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921.
This study is to examine the contribution of socioeconomic status (SES) to the risk of nonfatal pedestrian injury among children. The sample was obtained from two urban cities of China using multi-staged randomized sampling. Information was collected by respondents’ reporting using self-administrative way in the classroom under the guidance of interviewers. A logistic regression analysis was applied to examine the associations between SES and nonfatal children pedestrian injury. The results showed that boys and children aged 10 had significantly increased odds of suffering nonfatal pedestrian injury. Migrant children were at higher risk of being injured. Students whose mothers’ educational levels were either less than secondary school or postgraduate were more likely to sustain injury. Children who were from wealthier families or poorer families easily suffered from injury compared to children from middle families. Children living with grandparents, or siblings, or a single father, or a single mother were all at increased risk of injury. The possible causes or pathways of these SESs’ impacts on pedestrian injury were explored in discussion. This study suggests that SESs are important determinants of nonfatal pedestrian injury among children in China. 相似文献
922.
为了揭示山区服役环境下材料性能劣化对桥梁抗震安全性的影响,根据混凝土碳化和钢筋锈蚀规律得到山区环境下材料劣化时变模型,采用基于需求能力比(D/C)的动力增量分析(IDA)方法,提出了桥梁时变地震易损性分析流程。围绕某山区典型高墩刚构桥,研究了桥梁构件和体系两个层次的地震易损性时变规律。结果表明:构件塑性发展程度越高,材料劣化的影响越不利,构件曲率延性系数也越大;相比于横桥向,材料劣化对构件纵向地震易损性的影响更大,且服役时间越长,构件地震损伤概率越高;桥梁体系的损伤概率上限高于任意构件,材料劣化的不利影响也主要体现于纵桥向,该方向上 0.8g 时,服役 100 年的严重受损概率相比新桥增大 100.86%;材料劣化对桥梁地震易损性的影响不容忽视,且构件层面的易损性评估不足以反映桥梁体系的易损性。 相似文献
923.
几种模拟处理方式污泥淋出液重金属与养分特征 总被引:2,自引:0,他引:2
为了减少城市污泥重金属对农田的污染,更好地实现污泥农业资源化利用,通过盆栽实验研究不同处理(对照、黑网、附Fe黑网、附Fe黑网+K2SO4及附Fe黑网+玉米)对城市污泥淋出液重金属和养分含量等的影响。结果表明,黑网可降低污泥淋出液的Zn﹑Cd总量,且没有减少污泥淋出液中氮、磷和钾的总量。Fe(OH)3可使淋出液中Zn总量降低,但同时也显著减少了淋出液中的磷总量。K2SO4可降低淋出液中的Cu总量,且促进Fe结合磷的释放。玉米的种植可使污泥的总重降低,同时玉米籽粒和茎叶重金属含量达到饲料标准。综合来看,任何处理每次淋出液的Cu、Zn、Pb、Cd浓度均符合农田灌溉水标准,淋出液氮、磷、钾量占原污泥中氮、磷、钾总量的比例(0.98%~9.88%)远远大于重金属元素(Cu,Zn,Pb,Cd)占原污泥对应重金属总量的比例(0.04%~0.41%),污泥淋出液作为农田灌溉水进行肥水利用将是污泥农业资源化利用的适合途径,同时黑网+玉米处理可能是较理想的污泥综合处理利用方式。 相似文献
924.
电除尘器进气烟箱参数对气流分布影响的仿真研究 总被引:2,自引:1,他引:1
电除尘器进气烟箱结构参数不仅对除尘器内部气流分布的均匀性产生重要影响,而且还会影响除尘效率和排放指标。针对电除尘器进气烟箱结构参数选取与气流分布均匀性问题,采用欧拉-拉格朗日多相流模型,对进气烟箱扩散角,气流分布板孔形、开孔率和导流板角度等参数,进行了三维流场模拟仿真计算,获得各参数对气流均匀性的影响关系规律。仿真结果表明:方形孔的气流分布板能获得较佳的气流分布均匀性;合理调节进气烟箱扩散角、开孔率和导流板角度可有效地改善电场内气流分布状况。研究结果可为电除尘器进气烟箱的设计与改进提供依据。 相似文献
925.
Shexia Ma Ping’an Peng Jianzhong Song Xinhui Bi Jinping Zhao Lulu He Guoying Sheng Jiamo Fu 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5460-5467
The concentrations and compositions of free and bound organic acids in total suspended particles from typical urban, suburban and forest park sites of Guangzhou were determined in this study. The free form of organic acids (solvent extractable) in aerosols in Guangzhou varied with site and season. The suburban samples contained the highest contents of alkanoic, alkenoic and dicarboxylic acids. These findings were consistent with a higher supply of hydrocarbons and NOx in the suburban area. However, concentrations of aromatic acids were similar in the urban, suburban and forest park sites. Generally, winter season samples of the acids from anthropogenic sources contained more organic acids than summer season samples due to stronger removal by wet deposition in the summer. For the acids from botanic sources, the summer season samples were higher. In addition to the free acids, bound acids (solvent non-extractable) mainly formed by esterification of free acids were also found in the samples. In general, bound acids were higher than free acids. Esterification is mainly controlled by the pKa of organic acids and the atmospheric pH value. This explains why aromatic and dicarboxylic acids occur mainly as bound forms and why the samples from urban sites contained high levels of bound acids as the pH of rain water can reach 4.53.Concentrations of alkanoic and alkenoic acids in the aerosols of Guangzhou were much higher than those in the other areas studied. 相似文献
926.
927.
928.
929.
Introduction Environm ental and econom ic advantages highlight anaerobic digestion as a sustainable technology for solid w aste treatm ent (Edelm ann etal., 2000). A naerobic digestion could be described as four sequential steps: hydrolysis, acidogenesis, aceto- genesis and m ethanogenesis, am ong w hich the hydrolysis is recognized as the rate-lim iting step for particulate organic w aste (Jain et al., 1992; M ata-A lvarez, 2000). H ydrolysis occurs com m only together w ith the acidogenesi… 相似文献
930.