3D Simulations of Rayleigh–Taylor Instability Using “VULCAN/3D”     

Shimon M. Asida  Eli Livne  Josef Stein  Lior Metzker 《Astrophysics and Space Science》2005,298(1-2):363-367

The growth rate of the turbulent mixing zone, which develops from random perturbations under Rayleigh–Taylor instability, has been studied using the 3D version of the hydrodynamical code VULCAN. Previous studies show large differences between the α parameter of different codes. In its Eulerian mode VULCAN/3D employs Van–Leer scheme for the advection of all variables, and can also use interface tracking for multi-phase flows. Simulations using parallel version of VULCAN/3D give α of about 0.06, a value which agrees very well with experiments and some other simulations.  相似文献   

A spatial analysis of integrated risk: vulnerability of ecosystem services provisioning to different hazards in the Czech Republic     

Adam Pártl  David Vačkář  Blanka Loučková  Eliška Krkoška Lorencová 《Natural Hazards》2017,89(3):1185-1204

Ecosystem services are important to maintain the human well-being. However, their provisioning has been under the increasing pressure from both natural and socio-economic changes. This paper aims to assess the most significant hazards, such as water quality, nitrogen deposition, erosion, floods, invasive species, urbanisation and contaminated sites affecting delivery of ecosystem services in the Czech Republic. Using the multi-hazard assessment, the integrated risk index for ecosystem service provisioning was proposed. The spatial analysis based on this approach was then applied to the Czech Republic as a case study. The results showed that about 48% of the area falls into the very low risk category followed by 30%, 21%, and 1% for low, medium and high categories, respectively. Forest and wetland ecosystems were estimated to have the highest proportion of their total area among the highest risk values. Moreover, we found that the national parks appeared to have the highest proportion of medium- and high-risk classes among the natural areas. The approach presented in this study should aggregate the existing knowledge on ecosystem services and hazards and thus monitor the integrated risk. The results are intended to help with various planning and management decisions at both the national and regional levels and to bring more attention on the most problematic hot-spots.  相似文献   

A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models   总被引：1，自引：0，他引：1  

Lee H. Spangler  Laura M. Dobeck  Kevin S. Repasky  Amin R. Nehrir  Seth D. Humphries  Jamie L. Barr  Charlie J. Keith  Joseph A. Shaw  Joshua H. Rouse  Alfred B. Cunningham  Sally M. Benson  Curtis M. Oldenburg  Jennifer L. Lewicki  Arthur W. Wells  J. Rodney Diehl  Brian R. Strazisar  Julianna E. Fessenden  Thom A. Rahn  James E. Amonette  Jon L. Barr  William L. Pickles  James D. Jacobson  Eli A. Silver  Erin J. Male  Henry W. Rauch  Kadie S. Gullickson  Robert Trautz  Yousif Kharaka  Jens Birkholzer  Lucien Wielopolski 《Environmental Earth Sciences》2010,60(2):227-239

A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO₂ transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO₂ release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO₂ transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO₂ from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO₂ through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented.  相似文献   

Tidal river sediments in the Washington,D.C. area. II. Distribution and sources of organic contaminants     

Terry L. Wade  David J. Velinsky  Eli Reinharz  Christian E. Schlekat 《Estuaries and Coasts》1994,17(2):321-333

Concentration of aliphatic, aromatic, and chlorinated hydrocarbons were determined from 33 surface-sediment samples taken from the Tidal Basin, Washington Ship Channel, and the Anacostia and Potomac rivers in Washington, D.C. In conjunction with these samples, selected storm sewers and outfalls also were sampled to help elucidate general sources of contamination to the area. All of the sediments contained detectable concentrations of aliphatic and aromatic hydrocarbons, DDT (total dichlorodiphenyltrichloroethane), DDE (dichlorodiphenyldichloroethene), DDD (dichlorodiphenyldichloroethane), PCBs (total polychlorinated biphenyls) and total chlordanes (oxy-, α-, and γ-chlordane and cis + trans-nonachlor). Sediment concentrations of most contaminants were highest in the Anacostia River just downstream of the Washington Navy Yard, except for total chlordane, which appeared to have upstream sources in addition to storm and combined sewer runoff. This area has the highest number of storm and combined sewer outfalls in the river. Potomac River stations had lower concentrations than other stations. Total hydrocarbons (THC), normalized to the fine-grain fraction (clay + silt, < 63 μm), ranged from 120 μg g^?1 to, 1,900 μg g^?1 fine-grain sediment. The hydrocarbons were dominated by the unresolved complex mixture (UCM), with total polycyclic aromatic hydrocarbons (PAHs) concentrations ranging from 4 μg g^?1 to 33 μg g^?1 fine-grain sediment. Alkyl-substituted compounds (e.g., C1 to C4 methyl groups) of naphthalene, fluorene, phenanthrere + anthracene, and chrysene series dominated the polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons, saturated hydrocarbons, and the unresolved complex mixture (UCM) distributions reflect mixtures of combustion products (i.e., pyrogenic sources) and direct discharges of petroleum products. Total PCB concentrations ranged from 0.075 μg g^?1 to 2.6 μg g^?1 fine-grain sediment, with highest concentrations in the Anacostia River. Four to six C1-substituted biphenyls were the most-prevalent PCBs. Variability in the PCB distribution was observed in different sampling areas, reflecting, differing proportion of Arochlor inputs and degradation. The concentration of all contaminants was generally higher in sediments closer to known sewer outfalls, with concentrations of total hydrocarbon, PAHs, and PCBs as high as 6,900 μg g^?1, 620 μg g^?1, and 20 μg g^?1 fine-grain sediment, respectively. Highest PCB concentrations were found in two outfalls that drain into the Tidal Basin. Concentrations of organic contaminants from sewers draining to the Washington Ship Channel and Anacostia River had higher concentrations than sediments of the mid-channel or river. Sources of PCBs appear to be related to specific outfalls, while hydrocarbon inputs, especially PAHs, are diffuse, and may be related to street runoff. Whereas most point-source contaninant inputs have been regulated, the importance of nonpoint source inputs must be assessed for their potential addition of contaminants to aquatic ecosystems. This study indicates that in large urban areas, nonpoint sources deliver substantial amounts of contaminants to ecosystems through storm and combined sewer systems, and control of these inputs must be addressed.  相似文献   

The trade-off between density and other objectives: A re-examination of planning norms     

Eli Borukhov 《GeoJournal》1991,2(1):71-80

Residential density (dwelling units per area) affects the quality of life in urban environments in many direct and indirect ways. Determining the optimal level of density requires in each case, balancing all the relevant factors and influences, and should depend on the preferences of the potential residents and their financial resources.A residential neighborhood has many characteristics. Usually people trade off one characteristic against another. For instance: people can trade off density against cost or accessibility against space. The aim of good planning is to find the combination of characteristics that will give maximum level of satisfaction to the residents of a neighbourhood subject to the limitations of their budgets. Density standards should, therefore, be adapted to the preferences of the potential residents and their preferred compromise between the various attributes of their environment.To make things more complicated, the concept of density has many definitions, and different definitions are relevant when analysing the various effects of density. It seems that people do not perceive the gross residential density as it is measured, but are influenced by variables such as set-back distances, the percentage of building coverage and the like.Evidence is cited from an investigation in Kiryat-Gat which suggests that the perception of density is affected by other factors except the density itself.If people do not perceive the density as such but are affected by other factors, then modification of these factors is very important. If planners are to design neighborhoods according to the residents' preferences, they should have quantitative estimates of the residents' relative evaluation of these characteristics, including possible savings in the price of housing. The problems of investigating residential preferences are discussed, and examples of studies addressed to these questions are described.  相似文献   

Masters of mudbrick: Geoarchaeological analysis of Iron Age earthen public buildings at Ashdod-Yam (Israel)     

Marta Lorenzon  Benjamín Cutillas-Victoria  Eli Itkin  Alexander Fantalkin 《Geoarchaeology》2024,39(1):35-62

Excavations at Ashdod-Yam exposed a fortification system that features a massive mudbrick wall with large earthen ramparts laid on either side. This fortified horseshoe-shaped enclosure once surrounded what was likely a human-made harbor and an adjacent acropolis with complex earthen architecture, constructed and active during Iron Age IIB–C (eighth–seventh centuries B.C.E.). These Iron Age public structures are at the center of the current research. In this paper, we present the geoarchaeological analyses of Ashdod-Yam's earthen architecture. We applied a multidisciplinary methodology to new evidence for mudbrick manufacture with the goal of understanding the relationship between governing bodies and craftsmen. The analyses combine X-ray fluorescence, loss on ignition, environmental scanning electron microscopy, and thin-section petrography to investigate raw material procurement, manufacturing choices, and labor organization at Ashdod-Yam during Iron IIB–C. Construction techniques and the standardization of the mudbrick recipe point to a local enterprise regarding the site's public earthen architecture. Furthermore, the degree of labor organization must have been closely observed and supervised by a central political power. Thus, it is argued here that construction and maintenance of the site was carried out by the kingdom of Ashdod, either as a part of its own local initiative or on behalf of the Neo-Assyrian empire.  相似文献   

Poynting Robertson effects due to a logarithmic correction to the Newtonian potential     

Haranas  Ioannis  Gkigkitzis  Ioannis  Cobbett  Kristin  Hovesen  Gregory  Shah  Kay  Gauthier  Ryan  Cavan  Eli 《Astrophysics and Space Science》2021,366(9):1-16

Astrophysics and Space Science - We performed a detailed timing study of the Atoll source 4U 1705-44 in order to understand the accretion disk geometry. Cross correlation function (CCF) studies...  相似文献   

Erratum to: Potential impacts of increased coastal flooding in California due to sea-level rise     

Matthew Heberger  Heather Cooley  Pablo Herrera  Peter H. Gleick  Eli Moore 《Climatic change》2012,112(2):523-523

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Geomorphic inferences from regolith thickness, chemical denudation and CRN erosion rates near the glacial limit, Boulder Creek catchment and vicinity, Colorado   总被引：1，自引：1，他引：0  

David P. Dethier  Eli D. Lazarus 《Geomorphology》2006,75(3-4):384

Granitic regolith, developed in the Boulder Creek catchment and adjacent areas, records a history of deep weathering, some of which may predate Quaternary time. Field and well-log measurements of weathering, chemical denudation and rates of erosion derived from ¹⁰Be cosmogenic radionuclide (CRN) data help to quantify rates of landscape change in the post-orogenic Rocky Mountains. The density of oxidized, fractured bedrock ranges from 2.7 to about 2.2 g cm^− 3, saprolite and grus have densities between 2.0 and 1.8 g cm^− 3, and 30 soil samples averaged 1.6 ± 0.2 g cm^− 3. Highly weathered regolith in 540 wells averages 3.3 m thick, mean depth to bedrock in 1661 wells is 7 m, and the weathered thickness exceeds 10 m in relatively large local areas east of the late Pleistocene glacial limit. Thickness of regolith shows no simple relationship to rock type or structure, local slope, or distance from channels. Catchments in the vicinity of the Boulder Creek have an average CRN erosion rate of 2.2 ± 0.7 cm kyr^− 1 for the past 10,000 to 40,000 yr. Annual losses of cations and SiO₂ vary from about 2 to 5 g m^− 2 over a runoff range of 10 to nearly 160 cm.Using measured rates in simple box models shows that if a substantial fraction of void space is created by volume expansion in the weathering rock materials, 7 m of weathered rock materials could form in as little as 230 kyr. If density loss results mainly from chemical denudation and some volume expansion, however, the same weathering profile would take > 1340 kyr to form. Rates of erosion measured by CRN could be balanced by the rate of soil formation from saprolite if the annual solute loss from soil is 2.0 g m^− 2 and 70% of the density decrease from saprolite to grus and soil results from strain. Saprolite, however, forms from oxidized bedrock at a far slower rate and rates of saprolite formation cannot balance soil and grus losses to erosion. The zone of thick weathered regolith is likely an eroding relict landscape. The undulating surface marked by relatively low relief and tors is not literally a topographic surface of Eocene, Oligocene or Miocene age unless it was covered with deposits that were removed in Pliocene or Quaternary time.  相似文献   

Simultaneous time-domain deconvolution with application to the computation of receiver functions   总被引：5，自引：0，他引：5  

Harold Gurrola  G. Eli Baker  J. Bernard Minster 《Geophysical Journal International》1995,120(3):537-543

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