P-III分布参数的概率权重矩法S函数计算   总被引：4，自引：1，他引：3  

宋松柏 《水文》2008,28(5)

概率权重矩法是一种估计统计分布参数的方法.本文根据不完全Γ函数在无限区间积分,推导了P-Ⅲ分布参数的S函数的计算公式.通过现有计算公式比较,其计算结果具有较高的计算精度,避免了的大量的数值积分计算.文中公式只要借助于计算编程进行求解,给定超几何函数项一定的截断误差,其运算具有较高的运行速度.文中计算公式是一种P-Ⅲ分布参数S函数的计算途径.  相似文献   

含沙量对草地坡面径流泥沙沉积和水力特性的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

潘成忠  马岚  上官周平 《水科学进展》2008,19(6):857-862

通过室内模拟试验,在坡度为3°和9°、流量为20和60L/min条件下研究了不同浓度(0～350kg/m3)含沙水流流经草地的泥沙沉积过程及其水力学特性。结果表明,坡面泥沙沉积量随含沙量的增加而增大,3°时泥沙沉积率与含沙量呈正相关,而9°时沉积率与含沙量呈反势。坡度对泥沙沉积影响显著,而在相同坡度条件下,两种流量试验的泥沙沉积量无明显差异。相同坡面坡上部位流速小于坡下部位,且含沙量对坡面流速影响较小。在相同坡度和流量条件下,水流雷诺数随含沙量的增大而减小。3°时水流阻力系数和曼宁糙率均随含沙量的增加而增大,而9°时含沙量对阻力影响不明显,因此在土壤侵蚀较严重地区进行坡面水文过程演算时需考虑含沙量对缓坡糙率的影响。  相似文献   

Temporal dynamics of soil erosion and rainfall erosivity as geoindicators of land degradation in Northwestern Argentina     

《Quaternary International》2006,142(1):147-161

The subtropical region of Northwestern Argentina displays severe environmental deterioration due to a combination of factors, including seasonally contrasting weather, highly erodable loessic soils, a topography with varied slopes, and natural vegetation coverage restricted by deforestation and agricultural advance, in addition to exploitation of natural resources by people. The aim of the present research was to determine the landscape degradation, using as geoindicators the increase in erosion by water and the pluviometric gradient variations through time.Two regions were chosen as sample areas in the province of Tucumán: the eastern foothills and plain of the Southeastern Ranges (Western Chaco); and the intermountain valley of Tafí. Erosion increase was quantified by measuring the length of gullies and ravines; and the sedimentation in the artificial lake (La Angostura) located in the center of the valley of Tafí. Climate changes were analyzed by means of the rainfall erosivity variations in both sample areas during the last 30 years.The lineal increase in erosion is closely related to the pluvial dynamics. Nevertheless, this erosive intensification is also dependent on the interaction of environmental factors and human activities (deforestation, land use changes, unrestricted agriculture).  相似文献   

黄土坡面侵蚀产沙时空演变的REE示踪技术研究   总被引：2，自引：0，他引：2       下载免费PDF全文

薛亚洲  刘普灵  杨明义  琚彤军 《水科学进展》2005,16(2):174-180

室内交叉布设不同的稀土氧化物,通过人工模拟次降雨,在同一试验条件下,对坡面侵蚀沿顺坡方向和深度方向的演变过程同时展开研究。结果表明:REE示踪技术对定量研究土壤侵蚀具有较高的精度;降雨前期,片蚀与细沟侵蚀发育程度基本相当;后期细沟侵蚀占据坡面侵蚀的主导地位,其侵蚀平均加速度和平均侵蚀率分别是片蚀的15倍、9倍;试验结束,细沟侵蚀占据坡面总侵蚀的90%;本试验条件下,坡面下1/3区域为侵蚀活跃带。  相似文献   

区域水资源可持续利用的综合评价方法   总被引：8，自引：4，他引：8       下载免费PDF全文

宋松柏  蔡焕杰 《水科学进展》2005,16(2):244-249

水资源可持续利用指标体系及评价方法是水资源可持续利用研究的核心问题之一。以复合系统理论为基础,将水资源、社会经济和环境组成的复合系统定义为水资源可持续利用系统(RSWRS系统)。应用Bossel可持续发展基本定向指标框架,建立了水资源可持续利用指标评价体系。应用系统综合评价法,权重采用基于Bossel评分标准,以参考状态的离差平方和最大法计算,建立了以RSWRS系统发展综合指数和发展态势度量模型。以陕西省为例,进行了水资源可持续利用的综合定量评价。  相似文献   

Erosion response to anthropogenic activity and climatic changes during the Holocene: case studies in northwestern China and southern Norway     

HE Xiubin  TANG Keli  John A Matthews  Geraint Owen 《地理学报》2002,12(4):467-471

Soil erosion assessment and prediction play critical roles in addressing problems associated with erosion control or soil conservation. The past dynamics of soil erosion can provide valuable information for us to understand the relations of soil erosion to environmental change and anthropogenic activity. The present paper has compared Holocene climatic changes in northwestern China with those in southern Norway, and investigated the past dynamics of erosion activity during the Holocene. Modern soil erosion on the Loess Plateau is a combination of the intensive natural erosion and human-induced erosion, the latter being four times greater than the former. Because of global warming and increasing human activities, climate on the Loess Plateau is becoming dryer and more unstable, causing an enhanced erosion problem and water scarcity. In the arctic-alpine region of southern Norway, however, the global warming and regional wetting caused expansion of the largest European ice cap. This has accentuated the erosion in that region, with a higher frequency of avalanches and debris flows.  相似文献   

薄层水流速度测量系统的研究   总被引：14，自引：0，他引：14       下载免费PDF全文

夏卫生  雷廷武  赵军  张晴雯  高佩玲 《水科学进展》2003,14(6):781-784

根据水流影响电解质扩散和其导电特性的分析,结合电解质脉冲在水流中迁移的数学模型,设计了薄层水流速度测试系统。用Visual Basic语言编写了操作系统,实现了数据采集、参数计算和分析自动化。实验和模拟结果表明,模拟水槽实验中用流量法测量的流速和电解质扩散法测量的水流速度误差很小,说明用此系统测量浅层水流的流速是可行的。  相似文献   

Bio-climatic imprints on a Holocene loess palaeosol from China     

He Xiubin  Tian Junliang  Tang Keli  Sun Jianzhong  John A Matthews 《Journal of Asian Earth Sciences》2004,22(5):455

Micromorphology, heavy minerals, pollen and soil properties were examined in a typical Holocene loess profile in the north of the Loess Plateau, consisting of a palaeosol (locally known as the Ansai palaeosol) underlain by the Malan loess and overlain by modern loess. The palaeosol consists of an upper humus-rich (AB) horizon over a clay-rich (Bt) horizon. The humus-rich horizon is intensely weathered, contains precipitated calcitic material derived from the overlying modern loess, and has both high pollen content and diversity. Clay coatings in the clay-rich horizon indicate formation by eluviation–illuviation of clay. Pedogenetic characteristics and pollen analysis imply that the vegetation during the time of most intensive soil development is likely to have been a warm-temperate forest. A complex interpretation of the loess–palaeosol sequence recognizes several development stages. The phase of soil development, maximum and minimum limiting ages for which are ca. 8800 and 4400 ¹⁴C years BP, involved continuing but reduced loess deposition, and successive Holocene bio-climatic environment overprinted new features on the palaeosol.  相似文献   

The role of evaporation on the formation of secondary Cu-hydroxy minerals in the arid Namaqualand soil system of South Africa     

《Applied Geochemistry》2014

The soils surrounding the Spektakel mine in the arid Okiep copper district of the Northern Cape Province, South Africa have been exposed to Cu containing acid mine drainage (AMD) for well over a century. This has led to acute soil contamination with Cu concentrations present as high as 10 wt%. Despite the sulphate-rich environment, associated with AMD, the Cu-hydroxy chloride mineral, atacamite [Cu₂(OH)₃Cl] is the exclusive secondary Cu mineral identified in the soils. Brochantite [Cu₄(OH)₆SO₄], the sulphate equivalent was not detected. Evaporation is a major hydrologic process in the arid soil system, thus the chemical evolution of the saline, metal containing brine was determined both experimentally and using PHREEQC modelling in the presence and absence of calcite. In samples that evaporated in the absence of calcite, the pH of the evaporating solution progressively decreased to below 3.5, whereas the solution in contact with calcite retained a circumneutral pH throughout the evaporation process. Thus in the absence of calcite, evaporation alone will not favour the formation of Cu-hydroxy minerals. Chemical activities of the evaporating solutions were modelled using the SIT.dat database of PHREEQC. This allowed the inclusion of aqueous complexes into the activity calculations of the evaporating solutions. Contrary to the conservative molality evolution of sulphate, the evolution of the sulphate activity was substantially suppressed due to the formation of MgSO₄⁰ aqueous complexes. We propose that these MgSO₄⁰ aqueous complexes are responsible for the absence of brochantite whereas the conservative chloride ion is more available for secondary Cu mineral formation. This suggests that ion pairs and aqueous complexes play an important role in determining the speciation of evaporite minerals and should be included in the modelling of such systems.  相似文献   

电感耦合等离子体质谱法测定铅合金中的微量杂质元素镉和锡   总被引：1，自引：1，他引：0  

郝原芳  刘新  宋丽华  李丽君  徐英奎 《岩矿测试》2016,35(4):378-383

铅合金中的镉和锡由于含量较低,国家标准方法均为单一元素分析,步骤繁琐,检出限高,难以达到理想的检出要求。本文建立了应用电感耦合等离子体质谱法(ICP-MS)测定铅合金中微量级(μg/g级)杂质元素镉和锡的分析方法。采用单一的低浓度硝酸溶解铅合金,用低温慢溶的方式使样品溶解更加完全,减少了多离子对仪器的干扰;通过铅基体匹配和加入酒石酸保证了标准与样品介质的一致性,同时避免了锡的水解;以~(103)Rh作为内标元素,~(111)Cd和~(118)Sn作为测量同位素克服了质谱干扰。方法检出限为镉0.05 ng/g、锡0.04 ng/g,比国家标准方法的检出限(1~6μg/g)低,精密度小于4%。该方法试剂用量少,减少了处理样品的复杂性,实现了合金中微量级元素的准确测定。  相似文献