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71.
A theory of strain-gradient plasticity for isotropic, plastically irrotational materials. Part I: Small deformations 总被引:1,自引:0,他引:1
This study develops a small-deformation theory of strain-gradient plasticity for isotropic materials in the absence of plastic rotation. The theory is based on a system of microstresses consistent with a microforce balance; a mechanical version of the second law that includes, via microstresses, work performed during viscoplastic flow; a constitutive theory that allows:
- •
- the microstresses to depend on , the gradient of the plastic strain-rate, and
- •
- the free energy ψ to depend on the Burgers tensor .
72.
Morton E. Gurtin 《Journal of the mechanics and physics of solids》2004,52(11):2545-2568
This study develops a gradient theory of small-deformation viscoplasticity based on: a system of microforces consistent with its peculiar balance; a mechanical version of the second law that includes, via the microforces, work performed during viscoplastic flow; a constitutive theory that accounts for the Burgers vector through a free energy dependent on , with Hp the plastic part of the elastic-plastic decomposition of the displacement gradient. The microforce balance and the constitutive equations, restricted by the second law, are shown to be together equivalent to a nonlocal flow rule in the form of a coupled pair of second-order partial differential equations. The first of these is an equation for the plastic strain-rate in which the stress T plays a basic role; the second, which is independent of T, is an equation for the plastic spin. A consequence of this second equation is that the plastic spin vanishes identically when the free energy is independent of, but not generally otherwise. A formal discussion based on experience with other gradient theories suggests that sufficiently far from boundaries solutions should not differ appreciably from classical solutions, but close to microscopically hard boundaries, boundary layers characterized by a large Burgers vector and large plastic spin should form.Because of the nonlocal nature of the flow rule, the classical macroscopic boundary conditions need be supplemented by nonstandard boundary conditions associated with viscoplastic flow. As an aid to solution, a variational formulation of the flow rule is derived.Finally, we sketch a generalization of the theory that allows for isotropic hardening resulting from dissipative constitutive dependences on . 相似文献
73.
In this paper we present a new framework for identifying preferred solutions to multi-objective binary optimisation problems.
We develop the necessary theory which leads to new formulations that integrate the decision space with the space of criterion
weights. The advantage of this is that it allows for incorporating preferences directly within a unique binary optimisation
problem which identifies efficient solutions and associated weights simultaneously. We discuss how preferences can be incorporated
within the formulations and also describe how to accommodate the selection of weights when the identification of a unique
solution is required. Our results can be used for designing interactive procedures for the solution of multi-objective binary
optimisation problems. We describe one such procedure for the multi-objective multi-dimensional binary knapsack formulation
of the portfolio selection problem. 相似文献
74.
Patrick Morton 《The Ramanujan Journal》2011,25(2):247-275
The arithmetic on elliptic curves in Deuring normal form is shown to be related to solutions of the Fermat equation 27X 3+27Y 3=X 3 Y 3. This arithmetic is used to give conditions for the existence of multipliers μ on supersingular elliptic curves in characteristic p for which μ 2=?3p. Together with an explicit factorization of a certain class equation, these conditions imply that the number of irreducible binomial quadratic factors (mod p) of the Legendre polynomial P (p?e)/3(x) of degree (p?e)/3 is a simple linear function of the class number of the quadratic field \(\mathbb{Q}(\sqrt{-3p})\). 相似文献
75.
The Ramanujan Journal - In this paper, transformation formulas for the function $$\begin{aligned} A_{1}\left( z,s:\chi \right) =\sum \limits _{n=1}^{\infty }\sum \limits _{m=1} ^{\infty }\chi... 相似文献
76.
77.
78.
D.J. Hinde A.C. Berriman R.D. Butt M. Dasgupta C.R. Morton A. Mukherjee J.O. Newton 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):149-154
In the fusion of heavy nuclei, there is a distribution of fusion barrier energies resulting from coupling between intrinsic
motion and internal degrees of freedom. Precise experimental measurements of excitation functions have allowed the extraction
of the distributions by taking the second derivative using a point-difference method. In the case of statically deformed nuclei,
experimental data shows that the different fusion barrier energies correspond to different physical configurations of the
colliding nuclei, the latter affecting the subsequent dynamical trajectories over the potential energy surface, influencing
the ultimate reaction products, as for example in quasi-fission. The fusion barrier distribution is also valuable in understanding
the fusion of weakly bound nuclei, enabling a reliable prediction of the expected fusion cross-sections, and thus the determination
of fusion suppression factors at above-barrier energies.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
79.
Determining whether a solution is of high quality (optimal or near optimal) is fundamental in optimization theory and algorithms.
In this paper, we develop Monte Carlo sampling-based procedures for assessing solution quality in stochastic programs. Quality
is defined via the optimality gap and our procedures' output is a confidence interval on this gap. We review a multiple-replications
procedure that requires solution of, say, 30 optimization problems and then, we present a result that justifies a computationally
simplified single-replication procedure that only requires solving one optimization problem. Even though the single replication
procedure is computationally significantly less demanding, the resulting confidence interval might have low coverage probability
for small sample sizes for some problems. We provide variants of this procedure that require two replications instead of one
and that perform better empirically. We present computational results for a newsvendor problem and for two-stage stochastic
linear programs from the literature. We also discuss when the procedures perform well and when they fail, and we propose using
ɛ-optimal solutions to strengthen the performance of our procedures. 相似文献
80.
Archive for Rational Mechanics and Analysis - 相似文献