An efficient method for nonlinear analysis of layered shells

Finite element formulation based on explicit through-thickness integration scheme assumes importance when applied to multilayered shells, as it is numerically accurate and computationally efficient. Explicit integration becomes possible on assuming the variation of the inverse Jacobian through the thickness. The element stiffness matrices are discussed for (i) large rotation, and (ii) small rotation. Relative efficiencies of the explicit through-thickness integration schemes are compared with that of the conventional formulation involving numerical integration in three directions in each layer and summation over the layers. The small rotation formulation assuming linear variation of the Jacobian inverse across the thickness and based on further approximation regarding certain submatrices is seen to be computationally efficient. The geometric nonlinear behaviours of laminated composite cylindrical panels subjected to external pressure are discussed. The parameters considered are: number of layers, symmetric/antisymmetric, cross-ply/angleply, boundary conditions and central angle. The strength of shallow panels with longitudinal edges hinged and curved edges free is controlled by the limit point load, while for deep panels it is controlled by the bifurcation load. The boundary conditions have significant influence on load carrying capacities. A list of symbols is given at the end of the paper     

Microstructure devices for efficient heat transfer

Microstructure devices provide unique properties with regard to heat and mass transfer. Due to the tremendously high surface-to-volume ratio they are very well suited for many thermal and chemical processes in which large amount of heat has to be transferred. Metal microstructure devices also provide very high stability against high pressure, combined with an adjustable mass flow range of up to several thousand kg of liquid per hour and per passage, depending on the size and number of the integrated microstructures. Aside of fluid driven metallic microstructure devices like the famous Karlsruhe Cube, electrically powered devices have been developed and applied for temperature ranges where thermoliquids reach their limits or the use of gases may be disadvantageous due to their high viscosity and the arising pressure drop. In this publication several microstructure devices for heating and evaporation of fluids as well as for chemical reactions are presented in overview style. Details on manufacturing and device properties are given. Some process examples and experimental data for different types of microstructure devices are shown. Fouling problems are discussed briefly by an example.     

An efficient interior-point algorithm with new non-monotone line search filter method for nonlinear constrained programming

An efficient primal-dual interior-point algorithm using a new non-monotone line search filter method is presented for nonlinear constrained programming, which is widely applied in engineering optimization. The new non-monotone line search technique is introduced to lead to relaxed step acceptance conditions and improved convergence performance. It can also avoid the choice of the upper bound on the memory, which brings obvious disadvantages to traditional techniques. Under mild assumptions, the global convergence of the new non-monotone line search filter method is analysed, and fast local convergence is ensured by second order corrections. The proposed algorithm is applied to the classical alkylation process optimization problem and the results illustrate its effectiveness. Some comprehensive comparisons to existing methods are also presented.     

Extremum principles for some nonlinear heat transfer problems

Summary Recent results on extremum principles for various nonlinear boundary value problems are applied to heat transfer problems involving space radiators such as fins and other parts of spacecraft. The results are illustrated by obtaining quite accurate variational solutions for such problems involving the fourth-power law of radiation.     

基于电路压缩的单开路故障快速分析算法

基于多网格和等效电路这两种电路压缩方法,提出了一种电源线/地线(P/G)网络单故障高效分析算法,以有效地提高P/G网单开路电阻故障的测试效率.该算法包括3个算法步骤:先采用多网格方法和等效电路方法对电路进行大幅度地压缩,此过程具有快速与高精度的优点,再采用连续过松弛(SOR)求解算法求解剩余电路的电压分布,最后根据已知电压节点快速而精确地返算出被压缩节点的电压.实验数据表明:该算法具有精度高、算法复杂性低、应用范围广等优点.与通用的不完全乔勒斯基分解共轭梯度(ICCG)求解算法相比,该算法在保持较高精度(误差小于0.0276%)的前提下,速度可以提高106倍,同时还可以求解ICCG算法无法处理的测例.     

An efficient marching algorithm for waterhammer analysis by the method of characteristics

Summary A new fast and efficient marching algorithm is introduced to solve the basic quasilinear, hyperbolic partial differential equations describing unsteady, flow in conduits by the method of characteristics. The details of the marching method are presented with an illustration of the waterhammer problem in a simple piping system both for friction and frictionless cases. It is shown that for the same accuracy the new marching method requires fewer computational steps, less computer memory and time.     

Wave heat transfer in anisotropic space with nonlinear characteristics

An analytical solution to the problem of heat transfer in anisotropic space, the thermal-conductivity tensor components of which depend on temperature, has been obtained for the first time. Heat transfer is initiated by a pulsed point thermal-energy source. It is found that the heat transfer is of the wave type with a finite propagation rate of the thermal-wave front, although the heat conduction equation is of a parabolic type. Cases of different power-law temperature dependences of the thermal-conductivity tensor components have been investigated. It has been shown that the thermal-wave fronts have the shape of ellipsoids (in space) or ellipses (in plane). The results can be used to analyze the heat exchange in composites under laser irradiation.     

An efficient algorithm for granular dynamics simulations with complex-shaped objects

One of the most difficult aspect of the realistic modeling of granular materials is how to capture the real shape of the particles. Here we present a method to simulate two-dimensional granular materials with complex-shaped particles. The particle shape is represented by the classical concept of a Minkowski sum, which permits the representation of complex shapes without the need to define the object as a composite of spherical or convex particles. A well defined interaction force between these bodies is derived. The algorithm for identification of neighbor particles reduces force calculations to O(N), where N is the number of particles. The method is much more efficient, accurate and easier to implement than other models. We prove that the algorithm is consistent with energy conservation, which is numerically verified using non-dissipative granular dynamics simulations. Biaxial test simulations on dissipative granular systems demonstrate the relevance of shape in the strength and stress fluctuations at the critical state.     

An efficient algorithm for propagating fluid-driven fractures

This paper presents an efficient finite element algorithm for propagating fluid-driven fractures in pressure sensitive geomaterials. Fluid flow in the fracture is modelled by lubrication theory. Rock deformation is assumed to be elastoplastic and dilatent. A cohesive model based on the softening behaviour of rocks is employed as the propagation criterion. A special continuation method based on the volume of injected fluid in the fracture is used for direct coupling of the fluid-flow with rock deformation and for driving the solution during propagation. Sample results are provided for the problem of hydraulic fracturing to demonstrate the efficiency of the proposed algorithm. Received 5 February 1999     

An adaptive algorithm for nonlinear system identification

There are several methods — fixed, adaptive, recursive — for the identification of linear and bilinear systems from input-output measurements that are noisy. However, literature is rather scarce as far as such techniques are concerned for the identification of nonlinear systems. The objective of this paper, therefore, is to suggest an iterative technique for the identification of nonlinear system parameters from measurements that are noisy. This technique requires the transformation of a nonlinear system in the state variable form into an input-output autoregressive moving average exogenous (armax) model. The pseudo linear regression algorithm, which has been extensively used for the identification of linear systems, can then be used to identify the nonlinear system parameters. Using this technique simulation studies were carried out which, indeed, confirm the efficacy of the method.     

Nonsteady heat transfer in semi-infinite region with nonlinear heat-absorption law

The method of determining the temperature gradient at the boundary of a semi-infinite region proposed earlier for linear problems [1–3] is outlined as it applies to a nonlinear problem.Notation D fractional-differentiation symbol - T temperature - q temperature gradient - k parameter characterizing heat-transfer rate-, x, t, coordinate and time - , , coefficients of general heat-conduction equation - constant Indices s surface Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 1, pp. 143–147, July, 1980.     

A fully nonlinear analysis of heat and mass transfer problems in porous bodies

The finite element method is used to analyse heat and mass transfer problems in porous media, in which the thermophysical properties are allowed to vary as functions of temperature and moisture. An example is given of the application of the method to the problem of timber drying.     

Signal-to-noise-ratio analysis for nonlinear N-ary phase filters

The problem of recognizing targets in nonoverlapping clutter using nonlinear N-ary phase filters is addressed. Using mathematical analysis, expressions were derived for an N-ary phase filter and the intensity variance of an optical correlator output. The N-ary phase filter was shown to consist of an infinite sum of harmonic terms whose periodicity was determined by N. For the intensity variance, it was found that under certain conditions the variance was minimized due to a previously undiscovered phase quadrature effect. Comparison showed that optimal real filters produced greater signal-to-noise-ratio values than the continuous phase versions as a consequence of this effect.     

An efficient algorithm for minimum degeneracy primer selection

Selecting degenerate primers for multiplex polymerase chain reaction (MP-PCR) experiments, called the degenerate primer design problem (DPDP), is an important problem in computational molecular biology and has drawn the attention of numerous researchers in the recent past. Several variants of DPDP were formulated by Linhart and Shamir and proven to be NP-complete. A number of algorithms have been proposed for one such variant, namely, the maximum coverage degenerate primer design problem (MC-DPDP). In this paper, we consider another important variant called the minimum degeneracy degenerate primer design with errors problem (MD-DPDEP), propose an algorithm to design a degenerate primer of minimum degeneracy for a given set of DNA sequences and show experimental results of its performance on random and real biological datasets. Our algorithm combines methodologies in motif discovery and an iterative technique to design the primer     

On nonlinear problems of heat and mass transfer

A system of nonlinear equations for steady one-dimensional heat and mass transfer problems is considered. Analytical solutions are obtained for certain special cases.     

An efficient GRASP algorithm for disassembly sequence planning

One of the steps in a reverse supply chain is to disassemble the recovered products. The design of such disassembly operations is more complex than that of classical assembly lines. A new GRASP algorithm is presented in this paper for solving Disassembly Sequence Planning, i.e. the determination of the sequence for disassembling component parts. The problem has a combinatorial structure and a large number of constraints. Moreover, checking the feasibility of each solution element is time consuming. The proposed approach is successfully tested against previous best known solutions for a set of public benchmark problems.     

板换换热与压降关联式遗传算法参数辨识

针对板换的换热及压降关联式适用范围窄的缺点，在分析板换传热和压力损失原理的基础上，建立板式换热器分布参数模型，借鉴已有的换热和压降关联式，并以关联式中的系数为优化辨识变量，以换热器特性参数模拟值与试验值相对偏差为优化目标函数，采用遗传算法进行优化计算，获得待辨识参数的值，得到新的换热和压降关联式，通过与已有的较高精度关联式和试验数据的比较，证明所获得的关联式具有较高的精度，通过遗传算法参数辨识获得板换换热及压降关联式是一种行之有效的关联式获取方法。