Determining extreme parameter correlation in ground water models   总被引：4，自引：0，他引：4  

Hill MC  Osterby O 《Ground water》2003,41(4):420-430

In ground water flow system models with hydraulic-head observations but without significant imposed or observed flows, extreme parameter correlation generally exists. As a result, hydraulic conductivity and recharge parameters cannot be uniquely estimated. In complicated problems, such correlation can go undetected even by experienced modelers. Extreme parameter correlation can be detected using parameter correlation coefficients, but their utility depends on the presence of sufficient, but not excessive, numerical imprecision of the sensitivities, such as round-off error. This work investigates the information that can be obtained from parameter correlation coefficients in the presence of different levels of numerical imprecision, and compares it to the information provided by an alternative method called the singular value decomposition (SVD). Results suggest that (1) calculated correlation coefficients with absolute values that round to 1.00 were good indicators of extreme parameter correlation, but smaller values were not necessarily good indicators of lack of correlation and resulting unique parameter estimates; (2) the SVD may be more difficult to interpret than parameter correlation coefficients, but it required sensitivities that were one to two significant digits less accurate than those that required using parameter correlation coefficients; and (3) both the SVD and parameter correlation coefficients identified extremely correlated parameters better when the parameters were more equally sensitive. When the statistical measures fail, parameter correlation can be identified only by the tedious process of executing regression using different sets of starting values, or, in some circumstances, through graphs of the objective function.  相似文献   

The use of a non-lethal tool for evaluating toxicological hazard of organochlorine contaminants in Mediterranean cetaceans: new data 10 years after the first paper published in MPB     

Fossi MC  Marsili L  Neri G  Natoli A  Politi E  Panigada S 《Marine pollution bulletin》2003,46(8):972-982

In the Mediterranean Sea, top predators, and particularly cetacean odontocetes, accumulate high concentrations of organochlorine contaminants and toxic metals, incurring high toxicological risk. In this paper we investigate the use of the skin biopsies as a non-lethal tool for evaluating toxicological hazard of organochlorines in Mediterranean cetaceans, presenting new data 10 years after the paper published by Fossi and co-workers [Mar. Poll. Bull. 24 (9) (1992) 459] in which this new methodology was first presented. Some organochlorine compounds, now with worldwide distribution, are known as endocrine disrupting chemicals (EDCs). Here the unexplored hypothesis that Mediterranean cetaceans are potentially at risk due to organochlorines with endocrine disrupting capacity is investigated. High concentrations of DDT metabolites and PCB congeners (known as EDCs) were found in the different Mediterranean species (Stenella coeruleoalba, Delphinus delphis, Tursiops truncatus and Balaenoptera physalus). In this paper we also propose benzo(a)pyrene monooxygenase (BPMO) activity in marine mammal skin biopsies (non-lethal biomarker) as a potential indicator of exposure to organochlorines, with special reference to the compounds with endocrine disrupting capacity. A statistically significant correlation was found between BPMO activity and organochlorine levels (DDTs, pp(')DDT, op(')DDT, PCBs and PCB99) in skin biopsies of males of B. physalus. Moreover a statistical correlation was also found between BPMO activity and DDT levels in skin biopsies of the endangered Mediterranean population of D. delphis. These results suggest that BPMO induction may be an early sign of exposure to organochlorine EDCs and can be used for periodic monitoring of Mediterranean marine mammal toxicological status.  相似文献   

From a mountain-rural to a plains-urban society: implications of the 1981 Nepalese Census     

Goldstein MC  Ross JL  Schuler S 《Mountain research and development》1983,3(1):61-64

Preliminary results of the 1981 Nepal census are analyzed as to urbanization and population movement to the Terai. Noting the substantial shift in the pattern of Nepal's population distribution occurring between 1971-81, and projecting these rates of change for the future, the paper reports a process of transformation wherein Nepal is shifting from a rural hill and mountain society to an urban-subtropical plains (Terai) state. While the flow of migrants to urban areas and the Terai region is well known, the increase in rate of change poses a serious challenge for the Nepalese government. Economic development planning must readjust its goals and assumptions to take into account the massive metamorphosis that is occurring in Nepal. Development efforts aimed at rural hill and mountain areas may need to be reevaluated in light of the changing distribution of population.  相似文献   

基于GIS+BIM的三维建模方法研究     

罗军  吴彬彬  孙国辉 《测绘与空间地理信息》2023,(4):162-165+168+171

传统的GIS技术仅适用于宏观模型的展示,只能反映出建筑物外观和地理位置,无法去获取建筑物内部细节。建筑信息模型(building information modeling, BIM)主要应用于单体建筑,所构建的模型仅可以反映出建筑物各部件细节。本文主要研究利用GIS+BIM技术对建筑物设计的CAD数据进行数据转化,分析处理以及三维建模,最后实现BIM模型可视化。此方法使GIS的应用由室外走向室内,从宏观世界走向微观建筑。结果表明：GIS+BIM技术对智慧城市的数字化建设具有一定的参考意义。  相似文献   

Modeling the potential radionuclide transport by the Ob and Yenisey Rivers to the Kara Sea     

Paluszkiewicz T  Hibler LF  Richmond MC  Bradley DJ  Thomas SA 《Marine pollution bulletin》2001,43(1-6):111-121

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The 1997/1998 mass mortality of corals: effects on fish communities on a Tanzanian coral reef     

Lindahl U  Ohman MC  Schelten CK 《Marine pollution bulletin》2001,42(2):127-131

The abnormally high surface temperatures in the world's oceans during 1997/1998 resulted in widespread coral bleaching and subsequent coral mortality. An experiment was performed to study the effects of this coral mortality as well as the influence of the structural complexity on fish communities on a Tanzanian coral reef. Changes in fish communities were investigated on plots of transplanted corals after 88% of these corals had died. A distinct shift in fish community composition was found, although diversity was not affected. Fish abundance rose by 39% mostly due to an increase in herbivores, which seemed to benefit from enhanced algal growth on the dead corals. Fish abundance, species diversity and community composition were also strongly influenced by the structural complexity provided by the live and dead corals. This suggests that a coral reef can support abundant and diverse fish populations also after the corals have died as long as the reef structure is sustained.  相似文献   

Detection of Extended Thermal Infrared Emission around the Vega-like Source HD 141569     

Fisher RS  Telesco CM  Piña RK  Knacke RF  Wyatt MC 《The Astrophysical journal》2000,532(2):L141-L144

We report the detection of extended IR emission at 10.8 and 18.2 μm around the Vega-like source HD 141569. Mid-IR imaging with OSCIR on Keck II shows emission from dust extending out to 100 AU from the B9.5 Ve star. Our modeling of the dust places an upper limit of approximately 2 μm on the diameter of the mid-IR-emitting particles if they are Mie spheres of astronomical silicates. Comparison of our mid-IR images to the near-IR (1.1 μm) NICMOS images of HD 141569 (Weinberger et al. 1999) shows that the mid-IR emission originates at smaller distances from the star than the scattered near-IR light, as also previously observed for the archetype Vega-like source beta Pictoris.  相似文献   

一株产低温右旋糖苷酶海洋细菌的筛选和鉴定   总被引：1，自引：0，他引：1       下载免费PDF全文

吕明生  王淑军  房耀维  焦豫良  刘姝  葛亮  吴彬彬  李佳 《海洋科学》2011,35(5):32-37

从连云港海域筛选得到一株产低温右旋糖苷酶的菌株LP621,经形态特征、生理生化特征以及16S rDNA序列分析和鉴定,该菌株为Pseudoalteromonas tetraodonis.该茵产生低温右旋糖苷酶的最适作用温度为30℃,在80℃保温2.5 h后该酶仍具有40％以上的活性.目前尚无Pseudoalteromo...  相似文献   

花岗岩—水相互作用的定量模拟在Stripa矿床地下水研究...     

Beau.  C 吴彬 《华东地质学院学报》1990,13(3):21-24

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人造流体包裹体：一种水岩作用实验研究的新方法     

Bodn.  RJ 吴彬 《华东地质学院学报》1990,13(3):70-73

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