Low-frequency dilatational wave propagation through fully-saturated poroelastic media     

Wei-Cheng Lo  Garrison Sposito  Ernest Majer 《Advances in water resources》2006

The strong coupling of applied stress and pore fluid pressure, known as poroelasticity, is relevant to a number of applied problems arising in hydrogeology and reservoir engineering. The standard theory of poroelastic behavior in a homogeneous, isotropic, elastic porous medium saturated by a viscous, compressible fluid is due to Biot, who derived a pair of coupled partial differential equations that accurately predict the existence of two independent dilatational (compressional) wave motions, corresponding to in-phase and out-of-phase displacements of the solid and fluid phases, respectively. The Biot equations can be decoupled exactly after Fourier transformation to the frequency domain, but the resulting pair of Helmholtz equations cannot be converted to partial differential equations in the time domain and, therefore, closed-form analytical solutions of these equations in space and time variables cannot be obtained. In this paper we show that the decoupled Helmholtz equations can in fact be transformed to two independent partial differential equations in the time domain if the wave excitation frequency is very small as compared to a critical frequency equal to the kinematic viscosity of the pore fluid divided by the permeability of the porous medium. The partial differential equations found are a propagating wave equation and a dissipative wave equation, for which closed-form solutions are known under a variety of initial and boundary conditions. Numerical calculations indicate that the magnitude of the critical frequency for representative sedimentary materials containing either water or a nonaqueous phase liquid is in the kHz–MHz range, which is generally above the seismic band of frequencies. Therefore, the two partial differential equations obtained should be accurate for modeling elastic wave phenomena in fluid-saturated porous media under typical low-frequency conditions applicable to hydrogeological problems.  相似文献   

Lidar and Sun photometer observations of atmospheric boundary-layer characteristics over an urban area in a mountain valley     

Nikolay Kolev  Ivan Grigorov  Ivan Kolev  P. C. S. Devara  P. Ernest. Raj  K. K. Dani 《Boundary-Layer Meteorology》2007,124(1):99-115

We present measurements of the vertical aerosol structure and the aerosol optical depth in the lower troposphere performed above the city of Sofia (an urban area situated in a mountain valley), western Bulgaria by means of a ground-based aerosol lidar operating continuously for a number of years. The lidar measurements were accompanied by measurements of the aerosol optical depth (AOD) in the visible and near infrared regions of the spectrum performed in October 2004 using Microtops II radiometers. The maximum values of the AOD were found to occur 1–2 h before the complete development of the atmospheric boundary layer, i.e. during the residual layer destruction, which confirms our hypothesis concerning the slope circulation effect on the processes taking place in the atmospheric boundary layer. The AOD values obtained by the lidar are lower than those taken by the sun photometer. Further, the AOD exhibits two different types of behaviour. In the case of a ‘clear atmosphere’ (i.e. in the absence of volcanic eruptions and/or dust transport from the Sahara) most of the aerosol accumulated within the atmospheric boundary layer over the urban area considered. The combined use of the two instruments allows the comparison between the optical characteristics of the atmospheric aerosol (e.g. aerosol extinction coefficient, etc.) obtained by the lidar and through an independent method (sun photometer).  相似文献   

Study on the Chemical Character of Water Soluble Organic Compounds in Fine Atmospheric Aerosol at the Jungfraujoch   总被引：1，自引：0，他引：1  

Zoltán Krivácsy  András Gelencsér  Gyula Kiss  Ernő Mészáros  Ágnes Molnár  András Hoffer  Tamás Mészáros  Zsolt Sárvári  Dóra Temesi  Bálint Varga  Urs Baltensperger  Stephan Nyeki  Ernest Weingartner 《Journal of Atmospheric Chemistry》2001,39(3):235-259

In this study the chemical nature of the bulk of water soluble organic compounds in fine atmospheric aerosol collected during summer 1998 at the Jungfraujoch, Switzerland (3580 m asl) is characterised. The mass concentration of water soluble organic substances was similar to those of major inorganic ions, and the water soluble organic matter was found to be composed of two main fractions: (i) highly polyconjugated, acidic compounds with a varying degree of hydrophobicity and (ii) slightly polyconjugated, neutral and very hydrophilic compounds. The contribution of both fractions to the total water soluble organic carbon was about 50%. Separation into individual components was impossible either by HPLC or capillary electrophoresis which indicates the presence of a high number of chemically similar but not identical species. Results obtained by ultrafiltration and HPLC-MS have shown that the molecular weights are of the order of several hundreds. Most of the protonation constants for the acidic compounds determined by capillary electrophoresis were in the range 10⁴–10⁷.  相似文献   

Seasonal variations in the vertical structure of water vapor optical depth in the lower troposphere over a tropical station     

P. Ernest Raj  P.C.S. Devara 《大气科学进展》1997,14(3):425-432

Spatio-temporal variations of water vapor optical depth in the lower troposphere (450-3850 m) over Punt (18o32’N, 73o51’E, 559 m Above Mean Sea Level), India have been studied over a period of five years. The mean ver-tical structure showed that the moisture content is greatest at the lowest level and decreases with increasing altitude, except in the south-west monsoon season (June to September) where an increase upto 950 m has been found. Optical depths are maximum in the monsoon season. The increase from pre-monsoon (March-May) to monsoon season in moisture content on an average is by about 58% in the above altitude range. The temporal variations in surface Rela-tive Humidity and optical depth at 450 m show positive correlation. The amplitude of seasonal oscillation is the larg-est at 1465 m altitude. The time-height cross-sections of water vapor optical depths in the lower troposphere showed a contrast between years of good and bad monsoon.  相似文献   

Effects of acid mine drainage on dissolved inorganic carbon and stable carbon isotopes in receiving streams     

Ernest W. Fonyuy  Eliot A. Atekwana 《Applied Geochemistry》2008

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Codification of Unnamed Minerals     

Smith  Dorian G. W.; Nickel  Ernest H. 《Journal of Petrology》2008,49(3):581-583

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Combining airborne laser scanning and Landsat data for statistical modeling of soil carbon and tree biomass in Tanzanian Miombo woodlands     

Mikael Egberth  Gert Nyberg  Erik Næsset  Terje Gobakken  Ernest Mauya  Rogers Malimbwi  Josiah Katani  Nurudin Chamuya  George Bulenga  Håkan Olsson 《Carbon balance and management》2017,12(1):8

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Effects of toxic chemicals on macrophage phagocytosis in two estuarine fishes     

Beverly Anne Weeks  J.Ernest Warinner 《Marine environmental research》1984,14(1-4)

The phagocytic efficiency of macrophages isolated from the kidney of spot, Leiostomus xanthurus, and hogchoker, Trinectes maculatus, was determined in fish captured from the Elizabeth River (Virginia) Macrophage phagocytosis was found to be markedly reduced in the Elizabeth River fish as compared to Ware River controls. The macrophage phagocytic activity of Elizabeth River fish returned to normal after the fish were held in clean water for several weeks. This indicates that the decreased phagocytic activity was related to exposure to Elizabeth River pollutants but may be reversible.  相似文献   

An unusual “pipe” in the Blackheath Beds at Bromley Hill,Kent     

E. Ernest S. Brown  F.H. Edmunds 《Proceedings of the Geologists' Association. Geologists' Association》1929,40(1):70-IN4

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Field meeting at Wateringbury and Mereworth: (Weald Research Committee.) Sunday,October 4th, 1936     

E. Ernest  S. Brown  G.W. Himus 《Proceedings of the Geologists' Association. Geologists' Association》1938,49(1):55-57

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