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71.
Janusz R. Prajs Keith Whittington 《Transactions of the American Mathematical Society》2007,359(12):5991-6000
Applications of the work introduced by the authors in a recent article, Filament sets and homogeneous continua, are given to aposyndesis and local connectedness. The aposyndetic decomposition theorem of Jones is generalized to spaces with the property of Kelley.
72.
This is the first of two papers presenting a systematic development of a continuum model of a porous medium and of transport
processes occurring in it. The concept of a Representative Elementary Volume (REV) as opposed to any arbitrary volume of averaging
quantities at the micro-scale, is quantified. A universal criterion for selecting the size of an REV as a function of measurable
characteristics of a porous medium and selected tolerance levels of estimation errors, is developed. The rules of spatial
averaging are extended by including the effects of both the configuration of the solid matrix and of interphase transfer phenomena
within an REV. 相似文献
73.
In this work we consider a poroelastic, flexible material that may deform largely, which is situated in an incompressible fluid driven by the Navier–Stokes equations in two or three space dimensions. By a variational approach we show existence of weak solutions for a class of such coupled systems. We consider the unsteady case, this means that the PDE for the poroelastic solid involves the Fréchet-derivative of a non-convex functional as well as (second order in time) inertia terms. 相似文献
74.
Poro-micromechanics allows for the quantification of poroelastic properties such as the Biot and Skempton coefficients, once a continuum micromechanics model for the material under consideration has been developed and validated. Employing such a model for the transversely isotropic elasticity of cortical and trabecular bone, we determine the tensors of Biot and Skempton coefficients as functions of the volume fractions of mineral, collagen, and the micropore space (Haversian and Volkmann canals, and the inter-trabecular space). Increase of microporosity, as experienced in osteoporosis, as well as decrease of mineral content, as experienced in osteomalacia, lead to an increase of Biot and Skempton coefficients, i. e. to magnification of the mechanical role of the marrow filling the micropore space. For quantification of the marrow pressure rise upon downfall, undrained conditions are appropriate, as can be shown by model predictions of non-destructive impact experiments. 相似文献
75.
在这篇文章里,R.G Muncaster的零维弹性体被推广到一般的高阶零维物质体。从非极连续介质力学理论出发,我们推出了零维物质体的所有平衡方程和热力学不等式。再从这些方程和不等式推出微态物质体的相应平衡方程和热力学不等式。这样,我们在零维物质体理论和微态物质体理论之间建立了一个类似于刚性质点力学和古典非极连续介质力学之间关系的关系。 相似文献
76.
考虑双层碳纳米管的层间范德华力,采用连续介质力学的波动理论,建立了双层碳纳米管中周向导波传播模型,研究周向导波的频散现象.通过与单层碳纳米管结果的比较表明,双层碳纳米管中周向导波的传播表现出更为明显的频散特性,出现更多的模态干涉现象,并发现在某些特殊频率处出现成对模态的消失与新启现象. 相似文献
77.
I. W. Stewart 《Continuum Mechanics and Thermodynamics》2007,18(6):343-360
A dynamic continuum theory is presented for smectic A liquid crystals in which the usual director n and unit layer normal
a do not always necessarily coincide. Most previous dynamic continuum theories equate n with a; the theory developed in this
article allows n and a to differ in non-equilibrium situations, work that has been motivated by the recent investigations
by Auernhammer et al. (Rheol. Acta 39, 215–222, 2000; Phys. Rev. E 66, 061707, 2002) and Soddemann et al. (Eur. Phys. J. E
13, 141–151, 2004). The usual Oseen constraint () for smectics is not imposed upon the unit normal a. Permeation is also included. After a summary of the complete dynamic
equations, an application is given via an example which shows that planar aligned layers of smectic A subjected to an arbitrary
periodic disturbance are linearly stable.
相似文献
78.
Simulation of crack spacing using a reinforced concrete model with an internal length parameter 总被引:3,自引:0,他引:3
Summary A gradient-enhanced smeared crack model and bond-slip interface elements are utilized in finite element simulations of reinforced
concrete. The crack model is rooted in an enhanced plasticity theory. It uses the Rankine failure surface dependent on an
equivalent inelastic strain measure as well as on its Laplacian. As a result, finitely sized fracture process zones and realistic
crack spacings are obtained. A reinforced concrete bar in uniaxial tension is analyzed to demonstrate the regularizing influence
of the internal length parameter in the model and to evaluate the influence of the model parameters on the energy dissipation
in multiple cracks. A comparison of numerical simulations with experimental results for a beam without shear reinforcement
in four-point bending concludes the analysis.
Received 4 November 1997; accepted for publication 23 April 1998 相似文献
79.
Accuracy assessment of the linear Poisson–Boltzmann equation and reparametrization of the OBC generalized Born model for nucleic acids and nucleic acid–protein complexes 下载免费PDF全文
Federico Fogolari Alessandra Corazza Gennaro Esposito 《Journal of computational chemistry》2015,36(9):585-596
The generalized Born model in the Onufriev, Bashford, and Case (Onufriev et al., Proteins: Struct Funct Genet 2004, 55, 383) implementation has emerged as one of the best compromises between accuracy and speed of computation. For simulations of nucleic acids, however, a number of issues should be addressed: (1) the generalized Born model is based on a linear model and the linearization of the reference Poisson–Boltmann equation may be questioned for highly charged systems as nucleic acids; (2) although much attention has been given to potentials, solvation forces could be much less sensitive to linearization than the potentials; and (3) the accuracy of the Onufriev–Bashford–Case (OBC) model for nucleic acids depends on fine tuning of parameters. Here, we show that the linearization of the Poisson Boltzmann equation has mild effects on computed forces, and that with optimal choice of the OBC model parameters, solvation forces, essential for molecular dynamics simulations, agree well with those computed using the reference Poisson–Boltzmann model. © 2015 Wiley Periodicals, Inc. 相似文献
80.