Effect of Time Scale on the Performance of Different Sediment Transport Formulas in a Semiarid Region

This note compares the performance of various sediment transport formulas for a semiarid region of southern Italy (Puglia region). The sediment transport that occurs in the main streams of the region has been monitored for about 30 years (1958–1986) and the measured data are available at monthly intervals. The field data were compared with those predicted from four formulas (Ackers-White, Engelund-Hansen, Yang, and Van Rijn) selected on the basis of the sediment transport mode, the theoretical aspects, and the sensitivity to basic physical properties. The study examines the ability of the formulas to adapt to local conditions, the influence of time scale on predictions, and the accuracy of the prediction varying the discharge. The Engelund-Hansen and Van Rijn formulas (suspended sediment transport) estimate well the sediment load and are largely unaffected by variations in time scale. For low sediment loads, these formulas were less reliable.     

旱田逆切旋耕刀片正切面的研究

从旱田土壤条件出发，建立了适合旱田耕作的逆切旋耕模型，提出了逆切旋耕刀片正切面截断面为直线－圆弧组合型刀片的设计方法，即刀片正切面的几何参数由切削上块的抛掷特性和土块的抛脱条件来决定．在试验条件下，按本方法设计的刀片的功耗比国标刀片降低５．３６％～１４．７％．     

The use of time-integrated NOAA NDVI data and rainfall to assess landscape degradation in the arid shrubland of Western Australia

Ground-based data on total phytomass were collected in 1998 and 1999 from four sampling domains, each nearly 1000 km², within the arid shrubland of Western Australia. These data were used in models relating rainfall and landscape characteristics to total phytomass to provide landscape-scale estimates of total phytomass and rainfall-use efficiency for 1992-1999 (referred to as RUE_P). These modelled estimates were compared with remotely sensed estimates of total phytomass (I-NDVI) and rainfall-use efficiency (I-NDVI/annual rainfall; referred to as RUE_N) using data from NOAA satellites.There was good agreement between ground-based and remotely sensed estimates of total phytomass but less agreement between estimates of rainfall-use efficiency. Partitioning the landscape on the basis of landscape resilience did not improve the amount of variance accounted for in RUE_P or RUE_N and there were conflicting relationships between landscape-scale indicators of landscape function and RUE_N. There was, however, evidence to suggest that temporal change in RUE_N may provide a useful broad-scale indicator of landscape degradation or recovery over decadal time intervals. Recommendations are made for broad-scale application of this indicator based on temporal trends in RUE_N.     

A low cost design solar desalination unit

A novel low cost design solar still is described and performance data are presented. The proposed design eliminates the need for support or side-walls, as required in most conventional solar still designs. A comparison of the measured still productivity values between the proposed design and a large solar distillation plant constructed in India has shown that our design simplification has not affected still performances. An economic analysis, based upon the fraction of still construction cost dedicated to the still wall construction, has indicated that the proposed design should reduce the overall cost/m² of the solar still construction by at least 20%.     

Water Reuse/Recycling and Reclamation in Semiarid Zones: The Israeli Case of Salination and “Hard” Surfactants Pollution of Aquifers

The essence of three case studies in relation to the global problem of surface and groundwater contamination by inorganic salts and biodegradation-resistant (“hard”) nonionic surfactants (APEOs) is presented and the results analyzed as far as the long-term consequent water salt and APEO profiles are concerned. The main conclusion derived is that sustainable large-scale reuse/recycling and reclamation in semiarid zones requires a combined desalination-biological treatment of APEO-free sewage/wastewaters before their reuse. This should be done without delay in order to ensure the quality of the supplied water from the scarce resources and to avoid, most probably, an irreversible process of aquifer contamination in these zones.     

关于农村建设用地整理与新农村建设的几点思考

农村建设用地整理是社会主义新农村建设的重要内容,是盘活农村存量建设用地、节约集约用地的重要途径,是新时期开创土地整理工作新局面的大好时机。本文分析了当前开展农村建设用地整理的时代背景、经济条件和整理潜力,提出了应注意做好统筹规划、建立多元化融资机制和保护农民土地权益等问题。     

基于农用地分等的耕地等级折算研究——以呼和浩特市为例

耕地占补平衡由数量型向数量一质量型综合平衡管理的升级，已成为当前土地资源管理工作的重要任务。本文以呼和浩特市为例，在农用地分等成果的基础上，以单位标准粮产量为桥梁，确定耕地质量数量等级折算系数，从而实现耕地占补的数量一质量综合平衡。     

干旱/半干旱区MODIS地表温度反演与验证研究

劈窗算法是目前热红外遥感反演地表温度最常用的方法,根据Coll提出的劈窗算法建立基于MODIS适用干旱/半干旱区地表温度反演算法,并用同期的LP DAAC发布的MODIS地表温度产品和相应的53个气象站点的实际观测数据进行验证。通过分析,模型的反演精度与MODIS地表温度产品的反演精度相当,与气象观测数据相一致,反演精度较好,能够较精确地反演干旱/半干旱地区地表温度的时空变化特征。     

针床式测试仪的测试可靠性研究

建立了线路板（PCB）测试中变形对应的二维图形变换模型，使用正态和Weibull分布统计模型处理数据，成功用于针床式在线测试仪（Bed-of-nails Testing Fixture）可靠性定量评估，并由定量实测结果分析了针床测试仪对准误差的类型、大小及产生原因。     

煤矿塌陷区地基稳定性与承载力研究现状分析

煤矿塌陷区在我国分布较广泛,为了保证国家建设的需要和节约耕地,就必须对塌陷区土地进行科学开发和利用,使其恢复为建设用地.在综合分析大量文献的基础上,从老采空区的活化机理、地表沉陷与变形规律等方面,分析了煤矿塌陷区地基稳定性和承载力的研究现状.分析研究表明,提高塌陷区土地利用率的关键是需要准确分析和计算出地基的承载力.煤矿塌陷区地基稳定性和承载力研究,对于提高土地的利用率、保护耕地,促进我国经济和社会的协调和可持续发展等,具有十分重要的理论价值和现实意义.