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401.
Martin Cadwallader 《The Professional geographer》1987,39(3):317-326
The LISREL model analyzes complex interrelationships involving latent variables, effectively integrating the widely used factor analysis and regression procedures. A residential mobility example, calibrated for Portland, OR, suggests that turnover rates are both directly and indirectly influenced by latent variables representing housing type, housing quality, family status, and socioeconomic status. 相似文献
402.
A.?GuadagniniEmail author L.?Guadagnini D. M.?Tartakovsky C. L.?Winter 《Stochastic Environmental Research and Risk Assessment (SERRA)》2003,17(6):394-407
We study two-dimensional flow in a layered heterogeneous medium composed of two materials whose hydraulic properties and spatial distribution are known statistically but are otherwise uncertain. Our analysis relies on the composite media theory, which employs random domain decomposition in the context of groundwater flow moment equations to explicitly account for the separate effects of material and geometric uncertainty on ensemble moments of head and flux. Flow parallel and perpendicular to the layering in a two-material composite layered medium is considered. The hydraulic conductivity of each material is log-normally distributed with a much higher mean in one material than in the other. The hydraulic conductivities of points within different materials are uncorrelated. The location of the internal boundary between the two contrasting materials is random and normally distributed with given mean and variance. We solve the equations for (ensemble) moments of hydraulic head and flux and analyze the impact of unknown geometry of materials on statistical moments of head and flux. We compare the composite media approach to approximations that replace statistically inhomogeneous conductivity fields with pseudo-homogeneous random fields.
This work was performed under the auspices of the US Department of Energy (DOE): DOE/BES (Bureau of Energy Sciences) Program in the Applied Mathematical Sciences contract KC-07–01–01 and Los Alamos National Laboratory under LDRD 98604. This work made use of STC shared experimental facilities supported by the National Science Foundation under Agreement No. EAR-9876800. This work was supported in part by the European Commission under Contract No. EVK1-CT-1999–00041 (W-SAHaRA). 相似文献
403.
Volume-changing clay soils constitute the most costly natural hazard to buildings on shallow foundations. With the existing expansive clays in Ankara, low-rise buildings at the southwest part of the city have shown damage resulting in considerable maintenance costs. This paper reports the findings of an experimental investigation emphasizing the swelling behavior of Ankara Clay and correlations between the swelling parameters and other soil properties, and present a synthesis of observed damage details. The poor performance of the affected light-weight structures is assessed in the light of environmental conditions. In addition, swelling maps for SW and central parts of the Ankara metropolitan area, based on measured and predicted swelling parameters, are constructed for the purposes of land-use planning and general assessment of environmental problems. The experimental results suggest that the clay has high-to-very high activity, depth of active zone generally ranges between 1–2 m, the use of remolded and desiccated specimens seems to be a better approach in swelling tests, and the empirical equations based on two or more index or physical properties are good predictors for the estimation of the swelling potential of the clay. High swelling pressures exerted by the soil, flat topography and poor drainage, climatic conditions and poor construction methods are the main reasons of the structural damage observed at the study site. 相似文献
404.
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406.
油气勘探的重点是寻找油气储层的分布 ,而地下油气的存在必然对地震记录产生影响。传统的地震波理论是建立在纯弹性固体基础之上 ,没有考虑固体中所含的流体 ,因此 ,它难以研究含油水岩石的物理性质 ,如岩石的渗透率和孔隙度、油水粘度。从固、液介质系统能量和本构方程出发 ,推导出固体、油相和水相的动力学方程 ,进而建立起含油水两相流体各向异性孔隙介质的地震波传播方程。该方程包括有岩石和油水的物理参数 ,更适合于油田的勘探和开发。 相似文献
407.
Plasticity model for sand under small and large cyclic strains: a multiaxial formulation 总被引:1,自引:0,他引:1
Achilleas G. Papadimitriou George D. Bouckovalas 《Soil Dynamics and Earthquake Engineering》2002,22(3):15
This paper presents the multiaxial formulation of a plasticity model for sand under cyclic shearing. The model adopts a kinematic hardening circular cone as the yield surface and three non-circular conical surfaces corresponding to the deviatoric stress ratios at phase transformation, peak strength and critical state. The shape of the non-circular surfaces is formulated in accordance with the experimentally established failure criteria, while their size is related to the value of the state parameter ψ. To simulate cyclic response under small and large shear strain amplitudes without a change in model parameters, it was found necessary to introduce: (a) a non-linear hysteretic (Ramberg–Osgood type) formulation for the strain rate of elastic states and (b) an empirical index of the effect of fabric evolution during shearing which scales the plastic modulus. This index is estimated in terms of a macroscopic second-order fabric tensor, which develops as a function of the plastic volumetric strain increment and the loading direction in the deviatoric plane. Comparison of simulations to pertinent data from 27 resonant column, cyclic triaxial and cyclic direct simple shear tests provide a measure for the overall accuracy of the model. 相似文献
408.
Lidunka Vo?adlo John BrodholtDavid P Dobson K.S Knight W.G MarshallG.David Price Ian G Wood 《Earth and Planetary Science Letters》2002,203(1):567-575
First-principles calculations have been used to determine the equation of state of Fe3C in both its low-pressure magnetically ordered and high-pressure non-magnetically ordered states; at 0 K the ferromagnetic transition was found to occur at about 60 GPa. In the high pressure, non-magnetically ordered regime at 0 K the material may be described by a Birch-Murnaghan third-order equation of state with V0=8.968(7) Å3 per atom, K0=316.62(2) GPa and K′=4.30(2). At atmospheric pressure the ferromagnetic phase transition in Fe3C occurs at ∼483 K; preliminary measurements of the thermal expansion by powder neutron diffraction show that this transition produces a large effect on thermoelastic properties. The volumetric thermal expansion coefficient in the paramagnetic phase was found to be 4.34×10−5 K−1 at T∼550 K. By applying a thermal expansion correction to the calculated equation of state at 0 K, predicted values for the density and adiabatic incompressibility of this material at core pressures and temperatures were obtained. These results appear to be sufficiently different from seismological data so as to preclude Fe3C as the major inner core-forming phase. 相似文献
409.
Sang-Heon Shim Thomas S. DuffyKenichi Takemura 《Earth and Planetary Science Letters》2002,203(2):729-739
The pressure-volume-temperature equation of state (EOS) of gold is fundamental to high-pressure science because of its widespread use as an internal pressure standard. In particular, the EOS of gold has been used in recent in situ multi-anvil press studies for determination of phase boundaries related to the 660-km seismic discontinuity. These studies show that the boundaries are lower by 2 GPa than expected from the depth of the 660-km discontinuity. Here we report a new P-V-T EOS of gold based on the inversion of quasi-hydrostatic compression and shock wave data using the Mie-Grüneisen relation and the Birch-Murnaghan-Debye equation. The previously poorly constrained pressure derivative of isothermal bulk modulus and the volume dependence of Grüneisen parameter (q=d lnγ/d ln V) are determined by including both phonon and electron effects implicitly: K′0T=5.0±0.2 and q=1.0±0.1. This combined with other accurately measured parameters enables us to calculate pressure at a given volume and temperature. At 660-km depth conditions, this new EOS yields 1.0±0.2 GPa higher pressure than Anderson et al.’s EOS which has been used in the multi-anvil experiments. However, after the correction, there still exists a 1.5-GPa discrepancy between the post-spinel boundary measured by multi-anvil studies and the 660-km discontinuity. Other potential error sources, such as thermocouple emf dependence on pressure or systematic errors in spectroradiometry, should be investigated. Theoretical and experimental studies to better understand electronic and anharmonic effects in gold at high P-T are also needed. 相似文献
410.