Markov chain Monte Carlo methods for conditioning a permeability field to pressure data   总被引：3，自引：0，他引：3  

Dean S. Oliver  Luciane B. Cunha  Albert C. Reynolds 《Mathematical Geology》1997,29(1):61-91

Generating one realization of a random permeability field that is consistent with observed pressure data and a known variogram model is not a difficult problem. If, however, one wants to investigate the uncertainty of reservior behavior, one must generate a large number of realizations and ensure that the distribution of realizations properly reflects the uncertainty in reservoir properties. The most widely used method for conditioning permeability fields to production data has been the method of simulated annealing, in which practitioners attempt to minimize the difference between the ’ ’true and simulated production data, and “true” and simulated variograms. Unfortunately, the meaning of the resulting realization is not clear and the method can be extremely slow. In this paper, we present an alternative approach to generating realizations that are conditional to pressure data, focusing on the distribution of realizations and on the efficiency of the method. Under certain conditions that can be verified easily, the Markov chain Monte Carlo method is known to produce states whose frequencies of appearance correspond to a given probability distribution, so we use this method to generate the realizations. To make the method more efficient, we perturb the states in such a way that the variogram is satisfied automatically and the pressure data are approximately matched at every step. These perturbations make use of sensitivity coefficients calculated from the reservoir simulator.  相似文献   

Spatial Variation in Diameter Structures of Forests in Lassen Volcanic National Park,California*     

Albert J. Parker 《The Professional geographer》1992,44(2):147-160

Variation in seedling/sapling densities and stand diameter forms for six coniferous tree species is related to stand structural development and to elevation and topography in Lassen Volcanic National Park, California. Understory density patterns reflect differences in species tolerance; densities decrease with stand development for shade intolerant pines, but increase for shade tolerant firs and mountain hemlock. Pine species exhibit reverse-J diamter structures on recently disturbed sites, and decreaser and random forms elsewhere. More tolerant fir species show topographically mediated patterns of diameter structure, with reverse-J form common on northerly exposures and upland sites, but with decreaser and random forms on more xeric slopes. Interaction among species tolerance, environmental setting, and disturbance history yields a complex mosaic of stand diameter structures in the Lassen landscape.  相似文献   

Performance of a mixed-waste landfill amid geologic uncertainty—learning from a case study: Altamont Hills,California, U.S.A.     

Michael J. Taffet  Albert L. Lamarre  June A. Oberdorfer 《Environmental Geology》1991,18(3):185-194

The Jharia coalfield is the most important and active minig region; it experiences groundwater inflow and affects groundwater levels in overlying aquifers, and it provides the basis for a conceptual model of the hydrogeological impacts of coal mining. The several sandstone aquifers of the overburden are separated by aquitards that limit vertical hydraulic connection, but the inflow responds to seasonal events and seems to be linked to shallow groundwater behavior. The mine drainage behavior suggests a hydraulic connection between the mine and the shallower groundwater system. The greatest declines are directly above the panels, with an immediate response to coal mining. The inflow is localized by natural and induced fracture zones and is mostly into recent workings. The groundwater behavior is controlled by hydraulic property changes caused by mine-induced fracturing. The hydrological and chemical qualities of the shallow groundwater regime in 13 mining collieries in Mukunda Block have been investigated. Water samples collected from 30 shallow monitoring dug wells were chosen for the study. Rainfall, runoff, and infiltration rates have been calculated in the area. The water-quality plottings were used to interpret the distribution of individual chemical parameters and in predicting the water quality. The underground mine water has been classified as: (1) unconfined groundwater in the calcareous siltstone and sandstone—its composition is Na, Ca, SO₄ and Na-MgHCO₃ with moderate total dissolved solids (TDS) 200–1480 ppm; (2) the deep groundwater originating from the coal seams and associated sediments in the near-surface environments—this is a Na-HCO₃ water with higher TDS; and (3) spoil dump waters are essentially Na-HCO₃ with high TDS. This article presents some hydrologic results and conclusions relating to the hydrogeological and environmental impacts of the coal mining in the Jharia coalfield.  相似文献   

Amino acids derived from Titan tholins     

Khare BN  Sagan C  Ogino H  Nagy B  Er C  Schram KH  Arakawa ET 《Icarus》1986,68(1):176-184

An organic heteropolymer (Titan tholin) was produced by continuous dc discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mbar pressure, roughly simulating the cloudtop atmosphere of Titan. Treatment of this tholin with 6N HCl yielded 16 amino acids by gas chromatography after derivatization of N-trifluroacetyl isopropyl esters on two different capillary columns. Identifications were confirmed by GC/MS. Glycine, aspartic acid, and alpha- and beta-alanine were produced in greatest abundance; the total yield of amino acids was approximately 10(-2), approximately equal to the yield of urea. The presence of "nonbiological" amino acids, the absence of serine, and the fact that the amino acids are racemic within experimental error together indicate that these molecules are not due to microbial or other contamination, but are derived from the tholin. In addition to the HCN, HC2CN, and (CN)2 found by Voyager, nitriles and aminonitriles should be sought in the Titanian atmosphere and, eventually, amino acids on the surface. These results suggest that episodes of liquid water in the past or future of Titan might lead to major further steps in prebiological organic chemistry on that body.  相似文献   

Spatial, seasonal and ontogenetic variation in diet of Northeast Arctic Greenland halibut (Reinhardtius hippoglossoides)   总被引：2，自引：0，他引：2  

Hovde  S. C.; Albert  O. T.; Nilssen  E. M. 《ICES Journal of Marine Science》2002,59(2):421-437

  相似文献   

The phytoplankton bloom response to wind events and upwelled nutrients during the CoOP WEST study     

Frances P. Wilkerson  Adria M. Lassiter  Richard C. Dugdale  Albert Marchi  Victoria E. Hogue 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):3023

In the coastal waters off northern California, seasonal wind-driven upwelling supplies abundant nutrients to be processed by phytoplankton productivity. As part of the Coastal Ocean Processes: Wind Events and Shelf Transport (CoOP WEST) study, nutrients, CO₂, size-fractionated chlorophyll, and phytoplankton community structure were measured in the upwelling region off Bodega Bay, CA, during May–June 2000, 2001 and 2002. The ability of this ecosystem to assimilate nitrate (NO₃) and silicic acid/silicate (Si(OH)₄) and accumulate particulate material (i.e. phytoplankton) was realized in all 3 years, following short events of upwelling-favorable winds, followed by periods of relaxed winds. This was observed as phytoplankton blooms, dominated by chlorophyll in cells greater than 5 μm in diameter, that reduced the ambient nutrients to zero. These communities were located over the near-shore shelf (<100 m depth) and were dominated by diatoms. An optimal window of 3–7 days of relaxed winds, following an upwelling pulse, was required for chlorophyll accumulation. The large-celled phytoplankton that result are likely important players in coastal new production and carbon cycling.  相似文献   

Test of three methods to detect the overbank flow from water level time‐series analysis     

O. Navratil  M. B. Albert  P. Breil 《水文研究》2010,24(17):2452-2464

In this study, we propose to identify morphological and hydraulic characteristics related to overbank flows in the water level time‐series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km² with contrasted geology, land use and rainfalls regime) show that overflow mechanisms at the river‐reach scale can be systematically identified in the water level frequency distribution estimated with the peaks‐over‐threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water‐level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Spitzer spectroscopy of carbon stars in the Small Magellanic Cloud     

Eric Lagadec  Albert A. Zijlstra  G. C. Sloan  Mikako Matsuura  Peter R. Wood  Jacco Th. van Loon  G. J. Harris  J. A. D. L. Blommaert  S. Hony  M. A. T. Groenewegen  M. W. Feast  P. A. Whitelock  J. W. Menzies  M.-R. Cioni 《Monthly notices of the Royal Astronomical Society》2007,376(3):1270-1284

  相似文献   

Multi-proxy climate and environmental records from a Holocene eutrophic mire,southern taiga subzone,West Siberia     

Irina V. Kurina  Elena E. Veretennikova  Anna A. Il’ina  Marina L. Egorova  Lyudmila V. Salisch  Vladimir N. Dolgin  Albert V. Udaloi  Evgeniya A. Golovatskaya  Egor A. Dyukarev  Sergei V. Smirnov 《Boreas: An International Journal of Quaternary Research》2023,52(2):223-239

Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi-proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well-documented long-term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.  相似文献   

Planning for resettlement: building partnerships for,by, and with Indigenous peoples     

Kumasaka  Osamu  Bronen  Robin  Harrington  Elise  Knox-Hayes  Janelle  Laska  Shirley  Naquin  Albert  Patrick  Andy  Peterson  Kristina  Tom  Stanislaus 《GeoJournal》2021,87(2):307-327

Efforts in the United States to plan or implement relocation in response to climate risks have struggled to improve material conditions for participants, to incorporate local knowledge, and to keep communities intact. Mixed methodologies of community geography provide an opportunity for dialogue and knowledge-sharing to collaboratively diagnose the challenges of climate adaptation led by communities. In this article, we advance a participatory practice model for the co-creation of knowledge initiated during a two-day workshop with members from the Biloxi-Chitimacha-Choctaw Tribe from Isle de Jean Charles in Louisiana, Yup’ik people from Newtok Village in Alaska, and researchers from the MIT Resilient Communities Lab. Building on prior scholarship of indigenizing climate change research, this article shares the experience of the workshop to support knowledge exchange and dialogue, with the goal of understanding how to build participatory and non-extractive community-academic partnerships. We reflect on the community values and principles used to guide this workshop to inform more inclusive and co-produced research partnerships, and pedagogies that can improve and assist the self-determination of groups impacted by climate change. Workshop presentations and discussions highlight interconnected themes of resources, systems & structures, regulatory imbalance, and resilience that underpin climate resettlement. We reflect on the narratives presented by members of both Indigenous tribes and NGO partners that illustrate the shortcomings of resettlement planning practices past and present as perpetuating existing inequality. In response to this structured knowledge exchange, we identify potential roles for community-academic partnerships that aim to improve the equity of existing resettlement models. We propose approaches for incorporating traditional knowledge into the pedagogy, discourse, and practice of academic planning programs.

  相似文献