TY - RPRT TI - Atmospheric Pressure Plasma-Electrospinning Hybrid Nanofiber Mat Production AU - Zhang, Xiangwu AU - McCord, Marian G. AU - Bourham, Mohamed A. DA - 2011/// PY - 2011/// M3 - Final Technical Report ER - TY - RPRT TI - Enhanced Dye Adhesion on Cotton Fabric Using Atmospheric Pressure Plasmas AU - McCord, Marian AU - Bourham, Mohamed A3 - HanesBrand Inc DA - 2011/12/5/ PY - 2011/12/5/ M3 - Final Technical Report PB - HanesBrand Inc ER - TY - JOUR TI - Mechanical properties of Y2Ti2O7 AU - He, L.F. AU - Shirahata, J. AU - Nakayama, T. AU - Suzuki, T. AU - Suematsu, H. AU - Ihara, I. AU - Bao, Y.W. AU - Komatsu, T. AU - Niihara, K. T2 - Scripta Materialia AB - The mechanical properties of Y2Ti2O7 ceramics have been systematically characterized. Y2Ti2O7 shows higher hardness (12.1 GPa) than Y2O3 and TiO2. The Young’s modulus of Y2Ti2O7 (262 GPa) is close to that of TiO2 and 50% higher than that of Y2O3. The fracture toughness (1.9 MPa m1/2) and bending strength (206 MPa) are comparable with those of Y2O3 but half those of TiO2. The indentation size effect on the hardness in nanoindentation tests is discussed based on the Nix–Gao model. DA - 2011/// PY - 2011/// DO - 10.1016/j.scriptamat.2010.11.042 VL - 64 IS - 6 SP - 548-551 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78651300311&partnerID=MN8TOARS KW - Y2Ti2O7 KW - Mechanical properties KW - Hardness KW - Elastic behavior KW - Nanoindentation ER - TY - JOUR TI - Mechanical properties and bioactivity of β-Ca 2SiO 4 ceramics synthesized by spark plasma sintering AU - Zhong, H. AU - Wang, L. AU - Fan, Y. AU - He, L. AU - Lin, K. AU - Jiang, W. AU - Chang, J. AU - Chen, L. T2 - Ceramics International AB - Bioactive beta-dicalcium silicate ceramics (β-Ca2SiO4) were fabricated by spark plasma sintering (SPS). The relative density of as-prepared β-Ca2SiO4 ceramics reached 98.1% when sintered at 1150 °C, leading to great improvement in bending strength (293 MPa), almost 10 times higher than that of the specimen prepared by conventional pressureless sintering (PLS). High fracture toughness (3.0 MPa m1/2) and Vickers hardness (5.8 GPa) of β-Ca2SiO4 ceramics were also achieved by SPS at 1150 °C. The simulated body fluid (SBF) results showed that β-Ca2SiO4 ceramics had a good in vitro bioactivity to induce hydraxyapatite (HAp) formation on their surface, which suggests that β-Ca2SiO4 ceramics are promising candidates for load-bearing bone implant materials. DA - 2011/// PY - 2011/// DO - 10.1016/j.ceramint.2011.03.037 VL - 37 IS - 7 SP - 2459-2465 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79960328263&partnerID=MN8TOARS KW - Beta-dicalium silicate ceramics KW - Mechanical properties KW - Bioactivity KW - Spark plasma sintering ER - TY - JOUR TI - Effect of Ti dopant on the mechanical properties and oxidation behavior of Zr 2[Al(Si)] 4C 5 ceramics AU - Lu, X. AU - Xiang, H. AU - He, L.-F. AU - Sun, L. AU - Zhou, Y. T2 - Journal of the American Ceramic Society AB - Ti-doped Zr2[Al(Si)]4C5 solid solutions were prepared by an in situ hot-pressing method and its effect on the mechanical properties and high-temperature oxidation behavior were investigated. The solid solutions show comparable hardness, strength, and fracture toughness with Zr2[Al(Si)]4C5 except modulus, which decreases with Ti dopant content. The stiffness is maintained up to 1600°C, which derives from the clean grain boundaries without glassy phases. The oxidation resistance of [Zr1−x(Ti)x]2[Al(Si)]4C5 solid solutions at 1000°–1300°C is improved remarkably. The improved oxidation resistance is mostly due to the formation of a more protective oxide scale consisting of (Zr,Ti)O2, Al2O3, and mullite. DA - 2011/// PY - 2011/// DO - 10.1111/j.1551-2916.2010.04300.x VL - 94 IS - 6 SP - 1872-1877 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79958145065&partnerID=MN8TOARS ER - TY - JOUR TI - Fabrication and characterization of tricalcium silicate bioceramics with high mechanical properties by spark plasma sintering AU - Zhong, H. AU - Wang, L. AU - He, L. AU - Jiang, W. AU - Zhai, W. AU - Lin, K. AU - Chen, L. AU - Chang, J. T2 - International Journal of Applied Ceramic Technology AB - Bioactive tricalcium silicate ceramics (Ca3SiO5) were fabricated by spark plasma sintering (SPS), and their sinterability and mechanical properties were examined. The bioactivity and in vitro biocompatibility of Ca3SiO5 ceramics were evaluated. Ca3SiO5 ceramics show higher density and superior mechanical properties compared with those prepared by conventional pressureless sintering. In addition, hydroxyapatite was induced to form on the surface of Ca3SiO5 ceramics when soaked in simulated body fluid and bone marrow mesenchymal stem cells were attached and spread well on the ceramics. Ca3SiO5 ceramics fabricated by SPS possess excellent mechanical properties, bioactivity, and biocompatibility and are promising bone repaired materials. DA - 2011/// PY - 2011/// DO - 10.1111/j.1744-7402.2011.02613.x VL - 8 IS - 3 SP - 501-510 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79955659133&partnerID=MN8TOARS ER - TY - JOUR TI - Low-temperature spatially resolved micro-photoluminescence mapping in CdZnTe single crystals AU - Yang, G. AU - Bolotnikov, A. E. AU - Cui, Y. AU - Camarda, G. S. AU - Hossain, A. AU - Kim, K. H. AU - Gul, R. AU - James, R. B. T2 - Applied Physics Letters AB - We utilized a low-temperature spatially resolved micro-photoluminescence mapping technique to investigate the spatial variation of photoluminescence- and electronic-defect states in areas of CdZnTe (CZT) single crystals containing structural-imperfections. Photoluminescence mapping of the donor-bound-exciton emission reveals an unexpected blue-shift of the CZT bandgap at Te inclusions, which indicates that for optical measurements the localized strain field needs to be considered for accurate calculation of Zn composition and energy levels near micro-scale defects. We observed that the line widths of the donor-bound-exciton peak and defect-related D band are broadened in regions with a high density of dislocations; in contrast, the donor-acceptor-pair peak is narrowed. DA - 2011/6/27/ PY - 2011/6/27/ DO - 10.1063/1.3603930 VL - 98 IS - 26 SP - 261901 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3603930 DB - Crossref ER - TY - JOUR TI - Effect of Te inclusions in CdZnTe crystals at different temperatures AU - Hossain, A. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Gul, R. AU - Kim, K.-H. AU - Cui, Y. AU - Yang, G. AU - Xu, L. AU - James, R. B. T2 - Journal of Applied Physics AB - CdZnTe crystals often exhibit nonuniformities due to the presence of Te inclusions and dislocations. High concentrations of such defects in these crystals generally entail severe charge-trapping, a major problem in ensuring the device’s satisfactory performance. In this study, we employed a high-intensity, high-spatial-resolution synchrotron x-ray beam as the ideal tool to generate charges by focusing it over the large Te inclusions, and then observing the carrier’s response at room- and at low-temperatures. A high spatial 5-μm resolution raster scan revealed the fine details of the presence of extended defects, like Te inclusions and dislocations in the CdZnTe crystals. A noticeable change was observed in the efficiency of electron charge collection at low temperature (1 °C), but it was hardly altered at room-temperature. DA - 2011/2/15/ PY - 2011/2/15/ DO - 10.1063/1.3549236 VL - 109 IS - 4 SP - 044504-044504-4 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.3549236 DB - Crossref ER - TY - JOUR TI - Distribution of Te inclusions in a CdZnTe wafer and their effects on the electrical properties of fabricated devices AU - Hossain, A. AU - Xu, L. AU - Bolotnikov, A.E. AU - Camarda, G.S. AU - Cui, Y. AU - Yang, G. AU - Kim, K.-H. AU - James, R.B. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - We quantified the size and concentration of Te inclusions along the lateral- and the growth-directions of a ∼6 mm-thick wafer cut axially along the center of a CdZnTe ingot. We fabricated devices, selecting samples from the center slice outward in both directions, and then tested their response to incident X-rays. We employed, in concert, an automated IR transmission microscopic system and a highly collimated synchrotron X-ray source that allowed us to acquire and correlate comprehensive information on Te inclusions and other defects to assess the material factors limiting the performance of CdZnTe detectors. DA - 2011/10// PY - 2011/10// DO - 10.1016/J.NIMA.2011.01.162 VL - 652 IS - 1 SP - 146-148 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2011.01.162 DB - Crossref KW - CdZnTe KW - Detectors KW - Te inclusions KW - Dislocations KW - Pipes KW - IR transmission ER - TY - JOUR TI - Effect of extended defects in planar and pixelated CdZnTe detectors AU - Camarda, G.S. AU - Andreini, K.W. AU - Bolotnikov, A.E. AU - Cui, Y. AU - Hossain, A. AU - Gul, R. AU - Kim, K.-H. AU - Marchini, L. AU - Xu, L. AU - Yang, G. AU - Tkaczyk, J.E. AU - James, R.B. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - We evaluated a spectroscopy-grade 15×15×7 mm3 CdZnTe (CZT) crystal with a high μτ-product, >10−2 cm2/V, but impaired by microscopic extended defects, such as walls of dislocations, low-angle and sub-grain boundaries, and Te inclusions. First, we evaluated a planar detector fabricated from this crystal using a Micro-scale X-ray Detector Mapping (MXDM) technique. Then, we fabricated from the same crystal a pixel detector to study local non-uniformities of the electric field. The measured X-ray response maps confirmed the presence of non-uniformities in the charge transport, and they showed that the global- and local-distortions of the internal E-field correlated to the extended defects and space-charge buildup on the side surfaces. DA - 2011/10// PY - 2011/10// DO - 10.1016/J.NIMA.2010.12.012 VL - 652 IS - 1 SP - 170-173 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2010.12.012 DB - Crossref KW - CdZnTe KW - CZT KW - X-ray response maps KW - Extended defects KW - Dislocations KW - Detectors ER - TY - JOUR TI - Internal Electric Field Behavior of Cadmium Zinc Telluride Radiation Detectors Under High Carrier Injection AU - Yang, G. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Cui, Y. AU - Hossain, A. AU - Kim, K. H. AU - Gul, R. AU - James, R. B. T2 - Journal of Electronic Materials AB - The behavior of the internal electric field of nuclear-radiation detectors substantially affects detector performance. We investigated the distribution of the internal field in cadmium zinc telluride (CZT) detectors under high carrier injection. We noted the build-up of a space-charge region near the cathode that produces a built-in field opposing the applied field. Its presence entails the collapse of the electric field in the rest of the detector, other than the portion near the cathode. Such a space-charge region originates from serious hole trapping in CZT. The device’s operating temperature greatly affects the width of the space-charge region. With increasing temperature from 5°C to 35°C, its width expanded from about one-sixth to one-half of the total depth of the detector. DA - 2011/5/17/ PY - 2011/5/17/ DO - 10.1007/S11664-011-1656-3 VL - 40 IS - 8 SP - 1689-1692 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-011-1656-3 DB - Crossref KW - CZT KW - Pockels effect KW - electric field KW - hole trapping KW - polarization ER - TY - JOUR TI - Deterministic modeling of higher angular moments of resonant neutron scattering AU - Ghrayeb, Shadi Z. AU - Ouisloumen, Mohamed AU - Ougouag, Abderrafi M. AU - Ivanov, Kostadin N. T2 - Annals of Nuclear Energy AB - An exact scattering kernel formulation for anisotropic scattering up to angular order 10 has been developed and implemented into a deterministic code. The effects of accounting for lattice dynamics on the modeling of neutron scattering in 235U, 238U, 238Pu, and other nuclides have been demonstrated. The new formulation essentially reproduces other investigators previous results for isotropic scattering and quantifies the departures from the isotropic values when higher angular orders are accounted for. The correct accounting for the lattice effects influences the estimated values for the probability of neutron absorption and scattering, which in turn affect the estimation of core reactivity and burnup characteristics. It is shown that, when using the exact scattering kernel formulation, the probability for upscattering significantly increases with increasing temperatures. For example, upscattering for 238U from below the 20.67 eV resonance increases from 5.57% at 300 K to 30.41% at 1000 K, respectively. Thus, it is shown that the exact scattering kernel is strongly sensitive to temperature, a fact of major importance for High Temperature Reactor fuels. The slowing down process is important in thermal reactors because it results in the neutrons entering the thermal energy range in which the majority of fission events occur. Correctly modeling the slowing down and hence slowing down source into the thermal energy range and consequently allowing the correct modeling of the thermal energy neutron fluxes (or the correct thermal range portion of the spectrum) is paramount to the correct prediction of criticality and safety features such as the Doppler effect. These artifacts are important for all thermal spectrum reactors. In High Temperature Reactors such as the NGNP or the Deep Burn HTR these effects are even more important. DA - 2011/10// PY - 2011/10// DO - 10.1016/j.anucene.2011.04.025 VL - 38 IS - 10 SP - 2291-2297 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2011.04.025 DB - Crossref KW - Deterministic KW - Resonance scattering KW - Moment KW - Kernel KW - Doppler effect ER - TY - JOUR TI - MCOR – Monte Carlo depletion code for reference LWR calculations AU - Espel, Federico Puente AU - Tippayakul, Chanatip AU - Ivanov, Kostadin AU - Misu, Stefan T2 - Annals of Nuclear Energy AB - Abstract The MCOR (MCnp-kORigen) code system is a Monte Carlo based depletion system for reference fuel assembly and core calculations. The MCOR code is designed as an interfacing code that provides depletion capability to the LANL Monte Carlo code by coupling two codes: MCNP5 with the AREVA NP depletion code, KORIGEN. The physical quality of both codes is unchanged. The MCOR code system has been maintained and continuously enhanced since it was initially developed and validated. The verification of the coupling was made by evaluating the MCOR code against similar sophisticated code systems like MONTEBURNS, OCTOPUS and TRIPOLI-PEPIN. After its validation, the MCOR code has been further improved with important features. The MCOR code presents several valuable capabilities such as: (a) a predictor–corrector depletion algorithm, (b) utilization of KORIGEN as the depletion module, (c) individual depletion calculation of each burnup zone (no burnup zone grouping is required, which is particularly important for the modeling of gadolinium rings), and (d) on-line burnup cross-section generation by the Monte Carlo calculation for 88 isotopes and usage of the KORIGEN libraries for PWR and BWR typical spectra for the remaining isotopes. Besides the just mentioned capabilities, the MCOR code newest enhancements focus on the possibility of executing the MCNP5 calculation in sequential or parallel mode, a user-friendly automatic re-start capability, a modification of the burnup step size evaluation, and a post-processor and test-matrix, just to name the most important. The article describes the capabilities of the MCOR code system; from its design and development to its latest improvements and further ameliorations. Additionally, several interesting studies performed with MCOR are explained; its validation against MONTEBURNS, OCTOPUS and TRIPOLI-PEPIN; sensitivity studies with different voids and cross-section libraries; detailed comparison against measurement. Finally, the MCOR is used as a reference tool for benchmarking deterministic codes on the example of qualification of the spectral codes (APOLLO2-A and CASMO-4). DA - 2011/4// PY - 2011/4// DO - 10.1016/j.anucene.2010.12.010 VL - 38 IS - 4 SP - 731-741 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2010.12.010 DB - Crossref KW - Monte Carlo depletion KW - MCOR KW - Fuel assembly reference calculations KW - MCNP5 KW - KORIGEN ER - TY - JOUR TI - Spectral zone selection methodology for pebble bed reactors AU - Mphahlele, Ramatsemela AU - Ougouag, Abderrafi M. AU - Ivanov, Kostadin N. AU - Gougar, Hans D. T2 - Annals of Nuclear Energy AB - A methodology is developed for determining boundaries of spectral zones for pebble bed reactors. A spectral zone is defined as a region made up of a number of nodes whose characteristics are collectively similar and that are assigned the same few-group diffusion constants. The spectral zones are selected in such a manner that the difference (error) between the reference transport solution and the diffusion code solution takes a minimum value. This is achieved by choosing spectral zones through optimally minimizing this error. The objective function for the optimization algorithm is the total reaction rate error, which is defined as the sum of the leakage, absorption and fission reaction rates errors in each zone. The selection of these spectral zones is such that the core calculation results based on diffusion theory are within an acceptable tolerance as compared to a proper transport reference solution. Through this work, a consistent approach for identifying spectral zones that yield more accurate diffusion results is introduced. DA - 2011/1// PY - 2011/1// DO - 10.1016/j.anucene.2010.08.014 VL - 38 IS - 1 SP - 80-87 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2010.08.014 DB - Crossref KW - High temperature gas cooled reactor (HTR) KW - Pebble Bed Modular Reactor (PBMR) KW - Spectral zone KW - Selection methodology KW - Optimization algorithm ER - TY - JOUR TI - Experimental validation of a coupled neutron–photon inverse radiation transport solver AU - Mattingly, John AU - Mitchell, Dean J. AU - Harding, Lee T. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Sandia National Laboratories has developed an inverse radiation transport solver that applies nonlinear regression to coupled neutron–photon deterministic transport models. The inverse solver uses nonlinear regression to fit a radiation transport model to gamma spectrometry and neutron multiplicity counting measurements. The subject of this paper is the experimental validation of that solver. This paper describes a series of experiments conducted with a 4.5 kg sphere of α-phase, weapons-grade plutonium. The source was measured bare and reflected by high-density polyethylene (HDPE) spherical shells with total thicknesses between 1.27 and 15.24 cm. Neutron and photon emissions from the source were measured using three instruments: a gross neutron counter, a portable neutron multiplicity counter, and a high-resolution gamma spectrometer. These measurements were used as input to the inverse radiation transport solver to evaluate the solver's ability to correctly infer the configuration of the source from its measured radiation signatures. DA - 2011/10// PY - 2011/10// DO - 10.1016/J.NIMA.2011.01.139 VL - 652 IS - 1 SP - 537-539 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2011.01.139 DB - Crossref KW - Gamma spectrometry KW - Neutron multiplicity counting KW - Radiation transport KW - Inverse problems ER - TY - JOUR TI - Simulation of polyethylene-moderated plutonium neutron multiplicity measurements AU - Miller, E.C. AU - Dennis, B. AU - Clarke, S.D. AU - Pozzi, S.A. AU - Mattingly, J.K. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Neutron multiplicity measurements are a useful technique for the characterization of special nuclear material. This technique relies on the detection of correlated neutrons from fission events. As correlated events are detected it is possible to determine the neutron multiplicity distribution for the sample. This distribution is useful for identifying the material and estimating the mass. This work focuses on the ability of the Monte Carlo code MCNP-PoliMi to simulate measured distributions. The experiment used as the basis of comparison consisted of a 4.5 kg plutonium metal sphere surrounded by up to 6 in. of polyethylene. A bank of 15 3He detectors was used to detect the correlated neutron events. MCNP-PoliMi was used to simulate the particle transport and a post-processing algorithm was developed to apply detector deadtime effects and to determine the neutron multiplicity distributions. These simulated distributions were then compared to the measured results. The simulation provided an adequate estimation of the measured data. However, we observed a systematic over-prediction in both the mean and the variance of the measured distribution. DA - 2011/10// PY - 2011/10// DO - 10.1016/J.NIMA.2011.01.042 VL - 652 IS - 1 SP - 540-543 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2011.01.042 DB - Crossref KW - Monte Carlo KW - MCNP-PoliMi KW - Neutron multiplicity ER - TY - JOUR TI - Analysis of atmospheric pressure plasma parameters during treatment of polyethylene terephthalate films AU - Deichmann, Thorsten AU - McCord, Marian G. AU - Bourham, Mohamed A. AU - Gries, Thomas T2 - Journal of Applied Polymer Science AB - Abstract The North Carolina atmospheric plasma system (NCAPS) was interfaced with electric diagnostics and computer‐based instrument control hardware and software to display plasma parameters in real‐time. The monitoring system is also interfaced with gas flow controllers and a Teflon‐coated thermocouple for continuous monitoring of the gas flow and the ambient temperature inside the plasma test cell. A simplified plasma model was developed and built in the interface system to solve for the plasma electron number density and display the results during device operation. Polyethylene terephthalate (PET) films were treated in the device using various gas combinations. The ambient gas temperature inside the test cell increases from 83 to close to 95°F (28.33–35°C) for most gases within 30 s, and further increases to about 105 (40.6°C) after 300 s of operation, indicating a nonthermal plasma condition inside the test cell. The interface solver shows that the electron number density decreases when PET films are immersed in the plasma, indicating recombination of etched species to the free electrons. Contact angle measurements showed that the wettability of PET surfaces increased after plasma exposure for all used gas combinations. Measurements of Young's modulus with dynamic mechanical analysis (DMA) showed an increase of the modulus of PET after treatment with helium plasma, whereas the modulus slightly decreased after treatment with oxygen, tetrafluorocarbon and hexafluorocarbon gases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 DA - 2011/3/10/ PY - 2011/3/10/ DO - 10.1002/app.33557 VL - 121 IS - 4 SP - 1875-1884 J2 - J. Appl. Polym. Sci. LA - en OP - SN - 0021-8995 UR - http://dx.doi.org/10.1002/app.33557 DB - Crossref KW - atmospheric plasma KW - cold plasma KW - polyesters KW - films KW - modeling ER - TY - JOUR TI - An experimental study of rupture dynamics of evaporating liquid films on different heater surfaces AU - Gong, S. AU - Ma, W. AU - Dinh, T.-N. T2 - International Journal of Heat and Mass Transfer AB - Experimental data were obtained to reveal the complex dynamics of thin liquid films evaporating on heated horizontal surfaces, including formation and expansion of dry spots that occur after the liquid films decreased below critical thicknesses. The critical thickness of water film evaporating on various material surfaces is measured in the range of 60–150 μm, increasing with contact angle and heat flux while decreasing with thermal conductivity of the heater material. In the case of hexane evaporating on a titanium surface, the liquid film is found resilient to rupture, but starts oscillating as the averaged film thickness decreases below 15 μm. DA - 2011/// PY - 2011/// DO - 10.1016/j.ijheatmasstransfer.2010.11.036 VL - 54 IS - 7-8 SP - 1538-1547 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751643541&partnerID=MN8TOARS KW - Liquid film KW - Film evaporation KW - Film dynamics KW - Film rupture KW - Film thickness measurement ER - TY - CONF TI - Lessons learned from an initial VU-assessed code development effort AU - Nourgaliev, R.R. AU - Dinh, T.-N. AU - Nelson, R.A. C2 - 2011/// C3 - Transactions of the American Nuclear Society DA - 2011/// VL - 104 SP - 358-360 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875659394&partnerID=MN8TOARS ER - TY - CONF TI - Heartbeat model for component failure time in simulation of plant behavior AU - Youngblood, R.W. AU - Nourgaliev, R.R. AU - Kelly, D.L. AU - Smith, C.L. AU - Dinh, T.-N. C2 - 2011/// C3 - International Topical Meeting on Probabilistic Safety Assessment and Analysis 2011, PSA 2011 DA - 2011/// VL - 1 SP - 646-654 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-80051988899&partnerID=MN8TOARS ER - TY - CONF TI - Framework for applying a next-generation safety analysis code to plant life extension decision making, invited AU - Youngblood, R.W. AU - Nourgaliev, R.R. AU - Kelly, D.L. AU - Smith, C.L. AU - Dinh, T.-N. C2 - 2011/// C3 - Transactions of the American Nuclear Society DA - 2011/// VL - 104 SP - 949-950 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875658203&partnerID=MN8TOARS ER - TY - CONF TI - On physics modeling and components development in R7 AU - Bui, A. AU - Nourgaliev, R.R. AU - Dinh, T.-N. C2 - 2011/// C3 - Transactions of the American Nuclear Society DA - 2011/// VL - 104 SP - 523-525 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875679207&partnerID=MN8TOARS ER - TY - CONF TI - A system simulation code to support the safety case in the LVVR life extension: Selection, development, and testing of code architecture and solution algorithms, invited AU - Dinh, T.-N. AU - Nourgaliev, R.R. AU - Youngblood, R.W. C2 - 2011/// C3 - Transactions of the American Nuclear Society DA - 2011/// VL - 104 SP - 951-953 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875674404&partnerID=MN8TOARS ER - TY - PAT TI - Improving Plasma Process Uniformity Across A Wafer By Apportioning Power Among Plural Vhf Sources C2 - 2011/2/1/ DA - 2011/2/1/ PY - 2011/2/1/ UR - https://www.lens.org/035-374-849-498-503 ER - TY - PAT TI - Plasma Process Uniformity Across A Wafer By Controlling Rf Phase Between Opposing Electrodes C2 - 2011/12/13/ DA - 2011/12/13/ PY - 2011/12/13/ UR - https://www.lens.org/003-021-090-469-410 ER - TY - PAT TI - Plasma Process Uniformity Across A Wafer By Controlling A Variable Frequency Coupled To A Harmonic Resonator C2 - 2011/12/20/ DA - 2011/12/20/ PY - 2011/12/20/ UR - https://www.lens.org/145-961-377-173-552 ER - TY - PAT TI - Method Of Processing A Workpiece In A Plasma Reactor With Variable Height Ground Return Path To Control Plasma Ion Density Uniformity C2 - 2011/6/28/ DA - 2011/6/28/ PY - 2011/6/28/ UR - https://www.lens.org/082-874-457-200-865 ER - TY - PAT TI - Plasma Process Uniformity Across A Wafer By Apportioning Ground Return Path Impedances Among Plural Vhf Sources C2 - 2011/2/8/ DA - 2011/2/8/ PY - 2011/2/8/ UR - https://www.lens.org/004-808-299-268-13X ER - TY - JOUR TI - Special issue on the 16th biennial topical meeting of the radiation protection and shielding division AU - Hayes, R.B. T2 - Nuclear Technology AB - "Foreword: Special Issue on the 16th Biennial Topical Meeting of the Radiation Protection and Shielding Division." Nuclear Technology, 175(1), p. 1 DA - 2011/// PY - 2011/// DO - 10.13182/NT11-A12259 VL - 175 IS - 1 SP - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79960675149&partnerID=MN8TOARS ER - TY - CONF TI - In vitro characterization of bacterial macromolecule damage induced by low-pressure VHF-CCP plasma AU - Lackmann, Jan-Wilm AU - Stapelmann, Katharina AU - Narberhaus, Franz AU - Awakowicz, Peter AU - Bandow, Julia E C2 - 2011/// C3 - 20nd International Symposium on Plasma Chemistry (ISPC-20), Philadelphia, Pennsylvania, USA, 2011 DA - 2011/// UR - http://www.ispc-conference.org/ispcproc/ispc20/532.pdf ER - TY - CONF TI - Characterization of a novel VHF-CCP for sterilization and decontamination of medical instruments AU - Stapelmann, Katharina AU - Lackmann, Jan-Wilm AU - Bibinov, Nikita AU - Bandow, Julia E AU - Postema, Michiel AU - Awakowicz, Peter C2 - 2011/// C3 - 20nd International Symposium on Plasma Chemistry (ISPC-20), Philadelphia, Pennsylvania, USA, 2011 DA - 2011/// UR - http://www.ispc-conference.org/ispcproc/ispc20/368.pdf ER - TY - JOUR TI - Characterization of a Low-pressure Inductively Coupled Plasma Discharge Sustained in Ar/O2/N2 Ternary Mixtures and Evaluation of its Effect on Erosion of Biological Samples AU - Kylian, Ondrej AU - Denis, Benjamin AU - Stapelmann, Katharina AU - Ruiz, Ana AU - Rauscher, Hubert AU - Rossi, Francois T2 - PLASMA PROCESSES AND POLYMERS AB - Abstract Detailed characterization of a low‐pressure inductively coupled plasma discharge sustained in an Ar/O 2 /N 2 ternary mixture is performed in this study. The main attention is devoted to the evaluation of the dependence of parameters important for treatment of biological samples (emission of UV radiation, plasma density, energy of charged particles, O atoms density, and substrate heating) on the working gas mixture composition. Subsequently, the capability of plasma sustained in ternary gas mixture to effectively etch biological contaminants is tested on examples of bacterial spores and poly‐ L ‐histidine. magnified image DA - 2011/12/20/ PY - 2011/12/20/ DO - 10.1002/ppap.201100086 VL - 8 IS - 12 SP - 1137-1145 SN - 1612-8850 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298354000005&KeyUID=WOS:000298354000005 KW - amino acids KW - bacterial spores KW - decontamination KW - sterilization KW - ternary mixture ER - TY - JOUR TI - Multifunctional ZnO/Nylon 6 nanofiber mats by an electrospinning-electrospraying hybrid process for use in protective applications AU - Vitchuli, Narendiran AU - Shi, Quan AU - Nowak, Joshua AU - Kay, Kathryn AU - Caldwell, Jane M. AU - Breidt, Frederick AU - Bourham, Mohamed AU - McCord, Marian AU - Zhang, Xiangwu T2 - SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS AB - ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning-electrospraying hybrid process in which ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers without becoming completely embedded. The prepared ZnO/Nylon 6 nanofiber mats were evaluated for their abilities to kill bacteria or inhibit their growth and to catalytically detoxify chemicals. Results showed that these ZnO/Nylon 6 nanofiber mats had excellent antibacterial efficiency (99.99%) against both the Gram-negative Escherichia coli and Gram-positive Bacillus cereus bacteria. In addition, they exhibited good detoxifying efficiency (95%) against paraoxon, a simulant of highly toxic chemicals. ZnO/Nylon 6 nanofiber mats were also deposited onto nylon/cotton woven fabrics and the nanofiber mats did not significantly affect the moisture vapor transmission rates and air permeability values of the fabrics. Therefore, ZnO/Nylon 6 nanofiber mats prepared by the electrospinning-electrospraying hybrid process are promising material candidates for protective applications. DA - 2011/10// PY - 2011/10// DO - 10.1088/1468-6996/12/5/055004 VL - 12 IS - 5 SP - SN - 1468-6996 KW - electrospinning KW - electrospraying KW - Nylon 6 KW - zinc oxide KW - antibacterial KW - detoxification ER - TY - JOUR TI - Exact-to-precision generalized perturbation theory for source-driven systems AU - Wang, Congjian AU - Abdel-Khalik, Hany S. T2 - NUCLEAR ENGINEERING AND DESIGN AB - Presented in this manuscript are new developments to perturbation theory which are intended to extend its applicability to estimate, with quantifiable accuracy, the exact variations in all responses calculated by the model with respect to all possible perturbations in the model's input parameters. The new developments place high premium on reducing the associated computational overhead in order to enable the use of perturbation theory in routine reactor design calculations. By way of examples, these developments could be employed in core simulation to accurately estimate the few-group cross-sections variations resulting from perturbations in neutronics and thermal-hydraulics core conditions. These variations are currently being described using a look-up table approach, where thousands of assembly calculations are performed to capture few-group cross-sections variations for the downstream core calculations. Other applications include the efficient evaluation of surrogates for applications that require repeated model runs such as design optimization, inverse studies, uncertainty quantification, and online core monitoring. The theoretical background of these developments applied to source-driven systems and supporting numerical experiments are presented in this manuscript. Extension to eigenvalue problems will be presented in a future article. DA - 2011/12// PY - 2011/12// DO - 10.1016/j.nucengdes.2011.09.009 VL - 241 IS - 12 SP - 5104-5112 SN - 0029-5493 ER - TY - JOUR TI - Produced water characterization by prompt gamma-ray neutron activation analysis AU - Meric, I. AU - Johansen, G. A. AU - Holstad, M. B. AU - Wang, J. X. AU - Gardner, R. P. T2 - Measurement Science & Technology AB - Multiphase gas/oil/water measurement has been and still is a challenging task within the petroleum industry. The requirements of measurement efficiency and accuracy have been continuously increasing at the same time as the trend is to use subsea installations. As a response, the design of the SOFA (Subsea Online Fluid Analyser) concept was initiated by Christian Michelsen Research in cooperation with the University of Bergen. The final design of the analyser is yet to be completed. The ultimate goal of this design is the development of a permanently installed subsea metering station which is capable of characterizing all of the components that can be found in multiphase flow. One of the key challenges in this design is the detailed characterization of produced water samples which includes the identification of salt ions in the sample and their weight percentages. In this work, use of prompt gamma-ray neutron activation analysis (PGNAA) in conjunction with the so-called Monte Carlo library least-squares (MCLLS) approach is considered for characterization of the produced water component. A relatively simple produced water sample was prepared and the prompt gamma-ray spectrum of the sample was recorded using a large 6" × 6" NaI(Tl) scintillation detector. A specific purpose Monte Carlo code named CEARCPG was used to generate the pertinent elemental libraries that are required in the MCLLS approach. The results of this feasibility study have shown that the PGNAA in conjunction with the MCLLS approach would be feasible for determining the amounts of salt ions that can be found in produced water samples. DA - 2011/// PY - 2011/// DO - 10.1088/0957-0233/22/12/125701 VL - 22 IS - 12 ER - TY - CONF TI - A comparative study of different low-Z liner materials in an ablation-dominated electrothermal mass accelerator for fusion fueling AU - Winfrey, A. L. AU - Gilligan, J. G. AU - Bourham, Mohamed AB - A low-z ablation-dominated capillary with an ablation-free extension barrel is a concept that provides a plasma flow sufficient to propel fuel pellets into the tokamak fusion plasma chamber. The acceleration barrel is made from a non-ablating material to eliminate mixing the propelling plasma with any impurities evolving from the barrel ablation. A capillary discharge computer code, ETFLOW, has been developed to model plasma flow and acceleration of pellets for fusion fueling in magnetic confinement fusion reactors. The code incorporates a set of governing equations for both the capillary and the acceleration tube and ideal and non-ideal conductivity models. The joule heating in the energy conservation equation is only valid in the capillary section. The pellet momentum and kinetic energy are included in the governing equations of the barrel, with the addition of the effect of viscous drag terms. The capillary generates the plasma from the ablation of low-z liner materials "sleeves" inside the capillary. The acceleration of the pellet starts in the extension tube when the pressure of the plasma flow from the capillary reaches the release limit. The code results show exit velocities in excess of 2km/s for source/barrel systems with low-Z liner materials in the source and loaded with 5, 20, 45, and 80 mg pellets. An increase in the length of both the source and the acceleration barrel increases the pellet exit velocity with the limitation of slowdown effects for plasma expansion and cooling off inside the barrel. C2 - 2011/// C3 - 2011 IEEE/NPSS 24th Symposium on Fusion Engineering (SOFE) DA - 2011/// DO - 10.1109/sofe.2011.6052238 ER - TY - JOUR TI - Use of the CEARXRF GUI-Based Monte Carlo-Library Least-Squares (MCLLS) Code for the Micro-Focused EDXRF analyzer AU - Gardner, Robin P. AU - Li, Fusheng T2 - X-RAY SPECTROMETRY AB - The CEARXRF GUI‐Based Monte Carlo–Library Least‐Squares (MCLLS) Code is demonstrated with results from a micro‐focused EDXRF analyzer, which can be used to calculate elemental weight fractions in metal alloys or rock samples accurately by library least‐squares regression of the measured X‐ray spectrum with computer‐generated elemental library spectra. An elemental stratified sampling variance reduction technique has been implemented in the CEARXRF5 code, which equalizes the statistical precision of the elemental libraries within the measured sample independent of the relative elemental amounts that are present. Also, an improved Si(Li) detector response function (DRF) has been obtained for micro‐focused X‐ray fluorescence (XRF) analyzers, and the DRF parameters are obtained based on regression from pure elemental experimental spectra. It is demonstrated that the resulting MCLLS approach can greatly improve the accuracy of elemental XRF analysis results. Copyright © 2011 John Wiley & Sons, Ltd. DA - 2011/// PY - 2011/// DO - 10.1002/xrs.1365 VL - 40 IS - 6 SP - 405-410 SN - 0049-8246 ER - TY - JOUR TI - Time scale bridging in atomistic simulation of slow dynamics: viscous relaxation and defect activation AU - Kushima, A. AU - Eapen, J. AU - Li, Ju AU - Yip, S. AU - Zhu, T. T2 - EUROPEAN PHYSICAL JOURNAL B DA - 2011/8// PY - 2011/8// DO - 10.1140/epjb/e2011-20075-4 VL - 82 IS - 3-4 SP - 271-293 SN - 1434-6036 ER - TY - JOUR TI - Examining the importance of the particle size effect in inhalation dose assessment for short-term radiological events AU - Srimok, B. AU - Yim, M. S. T2 - Radiation Protection Dosimetry DA - 2011/// PY - 2011/// VL - 147 IS - 3 SP - 439-450 ER - TY - JOUR TI - Use of an iterative convolution approach for qualitative and quantitative peak analysis in low resolution gamma-ray spectra AU - Gardner, Robin P. AU - Ai, Xianyun AU - Peeples, Cody R. AU - Wang, Jiaxin AU - Lee, Kyoung AU - Peeples, Johanna L. AU - Calderon, Adan T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - In many applications, low resolution gamma-ray spectrometers, such as sodium iodide scintillation detectors, are widely used primarily due to their relatively low cost and high detection efficiency. There is widespread interest in improved methods for analyzing spectral data acquired with such devices, using inverse analysis. Peak means and peak areas in gamma- and X-ray spectra are needed for both qualitative and quantitative analysis. This paper introduces the PEAKSI code package that was developed at the Center for Engineering Applications of Radioisotopes (CEAR). The basic approach described here is to use accurate forward models and iterative convolution instead of direct deconvolution. Rather than smoothing and differentiation a combination of linear regression and non-linear searching is used to minimize the reduced chi-square, since this approach retains the capability of establishing uncertainties in the estimated peak parameters. The PEAKSI package uses a Levenberg–Marquardt (LM) non-linear search method combined with multiple linear regression (MLR) to minimize the reduced chi-square value for fitting single or multiple overlapping peaks to determine peak parameters, including peak means, peak standard deviations or full width at half maximum (FWHM), net peak counts, and background counts of peaks in experimental gamma-ray spectra. This approach maintains the natural error structure so that parameter uncertainties can be estimated. The plan is to release this code to the public in the near future. DA - 2011/10/1/ PY - 2011/10/1/ DO - 10.1016/j.nima.2010.12.224 VL - 652 IS - 1 SP - 544-549 SN - 0168-9002 KW - Gamma spectroscopy KW - Sodium iodide KW - Peak convolution ER - TY - JOUR TI - Phase contrast neutron imaging at the PULSTAR reactor AU - Mishra, Kaushal K. AU - Hawari, Ayman I. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Abstract Non-interferometric phase contrast effects have been shown to enhance material edges in neutron images. The achieved contrast enhancement in the image depends upon the neutron coherent scattering lengths of the materials present in the object and the degree of spatial coherence of the neutron beam. Spatial coherence of the beam is achieved using design-based spatial filters, a large L / d ratio (∼10,000) and low average neutron energy. Physically, a large L / d ratio is realized by a pinhole neutron source thereby significantly reducing the neutron beam intensity at the image plane. Thus, performance of such imaging exercises at low/medium intensity neutron sources is associated with additional design considerations that are not needed at high intensity neutron sources, where it has been demonstrated. In the present work, phase contrast neutron imaging was conducted using a suitably designed collimator at the 1-MWth PULSTAR reactor located at North Carolina State University (NCSU). Results of the imaging exercises that depict phase contrast edge enhancement are being presented along with the collimator design. Digital image plate detectors were used to capture images with a range of exposure times between 45 and 120 min. DA - 2011/10/1/ PY - 2011/10/1/ DO - 10.1016/j.nima.2010.09.113 VL - 652 IS - 1 SP - 615-619 SN - 1872-9576 KW - Neutron imaging KW - Phase Contrast Imaging KW - Nuclear reactor ER - TY - JOUR TI - Multilevel Quasidiffusion Methods for Solving Multigroup Neutron Transport k-Eigenvalue Problems in One-Dimensional Slab Geometry AU - Anistratov, Dmitriy Y. AU - Gol'din, Vladimir Ya T2 - NUCLEAR SCIENCE AND ENGINEERING AB - The methods for solving k-eigenvalue problems for the multigroup neutron transport equation in one-dimensional slab geometry are presented. They are defined by means of multigroup and effective grey (one-group) low-order quasidiffusion (QD) equations. In this paper we formulate and study different variants of nonlinear QD iteration algorithms. These methods are analyzed on a set of test problems designed using C5G7 benchmark data. We present numerical results that demonstrate the performance of iteration schemes in different types of reactor physics problems. We consider tests that represent single-assembly and color-set calculations as well as a problem with elements of full-core computations involving a reflector zone. DA - 2011/10// PY - 2011/10// DO - 10.13182/nse10-64 VL - 169 IS - 2 SP - 111-132 SN - 0029-5639 ER - TY - JOUR TI - Monte Carlo investigation and optimization of coincidence prompt gamma-ray neutron activation analysis AU - Wang, Jiaxin AU - Calderon, Adan AU - Peeples, Cody R. AU - Ai, Xianyun AU - Gardner, Robin P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Normal Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) suffers from a large inherent noise or background. The coincidence PGNAA approach is being investigated for eliminating almost all of the interfering backgrounds and thereby significantly improving the signal-to-noise ratio (SNR). This can be done since almost all of the prompt gamma rays from elements of interest are emitted in coincidence except hydrogen. However, it has been found previously that while the use of two normal NaI detectors greatly reduces the background, the signal is also greatly reduced so that very little improvement in standard deviation is obtained. With the help of MCNP5, the general-purpose Monte Carlo N-Particle code, and CEARCPG, the specific purpose Monte Carlo code for Coincidence PGNAA, further optimization of the proposed coincidence system is being accomplished. The idea pursued here is the use of a large area plastic scintillation detector as the trigger for coincidence events together with a normal large NaI detector. In this approach the detection solid angle is increased greatly, which directly increases the probability of coincidence detection. The 2D-coincidence spectrum obtained can then be projected to the axis representing the NaI detector to overcome the drawback of low energy resolution and photopeak intensity of the plastic scintillation detector and utilize the overall higher coincidence counting rate. To reach the best coincidence detection, the placement of detectors, sample, and the moderator of the neutron source have been optimized through Monte Carlo simulation. DA - 2011/10/1/ PY - 2011/10/1/ DO - 10.1016/j.nima.2010.08.011 VL - 652 IS - 1 SP - 572-577 SN - 1872-9576 KW - Coincidence KW - PGNAA KW - Monte Carlo KW - CEARCPG ER - TY - JOUR TI - Coded source neutron imaging at the PULSTAR reactor AU - Xiao, Ziyu AU - Mishra, Kaushal K. AU - Hawari, Ayman I. AU - Bingham, Philip R. AU - Bilheux, Hassina Z. AU - Tobin, Kenneth W. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - A neutron imaging facility is located on beam-tube #5 of the 1-MW PULSTAR reactor at North Carolina State University. An investigation of high resolution imaging using the coded source imaging technique has been initiated at the facility. Coded imaging uses a mosaic of pinholes to encode an aperture, thus generating an encoded image of the object at the detector. To reconstruct the image data received by the detector, the corresponding decoding patterns are used. The optimized design of coded mask is critical for the performance of this technique and will depend on the characteristics of the imaging beam. In this work, a 34×38 uniformly redundant array (URA) coded aperture system is studied for application at the PULSTAR reactor neutron imaging facility. The URA pattern was fabricated on a 500 μm gadolinium sheet. Simulations and experiments with a pinhole object have been conducted using the Gd URA and the optimized beam line. DA - 2011/10/1/ PY - 2011/10/1/ DO - 10.1016/j.nima.2010.10.049 VL - 652 IS - 1 SP - 606-609 SN - 1872-9576 KW - Coded source imaging KW - Neutron imaging KW - Nuclear reactor ER - TY - JOUR TI - Analysis of equilibrium methods for the computational model of the mark-IV electrorefiner AU - Cumberland, R. AU - Hoover, R. AU - Phongikaroon, S. AU - Yim, M. S. T2 - Nuclear Engineering and Technology DA - 2011/// PY - 2011/// VL - 43 IS - 6 SP - 547-556 ER - TY - JOUR TI - A single scatter electron Monte Carlo approach for simulating gamma-ray stopping efficiencies of Geiger-Müller counters AU - Meric, Ilker AU - Johansen, Geir A. AU - Holstad, Marie B. AU - Lee, Kyoung O. AU - Calderon, Adan F. AU - Wang, Jiaxin AU - Gardner, Robin P. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Abstract In spite of their relatively poor gamma-ray stopping efficiencies, the Geiger-Muller (GM) counter is still preferred in many radioisotope gauges for industrial measurements. This is because these detectors exhibit a high degree of robustness in harsh environments, are relatively insensitive to temperature changes in the environment, and are inexpensive compared to other types of radiation detectors. These properties could make the use of GM counters very feasible in a number of industrial applications, such as gamma-ray tomography and gamma-ray density gauges, provided that their gamma-ray stopping efficiencies can be improved. The Monte Carlo (MC) method is a powerful computational physics tool that is utilized very often in the design of radiation detectors and radioisotope gauges. In this work a MC model for GM counters that is benchmarked with experiments at the primary photon energy of 59.5 keV is proposed. This is a specific purpose MC simulation code that, as opposed to publicly available general purpose MC codes, employs single scatter (or microscopic) electron transport and is currently under development. In this paper, the MC code is described in detail and the results of the specific purpose MC code are benchmarked with experiments and two general purpose MC codes, MCNP5 and PENELOPE. It was observed that the specific purpose MC code improved the reduced chi-square value when compared to MCNP5 and PENELOPE. DA - 2011/10// PY - 2011/10// DO - 10.1016/J.NIMA.2011.06.065 VL - 654 IS - 1 SP - 279-287 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2011.06.065 DB - Crossref KW - Computational physics KW - Monte Carlo simulation KW - Single scatter electron transport KW - Geiger-Muller counter KW - Stopping efficiency ER - TY - JOUR TI - A proposed benchmark problem for cargo nuclear threat monitoring AU - Holmes, Thomas Wesley AU - Calderon, Adan AU - Peeples, Cody R. AU - Gardner, Robin P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - There is currently a great deal of technical and political effort focused on reducing the risk of potential attacks on the United States involving radiological dispersal devices or nuclear weapons. This paper proposes a benchmark problem for gamma-ray and X-ray cargo monitoring with results calculated using MCNP5, v1.51. The primary goal is to provide a benchmark problem that will allow researchers in this area to evaluate Monte Carlo models for both speed and accuracy in both forward and inverse calculational codes and approaches for nuclear security applications. A previous benchmark problem was developed by one of the authors (RPG) for two similar oil well logging problems (Gardner and Verghese, 1991, [1]). One of those benchmarks has recently been used by at least two researchers in the nuclear threat area to evaluate the speed and accuracy of Monte Carlo codes combined with variance reduction techniques. This apparent need has prompted us to design this benchmark problem specifically for the nuclear threat researcher. This benchmark consists of conceptual design and preliminary calculational results using gamma‐ray interactions on a system containing three thicknesses of three different shielding materials. A point source is placed inside the three materials lead, aluminum, and plywood. The first two materials are in right circular cylindrical form while the third is a cube. The entire system rests on a sufficiently thick lead base so as to reduce undesired scattering events. The configuration was arranged in such a manner that as gamma-ray moves from the source outward it first passes through the lead circular cylinder, then the aluminum circular cylinder, and finally the wooden cube before reaching the detector. A 2 in.×4 in.×16 in. box style NaI (Tl) detector was placed 1 m from the point source located in the center with the 4 in.×16 in. side facing the system. The two sources used in the benchmark are 137Cs and 235U. DA - 2011/10/1/ PY - 2011/10/1/ DO - 10.1016/j.nima.2010.10.070 VL - 652 IS - 1 SP - 52-57 SN - 0168-9002 KW - Benchmark KW - Cargo nuclear threat monitoring ER - TY - JOUR TI - Thermal performance of batch boiling water targets for 18F production AU - Peeples, Johanna L. AU - Stokely, Matthew H. AU - Michael Doster, J. T2 - Applied Radiation and Isotopes AB - Batch boiling targets are commonly used in cyclotrons to produce Fluorine-18 by proton bombardment of Oxygen-18 enriched water. Computational models have been developed to predict the thermal performance of bottom-pressurized batch boiling production targets. The models have been validated with experimental test data from the Duke University Medical Cyclotron and the Wisconsin Medical Cyclotron. Good agreement has been observed between experimental measurements and model predictions of average target vapor fraction as a function of beam current and energy. DA - 2011/10// PY - 2011/10// DO - 10.1016/j.apradiso.2011.06.015 VL - 69 IS - 10 SP - 1349-1354 J2 - Applied Radiation and Isotopes LA - en OP - SN - 0969-8043 UR - http://dx.doi.org/10.1016/j.apradiso.2011.06.015 DB - Crossref KW - Fluorine-18 KW - Batch boiling target KW - FDG KW - Positron emission tomography KW - Tantalum KW - Cyclotron targets ER - TY - JOUR TI - Self-repairing polymer optical fiber sensor AU - Song, Young AU - Peters, Kara T2 - 21ST INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS AB - This article presents experimental demonstrations of a self-repairing strain sensor waveguide created by self-writing in a photopolymerizable resin system. The sensor fabricates between two multi-mode optical fibers via lightwaves in the ultraviolet (UV) wavelength range and operates as a sensor through interrogation of the power transmitted through the waveguide in the infrared (IR) wavelength range. After failure of the sensor occurs due to loading, the waveguide rebridges the gap between the two optical fibers through the UV resin. The response of the original sensor and the selfrepaired sensor to strain are measured and show similar behaviors. DA - 2011/// PY - 2011/// DO - 10.1117/12.885147 VL - 7753 SP - SN - 1996-756X KW - polymer waveguide KW - strain sensor KW - self-writing waveguide ER - TY - JOUR TI - Many-Group Cross-Section Adjustment Techniques for Boiling Water Reactor Adaptive Simulation AU - Jessee, M. A. AU - Turinsky, P. J. AU - Abdel-Khalik, H. S. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - AbstractComputational capability has been developed to adjust multigroup neutron cross sections, including self-shielding correction factors, to improve the fidelity of boiling water reactor (BWR) core modeling and simulation. The method involves propagating multigroup neutron cross-section uncertainties through various BWR computational models to evaluate uncertainties in key core attributes such as core keff, nodal power distributions, thermal margins, and in-core detector readings. Uncertainty-based inverse theory methods are then employed to adjust multigroup cross sections to minimize the disagreement between BWR core modeling predictions and observed (i.e., measured) plant data. For this paper, observed plant data are virtually simulated in the form of perturbed three-dimensional nodal power distributions with the perturbations sized to represent actual discrepancies between predictions and real plant data. The major focus of this work is to efficiently propagate multigroup neutron cross-section uncertainty through BWR lattice physics and core simulator calculations. The data adjustment equations are developed using a subspace approach that exploits the ill-conditioning of the multigroup cross-section covariance matrix to minimize computation and storage burden. Tikhonov regularization is also employed to improve the conditioning of the data adjustment equations. Expressions are also provided for posterior covariance matrices of both the multigroup cross-section and core attributes uncertainties. DA - 2011/9// PY - 2011/9// DO - 10.13182/nse09-67 VL - 169 IS - 1 SP - 40-55 SN - 0029-5639 ER - TY - JOUR TI - BWR in-core fuel management optimization using parallel simulated annealing in FORMOSA-B AU - Hays, Ross AU - Turinsky, Paul T2 - PROGRESS IN NUCLEAR ENERGY AB - The process of finding optimized fuel reload patterns for boiling water reactors is complicated by a number of factors including the large number of fuel assemblies involved, the three-dimensional neutronic and thermal-hydraulic variations, and the interplay of coolant flow rate with control rod programming. The FORMOSA-B code was developed to provide an automated method for finding fuel loading patterns, control rod programs and coolant flow rate schedules to minimize certain quantitative metrics of core performance while satisfying given operational constraints. One drawback of this code has been the long runtimes required for a complete cycle optimization on a desktop workstation (oftentimes several days or more). To address this shortcoming, a parallel simulated annealing algorithm has been added to the FORMOSA-B code, so that the runtimes may be greatly reduced by using a multiprocessor computer cluster. Tests of the algorithm on a sample problem indicate that it is capable of parallel efficiencies exceeding 80% when using four processors. DA - 2011/8// PY - 2011/8// DO - 10.1016/j.pnucene.2010.09.002 VL - 53 IS - 6 SP - 600-606 SN - 0149-1970 KW - In-core fuel management KW - Boiling water reactor KW - Parallel simulated annealing ER - TY - JOUR TI - Assessment of fuel cycle proliferation resistance dynamics using coupled isotopic characterization AU - Skutnik, S. E. AU - Yim, M. S. T2 - Nuclear Engineering and Design DA - 2011/// PY - 2011/// VL - 241 IS - 8 SP - 3270-3282 ER - TY - JOUR TI - Temperature Dependence of the Dynamics of Portevin-Le Chatelier Effect in Al-2.5 Pct Mg Alloy AU - Chatterjee, A. AU - Murty, K. L. AU - Gayathri, N. AU - Mukherjee, P. AU - Barat, P. T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE AB - Tensile tests were carried out by deforming polycrystalline samples of Al-2.5 pct Mg alloy at four different temperatures in an intermediate strain rate regime of 2 × 10−4 s−1 to 2 × 10−3 s−1. The Portevin-Le Chatelier (PLC) effect was observed throughout the strain rate and temperature region. The mean cumulative stress drop magnitude and the mean reloading time exhibit an increasing trend with temperature, which is attributed to the enhanced solute diffusion at higher temperature. The observed stress–time series data were analyzed using the nonlinear dynamical methods. From the analyses, we established the presence of deterministic chaos in the PLC effect throughout the temperature regime. The dynamics goes to higher dimension at a sufficiently high temperature of 425 K (152 °C), but the complexity of the dynamics is not affected by the temperature. DA - 2011/5// PY - 2011/5// DO - 10.1007/s11661-010-0530-x VL - 42A IS - 5 SP - 1184-1190 SN - 1543-1940 ER - TY - JOUR TI - Operation and testing of the PULSTAR reactor intense slow positron beam and PALS spectrometers AU - Hawari, Ayman I. AU - Gidley, David W. AU - Moxom, Jeremy AU - Hathaway, Alfred G. AU - Mukherjee, Saurabh T2 - 12TH INTERNATIONAL WORKSHOP ON SLOW POSITRON BEAM TECHNIQUES (SLOPOS12) AB - An intense slow positron beam has been established at the 1-MW PULSTAR nuclear reactor. The beam is operational generating mono-energetic positrons with an energy of 1-keV. The maximum measured intensity slightly exceeds 109 e+/s. The beam is operated routinely with an intensity of approximately 5×108 e+/s. The positrons are generated through gamma-ray pair production interactions in two back-to-back banks of tungsten converter/moderators. The gamma-rays are produced in the PULSTAR core and by thermal neutron capture in a cadmium shroud that surrounds the tungsten. The primary utilization of the PULSTAR positron beam is the characterization of nanoscale structure in materials. Consequently, the beam has been equipped with two state-of-the-art PALS spectrometers. The first spectrometer is dedicated to measurements in materials such as metals and semiconductors. This spectrometer is based on pulsing and bunching of the primary beam and is currently operating with a timing resolution of approximately 390 picoseconds. The second spectrometer is dedicated to measurements in materials where positronium formation is promoted. The timing resolution of this spectrometer is designed to be ~ 0.5 nanosecond with an on-sample spot size of 1–2 mm. For both spectrometers, the energy of the positrons can be varied to allow depth profiling with on-sample intensity exceeding 106 e+/s. DA - 2011/// PY - 2011/// DO - 10.1088/1742-6596/262/1/012024 VL - 262 SP - SN - 1742-6588 ER - TY - JOUR TI - Newton's Method for the Computation of k-Eigenvalues in S-N Transport Applications AU - Gill, Daniel F. AU - Azmy, Yousry Y. AU - Warsa, James S. AU - Densmore, Jeffery D. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - Recently, Jacobian-Free Newton-Krylov (JFNK) methods have been used to solve the k-eigenvalue problem in diffusion and transport theories. We propose an improvement to Newton’s method (NM) for solving the k-eigenvalue problem in transport theory that avoids costly within-group iterations or iterations over energy groups. We present a formulation of the k-eigenvalue problem where a nonlinear function, whose roots are solutions of the k-eigenvalue problem, is written in terms of a generic fixed-point iteration (FPI). In this way any FPI that solves the k-eigenvalue problem can be accelerated using the Newton approach, including our improved formulation. Calculations with a one-dimensional multigroup SN transport implementation in MATLAB provide a proof of principle and show that convergence to the fundamental mode is feasible. Results generated using a three-dimensional Fortran implementation of several formulations of NM for the well-known Takeda and C5G7-MOX benchmark problems confirm the efficiency of NM for realistic k-eigenvalue calculations and highlight numerous advantages over traditional FPI. DA - 2011/5// PY - 2011/5// DO - 10.13182/nse10-01 VL - 168 IS - 1 SP - 37-58 SN - 0029-5639 ER - TY - JOUR TI - MODELING OF AN ABLATION-FREE ELECTROTHERMAL PLASMA PELLET ACCELERATOR AU - Winfrey, A. Leigh AU - Abd Al-Halim, Mohamed AU - Gilligan, John G. AU - Saveliev, Alexei V. AU - Bourham, Mohamed A. T2 - FUSION SCIENCE AND TECHNOLOGY AB - Electromagnetic and electrothermal launch devices can provide high acceleration and inject pellets with speeds in excess of 3 km/s for masses up to 3gm. However, the ablation of the bore adds impurities to the plasma. An ablation-free electrothermal pellet accelerator is a concept that utilizes an ablation-free capillary discharge in which a quartz capillary is coated with a nanocrystalline diamond film (NCD). The ablation-free capillary connects to an extension tube, which is also an ablation-free quartz tube coated with NCD that serves as the acceleration barrel. An ablation-free capillary discharge computer code has been developed to model plasma flow and acceleration of pellets for fusion fueling in magnetic fusion reactors. The code incorporates ideal and non-ideal conductivity models and has a set of governing equations for the capillary, the acceleration tube, and the pellet. The capillary generates the plasma from hydrogen/deuterium gas when the discharge current flows through the capillary. The pellet starts moving in the extension tube when the pressure of the plasma flow from the capillary reaches the release limit. The code results show an exit velocity of 2.7 km/s for a 20 mg deuterium pellet when using a capillary and barrel each 9 cm long where the source and barrel diameters are 0.4cm and 0.6cm, respectively, with a discharge current of 20 kA over a 300 both the capillary and the barrel to 12 cm increases the pellet exit velocity to 2.9 km/s, and a further increase to 18cm results in a 3.15km/s pellet exit velocity. Increasing the barrel length to 36 cm, while keeping the source length at 18 cm, results in an increase in the pellet velocity to 3.32 km/s. The pellet starts moving at 35 μs reaches 3.32 km/s in 100 this velocity until exiting the acceleration tube. DA - 2011/8// PY - 2011/8// DO - 10.13182/fst60-480 VL - 60 IS - 2 SP - 480-485 SN - 1536-1055 ER - TY - JOUR TI - Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning AU - Shi, Quan AU - Vitchuli, Narendiran AU - Nowak, Joshua AU - Caldwell, Jane M. AU - Breidt, Frederick AU - Bourham, Mohamed AU - Zhang, Xiangwu AU - McCord, Marian T2 - EUROPEAN POLYMER JOURNAL AB - Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers were prepared by atmospheric plasma treatment and electrospinning. Atmospheric helium plasma treatment was first used to reduce the AgNO3 precursor in pre-electrospinning solutions into metallic silver nanoparticles, followed by electrospinning into continuous and smooth nanofibers with Ag nanoparticles embedded in the matrix. SEM, TEM, and EDX spectra were used to study the structure and surface elemental composition of the nanofibers. Silver nanoparticles, with diameters ranging between 3 and 6 nm, were found to be uniformly dispersed in the nanofiber matrix. The Ag/PAN nanofibers exhibited slow and long-lasting silver ion release, which provided robust antibacterial activity against both Gram-positive Bacillus cereus and Gram-negative Escherichia coli microorganisms. DA - 2011/7// PY - 2011/7// DO - 10.1016/j.eurpolymj.2011.04.002 VL - 47 IS - 7 SP - 1402-1409 SN - 1873-1945 KW - Atmospheric plasma KW - Electrospinning KW - Nanofibers KW - Ag nanoparticles KW - Antibacterial activity ER - TY - JOUR TI - Detached direct numerical simulations of turbulent two-phase bubbly channel flow AU - Bolotnov, Igor A. AU - Jansen, Kenneth E. AU - Drew, Donald A. AU - Oberai, Assad A. AU - Lahey, Richard T., Jr. AU - Podowski, Michael Z. T2 - INTERNATIONAL JOURNAL OF MULTIPHASE FLOW AB - DNS simulations of two-phase turbulent bubbly channel flow at Reτ = 180 (Reynolds number based on friction velocity and channel half-width) were performed using a stabilized finite element method (FEM) and a level set approach to track the air/water interfaces. Fully developed turbulent single-phase solutions obtained previously using the same stabilized FEM code were used as the initial flow field, and an appropriate level-set distance field was introduced to represent the air bubbles. Surface tension and gravity forces were used in the simulations to physically represent the behavior of a bubbly air/water two-phase flow having a liquid/gas density ratio of 858.3. The simulation results were averaged to obtain the liquid and gas mean velocity distributions, the local void fractions as well as the local turbulent kinetic energy and dissipation rate of the liquid phase. The liquid phase parameters were compared with the corresponding single-phase turbulent channel flow to determine the bubbles’ influence on the turbulence field. DA - 2011/7// PY - 2011/7// DO - 10.1016/j.ijmultiphaseflow.2011.03.002 VL - 37 IS - 6 SP - 647-659 SN - 1879-3533 KW - Two-phase bubbly flows KW - Direct numerical simulation KW - Turbulence ER - TY - JOUR TI - Computing the viscosity of supercooled liquids: Markov network model AU - Li, J. AU - Kushima, A. AU - Eapen, J. AU - Lin, X. AU - Qian, X. F. AU - Mauro, J. C. AU - Diep, P. AU - Yip, S. T2 - PLoS One DA - 2011/// PY - 2011/// VL - 6 IS - 3 ER - TY - JOUR TI - Accuracy and borehole influences in pulsed neutron gamma density logging while drilling AU - Yu, Huawei AU - Sun, Jianmeng AU - Wang, Jiaxin AU - Gardner, Robin P. T2 - APPLIED RADIATION AND ISOTOPES AB - A new pulsed neutron gamma density (NGD) logging has been developed to replace radioactive chemical sources in oil logging tools. The present paper describes studies of near and far density measurement accuracy of NGD logging at two spacings and the borehole influences using Monte-Carlo simulation. The results show that the accuracy of near density is not as good as far density. It is difficult to correct this for borehole effects by using conventional methods because both near and far density measurement is significantly sensitive to standoffs and mud properties. DA - 2011/9// PY - 2011/9// DO - 10.1016/j.apradiso.2011.04.023 VL - 69 IS - 9 SP - 1313-1317 SN - 0969-8043 KW - Logging-while-drilling KW - Pulsed neutron gamma density log KW - Inelastic gamma-ray KW - Monte-Carlo simulation KW - Borehole influence ER - TY - JOUR TI - A self-repairing polymer waveguide sensor AU - Song, Young J. AU - Peters, Kara J. T2 - SMART MATERIALS AND STRUCTURES AB - This paper presents experimental demonstrations of a self-repairing strain sensor waveguide created by self-writing in a photopolymerizable resin system. The sensor is fabricated between two multi-mode optical fibers via lightwaves in the ultraviolet (UV) wavelength range and operates as a sensor through interrogation of the power transmitted through the waveguide in the infrared (IR) wavelength range. After failure of the sensor occurs due to loading, the waveguide re-bridges the gap between the two optical fibers through the UV resin. The response of the original sensor and the self-repaired sensor to strain are measured and show similar behaviors. DA - 2011/6// PY - 2011/6// DO - 10.1088/0964-1726/20/6/065005 VL - 20 IS - 6 SP - SN - 1361-665X ER - TY - JOUR TI - Monte Carlo modelling of gamma-ray stopping efficiencies of Geiger-Muller counters AU - Meric, I. AU - Johansen, G. A. AU - Holstad, M. B. AU - Gardner, R. P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - A detailed study of the intrinsic stopping efficiency mechanisms of low energy gamma-rays (59.5 keV) in a Geiger–Müller counter is presented. MCNP5 and PENELOPE 2006 simulations have been carried out and the simulation results have been benchmarked with experimentally obtained stopping efficiencies. The results show that the inner wall interactions are critical for the gamma-ray stopping efficiencies. DA - 2011/4/21/ PY - 2011/4/21/ DO - 10.1016/j.nima.2011.01.083 VL - 636 IS - 1 SP - 61-66 SN - 0168-9002 KW - Geiger-Muller detector KW - Monte Carlo simulation KW - Gamma-ray stopping efficiency ER - TY - JOUR TI - Limitations of Regularization Methods for the Reconstruction of Electron Velocity Distribution Function AU - El Saghir, A AU - Shannon, S T2 - IEEE Transactions on Plasma Science AB - The extraction of electron energy distribution functions (EEDFs) from Langmuir probe data is a discrete ill-posed problem. This problem rises due to the integral relationship between electron current and the probe voltage known as the Druyvesteyn relation. There have been a number of methods for the solution of this ill-posed problem ranging from data smoothing to a priori solution conditioning. Such methods include truncated singular value decomposition, truncated generalized singular value decomposition, and various regularization techniques. When these methods are extended to solve for similar integral relationships between electron current and electron distributions, complications arise due to their slightly different integral characteristics. For example, the electron velocity distribution function (EVDF) presents a similar ill-posed integral relationship. However, the EVDF integral presents an additional complication of rank deficiency that can` make accurate solutions of the inverse problem extremely challenging. In this paper, the ill-posed and rank deficiency problems of EEDF and EVDF reconstructions, respectively, are compared to highlight these challenges. DA - 2011/4// PY - 2011/4// DO - 10.1109/tps.2011.2125970 VL - 39 IS - 4 SP - 1034-1037 J2 - IEEE Trans. Plasma Sci. OP - SN - 0093-3813 1939-9375 UR - http://dx.doi.org/10.1109/TPS.2011.2125970 DB - Crossref KW - Electron energy distribution function (EEDF) KW - electron velocity distribution function (EVDF) KW - ill-posed problems KW - Tikhonov regularization ER - TY - JOUR TI - High temperature deformation characteristics of Zirlo (TM) tubing via ring-creep and burst tests AU - Seok, C. S. AU - Marple, B. AU - Song, Y. J. AU - Gollapudi, S. AU - Charit, I. AU - Murty, K. L. T2 - NUCLEAR ENGINEERING AND DESIGN AB - Abstract Fuel cladding tubing acting as a barrier between coolant and radioactive fuel pellets in light water reactors undergo a combination of mechanical and thermal effects along with corrosive conditions during normal operations as well as accident situations, such as LOCA, etc. Therefore, the mechanical integrity of the cladding tubing is of critical importance. In this study, high temperature deformation characteristics of niobium-containing zirconium alloy cladding materials (Zirlo™) have been evaluated via both ring-creep and burst tests. Creep-rupture data are presented in terms of Larson–Miller parameters (LMP). Data (creep rate vs. stress) from ring-creep and burst tests are analyzed, and operating deformation mechanisms are elucidated. This study demonstrates that the hoop creep data obtained from ring-creep and burst tests are equivalent, and one can be replaced with the other, if needed, in order to evaluate creep life. DA - 2011/3// PY - 2011/3// DO - 10.1016/j.nucengdes.2010.04.017 VL - 241 IS - 3 SP - 599-602 SN - 0029-5493 ER - TY - JOUR TI - One-step synthesis of silver nanoparticle-filled nylon 6 nanofibers and their antibacterial properties AU - Shi, Quan AU - Vitchuli, Narendiran AU - Nowak, Joshua AU - Noar, Jesse AU - Caldwell, Jane M. AU - Breidt, Frederick AU - Bourham, Mohamed AU - McCord, Marian AU - Zhang, Xiangwu T2 - JOURNAL OF MATERIALS CHEMISTRY AB - A novel and facile one-step approach to in situ synthesize silver nanoparticle-filled nylon 6 nanofibers by electrospinning is reported. The method does not need post-treatments and can be carried out at ambient conditions without using additional chemicals. It employs the electrospinning solvent as a reducing agent for in situ conversion of AgNO3 into silver nanoparticles during the solution preparation. The resultant silver nanoparticle-filled nylon 6 hybrid nanofibers show an excellent fibrous structure (fiber diameter at 50–150 nm), with narrow size 2–4 nm silver nanoparticles uniformly dispersed throughout the nylon 6 matrix. DSC analysis shows that the in situ incorporation of silver nanoparticles increased the Tg and crystallinity of the resultant nanofibers. These silver nanoparticle-filled nylon 6 nanofibers exhibit a steady and long-lasting silver ion release behavior, and robust antibacterial activity against both Gram-positive B. cereus and Gram-negative E. coli microorganisms. DA - 2011/// PY - 2011/// DO - 10.1039/c1jm11492a VL - 21 IS - 28 SP - 10330-10335 SN - 1364-5501 ER - TY - JOUR TI - PHOTON BUILDUP FACTORS IN LAMINATED DUAL-LAYER SHIELDS AU - Davis, Adam AU - Dudziak, Donald J. AU - Yim, Man-Sung AU - McNelis, David AU - Wooten, H. Omar T2 - NUCLEAR TECHNOLOGY AB - In radiation protection, photon buildup factors provide a convenient method for calculating dose and exposure response after various shielding configurations, as well as information about the behavior of radiation in these configurations. Though many situations call for multilayer shields, few databases and derived analytical formulas for photon buildup in multilayer shields exist. This research develops buildup factors and analytical fits to these data for slab-geometric, dual-layer shields composed of various materials. The photon buildup factors were calculated for monoenergetic photon sources incident on two-layer shields of various combinations of lead, polyethylene, aluminum, and stainless steel for thicknesses varying between 2 and 20 mean free paths using the Parallel Time Independent Sn (PARTISN) discrete ordinates code. The Gauss-Lobatto S100 quadrature was used with a 244-energy-group structure and coupled photon and electron cross sections. Data from PARTISN calculations were then benchmarked for representative cases using MCNP5, and fits to a new analytical formula were developed using Mathematica 6.0. DA - 2011/3// PY - 2011/3// DO - 10.13182/nt11-110 VL - 173 IS - 3 SP - 270-288 SN - 1943-7471 KW - radiation shielding KW - multilayered shields KW - buildup factors ER - TY - JOUR TI - Reduction of EEDF Measurement Distortion in Regularized Solutions of the Druyvesteyn Relation AU - El Saghir, Ahmed AU - Shannon, Steven T2 - IEEE Transactions on Plasma Science AB - Electron energy distribution function (EEDF) extraction from Langmuir probe data is an ill-posed problem due to the integral relationship between electron current and probe voltage. Both curve fitting of experimental data and reconstruction of the integral problem through methods, such as Tikhonov regularization, address this to some measure, with regularized solutions offering an advantage in overall EEDF accuracy over curve fitting. Although Tikhonov regularization provides a more accurate estimation of EEDF overall energy space, it typically also can distort the overall shape of the reconstructed distribution, particularly at high energies and energies below the distribution peak. This, combined with the relative ease of use that simple data smoothing algorithms provide, has limited the use of the more advanced reconstruction algorithms in EEDF analysis. In this paper, we will shed some light on these limitations and offer an alternative method to overcome these limitations. DA - 2011/1// PY - 2011/1// DO - 10.1109/tps.2010.2090906 VL - 39 IS - 1 SP - 596-602 J2 - IEEE Trans. Plasma Sci. OP - SN - 0093-3813 1939-9375 UR - http://dx.doi.org/10.1109/TPS.2010.2090906 DB - Crossref KW - Electron energy distribution function (EEDF) KW - ill-posed problems KW - Tikhonov regularization KW - truncated singular value decomposition (TSVD) ER - TY - JOUR TI - A simplified methodology for nuclear waste repository thermal analysis AU - Li, J. AU - Yim, M. S. AU - McNeils, D. T2 - Annals of Nuclear Energy DA - 2011/// PY - 2011/// VL - 38 IS - 2-3 SP - 243-253 ER - TY - JOUR TI - Newton's Method for Solving k-Eigenvalue Problems in Neutron Diffusion Theory AU - Gill, Daniel F. AU - Azmy, Yousry Y. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - We present an approach to the k-eigenvalue problem in multigroup diffusion theory based on a nonlinear treatment of the generalized eigenvalue problem. A nonlinear function is posed whose roots are equal to solutions of the k-eigenvalue problem; a Newton-Krylov method is used to find these roots. The Jacobian-vector product is found exactly or by using the Jacobian-free Newton-Krylov (JFNK) approximation. Several preconditioners for the Krylov iteration are developed. These preconditioners are based on simple approximations to the Jacobian, with one special instance being the use of power iteration as a preconditioner. Using power iteration as a preconditioner allows for the Newton-Krylov approach to heavily leverage existing power method implementations in production codes. When applied as a left preconditioner, any existing power iteration can be used to form the kernel of a JFNK solution to the k-eigenvalue problem. Numerical results generated for a suite of two-dimensional reactor benchmarks show the feasibility and computational benefits of the Newton formulation as well as examine some of the numerical difficulties potentially encountered with Newton-Krylov methods. The performance of the method is also seen to be relatively insensitive to the dominance ratio for a one-dimensional slab problem. DA - 2011/2// PY - 2011/2// DO - 10.13182/nse09-98 VL - 167 IS - 2 SP - 141-153 SN - 0029-5639 ER - TY - JOUR TI - Atmospheric Plasma Treatment of Pre-Electrospinning Polymer Solution: A Feasible Method to Improve Electrospinnability AU - Shi, Quan AU - Vitchuli, Narendiran AU - Nowak, Joshua AU - Lin, Zhan AU - Guo, Bingkun AU - McCord, Marian AU - Bourham, Mohamed AU - Zhang, Xiangwu T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Abstract The electrospinnability of polyethylene oxide (PEO) was manipulated by atmospheric plasma treatment of pre‐electrospinning solutions. Conductivity, viscosity, and surface tension of PEO solutions increased after plasma treatment, and the plasma effect remained longer when the solution concentrate increased. Both untreated and treated solutions were then electrospun, and the morphology of the resultant nanofibers was observed by SEM. Atmospheric plasma treatment improved the electrospinnability of PEO solutions and led to less beads and finer diameter distribution in the resultant nanofibers. Additionally, plasma treatment of the pre‐electrospinning solutions affected the crystal structure of resultant nanofibers. These results suggest that atmospheric plasma treatment is a feasible approach to improve the electrospinnability of polymer solutions and can used to control the structure of electrospun nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 DA - 2011/1/15/ PY - 2011/1/15/ DO - 10.1002/polb.22157 VL - 49 IS - 2 SP - 115-122 SN - 1099-0488 KW - atmospheric plasma KW - electrospinning KW - fibers KW - melting point KW - nanofibers KW - poly(ethylene oxide) ER - TY - JOUR TI - A Facile Approach to Fabricate Porous Nylon 6 Nanofibers Using Silica Nanotemplate AU - Shi, Quan AU - Vitchuli, Narendiran AU - Ji, Liwen AU - Nowak, Joshua AU - McCord, Marian AU - Bourham, Mohamed AU - Zhang, Xiangwu T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Porous Nylon 6 nanofibers were prepared using silica nanoparticles as the template. Firstly, Nylon 6/silica composite nanofibers were prepared as precursors by electrospinning Nylon 6 solutions containing different contents of silica nanoparticles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the surface morphology and the inner structure of composite nanofibers; where it was found that silica nanoparticles were distributed both inside and on the surface of nanofibers. Analytical techniques [Fourier transform infrared (FTIR), differential scanning calorimetry, thermal gravimetric analysis (TGA), and wide‐angle X‐ray diffraction) were used to study the structure and properties of these composite nanofibers. The glass transition, melting, and crystallization processes of the fibers were affected by the addition of silica nanoparticles. Secondly, porous Nylon 6 nanofibers were obtained by removing silica nanoparticles via hydrofluoric acid treatment. The removal of silica nanoparticles was confirmed using FTIR and TGA tests. SEM and TEM observations revealed the formation of the porous structure in these nanofibers. After the formation of the porous structure, Brunauer–Emmett–Teller specific surface areas of nanofibers were increased as compared to solid Nylon 6 and composite nanofibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 DA - 2011/4/5/ PY - 2011/4/5/ DO - 10.1002/app.33161 VL - 120 IS - 1 SP - 425-433 SN - 1097-4628 KW - electrospinning KW - nanocomposite KW - porous nanofibers KW - Nylon 6 ER -