排序方式： 共有8条查询结果，搜索用时 16 毫秒
1
1.
Geographic information systems(GIS)are a widely used tool in urban planning and management.More and more cities and deecision-makers require its attributes of promptness,precision and visualization.But the application of GIS in urban environmental management is still a new field and relevant researches are getting on tardily.As a subsystem of GIS,an urban environmental management geographic information system(UEMGIS0should be a complex multi-discipline and multi-objective tool to perform quantitative multi-dimension analysis and to transfer the results into an expression legible to an ordinary user.It should be a dynamic system of prompt functions based on upgradable databases,and be composed of many subsystems respectively specialized in items about water,air,waste and noise as well as relative standards and regulations.However, existing UEMGISs mostly rely on the basic GIS too much to design the actual requirements of applications and managements in themselves,and the unavailability of sufficient fundamental data has retarded their improvement.In the design of a UEMGIS,the standardization of data classification should be taken into consideration to make the data exchangeable and shareable among its subsystems and within every subsystemj,and the applicable error limits for input data should be defined in accordance with the user s required precision of data out.Data acquisition can be easy and quick if remote sensing,global positioning system(GPS)and other technologies are combined with GIS,Rapidly progressing information fechnologies have been giving a bright prospect for the melioration of UEMGIS that will have great potential and wide application in environmental conservation. 相似文献
2.
Daily influent quantity forecasting plays an important role in sewage treatment plant design and operation.Its uncertain factors are classified into three categories including day types,weather conditions and special events,of which the latter two are consicered with a BP(Back Propagation)model.On this basis,the daily period feature is taken into account in the presented model.The data from a practical sewage treatment plant utility is employed to show the effectiveness of the method. 相似文献
3.
初步分析《国家信息化指标构成方案》 总被引：15，自引：0，他引：15
本文概括介绍了我国《国家信息化指标构成方案》的出台历程，并对其结构进行了分析，指出方案的优点与不足之处，最后提出修改建议。 相似文献
4.
Based on theoretical analysis and studying other methods, P-Ⅲ curve is transformed into an incomplete Γ function by means of mathematical expression transformation, thus the mathematical model of the fast commonly-used algorithm is drawn out. Algorithm comparison and practices demonstrate that the mathematical model has an easy algorithm, agile resolution process, very good commonality, faster convergence rate and better calculation accuracy, and can be applied to other respects. 相似文献
5.
A one-dimensional BOD-DO coupling model for water quality simulation is presented,which adopts Streeter-Phelps equations and the theory of back-propagation artificial neural network.The water quality data of Yangtze River in the Chongqing region in the year of 1989 are divided into 5 groups and used in the learning and testing courses of this model.The result shows that such model is feasible for water quality simulation and is more accurate than traditional models. 相似文献
6.
任伯帜 《重庆大学学报(英文版)》2003,2(2)
1. Introduction In drawing up the rainstorm intensity formula of a modern town to obtain the datum relation between the rainfall intensity and the rainfall time-recurrence period from original data of rainstorm intensity at different rainfall time, there are two methods: 1) the method of theoretical frequency, 2) adjusting original data with some theories or an empirical frequency curve. The second method is usually adopted based on a great quantity of project practices done by predecessors. … 相似文献
7.
Jian Duan Yuheng Zheng Wei Luo Wangyan Wu Tengrui Wang Yong Xie Sa Li Ju Li Yunhui Huang 《国家科学评论(英文版)》2020,7(7):1208
Graphite and lithium metal are two classic anode materials and their composite has shown promising performance for rechargeable batteries. However, it is generally accepted that Li metal wets graphite poorly, causing its spreading and infiltration difficult. Here we show that graphite can either appear superlithiophilic or lithiophobic, depending on the local redox potential. By comparing the wetting performance of highly ordered pyrolytic graphite, porous carbon paper (PCP), lithiated PCP and graphite powder, we demonstrate that the surface contaminants that pin the contact-line motion and cause contact-angle hysteresis have their own electrochemical-stability windows. The surface contaminants can be either removed or reinforced in a time-dependent manner, depending on whether the reducing agents (C6→LiC6) or the oxidizing agents (air, moisture) dominate in the ambient environment, leading to bifurcating dynamics of either superfast or superslow wetting. Our findings enable new fabrication technology for Li–graphite composite with a controllable Li-metal/graphite ratio and present great promise for the mass production of Li-based anodes for use in high-energy-density batteries. 相似文献
8.
1