Applying the Kuhn–Tucker model to estimate the value of recreational ecosystem services in Sicily

This paper applies the Kuhn–Tucker model to estimate recreation demand of parks in Sicily. We estimate a fixed coefficient specification and a random coefficient specification to take into account heterogeneity across visitors. Estimates suggest a diversity of preferences across the population and that parks with higher level of quality attributes are more likely to be visited. We also simulate two sets of hypothetical policy scenarios to evaluate and compare the recreational value of each park and the welfare impacts of changes in a quality attribute.     

DEVELOPMENT AND EVALUATION OF A DIMENSIONLESS UNIT HYDROGRAPH1

ABSTRACT: A generalized unit hydrograph method is developed and evaluated for ungaged watersheds. A key component in this method is the value of a dimensionless storage coefficient. Procedures to estimate this coefficient are given using calibrated values from 142 rainfall-runoff events gaged in watershed located mainly in the Eastern US. Only limited success was obtained in predicting this storage coefficient. Thirty-seven, independent rainfall-runoff events were used to test the proposed technique. The generalized unit hydrograph predicted the observed runoff hydrographs fairly well with considerable improvement in accuracy over the SCS dimensionless unit hydrograph. Approximately one-half of test storms had percent errors in predicted peak flow rates that were less than 34 percent compared to percent error of 88 percent with the SCS method.     

长江三峡库区横向扩散系数研究初探

进行长江长寿段示踪剂岸边有限时段连续投放试验,求得横向扩散系数及其与流速、水深、流量、污染物浓度等关系。以长寿湖大沙坝河段为类比试验,预测得到三峡库区在90％保证率的最枯月流量下典型江段的横向扩散系数,并可用于库区的污染带计算。     

BOD5测定过程中稀释系数的确定

如何选取稀释系数是测定生化需氧量的关键。笔者通过理论推导,求出稀释系数与生化指标的关系,并经过汇总、分析本厂一年中进水的生化指标,从而求得稀释系数。实践证明该稀释系统适合本厂进水水质生化需氧量的测定。     

ESTIMATING BASEFLOW VOLUME AND ITS UNCERTAINTY1

ABSTRACT: By using the exponential baseflow recession equation it is possible to estimate from a single discharge measurement the total volume of stream discharge during a baseflow period. If the discharge measurement is properly centered in the baseflow period the resulting estimate will be fairly precise, even if the baseflow recession coefficient is not known. Furthermore, based on an assumed probability distribution of the baseflow coefficient it is possible to estimate the uncertainty of the baseflow volume estimate. Estimates of baseflow volume and their uncertainty are potentially useful for estimating water budgets of lakes.     

FREQUENCY OF DRY DAY SEQUENCES1

ABSTRACT: Data from 100 stations were used to prepare a generalized characterization of the extremely long dry day sequences in the United States. Maps are presented showing the magnitude of the two-year, dry day sequences for 1 mm threshold and the coefficient of variation of the items used in the extreme value analysis. For the United States, the average coefficient of variation for dry periods is 30 percent as compared with that for maximum 24h rainfalls which is 37 percent. An example is presented for computing the longer return periods.     

基于灰色关联度分析的河南省节能减排策略探析

采用灰色关联度分析法,考察城镇化率、人均GDP、产业结构多元化系数ESD、能源结构多元化系数ECSD、能源强度、人口总量6种驱动因素对河南省能源消费量的影响程度及驱动河南省能源消费增长的内在机理,得出城镇化水平的提高是河南省能源消费量增加最主要的原因和驱动因素,关联系数为0.937;产业化结构多元化系数和人均GDP与能源消费量之间的关联度次之,灰色关联系数为分别为0.887和0.822。针对以上结论,探索河南省节能减排策略,为河南省提高经济发展质量,走不以牺牲农业和粮食生产为代价的"三化"协调的科学发展之路提供理论支持。     

室内挥发性有机化合物综合散发量及其特征

基于室内建筑污染源散发特性与汇效应机制分析,给出了建筑室内挥发性有机化合物（VOCs）综合散发量的计算模型,并进一步分析了材料内部扩散系数、气固界面分离系数和材料厚度对室内VOCs综合散发量的影响特征。研究结果表明,在近似稳定阶段室内VOCs综合散发量会随源材料内部扩散系数的增大而升高,而随源材料气固界面分离系数和材料厚度的增加而减小,且以源材料内部扩散系数的影响最为显著;同时,室内汇表面三类参数的增大均会使室内VOCs综合散发量降低;此外,在相同的环境参数条件下,室内VOCs综合散发量会因室内汇效应的存在而减小。     

Blade thickness effect on the aerodynamic performance of an asymmetric NACA six series blade vertical axis wind turbine in low wind speed

ABSTRACT

Vertical axis wind turbine (VAWT) is an economic and widely used energy converter for converting wind energy into useful form of energy, like mechanical and electrical energy. For efficient energy conversion in low wind speed and to have improved power coefficient of asymmetric blade VAWT, selection of optimum blade thickness is needed thus entailing its detailed investigation with respect to different operating wind speed conditions. Present study methodically explores the impact of thickness to chord (t/c) ratio on aerodynamic performance of a three bladed asymmetrical blade H-Darrieus VAWT at different low wind speed conditions by using 2D unsteady CFD simulations. The optimal t/c is obtained on the basis of maximum power coefficient and average moment coefficient of the turbine. The aerodynamic performance curves are obtained at different operating and t/c conditions and the performance insights are corroborated with the findings from the flow physics study to come to some concrete conclusions on the effects of the thickness to chord ratio. The present study identifies large blade curvature to create a large diverging passage on the blade suction surface as the prominent reason for aerodynamic performance drop at a high t/c ratio.     

Performance Model for a Horizontal Tube Falling Film Evaporator

A model is developed to predict the evaporative heat transfer coefficient in a horizontal tube-falling evaporator and has been applied to evaluate overall performance of a desalination unit. Performance variation with different parameters like operation temperature, type of water distribution system, mass flow rate of distilled water inside the exchanger are analyzed. It has been observed that the model is able to predict the trends of heat transfer characteristics of the evaporator reasonably well. However, at low liquid film flow rate conditions, the model overpredicts the heat transfer characteristics marginally. In order to improve the evaporative exchanger performance, it is observed that preheating of the liquid film before injection into the evaporator is desirable. Calculations are also performed to estimate the value of overall heat transfer coefficient for a typical desalination unit.     

西部地区SO_2总量控制方案合理性评估

通过新增工业产值、农用地面积、降雨强度和环保投资4个指标,引入信息熵对各指标进行权重分配,科学界定基尼系数合理性范围,构建了以改良基尼系数为度量标准的二氧化硫总量控制方案分配合理性的评价体系,并将其应用于"十二五"西部地区二氧化硫排放总量控制规划方案合理性评价工作中。研究结果表明,西部地区"十二五"SO2总量控制方案存在不合理,可优先考虑针对环保投资进行调整。     

青冰滩冰川水文特征初步分析

通过对青冰滩冰川的综合考察,对该地区2008-08-01日至08-31日的水文、气象以及水环境进行了连续观测。结果表明:冰川表面大量覆盖冰碛增加了冰川表面的反射率,加速了冰川消融;整个8月日均气温在8℃以下,气温的日较差较大,冰川消融期的降水以降雪和冰雹为主;冰川融水的电导率和溶解性固体相关系数可达0.98,两者与气温的相关度也可达到0.8以上。     

含油污泥薄层干燥特性及动力学模型分析

采用薄层干燥方式进行含油污泥热干燥的研究,引入薄层干燥模型对含油污泥干燥过程进行模拟,结果表明,Midilli模型比其他模型更适合含油污泥的薄层干燥分析。应用Fick扩散模型,得到80～140℃条件下含油污泥干燥的有效扩散系数变化范围为1.08×10-10～4.22×10-10 m2/s,其值随着温度升高而增大。根据Arrhenius经验公式建立温度与扩散系数的关系,得到含油污泥干燥时水分扩散的活化能为27.26kJ/mol。     

Pu在粉质粘土介质中的分配系数及其影响因素研究

本文以粉质粘土介质为研究对象，用批式法实验研究了Pu在砂土介质中的分配系数及其影响因素。研究结果表明：核素Pu在粉质粘土中的分配系数较大，反映该种地质介质对Pu具有较强的吸附阻滞性；另外，分配系数是一个随环境pH值、介质含水率及水中核素源项浓度而变化的量。     

MERITS OF STATISTICAL CRITERIA FOR THE PERFORMANCE OF HYDROLOGICAL MODELS1

ABSTRACT: The performance of a hydrological model is usually assessed first by visual inspection of the measured and computed hydrographs. Numerous statistical criteria are available for numerical evaluations of model accuracy in each single year, in a particular season of the year, or in a sequence of years or seasons. In the last case, the problem of computing the overall result has to be considered. If too many criteria are used and the criteria are switched frequently, an assessment of a model's performance becomes difficult for a potential user. Therefore, this paper concentrates on just three criteria and their combined evaluation: The Nash-Sutcliffe coefficient, which compares the model computed discharge with the average measured discharge; the “coefficient of gain from daily means” in which a uniform average discharge is replaced by daily average discharges; and the volumetric difference between the total measured and computed runoff. The three criteria are combined in a three dimensional representation that allows intercomparisons of model performance in a single diagram.     

ESTIMATION OF OPTICAL PROPERTIES OF WATER FROM SECCHI DISK DEPTHS1

ABSTRACT: Optical information on a water body is often required when only Secchi disk depths are available. Many limnologists and water managers have attempted to estimate diffuse light attenuation in water from Secchi depth data assuming a simple inverse relationship. However, we show theoretically that the product of Secchi depth and the diffuse attenuation coefficient is markedly dependent on the reflectance coefficient (“brightness”) of water. Data from 28 New Zealand lakes of diverse optical character demonstrated this dependence over a wide range of reflectance (1.1 to 35.9 percent). Uncritical estimation of attenuation coefficients for diffuse light from Secchi depths, using the currently available simple inverse expressions, is discouraged because of the possibility of bias.     

Optimization of carbon dioxide absorption in a continuous bubble column reactor using response surface methodology

Carbon dioxide absorption using amine based solvents is a well-known approach for carbon dioxide removal. Especially with the increasing concerns about greenhouse gas emissions, there is a need for an optimization approach capable of multifactor calibration and prediction of interactions. Since conventional methods based on empirical relations are not efficiently applicable, this study investigates use of Response Surface Methodology as a strong optimization tool. A bubble column reactor was used and the effect of solvent concentration (10.0, 20.0 and 30.0 vol%), flow rate (4.0, 5.0 and 6.0 L min⁻¹), diffuser pore size (0.5, 1.0 and 1.5 mm) and temperature (20.0, 25.0 and 30.0°C) on the absorption capacity and also overall mass transfer coefficient was evaluated. The optimization results for maintaining maximum capacity and overall mass transfer coefficient revealed that different optimization targets led to different tuned operational factors. Overall mass transfer coefficient decreased to 34.7 min⁻¹ when the maximum capacity was the desired target. High reaction rate along with the highest absorption capacity was set as desirable two factor target in this application. As a result, a third scenario was designed to maximize both mass transfer coefficient and absorption capacity simultaneously. The optimized condition was achieved when a gas flow rate of 5.9 L min⁻¹, MEA solution of 29.6 vol%, diffuser pore size of 0.5 mm and temperature of 20.6°C was adjusted. At this condition, mass transfer coefficient reached a maximum of 38.4 min⁻¹, with a forecasted achievable absorption capacity of 120.5 g CO₂ per kg MEA.     

Application of Index Procedures to Flood Frequency Analysis in Turkey1

Abstract: This study investigates the regional analysis of annual maximum flood series of 48 stream gauging stations in the basins of the West Mediterranean Region in Turkey. The region is divided into three homogeneous subregions according to both Student‐t test and Dalrymple homogeneity test. The regional relationships of mean annual flood per unit area‐drainage area and coefficient of skew‐coefficient of variation are obtained. Two statistically meaningful relationships of the mean flood per unit area‐drainage area and a unique relationship between skewness and variation coefficients exist. Results show that the index‐flood method may be applicable to each homogenous subregion to estimate flood quantiles in the study area.     

A stochastic model for colloid transport and deposition

Profiles of retained colloids in porous media have frequently been observed to be hyper-exponential or non-monotonic with transport depth under unfavorable attachment conditions, whereas filtration theory predicts an exponential profile. In this work we present a stochastic model for colloid transport and deposition that allows various hypotheses for such deviations to be tested. The model is based on the conventional advective dispersion equation that accounts for first-order kinetic deposition and release of colloids. One or two stochastic parameters can be considered in this model, including the deposition coefficient, the release coefficient, and the average pore water velocity. In the case of one stochastic parameter, the probability density function (PDF) is characterized using log-normal, bimodal log-normal, or a simple two species/region formulation. When two stochastic parameters are considered, then a joint log-normal PDF is employed. Simulation results indicated that variations in the deposition coefficient and the average pore water velocity can both produce hyper-exponential deposition profiles. Bimodal formulations for the PDF were also able to produce hyper-exponential profiles, but with much lower variances in the deposition coefficient. The shape of the deposition profile was found to be very sensitive to the correlation of deposition and release coefficients, and to the correlation of pore water velocity and deposition coefficient. Application of the developed stochastic model to a particular set of colloid transport and deposition data indicated that chemical heterogeneity of the colloid population could not fully explain the observed behavior. Alternative interpretations were therefore proposed based on variability of the pore size and the water velocity distributions.     

地面水中的非离子氨及其数学计算法

非离子氨的换算工作在我国才刚开始,由于存在不少问题,给标准执行中带来一定困难。本文从水化学实际出发,根据化学平衡原理,导出了水体中非离子氨分布系数(或百分率)的计算公式及其浓度的换算公式。既引入了水温,pH,还引入了离子强度,且介绍了两个水中离子强度的经验计算公式,使计算手续大为简化。本文提出的计算公式,不仅能满足淡水水体的需要,也能满足其它水体,如海水的需要。