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791.
792.
Pengyi Zhang Bo Zhang Rui Shi 《Frontiers of Environmental Science & Engineering in China》2009,3(3):281-288
Highly dispersed gold nanoparticles were supported on coal-based activated carbon (AC) by a sol immobilization method and
were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature. Nitrogen adsorption-desorption,
scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts before
and after ozone decomposition. The results showed that the supported gold nanoparticles prepared with microwave heating were
much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating,
exhibiting higher catalytic activity for ozone decomposition. The pH values of gold precursor solution significantly influenced
the catalytic activity of supported gold for ozone decomposition, and the best pH value was 8. In the case of space velocity
of 120000 h−1, inlet ozone concentration of 50 mg/m3, and relative humidity of 45%, the Au/AC catalyst maintained the ozone removal ratio at 90.7% after 2500 min. After being
used for ozone decomposition, the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly,
while its specific surface area and pore volume only decreased a little. Ozone was mainly catalytically decomposed by the
gold nanoparticles supported on the activated carbon. 相似文献
793.
文章以太原市机动车排放的实际数据结合气象因素与街道构造,采用OSPM模型计算了2008年太原市夏季(7月)与冬季(12月)车流量高峰期街道内的一次NOx与CO的小时浓度,验证了适用性,并使用模型对太原市55条主干道进行了扩散模拟计算,结果表明:OSPM模型可以较好地模拟太原市NOx与CO的扩散;太原市冬季交通大气污染物浓度要明显高于夏季;从空间分布上来看,污染物浓度基本与车流量分布一致;对比国家大气二级环境质量标准来看,太原市主干道NOx超标较为严重,夏季达到了83.64%,冬季达到了98.18%;夏季CO浓度计算结果全部在二级标准限值内,冬季超标率为16.36%。 相似文献
794.
795.
Xiaoyan Shi Kebin He Jie Zhang Yongliang Ma Yunshan Ge Jianwei Tan 《Frontiers of Environmental Science & Engineering in China》2010,4(1):30-34
Oxygenated fuels are known to reduce particulate matter (PM) emissions from diesel engines. In this study, 100% soy methyl
ester (SME) biodiesel fuel (B100) and a blend of 10% acetal denoted by A-diesel with diesel fuel were tested as oxygenated
fuels. Particle size and number distributions from a diesel engine fueled with oxygenated fuels and base diesel fuel were
measured using an Electrical Low Pressure Impactor (ELPI). Measurements were made at ten steady-state operational modes of
various loads at two engine speeds. It was found that the geometric mean diameters of particles from SME and Adiesel were
lower than that from base diesel fuel. Compared to diesel fuel, SME emitted more ultra-fine particles at rated speed while
emitting less ultra-fine particles at maximum speed. Ultra-fine particle number concentrations of A-diesel were much higher
than those of base diesel fuel at most test modes. 相似文献
796.
为探究花岗岩风化形成的风化球孤石对边坡稳定性及破坏特征的影响,利用摄影测量和数字图像处理技术,对大量的孤石进行拍照及处理,建立大量具有各种形状的孤石模型,从所建立的孤石模型中选取具有不同形状参数的孤石,将其导入ABAQUS软件,建立含有孤石的边坡模型,进行有限元强度折减分析。结果表明:孤石的位置和大小会对边坡的安全系数产生规律性影响,而孤石的形状对边坡安全系数的影响表现出不确定性;孤石对边坡破坏特征产生影响,塑性应变区发展过程及位移场分布在孤石处与均质边坡相比均有较大变化。 相似文献
797.
火灾环境下高温对结构钢材的力学性能具有显著的不利影响.通常钢材在200~400℃的温度下力学性能开始下降,在800℃以上几乎丧失所有的强度.火灾环境下的钢结构力学响应行为是钢结构抗火设计的前提.为了展示火灾环境下钢结构的力学响应研究的清晰脉络,首先综述了火灾环境工况加载、钢结构升温规律的研究文献,然后从钢的耐火性能分析开始,评述了钢结构形式对耐火性能的影响和热作用下的结构变形研究.研究表明:若采用ISO 834标准升温曲线作为热加载方式,钢结构的升温规律和力学响应行为与真实火灾场景下相比差异显著,在标准火下钢的抗火时间更长;钢结构在火灾环境下的热应变随温度升高而增大,最终导致屈曲和过度挠度;当温度超过400℃时,高温蠕变会加速结构的失效;试验和数值模拟方法能很好地预测钢结构在真实火灾环境下的温升规律;较为真实地表征钢结构的不均匀力学响应行为,首先需要加载真实的火灾工况,同时要充分考虑钢结构形式,并耦合运用工程热物理、力学相关工具和方法;钢附着可燃材料燃烧的热反馈及相应的力学响应行为是钢结构抗火研究的新问题,针对该问题需要建立科学的热-力耦合工程定量测试方法. 相似文献
798.
油田修井作业井场传统的照明灯,一般是交流220 V大功率白炽灯泡或普通探照灯,这种传统的照明灯,为油田的修井作业井场照明发挥了作用,但其存在着亮度差、照射方位及角度有限、移动不便、安全性能差和耗电大的缺陷. 相似文献
799.
800.
Evaluation of the infectivity, gene and antigenicity persistence of rotaviruses by free chlorine disinfection 总被引:1,自引:0,他引:1
The effects of free chlorine disinfection of tap water and wastewater effluents on the infectivity, gene integrity and surface antigens of rotaviruses were evaluated by a bench-scale chlorine disinfection experiments. Plaque assays, integrated cell culture-quantitative RT-PCR (ICC-RT-qPCR), RT-qPCR, and enzyme-linked immunosorbent assays (ELISA), respectively, were used to assess the influence of the disinfectant on virus infectivity as well as genetic and antigenic integrity of simian rotavirus SA11 as a surrogate for human rotaviruses. The ICC-RT-qPCR was able to detect rotaviruses survival from chlorine disinfection at chlorine dose up to 20 mg/L (60 min contact), which suggested a required chlorine dose of 5 folds (from 1 to 5 mg/L) higher than that indicated by the plaque assay to achieve 1.8 log10 reductions in tap water with 60 min exposing. The VP7 gene was more resistant than the infectivity and existed at chlorine dose up to 20 mg/L (60 min contact), while the antigencity was undetectable with chlorine dose more than 5 mg/L (60 min contact). The water quality also impacted the inactivation efficiencies, and rotaviruses have a relatively higher resistant in secondary effluents than in the tap water under the same chlorine disinfection treatments. This study indicated that rotaviruses have a higher infectivity, gene and antigencity resistance to chlorine than that previously indicated by plaque assay only, which seemed to underestimate the resistance of rotaviruses to chlorine and the risk of rotaviruses in environments. Present results also suggested that re-evaluation of resistance of other waterborne viruses after disinfections by more sensitive infectivity detection method (such as ICC-RT-qPCR) may be necessary, to determine the adequate disinfectant doses required for the inactivation of waterborne viruses. 相似文献