EVALUATION OF METHODS FOR ESTIMATING STREAM WATER QUALITY PARAMETERS IN A TRANSIENT MODEL FROM STOCHASTIC DATA1

ABSTRACT: In this study the estimation of parameters in water quality models represented by linear first order partial differential equations is investigated. Two sets of simulated input-output data, one with input noise and the other with output measurement error, were used. The parameters were estimated by a gradient technique (Bard's method) and a pattern search technique. The results indicate that the output measurement error significantly affects the values of parameter estimates as compared to the noise added to the input. Bard's method consistently gave results with a smaller sum of square value.     

建筑火灾风险评价技术初探

在分析建筑火灾发生原因的基础上 ,建立了建筑火灾风险评估因素集。并运用模糊评价法对建筑物的火灾安全进行了风险评价 ,通过评价得出建筑物所属的安全等级。该方法可用于保险公司对投保建筑的鉴别与筛选 ,同时可使管理者及时采取措施 ,以减少火灾危险性。     

Regional Lake Trophic Patterns in the Northeastern United States: Three Approaches

N   = 11,076). Results were compared to a large, nonrandomly sampled data set for the same area compiled by Rohm and others and contrasted with lake trophic state information published in the National Water Quality Inventory: 1994 Report to Congress [305(b) report. Lakes across the entire Northeast were identified by EMAP data as 37.9% (±8.4%) oligotrophic, 40.1% (±9.7%) mesotrophic, 12.6% (±7.9%) eutrophic, and 9.3% (±6.3%) hypereutrophic. Lakes in the ADI and NEU generally are at a low, nearly identical trophic state (96% oligotrophic/mesotrophic), while those in the CLP are much richer (45% eutrophic). EMAP results are similar to results of the Rohm data set across the entire region. In the CLP, however, EMAP identified approximately 45% of the lakes as eutrophic/hypereutrophic, while the Rohm data set identified only 21% in these categories. Across the entire Northeast, the 305(b) report identified a much higher proportion (32.2%) of lakes in eutrophic condition and a much smaller proportion (19.8%) in oligotrophic condition than did the EMAP survey data (12.5% ± 7.9% and 37.9% ± 8.5%, respectively). Probability sampling has several advantages over nonrandom sampling when regional resource condition assessment is the goal.     

Variations in oxygen and some related pollution parameters in some streams in ITU Area of Nigeria

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地下水环境评价中分布参数随机性的空间统计分析

地下水环境评价中各种空间分布参数往往具有复杂的不确定性，对分布参数空间变化的二重性特征进行了分析，论述了空间分布参数统计分析的原理与方法。由于所采用的方法能够弥经典概率统计方法对地下水环境评从价中空间分布参数随机性分析的不足。     

遗传模拟退火算法在水质模型参数估值中的应用研究

在传统遗传算法 (GeneticAlgorithms,GA)基础上引入模拟退火技术 (SimulatedAnnealing,SA) ,提出了遗传模拟退火算法 (GSA) ,并将其应用到水质模型参数估值中。计算结果表明 ,GSA法综合了 2种优化方法各自的优点 ,不但克服了传统GA容易早熟的缺点 ,还加强了算法的收敛速度 ,因而具有良好的优化性能。不同的参数估值方法比较进一步验证了新方法的有效性。GSA法在环境优化领域中将具有广阔的应用前景     

Divergence of carbon dioxide fluxes in different trophic areas of Taihu Lake,China

IntroductionCarbondioxide(CO2 )isaprincipalgreenhousegasandthereforetheirair waterexchangesareimportantproblemsinterrestrialecosystemsforclimatechangestudy(Frankignoulle ,1 998;Chimel,2 0 0 1 ) .ThedirectionofCO2 gasexchange(evasionorinvasion)isdependentonthedirectionoftheCO2concentrationgradientbetweentheairandthesurfacewater;themagnitudeoftheexchangedependsadditionallyonthegasexchangecoefficient,k.Alloflakesinland ,withitssmallareabutlargeatmosphericCO2 fluxrange ,playanimportantroleinev…     

植被对风沙土风蚀作用的影响

以植物模型、风沙土为实验材料，以风洞模拟实验为研究手段得出初步结论：地表粗糙度为植被特征参数的函数，随植被盖度的增加呈幂函数增加；随植被作用区面积蛎呈线性增加；与行状植物的排列方向和主风向夹角的平方根成正比。在盖度相同的条件下，均匀分布较丛状分布可产生较大的粗糙度。风蚀率随植被盖度的减少呈指数增加。植被盖度对风沙土风蚀作用的影响可划分为３种程度类型：大于６０％为轻度风蚀和无风蚀。６０％￣２０％为中     

我国若干湖泊水库的营养状态指数TSI_c及其与各参数的关系

基于我国２０多个湖泊水库的不同营养状态特征，首次得出了适用于我国若干湖泊的营养状态指数ＴＳＩｃ及其与各参数的关系，通过对这些湖泊的ＴＳＩｃ与ＴＳＩｍ值比较，指出ＴＳＩｃ比ＴＳＩｍ更适合于描述生物量与营养盐呈线性响应的我国这类湖泊的营养状态，此外还提出用相关加权法综合不同参数的营养状态指数，并用一个“综合”状态式来表示湖泊的营养状态。     

滦河冲洪积扇地下水脆弱性评价体系研究

根据滦河冲洪积扇的主要环境地质问题,选择包气带岩性、厚度等7个参数作为评价指标,建立该区地下水脆弱性评价体系,认为只有评价参数选择正确、适当,地下水脆弱性评价才能为地下水管理、保护和规划提供决策参考。