圆柱壳稳定性分析的一种新方法

针对圆柱壳在复杂栽荷作用下静力稳定性问题提出了一种新的求解方法．基于分离变量的方法，设定一组可涵盖任意边界条件的复数位移函数，将位移函数代入系统平衡方程后，圆柱壳的静力稳定性问题就可以转化为一个复系数八次多项式的求根问题．该特征方程的偶次幂系数项以及常数项为实数，而奇数次幂项均为纯虚数．研究表明，根的大小代表了圆柱壳端部作用力的强度，以及该作用力在离开这个边界一定距离上的衰减特性．分析了该新方法和经典方法的关系，并给出了一个各向同性圆柱壳在轴向压力作用下稳定性分析算例，得到了线弹性失稳解．和经典方法的结果比较表明，文中所提出的新方法适用可行，且和经典方法具有同样的精度．     

A predictive analysis for optimum contour-after-wear for magnetic heads

Reliable reproduction of recorded signals is dependent upon a good head-tape interface, and particularly, upon adequate contact pressure at the gap. In the case of grooved magnetic heads the pressure profiles are complex 3-dimensional surfaces. The head contours, as machined, may cause pressure profiles which are unfavorable to good signal reproduction. A mathematical analysis is outlined, which forecasts the progressively changing head contours and pressure profiles in terms of the average depth of head wear due to passage of tape (magnetic or lapping tape). The analysis indicates the amount of wear needed to substantially improve the pressure profile. Good correlation is shown between the theoretical predictions and actual test values.     

A compensating method of skew determination in cylindrical thin magnetic films

A new compensating method for skew measurement in toristor-type cylindrical magnetic films is described. The state of the magnetization vector is scanned with a bipolar magnetic-field pulse and a compensating dc field is applied. Both the magnitude and direction of the skew are obtained.     

A renewable liquid droplet method for on-line pollution analysis by multi-photon ionization

A multi-photon ionization based fast conductance (MPI-FC) technique was applied to detect combustion byproduct aerosols. These PAH-polluted aerosols were on-line sampled by means of renewable water microdroplets. The environmental cases considered here have involved such common air contaminants as motor car exhaust gas and cigarette smoke. The possibility of obtaining useful calibration curves has been addressed. Two droplet contamination regimes were clearly observed. These have been argued to be associated with either a volume uniform (i.e., a bulk type) or a surface-favored contamination. The latter regime is possible whenever the increasing droplet contamination extends beyond the solubility saturation of the PAH compounds. Detection limits as low as 1 pg were obtained for pyrene-contaminated renewable microdroplets.     

A new method of on-line multiparameter amplitude analysis with compression

An algorithm of on-line multidimensional amplitude analysis with compression using fast adaptive orthogonal transform is presented in the paper. The method is based on a direct modification of multiplication coefficients of the signal flow graph of the fast Cooley-Tukey's algorithm. The coefficients are modified according to a reference vector representing the processed data. The method has been tested to compress three parameter experimental nuclear data. The efficiency of the derived adaptive transform is compared with classical orthogonal transforms.     

A boundary element method for two dimensional linear elastic fracture analysis

A boundary element method is developed for the analysis of fractures in two-dimensional solids. The solids are assumed to be linearly elastic and isotropic, and both bounded and unbounded domains are treated. The development of the boundary integral equations exploits (as usual) Somigliana's identity, but a special manipulation is carried out to regularize certain integrals associated with the crack line. The resulting integral equations consist of the conventional ordinary boundary terms and two additional terms which can be identified as a distribution of concentrated forces and a distribution of dislocations along each crack line. The strategy for establishing the integral equations is first outlined in terms of real variables, after which complex variable techniques are adopted for the detailed development. In the numerical implementation of the formulation, the ordinary boundary integrals are treated with standard boundary element techniques, while a novel numerical procedure is developed to treat the crack line integrals. The resulting numerical procedure is used to solve several sample problems for both embedded and surface-breaking cracks, and it is shown that the technique is both accurate and efficient. The utility of the method for simulating curvilinear crack propagation is also demonstrated.     

A magnetic circuit analysis of the iron-cored homopolar linear synchronous motor

An analysis of the iron-cored homopolar linear synchronous motor (LSM) is presented using tooth-by-tooth magnetic circuit theory and field dependent relative permeabilities. Sophisticated iterative procedures are used to obtain numerical solutions to the resulting set of simultaneous nonlinear equations. The analysis is validated by comparison between calculated and reported experimental tests results.     

A novel method for sensing rotational speed, linear displacement and current using superconducting BPSCCO magnetic sensor

For many decades, magnetic sensors have been of great assistance to mankind in variety of functions that include simple compass based navigational systems to devices that monitor the invisible biological activities. In industries magnetic sensors are in great demand for control and measurement of linear and rotary position sensing etc, because of its non destructive and contact less way of detection. Consequently, newer, smarter and cheaper materials are continuously being explored to suit the varied needs of technological requirements. In the present communication, the characteristics of a magnetic sensor, based on the non linear electromagnetic response of the weak links present in the polycrystalline BPSCCO superconductor are reported. The second harmonic response of sintered superconducting BPSCCO pellet in an alternating magnetic field at 40 kHz and 77 K being a strong linear function of low d.c. magnetic field has been utilized for the development of highly sensitive magnetic field sensors. The noise limited resolution of the sensor is found to be 3.16 ×10^-9 T/√Hz for H_a.c = 16 Oe and frequency 40 kHz. We further demonstrate that such HTSC based magnetic sensors are capable of sensing the rotational speed, small displacement and direct current with good resolution. The experimental methods and results obtained are discussed.     

一种被动双阵航迹关联新方法

在被动系统中,多传感器多目标数据关联一直是一个难解决的问题.对静态数据关联多维指派"组合爆炸"问题,许多外学者提出了像最小距离法、最大似然算法等多种解决方法,但它们或正确相关率较低,或计算量较大.基于上述问题,提出了一种基于运动目标在时间上具有连续性的先验知识的新的航迹关联算法,该算法根据数据列之间发展态势的相似或相异程度来衡量航迹间接近的程度,使航迹关联问题突破了样本容量和典型分布这两条限制.仿真结果表明该算法计算量小,正确关联率高,具有较高的工程应用价值.     

A method for linear elasto-static analysis of multi-layered axisymmetrical bodies using Hankel's transform

 A method to determine the distribution of stresses and displacements in an infinite, linear, elastic, multi-layered medium subjected to static axisymmetric loading is presented in this work. By using axisymmetric governing equations, Hankel's transform and matrix analysis, the methodology gives a clearly arranged way to calculate the stresses and displacements in the medium. A numerical method for Hankel's transform is employed to perform the calculation. Two representative examples are studied. The results can be utilized as a fundamental solution for boundary element methods for the linear, elasto-static, axisymmetric multi-layered problem with a little modification.     

A mesh-free method for analysis of the thermal and mechanical buckling of functionally graded cylindrical shell panels

The buckling response of functionally graded ceramic-metal cylindrical shell panels under axial compression and thermal load is presented here. The formulation is based on the first-order shear deformation shell theory and element-free kp-Ritz method. The material properties of shell panels are assumed to vary through their thickness direction according to a power-law distribution of the volume fraction of constituents. Approximations of the displacement field are expressed in terms of a set of mesh-free kernel particle functions. A stabilized conforming nodal integration approach is employed to estimate the bending stiffness, and the shear and membrane terms are evaluated using a direct nodal integration technique to eliminate membrane and shear locking for very thin shells. The mechanical and thermal buckling responses of functionally graded shell panels are investigated, and the influences of the volume fraction exponent, boundary conditions, and temperature distribution on their buckling strengths are also examined.     

Field analysis of the magnetic systems for tubular linear reluctance motors

We report a study of tubular linear reluctance motors (TLRMs) in various types of magnetic circuits. We carried out magnetic field analyses and calculated integral parameters of the field. We also determined static characteristics and electromagnetic parameters of the motor. We found good agreement between our calculations and tests of the motor with sinusoidal excitation.     

A hybrid method of analysis of low-speed linear induction motors

A current-excited low-speed solid-iron secondary single-sided linear induction motor (SLIM) with aluminum reaction rail is considered, A hybrid method of analysis consisting of field analysis in conjunction with the multilayer transfer-matrix concept with adjustment of secondary iron permeability to match the tangential magnetizing field in each layer is developed. It is shown that this method gives valuable information on permeability and flux penetration in secondary iron. Computed thrusts are in good agreement with test results.     

A method for the random analysis of linear systems subjected to non-stationary multi-correlated loads

The paper shows a procedure for evaluating the correlation matrix and the evolutionary power spectral density matrix of the response of linear structural systems subjected to random non-stationary multi-correlated vector processes. The approach reduces this problem to the solution of some corresponding stationary problems. It is shown that the assumption of a modulating matrix function, whose elements are the sum of exponential functions, allows to transform the initial non-stationary problem into a stationary one. This stationary problem can be solved by well-known unconditionally stable step-by-step numerical procedures in the time domain, and, in closed form, in the frequency domain. The comparison of the results obtained using the proposed approach with those obtained by Monte Carlo Simulations (MCS) has revealed a very good level of accuracy.     

A multilayer recognition method for understanding table-form documents

The items in documents are composed under the mutual relationship between geometrical layout structure and logical structure. Thus, currently used documents may be categorized roughly on the basis of the geometrical layout structure and logical structure. Table-form documents are strictly defined by the geometrical layout structure in comparison with the other documents. Since the item fields are, in general, surrounded with vertical and horizontal line segments, with a view to understanding table-form documents it is better to recognize these line segments first and then identify individual item fields on the basis of the recognition results. At least, in table-form documents the vertical and horizontal line segments take important roles in recognizing the layout structures. In this article, we address a multilayer recognition method for understanding table-form documents. Our recognition layers are composed hierarchically of four different recognition processes: document class recognition, layout recognition, item recognition, and character recognition. In addition, our recognition method is organized on the basis of the interaction paradigm that the lower-layer recognition process verifies objects interpreted in the upper-layer recognition process with its own knowledge and then decomposes the objects into more elementary and meaningful objects. Moreover, we discuss a knowledge representation method from the viewpoints of physical and logical representations, and syntactic and semantic information. We also show the knowledge that is useful in understanding table-form documents with respect to such a representation method. © 1996 John Wiley & Sons, Inc.     

The finite element method vs the edge function method for linear fracture analysis

An investigation was performed to compare the Finite Element Method and the Edge Function Method for the solution of two dimensional linear elastic fracture problems. The comparison was made to determine whether one of the procedures had a distinct advantage over the other for fracture analysis. Although each method has minor advantages for the computation of specific quantities or the analysis of specific types of problems, there is no major advantage for either procedure which is immediately apparent. Because of the considerable investment which many organizations have already expended on developing a Finite Element capability, and the additional investment which would be required to implement the Edge Function Method the application of the Edge Function Method will probably be very limited.     

一种新型机车动轮弛缓在线监测及报警方案

本文介绍了一种新型机车制动热抱弛缓在线监测方案。该方案以轮箍温度及轮箍和轮辋的相对位移为对象，在线监控机车运行状态，提示司机机车的意外情况，确保机车行车安全。