In-plane wave motion in finite element model

The analysis method of lattice dynamics in classical physics is extended to study the properties of in-plane wave motion in the hybrid-mass finite element model in this paper. The dispersion equations of P and SV waves in the discrete model are first obtained by means of separating the characteristic equation of the motion equation, and then used to analyse the properties of P-and SV-homogeneous, inhomogeneous waves and other types of motion in the model. The dispersion characters, cut-off frequencies of P and SV waves, the polarization drift and appendent anisotropic property of wave motion caused by the discretization are finally discussed. The project sponsored by the Earthquake Science Foundation under Contract No. 90141     

Prediction of the overall moduli of a cylindrical short-fiber reinforced composite

With respect to obtaining the effective elastic moduli of the composite, the present theory differs from both Eshelby's equivalent inclusion method and Hill's self-consistent one, both of which only consider the mechanical properties of the matrix and inclusions (fibers). In fact, the inclusion-inclusion interaction is more pronounced when the volume fraction of inclusions of the composite increases. Hence, in this paper the effective elastic moduli of the composite are derived by taking into account the shapes, sizes and distribution of inclusions, and the interactions between inclusions. In addition, it is more convincing to assume short-fibers as cylindrical inclusions as in the present paper than as ellipsoidal ones as in others^[7,8]. Finally, numerical results are given.     

一个Thoms型定理

Thomas［1］ established a genralization of the OrliczPettis theorem as follows: Let Ω be a compact Hausdorff space and X a normed space. If a series ∑fj in C(Ω,X) is subseries convergent in the topology of pointwise convergence on Ω, then ∑fj is also subseries convergent in the topology of uniform convergence on Ω. Note that ∑fj is subseries convergent in the topology of pointwise (resp., uniform) convergence on Ω means that for every (tj)∈{0,1}N, there is an f∈C(Ω,X) such that …     

A CONTINUATION HOMOTOPY METHOD FOR THE INVERSE PROBLEM OF OPERATOR IDENTIFICATION AND ITS APPLICATION

A new widly convergent method for solving the problem of operator kientification is illustrated.Numerical simulations are carried out to test the feasibllity and to study the general characteristics of the technique without the real measurement data.This technique is a direct application of the continuation homotopy method for solving nonlinear systems of equations.It is found that this method does give excellent results in solving the inverse problem of the elliptic differential equations.     

碳纤维/树脂基复合材料曲壁蜂窝夹芯结构的三点弯曲性能北大核心CSCD

为研究碳纤维复合材料(CFRP)曲壁蜂窝结构在三点弯曲载荷作用下的承载特性与失效模式,对不同芯层高度、面板厚度的结构进行了理论预报、数值模拟及试验.首先,根据夹芯结构的主要失效模式,提出了相应的理论预报公式,并绘制了失效机制图;其次,建立了CFRP曲壁蜂窝夹芯结构的有限元仿真模型,对其在三点弯曲载荷作用下的典型失效行为进行模拟;最后,通过模压成型工艺制备了不同尺寸的CFRP曲壁蜂窝夹芯结构,并将试验结果与理论、模拟结果进行比较.结果表明,蜂窝夹芯结构承载能力与芯层高度、面板厚度密切相关,结构芯层及面板刚度随其尺寸的减小而下降,导致结构失效模式由面芯脱黏失效变为面板压溃失效.     

含负折射率介质的一维光子晶体构成的相干热辐射源的辐射特性及控制

电子清刷是微通道板生产流程中常用的除气方法,会引起微通道板其他性能参量的变化.为研究电子清刷对微通道板输出信噪比及增益的影响,根据信噪比及增益的定义讨论了微通道板性能参量的测试方法,研制了微通道板参量测试系统.应用微通道板参量测试系统对微通道板进行了电子清刷处理,测试清刷过程中不同阶段微通道板的信噪比及增益变化.实验表明:微通道板增益随清刷时间增加而降低,同时增益稳定性提高;电子清刷过程中微通道板的输出信号及噪音的变化率与微通道板增益的变化率基本相同,输出信噪比基本不变.增益变化是影响清刷过程中信号及噪音变化的主要因素,并且电子清刷对微通道板输出信噪比影响较小.     

A Remark on the Unconditionally Convergent Series

For every unconditionally convergent series $\sum_{j=1}^{\infty}x_{j}$ in sequentially complete Abelian topological group, we show that the sum $\sum_{j=1}^{\infty}x_{\theta(j)}$ is same for all permutations θ:?→?. This result justify the measures defined on quantum structures.     

Almost Orthogonality and Hausdorff Interval Topologies of de Morgan Lattices and Lattice Effect Algebras

The topologies on ordered structures have been intensively studied by mathematicians and computer scientists. Various types of topologies may be introduced, depending on the nature of the ordered sets considered. Our purpose here is to study the interval topology τ _i , the order topology τ _o and the topology τ _Φ induced by a canonical intrinsic uniformity generated by a certain family of pseudometrics on de Morgan lattices. This uniformity and topology may be regarded as a “two-sided symmetrization” of a similar intrinsic uniformity introduced by Erné and Palko for an order-theoretical construction of certain uniform completions. We prove that on a de Morgan lattice L with a join-dense set $\mathcal{U}$ the interval topology τ _i is Hausdorff and L is compactly generated by the elements of $\mathcal{U}$ if and only if L is $\mathcal{U}$ -almost orthogonal if and only if any element of $\mathcal{U}$ is hypercompact.     

Semiparametric bounds of mean and variance for exotic options

Finding semiparametric bounds for option prices is a widely studied pricing technique. We obtain closed-form semiparametric bounds of the mean and variance for the pay-off of two exotic (Collar and Gap) call options given mean and variance information on the underlying asset price. Mathematically, we extended domination technique by quadratic functions to bound mean and variances. This work was supported by National Science Foundation of the United States (Grant Nos. DMS-0720977 and DMS-0805929)     

一些单叶函数族的卷积性质

一些单叶函数族的卷积性质凌怡，丁树森，杨晓非（哈尔滨工业大学数学系１５０００６）１９９０年６月２９日收到．一、介绍设在卜内解析且，记其全体为人用Ｓ表示Ａ中的单叶子类．对０≤ａ＜１，０≤β＜１，令Ｓ（ａ）＝，这些都是熟知的单叶函数族．其中Ｓ＊（ａ），Ｋ...