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排序方式: 共有861条查询结果,搜索用时 10 毫秒
61.
Gamma irradiation of pharmaceutical compounds, nitroimidazoles, as a new alternative for water treatment 总被引:4,自引:0,他引:4
M. Sánchez-Polo 《Water research》2009,43(16):4028-8
The main objectives of this study were: (1) to investigate the decomposition and mineralization of nitroimidazoles (Metronidazole [MNZ], Dimetridazole [DMZ], and Tinidazole [TNZ]) in waste and drinking water using gamma irradiation; (2) to study the decomposition kinetics of these nitroimidazoles; and (3) to evaluate the efficacy of nitroimidazole removal using radical promoters and scavengers. The results obtained showed that nitroimidazole concentrations decreased with increasing absorbed dose. No differences in irradiation kinetic constant were detected for any nitroimidazole studied (0.0014-0.0017 Gy−1). The decomposition yield was higher under acidic conditions than in neutral and alkaline media. Results obtained showed that, at appropriate concentrations, H2O2 accelerates MNZ degradation by generating additional HO; however, when the dosage of H2O2 exceeds the optimal concentration, the efficacy of MNZ degradation is reduced. The presence of t-BuOH (HO radical scavenger) and thiourea (HO, H and eaq− scavenger) reduced the MNZ irradiation rate, indicating that degradation of this pollutant can take place via two pathways: oxidation by HO radicals and reduction by eaq− and H. MNZ removal rate was slightly lower in subterranean and surface waters than in ultrapure water and was markedly lower in wastewater. Regardless of the water chemical composition, MNZ gamma irradiation can achieve i) a decrease in the concentration of dissolved organic carbon, and ii) a reduction in the toxicity of the system with higher gamma absorbed dose. 相似文献
62.
Magaly Caillon-Caravanier Jennifer Jones Frédéric Montigny Jean-Pierre David Daniel Lemordant 《Journal of power sources》2010,195(2):614-620
Lithium-ion batteries for space applications, such as satellites, are subjected to cosmic radiations, in particular, γ-irradiation. In this study, the effects of this radiation on electrolytes and their components used in the lithium-ion batteries are investigated. The conductivity and viscosity of the samples have been measured before and after the irradiation. The modifications are evaluated by spectral analyses such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H and 13C NMR), solid phase microextraction-gas chromatography (SPME-GC) and gas chromatography-mass spectroscopy (GC-MS). The experimental results show that only the samples containing vinylene carbonate and/or the lithium salt LiPF6 are degraded by γ-radiation. 相似文献
63.
Summary This paper is concerned with business mortality analysis in a Bayesian setting. We assume that a businessman startsN businesses at different points of time and at a certain epoch referred to as the ‘present’, the failure times of the failed
businesses and the survival times of the still surviving businesses are recorded. Bayesian prediction for business mortality
or survival up to a future time pointt
0 is made under the assumptions of a Weibull business survival distribution (WBSD) and the squared error loss function (SELF).
The results are extended to the situation where one of the observed times of business failure may possibly be an outlier. 相似文献
64.
溅水问题的试验研究与随机模拟 总被引:1,自引:0,他引:1
通过水力学试验,对于水舌撞击尾水形成的溅水分布进行研究,并运用随机溅水数值模型进行计算验证.研究结果表明,下游溅水区在水舌风的拖曳作用下,在平面上呈三角形分布,而降雨强度的纵向分布则符合伽玛函数形式.运用随机溅水模型得到的降雨强度分布与试验数据甚为吻合,证明该数值方法可以较好地模拟溅水雾化现象,具有较好的应用前景. 相似文献
65.
Optical and FT infrared spectral properties of tungsten ions in a host lead borate glass with composition PbO 55%, B2O3 45% (wt%) were studied. The same spectral properties were re-measured after subjecting the samples to successive gamma irradiation. The work was undertaken to justify the state of tungsten ions in such glass system by combined spectral investigations. Optical and FTIR spectral studies were confirmed by investigating electron spin resonance (ESR) of the undoped and WO3-doped samples before and after gamma irradiation. The optical spectrum of the undoped glass exhibits strong and wide UV absorption bands, which are related to the combined UV spectra of trace iron impurities (Fe3+ ions) and that from divalent lead (Pb2+) ions. Optical studies of WO3-doped sample indicate the presence of tungsten ions mostly in the hexavalent W6+ state. The presence of tungsten ions as structural groups was obtained by comparing the FTIR spectra of the undoped and WO3-doped samples. ESR spectra confirm the optical and FTIR spectral studies. The studied host lead borate glass has been found to show obvious shielding behavior towards successive gamma irradiation as revealed by the constancy of optical absorption spectral curves. 相似文献
66.
Polymers used to package food intended for irradiation must currently receive separate US FDA approvals for e-beam, gamma and X-radiation. The three forms of irradiation have virtually indistinguishable effects on polymers held in vacuum. However, in air, irradiation damage is favoured by slow dose rates, such as that characteristic of gamma irradiation. Irrespective of irradiation type, theory and existing polymer irradiation literature both suggest that radiolytic products in food contact polymers should not present a health hazard due to migration into the foods they contain. Equations are presented which calculate the FDA allowable content of radiolytic products to achieve 'threshold of regulation' clearance and conversion of radiolytic yield values (G-values) into ppb concentration in the treated polymer in conformance with FDA practice. An approach to quantifying the functional barrier of a polymer is discussed. 相似文献
67.
Gamma processes and peaks-over-threshold distributions for time-dependent reliability 总被引:2,自引:0,他引:2
J.M. van Noortwijk J.A.M. van der Weide M.J. Kallen M.D. Pandey 《Reliability Engineering & System Safety》2007,92(12):1651-1658
In the evaluation of structural reliability, a failure is defined as the event in which stress exceeds a resistance that is liable to deterioration. This paper presents a method to combine the two stochastic processes of deteriorating resistance and fluctuating load for computing the time-dependent reliability of a structural component. The deterioration process is modelled as a gamma process, which is a stochastic process with independent non-negative increments having a gamma distribution with identical scale parameter. The stochastic process of loads is generated by a Poisson process. The variability of the random loads is modelled by a peaks-over-threshold distribution (such as the generalised Pareto distribution). These stochastic processes of deterioration and load are combined to evaluate the time-dependent reliability. 相似文献
68.
快中子脉冲反应堆厅内空气中裂变产物污染的研究 总被引:1,自引:1,他引:0
本文研究了快中子脉冲反应堆大厅内空气中裂变产物的污染问题。通过对CFBR-Ⅱ快中子脉冲反应堆爆发额定产额脉冲(1.53×1016裂变)后,厅内气溶胶的取样和γ谱分析,确定了裂变产物从黄铜壳内空气中释放到厅内空气中形成气溶胶的释放份额为5×10-3。利用此释放份额计算了厅内空气中不同放射性核素的气溶胶浓度;还计算了该堆爆发额定产额脉冲后不同冷却时间t厅内空气中无分凝混合裂变产物的导出空气浓度DAC(t)值,为该堆辐射安全分析和现场辐射防护提供了依据。 相似文献
69.
Hyun-Joo Ahn Jae-Hyun Kim Cheorun Jo Hong-Sun Yook Hyun-Ja Lee Myung-Woo Byun 《Food Control》2003,14(8):553-557
Salted and fermented anchovy sauce spiked with or without N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) was irradiated at 0, 5, 10, 15 and 20 kGy. NDMA and NPYR reduction by irradiation was not observed in non-spiked samples at 0 week, while a significant reduction was observed after 4 weeks of storage at 15 °C (P<0.05). In N-nitrosamine spiked samples, a positive effect of irradiation on NDMA and NPYR reduction was observed. NDMA and NPYR levels were decreased by irradiation at 5 kGy or above after storage. Therefore, gamma irradiation has a possibility to reduce N-nitrosamines in salted and fermented anchovy sauce. 相似文献
70.
Dale E. Alexander 《Journal of Nuclear Materials》1997,240(3):196-204
Motivated by the recent interest in gamma ray embrittlement of nuclear reactor pressure vessels (RPVs), calculations were performed to evaluate aspects of defect production by gammas in iron and steel. In addition to determining displacement damage cross-sections, the atomic recoil energy dependence of gamma-induced defect production was described by integral recoil damage spectra, W(T), and their associated median recoil damage energies, T1/2. These latter characterizations, should be particularly useful in evaluating the contribution of gamma ray generated defects to microstructural changes causing radiation embrittlement. The results for monoenergetic gammas, as well as for gamma rays with a spectrum of energies characteristic of a RPV, reveal T1/2 values of <100 eV, about three orders of magnitude smaller than for fast-neutrons, the radiation of primary concern in previous embrittlement studies. The relative contributions of various gamma interactions to defect production, as well as the role of light alloy element-induced secondary displacement mechanisms, are also considered. 相似文献