管道环焊接头残余应力及氢扩散模拟研究

为减小氢气对管道的安全服役产生威胁,研究考虑焊接残余应力对氢在焊接接头中扩散的影响,建立管道3层环向对接焊的三维模型.通过顺序间接耦合方法,对管道焊接的温度场、应力场以及氢扩散进行耦合计算,研究结果表明:第2层焊缝与第3层焊缝交界处为整个接头的应力集中部位,也是焊接接头中的富氢区域,适当地提高填充焊线能量或者降低盖面焊...     

A study on emission performance of a diesel engine fueled with five typical methyl ester biodiesels

As an alternative and renewable fuel, biodiesel can effectively reduce diesel engine emissions, especially particulate matter and dry soot. However, the biodiesel effects on emissions may vary as the source fuel changes. In this paper, the performance of five methyl esters with different sources was studied: cottonseed methyl ester (CME), soybean methyl ester (SME), rapeseed methyl ester (RME), palm oil methyl ester (PME) and waste cooking oil methyl ester (WME). Total particulate matter (PM), dry soot (DS), non-soot fraction (NSF), nitrogen oxide (NO_x), unburned hydrocarbon (HC), and carbon monoxide (CO) were investigated on a Cummins ISBe6 Euro III diesel engine and compared with a baseline diesel fuel. Results show that using different methyl esters results in large PM reductions ranging from 53% to 69%, which include the DS reduction ranging from 79% to 83%. Both oxygen content and viscosity could influence the DS emission. Higher oxygen content leads to less DS at high load while lower viscosity results in less DS at low load. NSF decreases consistently as cetane number increases except for PME. The cetane number could be responsible for the large NSF difference between different methyl esters.     

Effects of phenanthrene on the mortality, growth, and anti-oxidant system of earthworms (Eisenia fetida) under laboratory conditions

To assess the toxic effects of phenanthrene on earthworms, we exposed Eisenia fetida to artificial soils supplemented with different concentrations (0.5, 2.5, 12.5, mgkg(-1) soil) of phenanthrene. The residual phenanthrene in the soil, the bioaccumulation of phenanthrene in earthworms, and the subsequent effects of phenanthrene on growth, anti-oxidant enzyme activities, and lipid peroxidation (LPO) were determined. The degradation rate of low concentrations of phenanthrene was faster than it was for higher concentrations, and the degradation half-life was 7.3d (0.5 mgkg(-1)). Bioaccumulation of phenanthrene in the earthworms decreased the phenanthrene concentration in soils, and phenanthrene content in the earthworms significantly increased with increasing initial soil concentrations. Phenanthrene had a significant effect on E. fetida growth, and the 14-d LC(50) was calculated as 40.67 mgkg(-1). Statistical analysis of the growth inhibition rate showed that the concentration and duration of exposure had significant effects on growth inhibition (p<0.001). Superoxide dismutase (SOD) activity increased at the beginning (2 and 7d) and decreased in the end (14 and 28 d). Catalase (CAT) activity in all treatments was inhibited from 1 to 14 d of exposure. However, no significant perturbations in malondialdehyde (MDA) content were noted between control and phenanthrene-treated earthworms except after 2d of exposure. These results revealed that bioaccumulation of phenanthrene in E. fetida caused concentration-dependent, sub-lethal toxicity. Growth and superoxide dismutase activity can be regarded as sensitive parameters for evaluating the toxicity of phenanthrene to earthworms.     

基于超效率DEA模型的中国能源效率测算与实证研究

随着城市化和工业化进程的加快,在能源需求量日益扩大的同时,二氧化碳排放量也快速增长,中国面临着越来越严峻的能源和环境形势。为了实现“十二五”规划节能减排目标及2030 年实现碳峰值的承诺,提高能源效率和碳减排成为了我国经济发展的当务之急。本文选取与能源效率存在密切关系的产业结构、技术进步、能源消费结构和经济发展水平作为主要影响因素,基于超效率DEA 模型对中国1980-2011 年的能源效率进行了测算,利用VEC 模型分析发现能源效率与产业结构、技术进步、能源消费结构和经济发展水平之间存在长期的协整关系;同时,在此基础上利用脉冲响应函数和方差分解模型就我国能源效率与其影响因素之间的短期动态关系作进一步分析,结果显示,产业结构、能源消费结构、技术进步对能源效率得提升有积极的正效应,而经济发展水平对其有一定的负面影响,从各因素对能源效率的贡献百分比来看, 产业结构比例对能源效率的贡献最大, 然后依次是经济发展水平、能源消费结构和技术进步。最后结合以上分析,从加大研发收入、调整产业结构、优化能源消费结构、提升技术利用水平、发展清洁能源技术、推广新能源使用与技术扩散能方面提出了可行性建议与对策。     

基于生态服务功能价值的水库工程生态补偿研究

生态补偿是环境管理的一种经济手段，它通过调节人类生产生活行为来达到生态环境保护的目的。生态补偿标准的确定在实践中常是产生争议的关键．本文以厦门市莲花水库工程生态补偿为饲．选择生态服务功能价值计算方法确定生态补偿标准。结果表明厦门市莲花水库运行期生态服务功能价值为12858．27万元，由此确定生态补偿费额度，并通过政府补贴和征收附加水费两种方式获得。     

满足重型柴油机超低排放法规的后处理技术现状与展望

柴油机排放污染物控制是全球应对大气环境恶化问题的重要解决方案之一。美国加利福尼亚州在2019年率先发布了针对超低排放要求的白皮书,建议将重型柴油机的NO_x排放继续降低90%,即最低达到0.027 g/（kW·h）。针对未来超低排放法规的技术要求,全球相关机构开展了大量的研发和试验工作,有效推动了排放控制技术的升级。从发动机后处理零部件的角度,总结了国内外相关文献及研究成果,提出发动机和后处理技术需联动升级,在加强发动机热管理的同时,降低原机NO_x排放。重点介绍了潜在的后处理技术解决方案,如NO_x吸附脱附技术和紧耦合SCR技术等控制低温NO_x排放的关键技术,灰分管理和PN控制相关的DPF控制技术,以及电加热催化器和燃烧器等可能应用于后处理系统的热管理技术,并对相关技术的优劣势进行了分析。     

移动通信基站电磁辐射实例分析

随着移动通信技术的发展，基站的电磁辐射受到越来越多的关注。本文介绍了分析移动通信基站的电磁辐射情况预测模型，结合天线的方向性和增益情况对不同地区不同辐射方向上的电磁辐射情况做出预测并与实测数据进行比较分析。     

Water resource system risk and adaptive management of the Chinese Heihe River Basin in Asian arid areas

Mitigation and Adaptation Strategies for Global Change - Water scarcity is a challenging environmental problem in global arid regions in the twenty-first century. Global climate change and urban...     

易挥发类危险废物道路运输环境风险分析与度量

危险废物的道路运输过程中会产生风险,其风险的主要影响对象是环境,本文主要研究易挥发性液体危险废物,分析并度量其在道路运输中对环境造成的风险。首先,以环境承载力理论为基础,结合道路运输区域环境系统的环境容量与危险废物的危险特性,定义危险废物道路运输的环境风险;其次,根据定义建立危险废物道路运输的环境风险度量模型;最后,通过算例演算论证模型的可行性,并表明其结论可供危险废物运输企业和相关环保部门进行决策辅助分析。     

基于AHP的大庆海外石油钻探项目风险评价指标体系研究

我国石油企业在承揽海外石油钻探项目的过程中,为确保工程能顺利进行,需要进行风险预警管理。基于150份完整有效的调查问卷数据,以大庆海外石油钻探项目风险管理为研究对象,采用文献查阅法、问卷调查法、德尔菲法专家法、AHP层次分析法等研究方法,对大庆海外石油钻探项目的风险预警管理进行了研究,构建了海外石油钻探项目的风险评价指标体系。研究表明:政治经济风险对海外石油钻探项目影响最大,社会文化风险影响最小;政治经济风险中,经济风险的影响远大于政治风险的影响;财务风险中,与获利相关的直接风险大于间接风险;地质条件工程与技术风险中,地质条件风险大于技术风险;社会文化风险中,与东道国语言差异造成的风险影响最大。最后,提出了相应地对策建议。