湘潭锰矿的酸性水污染及其防治对策

湘潭锰矿酸性水的形成,与含矿岩系富含黄铁矿的黑色页岩密切有关。本文揭示了它的形成条件和影响因素及其对工农业生产的危害。作者根据当地酸性水的来源与分布。提出了一些防治措施,并对石灰中和法原理及其应用效果作了介绍。     

Electromagnetic response of a buried cylindrical conductor for sheet and line current sources

A major problem in electromagnetic induction studies in regions of localized source fields, such as the auroral and equatorial electrojet regions, is the source effect. Using an analytical model, the electromagnetic response of a buried conducting cylinder to sheet current and line current excitations has been studied for the period rangeT=5 s to 24 h. The validity of the numerical results obtained from the analytical model are compared with the numerical results obtained from a finite difference model. The results show that for periods less than 30 min, there is no significant difference in the response of the cylinder to both source fields. However, significant differences are observed at longer periods. It was also observed that the equivalent height at which a uniform sheet current at 100 km above the earth's surface can be approximated by a line current varies as a function of the source period.     

Variability of Mixed-Layer Heights over the Indian Ocean and Central Arabian Sea during INDOEX, IFP-99

The upper air data collected from the balloon-borne GLASS Sondes launched from the Oceanic Research Vessel (ORV) Sagar Kanya during the Intensive Field Phase of the Indian Ocean experiment (INDOEX, IFP-99;SK-141 Cruise) are utilized forstudying the variability in the mixed-layer heights observed over the western tropical Indian Ocean and central Arabian Sea. During the entire cruise, typical daytime convective mixed-layer heights (roughly corresponding to 1400 LT) obtained from _V and q profiles, were observed to be in the range 200–900 m. Shallowmixed -layer heights are observed, in general, over the Inter-Tropical Convergence Zone (ITCZ). Over the central Arabian Sea, vertical profiles of _V and q demonstrate a double mixed-layer structure of the marine atmospheric boundary layer (MABL), which gradually disappears close to the Indian coastline.     

Global elevation vibration and seasonal changes derived by the analysis of GPS height

Nearly10yearshaveelapsedsincetheGPSobservationtechniquewasappliedingeophysicalstudies.TheInternationalGPSServiceforGeodynamics(IGS),whichcameintooperationin1994,distributespreciseGPSsatelliteephemerides,Earthrotationparameters,internationalterrestrialrefe…     

杭州市滨江区似大地水准面的确定及精度分析

介绍了通过布设足够密度且分布均匀的GPS水准联测点,建立杭州滨江区高精度、高分辨率的似大地水准面数学模型的原理和方法.     

西藏墨脱地区工程精化似大地水准面的研究

采用地球重力场模型 ,考虑区域重力异常和地形改正 ,建立了西藏墨脱地区 1′× 1′似大地水准面模型。实际检测结果表明 ,该似大地水准面模型相对精度达到了± 0 .0 2 5m ,可代替几何水准测量 ,满足该地区工程建设的要求。     

城市环境保护信息系统结构框架研究

随着城市化进程的加快,城市人口增加,城市环境保护成为城市关注的焦点.充分利用计算机技术、地理信息系统技术有利于提高城市环境保护规划及管理水平.结合城市环境保护局的工作内容及实质,提出了基于办公自动化、管理信息系统、网站发布系统、GIS可视化信息系统的城市环境保护信息系统的结构框架,并对系统框架的构成、信息流程、服务和应用模式进行了论述,探讨了基于WEB GIS的信息系统应用的系统数据体系以及基础地理信息系统、图文一体化、空间分析、决策支持等系统功能.     

软土地区基坑工程环境影响及其保护实例分析

以基坑工程为背景,针对上海外环隧道浦西暗埋段的大型超深基坑工程的主要环境保护问题,对基坑开挖引起的主要管线和建筑物的沉降、跟踪注浆保护措施及其效果进行了分析.实测数据表明,基坑开挖使周围建筑物和管线会产生较大的沉降速率和沉降量,尤其是降低深层承压水使远处的建筑物产生了不容忽视的均匀下沉.实践证明,采取预注浆与跟踪注浆相结合的保护措施,可以有效地减小基坑开挖对周围环境的影响.     

Evidence for direct suspension of loessial soils on the Columbia Plateau

Wind erosion modelling efforts, both ?eld and wind tunnel studies, have traditionally focused on saltation‐based processes for estimating dust emissions from high wind events. This approach gives generally good results when saltation‐sized particles, 90 µm to 2 mm mean diameter, are prevalent on the exposed soil surface. The Columbia Plateau, located in north‐central Oregon and south‐central Washington, is a region with extensive loess deposits where up to 90 per cent of sieved particles (by mass) are less than 100 µm mean diameter. During high‐wind events, large amounts of soil and ?ne particulate matter are suspended. However, ?eld surfaces typically show little evidence of surface scouring or saltation, e.g. soil drifts or covered furrows. Velocity pro?le analysis of two high‐wind events and additional data from a third event show evidence of direct suspension process where saltation is not a major mechanism for eroding soil or generating dust emissions. Surface roughness heights are less than saltation roughness height estimates during peak wind speeds. Copyright © 2004 John Wiley & Sons, Ltd.     

Hybrid seismic protection of cable‐stayed bridges

This paper proposes a hybrid control strategy combining passive and semi‐active control systems for seismic protection of cable‐stayed bridges. The efficacy of this control strategy is verified by examining the ASCE first‐generation benchmark problem for a seismically excited cable‐stayed bridge, which employs a three‐dimensional linearized evaluation bridge model as a testbed structure. Herein, conventional lead–rubber bearings are introduced as base isolation devices, and semi‐active dampers (e.g., variable orifice damper, controllable fluid damper, etc.) are considered as supplemental damping devices. For the semi‐active dampers, a clipped‐optimal control algorithm, shown to perform well in previous studies involving controllable dampers, is considered. Because the semi‐active damper is a controllable energy‐dissipation device that cannot add mechanical energy to the structural system, the proposed hybrid control strategy is fail‐safe in that the bounded‐input, bounded‐output stability of the controlled structure is guaranteed. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective in protecting seismically excited cable‐stayed bridges. Copyright © 2004 John Wiley & Sons, Ltd.