COMPUTATION OF STAGE-DISCHARGE RELATIONSHIPS AFFECTED BY UNSTEADY FLOW1

ABSTRACT: The dynamic relationship between stage and discharge which is unique to a particular flood for a selected station along the river can be determined via a mathematical model based on the complete one-dimensional equations of unsteady flow, i.e., the equations for the conservation of mass and momentum of the flood wave, and the Manning equation which accounts for energy losses. By assuming the bulk of the flood wave moves as a kinematic wave, the need for spatial resolution of the flood can be eliminated, and only the time variation of either the discharge or stage at the selected station is necessary for the computation of the other. The mathematical model can be used in river forecasting to convert the forecast discharge hydrograph into a stage hydrograph which properly reflects the unique dynamic stage-discharge relationship produced by the variable energy slope of the flood discharge. The model can be used also in stream gaging to convert a recorded stage hydrograph into a discharge hydrograph which properly accounts for the effects of unsteady flow. The model is applied to several observed floods at selected stations along the Lower Mississippi, Red, and Atchafalaya Rivers. The root mean square errors between observed and computed discharges are in the range of 3 to 7 percent, values well within the accuracy of the observations. A simple, easily-applied graphical procedure is also provided for estimating the magnitude of the effect of the unsteady flow on stage-discharge ratings. As a general rule, the dynamic effect may be significant if the channel bottom slope is less than 0.001 ft/ft (about 5 ft/mi) when the rate of change of stage is greater than about 0.10 ft/hr.     

基于资源安全的企业人才风险管理

从资源安全的角度出发 ,笔者阐述了企业人才资源的重要性 ;对我国企业目前面临的主要人才风险进行了识别 ;指出我国企业目前的人才风险主要来自人才外流、人才获取、人才道德和人才风险意识四个方面 ;强调了我国企业加强人才风险管理的重要意义。从人才风险引起的各项损失及其损失概率的角度 ,提出了企业进行人才风险估测的方法 ;建立了人才风险损失模型 ;指出了我国企业的人才风险管理、有效防范人才风险的途径。     

ESTIMATING RESIDENTIAL FLOOD CONTROL BENEFITS USING IMPLICIT PRICE EQUATIONS1

ABSTRACT: An implicit price model relating residential lot value to price determining characteristics of land is developed to measure the benefits of a structural flood control project. Special attention is given to the selection of relevant price determining characteristics of residential lots. An implicit price equation is estimated for both the with and without project conditions. Flood damages are quantified through the use of a dummy variable indicating a flood plain location. The analysis shows that annual flood damages were reduced by $15,275.     

Development and Evaluation of Bankfull Hydraulic Geometry Relationships for the Physiographic Regions of the United States

Bankfull hydraulic geometry relationships are used to estimate channel dimensions for streamflow simulation models, which require channel geometry data as input parameters. Often, one nationwide curve is used across the entire United States (U.S.) (e.g., in Soil and Water Assessment Tool), even though studies have shown that the use of regional curves can improve the reliability of predictions considerably. In this study, regional regression equations predicting bankfull width, depth, and cross‐sectional area as a function of drainage area are developed for the Physiographic Divisions and Provinces of the U.S. and compared to a nationwide equation. Results show that the regional curves at division level are more reliable than the nationwide curve. Reliability of the curves depends largely on the number of observations per region and how well the sample represents the population. Regional regression equations at province level yield even better results than the division‐level models, but because of small sample sizes, the development of meaningful regression models is not possible in some provinces. Results also show that drainage area is a less reliable predictor of bankfull channel dimensions than bankfull discharge. It is likely that the regional curves can be improved using multiple regression models to incorporate additional explanatory variables.     

Seasonal and Regional Patterns in Performance for a Baltic Sea Drainage Basin Hydrologic Model

This study evaluates the ability of the Catchment SIMulation (CSIM) hydrologic model to describe seasonal and regional variations in river discharge over the entire Baltic Sea drainage basin (BSDB) based on 31 years of monthly simulation from 1970 through 2000. To date, the model has been successfully applied to simulate annual fluxes of water from the catchments draining into the Baltic Sea. Here, we consider spatiotemporal bias in the distribution of monthly modeling errors across the BSDB since it could potentially reduce the fidelity of predictions and negatively affect the design and implementation of land‐management strategies. Within the period considered, the CSIM model accurately reproduced the annual flows across the BSDB; however, it tended to underpredict the proportion of discharge during high‐flow periods (i.e., spring months) and overpredict during the summer low flow periods. While the general overpredictions during summer periods are spread across all the subbasins of the BSDB, the underprediction during spring periods is seen largely in the northern regions. By implementing a genetic algorithm calibration procedure and/or seasonal parameterization of subsurface water flows for a subset of the catchments modeled, we demonstrate that it is possible to improve the model performance albeit at the cost of increased parameterization and potential loss of parsimony.     

Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode

Electrochemical oxidation of polyethylene glycol (PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified(PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.     

Two stages kinetics of municipal solid waste inoculation composting processes

IntroductionCompostingisanatureprocess,butmanyman inducedinnovativemeasureshavebeendevelopedtoacceleratecompostingefficiency .Variousspecializedseedinoculumshavebeenappliedforpracticalengineering(Biey ,2 0 0 0 ) .ThemicrobialfloraandthemassconcentrationofmicrobesinMSWcompostingprocessesunderlyinginoculationaredifferentinvariousstages(Lei,2 0 0 0 ;Akihito ,1998) .Atthesametime ,thelivingenvironmentofmicroorganismsisalsoincessantlychangingduetotheincreaseofmetabolizingproductionandconsumption…     

考虑延缓纠正的双应力加速可靠性增长试验方法

目的 缩短传统加速可靠性增长试验时间,以及考虑延缓纠正方式对产品可靠性的影响。方法 提出考虑延缓纠正的双应力加速可靠性增长试验方法,首先,采用基于延缓纠正AMSAA模型跟踪可靠性增长过程,并采用极大似然估计方法估计模型参数;其次,以温度和振动作为加速应力为例,开展加速寿命试验,获得试验数据,基于广义艾琳模型,通过最小二乘估计方法得到加速系数;然后,将产品可靠性外推到正常应力水平。结果 航空蓄电池应用案例分析表明,与基于单应力加载的高应力加速可靠性增长试验相比,所提方法能够缩短29.4%的试验时间,并且采用延缓纠正方式对产品的可靠性有影响。结论 为产品在双应力加载方式和采用延缓纠正方式下开展高应力加速可靠性增长试验的可靠性评估提供了技术手段。     

关于广义拟duo-环的正则性

刻画了广义拟duo-环并主要得到以下几个结果：（1）R是广义左拟duo-环当且仅当且是MELQ的左极小Abel环．（2）设R是一个环,R是强正则环且仅当是广义左左拟duo的左GP-V-环．参7．     

中国经济增长与物质消耗关系的实证研究

本文运用广义最小平方法和处理面板数据的固定影响模型,利用我国各省市1995-2009年物质消耗指数、人均GDP和人均固定资产投资等跨部门的时间序列数据,分析经济增长与物质消耗的关系。其主要结论如下:经济增长与物质消耗呈现正向关系,没有表现出明显的去物质化。固定资产投资对物质消耗趋势在统计上具有很好的解释力。固定效应模型下的广义最小二乘法对于处理跨部门的时间序列数据有明显的效果,固定效应模型的省际差异项有效地刻画了物质消耗与经济增长相关关系的省级差异。我国目前仍处于有形资产的积累阶段,为了达到发达国家的固定资产积累水平,必要的基础设施建设不能缺少。产业结构的差异会影响物质消耗与经济增长的关系强度,第一产业相对于第二产业需要更多的物质消耗。经济发展水平同样会影响物质消耗与经济增长的关系强度,发达地区相对于欠发达地区需要的物质消耗更少。