二阶中立型微分方程的区间振动准则

利用平均函数技巧 ,对二阶中立型微分方程 [a(t) (x(t) p(t)x(t-τ) )′]′ q(t)f[x(t) ,x(t-σ) ]g[x′(t) ]=0建立了一些区间振动准则 ,这些振动准则不同于已知依赖于整个区间 [t0 ,∞ )的性质的结果 ,而是仅依赖于 [t0 ,∞ )上的子区间列的性质     

A novel far-boundary condition for the finite element analysis of infinite reservoir

The present paper deals with the finite element analysis of the reservoir of infinite extent using a novel far-boundary condition. The equations of motion are expressed in terms of the pressure only assuming water as inviscid and incompressible. The truncation boundary condition is developed numerically from the classical wave equation. Comparative studies show that the proposed far-boundary condition is numerically efficient and accurate over the existing ones, available in the literature. The effect of the geometry of the reservoir bed and the adjacent structure on the development hydrodynamic pressure has been studied. The results show that the geometry of the reservoir bed and as well as the adjacent structure has considerable effect on the development of hydrodynamic pressure at the dam–reservoir interface.     

Hopping of chaotic dynamics in a doubly resonant parametric oscillator

We study a doubly resonant optical parametric oscillator where the pump can feed two pairs of signal-idler modes. We assume the presence of gain at the pump frequency. We investigate the various oscillation states of interest, namely, when only the first pair oscillates with the other pair having null amplitudes and vice versa. We demonstrate the exchange of dynamics between the mode pairs when the relevant parameters of the cavity, namely, the phase mismatch factors or the decay rates switch because of fluctuations. The exchange of dynamics is shown to be independent of the nature of dynamics, i.e. independent of whether the motion isn-periodic or chaotic. We also investigate the case where both the pairs can exhibit chaotic dynamics though these states are difficult to realize because of fluctuations.     

高阶拟线性中立型偏泛函微分方程组解的振动性

1 引言 由于在人口动力学、生物遗传工程和化学反应过程等自然的和人为的过程中都存在滞后现象,因而偏泛函微分方程(组)的研究能更精确地揭示事物本质,同时能丰富微分方程(组)理论的研究。近十几年来,很多学者在泛函偏微分方程解的振动理论的研究方面作了大量工作,取得了许多成果。然而,关于泛函偏微分方程组解的振动性的研     

储存环内电子冷却过程模拟

考虑储存环内离子的横向振荡和纵向振荡的运动特性,模拟了HIRFL-CSR内重离子束的电子冷却过程.给出了离子束的横向发射度和纵向动量散度随时间连续变化的图象,由此分析了电子束的空间电荷效应,冷却段色散函数和横向电子束温度对冷却过程快慢的影响.     

高速水射流与凝聚炸药相互作用的数值模拟

 利用LS-DYNA3D软件并采用Lagrange算法，对500 m/s的高速水射流与凝聚炸药的相互作用过程进行了数值模拟；对不同时刻凝聚炸药中的压力分布以及不同径向、轴向处的压力历史进行了分析；确定了所选凝聚炸药的声速。数值模拟的结果与理论分析的结果之间具有很好的一致性。模拟结果表明，在高速水射流与凝聚炸药相互作用的过程中，凝聚炸药药柱截面上的压力随径向距离的增加而降低；药柱中的最大压力出现在水射流头部附近或水射流头部的前方。     

Oscillation of second order neutral delay differential equations of Emden-Fowler type

We present new oscillation criteria for the second order nonlinear neutral delay differential equation [y(t)-py(t-τ)]'+ q(t)y ^λ (g(t)) sgn y(g(t)) = 0, t ≧ t ₀. Our results solve an open problem posed by James S.W . Wong [24]. The relevance of our results becomes clear due to a carefully selected example. This revised version was published online in June 2006 with corrections to the Cover Date.     

High-pressure clathrate hydrate of acetone

X-ray diffraction study of quenched sample of acetone clathrate hydrate synthesized at 0.8 GPa was carried out. It was shown that the host frameworks of the hydrate comprise uniform cavities which are similar to that of recently characterized structure of high-pressure tetrahydrofurane hydrate. The unique peculiarity of investigated hydrate is decrease in the crystallographic symmetry of the hydrate arising from ordering in guest subsystem.     

Model for phase coexistence in phase transitions

We propose a general model for describing the phenomena of phase coexistence in relation to pressure induced phase transformations by means of the T–P distribution in statistical thermodynamics. Using the well‐known B1–B2 transition in NaCl as a prototype, we demonstrate how phase coexistence gives rise to the changes in the bulk modulus and the equation‐of‐state across the transition. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004