从全混流反应器热稳定性的角度探讨高危工艺的危险性

通过对全混流反应器(CSTR)热平衡条件下多态的分析,探讨热稳定性条件,并对一级不可逆反应在CSTR中的热稳定性进行定性分析;探讨不同反应热和活化能对反应过程热稳定性的影响,及其对反应器发生"飞温"事故要求紧急停车时的控制要求的影响,进而从反应工程的角度对高危工艺的界定提出新的思路。分析结果表明,工艺的危险性不仅与工艺的种类相关,更与工艺本身的热力学、动力学特征密切相关。通过对高危工艺的热稳定状况的分析,能够动态地揭示其在温度扰动下发生"飞温"或"熄火"的过程,从本质上把握高危工艺潜在的危险性,并能有针对性地制定自动化改造方案,提高化工企业的本质安全度。     

火电厂烟气在线监测系统存在的主要问题及进一步加强在线监测工作的建议

火电厂燃煤过程排放的污染物是我国大气污染的主要来源之一,烟气排放连续监测系统(CEMS)是实现烟气排放连续监测有效的现代化仪器设备。介绍了目前我国火电厂烟气的CEMS主要存在的问题,并针对这些存在的问题提出了相应的解决方案。     

Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species

2,4,6-Trichlorophenol (2,4,6-TCP) is a common chemical intermediate and a by-product of water chlorination and combustion processes, and is a priority pollutant of the aquatic environment in many countries. Although information on the toxicity of 2,4,6-TCP is available, there is a lack of information on the predicted no-effect concentration (PNEC) of 2,4,6-TCP, mainly due to the shortage of chronic and site-specific toxicity data. In the present study, acute and sub-chronic toxicity of 2,4,6-TCP on six different resident Chinese aquatic species were determined. PNEC values were calculated and compared by use of two approaches: assessment factor (AF) and species sensitivity distribution (SSD). Values for acute toxicity ranged from 1.1 mg L⁻¹ (Plagiognathops microlepis) to 42 mg L⁻¹ (Corbicula fluminea) and the sub-chronic no observed effect concentrations (NOECs) ranged from 0.05 mg L⁻¹ (Mylopharyngodon piceus) to 2.0 mg L⁻¹ (C. fluminea). PNECs obtained by the assessment factor approach with acute (AF = 1000, 0.001 mg L⁻¹) or chronic (AF = 10, 0.005 mg L⁻¹) toxicity data were one order of magnitude less than those from SSD methods (0.057 mg L⁻¹). PNEC values calculated using SSD methods with a 50% certainty for 2,4,6-TCP was less than those obtained by use of the USEPA recommend final chronic value (FCV) method (0.097 mg L⁻¹) and the one obtained by use of the USEPA recommend acute-to-chronic (ACR) methods (0.073 mg L⁻¹). PNECs derived using AF methods were more protective and conservative than that derived using SSD methods.     

基于二阶矩法的钢筋混凝土连续梁可靠度分析

根据结构可靠性理论,运用应力-强度干涉模型,考虑随机参数服从正态分布情况下的影响,构建连续梁在强度失效模式下的可靠性模型,应用二阶矩法通过数值分析计算结构的可靠指标,得出了结构的可靠度。为使所建立的模型符合钢筋混凝土结构的具体受力特点,荷载效应计算中考虑了钢筋混凝土结构的内力重分布,承载能力计算中参考了《混凝土结构设计规范》(GB50010-2002)给出的近似计算公式,得到了多维非线性的极限状态方程。通过实例对模型和可靠度方法进行了验证,计算分析表明,本文所建立的可靠性模型揭示了钢筋混凝土连续梁在各种随机因素作用下强度失效的规律,为钢筋混凝土连续梁的可靠性分析提供了依据。此外,本文提供的构件可靠度计算思路也可为其他各类钢筋混凝土构件的可靠度分析提供参考。     

连续曝气下河水水质及睡莲生理响应的季节变化

采取现场实验方法,在春、夏、秋三季测定了6个睡莲(Nymphaea tetragona L.)植物净化槽(曝气、非曝气)中睡莲的叶绿素(Chl)、可溶性蛋白(SP)含量与过氧化物酶(POD)、过氧化氢酶(CAT)活性,氮磷积累、生物量、根长、茎高、叶长、分蘖数、根密度等生物学指标及对应的水质常规理化指标,探讨了连续曝气下睡莲的生理响应及河水水质的季节变化。结果表明,连续曝气明显影响了睡莲的生理特性,导致净化槽中水质发生相应变化,且影响程度与睡莲生长状况的季节变化相关。曝气槽中睡莲植物的根长、茎高、叶长较短,叶片Chl-a、Chl-b、SP含量下降,而根组织POD、CAT活性升高,氮磷积累、生物量下降,分蘖数、根密度下降;春、夏季曝气对睡莲的影响相对较小,曝气槽中TN、NH4+-N浓度低于非曝气槽,而TP、溶解性P浓度明显升高;秋季曝气对睡莲的影响较严重,曝气槽中TN、NH4+-N、TP、溶解性P浓度均高于非曝气槽。研究结论为在污染河道生态修复工程实践中,针对水生植物生长状况的季节变化而进行曝气方式调节提供理论依据。     

Health and Environmental Implications of Rural Female Entrepreneurship Practices in Osun State Nigeria

In rural Nigeria, food processing is mostly engaged in by women and children. Most of these processes are done using outdated technologies that make use of traditional woodstoves. This article presents the health and environmental implications of the rural female entrepreneurs involved in food processing and proffer means of bettering the lot of these women to handle these hazards. A partially structured questionnaire and focus group discussion was used to capture data from respondents. The study revealed that about 73 % of women involved in direct production of garri and palm oil processing could be at risk of early death or disability-adjusted life years from the mentioned diseases. The article concludes that the rural female entrepreneur needs to be better positioned to handle these hazards, for her health, that of her children, as well as for the environment.     

长江三角洲农牧系统结构的区域差异及空间位移研究

调整农业结构，实现农业增效、农民增收农业可持续发展，以确保中国中长期食物安全，是中国目前和未来农业和农村工作的重点。农业结构的调整，必须建立在对系统整体认识的基础上，必须符合系统结构本身的演变规律。为此，作者于1996－1999年，以中国经济发达的长江三角洲农区为例，通过资料调研、专家咨询、农户调查、实地考察和试验等手段。对该区1980－1997年以来71个县市的农业生产进行了全面的调查。利用基于GIS的农牧系统综合评价系统，对长江三角洲农牧系统结构的区域差异和空间布局变化进行了全面分析。结果显示，长江三角洲农牧系统结构存在显著的空间梯度差异，布局上出现了明显的空间位移，农业重心开始向南北推移。棉花、小麦和玉米均向北部集中，生猪和家禽向北部和中部的东北部集中，农业生产呈现出显著的区域性专业化布局格式。     

钢线拉丝及表面处理生产线成套装备

主要论述了一种钢线拉丝及表面处理生产线成套装备的设计。该生产线的生产方式是多根钢线在牵引动力系统的作用下依次穿过各种处理设备,完成各道工序,实现钢线完成表面处理的目的。这个生产过程中,钢线可以完成放线、脱脂、退火、镀镍、造膜、烘干及收线一体化的工序。采用立体式布置,空间利用更为合理。     

Evaluating the impact of criminalizing drunk driving on years of life lost due to road traffic deaths in one megacity,China

Objective: Road safety is an important public health issue worldwide. However, few studies have analyzed the association between criminalizing drunk driving and years of life lost (YLL) due to road traffic deaths (RTDs). Our study can provide useful information about this policy.

Methods: We used interrupted time-series analysis to find the changes in monthly YLL and RTD before and after law enforcement began using RTD data from 2008 to 2014 in Tianjin.

Results: After adjustment for seasonality, months, holidays, and the number of people in each district, criminalizing drunk driving was followed by a 11.1% (95% confidence interval [CI], 1.1–21.1%) reduction in risk of RTDs and a corresponding 778.1-year (95% CI, 200–1,355.1) reduction in monthly YLL. The reduction in YLL was especially significant among males, those aged 16–64 years old, and suburban residents.

Conclusions: This study highlights that the law can lead to a reduction in YLL due to RTDs in Tianjin, China. Large immediate public health benefits resulted from the new road traffic law in China. YLL provides a complementary measure for examining the effect of criminalization on drunk driving RTDs.     

北京市典型道路交通噪声排放特征

采用北京市道路交通噪声自动监测系统2013—2017年采集的等效连续A声级数据,对城市快速路、城市主干线、城市次干线、城市支路的代表性站点噪声排放情况进行了统计分析,结果显示,北京市不同等级的道路噪声排放具备一定的特征,排放水平从大到小依次为城市快速路城市主干线城市支路和城市次干线,道路噪声随时间变化存在较为一致的周期性排放特征,24 h变化特征比较明显。个别道路排放特征存在特异性,如城市主干线道路的一个代表监测站点噪声监测值出现了逐年下降趋势,分析发现,北京市非首都功能疏解对其噪声值的下降有一定贡献。采取一定的规划和管理措施有助于减少道路交通噪声的排放。