Lyapunov-type stability criterion for periodic generalized Camassa–Holm equations

We study the Lyapunov stability of the periodic generalized Camassa–Holm equation in terms of the periodic/anti-periodic eigenvalues and the associated spectral intervals. Moreover, we establish a Lyapunov-type stability criterion based on the Floquet theory and a Lyapunov-type inequality.     

Blow‐up criterion for 3D viscous‐resistive compressible magnetohydrodynamic equations

In this paper, we establish a blow‐up criterion of strong solutions for 3D viscous‐resistive compressible magnetohydrodynamic equations, which depends only on and . Our result improves the previous criterion in Lu's paper (Journal of Mathematical Analysis and Applications 2011; 379: 425–438.) for compressible magnetohydrodynamic equations by removing a stringent condition on the viscous coefficients μ > 4λ. In addition, initial vacuum states are also allowed in our cases. Copyright © 2012 John Wiley & Sons, Ltd.     

临界空穴扩张比准则的适用性

用新研制成的DE36平台钢制的轴对称和平面应变试样,进一步考察了临界空穴扩张比V_(Gi)准则[1]、[2]、[3]的适用性。实验和大应变有限元理论计算结果表明,V_(Gi)准则适用于所研究材料。文中指出,按V_(Gi)准则可根据试样或构件材料中V_G的发展变化来预起裂位置。     

对薄层柱壳爆炸膨胀断裂过程的研究

 本文提出了一个用于描述动态破坏发展过程的损伤度函数。从这个损伤度函数出发,把材料特征性方程取为强化粘塑性本构方程形式,导出了薄层柱壳爆炸膨胀运动在两种近似下（恒定膨胀速度近似合恒定应变速率近似）断裂判据的解析表达式。结果分析表明,在上述条件下,存在着一个动态断裂“塑性峰”,在这个峰值条件的应变率下,柱壳出现贯穿断裂时刻的应变最大。以软钢为算例,本断裂判据可以比较好地解释Иванов和陈大年等给出的实验结果。这时,动态断裂“塑性峰”对应的应变率为4×10⁴ s^-1,相应的应变约为60%~80%。     

光学低通滤波器的光学传递函数分析

光电成像系统的抽样过程会引起图像频谱在频谱空间上的多次复制,如果抽样过程不满足系统的奈奎斯特条件,相邻的频谱项就会产生混叠.光学传递函数可以反映系统中光学成像,抽样和重建等各个过程对图像信号频谱的响应.通过对使用光学低通滤波器(OLPF)光电成像系统的光学传递函数的分析,表明光学低通滤波器可以有效地限制图像的频谱宽度,使抽样满足奈奎斯特条件,达到消除频谱混叠,改善重建图像质量的目的.     

海上浮式风力机支撑结构的流固耦合动力学研究

海上漂浮式风力机支撑结构动力载荷的确定不仅对于结构设计、施工过程非常重要,对于设施的运维保障同样重要。水动力载荷的计算可归为基于势流理论的理论模型和基于计算流体动力学的数值模型两类方法。本文简述了两类模型各自的基本原理,明确其优劣,为实际工程应用的合理建模提供参考。对于海洋工程,水池物理模型实验发挥着重要作用。本文以某结构型式的浮式支撑结构的物理模型实验为例,阐述了物理模型实验技术的局限性及改进措施,为工程建设提供必要的技术支撑。

     

属性识别预警系统(AFS)——一种新的信用评价方法

在属性集和属性测度函数的基础上建立了属性测度预警系统.利用我国深、沪两交易所2000年公布的106家上市公司作为训练样本,计算出“差”企业和“好”企业的属性测度均值,构造出属性测度函数.进而对2001年公布的13家预亏公司进行预警分析,用置信度准则及最大属性测度准则判别,预警准确率分别达到92.31%和100%.因此,属性识别预警系统在信用评价方面具有良好的应用前景.     

Optimality criterion for a class of nonlinear integer programs

Graver's optimality conditions based on Hilbert bases apply to an integer program with linear equations and a linear objective function. We generalize this result to include a fairly large class of nonlinear objective functions. Our extension provides in particular a link between the superadditivity of the difference-objective function and the Hilbert bases of conic subpartitions of .     

全纯函数族涉及公共值的正规定则

研究涉及公共值的全纯函数正规族问题．设F为单位圆△内的全纯函数族,a,b为两个判别的有穷复数且b≠0．文中证明了若对每一个,f∈F,Ef(a)=Ef(a),E↑-f′（b)包含于E^-f(b),则F在单位圆△内正规．     

Dispersion Characteristics of Arbitrary Periodic Structures with Rectangular Grooves

The dispersion characteristics of a circular cylindrical waveguide with periodic surface corrugations consisting of rectangular grooves with smoothing are examined using the Space Harmonic Method (SHM). The whole structure is divided into two regions, one describing the propagation volume and one inside the grooves. In the first region, the Floquet theorem is applicable and the field distribution is expressed as a summation of spatial Bloch components, whereas in the second one an appropriate Fourier expansion of standing waves is used. Applying the boundary conditions an infinite system of equations is obtained, which is solved numerically by truncation. Several cases are considered, including the limiting cases of a sinusoidal and a rectangular corrugation profile, to check the accuracy of the method proposed as well as its dependence on the corrugation profile. Numerical results are presented only for transverse magnetic modes, although the formalism can be easily extended to include all kinds of waves that can in principle propagate in such a structure.