An Application of Bayesian Inverse Methods to Vertical Deconvolution of Hydraulic Conductivity in a Heterogeneous Aquifer at Oak Ridge National Laboratory   总被引：2，自引：0，他引：2  

Michael N. Fienen  Peter K. Kitanidis  David Watson  Philip Jardine 《Mathematical Geology》2004,36(1):101-126

A Bayesian inverse method is applied to two electromagnetic flowmeter tests conducted in fractured weathered shale at Oak Ridge National Laboratory. Traditional deconvolution of flowmeter tests is also performed using a deterministic first-difference approach; furthermore, ordinary kriging was applied on the first-difference results to provide an additional method yielding the best estimate and confidence intervals. Depth-averaged bulk hydraulic conductivity information was available from previous testing. The three methods deconvolute the vertical profile of lateral hydraulic conductivity. A linear generalized covariance function combined with a zoning approach was used to describe structure. Nonnegativity was enforced by using a power transformation. Data screening prior to calculations was critical to obtaining reasonable results, and the quantified uncertainty estimates obtained by the inverse method led to the discovery of questionable data at the end of the process. The best estimates obtained using the inverse method and kriging compared favorably with first-difference confirmatory calculations, and all three methods were consistent with the geology at the site.  相似文献   

The use of the simple genetic algorithm in finding the critical factor of safety in slope stability analysis   总被引：11，自引：0，他引：11  

Paul McCombie  Philip Wilkinson 《Computers and Geotechnics》2002,29(8):699-714

A simple genetic algorithm (SGA) is applied to the search for the minimum factor of safety in slope stability analysis. The method is shown to be superior to simple optimisation routines, which can find false minima, and to ‘brute force’ approaches, which require the analysis of a very large number of possibilities. An approach to implementing SGA is defined and refined, indicating principles which may be used in applying the method to other engineering problems.  相似文献   

Gold solubility, speciation, and partitioning as a function of HCl in the brine-silicate melt-metallic gold system at 800°C and 100 MPa     

Mark R. Frank  Philip A. CandelaPhilip M. Piccoli  Michael D. Glascock 《Geochimica et cosmochimica acta》2002,66(21):3719-3732

A vapor-undersaturated synthetic brine was equilibrated with metallic gold and a haplogranitic melt at 800°C and 100 MPa to examine the solubility, speciation and partitioning of gold in the silicate melt-brine-metallic gold system. The starting composition of the NaCl-KCl-HCl-H₂O brine was 70 wt.% NaCl (equivalent) with starting KCl/NaCl ranging from 0.5 to 1. KCl/HCl was varied from 3.2 to 104 to evaluate the solubility and partitioning of gold as a function of the concentration of HCl in the brine. Inclusions of brine were trapped in a silicate glass during quench. Inclusion-poor and inclusion-rich portions of glass were analyzed for gold and chloride by using neutron activation analysis. The inclusion-poor glass yielded an estimate of the solubility of gold and chloride in the silicate melt. The solubility of gold in the melt, at gold metal saturation, was estimated as ≈1 ppm. The solubility of gold in the brine was estimated by mass balance, given the concentration of gold and chloride in the inclusion-poor and inclusion-rich glasses. The solubility of gold metal at low-HCl concentrations in the brine, C_HCl^b, (3 × 10³ to 1.1 × 10⁴ ppm) is ≈40 ppm (by weight) and is independent of the HCl concentration under those conditions. For C_HCl^b of 1.1 × 10⁴ to 4.0 × 10⁴ ppm, the solubility of gold increased from 40 to 840 ppm, and the solubility is given by: log C_Au^b = [2.2 · log C_HCl^b] − 7.2(1) These data suggest that a significant amount of gold is not chloride complexed in brines at low-HCl concentrations (< 1.1 × 10⁴ ppm), but that gold-chloride complexes, possibly AuCl₂H, are important at elevated concentrations of HCl (> 1.1 × 10⁴ ppm). The calculated Nernst partition coefficient (D_Au^b/m) for gold between a brine and melt varied from 40 to 830 over a range of brine HCl concentrations of 3 × 10³ to 1.1 × 10⁴ ppm. Our results indicate a significant amount of gold can be transported by a brine in the magmatic-hydrothermal environment independent of the fugacity of sulfur in the system. Thus brines provide an effective mechanism for the scavenging of gold from a crystallizing melt and transport into an associated magmatic-hydrothermal system, regardless of their sulfur contents.  相似文献   

Rural industrialization, 'quality' and service: some findings from South Warwickshire and North Devon     

David Jarvis  Philip Dunham  & Brian Ilbery 《Area》2002,34(1):59-69

Studies of UK rural industrialization have traditionally sought to explain the success of rural SMEs (Small and Medium-sized Enterprises) in terms of their capacity for innovative or enterprising behaviour. In turn, this has led researchers to focus their attention on the material aspects of competitive behaviour, particularly those connected to technology and technological exploitation, at the expense of more intangible aspects such as the advantages gained from novel working practices and marketing strategies. In particular, the notion of 'quality' as a determinant of competitive behaviour, an idea gaining increased emphasis within literature concerning rural SMEs in the food, farming and craft sectors, has been neglected in wider studies of rural industrialization. However, this paper contends that both 'formal' and 'informal' constructions of quality are significant factors in the success of manufacturers outside these specific sectors.  相似文献   

Computational fluid dynamics and the physical modelling of an upland urban river     

Lin Ma  Philip J. Ashworth  James L. Best  Lionel Elliott  Derek B. Ingham  Leslie J. Whitcombe   《Geomorphology》2002,44(3-4)

This paper describes the application of a commercially available, three-dimensional computational fluid dynamic (CFD) model to simulate the flow structure in an upland river that is prone to flooding. Simulations use a rectangular channel geometry, smooth sidewalls and a bed topography obtained from the field site that contains a subdued pool–riffle sequence. The CFD model uses the RNG κ– turbulence closure scheme of Yakhot and Orszag (J. Sci. Comput. 1 (1986) 1), as implemented in FLUENT 4.4.4, with a free surface. Results are shown for numerical runs simulating a 1:100 year return interval flood. Output from the numerical model is compared to a physical model experiment that uses a 1:35 scale fibreglass mould of the field study reach and measures velocity using ultrasonic Doppler velocity profiling (UDVP). Results are presented from the numerical and flume models for the water surface and streamwise velocity pattern and for the secondary flows simulated in the numerical model. A good agreement is achieved between the CFD model output and the physical model results for the downstream velocities.Results suggest that the streamwise velocity is the main influence on the flow structure at the discharge and channel configuration studied. Secondary flows are, in general, very weak being below the resolution of measurement in the physical model and less than 10% of the streamwise velocity in the numerical model. Consequently, there is no evidence for a ‘velocity dip’. It is suggested that the subdued topography or inlet morphology may inhibit the development of secondary flows that have been recorded in previous flat-bed, rectangular open channel flows. A significant corollary of these results is that the morphological evolution of the pool–riffle sequence at high discharges may be controlled primarily by the downstream distribution of velocity and sediment transport with little role for lateral sorting and sediment routing by secondary flows. This paper also raises a number of issues that may be of use in future CFD modelling of three-dimensional flow in open channels within the geomorphological community.  相似文献   

Using the Internet to Integrate Thematic and Regional Approaches in Geographic Education     

Philip E. Steinberg  Andy Walter  Kathleen Sherman&#x;Morris 《The Professional geographer》2002,54(3):332-348

Geographers have long debated the superiority of regional versus thematic approaches to geographical analysis and geographic education. While most acknowledge that these two approaches are complementary, the task of implementing both approaches in a single introductory course remains challenging. “Global Change, Local Places,” an Internet–based course offered at Florida State University, attempts to fuse thematic and regional approaches using methodological and pedagogical techniques that emphasize student–centered learning and Internet technologies. Results of a student survey and analysis of student assignments suggest that this format was successful. Students expressed a high level of satisfaction with course content, and, although attainment of skills and knowledge was particularly hard to measure given the structure and goals of the course, students appear to have gained country–specific knowledge as well as skills in critical analysis using thematic concepts.  相似文献   

Visualization of wave-induced suspension patterns over two-dimensional bedforms   总被引：1，自引：0，他引：1  

Paul V. Villard  Philip D. Osborne 《Sedimentology》2002,49(2):363-378

High spatial and temporal resolution measurements of suspended sand concentration ( c ) over vortex ripples were collected with a three-transducer acoustic backscatter sensor (ABS) array, under irregular `natural' waves in a multidirectional wave basin. These measurements permit two-dimensional visualization of the movement of sediment-laden vortices over an individual vortex ripple under a series of waves. Patterns of sediment motion were tracked through consecutive zero-crossings in the horizontal velocity ( U ) record measured at 0·05 m above the ripple crest elevation. It was possible to trace the advection of individual sediment-laden vortices at the zero-crossings. During 73% of these events, shedding and advection of coherent suspension events occurred before the flow reversal associated with the zero-crossing. This may be caused by the bedforms retarding the near-bed flow inducing the eddy shedding before the zero-crossing. While at maxima in U , secondary suspension events with low c were observed to pass over the ripple crest moving with U measured at 0·05 m. This pattern is attributed to vortex shedding from adjacent bedforms and/or antecedent suspension events. The most energetic events appeared to persist for several wave cycles and reached heights of ≈0·20 m. These suspension events appeared to be more persistent when smaller waves follow larger waves, possibly as a result of weaker reversals in vorticity. Although the events appeared to be vertically coherent in the time series from the individual transducers, it is apparent through visualization that these events are associated with the pairing of antecedent and developing vortices.  相似文献   

The Mackenzie Delta: sedimentary processes and facies of a high-latitude, fine-grained delta   总被引：2，自引：0，他引：2  

Philip R. Hill  C. Peter Lewis  Simon Desmarais  Vassen Kauppaymuthoo  & Hasna Rais 《Sedimentology》2001,48(5):1047-1078

The Mackenzie Delta is a large fine‐grained delta deposited in a cold arctic setting. The delta has been constructed upon a flooding surface developed on a previous shelf‐phase delta. There are three principal depositional zones: the subaerial delta plain, the distributary channel mouth region and the subaqeous delta. The subaerial delta plain is characterized by an anastomosing system of high‐sinuosity channels and extensive thermokarst lake development. This region is greatly influenced by the annual cycle of seasonal processes including winter freezing of sediments and channels, ice‐jamming and flooding in the early spring and declining river stage during the summer and autumn. Deposition occurs on channel levees and in thermokarst lakes during flood events and is commonly rhythmic in nature with discrete annual beds being distinguishable. In the channel mouth environment, deposition is dominated by landward accretion and aggradation of mouth bars during river‐ and storm surge‐induced flood events. The subaqeous delta is characterized by a shallow water platform and a gentle offshore slope. Sediment bypassing of the shallow‐water platform is efficient as a result of the presence of incised submarine channels and the predominance of suspension transport of fine‐grained sediments. Facies of the shallow platform include silty sand with climbing ripple lamination. Offshore facies are dominated by seaward‐fining fine sand to silt tempestites. Sea‐ice scouring and sediment deformation are common beyond 10 m water depth where bioturbated muds are the predominant facies. The low angle profile of the shallow‐water platform is interpreted to be the combined response of a fine‐grained delta to (1) storm sediment dispersal; (2) autoretreat as a result of the increasing subaerial and subaqeous area of deposition as the delta progrades out of its glacial valley; (3) limited water depth above the underlying flooding surface; and (4) efficient nearshore bypassing of sediment through subice channels at the peak of spring discharge. Several indicators of the cold climate can be used as criteria for the interpretation of ancient successions, including thermokarst lake development, submarine channel scours, freeze–thaw deformation and ice‐scour deformation structures. Permafrost inhibits compaction subsidence and, together with the shallow‐water setting, also limits autocyclic lobe switching. The cold climate can thus influence stratal architecture by favouring the development of regional‐scale clinoform sets rather than multiple, smaller scale lobes separated by autocyclic flooding surfaces.  相似文献   

Sampling Colloids and Colloid-Associated Contaminants in Ground Water   总被引：2，自引：0，他引：2  

Debera A. Backhus  Joseph N. Ryan  Daniel M. Groher  John K. MacFarlane  Philip M. Gschwend 《Ground water》1993,31(3):466-479

  相似文献   

The round table discussion: Interactions and feedback between theory and experiment     

Philip Chatwin  Han van Dop  Steven Hanna  Michael Poreh  Brian Sawford  Roland Stull 《Boundary-Layer Meteorology》1993,62(1-4):435-448

  相似文献