正交化方法在水质模型参数确定中的应用

本文根据常微分方程参数反问题的数学理论，将正交化方法同有限差分法结合用于确定水质模型参数，并与正则化方法、最速下降法和共轭梯度法作了比较。其计算结果对比表明，正交化方法具有快速、简便、可靠的特点。更适合于水质模型参数的确定。     

从废感光胶片中回收银

研究了以Fe3 -乙二胺四乙酸二钠-N a2S2O3体系为浸取剂从废感光胶片中回收银的方法,考察了浸出银的最佳工艺条件。实验表明,当浸取剂中FeC l3.6H2O质量浓度为35g/L、N a2S2O3.5H2O质量浓度为150g/L、pH为7、固液质量比为3∶10时,浸取剂可重复使用6次,胶片上银的浸出率可达99%以上;浸取液中的银采用硼氢化钠还原回收,粗银粉配以熔剂高温熔炼可得到纯度达99.78%的银,银回收率达96.88%,回收银后的浸取液可循环使用。     

填埋场内水分运移过程双场耦合模型的探讨

基于多孔介质渗流力学和热力学理论，从填埋场内非等温的角度，理论上分析了场内垃圾含水率的分布与温度变化之间相互作用的机理，建立了垃圾填埋场内水分运移过程的双场耦合模型（三维），并提出模型的求解方法。为研究填埋场内水分的时空分布规律提供理论依据。     

从弱势群体入手增强安全理念

在2005年全国火灾分析报告中,有一个火灾特点十分引人关注,从火灾死亡情况看,老弱病残和流动务工人员等弱势群体所占比例居高不下.在很多地区,60岁以上老人、10岁以下儿童、伤残智障人员和进城就业的农民工占火灾死亡总人数的80%以上.     

我国湖泊富营养化问题及防治对策

富营养化是我国湖泊的主要问题,它不但制约了湖泊资源的可利用性,而且直接影响到人类的健康生存与社会经济的持续发展.分析了我国湖泊富营养化的现状、危害、产生的原因,提出了防治对策.     

我国三大地区城市发展现状及差异

通过采用相关年份有关城市方面的资料,从城市化水平,城市数量、体系和空间分布,城市社会经济发展状况,城市设施水平和城市经济效益5个方面,比较分析了我国三大地区城市发展现状,总结了我国三大地区的特征和城市发展差异,指出今后要积极缩小三大地区间的城市发展差距,推进区域经济的协调发展和可持续发展.     

A Parallel Study of SAR Levels in Head Tissues for Three Antennas Used in Cellular Telephones: Monopole, Helix and Patch

Summary This paper is a comparative study of several antennas commonly used in cellular telephones. These include a monopole, a helix-monopole and a patch antenna. Each one of these structures is modeled and numerically tested using finite-difference time-domain simulation and human models based on magnetic-resonance images, which allow for inclusion of details of the human body in the simulation. The testing procedure involves antenna simulation in the proximity of the human head. The behavior of each antenna is evaluated for variable distances from the head geometry (0, 1, 2, 4, 8 and 16 mm). Continuous waveform, representative of the sources used in mobile telephones, (250 mW, 1.8 GHz) is used as the form of the antenna excitation. The simulation outputs used as measures for this comparative study include transmitting and receiving antenna characteristics and the specific absorption rate (SAR). The SAR levels for the head tissues are calculated for and with accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP). The computed SAR levels within each of the considered tissues vary for the three antennas under investigation and are within the determined health safety standards. Results suggest that the patch antenna may be the structure of choice when considering safety standards, as its radiation yields the lowest local SAR in the head tissues.     

Cadmium solubility and sorption in a long-term sludge-amended arable soil

Cadmium solubility and sorption in an arable clay loam soil that had received sewage sludge for 41 years were compared to an unsludged control in batch studies. Soil pH dominated Cd sorption, explaining >92% of the variation in Kd values in both treatments. At any pH, Cd sorption was apparently slightly but significantly (p < 0.05) smaller in the sludge-amended soil compared to the control, even though the organic carbon content was 70% larger and the ammonium oxalate-extractable iron content was roughly doubled. Correction for dissolved organic carbon (DOC) complexation with the speciation model WHAM reduced the difference in sorption between treatments, but the sludged soil still had significantly smaller Kd values (p < 0.01). Batch equilibrations without addition of Cd showed that there was no significant difference in the solubility of "native" cadmium (defined as EDTA-extractable Cd) in sludged and control soils. The reason for the lack of increase in Cd sorption in the sludge-amended soil has not been established, but it may be due to competition for sorption sites on humic compounds with sludge-derived Fe and trace metals such as zinc. The fact that the pyrophosphate-extractable (i.e., organically associated) iron content was seven times larger in the sludged soil provides some supporting evidence for this hypothesis.     

突发事件机理体系与现代应急管理体制设计

本文为了增加对突发事件的科学认识,提升应急管理的能力水平,首先对突发事件和应急管理的内在机理进行剖析。通过分阶段、划层次地构建"4L-5S"机理分析模型,将二者划归为统一体系,以理清其逻辑内涵;然后,为顺应时代发展特征,满足应急管理的更高要求,实现应急管理工作从非常态协同应对转为常态化职能管理,对现代应急管理体制加以总体设计。从而,突发事件机理体系设计使得我国的突发事件机理研究逐渐过渡至具有阶段性和层次性,现代应急管理体制设计使得我国应急管理整合出具备现代思维理念的逻辑框架。