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301.
We have carried out first-principles molecular dynamics simulations of glass and liquid germanium dioxide (GeO2) over a wide range of pressure. Our results show that in the glass GeO2 system nearly all Ge–O coordination environments are fourfold at low compression, whereas at high compression five- and sixfold coordination types coexist. In the liquid GeO2 system although most Ge–O coordination environments are fourfold, some threefold coordination types exist at low compression. Pentahedral units also exist in the liquid state while less than that in the glass state. At high compression, pentahedral units disappear and GeO6 octahedron is dominant in the liquid state going with some sevenfold coordination. 相似文献
302.
By introducing two pairs of conjugate exponents and estimating the weight coefficients, we give generalizations of some Hilbert's type inequalities with the best constant factor. As applications, some particular results are considered. 相似文献
303.
参数设计是日本质量专家田口倡导的一种质量工程方法,调节因子的存在性在参数设计中非常重要.在附加了分布假定的条件下,本文对傅珏生等的定理给出了证明,也指出了从函数结构上研究参数设计的重要性. 相似文献
304.
305.
By using the finite-part integral concepts and limit technique, the hypersingular integrodifferential equations of three-dimensional
(3D) planar interface crack were obtained; then the dominant-part analysis of 2D hypersingular integral was further used to
investigate the stress fields near the crack front theoretically, and the accurate formulae were obtained for the singular
stress fields and the complex stress intensity factors. After that, a numerical method is proposed to solve the hypersingular
integrodifferential equations of 3D planar interface crack, and the problem of elliptical planar crack is then considered
to show the application of the method. The numerical results obtained are satisfactory.
Project supported by the Foundation of Solid Mechanics Open Research Laboratory of State Education Commission at Tongji University
and the National Natural Science Foundation. 相似文献
306.
O. D. Makinde 《国际流体数值方法杂志》2009,59(7):791-799
In this paper, the temporal development of small disturbances in a pressure‐driven fluid flow through a channel filled with a saturated porous medium is investigated. The Brinkman flow model is employed in order to obtain the basic flow velocity distribution. Under normal mode assumption, the linearized governing equations for disturbances yield a fourth‐order eigenvalue problem, which reduces to the well‐known Orr–Sommerfeld equation in some limiting cases solved numerically by a spectral collocation technique with expansions in Chebyshev polynomials. The critical Reynolds number Rec, the critical wave number αc, and the critical wave speed cc are obtained for a wide range of the porous medium shape factor parameter S. It is found that a decrease in porous medium permeability has a stabilizing effect on the fluid flow. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
307.
《Journal of Nonlinear Mathematical Physics》2013,20(2):247-254
We characterize the Liouvillian and analytic first integrals for the polynomial differential systems of the form x′ = a - (b + 1)x + x2y, y′ = bx - x2y, with a, b ∈ ?, called the Brusselator differential systems. 相似文献
308.
In this article, we present some new perturbation bounds for the (subunitary) unitary polar factors of the (generalized) polar decompositions. Two numerical examples are given to show the rationality and superiority of our results, respectively. In terms of the one-to-one correspondence between the weighted case and the non-weighted case, all these bounds can be applied to the weighted polar decomposition. 相似文献
309.
Current models for pressure drop prediction of slug flow pneumatic conveying in a horizontal pipeline system assume some type of steady state conditions for prediction,which limits their capability for increased predictive accuracy relative to experimental data.This is partly because of the nature of slug flow pneumatic conveying system,which,as a dynamic system,never becomes stable.By utilising conservation of mass (airflow),a dynamic pressure analysis model is proposed on the basis of the derivative of the upstream pressure behaviour.The rate of air permeation through slug,one of the important factors in the conservation model,is expressed as a function of a slug permeability factor.Other factors such as slug velocity,slug length and the fraction of stationary layer were also considered.Several test materials were conveyed in single-slug tests to verify the proposed pressure drop model,showing good agreement between the model and experimental results. 相似文献
310.
Rik G.P. Frehen Roy P.M.M. Hoevenaars Franz C. Palm Peter C. Schotman 《Insurance: Mathematics and Economics》2008,42(3):1050-1061
The high value of the implicit option to choose a retirement date at which interest rates are particularly high and life annuities relatively cheap, leads to the possibility to introduce regret aversion in the retirement investment decision of defined contribution plan participants. As a remedy for regret aversion in retirement investment decisions, this paper develops and prices a lookback option on a life annuity contract. We determine a closed-form option value under the restriction that the option holder invests risklessly during the time to maturity of the option and without the guarantee that the exact amount of retirement wealth is converted into a life annuity at retirement. Thereafter the investment restriction is relaxed and the guarantee of exact conversion is imposed and the option is priced via Monte Carlo simulations in an economic environment with a stochastic discount factor. Option price sensitivities are determined via the pricing of alternative options. We find that the price of a lookback option, with a maturity of three years, amounts to 8%–9% of the wealth at the option issuance date. The option price is highly sensitive to the exercise price of the option, i.e. pricing alternative options (e.g. Asian) substantially lowers the price. Time to maturity and interest rate volatility are other important option price drivers. Asset allocation decisions and initial interest rates hardly affect the option price. 相似文献