三向应力Mohr圆的真实构成及剪应力作用方向的确定

三向应力Mohr圆的构成在传统上是借助公式推证而得，并以平面图形来表示，缺乏三维的真实感和直观性。在应力应变分析中，对于平面应力问题，可以通过平面应力摩尔圆确定过一点不同斜面上的应力分量及其作用方向。对于三维问题，利用摩尔圆图解法可以确定某一斜面上的正应力和剪应力的数值，但不能表示剪应力的作用方向。剪应力的作用方向需要通过另外的图解方法来确定。本文分别从坐标系旋转和数值计算的角度解释了三向应力Mohr圆的构成过程，形象地说明了Mohr圆的物理本质。针对三向应力Mohr圆不能表示剪应力作用方向的问题，通过矢量运算，给出了剪应力作用方向的确定公式。     

Dynamics of a quantized circle homeomorphism with quasiperiodic perturbation

We introduce the notion of a quantized circle homeomorphism that is a discontinuous mapping of an interval shift, which is widely used in modern digital radio electronics. For a two-dimensional dynamical system given by a triangular mapping, which is a quantized circle homeomorphism with quasiperiodic perturbation, we prove, under some assumptions, that there exist an invariant absorbing belt and a repulsive contour, study properties of these structures, and get estimates for their sizes. To make the exposition complete, we, first, study the corresponding problems for three less complicated systems, namely, a proper circle homeomorphism, a proper circle homeomorphism with quasiperiodic perturbation, and a quantized circle homeomorphism without perturbation.     

Numerical solutions for the transient flow in the homogenous closed circle reservoirs

There are many fault block fields in China. A fault block field consists of fault pools. The small fault pools can be viewed as the closed circle reservoirs in some case. In order to know the pressure change of the developed formation and provide the formation data for developing the fault block fields reasonably, the transient flow should be researched. In this paper, we use the automatic mesh generation technology and the finite element method to solve the transient flow problem for the well located in the closed circle reservoir, especially for the well located in an arbitrary position in the closed circle reservoir. The pressure diffusion process is visualized and the well-location factor concept is first proposed in this paper. The typical curves of pressure vs time for the well with different well-location factors are presented. By comparing numerical results with the analytical solutions of the well located in the center of the closed circle reservoir, the numerical method is verified.     

Numerical method for obtaining the scattering matrix of a microwave two-port from standing wave measurements

A numerical procedure is presented for obtaining the scattering matrix of a passive reciprocal two-port from eight standing wave measurements with the aid of an image circle in the Smith chart. The optimum circle through more than three points is defined. Furthermore, an averaging method is applied using the fact that theoretically after a certain transformation the experimental points should be distributed regularly on the circle. The procedure is programmed for a computer.     

小子样试验条件下的序贯概率圆精度检验方法

小子样试验条件下的精度评定问题是远程飞行器靶场试验的关键问题之一,属于未知参数的假设检验问题。通过分析装备飞行试验双方风险管控和试验成本,提出了基于序贯的命中精度概率圆鉴定方法。通过落点概率密度分布函数推导出概率圆计算公式,设计了假设条件下的概率圆计算流程和仿真算例,总结出概率圆半径、试验子样和双方风险的关系,讨论了检出比λ的使用原则,基于保证使用方风险不变的原则提出传统概率圆检验方法的修正策略。利用仿真试验结果证实了基于序贯的概率圆方法能够保证检验精度,并且提高了试验效益。飞行试验结果证实了该方法的可行性。     

鞍马全旋运动的动力学

本文从经典力学观点讨论人体在鞍马上的全旋运动,理想化的全旋运动要求人体以不变的章动角作匀速进动,同时绕纵轴朝相反方向自旋,以保证在运动过程中始终面向前方。文中规定一种带特殊完整约束条件的刚体规则进动作为这种运动的理想模式,并利用人体的多刚体模型分析鞍马上的直体全旋及托马斯全旋的运动规律,导出肩关节支撑力及肌肉控制力矩的计算公式。     

The illustration calculations of second order effects in elastic half-space acted upon by a non-uniform shear load

I.IllustrationsThegeneralsolutionofsecondordereffectsinelastichalfspaceacteduponbyanon-uniformshearloadpresentedbypaperIl]areapplicableforallvalueof6>-l,butareverycomplicated.Asani1lustrationofthemethodwegivebelowthelinearandsecondordersolutionsfor8=l/2.T…     

Designing Hopf limit circle to dynamical systems via modified projective synchronization

In order to affirmatively utilize the characteristics of Hopf limit circle, a control method to design Hopf circle with proper characteristics into dynamical system is established based on the modified projective synchronization (MPS). The proposed method may serve as a complete solution to design a stable Hopf limit circle, which can simultaneously achieve the following three properties: with the desired amplitudes and shape changes, with the pre-specified location center, and at a pre-specified system parameter location. In contrast to the methods based on Hopf bifurcation theory, the new method is independent of the verbose procedures for the bifurcation critical conditions and the stability analysis. Numerical examples demonstrate the effectiveness of the proposed method.     

六分圆爆炸逻辑网络研究

本工作以随机定向战斗部为应用背景，研究了六分圆爆炸逻辑网络及其爆炸逻辑元件，以及相关的接口匹配技术。给出了爆炸二极管、同步型爆炸与门和异步型爆炸与门的设计原理和相关参数的安全性／可靠性概率窗，分析了六分圆爆炸逻辑网络设计中的元件选择、与战斗部的配合、与引信的配合等技术问题。试验检验表明，六分圆爆炸逻辑网络的输出状态完全达到预期的要求。     

SH波与界面多圆孔的散射及动应力集中

研究了平面SH波对相邻多个界面圆孔的散射及其动应力集中,为了求解,首先利用复变函数和多极坐标方法构造了在含有多个半圆形缺口的弹性半空间,水平面上任一点随时间谐和出平面线源载荷作用时失主移,邓Green函数,且采用“契合”模型,推导了SH波对相邻多个界面圆孔散射的定解积分方程组,进而求得圆孔附近的动应力系数,作为算例,讨论了具有两个界面圆孔对SH波的散射及其相互影响,给出了孔附近的动应力分布曲线。     

Scattering by an anisotropic circle

The scattering by a circle is considered when the outside medium is isotropic and the inside medium is anisotropic (orthotropic). The problem is a scalar one and is phrased as a scattering problem for elastic waves with polarization out of the plane of the circle (SH wave), but the solution is with minor modifications valid also for scattering of electromagnetic waves. The equation inside the circle is first transformed to polar coordinates and it then explicitly contains the azimuthal angle through trigonometric functions. Making an expansion in a trigonometric series in the azimuthal coordinate then gives a coupled system of ordinary differential equations in the radial coordinate that is solved by power series expansions. With the solution inside the circle complete the scattering problem is solved essentially as in the classical case. Some numerical examples are given showing the influence of anisotropy, and it is noted that the effects of anisotropy are generally strong except at low frequencies where the dominating scattering only depends on the mean stiffness and not on the degree of anisotropy.     

Analytic study of 2D and 3D grid motion using modified Laplacian

The modified Laplacian has been used to move unstructured grids in response to changes in the surface grid for a variety of grid movement applications including store separation, aero‐elastic wing deformation and free surface flow simulations. However, the use of the modified Laplacian can result in elements with negative areas/volumes, because it has no inherent mechanism to prevent inversion of elements. In this paper, the use of a modified Laplacian is studied analytically for a two‐dimensional problem of deforming the inner circle of two concentric circles and for a three‐dimensional problem of deforming the inner sphere of two concentric spheres. By analysing the exact solution for this problem, the amount of translation and deformation of the inner circle that maintains a valid mesh is determined. A general grid movement theorem is presented which determines analytically the maximum allowable deformation before an invalid mesh results. Under certain circumstances, the inner circle and sphere can be expanded until it reaches the outer circle or sphere, while remaining a valid grid, and the inner circle and sphere can be rotated by an extreme amount before failure of the mesh occurs. By choosing the exponent to the modified Laplacian appropriately, extreme deformations for single frequency deformations is possible, although for practical applications where the grid movement has multiple frequencies, choosing the optimal exponent for the modified Laplacian may not be practical or provide much improvement. For grid movement simulations involving rigid body translation and rotation or uniform expansion, the modified Laplacian can yield excellent results, and the optimum choice of the modified Laplacian can be analytically determined for these types of motions, but when there are multiple frequencies in the deformation, the modified Laplacian does not allow much deformation before an invalid grid results. Copyright © 2006 John Wiley & Sons, Ltd.     

Image encryption algorithm with circle index table scrambling and partition diffusion

This paper introduces an image encryption algorithm shorted as CITSPD, manipulated by circle index table scrambling and partition diffusion. Firstly, the circle index table is obtained through the generation, circle shift and transposition of the benchmark sequence. Secondly, the plain image is transformed into the wavelet coefficient and is then scrambled by the circle index table. Thirdly, the permutated image is disturbed by different noises and is further divided into four subsections. Finally, the forward and inverse partition diffusions are performed to the subsections for getting the cipher image. The main feature of this algorithm is that the robust chaos-based keystream and encryption process are highly sensitive to the plaintext, which will effectively resist against chosen-plaintext and known-plaintext attacks. In addition, the encryption scheme is free of noise attack since the inverse diffusion differs from the forward one. And the diffusion effect can be effectively enhanced by, as much as possible, increasing the small pixel value and decreasing the large pixel value. Experimental tests and security analyses are carried out to verify the advantages of the scheme.

     

热带气旋的基本热力学分析

通过对热带气旋的热力学分析与计算, 发现热带气旋的能量主要来源于水蒸气凝结所释放的潜热. 气旋内外的温度差异使其产生了做功能力, 形成了一个热力循环, 该热力循环的效率在一定高度范围内随温度的增高有一个最大值: 对于一定的气旋底部温度,在饱和空气温度较低时, 其效率随着高度的增加存在极大值; 而当温度较高时, 则其效率随着高度一直增加. 当海面环境温度在33oC~34oC时, 效率达到最大值, 约为7.4%. 而输出功则随着温度的增加而一直增加, 因而气旋强度随着环境温度的增高而增大.      

A boundary-field equation method for a nonlinear exterior elasticity problem in the plane

This paper presents a new method for solving a nonlinear exterior boundary value problem arising in two-dimensional elasto-plasticity. The procedure is based on the introduction of a sufficiently large circle that divides the exterior domain into a bounded region and an unbounded one. This allows us to consider the Dirichlet-Neumann mapping on the circle, which provides an explicit formula for the stress in terms of the displacement by using an appropriate infinite Fourier series. In this way we can reduce the original problem to an equivalent nonlinear boundary value problem on the bounded domain with a natural boundary condition on the circle. Hence, the resulting weak formulation includes boundary and field terms, which yields the so called boundary-field equation method. Next, we employ the finite Fourier series to obtain a sequence of approximating nonlinear problems from which the actual Galerkin schemes are derived. Finally, we apply some tools from monotone operators to prove existence, uniqueness and approximation results, including Cea type error estimates for the corresponding discrete solutions.     

椭圆孔口外受集中力和力偶时的新解法

文中给出了无限平板带椭圆孔又受集中力和力偶时的弹性分析。所讨论问题归结为复变函数的一个特殊问题，即令一个复变函数（单位圆外有奇点）的值和另一个复变函数（单位圆外为解析）的共轭值沿着单位圆相等。最后，得出了闭合形式的解。     

矩形区域不等圆形随机堆放的数值模拟

将若干待堆放的圆形堆放到一个给定矩形区域,是一类特殊的Packing问题。针对这一具有NP难度的困难问题,提出一种快速的数值模拟方法以及模拟力学检验的方法。该方法将圆形堆放的力学平衡规律化为几何形体相互接触的几何条件,把大量的圆形按级配及分布律等约束条件,随机堆放形成空间区域。按此方法得到的圆形堆体,在不加外力的情形下即可保持自身的稳定。使用该方法,在边长为15cm的正方形区域内,取圆形的直径范围为0.5cm~4cm,模拟了孔隙率小于25%(面积比)的圆形堆体。最后,将所模拟的圆形堆体试件进行了有限元网格划分及力学加载试算,结果表明该堆体是稳定的。为进一步在细观层次研究圆形堆体提供了一个快速的数值模拟方法。     

The Conley Index Over the Circle

We study the Conley index over a base in the case when the base is the circle. Such an index arises in a natural way when the considered flow admits a Poincaré section. In that case the fiberwise pointed spaces over the circle generated by index pairs are semibundles, i.e., admit a special structure similar to locally trivial bundles. We define a homotopy invariant of semibundles, the monodromy class. We use the monodromy class to prove that the Conley index of the Poincaré map may be expressed in terms of the Conley index over the circle.     

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等截面直梁受纯弯曲作用,其挠曲线精确解为圆弧线,然而用图乘法和重积分法求得的却都 是抛物线. 分析了用图乘法和重积分法求解纯弯曲梁的挠曲线均是抛物线而不是圆弧线的原 因,给出了用抛物线代替圆弧线的误差.