EMI有源滤波器与阻抗失配问题的分析

EMI滤波器的阻抗失配往往使得滤波器不仅起不到应有的作用，反而加剧了干扰分量的强度，为了弄清有源滤波器的结构类型与阻抗匹配之间的关系，本文从滤波器的主要性能参数插入损耗的基本定义入手。推导了不同结构有源滤波器的插入损耗与阻抗、滤波器增益关系的表达式。由此得出滤波器结构类型与阻抗失配情况的合理搭配．经过实验验证该结论对选用和设计EMI有源滤波器有直接的指导意义。     

Removal of VOCs emitted from p-xylene liquid storage tanks by a full-scale compost biofilter

A full-scale compost biofilter system (CBS) was built to treat vapor losses emitted from three analogous vertical fixed roof p-xylene (p-X) liquid storage tanks of 7500 m³ total working volume. The CBS showed a stable and efficient treatment of standing loss (L_S) and working loss (L_W) with an average removal efficiency of 95.4% through 18-month standing storage and filling operation of the tanks. The weight of activated carbon employed in the concentration buffer influences the CBS performance for L_W treatment under high organic loads. The daily average pressure drops across biofilter bed displayed very low with a maximum of 7.6 mm-H₂O. This reflects that the CBS can be operated without stress and compression of biofilter bed and thus reduce maintenance frequency. No additional inputs of chemicals and fuels along with low electricity and water usage helped in its prolonged operation and increased its cost effectiveness. These advantages make the CSB become a promising control technology of vapor losses emitted from fixed roof organic liquid storage tanks.     

Fire accident investigation of an explosion caused by static electricity in a propylene plant

This study investigated a 2010 fire and explosion that occurred at a polypropylene (PP) and copper-clad laminate high-tech plant in Taiwan. Liquid acetone leakage caused the fire and explosion. One person was killed and five were injured; property damage was estimated at US$20 million. In contrast to conventional plants, high-tech plants have sophisticated instrumentation, highly complex pipelines, and confined spaces. In addition, the floor area in a high-tech plant is large and frequently contains a channel through the ground floor to the second or third floor. This channel design enables the fire compartment to be destroyed. Therefore, the system cannot confine the fire to a specific area, thus hindering fire-relief operations. In this study, the original fire outbreak occurred in the PP processing area on the ground floor. The acetone storage tank was located on the third floor. The investigation conducted at the fire site of the situations of the burning (bursting) loss determined that the acetone liquid leaked and dripped from floor cracks and tunnel oven to the PP processing area. Because the PP manufacturing process rapidly generates static electricity, the flammable liquids made contact with the source of ignition, which caused the explosion and fire. Various procedures, such as those involving the operating environment of production, packaging, and processing in a high-tech plant, are likely to produce static electricity in a workplace. Improved electrostatic management can prevent the loss of property and lives, liquid acetone leakage, and loss of equipment caused by static electricity fire.     

基于马尔科夫灰色残差GM(1,1)模型的火灾损失预测

科学地预测火灾事故及其损失,对于制定火灾防控措施具有重要的现实意义。应用基于马尔科夫的灰色残差GM(1,1)模型,对2002—2011年全国火灾损失进行模拟和预测,结果表明,该模型预测精度明显高于GM(1,1)模型,为火灾损失的预测提供了一种简单而可靠的新途径。     

企业危险源风险管理方法研究

简要分析危险源管理现状,以及风险控制、风险的财务安排、保险等风险管理方法。阐述如何将风险管理理念引入到危险源管理中,将风险管理与企业危险源管理相结合,以提高危险源的管理水平。重点论述利用最小化代价原则紧抓企业安全管理;利用风险集中原理,合理使用安全投入资金;利用风险转移方法,降低事故率;合理使用财务方法,减小事故引发的损失。从而实现预防事故、减少损失、合理安排资金、保证企业的可持续发展。     

Using persuasive messages to encourage voluntary hearing protection among coal miners

INTRODUCTION: This longitudinal field study was designed to encourage Appalachian coal miners in West Virginia and Pennsylvania to engage in hearing-protection behaviors. METHOD: Participants were mailed postcards that featured either a positive, negative, or neutral message on the outside of the postcard and a message encouraging hearing protection behaviors on the inside. The first posttest measurement of the effectiveness of the persuasive messages was conducted about a week after the postcards were mailed. The delayed posttest measurement was conducted six weeks later. RESULTS: Responses from 307 coal miners revealed that the positive or neutral messages generated significantly more self-reported hearing protection behaviors than the negative message. Identical results were obtained in a delayed posttest assessment of miners' self-reported hearing protection behaviors. The positive message was also more effective than either the neutral or negative message in preventing defensive mechanisms from emerging over time. IMPACT ON INDUSTRY: Positive and neutral messages were convincingly more successful than negative messages in facilitating self-reported hearing protection behaviors among coal miners. Similarly, the positive messages kept defensive processes at bay.     

膜分离技术在油气回收中的应用

在油品储运、销售、应用过程中，存在着大量的油品蒸发损耗。可用膜分离技术来分离回收轻质油品蒸发排放出来的油气。介绍膜法油气回收的分离机理、应用实例和工艺设计数据，综合比较常用的吸收法、吸附法、冷凝法及膜法油气回收技术并获得各自的量化分值，认为膜法回收技术为目前较有可能及较容易取得突破成果的研究领域。最后指出今后的研究重点。     

城市用地扩展与耕地保护

中国耕地资源不足,人均耕地不足世界水平的一半。由于快速城市化,城市用地扩展(占用耕地)和耕地保护间的矛盾已引起了国内外学者的广泛关注。对此矛盾存在两种看法,一种观点认为城市用地远比农村居住用地节约,城市化有助于减少耕地的流失;另一种观点认为中国城市用地扩张和耕地资源稀缺之间矛盾尖锐,城市用地的蔓延极可能造成耕地资源的紧张。论文针对国外城市发展水平较高的国家和我国城市发达地区的城市发展历程,探讨了在城市发展过程中,这些国家或地区的耕地资源总量的变化趋势。然后,利用由遥感解译的土地利用数字化图,分析了我国部分地区城镇人均用地和农村人均居住用地的差距。结果认为,中国城镇人均用地并不像人们想象的那样远低于人均农村居民点用地,而是较为接近;中国城市用地的扩展可能导致耕地资源的紧张。     

致癌和非致癌环境健康风险的预期寿命损失评价法

预期寿命损失法（loss of life expectancy,LLE）可以对致癌和非致癌物质的环境健康风险进行评价和比较,是一种污染物环境健康风险评价的新方法.应用该方法对中国目前危害较大的6种典型致癌和非致癌污染物砷、DDTs、苯并芘、铅、汞、镉造成的人体的预期寿命损失进行了分析,并比较了6种污染物的环境健康风险大小.结果表明,预期寿命损失法可以作为污染物健康风险评价的一种方法,致癌物质砷、DDTs、苯并芘分别导致一个健康个体寿命损失3.6 d、2.2 d和12.1 d,非致癌物质铅、汞、镉分别导致一个健康个体寿命损失1.1 d、1.7 d和5.8 d;用预期寿命损失方法可以对致癌、非致癌风险在同一尺度上进行比较,在目标污染物现有相关研究基础上,6种污染物的健康风险大小顺序为苯并芘＞镉＞砷＞DDTs＞汞＞铅.     

大连市水土流失控制模拟研究

从控制大连市水土流失出发,结合大连市地表总体状况,根据水土流失通用方程,利用拉格朗日中值定理分析原理,模拟计算了土壤有机质含量、地面覆盖类型、地面覆盖率和水土流失控制距离等方面对水土流失造成的影响;分别计算了不同地表条件下控制水土流失的理论经济点和理论敏感点;定量分析了不同地表作用因子对控制水土流失的影响程度.模拟结果表明:对水土流失影响最大的地表作用因子是土壤有机质含量,其次依次为地面覆盖率、地面覆盖类型和水土流失控制距离;控制水土流失最基本的地表条件是,土壤有机质含量不得低于1.78%,地面覆盖率不得低于41%,地面不得裸露,最基本的植被覆盖类型是草地,水土流失控制距离不得低于3　603 m.依据模拟结果,提出了控制大连市水土流失的措施.