沙漠化遥感动态监测的方法与实践

土地沙漠化是我国北方地区一个严重的环境经济问题,进行遥感动态监测是了解其发展过程、状态和趋势的有效方法。本项研究在确定了沙漠化土地遥感判别指征体系和监测技术路线的基础上,提出遥感动态监测的方法,并以毛乌素沙 地为例,利用不同时期的TM遥感资料对土地沙漠化进行了动态监测。结果表明,该方法能够揭示出研究区内沙漠化土地时空分布及其变化规律,为防治沙漠化提供科学的依据。     

Effects of physical parameters of a gravel bed on the activity of sulphate-reducing bacteria in the presence of acid mine drainage

The use of sulphate-reducing bacteria (SRB) in the passive treatment of acid mine drainage (AMD) requires the presence of a sediment, such as gravel bed, in which the bacteria can establish microenvironments conducive to their survival in the presence of oxygen and acidity. The characterization of relationships between the physical environment and SRB activity would be useful in the sizing of passive treatment systems using SRB. The effects of physical parameters of a gravel bed (i.e. void volume, total surface area of gravel, type of gravel) on SRB activity while in the presence of varying loads of fresh AMD was investigated. SRB activity was expressed as the proportion of sulphate removed after 7 days. The study was accomplished in a series of column reactors containing beds comprising different types and size classes of gravel. SRB were established in the beds and metal and sulphate removal were monitored. Quantifiable relationships were found to exist between SRB activity and the physical parameters of the bed. ©1997 SCI     

砂状氧化铝生产过程中晶种对分解过程影响的研究

根据山西铝厂种分生产工艺条件,研究高浓度铝酸钠溶液种分分解过程中晶种粒度和种子比对分解过程的影响规律。结果表明,晶种粒度对分解率和产品质量都有较大影响,使用粗晶种,分解产品粒度大,强度高,分解率低;使用细晶种,分解产品粒度小,分解率高;种子比较大时,分解率提高,而且有利于产品氢氧化铝的长大。     

海底管道失稳过程的模型试验研究

直接铺设于砂质海床上的管道的失稳是一“流-管-土”耦合问题。本文利用U形水槽产生的振荡流对管道的失稳过程进行了模拟 ,通过改变管道水下重量、管径和加载历史研究管道失稳的条件。在试验结果的基础上 ,初步得到了管道失稳的临界Fr数与管重无量纲参数之间的关系曲线 ,并发现不同的加载历史对管道稳定性的影响程度不同     

浙江省砂砾石层工程地质特征及坝基防渗处理

砂砾石地基具有高抗剪强度、低压缩性、高承载力等特征,一般其上部为强透水层,为防止渗透破坏,在砂砾石层上建坝须对其进行防渗处理,文章列举了本省的几个工程,阐述了砂砾石层的工程地质特征及砂砾石坝基的防渗处理类型及其效果。     

阿拉尔耕地沙土与65Mn摩擦行为的研究

目的 探究阿拉尔耕地沙土与65Mn的摩擦学行为,为高速犁结构设计、优化和材料选择提供理论基础。方法 采用摩擦磨损试验机,选择土壤含水率、平均粒径、载荷、转速和摩擦时间等5个参数进行单因素多水平试验,研究沙土对65Mn的摩擦行为,并对各因素水平下金属磨损形貌进行分析。结果 随着含水率的增加,土壤黏附力和润滑水膜的厚度增大,摩擦因数减小,磨损量呈二阶抛物线规律;随着平均粒径的增加,微观接触面积减小,摩擦因数、磨损量与粒径呈负相关;随着载荷的增加,磨料挤压嵌入金属表面,使得微观切削量增加,摩擦因数呈小幅上升趋势,磨损量呈大幅上升趋势;随着转速的增加,摩擦因数、磨损量变化较缓和;随着摩擦时间的增加,因热量的累积,摩擦因数和磨损量呈上升趋势,土壤与金属的摩擦逐渐演变为土壤之间的摩擦。分析磨损形貌发现,65Mn金属磨损表面始终伴随着磨料磨损造成的犁沟、疲劳和剥落,还发现了腐蚀磨损造成的裂纹,表面金属材料被腐蚀成金属盐结晶体,2种形式的磨损交互影响,加剧了65Mn的磨损。结论 方差分析表明,与土壤含水率、载荷、转速相比,平均粒径和摩擦时间对沙土与65Mn的摩擦因数的影响较大,平均粒径对65Mn的磨损的影响最大。     

A GIS‐based approach to mapping probabilities of river bank erosion: regulated River Tummel,Scotland

This study explores the use of Geographic Information Systems (GIS) techniques for mapping river channel planform change and bank erosion probability. The method used is primarily based on an approach developed by Graf (Graf, W.L. 1984. ‘A probabilistic approach to the spatial assessment of river channel instability’, Water Resour. Res., 20 (7), 953–962), which proposed that bank erosion probability could be determined for any given cell on a floodplain by taking into account (i) its distance laterally and in the upstream direction to the active river channel, and (ii) a value representing flood magnitudes for the given period. In this study, Graf's method is refined by using a GIS approach and by incorporating the influence of geomorphic variables, such as river bank morphology, sediment type and floodplain vegetation, on bank erosion rates. In addition, the technique is applied to a wandering gravel‐bed river of roughly 80 m width, representing a different type and size of river to that used in Graf's study. Thus, the wider applicability of the technique is tested. In addition, the analysis here covers only a short time scale (1988–1994) compared with that used by Graf. The high temporal resolution of this study is enabled by the use of aerial photography and also by the substantial channel changes that occurred within this time period as a result of several high magnitude flood events. The results of the study indicate the usefulness and validity of the approach, particularly with regard to floodplain erosion hazard mapping and the assessment of the effects of altered flood regimes and land use. Copyright © 2000 John Wiley & Sons, Ltd.     

印尼CLP电厂地基抗震设计分析方法

由于存在饱和砂土,高烈度区地震灾害显著。由于国外工程一般不采用基本烈度参数进行抗震设计,本文介绍了在国外电力工程勘测设计过程中,采用了地震动峰值加速度对砂基液化、地基承载力分析,对相关工程有一定的借鉴作用。     

冷冻法在三山岛新立矿区的工程实践

在三山岛金矿新立矿区西风井的施工中,通过多开盐水泵、增加盐水循环速度,增加冻结孔个数、降低冷冻孔间距,增加盐水浓度、把盐水温度降低到凝固临界点等措施,顺利通过了第四纪砾砂富含卤水层。为工程和水文地质条件类似的工程,提供了宝贵的经验,值得条件类似的矿山借鉴。     

浅谈中间状氧化铝对电解生产的影响

结合200kA铝电解槽在使用不同性能氧化铝期间产生的影响,从理论上、实践上对中间状氧化铝与砂状氧化铝的性能进行对比分析.