Alternative method to prevent thermal runaway in case of error on operating conditions continuous reactor

Thermal runaway was studied in a continuous tubular pilot reactor under steady-state regime. Different accident scenarii were conducted by making some errors on reactant concentrations and/or temperature feed. To prevent thermal runaway, control by direct contact by solvent injection was used at different reactor locations. This injection allowed controlling the maximum reaction temperature. A simplified analytical method to estimate the maximum reaction temperature along the reactor was used.Benefit of this control method was the diminution of computational time. Furthermore, by injecting solvent to control maximum reaction temperature, there is no need to shut down the unit. The control method was validated experimentally.     

基于CVM方法分析牧民对禁牧政策的受偿意愿——以锡林郭勒草原为例

确定居民对生态措施实施的受偿意愿,对目前迫切需要的生态补偿政策制定以及生态恢复和保护的有效性具有重要的现实意义。选用锡林郭勒草原为案例区域,通过入户调查及在那达慕大会集中调查相结合的方式,调查锡林郭勒草原地区牧民对禁牧措施的态度和受偿意愿。分析结果显示:53%的牧民愿意参加禁牧,而不愿意参加禁牧主要是由于补偿标准不合理引起的。计量经济学模型分析表明,牧民对禁牧的支持态度与牧民的收入和草地面积呈正相关,与养羊数量呈负相关。牧民的受偿意愿由牧民养羊数量、受教育年限、草地现状以及对禁牧政策的支持程度决定。根据意愿调查法初步估算锡林郭勒草原地区禁牧措施实施后牧民的补偿意愿,牧民家庭对禁牧政策的平均受偿意愿为每年每户2.7717万元,人均受偿意愿为8399元,平均每1hm2草地受偿意愿为85.95元。     

Probability distributions and statistical inference for axial data

Observations on axes which lack information on the direction of propagation are referred to as axial data. Such data are often encountered in enviromental sciences, e.g. observations on propagations of cracks or on faults in mining walls. Even though such observations are recorded as angles, circular probability models are inappropriate for such data since the constraint that observations lie only in [0, π) needs to be enforced. Probability models for such axial data are argued here to have a general structure stemming from that of wrapping a circular distribution on a semi-circle. In particular, we consider the most popular circular model, the von Mises or circular normal distribution, and derive the corresponding axial normal distribution. Certain properties of this distribution are established. Maximum likelihood estimation of its parameters are shown to be surprisingly, in contrast to trigonometric moment estimation, numerically quite appealing. Finally we illustrate our results by several real life axial data sets. Received: September 2004/ Revised: December 2004     

用黑麦幼苗法测定土壤中污染元素的生物有效性

本文对全国污灌区１２个土样中Ｃｄ形态与生物有效性的试验表明，Ｃｄ的交换态，吸附态，有机结合态均有效，且有机结合态最为有效，对紫阳县富硒土壤的试验表明：黑麦幼苗中的总Ｓｅ量与０．１ｍｏｌ／１ＫＨ２ＰＯ４的浸提量最为相关，从而推荐该法为酸性土壤有效Ｓｅ的浸提方法，对西安污水厂污水污泥在娄土上不同施用量的试验表明：幼苗中Ｎ，Ｐ随施用量增加而增加，Ｎ，Ｐ的有效率分别为５０－７０％及１５－２８％；黑麦幼苗中     

Set-up costs and the existence of competitive equilibrium when extraction capacity is limited

Although set-up costs are prevalent and substantial in natural resource extraction, it is known that a Walrasian competitive equilibrium cannot exist in simple extraction models with set-up costs. This paper demonstrates that this result is sensitive to the assumption of unlimited extraction capacity and derives sufficient conditions for existence. An equilibrium exists if extraction is limited such that each firm earns sufficient surplus to cover its set-up costs or if firms choose extraction capacity subject to non-increasing returns. The resulting competitive equilibrium price either grows at the rate of interest when total extraction is below industry capacity or is constant when industry capacity is fully utilized. In the equilibrium, identical deposits are opened simultaneously, and set-up costs for new deposits are incurred when the industry has excess capacity rather than when capacity is fully utilized.     

试论冶金企业职业安全卫生评价技术和方法

介绍了安全卫生评价的目的和要求,同时介绍了职业安全卫生评价的方法。     

几种螯合剂对污染土壤的重金属提取效率的研究

在Cd,Pb污染的土壤上,采用批提取实验(batchexperiment),研究了几种螯合剂和不同的水土比对重金属提取效率的影响。结果表明:螯合剂对Cd的提取效率随着各淋洗剂浓度的提高而逐渐提高,相同浓度下各淋洗剂的提取效率大小顺序依次为EDTA>DTPA>NTA>PA>CA>CD>HCl。随水土比提高,相应的提取效率也提高。几种淋洗剂中只有EDTA对Pb和Cd都能达到理想的淋洗效果。     

活性污泥二次污染问题的探讨(Ⅱ)

讨论了城市污水经过A／O工艺处理时活性污泥的二次污染问题。将原水、处理后的出水及活性污泥用甲苯萃取，萃取相经过真空浓缩后，采用GC／MS测定了样品中的有机化合物，结果表明，在A／O工艺处理城市污水过程中，活性污泥的吸附作用是主要的，降解作用是次要的；A／O工艺所排放的活性污泥仍然是一种危险的污染物。     

Influence of soil moisture on the sequestration of organic compounds in soil

A study was conducted as a part of continuing investigation of the effect of soil moisture on the sequestration of organic compounds aged in the soil. Here, experiments focused on the effects of moisture changes within the soil before, during, and after contaminant addition. The extractability of aged (68 d) phenanthrene was greater from soil that had been subjected to wetting and drying cycles prior to solute addition as compared to soil initially maintained at constant moisture. The recovery of phenanthrene added to moist soil was increased relative to extractability from soil that was air-dried at the time of the contaminant addition. Repeated wetting and drying of soil after the addition of atrazine or phenanthrene resulted in decreased extractability of the compounds as compared to samples maintained at constant moisture. A method for rapidly sequestering contaminants is proposed and may be useful in limiting the time required for laboratory studies involving “aged” contaminants. These data build upon the findings of earlier work from our laboratory and indicate that changes in the moisture conditions of soil can affect the availability of sequestered contaminants possibly through alterations in the structure of the natural solid.     

国际间绿色GDP核算方法评述

绿色GDP核算是通过将资源环境成本纳入国民经济核算中来实现环境管理的一种有效的经济手段。本文分析了世界各主要核算体系下的编制方式,探讨目前各种核算方式所存在问题及缺失,以加深各方面对绿色GDP核算的理解与实践拓展。