A comparison of non-linear least square and GLUE for model calibration and uncertainty estimation for pesticide transport in soils   总被引：1，自引：0，他引：1  

Danrong Zhang  Keith Beven  Andr Mermoud 《Advances in water resources》2006,29(12):1924-1933

The problems of calibrating soil hydraulic and transport parameters are well documented, particularly when data are limited. Programs such as CXTFIT, UUCODE and PEST, based on well established principles of statistical inference, will often provide good fits to limited observations giving the impression that a useful model of a particular soil system has been obtained. This may be the case, but such an approach may grossly underestimate the uncertainties associated with future predictions of the system and resulting dependent variables. In this paper, this is illustrated by an application of CXTFIT within the generalised likelihood uncertainty estimation (GLUE) approach to model calibration which is based on a quite different philosophy. CXTFIT gives very good fits to the observed breakthrough curves for several different model formulations, resulting in very small parameter uncertainty estimates. The application of GLUE, however, shows that much wider ranges of parameter values can provide acceptable fits to the data. The wider range of potential outcomes should be more robust in model prediction, especially when used to constrain field scale models.  相似文献   

山西大同雁门关测震台误码原因试验研究及解决措施     

薛志文 《山西地震》2006,(4):27-32

通过对山西大同雁门关测震台信道特征及误码特征的分析,提出误码产生原因及改善信道的总体思路和试验方法。并对改进后的系统运行情况进行对比分析,发现,雁门关测震台的信道误码减少了。而且同样的改进措施对其他台也有效果,提高了台网系统运行率和地震数据的利用率。  相似文献   

Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam   总被引：2，自引：1，他引：2  

Vu Thi Minh Nguyet  Nico Goldscheider 《Hydrogeology Journal》2006,14(7):1147-1159

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.  相似文献   

Vertical impulse measurements of mines buried in saturated sand     

LC Taylor  RR Skaggs  W. Gault 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(1):19-28

The ultimate aim of our overall task, of which the effort described in this paper is a part, is to be able to model the impulsive output of buried charges and the response of targets of interest. It is not practical or cost-effective to determine the response of all targets of interest to buried charges of all sizes by testing them. In order to have confidence in our models, however, they must be validated by a modest number of tests. A critical element in modelling the response of a target is the ability to model the loading function. The load a buried charge applies to a target above it when the charge detonates can be characterized in terms of the vertical impulse. The vertical impulse is a function of the size of the charge, its depth of burial, and the properties of the soil in which it is buried. The primary objective of the effort described in this paper is to determine the load a known charge places on a non-responding target so the data can be used to validate our models.

For model validation, a large number of detonator-scale experiments have been conducted by the University of Maryland (Fourney et al. [1]). It was also necessary to conduct a modest number of experiments at a larger scale, nine in total, to ensure that the results of the detonator-scale tests can be satisfactorily scaled up. Of the nine large-scale experiments conducted, seven were conducted with 5 or 10 lb cast TNT charges. All experiments were conducted in sand that was as nearly fully water-saturated as possible. The objective of the experiments was to determine the vertical impulse applied to a non-deforming target plate above the charge.

The large-scale experiments were conducted using the Vertical Impulse Measurement Fixture (VIMF) at the Army Research Laboratory, Aberdeen, MD. The VIMF is a unique facility that has been designed specifically to measure accurately the vertical impulse from buried charges weighing up to 8 kg.

This paper describes the VIMF and its instrumentation, test methods and test results. The results obtained demonstrate that in some cases, when the soil is saturated sand, explosive 'bubble' effects similar to those encountered in shallow water are encountered.  相似文献   

Critical specific stream power in gravel-bed rivers     

F. Petit  F. Gob  G. Houbrechts  A.A. Assani 《Geomorphology》2005,69(1-4):92-101

Experiments with marked pebbles were carried out on different sized rivers of the Belgian Ardenne (catchment areas varying from less than 1 km² to 2700 km²). Specific stream power required to cause bedload movement was evaluated and critical values were obtained. Three types of relationship between critical specific stream power (ω₀) and grain size (D) were established. The values for ω₀ in the largest river (the Ourthe) were the lowest and were close to the values obtained for mountainous rivers carrying large boulders. In medium sized rivers (catchment area between 40 and 500 km²), the critical unit stream power was higher. It is likely that it is due to the bedform's greater resistance. This resistance would use up some of the energy that can cause movement and transport of bedload. The amount of resistance of the bedform can be expressed as bedform shear stress (τ″), determined by the relationship between grain shear stress (τ′—that determines movement and transport of the bedload) and the total shear stress (τ). This ratio varies between 0.4 and 0.5 in the medium sized rivers, compared to 0.7 in the Ourthe. In headwater streams (less than 20 km²), there is greater loss of energy due to bedform resistance (τ′/τ<0.3). Critical specific stream power is higher in this third type of river than in the other two.  相似文献   

A Bayesian hierarchical method for multiple-event seismic location     

Stephen C. Myers  Gardar Johannesson  William Hanley 《Geophysical Journal International》2007,171(3):1049-1063

  相似文献   

Copepod distribution as an indicator of epikarst system connectivity   总被引：2，自引：0，他引：2  

Tanja Pipan  David C. Culver 《Hydrogeology Journal》2007,15(4):817-822

The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnice, Postojna Planina Cave System, Škocjanske Jame, Županova Jama), and of ten species from 13 drips in one US cave (Organ Cave, West Virginia). The dripping water comes from epikarst, the skin of karst. A significant fraction of the copepod species found (nine species in Slovenia and three in West Virginia) occurred over a maximum linear extent of 100 m. These and other localized distributions probably resulted from colonization of epikarst by an ancestral surface population in a single location, with subsequent lateral spread in the direction of epikarst flow. This suggests that the distribution of copepods could potentially be used to trace major flow paths in epikarst without the need for the injection of dyes or other tracers.

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Résumé La distribution de 27 espèces de copépodes a été déterminée dans 35 zones de percolation de quatre grottes slovènes (Dimnice, système de grottes Postojna Planina, Škocjanske Jame, Županova Jama) et grace à dix espèces de 13 zones de percolation d’une grotte des Etats-Unis (Grotte Organ, Ouest de la Virginie). L’eau de percolation provient de l’épikarst, la partie supérieure du karst. Une fraction importante des espèces de copépodes trouvées (9 espèces en Slovénie et 3 dans l’Ouest de la Virginie) s’étendait sur une longueur maximum de 100 m. Ces dernières ainsi que d’autres distributions localisées étaient probablement issues de la colonisation par une population ancienne de surface, de zones localisées de l’épikarst, puis par une dispersion latérale dans la direction de l’écoulement dans l’épikarst. Ceci suggère que la distribution des copépodes pourrait potentiellement être utilisée pour identifier les principales trajectoires d’écoulement dans l’épikarst, sans utiliser l’injection de colorants ou d’autres traceurs.

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Resumen Se determina la distribución de 27 especies de copépodo en 35 gotas de cuatro cavernas de Eslovenia (Dimnice, Sistema de Caverna Planina Postojna, Jame Škocjanske, y Jama Županova), y de diez especies en 13 gotas de una caverna de Estados Unidos (Caverna órgano, Virginia Occidental). El agua que gotea se deriva del epikarst, la piel del karst. Una fracción significativa de las especies de copépodos encontradas (9 especies en Eslovenia y 3 en Virginia Occidental) se presentaron en una extensión linear máxima de 100 m. Estas y otras distribuciones localizadas resultaron probablemente de colonización del epikarst por poblaciones superficiales ancestrales en una sola localización, con una expansión lateral subsiguiente en la dirección de flujo epikárstico. Esto sugiere que la distribución de copépodos podría tener un uso potencial para trazar rutas de flujo principales en epikarst sin tener la necesidad de inyectar colorantes u otros trazadores.

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现代板块运动驱动地幔块体置换度及地幔混合的研究   总被引：1，自引：1，他引：1       下载免费PDF全文

傅容珊  韩力波  黄建华  单斌  刘军 《地球物理学报》2007,50(5):1409-1417

定义了描述地幔混合程度的新的统计学量度——地幔块体对流置换度和对流混合扩散度.地幔块体对流置换度等于至少被置换一次的块体数与地幔总块体数之比，对流混合扩散度等于示踪元初始体密度与示踪元终体密度之比.本研究假设地幔对流是稳定的，上地幔和下地幔的黏滞性存在差异，其驱动力为板块运动或地幔中密度异常分布.实验中地幔被划分为20736 个块体（5°×5°×300 km），2376个示踪元被放置在地幔顶部100 km深度或底部100 km高度的5°×5°的网格点上.模型计算表明， 地幔块体对流置换度随运转时间变化.就全地幔而言，在系统运行四十亿年后，大多数模型对应的块体对流置换度均超过80%，而上地幔块体置换度则达到90%.这预示大多数的地幔块体将被来自其他位置的块体所取代.对于放置在地幔顶部或底部，浓缩于很小空间10°×10°(间距0.25°) 中的两组1681个示踪元而言，尽管其对流混合扩散度在开始有较大的差异，但是在运行一段时间之后，此两组对应的对流混合扩散度均趋于常数，示踪元比较均匀地分布于全地幔之中.由以上的结果可以推断，在经历了四十五亿年的演化过程后，由于对流的作用使地幔基本上已经均匀混合，地幔中不大可能存在尺度大于5°×5°×300 km的异常块体.  相似文献   

Field characterization of vertical bromide transport in a fractured glacial till     

William G. Harrar  Lawrence C. Murdoch  Bertel Nilsson  Knud Erik S. Klint 《Hydrogeology Journal》2007,15(8):1473-1488

A study of the fracture distribution, hydraulic properties, groundwater levels and the transport of bromide was conducted to characterize vertical transport in the oxidized and reduced zones of a fractured glacial till. Detailed vertical profiles of groundwater levels and solute concentrations were obtained over a 4.5-year period. Vertical migration occurred at several time scales, as a low concentration front was rapidly transported at rates of 100–500 m/year ahead of a slower moving main plume, which advanced at rates of 0.2–0.8 m/year. Concentrations in the leading edge of the plume displayed a high degree of spatial variability over short vertical distances through day 1,000. Late in the test, the influence of matrix diffusion became apparent as concentration patterns developed from being irregular to more uniform distributions. Calculations show that the mass within the low concentration plume front accounts for less than 1% of the total solute mass. Simulation of the breakthrough curves using a simple one-dimensional advection-dispersion model of transport in porous media indicates that vertical transport is dominated by advection. Furthermore, the results indicate that vertical transport of solutes in oxidized and reduced zones of the till can be adequately simulated using an equivalent porous media.  相似文献   

在GIS软件中的拓扑关系及判定法则     

史与正  蒋卫国等 《湖南地质》2001,20(4):309-312,315

地理信息系统,在地理空间信息和数据库属性数据的管理中的地位和作用越来越明显,数字地图是GIS输入、输出的主要形式,数字地图通过内业矢量化或全野外采集的方式形成后,数据的关系依靠拓扑技术进行处理。论述了数据中点、线、面之间的关系,制定判定法则,判定它们的拓扑关系或添加一定的关系,使大量杂乱无章的数据建立或转换成另一种拓扑关系以达到处理信息的目的。特别就“交点计数检验法”进行了完善,保证了各种特殊情况处理方法的正确性。根据判别规则和方法,可以实现“缓冲区分析”、“自动裁剪线”、“自动形成封闭面”等拓扑处理功能。  相似文献