避雷针保护范围验算数学模型的确定

主要针对现有国家标准中避雷针保护范围确定的问题 ,即多是给予形状上的描述 ,而在实际设计或验算过程中通常计算量很大且重复工作多 ,笔者为应对上述的问题 ,提出了新的思路和新方法 ,建立了避雷针保护范围计算的数学模型 ,且编制了相应软件。     

COALBED METHANE PRODUCT WATER CHEMISTRY IN THREE WYOMING WATERSHEDS1

ABSTRACT: The Powder River Basin in Wyoming has become one of the most active areas of coalbed methane (CBM) development in the western United States. Extraction of methane from coalbeds requires pumping of aquifer water, which is called product water. Two to ten extraction wells are manifolded into one discharge point and product water is released into nearby unlined holding ponds. The objective of this study was to evaluate the chemistry, salinity, and sodicity of CBM product water at discharge points and associated holding ponds as a function of watershed. The product water samples from the discharge points and associated holding ponds were collected from the Cheyenne River (CHR), Belle Fourche River (BFR), and Little Powder River (LPR) watersheds during the summers of 1999 and 2000. These samples were analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS), alkalinity, sodium (Na), calcium (Ca), magnesium (Mg), potassium (K), sulfate (SO₄^2‐), and chloride (C^1‐). From the chemical data, practical sodium adsorption ratio (SARp) and true sodium adsorption ratio (SARt) were calculated for the CBM discharge water and pond water. The pH, EC, TDS, alkalinity, Na, Ca, Mg, K, SARp, and SARt of CBM discharge water increased significantly moving north from the CHR watershed to the LPR watershed. CBM discharge water in associated holding ponds showed significant increases in EC, TDS, alkalinity, Na, K, SARp, and SARt moving north from the CHR to the LPR watershed. Within watersheds, the only significant change was an increase in pH from 7.21 to 8.26 between discharge points and holding ponds in the LPR watershed. However, the LPR and BFR exhibited larger changes in mean chemistry values in pH, salinity (EC, TDS), and sodicity (SAR) between CBM product water discharges and associated holding ponds than the CHR watershed. For instance, the mean EC and TDS of CBM product water in LPR increased from 1.93 to 2.09 dS/m, and froml,232 to 1,336 mg/L, respectively, between discharge and pond waters. The CHR exhibited no change in EC, TDS, Na, or SAR between discharge water and pond water. Also, while not statistically significant, mean alkalinity of CBM product water in BFR and LPR watersheds decreased from 9.81 to 8.01 meq/L and from 19.87 to 18.14 meq/L, respectively, between discharge and pond waters. The results of this study suggest that release of CBM product water onto the rangelands of BFR and LPR watersheds may precipitate calcium carbonate (CaCO₃) in soils, which in turn may decrease infiltration and increase runoff and erosion. Thus, use of CBM product water for irrigation in LPR and BFR watersheds may require careful planning based on water pH, EC, alkalinity, Na, and SAR, as well as local soil physical and chemical properties.     

STREAM DISCHARGE PREDICTION VIA A GRID BASED SOIL WATER ROUTING WITH PADDY FIELDS1

ABSTRACT: A grid based daily hydrologic model for a watershed with paddy fields was developed to predict the stream discharge. ASCII formatted elevation, soil, and land use data supported by the GRASS Geographic Information System are used to generate distributed results such as surface runoff and subsurface flow, soil water content, and evapotranspiration. The model uses a single flow path algorithm and simulates a water balance at each grid element. A linear reservoir assumption was used to predict subsurface runoff components. The model was applied to a 75.6 km² watershed located in the middle of South Korea, and observed stream flow hydrographs from 1995 and 1996 were compared to model predictions. The stream flow predictions of 1995 and 1996 generally agreed with the observed flow, resulting in a Nash‐Sutcliffe efficiency R² of 0.60 and 0.62, respectively. The hydraulic conductivity for percolating water through the saturated layer affected baseflow generation. The levee height of the paddy influenced the time and magnitude of the surface runoff, depending on irrigation management. The model will be used for making low flow management decisions by evaluating the role of each land use to stream flow, especially in case of paddy decrease by gradual urbanization of a watershed.     

建筑物塌陷损坏评价的物元模型及其应用

矿产采掘和地下水资源开采造成的地表塌陷是一类较为严重的地质灾害,地表的塌陷必然会对依附于地球表层的建筑物造成不同程度的损害,建筑物损害的量化评价是地表塌陷损害工程评估的一项重要内容。本文应用可拓学的理论和方法,基于可拓学中的可拓集合变换和相关函数分析法,给出了受塌陷影响建筑物损害评价的经典域物元和节域物元,并建立了建筑物损害量化评价的物元模型。通过具体的计算示例说明了该方法的应用步骤,并对该方法的合理性进行了验证,为建筑物塌陷损坏评价提供一种新的方法。     

土与结构相互作用体系振动台模型试验数值模拟研究(英文)

运用土与结构动力相互作用 (SSI)有限元三维分析软件 SASSI2 0 0 0对一个土与结构动力相互作用体系振动台模型试验进行了模拟计算。对振动台模型试验作了简单的介绍 ,并详细叙述了试验的建模方法。对于试验中的刚性地基和柔性地基条件 ,El- centro波、Taft波和 5 0年超越概率为 10 %的南京人工波等三种地震波输入 ,三个加速度峰值水平 0 .1g、0 .2 g、0 .3g及两个水平向地震波输入的各种组合工况均进行了计算。在数值计算中 ,假设地基土为覆盖于基岩上的半无限粘弹性水平成层土 ,采用等效线性模型考虑土的动力非线性的影响 ;上部结构用三维杆系有限元单元模拟 ,楼板用四结点壳单元模拟 ,每个结点有三个平动自由度和三个转动自由度 ,模型试验中所施加的人工质量均匀分布于壳单元上 ;基础视为平板基础 ,用八结点块体单元模拟 ,每个结点有三个平动自由度。将试验结果与计算结果进行对比较 ,结果表明 :计算所建立的模型较好地模拟了相互作用体系在地震荷载下的反应性状 ,计算结果与试验结果吻合较好 ,SSI效应对结构地震反应有很大影响     

关于建立许家峪生态农业示范村的可行性研究

生态农业示范村建设是进行综合生态农业示范体系研究的基础,也是神态农业经营理念和技术推广的重要途径。因此,地理、交通、自然和人文环境的选择,生产经营模式的确定对生态农业经营效益和示范影响效果至关重要。本文通过对许家峪村的现状和作为冀东生态农业示范村的优势和存在问题以及适宜的经营模式进行了剖析和阐述。     

PREDICTIVE MODEL FOR NITRATE LOAD IN THE BULL RUN WATERSHED,OREGON1

ABSTRACT: Predictive models for nitrate in four streams in the Bull Run Watershed in the Cascade Mountains of Oregon were developed from a record of 17 years of nitrate samples. The models are time series regression models written in terms of Log(nitrate load). The independent variables are logarithm of 14-day mean daily stream discharge, current day's precipitation, logarithm of the previous day's precipitation, total precipitation for the previous seven days, a hydrograph position variable that indicates rising or falling limb, and average maximum air temperature for the preceding 14 days. The models describe annual cycle and seasonable trends and variations in nitrate load, but are unable to describe large day to day variations like those associated with hydrograph peaks.     

河流水质灾害中的S—P方程稳态分析和临界氧亏计算

污染物对水环境的影响主要发生在枯水期，此时水流状态处于稳态．Streeter－phelps（S－P）方程能预测简单稳态条件下的水质状况，并具有较高的计算织亏的精度．     

自然灾害变动的集成预测模型及其应用

本文提出了以非线性回归拟合发展趋势、正弦函数逼近周期变动和马尔可夫链刻划随机扰动的集成预测模型，并应用于山东省农业自然灾害成灾面积的变动规律模拟，得到了较好的预测效果。理论和实践表明，集成预测模型优于传统的单模型预测，为预测具有复杂机制的自然灾害演变提供了一种新方法。