@article{tong_mathur_kang_yu_schere_pouliot_2009, title={Vegetation exposure to ozone over the continental United States: Assessment of exposure indices by the Eta-CMAQ air quality forecast model}, volume={43}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2008.09.084}, abstractNote={The main use of air quality forecast (AQF) models is to predict ozone (O3) exceedances of the primary O3 standard for informing the public of potential health concerns. This study presents the first evaluation of the performance of the Eta-CMAQ air quality forecast model to predict a variety of widely used seasonal mean and cumulative O3 exposure indices associated with vegetation using the U.S. AIRNow O3 observations. These exposure indices include two concentration-based O3 indices, M7 and M12 (the seasonal means of daytime 7-h and 12-h O3 concentrations, respectively), and three cumulative exposure-based indices, SUM06 (the sum of all hourly O3 concentrations ≥ 0.06 ppm), W126 (hourly concentrations weighed by a sigmoidal weighting function), and AOT40 (O3 concentrations accumulated over a threshold of 40 ppb during daylight hours). During a three-month simulation (July–September 2005), the model over predicted the M7 and M12 values by 8–9 ppb, or a NMB value of 19% and a NME value of 21%. The model predicts a central belt of high O3 extending from Southern California to Middle Atlantic where the seasonal means, M7 and M12 (the seasonal means of daytime 7-h and 12-h O3 concentrations), are higher than 50 ppbv. In contrast, the model is less capable of reproducing the observed cumulative indices. For AOT40, SUM06 and W126, the NMB and NME values are two- to three-fold of that for M7, M12 or peak 8-h O3 concentrations. The AOT40 values range from 2 to 33 ppm h by the model and from 1 to 40 ppm h by the monitors. There is a significantly higher AOT40 value experienced in the United States in comparison to Europe. The domain-wide mean SUM06 value is 14.4 ppm h, which is about 30% higher than W126, and 40% higher than AOT40 calculated from the same 3-month hourly O3 data. This suggests that SUM06 and W126 represent a more stringent standard than AOT40 if either the SUM06 or the W126 was used as a secondary O3 standard. Although CMAQ considerably over predicts SUM06 and W126 values at the low end, the model under predicts the extreme high exposure values (>50 ppm h). Most of these extreme high values are found at inland California sites. Based on our analysis, further improvement of the model is needed to better capture cumulative exposure indices.}, number={3}, journal={ATMOSPHERIC ENVIRONMENT}, author={Tong, Daniel Q. and Mathur, Rohit and Kang, Daiwen and Yu, Shaocai and Schere, Kenneth L. and Pouliot, George}, year={2009}, month={Jan}, pages={724–733} }
 @article{rayner_kang_hinkle_hong_lucovsky_2004, title={Chemical phase separation in Zr silicate alloys: a spectroscopic study distinguishing between chemical phase separation with different degree of micro- and nano-crystallinity}, volume={72}, ISSN={["1873-5568"]}, DOI={10.1016/j.mee.2004.01.008}, abstractNote={Chemical phase separation at processing temperatures is an important issue for integration of Zr and Hf silicates alloys into advanced CMOS devices. Chemical phase separation into ZrO2 and SiO2 has been detected by different spectroscopic techniques, including Fourier transform infrared, X-ray photoelectron, and X-ray absorption spectroscopy, as well as X-ray diffraction and high resolution transmission electron microscopy imaging as well. Comparisons between techniques for Zr silicates identify an unambiguous approach to distinguishing between chemical phase separation with different degrees of micro- and nano-crystallinity. This is important since all modes of chemical separation degrade dielectric properties required for high-K applications.}, number={1-4}, journal={MICROELECTRONIC ENGINEERING}, author={Rayner, GB and Kang, D and Hinkle, CL and Hong, JG and Lucovsky, G}, year={2004}, month={Apr}, pages={304–309} }
 @article{kang_aneja_mathur_ray_2004, title={Observed and modeled VOC chemistry under high VOC/NOx conditions in the Southeast United States national parks}, volume={38}, ISSN={["1352-2310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-4043070651&partnerID=MN8TOARS}, DOI={10.1016/j.atmosenv.2004.05.054}, abstractNote={In airsheds that contain high volatile organic compounds (VOCs) and low NOx (=NO+NO2) concentrations, ozone (O3) production may be significantly suppressed by NOx reactions that lead to the formation of organic nitrates. O3 and its precursors (VOCs and NOx) ambient levels simulated using a regional-scale photochemical model, called Multiscale Air Quality Simulation Platform, are analyzed and compared to observed data from three southeast United States national parks.}, number={29}, journal={ATMOSPHERIC ENVIRONMENT}, author={Kang, DW and Aneja, VP and Mathur, R and Ray, JD}, year={2004}, month={Sep}, pages={4969–4974} }
 @article{das_kang_aneja_lonneman_cook_wesely_2003, title={Measurements of hydrocarbon air-surface exchange rates over maize}, volume={37}, ISSN={["1352-2310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037403349&partnerID=MN8TOARS}, DOI={10.1016/S1352-2310(03)00076-1}, abstractNote={Vertical gradients of volatile organic compounds (VOCs) were measured over a maize (Zea mays) field, in its early growth period, during May 1995, in the Lower Coastal Plains of North Carolina. These measurements were combined with micrometeorological flux measurements to determine emission flux measurements for various VOCs. This measurement program was part of project NOVA (Natural emissions of Oxidant precursors: Validation of techniques and Assessment) to estimate the flux of VOCs. Average emissions of VOCs (and standard error) was estimated to be 4900±700 μg/m2/h out of which emission for methanol averaged (3450±420) μg/m2/h. A methanol emission rate of 35 μg/g/h was calculated for maize from the estimated emission of methanol and biomass density for the site.}, number={16}, journal={ATMOSPHERIC ENVIRONMENT}, author={Das, M and Kang, DW and Aneja, VP and Lonneman, W and Cook, DR and Wesely, ML}, year={2003}, month={May}, pages={2269–2277} }
 @article{kang_aneja_mathur_ray_2003, title={Nonmethane hydrocarbons and ozone in three rural southeast United States national parks: A model sensitivity analysis and comparison to measurements}, volume={108}, ISSN={["2169-8996"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0347692888&partnerID=MN8TOARS}, DOI={10.1029/2002jd003054}, abstractNote={A detailed modeling analysis is conducted focusing on nonmethane hydrocarbons and ozone in three southeast United States national parks for a 15‐day time period (14–29 July 1995) characterized by high O3 surface concentrations. The three national parks are Smoky Mountains National Park (GRSM), Mammoth Cave National Park (MACA), and Shenandoah National Park (SHEN), Big Meadows. A base emission scenario and eight variant predictions are analyzed, and predictions are compared with data observed at the three locations for the same time period. Model‐predicted concentrations are higher than observed values for O3 (with a cutoff of 40 ppbv) by 3.0% at GRSM, 19.1% at MACA, and 9.0% at SHEN (mean normalized bias error). They are very similar to observations for overall mean ozone concentrations at GRSM and SHEN. They generally agree (the same order of magnitude) with observed values for lumped paraffin compounds but are an order of magnitude lower for other species (isoprene, ethene, surrogate olefin, surrogate toluene, and surrogate xylene). Model sensitivity analyses here indicate that each location differs in terms of volatile organic compound (VOC) capacity to produce O3, but a maximum VOC capacity point (MVCP) exists at all locations that changes the influence of VOCs on O3 from net production to production suppression. Analysis of individual model processes shows that more than 50% of daytime O3 concentrations at the high‐elevation rural locations (GRSM and SHEN) are transported from other areas; local chemistry is the second largest O3 contributor. At the low‐elevation location (MACA), about 80% of daytime O3 is produced by local chemistry and 20% is transported from other areas. Local emissions (67–95%) are predominantly responsible for VOCs at all locations, the rest coming from transport. Chemistry processes are responsible for about 50% removal of VOCs for all locations; less than 10% are lost to surface deposition and the rest are exported to other areas. Metrics, such as VOC potential for O3 production (VPOP), which links the chemistry processes of both O3 and VOCs and MVCP, are devised to measure the different characteristics of O3 production and VOCs. The values of the defined metrics are mapped for the entire modeling domain. Implications of this model exercise in understanding O3 production are analyzed and discussed. Even though this study was focused on three United States national parks, the research results and conclusions may be applicable to other or to similar rural environments in the southeast United States.}, number={D19}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Kang, DW and Aneja, VP and Mathur, R and Ray, JD}, year={2003}, month={Oct} }
 @article{mohamed_kang_aneja_2002, title={Volatile organic compounds in some urban locations in United States}, volume={47}, ISSN={["0045-6535"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036595008&partnerID=MN8TOARS}, DOI={10.1016/S0045-6535(02)00107-8}, abstractNote={Volatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air samples were collected and analyzed in accordance with US Environmental Protection Agency-approved methods. The target compounds most commonly found were benzene, toluene, xylene and ethylbenzene. These aromatic compounds were highly correlated and proportionally related in a manner suggesting that the primary contributors were mobile sources in all the urban locations studied. Concentrations of total hydrocarbons ranged between 1.39 and 11.93 parts per billion, by volume (ppbv). Ambient air levels of halogenated hydrocarbons appeared to exhibit unique spatial variations, and no single factor seemed to explain trends for this group of compounds. The highest halogenated hydrocarbon concentrations ranged from 0.24 ppbv for methylene chloride to 1.22 ppbv for chloromethane. At participating urban locations for the year of data considered, levels of carbonyls were higher than the level of the other organic compound groups, suggesting that emissions from motor vehicles and photochemical reactions strongly influence ambient air concentrations of carbonyls. Of the most prevalent carbonyls, formaldehyde and acetaldehyde were the dominant compounds, ranging from 1.5-7.4 ppbv for formaldehyde, to 0.8-2.7 ppbv for acetaldehyde.}, number={8}, journal={CHEMOSPHERE}, author={Mohamed, MF and Kang, DW and Aneja, VP}, year={2002}, month={Jun}, pages={863–882} }
 @article{lucovsky_rayner_kang_appel_johnson_zhang_sayers_ade_whitten_2001, title={Electronic structure of noncrystalline transition metal silicate and aluminate alloys}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1404997}, abstractNote={A localized molecular orbital description (LMO) for the electronic states of transition metal (TM) noncrystalline silicate and aluminate alloys establishes that the lowest conduction band states are derived from d states of TM atoms. The relative energies of these states are in agreement with the LMO approach, and have been measured by x-ray absorption spectroscopy for ZrO2–SiO2 alloys, and deduced from an interpretation of capacitance–voltage and current–voltage data for capacitors with Al2O3–Ta2O5 alloy dielectrics. The LMO model yields a scaling relationship for band offset energies providing a guideline for selection of gate dielectrics for advanced Si devices.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Lucovsky, G and Rayner, GB and Kang, D and Appel, G and Johnson, RS and Zhang, Y and Sayers, DE and Ade, H and Whitten, JL}, year={2001}, month={Sep}, pages={1775–1777} }
 @article{kang_zhirnov_sanwald_hren_cuomo_2001, title={Field emission from ultrathin coatings of AlN on Mo emitters}, volume={19}, ISSN={["2166-2746"]}, DOI={10.1116/1.1340669}, abstractNote={Experiments characterizing both the physics of emission and the performance of Mo tips coated with ultrathin film of AlN were conducted. Ultrathin films of AlN with thicknesses ranging from 7 to 21 nm in 1.5 nm increments were deposited onto Mo tips by magnetron sputtering. In situ field emission measurements were performed after each deposition step. Tip radius, thickness, and morphology of AlN coating were characterized with the transmission electron microscopy. The effect of the thickness of AlN on emission was determined using a Fowler–Nordheim analysis. Various surface treatment effects were studied and measurements of maximum current and emission stability were performed, e.g., maximum current from a single Mo tip with 15 nm of AlN coating was 52 μA.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Kang, D and Zhirnov, VV and Sanwald, RC and Hren, JJ and Cuomo, JJ}, year={2001}, pages={50–54} }
 @article{kang_aneja_zika_farmer_ray_2001, title={Nonmethane hydrocarbons in the rural southeast United States national parks}, volume={106}, ISSN={["0747-7309"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035081992&partnerID=MN8TOARS}, DOI={10.1029/2000JD900607}, abstractNote={Measurements of volatile organic compounds (VOCs) were made at three rural sites in the southeast U.S. national parks: Mammoth Cave National Park, Kentucky; Cove Mountain, Great Smoky Mountains National Park, Tennessee; and Big Meadows, Shenandoah National Park, Virginia. In 1995 the three locations were sampling sites for the Southern Oxidants Study (SOS) Nashville Intensive, and the measurements of VOCs for Shenandoah were also made under contract with the National Park Service. Starting in 1996, the National Park Service added the other two parks to the monitoring contract. Hydrocarbon measurements made during June through September for the years 1995, 1996, and 1997 were analyzed in this study. Source classification techniques based on correlation coefficient, chemical reactivity, and ratioing were developed and applied to these data. The results show that anthropogenic VOCs from automobile exhaust appeared to be dominant at Mammoth Cave National Park, and at Cove Mountain, Great Smoky Mountains National Park, but other sources were also important at Big Meadows, Shenandoah National Park. Correlation and ratio analysis based on chemical reactivity provides a basis for source‐receptor relationship. The most abundant ambient VOCs varied both in concentration and order depending on park and year, but the following VOCs appeared on the top 10 list for all three sites: isoprene (6.3 to 18.4 ppbv), propane (2.1 to 12.9 ppbv), isopentane (1.3 to 5.7 ppbv), and toluene (1.0 to 7.2 ppbv). Isoprene is naturally emitted by vegetation, and the others are produced mainly by fossil fuel combustion and industrial processes. Propylene‐equivalent concentrations were calculated to account for differences in reaction rates between the hydroxyl radical and individual hydrocarbons, and to thereby estimate their relative contributions to ozone formation.}, number={D3}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Kang, DW and Aneja, VP and Zika, RG and Farmer, C and Ray, JD}, year={2001}, month={Feb}, pages={3133–3155} }