共查询到20条相似文献，搜索用时 31 毫秒
1.
Summary The paper is concerned with the investigation of the plane Lamb's problem in which a line load is suddenly applied on a magneto-elastic initially stressed conducting half-space bounded by a plane. The results obtained in this investigation are in agreement with the corresponding results of the classical plane Lamb's problem when the semispace is supposed to be initially unstressed and non-magnetic. 相似文献
2.
Summary The object of the present paper is to investigate the so-called planeLamb's problem in an initially stressed magneto-elastic semi-space bounded by a plane. The results obtained in this investigation are in agreement with the corresponding results of the classical planeLamb's problem when the semi-space is supposed to be initially unstressed and non-magnetic. 相似文献
3.
Summary The paper is concerned with the investigation of the magneto-elastic waves and disturbances in initially stressed conducting media. Firstly, (a) the steady state response to moving loads in a magneto-elastic initially stressed conducting medium under an uniaxial tension has been discussed. Secondly, (b) the Lamb's problem corresponding to a line load suddenly applied in a magneto-elastic initially stressed conducting half-space bounded by a plane under uniaxial tension has been investigated. The final results obtained in both cases are in agreement with the corresponding classical problems when the initial tension is zero and the magnetic field is absent. 相似文献
4.
A one‐dimensional, two‐layer solute transport model is developed to simulate chemical transport process in an initially unsaturated soil with ponding water on the soil surface before surface runoff starts. The developed mathematical model is tested against a laboratory experiment. The infiltration and diffusion processes are mathematically lumped together and described by incomplete mixing parameters. Based on mass conservation and water balance equations, the model is developed to describe solute transport in a two‐zone layer, a ponding runoff zone and a soil mixing zone. The two‐zone layer is treated as one system to avoid describing the complicated chemical transport processes near the soil surface in the mixing zone. The proposed model was analytically solved, and the solutions agreed well with the experimental data. The developed experimental method and mathematical model were used to study the effect of the soil initial moisture saturation on chemical concentration in surface runoff. The study results indicated that, when the soil was initially saturated, chemical concentration in surface runoff was significantly (two orders of magnitude) higher than that with initially unsaturated soil, while the initial chemical concentrations at the two cases were of the same magnitude. The soil mixing depth for the initially unsaturated soil was much larger than that for the initially saturated soil, and the incomplete runoff mixing parameter was larger for the initially unsaturated soil. The higher the infiltration rate of the soil, the greater the infiltration‐related incomplete mixing parameter. According to the quantitative analysis, the soil mixing depth was found to be sensitive for both initially unsaturated and saturated soils, and the incomplete runoff mixing parameter was sensitive for initially saturated soil but not for the initially unsaturated soil; the incomplete infiltration mixing parameter behaved just the opposite. Some suggestions are made for reducing chemical loss from runoff. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
D. S. Chandrasekharaiah 《Pure and Applied Geophysics》1973,109(1):1712-1717
Summary Transverse waves in an electrically conducting initially stressed elastic half-space with stress free boundary permeated by a magnetic field are investigated. The conditions for the existence of these waves is obtained and the velocity as well as the depth of penetration is calculated. In the absence of the initial stresses our results reduce to already known results. 相似文献
6.
M. A. Khan 《Pure and Applied Geophysics》1972,94(1):66-73
Summary A semi-infinite rod of piezoelectric material is initially at zero temperature. The deformation at any point of the rod is also zero initially. The radiation at the surface is equal to a prescribed temperature for all time. The velocity is kept zero initially. The distribution of temperature, stress, displacement, electric-field and entropy density have been worked out. 相似文献
7.
Summary The object of the present paper is to investigate the magneto-elastic surface waves in an initially stressed conducting medium. The theory of magneto-elastic surface waves in an initially stressed conducting medium has firstly been deduced and then it has been employed in investigating the particular cases of surface waves such as (i) Rayleigh waves (ii) Love waves and (iii) Stoneley waves. The wave-velocity equations obtained in different cases are in agreement with the corresponding classical results when the solid is initially unstressed and the magnetic field is absent or the material is non-magnetic. 相似文献
8.
Implications of Coulomb plasticity for the velocity dependence of experimental faults 总被引：2，自引：0，他引：2
Simulated fault gouges often deform more stably than initially bare surfaces of the same composition. It is important to understand why the sliding stability is enhanced because the presence of gouge on natural faults may have the same effect as seen in experiments, and thus explain the absence of earthquakes at shallow depths. Gouge stabilization in experiments has been attributed to positive contributions to velocity dependence within gouge layers from either dilation (Marone
et al., 1990) or grain fracture (Biegel
et al., 1989). In this study we test the hypothesis that some aspects of gouge and initially bare surface velocity dependence are identical by measuring the time-dependent constitutive parameterb. An important result follows however from stress analysis: if both sample configurations are frictional in the Mohr-Coulomb sense, each configuration is required to deform on planes of distinctly different orientation. The measured strength and velocity dependence will reflect this geometric difference. Our observed values ofb for simulated granite and quartz gouge are two to two and a half times smaller thanb for initially bare surfaces. This difference is completely accounted for if gouge is represented as a cohesionless-Coulomb plastic material. The analysis demonstrates the following points: 1) gouge deformation is fully consistent with Coulomb plasticity, 2) observed gouge velocity dependence is a function of observed strength and 3) the constitutive parameterb is the same for both bare surfaces and gouge. Furthermore, the results suggest that there is no time-dependent strengthening associated with stabilizing effects in gouge. These observations provide a framework for understanding how slip on initially bare surfaces and gouge deformation are related. 相似文献
9.
K. Miksch 《洁净——土壤、空气、水》1988,16(6):607-615
The general assumption that the quantity of the formazan formed is linearly proportional to the time of incubation cannot be confirmed in practice. A formation of formazan which is too low initially is due to the initially passive transport of TTC to the sites of action. A formazan formation which is initially very high occurs through non-enzymatic reduction of TTC by reducing substances in the environment outside the bacterial cells. During longer periods of incubation, especially during toxicological tests, the substrate may get exhausted, so that less formazan will be formed. For the correct determination of the dehydrogenase activity by means of TTC it is necessary to determine the period of incubation within which the increase of formazan is linearly proportional to time. The dehydrogenase activity can be exactly determined only from this period of time of incubation. 相似文献
10.
Saurendra Nath De 《Pure and Applied Geophysics》1972,99(1):55-60
Summary The paper deals with the propagation of waves in a magneto-elastic initially stressed conducting layer. The wave velocity equation obtained is in agreement with the classical result of Rayleigh and Lamb when the layer is initially unstressed and the magnetic field isabsent. 相似文献
11.
本文研究初始应力及磁场作用下导电粘弹体内的波动特性。首先导出有初始应力及磁场作用下导电粘弹体运动的基本方程,然后用它去研究流体静压力及单轴初始应力下波动方程的解,从平面简谐波的频散方程,分析了初始应力及磁场对波动传播的影响。粘弹体用Kelvin-Voigt模型,外磁场假定为均匀。所得结果表明,初始应力对波的影响随应力性质不同而有所差异,它既影响波的相速也影响波的衰减。磁场影响的大小决定于外磁场的强弱。从本文所得公式中,令外磁场为零,可得初始应力对波特性的影响;如令初始应力为零,就得到磁场对波的影响结果;令两者同时为零,即得粘弹波的经典结果。 相似文献
12.
农村单层砌体房屋中的居民的地震逃生问题是一个重要课题。本文对安全目标和安全区进行了等级划分,提出了判定地震逃生方法可行性的地震逃生安全函数;对农村单层砌体房屋中的地震逃生进行了一系列的模拟试验,初步得到了逃生时间与逃生者个体、逃生者环境的关系;对地震逃生案例进行分析,得到了农村单层砌体房屋中的地震逃生各种方法的可行性;提出了基于目标安全区的地震逃生方法,给出了不同条件下逃生者的地震逃生方法。 相似文献
13.
A review of rock mechanics studies in the United States pertinent to earthquake prediction 总被引：1，自引：0，他引：1
J. Byerlee 《Pure and Applied Geophysics》1978,116(4-5):586-602
Premonitory phenomena such as dilatancy, creep, acoustic emission, and changes in seismic velocity and attenuation, electrical resistivity, magnetic moment, and gas emission, which occur before fracture of initially intact rock and before stick-slip on faults or between finely ground surfaces of rock, have been reviewed and discussed in relation to earthquake prediction. This review is restricted to the results of laboratory experiments that have been carried out in the United States of America. 相似文献
14.
A simple and accurate cubic approximation to the solution of the Boussinesq equation is given in case of power-law flux boundary condition being imposed at the inlet of an initially dry aquifer. The new approximation overcomes the numerical intensity of the earlier cubic approximation of Telyakovskiy and Allen [Telyakovskiy AS, Allen MB. Polynomial approximate solutions to the Boussinesq equation. Adv Water Resour 2006;29(12):1767–79], while producing comparably accurate results. 相似文献
15.
Francesca Zuccarello Salvatore L. Guglielmino Viviana Battiato Lidia Contarino Daniele Spadaro Pado Romano 《Acta Geophysica》2009,57(1):15-23
This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high
resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising
flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially
characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline
of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following
legs of the flux tubes. These results are briefly discussed in the light of most recent models. 相似文献
16.
An application of waveform denoising for microseismic data using polarization–linearity and time–frequency thresholding 
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下载免费PDF全文 Jubran Akram 《Geophysical Prospecting》2018,66(5):872-893
Noise suppression or signal‐to‐noise ratio enhancement is often desired for better processing results from a microseismic dataset. In this paper, a polarization–linearity and time–frequency‐thresholding‐based approach is used for denoising waveforms. A polarization–linearity filter is initially applied to preserve the signal intervals and suppress the noise amplitudes. This is followed by time–frequency thresholding for further signal‐to‐noise ratio enhancement in the S transform domain. The parameterisation for both polarization filter and time–frequency thresholding is also discussed. Finally, real microseismic data examples are shown to demonstrate the improvements in processing results when denoised waveforms are considered in the workflow. The results indicate that current denoising approach effectively suppresses the background noise and preserves the vector fidelity of signal waveform. Consequently, the quality of event detection, arrival‐time picking, and hypocenter location improves. 相似文献
17.
This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and empirical relationships, describing the influence of meteorological conditions, topography, sediment characteristics and vegetation. A so-called adaptation length is incorporated to calculate the development of transport equilibrium along the profile. Changes in topography are derived from the predicted transport, using the continuity equation. Vegetation height is incorporated in the model as a dynamic variable. Vegetation can be buried during transport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-order closure air flow model, which predicts friction velocities over the profile, influenced by topography and surface roughness. Modelling results are shown for (a) the growth and migration of bare, initially sine-shaped dunes, and (b) dune building on a partly vegetated and initially flat surface. Results show that the bare symmetrical dunes change into asymmetric shapes with a slipface on the lee side. This result could only be achieved in combination with the secondorder closure model for the calculation of air flow. The simulations with the partly vegetated surfaces reveal that the resulting dune morphology strongly depends on the value of the adaptation length parameter and on the vegetation height. The latter result implies that the dynamical interaction between aeolian activity and vegetation (reaction to burial, growth rates) is highly relevant in dune geomorphology and deserves much attention in future studies. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
18.
孙一男 《地震地磁观测与研究》2022,43(2):219-224
人工地震数据的存储管理及共享技术发展迅速,但是存储管理方式、资源利用率及服务水平等还有很大的提升空间。针对以上问题初步建立人工地震数据平台,利用Web和数据库技术,整合并存储已有人工地震数据资源,以便向公众及地震科研人员提供最新工作进展和研究成果。该平台的建立,利于科学研究工作的交流合作和观测资料的充分利用,从而为我国防震减灾事业做更大贡献。 相似文献
19.
按照压剪应力场中袭纹具有的特点,简化成三种力学模型——狭长缺口、顺序闭合裂纹及初始闭合裂纹。利用文中建议的局部分析法,对其端部应力场做的一般分析,导出了他们的普遍表达式。用光弹性实验及有限元计算对所得结果做的分析表明,它们是成立的。这些结果有助于了解构造地震震源的破裂机制及其应力场分布的某些特点。 相似文献
20.
An understanding of the frictional sliding on faults that can lead to earthquakes requires a knowledge of both constitutive behavior of the sliding surfaces and its mechanical interaction with the loading system. We have determined the constitutive parameters for frictional sliding of initially bare surfaces of Westerly granite, using a recently developed high pressure rotary shear apparatus that allows long distances of sliding and therefore a greater assurance of attaining steady state behavior. From experiments conducted at room temperature and normal stresses of 27–84 MPa several important results have been found. (1) A gouge layer 100 to 200 m thick was developed from the initially bare rock surfaces after 18 to 70 mm of sliding. (2) The steady state frictional resistance, attained after about 10 mm of sliding, is proportional to the negative of the logarithm of the sliding velocity. (3) Abrup changes in the velocity of sliding result in initial changes in the frictional resistance, which have the same sign as the velocity change, and are followed by a gradual decay to a new steady state value over a characteristic distance of sliding. This velocity weakening behavior is essentially identical with that found by several previous workers on the same material at lower normal stress. (4) Our results are well described by a two state variable constitutive law. The values of the constitutive parameters are quite similar to those found previously at low normal stress, but the characteristic distance is about an order of magnitude smaller than that found at 10 MPa normal stress with thicker layers of coarser gouge. (5) We have approximated our results with a one state variable constitutive law and compared the results with the predictions of existing nonlinear stability analysis; in addition, we have extended the stability analysis to systems possessing two state variables. With such formulations good agreement is found between the experimentally observed and theoretically predicted transitions between stable and unstable sliding. These results allow a better understanding of the instabilities that lead to earthquakes. 相似文献