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991.
介绍了地理信息系统开发的技术路线,阐述了建立地理信息系统过程中,如何解决系统模型建立、系统的空间坐标系统、数据质量问题和系统的质量体系等重要问题。 相似文献
992.
The peculiar rainfall pattern in Indiarenders the country highly vulnerable to floods. Forty million hectares of land, roughlyone-eighth of the country's geographical area, is prone to floods. Each year, floods cause extensive damage to life and property, losses being exacerbated by rapid population growth, unplanned development and unchecked environmental degradation. The country has been tackling the problem through structural and non-structural measures. While non-structural measures like flood forecasting aim at improving the preparedness to floods by seeking to keep people away from floodwaters, structural measures involve the construction of physical structures like embankments, dams, drainage channels, and reservoirs that prevent floodwaters from reaching potential damage centres. Almost 48% of the vulnerable area has been provided with reasonable protection, though floods continue to cause widespread losses year after year. This paper examines the incidence of floods and the trends in consequent losses in the eastern region of the country – one of the most vulnerable – with the objective of studying the efficacy of flood protection measures in the region. Based on a simple regression exercise for three highly vulnerable states in the region, the paper argues that flood protection measures have been inadequate in controlling losses and reducing vulnerability. Regressions for the three states over the period 1971 to 1996 indicate that the level of protection is an insignificant explanatory variable in explaining the number of people (adjusted for increases in density) affected by floods; while area affected, as an indicator of the intensity of floods remains the main loss-determining factor. 相似文献
993.
994.
The purpose of this report is to explain geochemical and stable isotopes trends in the Brazilian unit of the Guarani Aquifer
System (Botucatu and Piramboia aquifers) in S?o Paulo State, Brazil. Trends of dissolved species concentrations and geochemical
modeling indicated a significant role of cation exchange and dissolution of carbonates in downgradient evolution of groundwater
chemistry. Loss of calcium by the exchange for sodium drives dissolution of carbonates and results in Na–HCO3 type of groundwater. The cation-exchange front moves downgradient at probably much slower rate compared to the velocity of
groundwater flow and at present is located near to the cities of Sert?ozinho and águas de Santa Barbara (wells PZ-34 and PZ-148,
respectively) in a shallow confined area, 50–70 km from the recharge zone. Part of the sodium probably enters the Guarani
Aquifer System. together with chloride and sulfate from the underlying Piramboia Formation by diffusion related to the dissolution
of evaporates like halite and gypsum. High concentrations of fluorine (up to 13.3 mg/L) can be explained by dissolution of
mineral fluoride also driven by cation exchange. However, it is unclear if the dissolution takes place directly in the Guarani
Aquifer System or in the overlying basaltic Serra Geral Formation. There is depletion in δ
2H and δ
18O values in groundwater downgradient. Values of δ
13C(DIC) are enriched downgradient, indicating dissolution of calcite under closed system conditions. Values of δ
13C(DIC) in deep geothermal wells are very high (>–6.0‰) and probably indicate isotopic exchange with carbonates with δ
13C about –3.0‰. Future work should be based on evaluation of vertical fluxes and potential for penetration of contamination
to the Guarani Aquifer System.
Electronic Publication 相似文献
995.
降雨量作为水资源评价和管理的一个重要参数,长期以来,均采用多年平均值,但由于大气降雨的灾变性,这种平均值即不能客观地反映未来降雨量,更不能代表某一指定年份的降雨量,它实际上是一种建立在算术概率基础上的以数字表示的定性方法。为解决这一问题,本文利用灰色系统理论的灾变预测方法对山东省滕州市西部平原地区不同年份的降雨量进行预测,并通过预测建立该区地下水资源管理模型,主要由三部分组成:即①降雨预测系统;②水资源供需平衡系统;③水资源管理系统。 相似文献
996.
介绍了Web存储系统(WSS)中窗体注册表的基本概念,分析了注册表的工作流程和主要参数,举例说明了注册表的操作和应用。 相似文献
997.
基于MapX的厦门市PHS基站信息系统的设计与开发 总被引:4,自引:0,他引:4
针对电信部门对PHS基站管理的需求,通过对Mapinfo公司的MapX结构的分析,利用组件技术建立了一个Client/Server模式的GIS和MIS技术相结合的综合性管理信息系统。 相似文献
998.
Behrooz Tavakoli 《Journal of Seismology》2002,6(4):525-545
The sensitivity and overall uncertainty in peak ground acceleration (PGA)estimates have been calculated for the city of Tabriz, northwestern Iran byusing a specific randomized blocks design. Eight seismic hazard models andparameters with randomly selected uncertainties at two levels have beenconsidered and then a linear model between predicted PGA at a givenprobability level and the uncertainties has been performed. The inputmodels and parameters are those related to the attenuation, magnituderupture-length and recurrence relationships with their uncertainties.Application of this procedure to the studied area indicates that effects ofthe simultaneous variation of all eight input models and parameters on thesensitivity of the seismic hazard can be investigated with a decreasingnumber of computations for all possible combinations at a fixed annualprobability. The results show that the choice of a mathematical model ofthe source mechanism, attenuation relationships and the definition ofseismic parameters are most critical in estimating the sensitivity of seismichazard evaluation, in particular at low levels of probability of exceedance.The overall uncertainty in the expected PGA for an annual probability of0.0021 (10% exceedence in 50 yr) is expressed by a coefficient ofvariation (CV) of about 34% at 68% confidence level for a distance ofabout 5km from the field of the major faults. The CV will decrease withincreasing site-source distance and remains constant, CV = 15%, fordistances larger than 15 km. Finally, treating alternative models on theoverall uncertainty are investigated by additional outliers in input decision. 相似文献
999.
Juan C. Carvajal Víctor M. Taboada-Urtuzustegui Miguel P. Romo 《Soil Dynamics and Earthquake Engineering》2002,22(4)
The installation of vertical downhole arrays in the field that record the soil behavior during earthquakes, has opened the opportunity of exploring another alternate method for assessing the soil dynamic properties by solving the inverse problem. This article proposes a methodology for solving this problem using spectral analysis of downhole arrays records. The one-dimensional shear wave propagation model was used, considering a homogeneous-viscoelastic medium. This methodology was applied at the site known as Central de Abasto Oficinas (CAO), which is located in the lake zone of the Mexico City. The results indicate that even relatively low frequencies have a noticeable effect on dynamic soil properties. Shear modulus increases and damping ratio lessens when the frequency rises. 相似文献
1000.