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151.
《中国安全科学学报》1996,(Z1)
第一届亚太区安全健成海报、录像带创作比赛即将在港举行我国有关职业安全卫生单位积极报名参赛第十三届亚太区职业安全健康组织大会及展览会将于1997年4月21日至4月26日在香港举行,这是香港职业安全健康局首次主办的大型国际性会议,预计将有二千多人参加,此... 相似文献
152.
John K. Yu Martin M. Fogel 《Journal of the American Water Resources Association》1978,14(5):1239-1250
ABSTRACT: Use-oriented benefits and treatment costs analysis has been incorporated into a water quality index to show an economically optimized concentration for the treatment of the pollutants and the resulting water quality. This combined water quality index can be used in decisionmaking at the federal and local government levels. Five major pollutants, i.e., coliforms, nitrogen, phosphorus, suspended solids, and detergent, have been considered for the municipal waste water. With each higher level of improvement the treatment costs increase accordingly and the benefits associated with the reuse of this treated waste water will increase too but not for the nutrient removal in agricultural use. The optimal concentration is determined when the marginal costs equal the marginal benefits. The combined water quality index is the combination of the maximum net benefits and the water quality index of the optimized residual concentrations. This water quality index is zero dollars for the Tucson region in this study. The possible reclaimed use of municipal waste water is for agricultural irrigation and recreational lakes for the Tucson region. 相似文献
153.
A series of computer programs designed to predict gross annual soil loss on a watershed basis by application of the Universal Soil Loss Equation (USLE) have been developed. The programs provide an easy-to-use, flexible, and standardized means of organizing base data and applying the USLE to large land areas. The programs can be used to assess and to evaluate the effects of changing land-use patterns and conservation practices on soil losses. Critical or problem areas can be readily identified. The USLE Computer Programs are a useful research tool for investigators involved in water quality management, 208 planning, or conservation research.The package of computer programs consists of three main components: data input, the Main Program, and the Totals Program. Input data include both field base data describing the watershed and corresponding values for the factors in the USLE. The Main Program calculates the average rate of soil loss (tons/ acre/yr) and the total soil loss (tons/yr) for the smallest subunit of the watershed identified as the soil unit. Also calculated is an RKLS factor, which is an indication of the erosive potential of a given soil type, slope, and slope length, under a particular rainfall regime. The Totals Program aggregates soil unit losses into progressively larger units, that is, field, farm, subwatershed, and watershed units. An example of the programs' versatility and use is presented. 相似文献
154.
Abdel-Aziz I. Kashef Mahmoud M. Safar 《Journal of the American Water Resources Association》1975,11(4):651-664
ABSTRACT: The fresh-salt water interface in artesian aquifers has been investigated by various techniques on the basis of its analogy to the free surface in earth dams or cores of dams. Although various approximations are used, some more or less exact solutions exist. One of the simple methods, that would appeal to practical workers, was developed by the analysis of hydraulic forces. However, this method has not been checked thoroughly due to the lack of wide ranges of coverage by the more or less exact solutions. In this paper a suggested finite element method is used for the purpose of comparing with the method of hydraulic forces. The presented procedure eliminates some of the difficulties and uncertainties in current finite element procedures. Both methods proved to be in close agreement. Moreover, the hydraulic heads along the upper boundary of the artesian aquifer were found to be in close agreement with Dupuit's equation. The results of this investigation would greatly simplify the more complex management problems when the effects of discharge and/or recharge wells are added to the natural flow effects. 相似文献
155.
阐述了计算机实时仿真在危险气体泄漏扩散预警系统中的应用。文中首次提出了通过求解气体扩散方程一类反问题来确定源强,即根据传感器实时检测的浓度值,代入反问题算法的仿真程序求得近似泄漏强度,再将实时采集的气象参数一并代入扩散方程,在显示屏上给出有害气体云团在区域电子地图上的扩散态势。 相似文献
156.
J. G. Elliott R. S. Parker 《Journal of the American Water Resources Association》1997,33(5):1041-1054
ABSTRACT: The Gunnison River in the Gunnison Gorge is a canyon river where upstream dams regulate mainstem discharge but do not affect debris-flow sediment supply from tributaries entering below the reservoirs. Regulation since 1966 has altered flood frequency, streambed mobility, and fluvial geomorphology creating potential resource-management issues. The duration of moderate streamflows between 32.3 and 85.0 m3/s has increased threefold since 1966. This, along with flood-peak attenuation, has facilitated fine-sediment deposition and vegetation encroachment on stream banks. The Shields equation and on-site channel geometry and bed-material measurements were used to assess changes in sediment entrainment in four alluvial reaches. Sand and fine gravel are transported through riffle/pool reaches at most discharges, but the cobbles and boulders composing the streambed in many reaches now are infrequently entrained. Periodic debris flows add coarse sediment to rapids and can increase pool elevation and the streambed area affected by backwater and fine-sediment accumulation. Debris-flow supplied boulders accumulate on fans and in rapids and constrict the channel until reworked by larger floods. The response to streamflow-régime changes in the Gunnison Gorge could serve as an analog for alluvial reaches in other regulated canyon rivers. 相似文献
157.
Jacek K. Leznicki George P. Korfiatis 《Journal of the American Water Resources Association》1987,23(6):1085-1089
ABSTRACT: Two models based on variations of the one dimensional Boussinesq equation are presented. The models are formulated by treating each of the two nonlinearities appearing in the equation separately, and the resulting equations are solved by implicit finite difference techniques. The models have been used to predict drawdowns created from large scale pumping at an open coal mine pit dewatering project in Poland. The predictions were found to be in good agreement with data collected over a period of seven years. 相似文献
158.
159.
多棱插接式钢管塔具有制作安装方便、占地面积小等独特优势,正在得到越来越多的应用。但这种结构属于风敏感结构,风振特性是设计必须考虑的关键因素。钢管塔结构为空间薄壁壳体结构,其结构分析设计尤其是风振反应分析和风振控制与传统的杆系塔架结构有很大的不同。在静动力分析的基础上,提出利用钢球减振器对钢管塔进行风振控制,基于状态空间描述法模拟了钢管塔受控前后的位移时程反应,时域与频域分析结果表明该减振装置可以使结构的阻尼增加3~5倍,结构的风振反应可减小30%。本文的研究为钢管塔结构的合理设计提供了基础,有助于其在我国的推广应用,同时为行业规范和高耸结构设计规范的修订提供必要的理论基础。 相似文献
160.
A technique is presented to solve analytically the turbulent diffusion equation for the concentration of a passive contaminant
emitted from an elevated continuous source into the atmosphere. A generalized method of solution using Sturm–Liouville and
WKB theories is developed to overcome difficulties due to the height‐dependent wind velocity and diffusion coefficient appearing
in the diffusion equation. The method presented in this paper is able to derive an asymptotic expression for the concentration
obtained from the solution of the atmospheric diffusion equation which involves explicitly inhomogeneous wind velocity and
diffusion coefficient. The diffusion equation model derived from this method can be applied in a practical prediction of contaminant
concentration in a turbulent atmosphere.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献