TY - CONF TI - Speed Photo–Radar Enforcement and Its Effects on Speed in Work Zones AU - Benekohal, R.F. AU - Wang, M. AU - Chitturi, M.V. AU - Hajbabaie, A. AU - Medina, J.C. T2 - 88th Annual Meeting of the Transportation Research Board C2 - 2009/// C3 - The 88th Annual Meeting of the Transportation Research Board CY - Washington, DC DA - 2009/// PY - 2009/1/11/ ER - TY - CONF TI - Comparison of Effects of Automated Speed Enforcement and Police Presence on Speeding in Work Zones AU - Hajbabaie, A. AU - Benekohal, R.F. AU - Chitturi, M.V. AU - Wang, M. AU - Medina, J.C. T2 - 88th Annual Meeting of the Transportation Research Board C2 - 2009/// C3 - The 88th Annual Meeting of the Transportation Research Board CY - Washington, DC DA - 2009/// PY - 2009/1/11/ ER - TY - CONF TI - Downstream Effects of Speed Photo–Radar Enforcement and Other Speed Reduction Treatments on Work Zones AU - Medina, J.C. AU - Benekohal, R.F. AU - Hajbabaie, A. AU - Wang, M. AU - Chitturi, M.V. T2 - 88th Annual Meeting of the Transportation Research Board C2 - 2009/// C3 - The 88th Annual Meeting of the Transportation Research Board CY - Washington, DC DA - 2009/// PY - 2009/1/11/ ER - TY - CHAP TI - Sample Preparation Techniques for Filtration Testing of Fly Ash with Nonwoven Geotextiles AU - Gabr, MA AU - Akram, MH T2 - Sampling Environmental Media AB - A laboratory investigation was conducted to evaluate the applicability of five preparation techniques of fly ash/geotextile specimens for the gradient ratio (GR) test. These techniques included the current ASTM method, a modified ASTM method, a vibro-prep technique, a dry preparation, and slurry method. Using the ASTM method for preparation, measured specific discharge and GR across the fly ash-geotextile systems were 8.0 {times} 10{sup {minus}4} cm/sec and 1.25, respectively. However, during the placement of the fly ash in the permeameter some intrusion of the particles into the geotextile openings took place. A technique for placing fly ash in the permeameter was modified after ASTM D5101. Using this modified method, the specific discharge and GR were measured to be 6.8 {times} 10{sup {minus}4} cm/sec and 0.80, respectively. The specimens prepared using the slurry method exhibited a relatively stable behavior. The specific discharge had an average value of 2.5 {times} 10{sup {minus}4} cm/sec after 600 hours of testing. The GR decreased from 1.52 to 1.37 during this period. The extent of piping under different testing conditions was quantified in this investigation. The specimens prepared using dry method exhibited an unsteady behavior and piping was observed to be dominant. Although piping of fine particlesmore » through the geotextile system was less than the suggested limit of 0.25 g/cm{sup 2} for soils, it is proposed that in the case of fly ash specimens with geotextile, stable systems should be categorized as those with piping rate less than 0.03 g/cm{sup 2}.« less PY - 2009/3/4/ DO - 10.1520/stp16586s SP - 376-376-13 PB - ASTM International UR - http://dx.doi.org/10.1520/stp16586s ER - TY - JOUR TI - Transport and release of chemicals from plastics to the environment and to wildlife AU - Teuten, E.L. AU - Saquing, J.M. AU - Knappe, D.R.U. AU - Barlaz, M.A. AU - Jonsson, S. AU - Björn, A. AU - Rowland, S.J. AU - Thompson, R.C. AU - Galloway, T.S. AU - Yamashita, R. AU - Ochi, D. AU - Watanuki, Y. AU - Moore, C. AU - Viet, P.H. AU - Tana, T.S. AU - Prudente, M. AU - Boonyatumanond, R. AU - Zakaria, M.P. AU - Akkhavong, K. AU - Ogata, Y. AU - Hirai, H. AU - Iwasa, S. AU - Mizukawa, K. AU - Hagino, Y. AU - Imamura, A. AU - Saha, M. AU - Takada, H. T2 - Philosophical Transactions of the Royal Society B: Biological Sciences AB - Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2′-bis( p- chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g –1 to µg g –1 . Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub µg l –1 to mg l –1 and were correlated with the level of economic development. DA - 2009/// PY - 2009/// DO - 10.1098/rstb.2008.0284 VL - 364 IS - 1526 SP - 2027-2045 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-67650784197&partnerID=MN8TOARS ER - TY - CHAP TI - Black Carbon Mitigation AU - Baron, R. AU - Lomborg, B. AU - David Montgomery, W. AU - Tuladhar, S. AU - Kandlikar, M. AU - Reynolds, C. AU - Andrew, P. AU - Lomborg, B. AB - Much attention has been given to mitigation policies designed to limit the emissions of carbon dioxide (CO2) and other greenhouse gases (GHGs) that contribute to atmospheric warming. However, it is generally agreed that as much as 40% of current net warming (10–20% of gross warming) is attributable to black carbon (Jacobsen 2007: 3). Because of its large effect on radiative forcing and relatively short residence time in the atmosphere, black carbon presents some unique opportunities for postponing the effects of climate change. Whereas CO2 has a lifetime of up to about forty years, black carbon remains in the atmosphere for as little as several weeks. As such, reducing emissions of black carbon can have an immediate near-term impact on atmospheric warming. Furthermore, since black carbon is considered responsible for about 30% of the Arctic melting, black carbon emission reductions can rapidly reduce the rate at which Arctic ice is melting and avert associated consequences. Black carbon reduction policies can also result in large health benefits, especially to citizens of developing countries. PY - 2009/// DO - 10.1017/CBO9780511779015.005 PB - Cambridge University Press ER - TY - SOUND TI - Simultaneous Modeling Carbon and Nitrogen Removal under the Influence of Floc Size Distribution AU - Sobremisana, A. AU - de lose Reyes, F.L., III AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - Factors Affecting the Formation of FOG Deposits in Sewer Lines AU - de los Reyes, F. AU - Ducoste, J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - Validation of CFD Models Simulating the UV/H2O2 Advanced Oxidation Process AU - Alpert, S.M. AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - JOUR TI - Computational Fluid Dynamics as an Integral Part of Water and Wastewater Treatment Process Design AU - Ducoste, J.J. T2 - Influents: Water Environment Association of Ontario DA - 2009/// PY - 2009/// VL - 4 SP - 40–44 ER - TY - SOUND TI - Simulating Ultraviolet Advance Oxidation Processes in Continuous Flow UV Reactors AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - CFD Modeling for UV Disinfection and UV-Initiated Advanced Oxidation Processes AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - Analysis of Fat, Oil, and Grease (FOG) in Sanitary Sewer Systems: Challenges to a Sustainable system AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - BOOK TI - Advances in Population Balance Modeling A3 - Nopens, I. A3 - Ducoste, J.J. A3 - Briesen, H. DA - 2009/// PY - 2009/// VL - 64 ER - TY - SOUND TI - Computational Fluid Dynamics Modeling for Unit Process simulations in Drinking Water Treatment AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - Population Balance Modeling in CFD Simulations AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - The Intricacies of Analyzing/Designing Ultraviolet UV Disinfection Reactors using CFD AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - CONF TI - Estimating Carbon Sequestration and Gas Production in Solid Waste Using Waste Composition AU - Staley, B.F. AU - Barlaz, M.A. T2 - Association of Environmental Engineering and Science Professionals (AEESP) Frontiers Conference C2 - 2009/// CY - Iowa City, Iowa DA - 2009/// PY - 2009/7/26/ ER - TY - CONF TI - A Method to Estimate Carbon Sequestration from Excavated Refuse Samples AU - De La Cruz, F. AU - Barlaz, M.A. T2 - First International Greenhouse Gas Measurement Symposium, Air and Waste Management Association C2 - 2009/// CY - San Francisco, CA DA - 2009/// PY - 2009/3/22/ ER - TY - RPRT TI - Life-Cycle Inventory Model for Commercial and Industrial Food Waste Management AU - Reale-Levis, J.L. AU - Barlaz, M.A. AU - Ranjithan, S.R. A3 - Delaware Solid Waste Authority DA - 2009/// PY - 2009/// M3 - Final report PB - Delaware Solid Waste Authority ER - TY - RPRT TI - A Life-Cycle Analysis of Alternatives for the Management of Waste Hot Mix Asphalt AU - Reale-Levis, J.L. AU - Barlaz, M.A. AU - Ranjithan, S.R. A3 - Delaware Solid Waste Authority DA - 2009/// PY - 2009/// M3 - Final report PB - Delaware Solid Waste Authority ER - TY - RPRT TI - A Life-Cycle Analysis of Alternatives for the Management of Construction and Demolition Waste AU - Reale-Levis, J.L. AU - Barlaz, M.A. AU - Ranjithan, S.R. A3 - Delaware Solid Waste Authority DA - 2009/// PY - 2009/// M3 - Final report PB - Delaware Solid Waste Authority ER - TY - SOUND TI - Criteria to Terminate Post-Closure Monitoring at MSW landfills AU - Barlaz, M.A. DA - 2009/// PY - 2009/// ER - TY - CONF TI - A Landfill Carbon Balance: Gas Production and Control, and Carbon Sequestration AU - Barlaz, M.A. T2 - International Solid Waste Association (ISWA) Annual Meeting C2 - 2009/// CY - Copenhagen, Denmark DA - 2009/// PY - 2009/12/3/ ER - TY - SOUND TI - Solid Waste Management Research: from the Test Tube to the Field AU - Barlaz, M.A. DA - 2009/// PY - 2009/// M3 - invited lectures ER - TY - SOUND TI - Analysis of Field Grease Interceptors AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - SOUND TI - Assessment of Root Control Methods and Root Regrowth in a Pilot Scale Sanitary Sewer AU - Ducoste, J.J. DA - 2009/// PY - 2009/// ER - TY - JOUR TI - Flexural Design of Concrete Beams Reinforced with High Strength Steel Reinforcing Bars AU - Mast, R. AU - Dawood, M. AU - Rizkalla, S. AU - Zia, P. T2 - ACI Structural Journal DA - 2009/// PY - 2009/// VL - 106 IS - 4 SP - 551–552 ER - TY - JOUR TI - FRP Shear Transfer Mechanism for Precast, Prestressed Concrete Sandwich Load Bearing Panels AU - Rizkalla, S. AU - Hassan, T. AU - Lucier, G. T2 - ACI Special Publication DA - 2009/10// PY - 2009/10// VL - 265 SP - 603 – 626 ER - TY - CONF TI - A Multi-Objective Evolutionary Computation Approach to Hazards Mitigation Design for Water Distribution Systems AU - Kanta, Lufthansa AU - Brumbelow, Kelly AU - Zechman, Emily T2 - World Environmental and Water Resources Congress 2009 AB - One of the critical public safety roles for water distribution systems (WDS) is suppression of urban fire events. Previous studies have investigated WDS rehabilitation for mitigation of potential fire events with a major focus on improving fire flows by pipe enlargement. However, pipe enlargement can cause water quality problems and place public health at risk during normal operational periods. Thus a novel approach is required to effectively address the conflicting goals of the WDS: reliable delivery of water during normal as well as emergency conditions, meeting water quality standards, and finding cost-effective design and rehabilitation options. In this study an evolutionary computation-based multi-objective optimization-simulation framework is developed to design effective mitigation strategies for urban fire events for water distribution systems with three objectives: (1) minimizing fire damages, (2) minimizing water quality deficiencies, and (3) minimizing the cost of mitigation. An elitist non-dominated sorting genetic algorithm (NSGA-II) is modified by incorporating an evolution strategy (ES) to address difficulties for heuristic algorithms posed by WDS problems. Implementation of this methodology generates Pareto-optimal solution surfaces that express the trade-off relationship between fire damage, water quality, and least cost objectives. Thus, the method provides decision makers with the flexibility to choose a mitigation plan for urban fire events best suited for their circumstances. Each Pareto-optimal solution comprises a set of pipes to be enlarged to achieve increased fire flow and the corresponding diameters of these pipes. The algorithm is illustrated with several test functions. The Micropolis virtual city is then used to demonstrate the application of the proposed methodology to a complex WDS. C2 - 2009/5/12/ C3 - World Environmental and Water Resources Congress 2009 DA - 2009/5/12/ DO - 10.1061/41036(342)43 PB - American Society of Civil Engineers SN - 9780784410363 UR - http://dx.doi.org/10.1061/41036(342)43 DB - Crossref ER - TY - CONF TI - Improving Hydrologic Sustainability of Texas A&M University Campus AU - Khedun, Prakash AU - Damodaram, Chandana AU - Giacomoni, Marcio AU - Ryan, Andrea AU - Holmes, Hillary AU - Klein, Ross AU - Saour, William AU - Hollingsworth, Michelle AU - Berthold, Troy AU - Davis, Meg AU - Bullock, Philip AU - Ravikumar, Neetha AU - Zechman, Emily AU - Moore, Georgianne AU - Boulanger, Bryan AU - Stoleru, Radu T2 - World Environmental and Water Resources Congress 2009 AB - This research investigates the hydrologic sustainability of urban development and stormwater management for a watershed on the Texas A&M campus. The main Texas A&M campus has become increasingly urbanized, resulting in areas of imperviousness that generate higher rates of runoff. This growth has proceeded unchecked, and significant growth and development are planned for the future. Both increased rates of runoff from previous development and the impact of anticipated development should be addressed through mitigation efforts. This research provides a means to assess watershed health through biological indicators, water quality indicators, riparian ecosystems, the floodplain footprint, and the long term flow regime. A modeling framework is implemented to couple hydrologic and hydraulics models to simulate a set of watershed management plans that employ alternative best management practices. Development plans will be evaluated based on a set of comprehensive metrics that synthesize ecological, hydrologic, and environmental aspects of watershed health. The selection of management plans based on these metrics will enhance the environmental sustainability of further campus development. C2 - 2009/5/12/ C3 - World Environmental and Water Resources Congress 2009 DA - 2009/5/12/ DO - 10.1061/41036(342)122 PB - American Society of Civil Engineers SN - 9780784410363 UR - http://dx.doi.org/10.1061/41036(342)122 DB - Crossref ER - TY - CONF TI - Hydrologic Footprint Residence: A New Metric to Assess Hydrological Alterations Due to Urbanization AU - Giacomoni, M. H. AU - Zechman, E. M. T2 - World Environmental and Water Resources Congress 2009 AB - Urbanization modifies hydrological processes in a watershed as surface alterations, such as the use of impervious cover, increase runoff volumes and modify the temporal patterns of the hydrograph. Higher peak flows and increased flood duration often lead to erosion and degradation of ecosystems. Typically, the peak flow for a design storm is used to assess the impact of land use change on the hydrological cycle. This approach, however, does not capture the extent of hydrologic change and impact on downstream communities. Floodplains have an important function in controlling downstream floods and sustaining sensitive ecosystems. This research proposes a new metric to quantify the effects of development based on the change in floodplain areas. The Hydrologic Footprint Residence (HFR) is proposed to evaluate the modification of floodplain areas and duration of a flood's residence. HFR can be used to analyze hydrological changes, gauge riparian ecosystem health, and develop watershed management plans. The use of HFR is demonstrated for a case study located on the Texas A&M University campus to evaluate the hydrologic impact of watershed development. C2 - 2009/5/12/ C3 - World Environmental and Water Resources Congress 2009 DA - 2009/5/12/ DO - 10.1061/41036(342)119 PB - American Society of Civil Engineers SN - 9780784410363 UR - http://dx.doi.org/10.1061/41036(342)119 DB - Crossref ER - TY - JOUR TI - Semiconductor to metal transition characteristics of VO2 thin films grown epitaxially on Si (001) AU - Gupta, A. AU - Aggarwal, R. AU - Gupta, P. AU - Dutta, T. AU - Narayan, Roger J. AU - Narayan, J. T2 - Applied Physics Letters AB - We report semiconductor to metal transition (SMT) characteristics of vanadium dioxide (VO2) grown epitaxially on Si (001) at 500 °C. The epitaxial integration with Si (001) was achieved by using epitaxial tetragonal yttria-stabilized zirconia (YSZ) as an intermediate buffer layer, which was grown in situ. From x-ray (θ-2θ and ϕ-scan) and electron diffraction studies, we established that VO2 and YSZ grow in (020) and (001) orientations, respectively, on Si (001) substrate and epitaxial relationship was established to be “VO2[001] or VO2[100]”//YSZ[110]//Si [100] and VO2(010)//YSZ(001)//Si(001). VO2/YSZ/Si(001) heterostructures showed approximately three orders of magnitude reversible change in resistivity and hysteresis of ∼6 K upon traversing the transition temperature. A 10 °C increase in the SMT temperature of these VO2 films, compared to the value reported for bulk VO2, has been explained on the basis of uniaxial stress along the c-axis, which can stabilize the covalent monoclinic phase up to higher temperatures. A correlation between in-plane orientations of the film and the transition width has also been suggested, which is consistent with our previously published thermodynamic model. DA - 2009/9/14/ PY - 2009/9/14/ DO - 10.1063/1.3232241 VL - 95 IS - 11 SP - 111915 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3232241 DB - Crossref ER - TY - JOUR TI - The effect of temperature on the corrosion of steel in concrete. Part 2: Model verification and parametric study AU - Pour-Ghaz, M. AU - Burkan Isgor, O. AU - Ghods, P. T2 - Corrosion Science AB - A comprehensive model for predicting the corrosion rate of steel in concrete has been developed using the concept of simulated polarization resistance experiments. This model is developed by carrying out a nonlinear regression analysis on data obtained from numerical experiments that are based on the solution of Laplace’s equation in a domain determined by the polarized length of the rebar. This part of the paper provides a comprehensive verification of the developed model and illustrates the application of the model to investigate the coupled effects of parameters affecting corrosion of steel in concrete. The results of the verification study show that the model predictions are in good agreement with the experimental data. DA - 2009/2// PY - 2009/2// DO - 10.1016/j.corsci.2008.10.036 VL - 51 IS - 2 SP - 426-433 J2 - Corrosion Science LA - en OP - SN - 0010-938X UR - http://dx.doi.org/10.1016/j.corsci.2008.10.036 DB - Crossref KW - Steel reinforced concrete KW - Modelling studies KW - Polarization KW - Kinetic parameters ER - TY - JOUR TI - The Effects of Interdune Vegetation Changes on Eolian Dune Field Evolution: a numerical modeling case study at Jockey's Ridge, North Carolina, USA AU - Pelletier, J. AU - Mitasova, H. AU - Overton, M. AU - Harmon, R T2 - Earth Surface Processes and Landforms AB - Abstract Changes in vegetation cover within dune fields can play a major role in how dune fields evolve. To better understand the linkage between dune field evolution and interdune vegetation changes, we modified Werner's ( Geology , 23, 1995: 1107–1110) dune field evolution model to account for the stabilizing effects of vegetation. Model results indicate that changes in the density of interdune vegetation strongly influence subsequent trends in the height and area of eolian dunes. We applied the model to interpreting the recent evolution of Jockey's Ridge, North Carolina, where repeat LiDAR surveys and historical aerial photographs and maps provide an unusually detailed record of recent dune field evolution. In the absence of interdune vegetation, the model predicts that dunes at Jockey's Ridge evolve towards taller, more closely‐spaced, barchanoid dunes, with smaller dunes generally migrating faster than larger dunes. Conversely, the establishment of interdune vegetation causes dunes to evolve towards shorter, more widely‐spaced, parabolic forms. These results provide a basis for understanding the increase in dune height at Jockey's Ridge during the early part of the twentieth century, when interdune vegetation was sparse, followed by the decrease in dune height and establishment of parabolic forms from 1953‐present when interdune vegetation density increased. These results provide a conceptual model that may be applicable at other sites with increasing interdune vegetation cover, and they illustrate the power of using numerical modeling to model decadal variations in eolian dune field evolution. We also describe model results designed to test the relative efficacy of alternative strategies for mitigating dune migration and deflation. Installing sand‐trapping fences and/or promoting vegetation growth on the stoss sides of dunes are found to be the most effective strategies for limiting dune advance, but these strategies must be weighed against the desire of many park visitors to maintain the natural state of the dunes. Copyright © 2009 John Wiley & Sons, Ltd. DA - 2009/7// PY - 2009/7// DO - http://doi.org/10.1002/esp.1809 VL - 34 IS - 9 SP - 1245–1254 ER - TY - JOUR TI - Field investigation of Hurricane Ike impacts to the upper Texas coast AU - Ewing, L. AU - Stauble, D. AU - Work, P. AU - Edge, B. AU - Loeffler, M. AU - Kaihatu, J. AU - Overton, M. AU - Waters, J. AU - Suzuki, K AU - Dean, R. AU - Garrett, M. AU - Wiggins, E. AU - Gregory, G. T2 - Shore and Beach DA - 2009/// PY - 2009/// VL - 77 IS - 2 ER - TY - CONF TI - Climate-informed Uncertainty Analyses for Integrated River Basin Management AU - Arumugam, S. T2 - US-Korea Conference C2 - 2009/7/19/ CY - Raleigh, NC DA - 2009/7/19/ PY - 2009/7/19/ ER - TY - SOUND TI - Role of Climate Variability and Change in Improving River Basin Management AU - Arumugam, S. DA - 2009/12/23/ PY - 2009/12/23/ ER - TY - RPRT TI - Characterization of Biological Activity in Refuse Samples Excavated from the Waimanalo Gulch Sanitary Landfill AU - Sadri, A. AU - Staley, B.F. AU - Reyes, F. AU - Barlaz, M.A. A3 - Waste Management of Hawaii DA - 2009/// PY - 2009/// PB - Waste Management of Hawaii ER - TY - CHAP TI - The use of seasonal climate forecasts within a shared reservoir system: The case of Angat reservoir, the Philippines AU - Brown, C. AU - Conrad, E. AU - Sankarasubramanian, A. AU - Someshwar, S. AU - Elazegui, Dulze T2 - Climate Change Adaptation in the Water Sector A2 - Ludwig, F. A2 - Kabat, P. A2 - van Schaik, H. A2 - van der Valk, M. PY - 2009/// PB - Earthscan ER - TY - CHAP TI - VEPCD Modeling of Asphalt Concrete with Growing Damage AU - Kim, Y.R. AU - Underwood, B.S. AU - Chehab, G.R. AU - Daniel, J.S. AU - Lee, H.J. AU - Yun, T.Y. T2 - Modeling of Asphalt Concrete A2 - Kim, Y.R. PY - 2009/// SP - 163–203 PB - ASCE Press/McGraw Hill ER - TY - JOUR TI - Bond Behavior of Near-Surface Mounted FRP Strips Bonded to Modern Clay Brick Masonry Prisms: Influence of Strip Orientation and Compression Perpendicular to the Strip AU - Petersen, Robert B. AU - Masia, Mark J. AU - Seracino, Rudolf T2 - Journal of Composites for Construction AB - In this paper the results of 18 pull tests performed on clay brick masonry prisms strengthened with near-surface mounted carbon fiber-reinforced polymer (CFRP) strips are presented. The pull tests were designed to add to the existing database and investigate variables significant to masonry construction. FRP was bonded to solid clay brick masonry; FRP aligned both perpendicular and parallel to the bed joint; and in the case of FRP reinforcement aligned parallel to the bed joint, compression applied perpendicular to the strip was used to simulate vertical compression load in masonry walls. Results including bond strength, critical bond length, and the local bond-slip relationship are presented as well as a discussion on the effect of the new variables on these results. DA - 2009/6// PY - 2009/6// DO - 10.1061/(ASCE)CC.1943-5614.0000002 VL - 13 IS - 3 SP - 169-178 J2 - J. Compos. Constr. LA - en OP - SN - 1090-0268 1943-5614 UR - http://dx.doi.org/10.1061/(ASCE)1090-0268(2009)13:3(169) DB - Crossref ER - TY - CONF TI - Grain Size Distribution Effects in 2D Discrete Numerical Experiments AU - Evans, T. Matthew AU - Mojarrad, Hamed AU - Cunningham, Charles AU - Tayebali, Akhtar A. T2 - International Foundation Congress and Equipment Expo 2009 AB - The discrete element method (DEM) is becoming increasingly popular for the simulation and study of the mechanical response of granular materials. The narrow grain size distributions (GSD) used in most DEM studies are not necessarily representative of real soils, wherein grain sizes vary over several orders of magnitude. In the current study, biaxial compression tests on two-dimensional particulate assemblies are simulated and the results analyzed as a function of GSD. Four GSD's are simulated and material response is interpreted in terms of stress-strain-strength behavior at the macroscale and in terms of particle-level properties at the microscale. These types of studies may ultimately lead to a better fundamental understanding of the response of real soils with varying GSD's. Results of the simulations indicate that a coarser well-graded specimen has a higher shear strength than a finer well-graded specimen, consistent with a higher rate of dilation at peak for the coarser specimen. The more uniformly graded specimen is softer at low strains, requires a higher strain to peak, and is significantly more dilatant than the well-graded assemblies. C2 - 2009/3/10/ C3 - Contemporary Topics in In Situ Testing, Analysis, and Reliability of Foundations DA - 2009/3/10/ DO - 10.1061/41022(336)8 PB - American Society of Civil Engineers SN - 9780784410226 UR - http://dx.doi.org/10.1061/41022(336)8 DB - Crossref ER - TY - JOUR TI - Stringless Portland Cement Concrete Paving AU - Cable, James K. AU - Jaselskis, Edward J. AU - Walters, Russell C. AU - Li, Lifeng AU - Bauer, Chris R. T2 - Journal of Construction Engineering and Management AB - This paper describes results from a study evaluating stringless paving using a combination of global positioning and laser technologies. A concrete paver manufacturer and a machine guidance solution provider developed this technology and successfully implemented it on construction earthmoving and grading projects. Concrete paving is a new area for considering this technology. A concrete paving contractor in Iowa agreed to test the stringless paving technology on two challenging concrete paving projects located in Washington County, Iowa during the summer of 2003. The research team from Iowa State University monitored the guidance and elevation conformance to the original design. They employed a combination of physical depth checks, surface location and elevation surveys, concrete yield checks, and physical survey of the control stakes and string line elevations. A final check on profile of the pavement surface was accomplished by the use of the Iowa Department of Transportation Light Weight Surface Analyzer. Due to the speed of paving and the rapid changes in terrain, the laser technology was abandoned for this project. Total control of the guidance and elevation controls on the slip form paver were moved from string line to a global positioning system (GPS). Results indicate that GPS control is a feasible approach to controlling a concrete paver. Further enhancements are needed in the physical features of the slip form paver hydraulic system controls and in the computer program for controlling elevation. DA - 2009/11// PY - 2009/11// DO - 10.1061/(ASCE)CO.1943-7862.0000083 VL - 135 IS - 11 SP - 1253-1260 J2 - J. Constr. Eng. Manage. LA - en OP - SN - 0733-9364 1943-7862 UR - http://dx.doi.org/10.1061/(ASCE)CO.1943-7862.0000083 DB - Crossref ER - TY - JOUR TI - Large-scale laboratory experiment on erosion of sand beds by moving circular vertical jets AU - Yeh, Po-Hung AU - Chang, Kuang-An AU - Henriksen, John AU - Edge, Billy AU - Chang, Peter AU - Silver, Andrew AU - Vargas, Abel T2 - Ocean Engineering AB - This study investigates the topographic deformation due to the erosion of a sand bed impinged by a moving submerged turbulent round jet in a large-scale laboratory. The test conditions represent the case of discharges beneath a vessel while operating in water with a limited clearance such as a shallow navigation channel. The jet moves horizontally and discharges water vertically downward towards the bed. The distance between the jet nozzle and the bed equals six times the jet diameter so the jet flow is in the potential core region. The speed of the jet horizontal motion was varied to examine its effect on the scour profile. The characteristic lengths of the scour profile in the asymptotic state were determined by modifying the empirical formulas in Aderibigbe and Rajaratnam [1996. Erosion of loose beds by submerged circular impinging vertical turbulent jets. Journal of Hydraulic Research 34(1), 19–33]. The maximum scour depth, the scour hole radius, and the ridge height were found to be a function of the ratio of the jet exit to jet translation velocities and were modeled using a hyperbolic function. Empirical equations describing the scour profile were developed and the scour profile was found to be self-similar when normalized by appropriate length scales. DA - 2009/3// PY - 2009/3// DO - 10.1016/j.oceaneng.2008.11.006 VL - 36 IS - 3-4 SP - 248-255 J2 - Ocean Engineering LA - en OP - SN - 0029-8018 UR - http://dx.doi.org/10.1016/j.oceaneng.2008.11.006 DB - Crossref KW - Turbulence jet KW - Moving jet KW - Bed erosion KW - Scour KW - Laboratory measurement ER - TY - JOUR TI - Quantitative Interpretation of Half-Cell Potential Measurements in Concrete Structures AU - Pour-Ghaz, Mohammad AU - Isgor, O. Burkan AU - Ghods, Pouria T2 - Journal of Materials in Civil Engineering AB - The interpretation of half-cell potential measurements in reinforced concrete structures can be a major challenge for civil engineers. The main reason for this is that half-cell potential mapping provides information to predict the probability of corrosion in concrete, but it does not give clear insight on the rate and the nature of corrosion. Although for general uniform corrosion, half-cell data can provide valuable information about the probability of corrosion. In the case of localized corrosion, the predictions of half-cell measurements can be misleading. The main objective of the present work is to provide practicing engineers a tool that they can use to better interpret the results of half-cell potential measurements. This tool quantitatively relates the potential readings on the surface of the concrete to the rate of probable localized reinforcement corrosion through concrete resistivity, cover thickness, and temperature, allowing the engineers to gain supplementary information from half-cell tests. Experimental comparisons presented in this paper demonstrate the potential benefits of the proposed approach when typical half-cell measurements may not be able to predict the localized corrosion mechanism. DA - 2009/9// PY - 2009/9// DO - 10.1061/(asce)0899-1561(2009)21:9(467) VL - 21 IS - 9 SP - 467-475 J2 - J. Mater. Civ. Eng. LA - en OP - SN - 0899-1561 1943-5533 UR - http://dx.doi.org/10.1061/(asce)0899-1561(2009)21:9(467) DB - Crossref ER - TY - JOUR TI - The effect of temperature on the corrosion of steel in concrete. Part 1: Simulated polarization resistance tests and model development AU - Pour-Ghaz, M. AU - Isgor, O. Burkan AU - Ghods, P. T2 - Corrosion Science AB - The effect of temperature on the corrosion rate of steel corrosion in concrete is investigated through simulated polarization resistance experiments. The simulated experiments are based on the numerical solution of the Laplace’s equation with predefined boundary conditions of the problem and have been designed to establish independent correlations among corrosion rate, temperature, kinetic parameters, concrete resistivity and limiting current density for a wide range of possible anode/cathode (A/C) distributions on the reinforcement. The results, which successfully capture the resistance and diffusion control mechanisms of corrosion as well as the effect of temperature on the kinetic parameters and concrete/pore solution properties, have been used to develop a closed-form regression model for the prediction of the corrosion rate of steel in concrete. DA - 2009/2// PY - 2009/2// DO - 10.1016/j.corsci.2008.10.034 VL - 51 IS - 2 SP - 415-425 J2 - Corrosion Science LA - en OP - SN - 0010-938X UR - http://dx.doi.org/10.1016/j.corsci.2008.10.034 DB - Crossref KW - Steel reinforced concrete KW - Modelling studies KW - Polarization KW - Kinetic parameters ER - TY - JOUR TI - Climate Stabilization Wedges in Action: A Systems Approach to Energy Sustainability for Hawaii Island AU - Johnson, Jeremiah AU - Chertow, Marian T2 - Environmental Science & Technology AB - Pacala and Socolow developed a framework to stabilize global greenhouse gas levels for the next fifty years using wedges of constant size representing an increasing use of existing technologies and approaches for energy efficiency, carbon free generation, renewables, and carbon storage. The research presented here applies their approach to Hawaii Island, with modifications to support local scale analysis and employing a "bottom-up" methodology that allows for wedges of various sizes. A discretely bounded spatial unit offers a testing ground for a holistic approach to improving the energy sector with the identification of local options and limitations to the implementation of a comprehensive energy strategy. Nearly 80% of total primary energy demand across all sectors for Hawaii Island is currently met using petroleum-based fuels.The Sustainable Energy Plan scenario included here presents an internally consistent set of recommendations bounded by local constraints in areas such as transportation efficiency, centralized renewable generation (e.g., geothermal, wind), reduction in transmission losses, and improved building efficiency. This scenario shows thatthe demand for primary energy in 2030 could be reduced by 23% through efficiency measures while 46% could be met by renewable generation, resulting in only 31% of the projected demand being met by fossil fuels. In 2030, the annual releases of greenhouse gases would be 3.2 Mt CO2-eq/year under the Baseline scenario, while the Sustainable Energy Plan would reduce this to 1.2 Mt CO2-eq/year--an annual emissions rate 40% below 2006 levels and 10% below 1990 levels. The total for greenhouse gas emissions during the 24-year study period (2007 to 2030) is 59.9 Mt CO2-eq under the Baseline scenario and 32.5 Mt CO2-eq under the Sustainable Energy Plan scenario. Numerous combinations of efficiency and renewable energy options can be employed in a manner that stabilizes the greenhouse gas emissions of Hawaii Island. DA - 2009/4// PY - 2009/4// DO - 10.1021/es801700a VL - 43 IS - 7 SP - 2234-2240 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es801700a DB - Crossref ER - TY - JOUR TI - High Surface Area Stainless Steel Brushes as Cathodes in Microbial Electrolysis Cells AU - Call, Douglas F. AU - Merrill, Matthew D. AU - Logan, Bruce E. T2 - Environmental Science & Technology AB - Microbial electrolysis cells (MECs) are an efficient technology for generating hydrogen gas from organic matter, but alternatives to precious metals are needed for cathode catalysts. We show here that high surface area stainless steel brush cathodes produce hydrogen at rates and efficiencies similar to those achieved with platinum-catalyzed carbon cloth cathodes in single-chamber MECs. Using a stainless steel brush cathode with a specific surface area of 810 m2/m3, hydrogen was produced at a rate of 1.7 +/- 0.1 m3-H2/m3-d (current density of 188 +/- 10 A/m3) at an applied voltage of 0.6 V. The energy efficiency relative to the electrical energy input was 221 +/- 8%, and the overall energy efficiency was 78 +/- 5% based on both electrical energy and substrate utilization. These values compare well to previous results obtained using platinum on flat carbon cathodes in a similar system. Reducing the cathode surface area by 75% decreased performance from 91 +/- 3 A/m3 to 78 +/- 4 A/m3. A brush cathode with graphite instead of stainless steel and a specific surface area of 4600 m2/m3 generated substantially less current (1.7 +/- 0.0 A/m3), and a flat stainless steel cathode (25 m2/m3) produced 64 +/- 1 A/m3, demonstrating that both the stainless steel and the large surface area contributed to high current densities. Linear sweep voltammetry showed that the stainless steel brush cathodes both reduced the overpotential needed for hydrogen evolution and exhibited a decrease in overpotential over time as a result of activation. These results demonstrate for the first time that hydrogen production can be achieved at rates comparable to those with precious metal catalysts in MECs without the need for expensive cathodes. DA - 2009/3/15/ PY - 2009/3/15/ DO - 10.1021/es803074x VL - 43 IS - 6 SP - 2179-2183 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es803074x DB - Crossref ER - TY - JOUR TI - Direct Biological Conversion of Electrical Current into Methane by Electromethanogenesis AU - Cheng, Shaoan AU - Xing, Defeng AU - Call, Douglas F. AU - Logan, Bruce E. T2 - Environmental Science & Technology AB - New sustainable methods are needed to produce renewable energy carriers that can be stored and used for transportation, heating, or chemical production. Here we demonstrate that methane can directly be produced using a biocathode containing methanogens in electrochemical systems (abiotic anode) or microbial electrolysis cells (MECs; biotic anode) by a process called electromethanogenesis. At a set potential of less than -0.7 V (vs Ag/AgCl), carbon dioxide was reduced to methane using a two-chamber electrochemical reactor containing an abiotic anode, a biocathode, and no precious metal catalysts. At -1.0 V, the current capture efficiency was 96%. Electrochemical measurements made using linear sweep voltammetry showed that the biocathode substantially increased current densities compared to a plain carbon cathode where only small amounts of hydrogen gas could be produced. Both increased current densities and very small hydrogen production rates by a plain cathode therefore support a mechanism of methane production directly from current and not from hydrogen gas. The biocathode was dominated by a single Archaeon, Methanobacterium palustre. When a current was generated by an exoelectrogenic biofilm on the anode growing on acetate in a single-chamber MEC, methane was produced at an overall energy efficiency of 80% (electrical energy and substrate heat of combustion). These results show that electromethanogenesis can be used to convert electrical current produced from renewable energy sources (such as wind, solar, or biomass) into a biofuel (methane) as well as serving as a method for the capture of carbon dioxide. DA - 2009/5/15/ PY - 2009/5/15/ DO - 10.1021/es803531g VL - 43 IS - 10 SP - 3953-3958 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es803531g DB - Crossref ER - TY - JOUR TI - Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell AU - Call, D. F. AU - Wagner, R. C. AU - Logan, B. E. T2 - Applied and Environmental Microbiology AB - A hydrogen utilizing exoelectrogenic bacterium (Geobacter sulfurreducens) was compared to both a nonhydrogen oxidizer (Geobacter metallireducens) and a mixed consortium in order to compare the hydrogen production rates and hydrogen recoveries of pure and mixed cultures in microbial electrolysis cells (MECs). At an applied voltage of 0.7 V, both G. sulfurreducens and the mixed culture generated similar current densities (ca. 160 A/m3), resulting in hydrogen production rates of ca. 1.9 m(3) H2/m3/day, whereas G. metallireducens exhibited lower current densities and production rates of 110 +/- 7 A/m3 and 1.3 +/- 0.1 m3 H2/m3/day, respectively. Before methane was detected in the mixed-culture MEC, the mixed consortium achieved the highest overall energy recovery (relative to both electricity and substrate energy inputs) of 82% +/- 8% compared to G. sulfurreducens (77% +/- 2%) and G. metallireducens (78% +/- 5%), due to the higher coulombic efficiency of the mixed consortium. At an applied voltage of 0.4 V, methane production increased in the mixed-culture MEC and, as a result, the hydrogen recovery decreased and the overall energy recovery dropped to 38% +/- 16% compared to 80% +/- 5% for G. sulfurreducens and 76% +/- 0% for G. metallireducens. Internal hydrogen recycling was confirmed since the mixed culture generated a stable current density of 31 +/- 0 A/m3 when fed hydrogen gas, whereas G. sulfurreducens exhibited a steady decrease in current production. Community analysis suggested that G. sulfurreducens was predominant in the mixed-culture MEC (72% of clones) despite its relative absence in the mixed-culture inoculum obtained from a microbial fuel cell reactor (2% of clones). These results demonstrate that Geobacter species are capable of obtaining similar hydrogen production rates and energy recoveries as mixed cultures in an MEC and that high coulombic efficiencies in mixed culture MECs can be attributed in part to the recycling of hydrogen into current. DA - 2009/10/9/ PY - 2009/10/9/ DO - 10.1128/aem.01760-09 VL - 75 IS - 24 SP - 7579-7587 J2 - Applied and Environmental Microbiology LA - en OP - SN - 0099-2240 UR - http://dx.doi.org/10.1128/aem.01760-09 DB - Crossref ER - TY - JOUR TI - Evolution of Organic Aerosols in the Atmosphere AU - Jimenez, J. L. AU - Canagaratna, M. R. AU - Donahue, N. M. AU - Prevot, A. S. H. AU - Zhang, Q. AU - Kroll, J. H. AU - DeCarlo, P. F. AU - Allan, J. D. AU - Coe, H. AU - Ng, N. L. AU - Aiken, A. C. AU - Docherty, K. S. AU - Ulbrich, I. M. AU - Grieshop, A. P. AU - Robinson, A. L. AU - Duplissy, J. AU - Smith, J. D. AU - Wilson, K. R. AU - Lanz, V. A. AU - Hueglin, C. AU - Sun, Y. L. AU - Tian, J. AU - Laaksonen, A. AU - Raatikainen, T. AU - Rautiainen, J. AU - Vaattovaara, P. AU - Ehn, M. AU - Kulmala, M. AU - Tomlinson, J. M. AU - Collins, D. R. AU - Cubison, M. J. AU - Dunlea, J. AU - Huffman, J. A. AU - Onasch, T. B. AU - Alfarra, M. R. AU - Williams, P. I. AU - Bower, K. AU - Kondo, Y. AU - Schneider, J. AU - Drewnick, F. AU - Borrmann, S. AU - Weimer, S. AU - Demerjian, K. AU - Salcedo, D. AU - Cottrell, L. AU - Griffin, R. AU - Takami, A. AU - Miyoshi, T. AU - Hatakeyama, S. AU - Shimono, A. AU - Sun, J. Y AU - Zhang, Y. M. AU - Dzepina, K. AU - Kimmel, J. R. AU - Sueper, D. AU - Jayne, J. T. AU - Herndon, S. C. AU - Trimborn, A. M. AU - Williams, L. R. AU - Wood, E. C. AU - Middlebrook, A. M. AU - Kolb, C. E. AU - Baltensperger, U. AU - Worsnop, D. R. T2 - Science AB - Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models. DA - 2009/12/10/ PY - 2009/12/10/ DO - 10.1126/science.1180353 VL - 326 IS - 5959 SP - 1525-1529 J2 - Science LA - en OP - SN - 0036-8075 1095-9203 UR - http://dx.doi.org/10.1126/science.1180353 DB - Crossref ER - TY - JOUR TI - A black-carbon mitigation wedge AU - Grieshop, Andrew P. AU - Reynolds, Conor C. O. AU - Kandlikar, Milind AU - Dowlatabadi, Hadi T2 - Nature Geoscience DA - 2009/8// PY - 2009/8// DO - 10.1038/ngeo595 VL - 2 IS - 8 SP - 533-534 J2 - Nature Geosci LA - en OP - SN - 1752-0894 1752-0908 UR - http://dx.doi.org/10.1038/ngeo595 DB - Crossref ER - TY - JOUR TI - Constraining the Volatility Distribution and Gas-Particle Partitioning of Combustion Aerosols Using Isothermal Dilution and Thermodenuder Measurements AU - Grieshop, Andrew P. AU - Miracolo, Marissa A. AU - Donahue, Neil M. AU - Robinson, Allen L. T2 - Environmental Science & Technology AB - The gas-particle partitioning of primary organic aerosol (POA) emissions from a diesel engine and the combustion of hard- and soft-woods in a stove was investigated by isothermally diluting them in a smog chamber or by passing them through a thermodenuder and measuring the extent of evaporation. The experiments were conducted at atmospherically relevant conditions: low concentrations and small temperature perturbations. The partitioning of the POA emissions from both sources varied continuously with changing concentration and temperature. Although the POA emissions are semivolatile, they do not completely evaporate at typical atmospheric conditions. The overall partitioning characteristics of diesel and wood smoke POA are similar, with wood smoke being somewhat less volatile than the diesel exhaust. The gas-particle partitioning of aerosols formed from flash-vaporized engine lubricating oil was also studied; diesel POA is somewhat more volatile than the oil aerosol. The experimental data from the dilution- and thermodenuder-based techniques were fit using absorptive partitioning theory to derive a volatility distribution of the POA emissions from each source. These distributions are suitable for use in chemical transport models that simulate POA concentrations. DA - 2009/7// PY - 2009/7// DO - 10.1021/es8032378 VL - 43 IS - 13 SP - 4750-4756 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es8032378 DB - Crossref ER - TY - JOUR TI - Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 1: measurement and simulation of organic aerosol evolution AU - Grieshop, A. P. AU - Logue, J. M. AU - Donahue, N. M. AU - Robinson, A. L. T2 - Atmospheric Chemistry and Physics AB - Abstract. Experiments were conducted to investigate the effects of photo-oxidation on organic aerosol (OA) emissions from flaming and smoldering hard- and soft-wood fires under plume-like conditions. This was done by exposing the dilute emissions from a small wood stove to UV light in a smog chamber and measuring the gas- and particle-phase pollutant concentrations with a suite of instruments including a Proton Transfer Reaction Mass Spectrometer (PTR-MS), an Aerosol Mass Spectrometer (AMS) and a thermodenuder. The measurements highlight how atmospheric processing can lead to considerable evolution of the mass and volatility of biomass-burning OA. Photochemical oxidation produced substantial new OA, increasing concentrations by a factor of 1.5 to 2.8 after several hours of exposure to typical summertime hydroxyl radical (OH) concentrations. Less than 20% of this new OA could be explained using a state-of-the-art secondary organic aerosol model and the measured decay of traditional SOA precursors. The thermodenuder data indicate that the primary OA is semivolatile; at 50°C between 50 and 80% of the fresh primary OA evaporated. Aging reduced the volatility of the OA; at 50°C only 20 to 40% of aged OA evaporated. The predictions of a volatility basis-set model that explicitly tracks the partitioning and aging of low-volatility organics was compared to the chamber data. The OA production can be explained by the oxidation of low-volatility organic vapors; the model can also reproduce observed changes in OA volatility and composition. The model was used to investigate the competition between photochemical processing and dilution on OA concentrations in plumes. DA - 2009/2/18/ PY - 2009/2/18/ DO - 10.5194/acp-9-1263-2009 VL - 9 IS - 4 SP - 1263-1277 J2 - Atmos. Chem. Phys. LA - en OP - SN - 1680-7324 UR - http://dx.doi.org/10.5194/acp-9-1263-2009 DB - Crossref ER - TY - JOUR TI - Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 2: analysis of aerosol mass spectrometer data AU - Grieshop, A. P. AU - Donahue, N. M. AU - Robinson, A. L. T2 - Atmospheric Chemistry and Physics AB - Abstract. Experiments were conducted to investigate the effects of photo-oxidation on organic aerosol (OA) in dilute wood smoke by exposing emissions from soft- and hard-wood fires to UV light in a smog chamber. This paper focuses on changes in OA composition measured using a unit-mass-resolution quadrupole Aerosol Mass Spectrometer (AMS). The results highlight how photochemical processing can lead to considerable evolution of the mass, volatility and level of oxygenation of biomass-burning OA. Photochemical oxidation produced substantial new OA, more than doubling the OA mass after a few hours of aging under typical summertime conditions. Aging also decreased the volatility of the OA and made it progressively more oxygenated. The results also illustrate strengths of, and challenges with, using AMS data for source apportionment analysis. For example, the mass spectra of fresh and aged BBOA are distinct from fresh motor-vehicle emissions. The mass spectra of the secondary OA produced from aging wood smoke are very similar to those of the oxygenated OA (OOA) that dominates ambient AMS datasets, further reinforcing the connection between OOA and OA formed from photo-chemistry. In addition, aged wood smoke spectra are similar to those from OA created by photo-oxidizing dilute diesel exhaust. This demonstrates that the OOA observed in the atmosphere can be produced by photochemical aging of dilute emissions from different types of combustion systems operating on fuels with modern or fossil carbon. Since OOA is frequently the dominant component of ambient OA, the similarity of spectra of aged emissions from different sources represents an important challenge for AMS-based source apportionment studies. DA - 2009/3/27/ PY - 2009/3/27/ DO - 10.5194/acp-9-2227-2009 VL - 9 IS - 6 SP - 2227-2240 J2 - Atmos. Chem. Phys. LA - en OP - SN - 1680-7324 UR - http://dx.doi.org/10.5194/acp-9-2227-2009 DB - Crossref ER - TY - BOOK TI - Downstream effects of speed photo-radar enforcement and other speed reduction treatments on work zones AU - Medina, J.C. AU - Benekohal, R.F. AU - Hajbabaie, A. AU - Wang, M.-H. AU - Chitturi, M.V. AB - The effects of automated speed photo–radar enforcement (SPE) and traditional speed reduction treatments (speed feedback trailer, presence of police vehicles with emergency lights on and off, and combinations of the speed feedback trailer and police presence) on speed were studied at a location 1.5 mi downstream of the actual treatment (spatial effects). Three data sets from two Interstate highway work zones were used. Field data consistently showed significant spatial (downstream) effects for SPE. The combination of speed feedback trailer and police vehicle with emergency lights off had downstream effects in some cases but to a lesser degree than SPE. Other treatments showed no significant downstream effects. For free-flowing traffic, SPE reduced the average downstream speed by 2 to 3.8 mph for cars and by 0.8 to 5.3 mph for trucks. Also, SPE reduced speeding cars by 7.1% to 23.4% (except for cars in median in Data Set 1), and speeding trucks by 4.2% to 48.3% (except for trucks in shoulder in Data Set 3). For the general traffic stream, SPE reduced the average downstream speed by 1.1 to 2.9 mph on cars and by 0.9 to 3.3 mph on trucks. When SPE was used, the percentage of speeding cars and trucks in the general traffic stream was reduced by 2.9% to 28.6%, and by 7.5% to 36.1%, respectively. SPE also reduced the percentage of cars in the general traffic stream exceeding the speed limit by more than 10 mph in virtually all cases, and eliminated such trucks in all but one case. DA - 2009/// PY - 2009/// DO - 10.3141/2107-03 SE - 24-33 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76249112826&partnerID=MN8TOARS ER - TY - BOOK TI - Speed photo-radar enforcement and Its effects on speed in work zones AU - Benekohal, R.F. AU - Wang, M.-H. AU - Chitturi, M.V. AU - Hajbabaie, A. AU - Medina, J.C. AB - Automated speed photo–radar enforcement (SPE) in work zones was implemented for the first time in the United States in Illinois. This paper presents the results of the effectiveness of SPE on the basis of three data sets collected in two work zones. SPE was effective in reducing the average speed and increasing compliance with the work zone speed limit in all three data sets. In almost all cases in which SPE was implemented, the average speeds were significantly lower than the work zone speed limit. The average free-flowing speed of cars was reduced by 4.2 to 7.9 mph, and that of trucks by 3.4 to 6.9 mph. SPE reduced the percentage of cars and heavy vehicles exceeding the speed limit significantly. The percentages of free-flowing cars exceeding the speed limit were reduced from 39.8% to 8.3% in Data Set 1, from 30.4% to 4.2% in Data Set 2, and from 93.2% to 45.5% in Data Set 3. The percentages of free-flowing heavy vehicles exceeding the speed limit were reduced from 17.3% to 4.2% in Data Set 1; from 6.1% to 1.2% in Data Set 2; and from 69.2% to 13.9% in Data Set 3. Trucks did not exceed the speed limit by more than 10 mph in any of the data sets when SPE was implemented. In two data sets no cars exceeded the speed limit by more than 10 mph, while in the third data set only 2.5% did. Field data were also collected after the SPE van left the work zone to examine the halo (temporal) effects of SPE. SPE had a halo effect of 1.8∼2.7 mph on free-flowing trucks in one work zone but none in the other work zone. The halo effect of SPE on free-flowing cars was a limited 1.2 mph on the shoulder lane in only one data set. DA - 2009/// PY - 2009/// DO - 10.3141/2096-12 SE - 89-97 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76649143367&partnerID=MN8TOARS ER - TY - CONF TI - Evolution strategies compared to genetic algorithms in finding optimal signal timing for oversaturated transportation network AU - Hajbabaie, A. AU - Benekohal, R.F. C2 - 2009/// C3 - IJCCI 2009 - International Joint Conference on Computational Intelligence, Proceedings DA - 2009/// SP - 298-301 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955445784&partnerID=MN8TOARS ER - TY - CONF TI - Characterizing Reactive Contaminant Sources in a Water Distribution System AU - Kumar, Jitendra AU - Brill, E. Downey AU - Mahinthakumar, G AU - Ranjithan, Ranji T2 - World Environmental and Water Resources Congress 2009 AB - Accurate knowledge of the characteristics of the contamination source during a contamination event is necessary for development of any mitigation and control strategy. Contaminant injected in a system is most likely to be reactive with chlorine; however, it is impractical for water quality monitoring systems to be able to monitor for the presence of all possible contaminants. In any distribution system, chlorine levels and other water quality parameters (pH, conductance, etc.) are routinely monitored to maintain the prescribed disinfection capacity. Any reactive contaminant would affect the chlorine levels resulting in deviations in the expected chlorine levels from those expected under normal operating conditions. Anomalies in the chlorine concentration from that of the expected value can be used as a surrogate to characterize the contaminant source in the system. In the absence of knowing the reactive characteristics of the contaminants, the location of injection, and injection pattern, source identification becomes a difficult problem to solve. Source identification can be posed as an inverse problem. In earlier work authors investigated the effect of the order of reaction kinetics of the contaminant with chlorine and its impact on source identification problem assuming the reaction kinetics to be known. That work is extended to investigate a methodology to address the source identification problem based on chlorine measurements, and the effects of different uncertain contamination conditions. Findings from a range of scenarios will be presented and discussed. C2 - 2009/5/12/ C3 - World Environmental and Water Resources Congress 2009 DA - 2009/5/12/ DO - 10.1061/41036(342)65 PB - American Society of Civil Engineers SN - 9780784410363 UR - http://dx.doi.org/10.1061/41036(342)65 DB - Crossref ER - TY - CONF TI - A Hybrid Heuristic Search Approach for Contaminant Source Characterization AU - Liu, Li AU - Brill, E. Downey AU - Mahinthakumar, G. (Kumar) AU - Ranjithan, S. Ranji T2 - World Environmental and Water Resources Congress 2009 AB - The rapid discovery of the contaminant source and its mass loading characteristics in a water distribution system (WDS) is vital for generating an efficient control strategy during a contamination event. Previous work on the Adaptive Dynamic Optimization Technique (ADOPT), which was developed as an Evolution Strategy (ES) based procedure, presents an approach to estimate the source characteristics adaptively, given dynamically updated observation data. Although this simulation-optimization approach is promising, it is computationally expensive, which poses challenges in the context of real-time solutions. This paper reports the findings of an investigation that builds upon the prior work by introducing a hybrid heuristic search method for the real-time characterization of a contaminant source. This new method integrates the ES-based ADOPT with a logistic regression (LR) analysis and a local improvement method to expedite the convergence and possibly solve the problem quickly. As a prescreening technique, a LR analysis step is performed prior to ADOPT; this step reduces the search space by eliminating unnecessary source nodes as potential source locations. Then, a local search (LS) approach is embedded into some of the algorithmic steps in ADOPT to serve as a postscreening step that potentially speeds up the convergence in localized regions in the solution space. Numerical experiments for the proposed hybrid approach are performed on an example water distribution network, and the results are compared with those of the standard implementation of ADOPT. C2 - 2009/5/12/ C3 - World Environmental and Water Resources Congress 2009 DA - 2009/5/12/ DO - 10.1061/41036(342)63 PB - American Society of Civil Engineers SN - 9780784410363 UR - http://dx.doi.org/10.1061/41036(342)63 DB - Crossref ER - TY - CONF TI - A CFD modeling protocol for simulating the UV/H2O2 advanced oxidation process AU - Alpert, S.M. AU - Ducoste, J.J. C2 - 2009/// C3 - Water Quality Technology Conference and Exposition 2009 DA - 2009/// SP - 1795-1816 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84873492275&partnerID=MN8TOARS ER - TY - JOUR TI - Speed Photo--Radar Enforcement and Its Effects on Speed in Work Zones AU - Benekohal, Rahim F AU - Wang, Ming-Heng AU - Chitturi, Madhav V AU - Hajbabaie, Ali AU - Medina, Juan C T2 - Transportation research record DA - 2009/// PY - 2009/// VL - 2096 IS - 1 SP - 89-97 ER - TY - JOUR TI - Downstream Effects of Speed Photo--Radar Enforcement and Other Speed Reduction Treatments on Work Zones AU - Medina, Juan C AU - Benekohal, Rahim F AU - Hajbabaie, Ali AU - Wang, Ming-Heng AU - Chitturi, Madhav V T2 - Transportation Research Record DA - 2009/// PY - 2009/// VL - 2107 IS - 1 SP - 24-33 ER - TY - JOUR TI - Modeling of in-vehicle PM2.5 exposure using the stochastic human exposure and dose simulation model AU - Liu, X. AU - Frey, H.C. AU - Cao, Y. AU - Deshpande, B. T2 - Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA DA - 2009/// PY - 2009/// VL - 2 SP - 1087-1100 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952286694&partnerID=MN8TOARS ER - TY - JOUR TI - Measurement of the energy use and emissions of passenger rail locomotives using a portable emission measurement system AU - Frey, H.C. AU - Choi, H.-W. AU - Kim, K. T2 - Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA DA - 2009/// PY - 2009/// VL - 2 SP - 1145-1157 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952268050&partnerID=MN8TOARS ER - TY - JOUR TI - Life Cycle Inventory Energy Consumption and Emissions for Biodiesel versus Petroleum Diesel Fueled Construction Vehicles AU - Pang, Shih-Hao AU - Frey, H. Christopher AU - Rasdorf, William J. T2 - Environmental Science & Technology AB - Substitution of soy-based biodiesel fuels for petroleum diesel will alter life cycle emissions for construction vehicles. A life cycle inventory was used to estimate fuel cycle energy consumption and emissions of selected pollutants and greenhouse gases. Real-world measurements using a portable emission measurement system (PEMS) were made for five backhoes, four front-end loaders, and six motor graders on both fuels from which fuel consumption and tailpipe emission factors of CO, HC, NOx, and PM were estimated. Life cycle fossil energy reductions are estimated at 9% for B20 and 42% for B100 versus petroleum diesel based on the current national energy mix. Fuel cycle emissions will contribute a larger share of total life cycle emissions as new engines enter the in-use fleet. The average differences in life cycle emissions for B20 versus diesel are: 3.5% higher for NOx; 11.8% lower for PM, 1.6% higher for HC, and 4.1% lower for CO. Local urban tailpipe emissions are estimated to be 24% lower for HC, 20% lower for CO, 17% lower for PM, and 0.9% lower for NOx. Thus, there are environmental trade-offs such as for rural vs urban areas. The key sources of uncertainty in the B20 LCI are vehicle emission factors. DA - 2009/8/15/ PY - 2009/8/15/ DO - 10.1021/es802916u VL - 43 IS - 16 SP - 6398-6405 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es802916u DB - Crossref ER - TY - JOUR TI - In-use measurement of the activity, energy use, and emissions of a plug-in hybrid electric vehicle AU - Frey, H.C. AU - Choi, H.-W. AU - Pritchard, E. AU - Lawrence, J. T2 - Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA DA - 2009/// PY - 2009/// VL - 2 SP - 1127-1144 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952244297&partnerID=MN8TOARS ER - TY - CONF TI - Estimation of air carrier emissions at Raleigh-Durham international airport AU - Graver, B.M. AU - Frey, H.C. C2 - 2009/// C3 - Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA DA - 2009/// VL - 4 SP - 2502-2516 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952383333&partnerID=MN8TOARS ER - TY - JOUR TI - A risk-based assessment and management framework for multipollutant air quality AU - Frey, H.C. AU - Hubbell, B. T2 - Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA DA - 2009/// PY - 2009/// VL - 2 SP - 1068-1080 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952278636&partnerID=MN8TOARS ER - TY - JOUR TI - Multiple approaches to assess filamentous bacterial growth in activated sludge under different carbon source conditions. AU - Gulez, G. AU - Los Reyes, F. L. T2 - J Appl Microbiol DA - 2009/// PY - 2009/// DO - JAM4049 [pii] 10.1111/j.1365-2672.2008.04049.x VL - 106 IS - 2 SP - 682-91 KW - activated sludge KW - carbon source KW - DGGE KW - filamentous bulking KW - FISH ER - TY - CHAP TI - Chapter 7. VEPCD Modeling of Asphalt Concrete with Growing Damage AU - Kim, Y.R. AU - Underwood, B.S. AU - Chehab, G.R. AU - Daniel, J.S. AU - Lee, H.J. AU - Yun, Y.R. T2 - Modeling of Asphalt Concrete PY - 2009/// PB - New York :McGraw-Hill ER - TY - JOUR TI - The application of artificial neural networks for estimating the dynamic modulus of asphalt concrete AU - Sakhaei Far, M.S. AU - Underwood, B.S. AU - Ranjithan, S.R. AU - Krim, Y.R. AU - Jackson, N. T2 - Transportation Research Record DA - 2009/// PY - 2009/// SP - 173-186 ER - TY - CONF TI - Simplified fatigue performance modeling of ALF pavements using VECD+3-D finite element modeling AU - Underwood, B.S. AU - Kim, Y.R. AU - Savadatti, S. AU - Thirunavukkarasu, S. AU - Guddati, M.N. C2 - 2009/// C3 - 7th International RILEM Symposium on Advanced Testing and Characterization of Bituminous Materials DA - 2009/// ER - TY - JOUR TI - Response and fatigue performance modeling of ALF pavements using 3-D finite element analysis and a simplified viscoelastic continuum damage model AU - Underwood. B.S., Krim AU - Y.R., Savadatti AU - S. Thirunavukkarasu, S. AU - M.N., Guddati T2 - Journal of the Association of Asphalt Paving Technologists DA - 2009/// PY - 2009/// SP - 829-868 ER - TY - CONF TI - Asphalt pavement response and fatigue performance prediction with viscoelastic continuum damage modeling approach AU - Underwood, B.S. AU - Kim, Y.R. C2 - 2009/// C3 - 2009 Pavement Prediction Symposium: Validation of Predictive Models Using Full-Scale and Field Pavement Performance DA - 2009/// ER - TY - CONF TI - Application of simplified VECD modeling to the fatigue prediction of asphalt concrete mixtures AU - Underwood, B.S. AU - Hou, E.T. AU - Kim, Y.R. C2 - 2009/// C3 - 7th International RILEM Symposium on Advanced Testing and Characterization of Bituminous Materials DA - 2009/// ER - TY - CONF TI - Analytical techniques for determining the endurance limit of hot mix asphalt concrete AU - Underwood, B.S. AU - Kim, Y.R. C2 - 2009/// C3 - 2nd International Conference on Perpetual Pavements DA - 2009/// ER - TY - JOUR TI - Comment on "Elastic modulus and hardness of muscovite and rectorite determined by nanoindentation" by G. Zhang, Z. Wei and RE Ferrell [Applied Clay Science 43 (2009) 271-281] AU - Bobko, Christopher P. AU - Ortega, J. Alberto AU - Ulm, Franz-Josef T2 - APPLIED CLAY SCIENCE AB - In their paper, Zhang et al. (2009) report on a series of nanoindentation experiments on muscovite and rectorite, two clay minerals with very different interlayer structures. Their work raises a fundamental question regarding the mechanical definition of a single clay mineral. Furthermore, if such a definition is possible, is nanoindentation capable of assessing the mechanical behavior of a single clay mineral? Comparison of Zhang et al.'s results with previously published nanoindentation results on shale, and with results of other methods of assessing the mechanical behavior of single clay minerals, provides an avenue to address these questions. In a final analysis, it may be impossible to strictly define the mechanical behavior of a single clay mineral without the additional context of specific applications. DA - 2009/12// PY - 2009/12// DO - 10.1016/j.clay.2009.08.008 VL - 46 IS - 4 SP - 425-428 SN - 1872-9053 KW - Elastic modulus KW - Hardness KW - Nanoindentation KW - Muscovite KW - Rectorite ER - TY - JOUR TI - A Control Sign Facility Design to Meet the New FHWA Minimum Sign Retroreflectivity Standards AU - Harris, Elizabeth A. AU - Rasdorf, William AU - Hummer, Joseph E. T2 - PUBLIC WORKS MANAGEMENT & POLICY AB - Minimum sign retroreflectivity standards issued by the Federal Highway Administration (FHWA) on January 29, 2008, have focused the attention of administrators and sign managers on improving the nighttime performance of traffic signs. To predict when a sign will need replacement, an agency will need to know when the retroreflectivity of signs with similar characteristics deteriorate to the minimum level established by the FHWA. Currently in the literature, there is limited information about the long-term deterioration behavior of ASTM Type III and IX signs. One way of achieving a better understanding of long-term sign deterioration is to establish an experimental sign retroreflectivity measurement facility (ESRMF). An ESRMF is an arrangement of signs in a controlled area that have their retroreflectivity measured at regular intervals to determine how it deteriorates as a function of time. This article shows how such a facility should look and why. A template is presented that can be used by agencies nationwide for collecting critical sign data to inform policy decisions. DA - 2009/10// PY - 2009/10// DO - 10.1177/1087724x09350226 VL - 14 IS - 2 SP - 174-194 SN - 1552-7549 KW - traffic signs KW - retroreflectivity KW - sign management KW - sign deterioration KW - sign testing KW - asset management ER - TY - JOUR TI - The Impact of Directionality on Paint Pavement Marking Retroreflectivity AU - Rasdorf, William J. AU - Zhang, Guanghua AU - Hummer, Joseph E. T2 - PUBLIC WORKS MANAGEMENT & POLICY AB - This article addresses paint centerline pavement marking retroreflectivity. The authors collect yellow centerline retroreflectivity data on two-lane highways, taking measurements in two directions. A paired t test on the data shows that there are differences and they are statistically significant. A field study is initiated to investigate the relationship between the direction the marking is painted and the retroreflectivity direction. The key result of this study is that paint centerline retroreflectivity values measured in the direction of paint striping are significantly higher than values measured in the opposite direction. Findings indicate that it is the lower retroreflectivity values of yellow centerlines (measured in the opposite direction from paint striping) that should be used to compare with the newly proposed Federal Highway Administration minimum standard because the drivers in that direction experience lower marking retroreflectivity at night. The implications for safety, for policy making, and for transportation asset management are significant. DA - 2009/1// PY - 2009/1// DO - 10.1177/1087724x08330824 VL - 13 IS - 3 SP - 265-277 SN - 1552-7549 KW - pavement marking KW - retroreflectivity KW - directionality KW - infrastructure management KW - asset management ER - TY - CONF TI - GIS and LiDAR use for identification of potential road hazard locations AU - Pradhan, A. AU - Rasdorf, W. A2 - Carlos H. Caldas, William J. O'Brien AB - In Northerly climates snowstorms are common occurrences that pose severe hazards to drivers. Thousands of lives and property worth of millions of dollars are lost annually. This paper presents a novel method of identifying road segments that pose special hazards to drivers during and after snowstorms by using Light Detection and Ranging (LiDAR) data and a Geographic Information System (GIS). The methodology presented herein can be used for prioritizing roadway snow clearing efforts by identifying the most hazardous road segments. The proposed methodology uses the spatial analysis functionality provided by GIS software and three-dimensional (3D) data obtained from an airborne LiDAR scanning system. The computing focus of this paper is on spatial data analysis. The data include road centerline 3D coordinates (to identify roadway crests and troughs), aspect data (to determine ground surface slope), and sunlight data (to determine ground surface illumination values and identify shaded areas). Combining and analyzing these data sets identify potentially dangerous north facing, shaded, steep slopes over large geographic areas. C2 - 2009/// C3 - Computing in civil engineering : proceedings of the 2009 ASCE International Workshop on Computing in Civil Engineering : June 24-27, 2009, Austin, Texas DA - 2009/// DO - 10.1061/41052(346)13 PB - Reston, Va. : American Society of Civil Engineers SN - 9780784410523 ER - TY - JOUR TI - Development and Use of Emissions Inventories for Construction Vehicles AU - Lewis, Phil AU - Frey, H. Christopher AU - Rasdorf, William T2 - TRANSPORTATION RESEARCH RECORD AB - Real-world data are insufficient to estimate actual emissions from construction vehicles and to develop effective decisions aimed at reducing emissions. A methodology is developed here for inventorying construction fleet emissions on the basis of representative real-world measurements of construction vehicles by means of a portable emissions measurement system (PEMS). The PEMS enables measurements of actual duty cycles and their corresponding fuel use and emissions. The methodology is demonstrated via application to a fleet of publicly owned construction vehicles used primarily for highway maintenance. Selected backhoes, front-end loaders, and motor graders, representing various model years and engine emissions standards, were measured with PEMS during use. Tests were performed for B20 biodiesel and petroleum diesel (PD) fuels. Emission factors from the PEMS data, combined with owner records of annual fuel consumption for over 1,000 vehicles, were used to estimate annual inventories of tailpipe emissions of nitrogen oxides, particulate matter, hydrocarbons, and carbon monoxide. The emissions inventory was stratified by pollutant, vehicle type, fuel type, and engine tier and was used to assess fleet management strategies aimed at reducing emissions. Case study results illustrate that total fleet emissions would be reduced by 3% to 24% when B20 fuel was being used exclusively instead of PD exclusively, 11% to 50% when all Tier 0 and Tier 1 engines were replaced with Tier 2 engines, and 31% to 72% when B20 fuel was used exclusively in the highest engine tier available. Recommendations are made about development and practical applications of emissions inventories for construction fleet management. DA - 2009/// PY - 2009/// DO - 10.3141/2123-06 IS - 2123 SP - 46-53 SN - 2169-4052 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76149135725&partnerID=MN8TOARS ER - TY - JOUR TI - Application of Artificial Neural Networks for Estimating Dynamic Modulus of Asphalt Concrete AU - Far, Maryam Sadat Sakhaei AU - Underwood, B. Shane AU - Ranjithan, S. Ranji AU - Kim, Y. Richard AU - Jackson, Newton T2 - Transportation Research Record: Journal of the Transportation Research Board AB - This paper presents outcomes from a research effort to develop models for estimating the dynamic modulus (| E * |) of hot-mix asphalt (HMA) layers on long-term pavement performance test sections. The goal of the work is the development of a new, rational, and effective set of dynamic modulus | E * | predictive models for HMA mixtures. These predictive models use artificial neural networks (ANNs) trained with the same set of parameters used in other popular predictive equations: the modified Witczak and Hirsch models. The main advantage of using ANNs for predicting | E * | is that an ANN can be created for different sets of variables without knowing the form of the predictive relationship a priori. The primary disadvantage of ANNs is the difficulty in predicting responses when the inputs are outside of the training database (i.e., extrapolation). To overcome this shortcoming, a large data set that covers the complete range of potential input conditions is needed. For this study, modulus values from multiple mixtures and binders were required and were assembled from existing national efforts and from data obtained at North Carolina State University. The data consisted of measured moduli from both modified and unmodified mixtures from numerous geographical locations across the United States. Prediction models were developed by using a portion of the data from these databases and then verified by using the remaining data in the databases. When these new ANN models are used, the results show that the predicted and measured | E * | values are in close agreement. DA - 2009/1// PY - 2009/1// DO - 10.3141/2127-20 VL - 2127 IS - 1 SP - 173-186 J2 - Transportation Research Record LA - en OP - SN - 0361-1981 2169-4052 UR - http://dx.doi.org/10.3141/2127-20 DB - Crossref ER - TY - JOUR TI - Performance-Based Uniformity Coefficient of Chip Seal Aggregate AU - Lee, Ju Sang AU - Kim, Y. Richard T2 - TRANSPORTATION RESEARCH RECORD AB - Development of a new chip seal performance indicator called the performance-based uniformity coefficient (PUC) is presented. The PUC uses the concepts of McLeod's failure criteria for chip seals and the uniformity coefficient used for soil, sand, and aggregate. The aggregate loss performance test, using the third-scale model mobile loading simulator, is used for evaluating the PUC. Results demonstrate that the methodology introduced in this research and McLeod's failure criteria can be excellent tools for narrowing the aggregate specifications required for chip seal construction. In addition to these results, the PUC, which is a gradation-based performance indicator, is an improvement over the previous uniformity coefficient for chip seal construction. The PUC can also aid in aggregate selection for the chip seal, and it can ease and clarify engineering communications within the chip seal industry. DA - 2009/// PY - 2009/// DO - 10.3141/2108-06 IS - 2108 SP - 53-60 SN - 0361-1981 ER - TY - JOUR TI - Light duty gasoline vehicle emission factors at high transient and constant speeds for short road segments AU - Choi, Hyung-Wook AU - Frey, H. Christopher T2 - TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT AB - Vehicle emissions estimates are needed at high spatial and temporal resolution to estimate near-roadway air quality and human exposures. The MOBILE6 emission factor model is based on transient test cycles of less than 65 mph. Correction factors for high speed and constant speed are developed based on vehicle-specific power-based modal models for light duty gasoline vehicles, using data from portable emission measurement systems. At 80 mph versus 65 mph, the estimated average emission rates are greater by 30%, 20%, 80%, and 10% for NOx, HC, CO, and CO2. The ratio of constant to average of transient speed emission rates range from 0.49 to 0.94 for NOx at speeds of 20 mph and 80 mph. The high speed and constant speed correction factors are applied to estimate vehicle emissions for a freeway segment that includes vehicle cruising speeds between 65 and 80 mph. The potential error for not accounting for constant speed operation on a short segment of highway could be 49% at moderate speed and 24% at high speed. DA - 2009/12// PY - 2009/12// DO - 10.1016/j.trd.2009.09.001 VL - 14 IS - 8 SP - 610-614 SN - 1361-9209 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-71249122701&partnerID=MN8TOARS KW - Speed correction factor KW - Segment emissions KW - Near-roadway KW - Air quality study ER - TY - JOUR TI - In-use measurement of the activity, fuel use, and emissions of eight cement mixer trucks operated on each of petroleum diesel and soy-based B20 biodiesel AU - Frey, H. Christopher AU - Kim, Kangwook T2 - TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT AB - In-use micro-scale fuel use and emission rates were measured for eight cement mixer trucks using a portable emission measurement system. Each vehicle was tested on petroleum diesel and B20 biodiesel. Average fuel use and emission rates increase monotonically versus engine manifold absolute pressure. A typical duty cycle includes loading at a cement plant, transit while loaded from the cement plant to work site, creeping in a queue of vehicles at the worksite, unloading, and transit without load from the site to the plant. For B20 versus petroleum diesel, there is no significant change in the rate of fuel use, CO2 emissions, and NO emissions, and significant decreases in emissions for CO, hydrocarbons, and particulate matter. For loaded versus unloaded onroad travel, fuel use and CO2 emissions rates are approximately 60% higher and the rates for other pollutants are approximately 30–50% higher. A substantial portion of cycle emissions occurred at the work site. Inter-vehicle and intra-cycle variability are also quantified using the micro-scale methodology. DA - 2009/12// PY - 2009/12// DO - 10.1016/j.trd.2009.08.004 VL - 14 IS - 8 SP - 585-592 SN - 1361-9209 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-71249088383&partnerID=MN8TOARS KW - In-use KW - Emissions KW - Fuel use KW - Diesel KW - B20 KW - Biodiesel KW - Cement mixer KW - Duty cycle ER - TY - JOUR TI - Improved water allocation utilizing probabilistic climate forecasts: Short-term water contracts in a risk management framework AU - Sankarasubramanian, A. AU - Lall, Upmanu AU - Souza Filho, Francisco Assis AU - Sharma, Ashish T2 - Water Resources Research AB - Probabilistic, seasonal to interannual streamflow forecasts are becoming increasingly available as the ability to model climate teleconnections is improving. However, water managers and practitioners have been slow to adopt such products, citing concerns with forecast skill. Essentially, a management risk is perceived in “gambling” with operations using a probabilistic forecast, while a system failure upon following existing operating policies is “protected” by the official rules or guidebook. In the presence of a prescribed system of prior allocation of releases under different storage or water availability conditions, the manager has little incentive to change. Innovation in allocation and operation is hence key to improved risk management using such forecasts. A participatory water allocation process that can effectively use probabilistic forecasts as part of an adaptive management strategy is introduced here. Users can express their demand for water through statements that cover the quantity needed at a particular reliability, the temporal distribution of the “allocation,” the associated willingness to pay, and compensation in the event of contract nonperformance. The water manager then assesses feasible allocations using the probabilistic forecast that try to meet these criteria across all users. An iterative process between users and water manager could be used to formalize a set of short‐term contracts that represent the resulting prioritized water allocation strategy over the operating period for which the forecast was issued. These contracts can be used to allocate water each year/season beyond long‐term contracts that may have precedence. Thus, integrated supply and demand management can be achieved. In this paper, a single period multiuser optimization model that can support such an allocation process is presented. The application of this conceptual model is explored using data for the Jaguaribe Metropolitan Hydro System in Ceara, Brazil. The performance relative to the current allocation process is assessed in the context of whether such a model could support the proposed short‐term contract based participatory process. A synthetic forecasting example is also used to explore the relative roles of forecast skill and reservoir storage in this framework. DA - 2009/11// PY - 2009/11// DO - 10.1029/2009wr007821 VL - 45 IS - 11 SP - J2 - Water Resour. Res. LA - en OP - SN - 0043-1397 UR - http://dx.doi.org/10.1029/2009WR007821 DB - Crossref ER - TY - JOUR TI - Daily Activity Patterns of University Students AU - Eom, Jin Ki AU - Stone, John R. AU - Ghosh, Sujit K. T2 - JOURNAL OF URBAN PLANNING AND DEVELOPMENT AB - This paper presents a comprehensive analysis of students’ activity characteristics and travel patterns based on the 2001 North Carolina State University Student Activity Travel Survey. Results show that undergraduate students and on-campus residents are engaged in more activities than graduate students and off-campus students. Graduate students are more likely to engage in class and work activity in the afternoon than in the morning. There is no statistically significant difference between student groups in terms of the proportion of students involved in a certain activity at a certain hour of the day. Instead, the types of activities are different across all 24 h of a day. The insights gained from this study will serve as the basis of an activity-based university travel demand model for North Carolina State University. DA - 2009/12// PY - 2009/12// DO - 10.1061/(ASCE)UP.1943-5444.0000015 VL - 135 IS - 4 SP - 141-149 SN - 1943-5444 ER - TY - JOUR TI - Controls on Landfill Gas Collection Efficiency: Instantaneous and Lifetime Performance AU - Barlaz, Morton A. AU - Chanton, Jeff P. AU - Green, Roger B. T2 - JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION AB - Estimates of landfill gas (LFG) collection efficiency are required to estimate methane emissions and the environmental performance of a solid waste landfill. The gas collection efficiency varies with time on the basis of the manner in which landfills are designed, operated, and regulated. The literature supports instantaneous collection efficiencies varying between 50% and near 100%, dependent on the cover type and the coverage of the LFG collection system. The authors suggest that the temporally weighted gas collection efficiency, which considers total gas production and collection over the landfill life, is the appropriate way to report collection efficiency. This value was calculated for a range of decay rates representative of refuse buried in arid and wet areas (i.e., >63.5 cm precipitation) and for bioreactor landfills. Temporally weighted collection efficiencies ranging from 67 to 91%, 62 to 86%, and 55 to 78% were calculated at decay rates of 0.02, 0.04, and 0.07 yr(-1), respectively. With aggressive gas collection, as would be implemented for a bioreactor landfill, estimated gas collection efficiency ranged from 84 to 67% at decay rates of 0.04 to 0.15 yr(-1), respectively. DA - 2009/12// PY - 2009/12// DO - 10.3155/1047-3289.59.12.1399 VL - 59 IS - 12 SP - 1399-1404 SN - 2162-2906 ER - TY - JOUR TI - Bond behaviour of FRP-to-clay brick masonry joints AU - Willis, C. R. AU - Yang, Q. AU - Seracino, R. AU - Griffith, M. C. T2 - ENGINEERING STRUCTURES AB - The out-of-plane bending and in-plane shear response of unreinforced modern clay brick masonry walls retrofitted with fibre-reinforced polymer (FRP) strips is often governed by debonding failure mechanisms. Hence, it is necessary to quantify the fundamental interface bond–slip model, which describes the debonding behaviour of the FRP-to-masonry interface. This paper presents the results of a series of 29 pull tests investigating the use of externally bonded (EB) and near surface mounted (NSM) retrofitting techniques. Test variables included: surface preparation; geometric properties; location of FRP (relative to perpend joints and cores); bonding agent of bed joints (mortar and quick drying paste); bonding method for glass fibre sheets (plate bonding and dry lay-up); and FRP material. A discussion of the test results and preliminary practical recommendations are also provided. A model used to predict the intermediate crack debonding resistance was verified against the test data. The model is generic in that it is applicable to both the EB and NSM retrofitting techniques. This generic model was shown to give very good ultimate strength predictions for the series of 29 pull tests conducted as part of this research. DA - 2009/11// PY - 2009/11// DO - 10.1016/j.engstruct.2009.06.006 VL - 31 IS - 11 SP - 2580-2587 SN - 1873-7323 KW - Intermediate crack debonding KW - Externally bonded KW - Near surface mounted KW - Pull test KW - Unreinforced masonry KW - Fibre-reinforced polymer ER - TY - JOUR TI - A Tunable Holistic Resiliency Approach for High-Performance Computing Systems AU - Scott, Stephen L. AU - Engelmann, Christian AU - Vallee, Geoffroy R. AU - Naughton, Thomas AU - Tikotekar, Anand AU - Ostrouchov, George AU - Leangsuksun, Chokchai AU - Naksinehaboon, Nichamon AU - Nassar, Raja AU - Paun, Mihaela AU - Mueller, Frank AU - Wang, Chao AU - Nagarajan, Arun B. AU - Varma, Jyothish T2 - ACM SIGPLAN NOTICES AB - In order to address anticipated high failure rates, resiliency characteristics have become an urgent priority for next-generation extreme-scale high-performance computing (HPC) systems. This poster describes our past and ongoing efforts in novel fault resilience technologies for HPC. Presented work includes proactive fault resilience techniques, system and application reliability models and analyses, failure prediction, transparent process- and virtual-machine-level migration, and trade-off models for combining preemptive migration with checkpoint/restart. This poster summarizes our work and puts all individual technologies into context with a proposed holistic fault resilience framework. DA - 2009/4// PY - 2009/4// DO - 10.1145/1594835.1504227 VL - 44 IS - 4 SP - 305-306 SN - 1558-1160 KW - Design KW - Measurement KW - Performance KW - Reliability ER - TY - JOUR TI - Working concept of accessibility performance measures for usability of crosswalks by pedestrians with vision impairments AU - Schroeder, B. J. AU - Rouphail, N. M. AU - Hughes, R. G. T2 - Transportation Research Record DA - 2009/// PY - 2009/// IS - 2140 SP - 103-110 ER - TY - JOUR TI - Phonon absorbing boundary conditions for molecular dynamics AU - Guddati, Murthy N. AU - Thirunavukkarasu, Senganal T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - With the goal of minimizing the domain size for molecular dynamics (MD) simulations, we develop a new class of absorbing boundary conditions (ABCs) that mimic the phonon absorption properties of an unbounded exterior. The proposed MD-ABCs are extensions of perfectly matched discrete layers (PMDLs), originally developed as an absorbing boundary condition for continuous wave propagation problems. Called MD-PMDL, this extension carefully targets the absorption of phonons, the high frequency waves, whose propagation properties are completely different from continuous waves. This paper presents the derivation of MD-PMDL for general lattice systems, followed by explicit application to one-dimensional and two-dimensional square lattice systems. The accuracy of MD-PMDL for phonon absorption is proven by analyzing reflection coefficients, and demonstrated through numerical experiments. Unlike existing MD-ABCs, MD-PMDL is local in both space and time and thus more efficient. Based on their favorable properties, it is concluded that MD-PMDL could provide a more effective alternative to existing MD-ABCs. DA - 2009/11// PY - 2009/11// DO - 10.1016/j.jcp.2009.07.033 VL - 228 IS - 21 SP - 8112-8134 SN - 1090-2716 KW - Atomistic-to-continuum coupling KW - Artificial boundary conditions KW - Absorbing boundary conditions KW - Perfectly matched layers ER - TY - JOUR TI - Modeling the Role of Transportation Information in Mitigating Major Capacity Reductions in a Regional Network AU - Hu, Hyejung AU - Williams, Billy AU - Rouphail, Nagui M. AU - Khattak, Asad J. AU - Zhou, Xuesong T2 - Transportation Research Record AB - A practical method is presented for systematically evaluating the network impacts of advanced traveler information systems (ATISs) to support well-informed project decisions and well-founded funding priorities. Detailed comparative assessments of available evaluation tools are given on the basis of a common set of desirable criteria. A mesoscopic network modeling and dynamic traffic assignment (DTA) tool, namely, DYNASMART-P, was identified as a promising candidate model and was applied to the evaluation of case study scenarios in a subnetwork of the Triangle Regional Model in North Carolina. The case study involved planned work zone activities occurring during nonpeak time periods. The case study demonstrated that the DYNASMART-P DTA tool is capable of providing reasonable evaluation results, including realistic estimates of the effectiveness of ATISs in mitigating the congestion caused by work zone activities. The case study analyses further illustrated the high value of traveler information through an example benefit–cost analysis based on the scenario modeling. The simulation results were validated for reasonableness through comparison with field speed data. Finally, several potential DTA functionality enhancements are identified that will further support ATIS evaluation. DA - 2009/// PY - 2009/// DO - 10.3141/2138-11 IS - 2138 SP - 75–84 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76749103439&partnerID=MN8TOARS ER - TY - JOUR TI - Proposal for concrete compressive strength up to 18 ksi (124 Mpa) for bridge design AU - Rizkalla, S. AU - Zia, P. AU - Mirmiran, A. AU - Russell, H. G. AU - Mast, R. T2 - Transportation Research Record DA - 2009/// PY - 2009/// IS - 2131 SP - 59-67 ER - TY - JOUR TI - Macro versus micro-scale constitutive models in simulating proportional and nonproportional cyclic and ratcheting responses of stainless steel 304 AU - Krishna, Shree AU - Hassan, Tasnim AU - Ben Naceur, Ilyes AU - Sai, Kacem AU - Cailletaud, Georges T2 - INTERNATIONAL JOURNAL OF PLASTICITY AB - A recent study by Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] demonstrated that some of the nonproportional ratcheting responses under stress-controlled loading histories cannot be simulated reasonably by two recent cyclic plasticity models. Two major drawbacks of the models identified were: (i) the stainless steel 304 demonstrated cyclic hardening under strain-controlled loading whereas cyclic softening under stress-controlled loading, which depends on the strain-range and which the existing models cannot describe; (ii) the change in biaxial ratcheting responses due to the change in the degree of nonproportionality were not simulated well by the models. Motivated by these findings, two modified cyclic plasticity models are evaluated in predicting a broad set of cyclic and ratcheting response of stainless steel 304. The experimental responses used in evaluating the modified models included both proportional (uniaxial) and nonproportional (biaxial) loading responses from Hassan and Kyriakides [Hassan, T., Kyriakides, S., 1994a. Ratcheting of cyclically hardening and softening materials. Part I: uniaxial behavior. Int. J. Plasticity, 10, 149–184; Hassan, T., Kyriakides, S., 1994b. Ratcheting of cyclically hardening and softening materials. Part II: multiaxial behavior. Int. J. Plasticity, 10, 185–212.] and Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] The first model studied is a macro-scale, phenomenological, constitutive model originally proposed by Chaboche et al. [Chaboche, J.L., Dang-Van, K., Cordier, G., 1979. Modelization of the strain memory effect on the cyclic hardening of 316 stainless steel. In: Proceedings of the Fifth International Conference on SMiRT, Div. L, Berlin, Germany, L11/3.]. This model was systematically modified for incorporating strain-range dependent cyclic hardening–softening, and proportional and nonproportional loading memory parameters. The second model evaluated is a polycrystalline model originally proposed by Cailletaud [Cailletaud, G., 1992. A micromechanical approach to inelastic behavior of metals. Int. J. Plasticity, 8, 55–73.] based on crystalline slip mechanisms. These two models are scrutinized against simulating hysteresis loop shape, cyclic hardening–softening, cross-effect, cyclic relaxation, subsequent cyclic softening and finally a broad set of ratcheting responses under uniaxial and biaxial loading histories. The modeling features which improved simulations for these responses are elaborated in the paper. In addition, a novel technique for simulating both the monotonic and cyclic responses with one set of model parameters is developed and validated. DA - 2009/10// PY - 2009/10// DO - 10.1016/j.ijplas.2008.12.009 VL - 25 IS - 10 SP - 1910-1949 SN - 1879-2154 KW - Cyclic plasticity KW - Nonproportional effects KW - Cross hardening KW - Ratcheting KW - Polycrystalline models ER - TY - JOUR TI - Effective Splices for a Carbon Fiber-Reinforced Polymer Strengthening System for Steel Bridges and Structures AU - Dawood, Mina AU - Guddati, Murthy AU - Rizkalla, Sami T2 - TRANSPORTATION RESEARCH RECORD AB - Carbon fiber–reinforced polymer (CFRP) materials have been used successfully to strengthen reinforced concrete bridges and structures. Recently, a new high modulus CFRP strengthening system was developed to increase the allowable load carrying capacity and to enhance the serviceability of steel bridges and structures. Because of the relatively high flexural rigidity of the CFRP materials, the length of the CFRP plates that can be transported to the job site is limited. To implement the proposed strengthening system in longer-span steel bridges, adjacent lengths of CFRP must be spliced. To develop an effective splice joint for the proposed strengthening system, an experimental and analytical research program was conducted to study the bond behavior of the CFRP materials. The parameters considered included plate end geometry, splice length, and the possibility of using mechanical anchorage. The analytical study included a finite element analysis to determine the distribution of the stresses within the adhesive layer for different splice configurations. On the basis of the findings, a simplified method was proposed to design lap splice joints with different reversed taper angles and adhesive properties. The research concluded that, with proper detailing, the proposed CFRP system could be effectively used to strengthen steel bridges and structures. DA - 2009/// PY - 2009/// DO - 10.3141/2131-12 IS - 2131 SP - 125-133 SN - 0361-1981 ER - TY - JOUR TI - Effect of Free Chlorine Application on Microbial Quality of Drinking Water in Chloraminated Distribution Systems AU - Rosenfeldt, E.J. AU - Baeza, C. AU - Knappe, D.R.U. T2 - Journal AWWA AB - The potential for bacterial regrowth and the formation of disinfection by‐products in distribution systems are issues of concern for many drinking water utilities. The principal objective of this study was to examine bacterial growth/regrowth in two chloraminated distribution systems before, during, and after a free chlorine flush. Raw water for both systems was of similar quality, but treatment trains differed, primarily in their use of ozone. To avoid culture‐based technique biases, cell counts were measured directly by nucleic acid staining and subsequent analysis by flow cytometry. During the free chlorine flush period, lower cell counts were obtained at all sampled locations in one distribution system, but only at long detention times in the second distribution system. Assimilable organic carbon levels were generally greater in the second distribution system, where ozonation was used in the treatment train. At an intermittent‐use facility, nitrification was mitigated after hydrant flushing led to the appearance of a free chlorine residual. However, without additional hydrant flushing, the free chlorine residual decayed and led to elevated levels of chloroform. In comparing tap water from both distribution systems with several commercially available bottled waters, bacteria levels were found to be higher in more than half of the bottled waters tested. DA - 2009/// PY - 2009/// DO - 10.1002/j.1551-8833.2009.tb09974.x VL - 101 IS - 10 SP - 60–70 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-73249126255&partnerID=MN8TOARS ER - TY - JOUR TI - Calibration of a single-mode polymer optical fiber large-strain sensor AU - Kiesel, Sharon AU - Peters, Kara AU - Hassan, Tasnim AU - Kowalsky, Mervyn T2 - MEASUREMENT SCIENCE AND TECHNOLOGY AB - We calibrate the phase shift as a function of applied displacement in a polymethylmethacrylate (PMMA) single-mode optical fiber interferometer, operating at a wavelength of 632.8 nm. The phase sensitivity is measured up to 15.8% nominal strain in the fiber. The measured phase–displacement response is compared to a previous analytical formulation for the large deformation response of the polymer optical fiber strain sensor. The formulation includes both the finite deformation of the optical fiber and nonlinear strain-optic effects at large deformations. Using previously measured values for the linear and nonlinear mechanical response of the fiber, the nonlinear strain-optic effects are calibrated from the current experimental data. This calibration demonstrates that the nonlinearities in the strain-optic effect are of the same order of magnitude as those in the mechanical response of the PMMA optical fiber sensor. DA - 2009/3// PY - 2009/3// DO - 10.1088/0957-0233/20/3/034016 VL - 20 IS - 3 SP - SN - 1361-6501 KW - polymer optical fiber KW - strain sensor KW - large deformation ER - TY - JOUR TI - Wave propagation velocity under a vertically vibrated surface foundation AU - Ahn, Jaehun AU - Biscontin, Giovanna AU - Roesset, Jose M. T2 - INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS AB - Abstract The ultimate objective of the research conducted by the authors is to explore the feasibility of determining reliable in situ values of soil modulus as a function of strain. In field experiments, an excitation is applied on the ground surface using large‐scale shakers, and the response of the soil deposit is recorded through receivers embedded in the soil. The focus of this paper is on the simulation and observation of signals that would be recorded at the receiver locations under idealized conditions to provide guidelines on the interpretation of the field measurements. Discrete models are used to reproduce one‐dimensional and three‐dimensional geometries. When the first times of arrival are detected by receivers under the vertical impulse, they coincide with the arrival of the P wave; therefore related to the constrained modulus of the material. If one considers, on the other hand, phase differences between the motions at two receivers, the picture is far more complicated and one would obtain propagation velocities, function of frequency and measuring location, which do not correspond to either the constrained modulus or Young's modulus. It is necessary then to conduct more rigorous and complicated analyses in order to interpret the data. This paper discusses and illustrates these points. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2009/6/25/ PY - 2009/6/25/ DO - 10.1002/nag.759 VL - 33 IS - 9 SP - 1153-1167 SN - 0363-9061 KW - wave propagation KW - surface foundation KW - dynamic interaction KW - vertical vibration KW - in situ test ER - TY - JOUR TI - Transport and release of chemicals from plastics to the environment and to wildlife AU - Teuten, E. L. AU - Saquing, J. M. AU - Knappe, D. R. U. AU - Barlaz, M. A. AU - Jonsson, S. AU - Bjorn, A. AU - Rowland, S. J. AU - Thompson, R. C. AU - Galloway, T. S. AU - Yamashita, R. AU - Ochi, D. AU - Watanuki, Y. AU - Moore, C. AU - Pham, H. V. AU - Tana, T. S. AU - Prudente, M. AU - Boonyatumanond, R. T2 - Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences DA - 2009/// PY - 2009/// VL - 364 IS - 1526 SP - 2027-2045 ER - TY - JOUR TI - Seismic behavior of shear-dominated reinforced concrete columns at low temperatures AU - Montejo, L. A. AU - Kowalsky, M. J. AU - Hassan, T. T2 - ACI Structural Journal AB - First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address DA - 2009/// PY - 2009/// DO - 10.14359/56610 VL - 106 IS - 4 SP - 445-454 ER - TY - JOUR TI - Comparison of Flexible Fuel Vehicle and Life-Cycle Fuel Consumption and Emissions of Selected Pollutants and Greenhouse Gases for Ethanol 85 Versus Gasoline AU - Zhai, Haibo AU - Frey, H. Christopher AU - Rouphail, Nagui M. AU - Goncalves, Goncalo A. AU - Farias, Tiago L. T2 - JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION AB - Abstract The objective of this research is to evaluate differences in fuel consumption and tailpipe emissions of flexible fuel vehicles (FFVs) operated on ethanol 85 (E85) versus gasoline. Theoretical ratios of fuel consumption and carbon dioxide (CO2) emissions for both fuels are estimated based on the same amount of energy released. Second-by-second fuel consumption and emissions from one FFV Ford Focus fueled with E85 and gasoline were measured under real-world traffic conditions in Lisbon, Portugal, using a portable emissions measurement system (PEMS). Cycle average dynamometer fuel consumption and emission test results for FFVs are available from the U.S. Department of Energy, and emissions certification test results for ethanol-fueled vehicles are available from the U.S. Environmental Protection Agency. On the basis of the PEMS data, vehicle-specific power (VSP)-based modal average fuel and emission rates for both fuels are estimated. For E85 versus gasoline, empirical ratios of fuel consumption and CO2 emissions agree within a margin of error to the theoretical expectations. Carbon monoxide (CO) emissions were found to be typically lower. From the PEMS data, nitric oxide (NO) emissions associated with some higher VSP modes are higher for E85. From the dynamometer and certification data, average hydrocarbon (HC) and nitrogen oxides (NOx) emission differences vary depending on the vehicle. The differences of average E85 versus gasoline emission rates for all vehicle models are −22% for CO, 12% for HC, and −8% for NOx emissions, which imply that replacing gasoline with E85 reduces CO emissions, may moderately decrease NOx tailpipe emissions, and may increase HC tailpipe emissions. On a fuel life cycle basis for corn-based ethanol versus gasoline, CO emissions are estimated to decrease by 18%. Life-cycle total and fossil CO2 emissions are estimated to decrease by 25 and 50%, respectively; however, life-cycle HC and NOx emissions are estimated to increase by 18 and 82%, respectively. DA - 2009/8// PY - 2009/8// DO - 10.3155/1047-3289.59.8.912 VL - 59 IS - 8 SP - 912-924 SN - 1096-2247 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70350516518&partnerID=MN8TOARS ER - TY - JOUR TI - Bond characteristics of ASTM A1035 steel reinforcing bars AU - Seliem, H. M. AU - Hosny, A. AU - Rizkalla, S. AU - Zia, P. AU - Briggs, M. AU - Miller, S. AU - Darwin, D. AU - Browning, J. AU - Glass, G. M. AU - Hoyt, K. AU - Donnelly, K. AU - Jirsa, J. O. T2 - ACI Structural Journal DA - 2009/// PY - 2009/// VL - 106 IS - 4 SP - 530-539 ER - TY - JOUR TI - Accuracy Evaluation and Sensitivity Analysis of Estimating 3D Road Centerline Length using Lidar and NED AU - Cai, Hubo AU - Rasdorf, William T2 - PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING AB - Highway networks are represented by linear spatial objects (road segments). Having accurate length information of road centerlines is critical in transportation. This paper presents a geographic information system (GIS)-based approach that overlays planimetric road centerlines and elevation data to model road centerlines in a 3D space and estimate their lengths. Elevation sources included light detection and ranging (lidar) and the National Elevation Dataset (NED). The estimated distances were compared to distance measurement instrument (DMI)-measured distances to evaluate the accuracy. The effects of elevation datasets with varying vertical accuracies were assessed. The relationship between road geometric properties and the accuracy of distance estimates was examined. We found that (a) the proposed 3D approach is efficient in estimating 3D road centerline distances, (b) using lidar point data improves the accuracy by 28 percent over the use of NED, and (c) certain road geometric properties have direct relationship with the accuracy of distance estimates. DA - 2009/6// PY - 2009/6// DO - 10.14358/PERS.75.6.657 VL - 75 IS - 6 SP - 657-665 SN - 0099-1112 ER - TY - JOUR TI - Accumulation and fragmentation of plastic debris in global environments AU - Barnes, David K. A. AU - Galgani, Francois AU - Thompson, Richard C. AU - Barlaz, Morton T2 - PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES AB - One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly understood. DA - 2009/7/27/ PY - 2009/7/27/ DO - 10.1098/rstb.2008.0205 VL - 364 IS - 1526 SP - 1985-1998 SN - 1471-2970 KW - persistent organic pollutants KW - marine debris KW - plastic production KW - landfill KW - microplastic ER - TY - JOUR TI - The Role of Monthly Updated Climate Forecasts in Improving Intraseasonal Water Allocation AU - Sankarasubramanian, A. AU - Lall, Upmanu AU - Devineni, Naresh AU - Espinueva, Susan T2 - JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY AB - Abstract Seasonal streamflow forecasts contingent on climate information are essential for short-term planning (e.g., water allocation) and for setting up contingency measures during extreme years. However, the water allocated based on the climate forecasts issued at the beginning of the season needs to be revised using the updated climate forecasts throughout the season. In this study, reservoir inflow forecasts downscaled from monthly updated precipitation forecasts from ECHAM4.5 forced with “persisted” SSTs were used to improve both seasonal and intraseasonal water allocation during the October–February season for the Angat reservoir, a multipurpose system, in the Philippines. Monthly updated reservoir inflow forecasts are ingested into a reservoir simulation model to allocate water for multiple uses by ensuring a high probability of meeting the end-of-season target storage that is required to meet the summer (March–May) demand. The forecast-based allocation is combined with the observed inflows during the season to estimate storages, spill, and generated hydropower from the system. The performance of the reservoir is compared under three scenarios: forecasts issued at the beginning of the season, monthly updated forecasts during the season, and use of climatological values. Retrospective reservoir analysis shows that the operation of a reservoir by using monthly updated inflow forecasts reduces the spill considerably by increasing the allocation for hydropower during above-normal-inflow years. During below-normal-inflow years, monthly updated streamflow forecasts could be effectively used for ensuring enough water for the summer season by meeting the end-of-season target storage. These analyses suggest the importance of performing experimental reservoir analyses to understand the potential challenges and opportunities in improving seasonal and intraseasonal water allocation by using real-time climate forecasts. DA - 2009/7// PY - 2009/7// DO - 10.1175/2009JAMC2122.1 VL - 48 IS - 7 SP - 1464-1482 SN - 1558-8432 ER - TY - JOUR TI - River Flood Forecasting Using Complementary Muskingum Rating Equations AU - Choudhury, Parthasarathi AU - Sankarasubramanian, A. T2 - JOURNAL OF HYDROLOGIC ENGINEERING AB - A model for real-time flood forecasting in river systems with large drainage areas has been developed. Flow variations between upstream and downstream stations are interlinked and are typically governed by reach properties. Unique paired variations establish useful flow correspondence resulting in inflow and outflow forecasting models for a reach. The proposed model can generate forecasts with increased lead time without applying a separate inflow forecasting model and can also provide updated forecasts essential for real-time applications. The model was applied to flood forecasting in Tar River Basin, N.C., covering a drainage area of 13,921km2 . The model aggregates multiple upstream flows to provide long range forecasts for two downstream stations in the basin. Applicability of the model in estimating complete upstream and downstream hydrographs was demonstrated using a textbook example. Application results indicate that the new model can provide complete and updatable evolution of hydrographs using the current flow state. DA - 2009/7// PY - 2009/7// DO - 10.1061/(ASCE)HE.1943-5584.0000046 VL - 14 IS - 7 SP - 745-751 SN - 1943-5584 ER - TY - JOUR TI - Requirements and Incentives for Reducing Construction Vehicle Emissions and Comparison of Nonroad Diesel Engine Emissions Data Sources AU - Lewis, Phil AU - Rasdorf, William AU - Frey, H. Christopher AU - Pang, Shih-Hao AU - Kim, Kangwook T2 - JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT-ASCE AB - Nonroad construction vehicles and equipment powered by diesel engines contribute to mobile source air pollution. The engines of this equipment emit significant amounts of carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter. These pollutants pose serious problems for human health and the environment. Therefore, it is necessary to regulate and control the levels of these pollutants. Furthermore, there are emerging requirements and incentives for “greening” of construction vehicle fleets and operations. Currently, there are two types of standards that regulate air pollution for these types of vehicles: technological standards for engines and quality standards for air. It is also necessary to quantify the levels of emissions that nonroad construction vehicles and equipment produce. Quantification may be based on existing data sources (such as the EPA NONROAD model) or by collecting data directly from the vehicles as they work in the field. The purpose of this paper is to introduce the challenges to quantification of emissions from nonroad construction vehicles, describe associated governmental regulations and incentives for reducing emissions, identify and compare various sources of emissions data, establish the need to collect additional data, and propose a future research agenda that focuses on air pollution generated by construction vehicles. DA - 2009/5// PY - 2009/5// DO - 10.1061/(ASCE)CO.1943-7862.0000008 VL - 135 IS - 5 SP - 341-351 SN - 0733-9364 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-65249158552&partnerID=MN8TOARS ER - TY - JOUR TI - Quantitative exposure model for the transmission of norovirus in retail food preparation AU - Mokhtari, Amirhossein AU - Jaykus, Lee-Ann T2 - INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY AB - It is widely recognized that the human noroviruses (HuNoV) are responsible for a large proportion of the world's foodborne disease burden. These viruses are transmitted by human fecal contamination and frequently make their way into foods because of poor personal hygiene of infected food handlers. This paper describes a probabilistic exposure assessment which models the dynamics of the transmission of HuNoV in the retail food preparation environment. Key inputs included degree of fecal shedding, hand hygiene behaviors, efficacy of virus removal and/or inactivation, and transferability of virus between surfaces. The model has a temporal dimension allowing contamination to be estimated as a function of time over the simulation period. Sensitivity and what-if scenario analyses were applied to identify the most important model inputs and evaluate potential mitigation strategies. The key inputs affecting estimates of the number of infectious viruses present in contaminated food servings, given the current model structure and assumptions, were as follows: mass of feces on hands (m(FH)), concentration of virus in feces (nv(CF)), number of bathroom visits, degree of gloving compliance (p(WG)), hand-washing efficiency (HW(eff)), and hand-washing compliance (p(HW)). The model suggests that gloving and hand-washing compliance are most effective in controlling contamination of food products when practiced simultaneously. Moreover, the bathroom environment was identified as a major reservoir of HuNoV, even in the absence of an ill individual on site. This mathematical approach to modeling the transmission of gastrointestinal viruses should facilitate comparison of potential mitigations aimed at reducing the transmission of foodborne viruses. DA - 2009/7/31/ PY - 2009/7/31/ DO - 10.1016/j.ijfoodmicro.2009.04.021 VL - 133 IS - 1-2 SP - 38-47 SN - 1879-3460 KW - Probabilistic risk assessment KW - Foodborne disease KW - Cross-contamination KW - Personal hygiene KW - Food handier KW - Sensitivity analysis ER - TY - JOUR TI - Membrane Effects in Biaxial Compression Tests AU - Frost, J. David AU - Evans, T. Matthew T2 - JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING AB - The effects of the confining membrane in laboratory tests on soil specimens have been the subject of numerous experimental, analytical, and numerical studies over the past half-century. This technical note expands the existing knowledge base by presenting a methodology and the associated results from an experimental study that has quantified the effect of the confining membrane in biaxial shear tests conducted on medium sand. The applicability of the method of biaxial tests on clay specimens is also presented. The results show that for both tests on sands and clays, the effect of the membrane on the shear stress on the failure plane are significant and should be accounted for in the interpretation of biaxial shear test results where localization occurs. DA - 2009/7// PY - 2009/7// DO - 10.1061/(ASCE)GT.1943-5606.0000011 VL - 135 IS - 7 SP - 986-991 SN - 1090-0241 ER - TY - PCOMM TI - Landfill gas recovery AU - Barlaz, Morton A. AB - ADVERTISEMENT RETURN TO ISSUEPREVLetterNEXTLandfill gas recoveryMorton A. BarlazView Author Information North Carolina State University[email protected]Cite this: Environ. Sci. Technol. 2009, 43, 9, 2995Publication Date (Web):April 29, 2009Publication History Published online29 April 2009Published inissue 1 May 2009https://doi.org/10.1021/es9004174Copyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views990Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (34 KB) Get e-AlertscloseSUBJECTS:Biological databases,Climate change,Energy conversion,Hydrocarbons,Wastes Get e-Alerts DA - 2009/5/1/ PY - 2009/5/1/ DO - 10.1021/es9004174 SP - 2995-2995 ER - TY - JOUR TI - Evaluation of Rotational Stiffness of Elastomeric Bearing Pad-Anchor Bolt Connections on Deep Foundation Bents AU - Vidot-Vega, Aidcer L. AU - Possiel, Ben AU - Robinson, Brent AU - Kowalsky, Mervyn J. AU - Gabr, Mohammed A. T2 - JOURNAL OF BRIDGE ENGINEERING AB - Experimental tests are performed on a bearing pad-anchor bolt connection to study rotational stiffness and moment transfer capabilities of a typical bridge configuration. The experimental program is divided in two phases. The first phase consisted of shear and compression properties of two types of bearing pads. The second phase consisted of a total of 42 full-scale tests of a bearing pad-anchor bolt connection. The tested bridge-bent configuration includes two AASHTO Type II girders made continuous with a slab and diaphragm, bearing pads, pile caps, and piles. Variables included axial loads applied to the piles and bearing pads, two different sets of bearing pads, and three different pile types. The bridge connection is subjected to lateral cyclic reversed loading in one-cycle displacement increments. Test results show the potential for this type of connection to sustain lateral loads and flexural moments, and to develop the full strength of the pile elements. Shear and compression modulus are also obtained for the bearing pad types used in this study. Rotational stiffness values for the connection are determined as a function of varying axial loads. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)BE.1943-5592.0000010 VL - 14 IS - 6 SP - 487-495 SN - 1084-0702 KW - Bolts KW - Deep foundations KW - Stiffness KW - Buckling KW - Bridges KW - Connections KW - Effective length ER - TY - JOUR TI - Wave-induced response of seabed: Various formulations and their applicability AU - Ulker, M. B. C. AU - Rahman, M. S. AU - Jeng, D. -S. T2 - APPLIED OCEAN RESEARCH AB - In this study, a set of generalized analytical solutions are developed for the wave-induced response of a saturated porous seabed under plane strain condition. When considering the water waves originating in deep water and travelling towards the shore, their velocities, lengths and heights vary. Depending on the characteristics of the wave and the properties of the seabed, different formulations (fully dynamic, partly dynamic, quasi-static) for the wave-induced response of the seabed are possible. The solutions for the response with these formulations are established in terms of non-dimensional parameters. The results are presented in terms of pore pressure, shear stress and vertical effective stress distributions within the seabed. For typical values of wave period and seabed permeability, the regions of applicability of the three formulations are identified and plotted in parametric spaces. With given wave and seabed characteristics, these regions provide quick identification of the appropriate formulation for an adequate evaluation of the wave-induced seabed response. DA - 2009/2// PY - 2009/2// DO - 10.1016/j.apor.2009.03.003 VL - 31 IS - 1 SP - 12-24 SN - 1879-1549 KW - Seabed KW - Water wave KW - Formulation KW - Analytical KW - Dynamics KW - Response ER - TY - JOUR TI - The effects of interdune vegetation changes on eolian dune field evolution: a numerical-modeling case study at Jockey's Ridge, North Carolina, USA AU - Pelletier, Jon D. AU - Mitasova, Helena AU - Harmon, Russell S. AU - Overton, Margery T2 - EARTH SURFACE PROCESSES AND LANDFORMS AB - Abstract Changes in vegetation cover within dune fields can play a major role in how dune fields evolve. To better understand the linkage between dune field evolution and interdune vegetation changes, we modified Werner's ( Geology , 23, 1995: 1107–1110) dune field evolution model to account for the stabilizing effects of vegetation. Model results indicate that changes in the density of interdune vegetation strongly influence subsequent trends in the height and area of eolian dunes. We applied the model to interpreting the recent evolution of Jockey's Ridge, North Carolina, where repeat LiDAR surveys and historical aerial photographs and maps provide an unusually detailed record of recent dune field evolution. In the absence of interdune vegetation, the model predicts that dunes at Jockey's Ridge evolve towards taller, more closely‐spaced, barchanoid dunes, with smaller dunes generally migrating faster than larger dunes. Conversely, the establishment of interdune vegetation causes dunes to evolve towards shorter, more widely‐spaced, parabolic forms. These results provide a basis for understanding the increase in dune height at Jockey's Ridge during the early part of the twentieth century, when interdune vegetation was sparse, followed by the decrease in dune height and establishment of parabolic forms from 1953‐present when interdune vegetation density increased. These results provide a conceptual model that may be applicable at other sites with increasing interdune vegetation cover, and they illustrate the power of using numerical modeling to model decadal variations in eolian dune field evolution. We also describe model results designed to test the relative efficacy of alternative strategies for mitigating dune migration and deflation. Installing sand‐trapping fences and/or promoting vegetation growth on the stoss sides of dunes are found to be the most effective strategies for limiting dune advance, but these strategies must be weighed against the desire of many park visitors to maintain the natural state of the dunes. Copyright © 2009 John Wiley & Sons, Ltd. DA - 2009/7// PY - 2009/7// DO - 10.1002/esp.1809 VL - 34 IS - 9 SP - 1245-1254 SN - 1096-9837 KW - eolian dunes KW - numerical modeling KW - biogeomorphology ER - TY - JOUR TI - Short-term mechanical properties of high-strength concrete AU - Logan, A. AU - Choi, W. AU - Mirmiran, A. AU - Rizkalla, S. AU - Zia, P. T2 - ACI Materials Journal DA - 2009/// PY - 2009/// VL - 106 IS - 5 SP - 413-418 ER - TY - JOUR TI - Regional On-Road Vehicle Running Emissions Modeling and Evaluation for Conventional and Alternative Vehicle Technologies AU - Frey, H. Christopher AU - Zhai, Haibo AU - Rouphail, Nagui M. T2 - ENVIRONMENTAL SCIENCE & TECHNOLOGY AB - This study presents a methodology for estimating high-resolution, regional on-road vehicle emissions and the associated reductions in air pollutant emissions from vehicles that utilize alternative fuels or propulsion technologies. The fuels considered are gasoline, diesel, ethanol, biodiesel, compressed natural gas, hydrogen, and electricity. The technologies considered are internal combustion or compression engines, hybrids, fuel cell, and electric. Road link-based emission models are developed using modal fuel use and emission rates applied to facility- and speed-specific driving cycles. For an urban case study, passenger cars were found to be the largest sources of HC, CO, and CO2 emissions, whereas trucks contributed the largest share of NOx emissions. When alternative fuel and propulsion technologies were introduced in the fleet at a modest market penetration level of 27%, their emission reductions were found to be 3−14%. Emissions for all pollutants generally decreased with an increase in the market share of alternative vehicle technologies. Turnover of the light duty fleet to newer Tier 2 vehicles reduced emissions of HC, CO, and NOx substantially. However, modest improvements in fuel economy may be offset by VMT growth and reductions in overall average speed. DA - 2009/11/1/ PY - 2009/11/1/ DO - 10.1021/es900535s VL - 43 IS - 21 SP - 8449-8455 SN - 1520-5851 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70350776818&partnerID=MN8TOARS ER - TY - JOUR TI - Inverse Analysis of Plate Load Tests to Assess Subgrade Resilient Modulus AU - Ahn, Jaehun AU - Cote, Benjamin M. AU - Robinson, Brent AU - Gabr, Mohammed A. AU - Borden, Roy H. T2 - TRANSPORTATION RESEARCH RECORD AB - Cyclic plate load testing is commonly used to investigate subgrade response under repetitive loads. Two frameworks for performing inverse analysis are described for backcalculating resilient moduli on the basis of measured key outputs. In the first approach, an elastic modulus is back-calculated in each selected domain; in the second, selected parameters in the resilient modulus model are estimated. The axisymmetric finite element model analysis results suggest that the second approach is more robust because it allows the modulus to be distributed in the selected domain. A series of sensitivity analyses was conducted with the second approach to illustrate how the assumed properties or model geometry affects the backcalculated parameters. Discrepancies between the back-calculated parameters and their known values were observed when the distance to the boundary–-that is, the radial distance from centerline to sidewall–-was not properly assigned. When backcalculating only selected parameters in the resilient modulus equation, it is necessary to assign the other parameters carefully (i.e., from laboratory tests or references). An example analysis shows the application of the proposed approach to an actual plate load test. DA - 2009/// PY - 2009/// DO - 10.3141/2101-13 VL - 2101 IS - 2101 SP - 110-117 SN - 2169-4052 ER - TY - JOUR TI - Determination of the appropriate representative elastic modulus for asphalt concrete AU - Underwood, B.S. AU - Kim, Y.R. T2 - International Journal of Pavement Engineering AB - The National Cooperative Highway Research Program (NCHRP) 1-37A mechanistic-empirical pavement design guide (MEPDG) utilises the dynamic modulus of asphalt concrete in a multilayered elastic analysis to determine the primary responses in asphalt pavements. The dynamic modulus depends on temperature and loading frequency. In the MEPDG, the pulse time is used to determine the loading frequency. This methodology has been under scrutiny due to the large modulus it estimates. This paper evaluates several approximation methods, including the current MEPDG analysis, for the calculation of stresses and strains in linear viscoelastic materials by comparing analysis results with the solutions from the exact linear viscoelastic analysis. Sources of the errors that result from various approximation methods are discussed. Also, an alternative method to that of the MEPDG is proposed for determining the appropriate representative elastic modulus of asphalt concrete. DA - 2009/4// PY - 2009/4// DO - 10.1080/10298430701827668 VL - 10 IS - 2 SP - 77-86 J2 - International Journal of Pavement Engineering LA - en OP - SN - 1029-8436 1477-268X UR - http://dx.doi.org/10.1080/10298430701827668 DB - Crossref KW - linear viscoelasticity KW - asphalt mixtures KW - dynamic modulus KW - frequency KW - MEPDG ER - TY - JOUR TI - Construction fatalities in Singapore AU - Ling, Florence Yean Yng AU - Liu, Min AU - Woo, Yue Chiau T2 - International Journal of Project Management AB - This study investigates proximal causes to 40 fatalities between 2006 and 2008 in Singapore’s construction industry. We statistically analyzed the data and found 11 characteristics of deceased workers, types of work, and the environment. Construction fatality causes in the US between 2003 and 2006 were also analyzed and compared with the data in Singapore. We developed 41 strategies to minimize fatalities. We interviewed seven Singapore and US construction safety managers for their opinions on the effectiveness of the strategies. We conclude that in addition to those recommended strategies, changes in organizational safety culture, enhancement of the penalty system, and effective communication are critical to improve safety performance in Singapore’s construction industry. DA - 2009/10// PY - 2009/10// DO - 10.1016/j.ijproman.2008.11.002 VL - 27 IS - 7 SP - 717-726 J2 - International Journal of Project Management LA - en OP - SN - 0263-7863 UR - http://dx.doi.org/10.1016/j.ijproman.2008.11.002 DB - Crossref KW - Fatalities KW - Construction accidents KW - Construction safety KW - Prevention KW - Risks ER - TY - JOUR TI - Backcalculation of subgrade stiffness under rubblised PCC slabs using multilevel FWD loads AU - Mun, Sungho AU - Kim, Y. Richard T2 - INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING AB - Rubblisation is an effective rehabilitation method for deteriorated Portland cement concrete (PCC) pavements due to its low initial costs, minimal traffic disruption and ability to minimise reflective cracking in asphalt overlays. However, the loss of strength in the PCC slab due to rubblisation creates the demand for a subgrade that is strong enough to handle traffic after rubblisation. This paper presents a research effort to develop an analysis method that allows the realistic estimation of subgrade stiffness after rubblisation from deflection measurements on intact PCC slabs before rubblisation. As a forward model, stress- and strain-dependent nonlinear subgrade models are incorporated into a finite element analysis (FEA). Based on the synthetic database generated from the FEA, different methodologies are developed to predict the coefficients in the nonlinear subgrade model from deflections under multilevel falling weight deflectometer loads. DA - 2009/// PY - 2009/// DO - 10.1080/10298430701827650 VL - 10 IS - 1 SP - 9-18 SN - 1477-268X KW - rubblisation KW - FWD KW - finite element analysis KW - nonlinear subgrade model KW - backcalculation ER - TY - JOUR TI - Removal of emerging contaminants of concern by alternative adsorbents AU - Rossner, Alfred AU - Snyder, Shane A. AU - Knappe, Detlef R. U. T2 - WATER RESEARCH AB - The effective removal of emerging contaminants of concern (ECCs) such as endocrine-disrupting chemicals, pharmaceutically active compounds, personal care products, and flame retardants is a desirable water treatment goal. In this study, one activated carbon, one carbonaceous resin, and two high-silica zeolites were studied to evaluate their effectiveness for the removal of an ECC mixture from lake water. Adsorption isotherm experiments were performed with a mixture of 28 ECCs at environmentally relevant concentrations (∼200–900 ng/L). Among the tested adsorbents, activated carbon was the most effective, and activated carbon doses typically used for taste and odor control in drinking water (<10 mg/L) were sufficient to achieve a 2-log removal for most of the tested ECCs. The carbonaceous resin was less effective than the activated carbon because this adsorbent had a smaller volume of pores in the size range required for the adsorption of many ECCs (∼6–9 Å). For the removal of ECC mixture constituents, zeolites were less effective than the carbonaceous adsorbents. Because zeolites contain pores of uniform size and shape, a few of the tested ECCs with matching pore size/shape requirements were well removed, but the adsorptive removal of others was negligible, even at zeolite doses of 100 mg/L. The results of this study demonstrate that effective adsorbents for the removal of a broad spectrum of ECCs from water should exhibit heterogeneity in pore size and shape and a large pore volume in the 6–9 Å size range. DA - 2009/8// PY - 2009/8// DO - 10.1016/j.watres.2009.06.009 VL - 43 IS - 15 SP - 3787-3796 SN - 0043-1354 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-67651091719&partnerID=MN8TOARS KW - Adsorption KW - Activated carbon KW - Zeolites KW - Emerging contaminants KW - Drinking water treatment ER - TY - JOUR TI - Probabilistic Exposure Analysis for Chemical Risk Characterization AU - Bogen, Kenneth T. AU - Cullen, Alison C. AU - Frey, H. Christopher AU - Price, Paul S. T2 - TOXICOLOGICAL SCIENCES AB - This paper summarizes the state of the science of probabilistic exposure assessment (PEA) as applied to chemical risk characterization. Current probabilistic risk analysis methods applied to PEA are reviewed. PEA within the context of risk-based decision making is discussed, including probabilistic treatment of related uncertainty, interindividual heterogeneity, and other sources of variability. Key examples of recent experience gained in assessing human exposures to chemicals in the environment, and other applications to chemical risk characterization and assessment, are presented. It is concluded that, although improvements continue to be made, existing methods suffice for effective application of PEA to support quantitative analyses of the risk of chemically induced toxicity that play an increasing role in key decision-making objectives involving health protection, triage, civil justice, and criminal justice. Different types of information required to apply PEA to these different decision contexts are identified, and specific PEA methods are highlighted that are best suited to exposure assessment in these separate contexts. DA - 2009/5// PY - 2009/5// DO - 10.1093/toxsci/kfp036 VL - 109 IS - 1 SP - 4-17 SN - 1096-0929 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-65549124897&partnerID=MN8TOARS KW - applied probability analysis KW - assessment methods KW - environmental chemicals KW - modeling KW - Monte Carlo KW - toxicity risk characterization ER - TY - JOUR TI - Peroxidase-Mediated Polymerization of 1-Naphthol: Impact of Solution pH and Ionic Strength AU - Bhandari, Alok AU - Xu, Fangxiang AU - Koch, David E. AU - Hunter, Robert P. T2 - JOURNAL OF ENVIRONMENTAL QUALITY AB - Peroxidase-mediated oxidation has been proposed as a treatment method for naphthol-contaminated water. However, the impact of solution chemistry on naphthol polymerization and removal has not been documented. This research investigated the impact of pH and ionic strength on peroxidase-mediated removal of 1-naphthol in completely mixed batch reactors. The impact of hydrogen peroxide to 1-naphthol ratio and activity of horseradish peroxidase was also studied. Size exclusion chromatography was used to estimate the molecular weight distribution of oligomeric products, and liquid chromatography/mass spectrometry was used to estimate product structure. Naphthol transformation decreased with ionic strength, and substrate removal was lowest at neutral pHs. Solution pH influenced the size and the composition of the oligomeric products. An equimolar ratio of H(2)O(2):naphthol was sufficient for optimal naphthol removal. Polymerization products included naphthoquinones and oligomers derived from two, three, and four naphthol molecules. Our results illustrate the importance of water chemistry when considering a peroxidase-based approach for treatment of naphthol-contaminated waters. DA - 2009/// PY - 2009/// DO - 10.2134/jeq2008.0426 VL - 38 IS - 5 SP - 2034-2040 SN - 0047-2425 ER - TY - JOUR TI - Pavement marking degradation modeling and analysis AU - Sitzabee, W. E. AU - Hummer, J. E. AU - Rasdorf, W. T2 - Journal of Infrastructure Systems AB - The objective of this research was to determine the performance characteristics of thermoplastic pavement markings in North Carolina and to create viable degradation models. Additionally, an evaluation of paint pavement-marking materials was conducted and models were created for them as well. The resulting models provide pavement-marking managers with valuable tools that will allow them to focus limited resources where they are most needed and avoid replacing materials with effective life still remaining in them. Consideration was given to the analysis of the relationships between pavement-marking retroreflectivity values and variables such as time, traffic volume, and marking color. Unique to this research is the inclusion of lateral location as a key variable affecting the performance of pavement markings. Another key contribution to pavement-marking management from this research was the development and use of level of service increments for describing the status of a given marking at some point in time. Using the tools reported herein an expected service life for thermoplastic and paint pavement markings in North Carolina can be estimated. A key finding of the research is that the markings have a far greater life expectancy than originally expected. Combining our predictive tool with level of service increments provides a holistic infrastructure management approach to pavement markings. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)1076-0342(2009)15:3(190) VL - 15 IS - 3 SP - 190-199 ER - TY - JOUR TI - Microstructural modeling of adaptive nanocomposite coatings for durability and wear AU - Pearson, James D. AU - Zikry, Mohammed A. AU - Wahl, Kathryn J. T2 - WEAR AB - Adaptive thin-film nanocomposite coatings comprised of crystalline ductile phases of gold and molybdenum disulfide, and brittle phases of diamond like carbon (DLC) and ytrria stabilized zirconia (YSZ) have been investigated by specialized microstructurally based finite-element techniques. One of the major objectives is to determine optimal crystalline and amorphous compositions and behavior related to wear and durability over a wide range of thermo-mechanical conditions. The interrelated effects of microstructural characteristics such as grain shapes and sizes, local material behavior due to interfacial stresses and strains, varying amorphous and crystalline compositions, and transfer film adhesion on coating behavior have been studied. The computational predictions, consistent with experimental observations, indicate specific interfacial regions between DLC and ductile metal inclusions are critical regions of stress and strain accumulation that can be precursors to material failure and wear. It is shown by varying the composition, resulting in tradeoffs between lubrication, toughness, and strength, the effects of these critical stresses and strains can be controlled for desired behavior. A mechanistic model to account for experimentally observed transfer film adhesion modes was also developed, and based on these results, it was shown that transfer film bonding has a significant impact on stress and wear behavior. DA - 2009/4/24/ PY - 2009/4/24/ DO - 10.1016/j.wear.2009.02.004 VL - 266 IS - 9-10 SP - 1003-1012 SN - 1873-2577 KW - Solid lubrication KW - Finite-element modeling KW - Sliding wear KW - Nanocomposite coating KW - Thin-film KW - Transfer film ER - TY - JOUR TI - Magnetic Properties of Self-Assembled Ni Nanoparticles in Two Dimensional Structures AU - Gupta, A. AU - Narayan, J. AU - Kumar, Dhananjay T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - A pulsed laser deposition technique has been used to synthesize a uniform distribution of Ni nanoparticles of controllable size in Al2O3 thin film matrix. The ability to control particle size in confined layers provides a very convenient means to tune the magnetic properties from superparamagnetic to ferromagnetic. The coercivity of these particles was measured at various temperatures as a function of particle size. The results indicate that the magnetic transition from single- to multi-domain region occurs at a larger particle size at higher temperature than at lower temperature. Stronger magnetic interaction among particles at lower temperatures is believed to lead to the formation of smaller sized domains for any given particle size in order to minimize the interaction energy. DA - 2009/6// PY - 2009/6// DO - 10.1166/jnn.2009.214 VL - 9 IS - 6 SP - 3993-3996 SN - 1533-4899 KW - Self-Assembly KW - Nanomagnetism KW - Pulsed Laser Deposition KW - Single and Multi Domain Nanoparticles ER - TY - JOUR TI - Evolutionary Computation-Based Methods for Characterizing Contaminant Sources in a Water Distribution System AU - Zechman, Emily M. AU - Ranjithan, S. Ranji T2 - Journal of Water Resources Planning and Management AB - The area of systematic identification of contamination sources in water distribution systems is in its infancy and is rapidly growing. The real water distribution network problem poses many challenges that current methods usually assume away to facilitate manageable method development and testing. Current methods may not readily and efficiently address issues, such as multiple sources, unknown contamination types with different reaction kinetics, use of different types of sensors with varying degree of resolution, dynamically varying demand and sensor information, and uncertainty and errors in the data and measurements. With the aim of addressing these imminent challenges, this paper reports the findings of an ongoing research investigation that develops and tests an evolutionary algorithm-based flexible and generic procedure, which is structured within a simulation-optimization paradigm. This paper describes the specific implementation of the method using evolution strategies (ESs), a population-based heuristic global search algorithm. A key component of designing this source characterization method is to define a compact, but comprehensive, solution encoding structure. The new method is constructed using a tree-based encoding design to enable the representation of variable-length decision vectors and a set of associated genetic operators that enable an efficient search. This algorithm is successfully tested and demonstrated to have consistently good performance for several instances of an illustrative water distribution contamination case study. As the ES-based algorithm conducts a probabilistic search, its robustness is tested using multiple random trials, and the method is shown to exhibit a robust behavior. DA - 2009/9// PY - 2009/9// DO - 10.1061/(ASCE)0733-9496(2009)135:5(334) VL - 135 IS - 5 SP - 334-343 J2 - J. Water Resour. Plann. Manage. LA - en OP - SN - 0733-9496 1943-5452 UR - http://dx.doi.org/10.1061/(asce)0733-9496(2009)135:5(334) DB - Crossref ER - TY - JOUR TI - Contaminant Source Identification in Water Distribution Networks Under Conditions of Demand Uncertainty AU - Vankayala, Praveen AU - Sankarasubramanian, A. AU - Ranjithan, S. Ranji AU - Mahinthakumar, G. T2 - ENVIRONMENTAL FORENSICS AB - Water distribution systems are susceptible to accidental and intentional chemical or biological contamination that could result in adverse health impact to the consumers. This study focuses on a water distribution forensics problem, contaminant source identification, subject to water demand uncertainty. Due to inherent variability in water consumption levels, demands at consumer nodes remain one of the major sources of uncertainty. In this research, the nodal demands are considered to be stochastic in nature and are varied using Gaussian and Autoregressive models. A hypothetical source identification problem is constructed by simulating observations at the sensor nodes from an arbitrary contaminant source. A simulation-optimization approach is used to solve the source identification problem with EPANET tool as the simulator and Genetic Algorithm (GA) as the optimizer. The goal is to find the source location and concentration by minimizing the difference between the simulated and observed concentrations at the sensor nodes. Two variations of GA, stochastic GA and noisy GA are applied to the same problem for comparison. Results show that noisy GA is more robust and is less computationally expensive than stochastic GA in solving the source identification problem. Moreover, the autoregressive demand uncertainty model better represents the uncertainty in the source identification process than the Gaussian model. DA - 2009/// PY - 2009/// DO - 10.1080/15275920903140486 VL - 10 IS - 3 SP - 253-263 SN - 1527-5930 KW - contaminant source identification KW - water distribution system KW - noisy genetic algorithms KW - uncertainty KW - optimization simulation ER - TY - JOUR TI - Composition of Municipal Solid Waste in the United States and Implications for Carbon Sequestration and Methane Yield AU - Staley, Bryan F. AU - Barlaz, Morton A. T2 - JOURNAL OF ENVIRONMENTAL ENGINEERING AB - Eleven statewide waste characterization studies were compared to assess variation in the quantity and composition of waste after separation of recyclable and compostable materials, i.e., discarded waste. These data were also used to assess the impact of varying composition on sequestered carbon and methane yield. Inconsistencies in the designation of waste component categories and definitions were the primary differences between study methodologies; however, sampling methodologies were consistent with recommended protocols. The average municipal solid waste (MSW) discard rate based on the statewide studies was 1.90 kg MSW person−1 day−1, which was within the range of two national estimates: 2.35 and 1.46 kg MSW person−1 day−1. Dominant components in MSW discards were similar between studies. Organics (food waste, yard trimmings), paper, and plastic components averaged 23.6±4.9%, 28.5±6.5%, and 10.6±3.0% of discarded MSW, respectively. Construction and demolition (C&D) waste was 20.2±9.7% of total solid waste discards (i.e., MSW plus C&D). Based on average statewide waste composition data, a carbon sequestration factor (CSF) for MSW of 0.13 kg C dry kg MSW−1 was calculated. For C&D waste, a CSF of 0.14 kg C dry kg C and D waste−1 was estimated. Ultimate methane yields (Lo) of 59.1 and 63.9 m3CH4 wet Mg refuse−1 were computed using EPA and state characterization study data, respectively, and were lower than AP-42 guidelines. Recycling, combustion, and other management practices at the local level could significantly impact CSF and (Lo) estimates, which are sensitive to the relative fraction of organic components in discarded MSW and C&D waste. DA - 2009/10// PY - 2009/10// DO - 10.1061/(asce)ee.1943-7870.0000032 VL - 135 IS - 10 SP - 901-909 SN - 1943-7870 ER - TY - JOUR TI - Bond behavior of near-surface mounted frp strips bonded to modern clay brick masonry prisms: Influence of strip orientation and compression perpendicular to the strip AU - Petersen, R. B. AU - Masia, M. J. AU - Seracino, R. T2 - Journal of Composites for Construction AB - In this paper the results of 18 pull tests performed on clay brick masonry prisms strengthened with near-surface mounted carbon fiber-reinforced polymer (CFRP) strips are presented. The pull tests were designed to add to the existing database and investigate variables significant to masonry construction. FRP was bonded to solid clay brick masonry; FRP aligned both perpendicular and parallel to the bed joint; and in the case of FRP reinforcement aligned parallel to the bed joint, compression applied perpendicular to the strip was used to simulate vertical compression load in masonry walls. Results including bond strength, critical bond length, and the local bond-slip relationship are presented as well as a discussion on the effect of the new variables on these results. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)1090-0268(2009)13:3(169) VL - 13 IS - 3 SP - 169-178 ER - TY - JOUR TI - Behavior of steel monopoles strengthened with high-modulus CFRP materials AU - Lanier, B. AU - Schnerch, D. AU - Rizkalla, S. T2 - THIN-WALLED STRUCTURES AB - This paper introduces a strengthening technique for steel monopole towers using high-modulus carbon fiber reinforced polymer (CFRP) materials. The technique is based on a theoretical and analytical investigation including testing large scale steel monopole towers strengthened with different CFRP materials and connection details. Based on the research findings, design aspects and installation procedures are introduced. The recommended installation procedure describes the surface preparation, application of the adhesives and the sequence of CFRP application. The design aspects are based on flexural elastic analysis and material properties of the CFRP and steel monopole shaft. This paper recommends specific connection details to ensure the development of the forces from the CFRP to the steel tower baseplate. The research findings conclude that CFRP materials provide a viable alternative for strengthening steel monopoles that can be easily designed and installed to increase their flexural strength and stiffness. DA - 2009/10// PY - 2009/10// DO - 10.1016/j.tws.2008.10.010 VL - 47 IS - 10 SP - 1037-1047 SN - 1879-3223 KW - Elastic modulus KW - Carbon fiber reinforced polymers KW - Steel structures KW - Design recommendations KW - Monopole towers ER - TY - JOUR TI - A parallel evolutionary strategy based simulation–optimization approach for solving groundwater source identification problems AU - Mirghani, Baha Y. AU - Mahinthakumar, Kumar G. AU - Tryby, Michael E. AU - Ranjithan, Ranji S. AU - Zechman, Emily M. T2 - Advances in Water Resources AB - Groundwater characterization involves the resolution of unknown system characteristics from observation data, and is often classified as an inverse problem. Inverse problems are difficult to solve due to natural ill-posedness and computational intractability. Here we adopt the use of a simulation–optimization approach that couples a numerical pollutant-transport simulation model with evolutionary search algorithms for solution of the inverse problem. In this approach, the numerical transport model is solved iteratively during the evolutionary search. This process can be computationally intensive since several hundreds to thousands of forward model evaluations are typically required for solution. Given the potential computational intractability of such a simulation–optimization approach, parallel computation is employed to ease and enable the solution of such problems. In this paper, several variations of a groundwater source identification problem is examined in terms of solution quality and computational performance. The computational experiments were performed on the TeraGrid cluster available at the National Center for Supercomputing Applications. The results demonstrate the performance of the parallel simulation–optimization approach in terms of solution quality and computational performance. DA - 2009/9// PY - 2009/9// DO - 10.1016/j.advwatres.2009.06.001 VL - 32 IS - 9 SP - 1373-1385 J2 - Advances in Water Resources LA - en OP - SN - 0309-1708 UR - http://dx.doi.org/10.1016/j.advwatres.2009.06.001 DB - Crossref KW - Evolutionary algorithms KW - Inverse problems KW - Parallel simulation-optimization framework KW - Groundwater source identification problem KW - High performance computing ER - TY - JOUR TI - Visualization and analysis of microstructure in three-dimensional discrete numerical models AU - Evans, T. M. AU - Chall, S. AU - Zhao, X. L. AU - Rhyne, T. M. T2 - Journal of Computing in Civil Engineering AB - A computer program has been developed to allow for the virtual slicing of irregularly spaced and irregularly shaped three-dimensional image data. The program was used to virtually slice three-dimensional particle assemblies from discrete element method (DEM) simulations, allowing, for the first time, direct comparison to two-dimensional slices extracted from solidified physical specimens. Based on slices obtained from the numerical specimens, it is possible to compare quantitatively numerical microstructure directly to its physical analog, which should lead to greatly improved calibrations of granular mechanics models, and could facilitate the calibration of models across all scales of interest rather than solely at specimen boundaries. Improved confidence in the ability of the DEM to realistically simulate the microstructure of granular assemblies (through improved multiscale calibration) should result in increased confidence in microstructural parameters measurable in numerical simulations but inaccessible in the laboratory. Algorithm development within the framework of the open-source Visualization Toolkit is described and performance of the algorithm is quantified for two platforms. Results from virtual slices of a test assembly with regular particle packing are verified against known analytical solutions. A slice of a more complex assembly comprised of nearly 40,000 spheres is quantified statistically and compared to an analogous slice from a physical specimen of uniform sand. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0887-3801(2009)23:5(277) VL - 23 IS - 5 SP - 277-287 ER - TY - JOUR TI - The effect of shredding and test apparatus size on compressibility and strength parameters of degraded municipal solid waste AU - Hossain, M. S. AU - Gabr, M. A. AU - Asce, F. T2 - WASTE MANAGEMENT AB - In many situations, MSW components are processed and shredded before use in laboratory experiments using conventional soil testing apparatus. However, shredding MSW material may affect the target property to be measured. The objective of this study is to contribute to the understanding of the effect of shredding of MSW on the measured compressibility and strength properties. It is hypothesized that measured properties can be correlated to an R-value, the ratio of waste particle size to apparatus size. Results from oedometer tests, conducted on 63.5 mm, 100 mm, 200 mm diameter apparatus, indicated the dependency of the compressibility parameters on R-value. The compressibility parameters are similar for the same R-value even though the apparatus size varies. The results using same apparatus size with variable R-values indicated that shredding of MSW mainly affects initial compression. Creep and biological strain rate of the tested MSW are not significantly affected by R-value. The shear strength is affected by shredding as the light-weight reinforcing materials are shredded into smaller pieces during specimen preparation. For example, the measured friction angles are 32° and 27° for maximum particle sizes of 50 mm and 25 mm, respectively. The larger MSW components in the specimen provide better reinforcing contribution. This conclusion is however dependent on comparing specimen at the same level of degradation since shear strength is also a function of extent of degradation. DA - 2009/9// PY - 2009/9// DO - 10.1016/j.wasman.2009.03.024 VL - 29 IS - 9 SP - 2417-2424 SN - 0956-053X ER - TY - JOUR TI - Real-World Energy Use and Emission Rates for Idling Long-Haul Trucks and Selected Idle Reduction Technologies AU - Frey, H. Christopher AU - Kuo, Po-Yao T2 - JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION AB - Abstract Long-haul freight trucks typically idle for 2000 or more hours per year, motivating interest in reducing idle fuel use and emissions using auxiliary power units (APUs) and shore-power (SP). Fuel-use rates are estimated based on electronic control unit (ECU) data for truck engines and measurements for APU engines. Engine emission factors were measured using a portable emission measurement system. Indirect emissions from SP were based on average utility grid emission factors. Base engine fuel use and APU and SP electrical load were analyzed for 20 trucks monitored for more than 1 yr during 2.76 million mi of activity within 42 U.S. states. The average base engine fuel use varied from 0.46 to 0.65 gal/hr. The average APU fuel use varied from 0.24 to 0.41 gal/hr. Fuel-use rates are typically lowest in mild weather, highest in hot or cold weather, and depend on engine speed (revolutions per minute [RPM]). Compared with the base engine, APU fuel use and emissions of carbon dioxide (CO2) and sulfur dioxide (SO2) are lower by 36–47%. Oxides of nitrogen (NOx) emissions are lower by 80–90%. Reductions in particulate matter (PM), carbon monoxide (CO), and hydrocarbon emissions vary from approximately 10 to over 50%. SP leads to more substantial reductions, except for SO2. The actual achievable reductions will be lower because only a fraction of base engine usage will be replaced by APUs, SP, or both. Recommendations are made for reducing base engine fuel use and emissions, accounting for variability in fuel use and emissions reductions, and further work to quantify real-world avoided fuel use and emissions. DA - 2009/7// PY - 2009/7// DO - 10.3155/1047-3289.59.7.857 VL - 59 IS - 7 SP - 857-864 SN - 2162-2906 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-68649109612&partnerID=MN8TOARS ER - TY - JOUR TI - Life cycle inventory energy consumption and emissions for biodiesel versus petroleum diesel fueled construction vehicles AU - Pang, S. H. AU - Frey, H. Christopher AU - Rasdorf, W. J. T2 - Environmental Science & Technology DA - 2009/// PY - 2009/// DO - 10.1021/os802916u VL - 43 IS - 16 SP - 6398–6405 ER - TY - JOUR TI - Effects of Idle Reduction Technologies on Real World Fuel Use and Exhaust Emissions of Idling Long-Haul Trucks AU - Frey, H. Christopher AU - Kuo, Po-Yao AU - Villa, Charles T2 - ENVIRONMENTAL SCIENCE & TECHNOLOGY AB - Idling long-haul freight trucks may consume nearly one billion gallons of diesel fuel per year in the U.S. There is a need for real-world data by which to quantify avoided fuel use and emissions attributable to idle reduction techniques of auxiliary power units (APUs) and shore-power (SP). Field data were obtained from 20 APU-equipped and SP-compatible trucks observed during 2.8 million miles of travel in 42 states. Base engine fuel use and emission rates varied depending on ambient temperature. APU and SP energy use and emission rates varied depending on electrical load. APUs reduced idling fuel use and CO2 emissions for single and team drivers by 22 and 5% annually, respectively. SP offers greater reductions in energy use of 48% for single drivers, as well as in emissions, except for SO2. APUs were cost-effective for single drivers with a large number of APU usage hours per year, but not for team drivers or for single drivers with low APU utilization rates. The findings support more accurate assessments of avoided fuel use and emissions, and recommendations to encourage greater APU utilization by single drivers and to further develop infrastructure for SP. DA - 2009/9/1/ PY - 2009/9/1/ DO - 10.1021/es900186e VL - 43 IS - 17 SP - 6875-6881 SN - 1520-5851 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-69549124649&partnerID=MN8TOARS ER - TY - JOUR TI - Data integration of pavement markings: A case in transportation asset management AU - Sitzabee, W. E. AU - Rasdorf, W. AU - Hummer, J. E. AU - Devine, H. A. T2 - Journal of Computing in Civil Engineering AB - Effective transportation asset management requires the implementation of tools such as software, hardware, databases, and data collection systems. Pavement markings make up one component in transportation asset management, which are complex networks that require large databases. Typically these databases are maintained in different areas within an agency and are most often incompatible. Combining new and old tools, this paper addresses the need for better data integration and utilization while incorporating current information technologies. Specifically, this paper presents integrated transportation asset management system for estimating the current and future condition of pavement markings. The paper describes the data structure, in the form of a physical model, integrating a pavement marking relational data schema with existing information technology systems. Software was found to be useful in developing the data schema. The software produced an extensible markup language file that is compatible with a variety of existing database structures such as Oracle, SQL, and MS Access. Additionally, the system included an algorithm, which implements the data structure and predictive models to estimate the condition of the asset at any point in time or space on the highway system. Using either measured data or predicted data the system gives managers an opportunity to decide on the best possible condition state of the asset and perform queries or optimizations. Ultimately, managers can develop cost effective strategies for pavement marking asset management. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0887-3801(2009)23:5(288) VL - 23 IS - 5 SP - 288-298 ER - TY - JOUR TI - Computational design of thin-film nanocomposite coatings for optimized stress and velocity accommodation response AU - Pearson, J. D. AU - Zikry, M. A. AU - Wahl, K. T2 - WEAR AB - The tailoring of thin-film coatings comprised of high strength nano-grained constituents is investigated by new microstructurally based finite-element techniques for applications related to the wear, durability, and performance of these coatings over a broad range of temperatures and loading conditions. These coatings are comprised of brittle phases, diamond-like carbon and partially stabilized zirconia and ductile constituents, such as gold and molybdenum. The effects of wear, contact transfer films, grain sizes and distributions, grain spacing and strength are used to determine the optimal thin-film coating compositions. Comparisons are made with experimental measurements pertaining to durability and wear for validation and for the development of design guidelines for thin-film nanocomposite coatings. DA - 2009/6/15/ PY - 2009/6/15/ DO - 10.1016/j.wear.2008.11.027 VL - 267 IS - 5-8 SP - 1137-1145 SN - 1873-2577 KW - Nanocomposite KW - Thin-film coating KW - Solid lubricant KW - Finite-element modeling ER - TY - JOUR TI - A Numerical Tool for Estimating Pollutant Emissions and Vehicles Performance in Traffic Interruptions on Urban Corridors AU - Coelho, Margarida C. AU - Farias, Tiago L. AU - Rouphail, Nagui M. T2 - INTERNATIONAL JOURNAL OF SUSTAINABLE TRANSPORTATION AB - ABSTRACT The principal objective of this research was to develop and apply a traffic and emission decision support (TEDS) tool to urban highway corridors. This model simulates traffic while predicting time elapsed, energy consumed, and pollutants emitted to the atmosphere by vehicles on the corridor. Because emissions from internal combustion engines are very high during speed-change cycles, congested stop-and-go traffic can be very detrimental to local levels of pollution. Thus, the research was mainly focused on the existence and quantification of effects for local singularities (or traffic interruptions), such as pay tolls, roundabouts, and traffic signals within the corridor. This approach yielded a numerical predictive model, based on experimental measurements and concepts of traffic flow theory, which explains the interaction between the system operational variables of each traffic interruption and the environmental and traffic performance variables. In particular, the focus was on carbon monoxide, carbon dioxide, nitric oxide, and hydrocarbons emissions and their relation to queue length and stops. The proposed traffic and emission estimation models provide an overall pollution estimate for a traffic interruption under any control configuration and traffic demand pattern. DA - 2009/// PY - 2009/// DO - 10.1080/15568310802175641 VL - 3 IS - 4 SP - 246-262 SN - 1556-8334 KW - numerical model KW - queue length KW - stop and go KW - traffic interruptions KW - vehicle emissions ER - TY - JOUR TI - Response of saturated and nearly saturated porous media: Different formulations and their applicability AU - Ulker, M. B. C. AU - Rahman, M. S. T2 - INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS AB - Abstract The response of saturated porous medium is of significant interest in many fields ranging from geomechanics to biomechanics. Biot was the first to formulate the basic equations governing the process of coupled flow and deformation in porous media. Depending on the nature of loading vis‐à‐vis the characteristics of the media, different formulations (fully dynamic, partly dynamic, quasi‐static) are possible. In this study, analytical solutions are developed for the response of saturated and nearly saturated porous media under plane strain condition. The solutions for different formulations are developed in terms of non‐dimensional parameters. The response is studied for various conditions and the regions of validity for various formulations are identified in a parametric space. An assessment of the needed formulation for few important problems is also presented. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2009/4/10/ PY - 2009/4/10/ DO - 10.1002/nag.739 VL - 33 IS - 5 SP - 633-664 SN - 1096-9853 KW - porous KW - flow KW - deformation KW - dynamics KW - response KW - saturated KW - analytical ER - TY - JOUR TI - Mineral Filler Reinforcement for Commingled Recycled-Plastic Materials AU - Putra, H. D. AU - Ngothai, Y. AU - Ozbakkaloglu, T. AU - Seracino, R. T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Three types of mineral fillers, gypsum, wollastonite, and talc, were investigated for their ability to modify the mechanical properties of commingled recycled‐plastic composites containing 0.07–0.26 v/v of filler. Mechanical test results showed that the talc reinforced composites were significantly better in mechanical properties when compared with the gypsum and wollastonite composites. Scanning electron microscopy (SEM) showed that gypsum formed large agglomerates in the matrix. Interfacial adhesion between filler and matrix was evaluated using simple empirical models. To enhance the adhesion, talc, and wollastonite were pretreated with silane coupling agents, 3‐methacryloxypropyltrimethoxy silane (γ‐MPS) and 3‐aminopropyltriethoxy silane (γ‐APS). This did not result in any significant improvement to the material properties. The γ‐APS treatment, however, increased the tensile properties of the composites by ∼ 5% when compared with the γ‐MPS treatment. The SEM investigations showed that the γ‐APS treatment provided better adhesion of filler particles and hence voids were less likely to form in the matrix when compared with the γ‐MPS composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 DA - 2009/6/15/ PY - 2009/6/15/ DO - 10.1002/app.29861 VL - 112 IS - 6 SP - 3470-3481 SN - 1097-4628 KW - commingled recycled plastic KW - mineral fillers KW - silanes ER - TY - JOUR TI - Assessing the Impact of Upstream Hydraulics on the Dose Distribution of Ultraviolet Reactors Using Fluorescence Microspheres and Computational Fluid Dynamics AU - Zhao, , Xi AU - Alpert, Scott M. AU - Ducoste, Joel J. T2 - ENVIRONMENTAL ENGINEERING SCIENCE AB - The ultraviolet (UV) dose distribution in an UV reactor was evaluated under multiple upstream configurations using UV-sensitive fluorescent microspheres and computational fluid dynamics (CFD). The upstream hydraulics configurations included two orientations of 90-degree bends and one straight pipe inlet. Experimental tests and numerical simulations were performed on a single-lamp low-pressure high-output (LPHO) UV reactor operating at a 50-gpm flow rate and 91% UV transmittance (UVT). Both the numerical and experimental results showed that the straight pipe configuration produced a shift in the UV dose distribution to a higher UV dose range compared to the two elbow configurations. The experimental UV dose distribution displayed no significant difference between the two elbow configurations while a slight difference in the location of the peak was noted between the two elbow configurations for the numerical model. Compared to the experimental results, the CFD model predicted slightly higher reduction equivalent dose (RED) values and higher RED biases. The CFD UV dose distribution displayed taller peaks for all three configurations and higher low UV dose region compared to the experimental distributions. DA - 2009/5// PY - 2009/5// DO - 10.1089/ees.2008.0139 VL - 26 IS - 5 SP - 947-959 SN - 1557-9018 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-67249087634&partnerID=MN8TOARS KW - ultraviolet light KW - UV KW - disinfection KW - dose KW - microspheres ER - TY - JOUR TI - Use of Life-Cycle Analysis To Support Solid Waste Management Planning for Delaware AU - Kaplan, P. Ozge AU - Ranjithan, S. Ranji AU - Barlaz, Morton A. T2 - ENVIRONMENTAL SCIENCE & TECHNOLOGY AB - Mathematical models of integrated solid waste management (SWM) are useful planning tools given the complexity of the solid waste system and the interactions among the numerous components that constitute the system. An optimization model was used in this study to identify and evaluate alternative plans for integrated SWM for the State of Delaware in consideration of cost and environmental performance, including greenhouse gas (GHG) emissions. The three counties in Delaware were modeled individually to identify efficient SWM plans in consideration of constraints on cost, landfill diversion requirements, GHG emissions, and the availability of alternate treatment processes (e.g., recycling, composting, and combustion). The results show that implementing a landfill diversion strategy (e.g., curbside recycling) for only a portion of the population is most cost-effective for meeting a county-specific landfill diversion target. Implementation of waste-to-energy offers the most cost-effective opportunity for GHG emissions reductions. DA - 2009/3/1/ PY - 2009/3/1/ DO - 10.1021/es8018447 VL - 43 IS - 5 SP - 1264-1270 SN - 0013-936X ER - TY - JOUR TI - Strengthening of prestressed concrete girders with composites: Installation, design and inspection AU - Rosenboom, Owen AU - Walter, Catrina AU - Rizkalla, Sami T2 - CONSTRUCTION AND BUILDING MATERIALS AB - The application of fibre reinforced polymer (FRP) or steel reinforced polymer (SRP) materials to the tension side of a reinforced/prestressed concrete member has been accepted as a strengthening technique to increase the load carrying capacity and in some cases can enhance member serviceability. Proper installation and regular inspection of a composite (FRP or SRP) strengthening system is important since quality of the bond is essential to internally transfer forces. This paper describes an experimental programme conducted to study the behaviour of six prestressed concrete bridge girders, which were tested under static and fatigue loading conditions. The test results were combined with the results of 16 other girders tested by the authors to develop structural design guidelines and guidelines on the installation and inspection of composite strengthening systems. The behaviour was also examined using value engineering to evaluate the cost-effectiveness by investigating the overall system performance. Research findings indicate that SRP materials are more structurally efficient than carbon FRP (CFRP) materials. The results of an inspection demonstration programme, including the pull-off testing of over 150 CFRP samples, has shown that the most effective inspection techniques are visual inspection, pull-off testing, and acoustic sounding. DA - 2009/4// PY - 2009/4// DO - 10.1016/j.conbuildmat.2007.11.010 VL - 23 IS - 4 SP - 1495-1507 SN - 1879-0526 KW - Prestressed KW - Strengthening KW - Installation procedures KW - Fibre reinforced polymers KW - Steel reinforced polymers KW - Bridge girder KW - Inspection procedures KW - Value engineering ER - TY - JOUR TI - Raster-Based Analysis of Coastal Terrain Dynamics from Multitemporal Lidar Data AU - Mitasova, Helena AU - Overton, Margery F. AU - Recalde, Juan Jose AU - Bernstein, David J. AU - Freeman, Christopher W. T2 - JOURNAL OF COASTAL RESEARCH AB - Multitemporal sets of lidar data provide a unique opportunity to analyze and quantify changes in topography in rapidly evolving landscapes. Methodology for geospatial analyses of lidar data time series was developed to investigate patterns of coastal terrain evolution, including the beach and dune systems. The diverse lidar-point data density, noise, and systematic errors were first quantified, and the results were used to compute a consistent series of high-resolution digital elevation models using spline-based approximation with optimized parameters. Raster-based statistical analysis was applied to the elevation-model time series to derive maps representing multiyear trends in spatial patterns of elevation change, to quantify dynamics at each cell using standard deviation maps, and to extract the core surface below which the elevation has never decreased. The methodology was applied to a North Carolina barrier island that was mapped by a sequence of 13 lidar surveys during the past decade, using several different lidar systems. Assessment of vertical differences between the lidar data sets using stable structures such as a road, was shown to be essential for correct quantification of coastal terrain change and its pattern. The analysis revealed the highly dynamic nature of foredunes, the trend toward inland sand transport, and the impact of anthropogenic sand disposal on that trend. DA - 2009/3// PY - 2009/3// DO - 10.2112/07-0976.1 VL - 25 IS - 2 SP - 507-514 SN - 1551-5036 KW - Coastal change KW - systematic error KW - barrier island KW - North Carolina KW - GRASS GIS ER - TY - JOUR TI - Numerical Modeling of Emulsified Oil Distribution in Heterogeneous Aquifers AU - Clayton, Matthew H. AU - Borden, Robert C. T2 - GROUND WATER AB - Abstract In situ anaerobic bioremediation using edible oil emulsions will be most effective if the oil droplets can be brought into close contact with the contaminant to be treated. However, uniformly distributing oil in heterogeneous aquifers can be difficult. The impact of injection conditions on emulsion distribution in a three‐dimensional heterogeneous aquifer is examined using MODFLOW and RT3D. Emulsion retention is simulated using a rate‐limited Langmuir isotherm. Volume and flow contact efficiency are shown to be functions of mass of oil injected, injection fluid volume, well spacing, and injection sequence. Regression equations are developed relating dimensionless scaling factors to expected contact efficiency for area treatment and barriers. Cleanup time for uncontacted zones is estimated using a mobile‐immobile zone modeling approach. DA - 2009/// PY - 2009/// DO - 10.1111/j.1745-6584.2008.00531.x VL - 47 IS - 2 SP - 246-258 SN - 1745-6584 ER - TY - JOUR TI - Improved flow-based travel time estimation method from point detector data for freeways AU - Vanajakshi, L.D. AU - Williams, Billy AU - Rilett, L.R. T2 - Journal of Transportation Engineering AB - Travel time is an important parameter in evaluating the operating efficiency of traffic networks, in assessing the performance of traffic management strategies, and as input to many intelligent transportation systems applications such as advanced traveler information systems. Travel time can be obtained directly from instrumented test vehicles, license plate matching, probe vehicles etc., or from indirect methods such as inductance loop detectors. Because of the widespread deployment of loop detectors, they are one of the most widely used inputs to travel time estimation techniques. There are different methods available to calculate the travel time from loop detector data, such as extrapolation of the point speed values, statistical methods, and models based on traffic flow theory. However, most of these methods fail during the transition period between the normal and congested flow conditions. The present study proposes several modifications to an existing traffic flow theory based model for travel time estimation on freeways, such that the model can estimate travel time for varying traffic flow conditions, including transition period, directly from the loop detector data. Field data collected from the I-35 freeway in San Antonio, Tex., USA, are used for illustrating the results. Automatic vehicle identification data collected from the same location are used for validating the results. Simulated data using CORSIM simulation software are also used for the validation of the model. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0733-947X(2009)135:1(26) VL - 135 IS - 1 SP - 26-36 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-57949084250&partnerID=MN8TOARS ER - TY - JOUR TI - Improved drought management of Falls Lake Reservoir: Role of multimodel streamflow forecasts in setting up restrictions AU - Golembesky, K. AU - Sankarasubramanian, A. AU - Devineni, N. T2 - Journal of Water Resources Planning and Management AB - Droughts, resulting from natural variability in supply and from increased demand due to urbanization, have severe economic implications on local and regional water supply systems. In the context of short-term (monthly to seasonal) water management, predicting these supply variations well in advance are essential in advocating appropriate conservation measures before the onset of drought. In this study, we utilized 3-month ahead probabilistic multimodel streamflow forecasts developed using climatic information—sea surface temperature conditions in the tropical Pacific, tropical Atlantic, and over the North Carolina coast—to invoke restrictions for Falls Lake Reservoir in the Neuse River Basin, N.C. Multimodel streamflow forecasts developed from two single models, a parametric regression approach and semiparametric resampling approach, are forced with a reservoir management model that takes ensembles to estimate the reliability of meeting the water quality and water supply releases and the end of the season target storage. The analyses show that the entire seasonal releases for water supply and water quality uses could be met purely based on the initial storages (100% reliability of supply), thereby limiting the use of forecasts. The study suggests that, by constraining the end of the season target storage conditions being met with high probability, the climate information based streamflow forecasts could be utilized for invoking restrictions during below-normal inflow years. Further, multimodel forecasts perform better in detecting the below-normal inflow conditions in comparison to single model forecasts by reducing false alarms and missed targets which could improve public confidence in utilizing climate forecasts for developing proactive water management strategies. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0733-9496(2009)135:3(188) VL - 135 IS - 3 SP - 188–197 ER - TY - JOUR TI - Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer AU - Hatzinger, Paul B. AU - Bohlke, John Karl AU - Sturchio, Neil C. AU - Gu, Baohua AU - Heraty, Linnea J. AU - Borden, Robert C. T2 - ENVIRONMENTAL CHEMISTRY AB - Environmental context. Perchlorate (ClO4–) and nitrate (NO3–) are common co-contaminants in groundwater, with both natural and anthropogenic sources. Each of these compounds is biodegradable, so in situ enhanced bioremediation is one alternative for treating them in groundwater. Because bacteria typically fractionate isotopes during biodegradation, stable isotope analysis is increasingly used to distinguish this process from transport or mixing-related decreases in contaminant concentrations. However, for this technique to be useful in the field to monitor bioremediation progress, isotope fractionation must be quantified under relevant environmental conditions. In the present study, we quantify the apparent in situ fractionation effects for stable isotopes in ClO4– (Cl and O) and NO3– (N and O) resulting from biodegradation in an aquifer. Abstract. An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiment, groundwater extracted from an upgradient well was pumped into an injection well located within the in situ oil barrier, and then groundwater samples were withdrawn for the next 30 h. After correction for dilution (using Br– as a conservative tracer of the injectate), perchlorate concentrations decreased by 78% and nitrate concentrations decreased by 82% during the initial 8.6 h after the injection. The observed ratio of fractionation effects of O and Cl isotopes in perchlorate (ϵ18O/ϵ37Cl) was 2.6, which is similar to that observed in the laboratory using pure cultures (2.5). Denitrification by indigenous bacteria fractionated O and N isotopes in nitrate at a ratio of ~0.8 (ϵ18O/ϵ15N), which is within the range of values reported previously for denitrification. However, the magnitudes of the individual apparent in situ isotope fractionation effects for perchlorate and nitrate were appreciably smaller than those reported in homogeneous closed systems (0.2 to 0.6 times), even after adjustment for dilution. These results indicate that (1) isotope fractionation factor ratios (ϵ18O/ϵ37Cl, ϵ18O/ϵ15N) derived from homogeneous laboratory systems (e.g. pure culture studies) can be used qualitatively to confirm the occurrence of in situ biodegradation of both perchlorate and nitrate, but (2) the magnitudes of the individual apparent ϵ values cannot be used quantitatively to estimate the in situ extent of biodegradation of either anion. DA - 2009/// PY - 2009/// DO - 10.1071/EN09008 VL - 6 IS - 1 SP - 44-52 SN - 1448-2517 ER - TY - JOUR TI - Damaged masonry walls in two-way bending retrofitted with vertical FRP strips AU - Willis, C. R. AU - Yang, Q. AU - Seracino, R. AU - Griffith, M. C. T2 - Construction & Building Materials AB - Unreinforced masonry (hereafter termed ‘masonry’) structures comprise a significant proportion of the building stock in many countries worldwide, however their walls do not behave well under out-of-plane loading, such as that experienced during seismic events. Consequently, many existing masonry structures require some form of retrofit to comply with existing codes. As part of ongoing research at The University of Adelaide on the out-of-plane bending behaviour of masonry walls, eight full-scale walls (with window openings) were tested under reversed-cyclic loading. Four of the severely damaged walls were subsequently retrofitted using externally bonded (EB) (three walls) and near-surface mounted (NSM) (one wall) fibre-reinforced polymer (FRP) strips and tested again to quantify the increase in strength and ductility relative to the original capacities. A debonding mechanism not yet quantified for retrofitted masonry walls was observed and identified as displacement induced (DI) debonding. It is a result of a differential out-of-plane displacement at either side of a crack in the wall. NSM strips are more susceptible due to their orientation. This paper presents the results of the wall tests along with detailed accounts of the wall failure modes. DA - 2009/// PY - 2009/// DO - 10.1016/j.conbuildmat.2007.09.007 VL - 23 IS - 4 SP - 1591-1604 ER - TY - JOUR TI - Celebrating a milestone in Population Balance Modeling AU - Nopens, Ingmar AU - Briesen, Heiko AU - Ducoste, Joel T2 - CHEMICAL ENGINEERING SCIENCE AB - Crystallization is one of the most important unit operations used for the separation and purification of crystalline solid products. Appropriate design and control of the crystallization process is paramount to produce crystalline products with tailor-made-properties. This paper provides an overview of selected recent developments in the modelling, monitoring and control of crystallization processes. We consider the topics discussed in this review to be enabling technologies for the development of the next generation of crystallization processes with significantly improved predictability, robustness and controllability. DA - 2009/2/16/ PY - 2009/2/16/ DO - 10.1016/j.ces.2009.01.004 VL - 64 IS - 4 SP - 627-627 SN - 0009-2509 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-58949087904&partnerID=MN8TOARS ER - TY - JOUR TI - Behavior of high-performance steel as shear reinforcement for concrete beams AU - Sumpter, M. S. AU - Rizkalla, S. H. AU - Zia, P. T2 - ACI Structural Journal DA - 2009/// PY - 2009/// VL - 106 IS - 2 SP - 171-177 ER - TY - JOUR TI - Wave propagation in nonlinear one-dimensional soil model AU - Ahn, J. AU - Biscontin, G. AU - Roesset, J. M. T2 - INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS AB - Abstract The objective of the research conducted by the authors is to explore the feasibility of determining reliable in situ values of shear modulus as a function of strain. In this paper the meaning of the material stiffness obtained from impact and harmonic excitation tests on a surface slab is discussed. A one‐dimensional discrete model with the nonlinear material stiffness is used for this purpose. When a static load is applied followed by an impact excitation, if the amplitude of the impact is very small, the measured wave velocity using the cross‐correlation indicates the wave velocity calculated from the tangent modulus corresponding to the state of stress caused by the applied static load. The duration of the impact affects the magnitude of the displacement and the particle velocity but has very little effect on the estimation of the wave velocity for the magnitudes considered herein. When a harmonic excitation is applied, the cross‐correlation of the time histories at different depths estimates a wave velocity close to the one calculated from the secant modulus in the stress–strain loop under steady‐state condition. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2009/3// PY - 2009/3// DO - 10.1002/nag.724 VL - 33 IS - 4 SP - 487-509 SN - 1096-9853 KW - wave propagation KW - nonlinear KW - impact excitation KW - harmonic excitation ER - TY - JOUR TI - Synthesis of sign deterioration rates across the United States AU - Immaneni, V. P. K. AU - Hummer, J. E. AU - Rasdorf, W. J. AU - Harris, E. A. AU - Yeom, C. T2 - Journal of Transportation Engineering AB - In response to minimum retroreflectivity standards, transportation departments are implementing sign asset management strategies, which rely upon knowledge of how retroreflectivity decreases as signs weather and age. To provide this knowledge, the writers field measured over 1,000 in-service signs in scattered North Carolina Department of Transportation (NCDOT) divisions, collecting age and retroreflectivity data for white, yellow, red, and green signs and for ASTM sheeting Types I and III. Data from this study and data from five similar U.S. efforts were analyzed using regression to identify the best available deterioration rate estimates, finding that retroreflectivity minimums are usually reached eight to 15years after installation. Initial results indicated that the best-fitting relationships between retroreflectivity and age were generally linear and that these models were significant despite having low R2 values. Because age did not explain some of the variance, the writers reevaluated their data including NCDOT divisions as a factor, finding that sign deterioration differed significantly by division, indicating that handling practices, manufacturing differences, and environmental exposure may be key deterioration model factors that merit future study. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0733-947X(2009)135:3(94) VL - 135 IS - 3 SP - 94-103 ER - TY - JOUR TI - Seismic behavior of flexural dominated reinforced concrete bridge columns at low temperatures AU - Montejo, L. A. AU - Kowalsky, M. J. AU - Hassan, T. T2 - Journal of Cold Regions Engineering AB - This paper presents the results from Phase II of an experimental study on the behavior of reinforced concrete bridge columns in cold seismicly active regions. Six half-scale circular reinforced concrete columns, designed to be flexural dominated, were tested under reversed cyclic loading while subjected to temperatures ranging from −36°C(−33°F) to 22°C(72°F). Four of the units tested were reinforced concrete filled steel tube (RCFST) columns and the other two were ordinary reinforced concrete columns. Results obtained reiterated the observations made in Phase I, which is that low temperatures cause an increase in the flexural strength and initial stiffness as well as a reduction in the spread of plasticity and displacement capacity of the column. Another important observation made was that the plastic hinge length is drastically reduced in the RCFST units compromising the displacement capacity of this type of column even at room temperature conditions. Current predictive models were revised and modified to account for the low-temperature effect. DA - 2009/// PY - 2009/// DO - 10.1061/(ASCE)0887-381X(2009)23:1(18) VL - 23 IS - 1 SP - 18-42 ER - TY - JOUR TI - IT Issues for the management of high-quantity, low-cost assets AU - Rasdorf, W. AU - Hummer, J. E. AU - Harris, E. A. AU - Sitzabee, W. E. T2 - Journal of Computing in Civil Engineering AB - Transportation infrastructure asset management efforts have historically focused on collecting data on assets with high capital costs, such as bridges and pavements. Road signs and pavement markings, on the other hand, are high quantity, low capital cost assets but are also critical elements of the transportation infrastructure. These high quantity assets serve a critical function, safety, and thus they are receiving attention. Mandated by law, the Federal Highway Administration has been working to establish minimum retroreflectivity standards for signs and pavement markings. This paper seeks to address the information technology (IT) problems that emerge when developing an overall asset management system for high-quantity, low-cost assets. These IT problems include asset identification, asset location, data availability, data fragmentation, and automated data collection. A discussion of the issues related to these problems is presented to promote awareness of the myriad problems that do exist and to facilitate the development of more comprehensive systems to manage the automation of infrastructure asset management systems. DA - 2009/// PY - 2009/// DO - 10.1061/(asce)0887-3801(2009)23:2(91) VL - 23 IS - 2 SP - 91-99 ER - TY - JOUR TI - Flexural behavior of prestressed FRP tubular bridge deck AU - Wu, Zhenhua AU - Mirmiran, Amir AU - Zhu, Zhenyu AU - Swanson, James T2 - COMPOSITES PART B-ENGINEERING AB - An experimental and analytical study was undertaken to assess the flexural behavior of a new fiber reinforced polymer (FRP) deck system. The deck consists of a series of pultruted FRP tubes, post-tensioned in between each two stringers. Seven pure compression tests and eleven flexural tests were carried out to investigate the effect of tube size, bonding condition, post-tensioning, and supporting conditions. Finite element modeling of compression and flexural specimens was carried out to determine the effect of tube interface friction, bond and geometry restraints. The study showed feasibility of the new deck system for bridges with closely spaced stringers, where lack of two-way panel action is not a primary concern. Failure modes were also identified for these types of deck systems. Longer span decks generally failed in bending, whereas shorter span decks suffered from local shear failure at the corner of the tubes. Prestressing provided redundancy and reserved strength to the deck system. DA - 2009/3// PY - 2009/3// DO - 10.1016/j.compositesb.2008.11.001 VL - 40 IS - 2 SP - 125-133 SN - 1879-1069 KW - Glass fibers KW - Delamination KW - Finite element analysis KW - Mechanical testing KW - Pultrusion ER - TY - JOUR TI - Cleaving of solid single mode polymer optical fiber for strain sensor applications AU - Abdi, O. AU - Wong, K. C. AU - Hassan, T. AU - Peters, K. J. AU - Kowalsky, M. J. T2 - OPTICS COMMUNICATIONS AB - Abstract Single mode polymer optical fibers (smPOFs) can be applied for measuring large strains in numerous applications, such as civil engineering infrastructure assessment and health monitoring. Because of the large light attenuation of solid smPOFs, small lengths of the fiber would need to be coupled to silica optical fibers (SOFs) for practical applications of the smPOF as a strain sensor. This coupling requires smooth cleaving of the smPOFs. In this work, several cleaving techniques previously demonstrated to provide smooth cross-sections of multimode POFs were applied to the smPOF. From these techniques, hot-knife cutting was determined to be a feasible method for cleaving when the blade was heated to 80 °C and the smPOF heated in the range of 30 °C to 40 °C. In addition, focused ion beam machining which produces high-precision cleaves of the solid smPOF cross-section, was performed to set a bench mark and thus evaluate the quality of cleaving from other methods used in this study. DA - 2009/3/1/ PY - 2009/3/1/ DO - 10.1016/j.optcom.2008.11.046 VL - 282 IS - 5 SP - 856-861 SN - 1873-0310 KW - Cleaving KW - Polymer optical fiber KW - Single mode KW - Strain KW - Sensor ER - TY - JOUR TI - Is It Better To Burn or Bury Waste for Clean Electricity Generation? AU - Kaplan, P. Ozge AU - DeCarolis, Joseph AU - Thorneloe, Susan T2 - Environmental Science & Technology AB - The use of municipal solid waste (MSW) to generate electricity through landfill-gas-to-energy (LFGTE) and waste-to-energy (WTE) projects represents roughly 14% of U.S. nonhydro renewable electricity generation. Although various aspects of LFGTE and WTE have been analyzed in the literature, this paper is the first to present a comprehensive set of life-cycle emission factors per unit of electricity generated for these energy recovery options. In addition, sensitivity analysis is conducted on key inputs (e.g., efficiency of the WTE plant landfill gas management schedules, oxidation rate, and waste composition) to quantify the variability in the resultant life-cycle emissions estimates. While methane from landfills results from the anaerobic breakdown of biogenic materials, the energy derived from WTE results from the combustion of both biogenic and fossil materials. The greenhouse gas emissions for WTE ranges from 0.4 to 1.5 MTCO2e/MWh, whereas the most agressive LFGTE scenerio results in 2.3 MTCO2e/MWh. WTE also produces lower NO(x) emissions than LFGTE, whereas SO(x) emissions depend on the specific configurations of WTE and LFGTE. DA - 2009/3/15/ PY - 2009/3/15/ DO - 10.1021/es802395e VL - 43 IS - 6 SP - 1711-1717 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es802395e DB - Crossref ER - TY - JOUR TI - Assessing methods for comparing emissions from gasoline and diesel light-duty vehicles based on microscale measurements AU - Coelho, Margarida C. AU - Frey, H. Christopher AU - Rouphail, Nagui M. AU - Zhai, Haibo AU - Pelkmans, Luc T2 - TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT AB - This paper assess whether a real-world second-by-second methodology that integrates vehicle activity and emissions rates for light-duty gasoline vehicles can be extended to diesel vehicles. Secondly it compares fuel use and emission rates between gasoline and diesel light-duty vehicles. To evaluate the methodology, real-world field data from two light-duty diesel vehicles are used. Vehicle specific power, a function of vehicle speed, acceleration, and road grade, is evaluated with respect to ability to explain variation in emissions rates. Vehicle specific power has been used previously to define activity-based modes and to quantify variation in fuel use and emission rates of gasoline vehicles taking into account idle, acceleration, cruise, and deceleration. The fuel use and emission rates for light-duty diesel vehicles can also be explained using vehicle specific power -based modes. Thus, the methodology enables direct comparisons for different vehicle fuels and technologies. Furthermore, the method can be used to estimate average fuel use and emission rates for a wide variety of driving cycles. DA - 2009/3// PY - 2009/3// DO - 10.1016/j.trd.2008.11.005 VL - 14 IS - 2 SP - 91-99 SN - 1361-9209 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-58849133274&partnerID=MN8TOARS KW - Diesel vehicles KW - Emissions KW - On-board measurements KW - Vehicle specific power ER - TY - JOUR TI - Analysis of coupled model uncertainties in source-to-dose modeling of human exposures to ambient air pollution: A PM2.5 case study AU - Oezkaynak, Haluk AU - Frey, H. Christopher AU - Burke, Janet AU - Pinder, Robert W. T2 - ATMOSPHERIC ENVIRONMENT AB - Quantitative assessment of human exposures and health effects due to air pollution involve detailed characterization of impacts of air quality on exposure and dose. A key challenge is to integrate these three components on a consistent spatial and temporal basis taking into account linkages and feedbacks. The current state-of-practice for such assessments is to exercise emission, meteorology, air quality, exposure, and dose models separately, and to link them together by using the output of one model as input to the subsequent downstream model. Quantification of variability and uncertainty has been an important topic in the exposure assessment community for a number of years. Variability refers to differences in the value of a quantity (e.g., exposure) over time, space, or among individuals. Uncertainty refers to lack of knowledge regarding the true value of a quantity. An emerging challenge is how to quantify variability and uncertainty in integrated assessments over the source-to-dose continuum by considering contributions from individual as well as linked components. For a case study of fine particulate matter (PM2.5) in North Carolina during July 2002, we characterize variability and uncertainty associated with each of the individual concentration, exposure and dose models that are linked, and use a conceptual framework to quantify and evaluate the implications of coupled model uncertainties. We find that the resulting overall uncertainties due to combined effects of both variability and uncertainty are smaller (usually by a factor of 3–4) than the crudely multiplied model-specific overall uncertainty ratios. Future research will need to examine the impact of potential dependencies among the model components by conducting a truly coupled modeling analysis. DA - 2009/3// PY - 2009/3// DO - 10.1016/j.atmosenv.2008.12.008 VL - 43 IS - 9 SP - 1641-1649 SN - 1352-2310 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-59649124689&partnerID=MN8TOARS KW - Air quality model KW - Exposure model KW - Particulate matter KW - Variability KW - Uncertainty ER - TY - JOUR TI - A genetic algorithm-based procedure for 3D source identification at the Borden emplacement site AU - Jin, Xin AU - Mahinthakumar, G. (Kumar) AU - Zechman, Emily M. AU - Ranjithan, Ranji S. T2 - Journal of Hydroinformatics AB - Finding the location and concentration of groundwater contaminant sources typically requires the solution of an inverse problem. A parallel hybrid optimization framework that uses genetic algorithms (GA) coupled with local search approaches (GA-LS) has been developed previously to solve groundwater inverse problems. In this study, the identification of an emplaced source at the Borden site is carried out as a test problem using this optimization framework by using a Real Genetic Algorithm (RGA) as the GA approach and a Nelder–Mead simplex as the LS approach. The RGA results showed that the minimum objective function did not always correspond to the minimum solution error, indicating a possible non-uniqueness issue. To address this problem, a procedure to identify maximally different starting points for LS is introduced. When measurement or model errors are non-existent or minimal it is shown that one of these starting points leads to the true solution. When these errors are significant, this procedure leads to multiple possible solutions that could be used as a basis for further investigation. Metrics of mean and standard deviation of objective function values was adopted to evaluate the possible solutions. A new selection criterion based on these metrics is suggested to find the best alternative. This suggests that this alternative generation procedure could be used to address the non-uniqueness of similar inverse problems. A potential limitation of this approach is the application to a wide class of problems, as verification has not been performed with a large number of test cases or other inverse problems. This remains a topic for future work. DA - 2009/1// PY - 2009/1// DO - 10.2166/hydro.2009.002 VL - 11 IS - 1 SP - 51-64 LA - en OP - SN - 1464-7141 1465-1734 UR - http://dx.doi.org/10.2166/hydro.2009.002 DB - Crossref KW - environmental forensics KW - evolutionary computation KW - groundwater source identification KW - inverse problems ER - TY - RPRT TI - Pavement marking performance analysis AU - Rasdorf, W. AU - Hummer, J. E. AU - Zhang, G. AU - Sitzabee, W. E. A3 - Raleigh, N.C.: North Carolina Department of Transportation DA - 2009/// PY - 2009/// PB - Raleigh, N.C.: North Carolina Department of Transportation ER - TY - JOUR TI - Multiple approaches to assess filamentous bacterial growth in activated sludge under different carbon source conditions AU - Gulez, G. AU - Reyes, F. L., III T2 - JOURNAL OF APPLIED MICROBIOLOGY AB - To compare molecular and microscopic approaches in determining which filamentous bacteria grow in activated sludge reactors when different carbon sources and different activated sludge mixed liquor inocula are used.Microscopic and molecular (Denaturing Gradient Gel Electrophoresis and Fluorescent In Situ Hybridization) techniques were used to determine which filamentous bacteria became dominant in lab scale reactors treating wastewater composed of different carbon sources. Molecular analysis indicated the presence of Sphaerotilus natans and Thiothrix-related organisms. Microscopy indicated the presence of Nostocoida limicola in some reactors. Sludge volume index increased as filament abundance increased. The detection level of DGGE analysis increased when the abundance levels of the filaments were high.Simultaneous application of traditional and molecular methods was effective, and highlighted the advantages and limitations of each method. Readily biodegradable substances favoured the growth of specific filaments in a mixed liquor environment. The origin of inoculum influenced which specific filamentous bacteria grew.The study shows the potential problems when using particular techniques, and highlights the need for multiple approaches when studying filaments. The study also provides more information on which filaments will grow under different carbon source conditions for a given inoculum. DA - 2009/2// PY - 2009/2// DO - 10.1111/j.1365-2672.2008.04049.x VL - 106 IS - 2 SP - 682-691 SN - 1365-2672 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-58549115306&partnerID=MN8TOARS KW - activated sludge KW - carbon source KW - DGGE KW - filamentous bulking KW - FISH ER -