Showing papers by "Xi'an Jiaotong University published in 1990"
TL;DR: An algorithm for global minimization is generated based on the concept and properties of the filled function and computational results show that in most cases this algorithm works better than the tunneling algorithm.
Abstract: The concept of a filled function is introduced. We construct a particular filled function and analyze its properties. An algorithm for global minimization is generated based on the concept and properties of the filled function. Some typical examples with 1 to 10 variables are tested and computational results show that in most cases this algorithm works better than the tunneling algorithm. The advantages and disadvantages are analyzed and further research directions are discussed.
298 citations
TL;DR: In this article, a double-inlet pulse tube refrigerator is proposed, which has a second inlet at the hot end of the pulse tube connected to the pressure wave generator.
255 citations
TL;DR: In this article, some sufficient conditions on persistence or extinction of a population have been obtained, and the threshold between the two has also been obtained for most situations in most situations. But all those papers have a basic assumption that the capacity of the environment is so large that the change of toxicants in the environment that comes from uptake and egestion by the organisms can be neglected.
Abstract: Models of the persistence and extinction of a population or community in a polluted environment have been investigated in several papers. But all of those papers have a basic assumption that the capacity of the environment is so large that the change of toxicants in the environment that comes from uptake and egestion by the organisms can be neglected. This assumption is not made in this article. Some sufficient conditions on persistence or extinction of a population have been obtained, and the threshold between the two has also been obtained for most situations.
95 citations
TL;DR: In this article, a new filled function, the globally convexized filled function (GFFL), is proposed, where the value tends to positive infinity as the norm of the variable vector tends to infinity, and it has no stationary point in the region in which the objective function value is greater than or equal to the least value found so far, but it does have a minimizer with a prefixed minimizer.
95 citations
TL;DR: In this paper, the low cycle fatigue (LCF) damage evolution of weld Heat Affected Zone (HAZ) is studied by use of Continuum Damage Mechanics, based on a continuum damage variable, D, on the effective stress concept and on thermodynamics.
72 citations
TL;DR: In this article, the Bauschinger effect in dual-phase steels has been computationally simulated, and the influence of phase stresses, developed due to nonhomogeneous deformation during preloading, on the BE has been investigated.
Abstract: The Bauschinger effect (BE) in dual-phase steels has been computationally simulated, and the influence of phase stresses, developed due to nonhomogeneous deformation during preloading, on the BE has been investigated. Isotropic-and anisotropic-hardening models were used in finite-element method calculation to produce the reverse flow stress-strain curves (compression) of dual-phase steels from the reverse stress-strain curves of single-phase materials. Aspects of the Bauschinger effect, including the rounding of the reverse flow curve, yielding at low reverse stresses, high initial work-hardening rates, and the absence of permanent softening,etc., were elucidated by the variation in phase stresses in the constituent phase.
70 citations
TL;DR: In this paper, the authors investigated thermal instabilities in forced convection boiling in a vertical single channel system, with Freon-11 as the working fluid, and they used finite difference techniques to determine the wall conditions, fluid properties and flow conditions at any point along the test section.
49 citations
TL;DR: In this paper, the authors define an N -order squeezing of the radiation field and study it in the M -photon interactions of a single-mode field with one atom and with two atoms.
48 citations
TL;DR: In this paper, two reciprocating compressor refrigeration systems were studied: (1) a conventional cycle with refrigerant migration through the capillary tube after compressor shut-down and (2) a system in which a magnetic cut-off valve was closed on compressor shutdown.
Abstract: Refrigerant migration during start-up and shut-down cycles can affect energy losses. Two reciprocating compressor refrigeration systems were studied: (1) a conventional cycle with refrigerant migration through the capillary tube after compressor shut-down and (2) a system in which a magnetic cut-off valve was closed on compressor shut-down. It was found that by preventing the refrigerant from migrating during shut-down, energy losses during start-up could be reduced, resulting in a 4% decrease in motor power input at this time. A computer program has been developed to calculate energy losses due to refrigerant migration.
38 citations
TL;DR: In this paper, the relationship between microscopic structure morphology and electrical strength of polypropylene (PP) film used in PP-laminated paper (PPLP) in very high voltage oil-filled cable is studied by several methods including infrared spectrum, X-ray diffraction and dynamic mechanical spectra.
Abstract: The relationship between the microscopic structure morphology and the electrical strength of polypropylene (PP) film used in PP-laminated paper (PPLP) in very high voltage oil-filled cable is studied by several methods including infrared spectrum, X-ray diffraction and dynamic mechanical spectra. It is found that the key to improve the breakdown strength, the tensile strength and the stability in oil for PP film is to increase its structure parameters, namely, its crystallinity, orientation and molecular weight. The interaction between PPLP and liquid dielectric is also studied. It is found that when it is immersed in dodecyl benzene at 100 degrees C, the strength of PP film decreases because the amorphous part dissolves and disorientation occurs. >
37 citations
TL;DR: In this paper, a finite element method was employed to calculate the effect of the prestrain, particle size, volume fraction, and yield strength ratio of the constituent phases on the Bauschinger effect and residual phase stresses for ferrite-martensite two-phase steels.
Abstract: A finite-element method has been employed to calculate the effect of the prestrain, particle size, volume fraction, and yield strength ratio of the constituent phases on the Bauschinger effect (BE) and residual phase stresses for ferrite-martensite two-phase steels. The relationships be-tween the BE parameters and residual phase stresses are given, and the basics of inelastic un-loading and the effect of reverse deformation on the BE and residual phase stresses are also discussed. Based on the decaying of the residual phase stresses (commonly called “back stresses”) during reverse loading, the relationship between back stresses and permanent softening has been elucidated. Some of the calculated results are compared with experimental ones, and good agree-ment between them is found.
TL;DR: In this paper, an analysis of the distribution of interlaminar stresses near free edges in composite laminates is presented, based on a heterogeneous model, as well as the macroscopically homogeneous model.
TL;DR: For three-point-bend specimens with different crack-depth in 50D steel, the principal reasons leading to the losing of J-dominance and the crackdepth dependence of Ji, were discovered by FEM calculations and experiments as discussed by the authors.
TL;DR: In this article, a local existence result for a coupled hyperbolic-parabolic initial boundary value problem is proved for the case of the first boundary value in the first order.
Abstract: We prove a local existence result for a coupled hyperbolic–parabolic initial boundary value problem.
TL;DR: The Cauchy problem is approximate by a problem in a bounded domain ΩR=(−R,R) withR>0 sufficiently large, and the boundary conditions on ∂ΩR are imposed in terms of the far field behavior of solutions to the Cauche problem.
Abstract: We approximate the Cauchy problem by a problem in a bounded domain Ω R =(−R,R) withR>0 sufficiently large, and the boundary conditions on ∂Ω R are imposed in terms of the far field behavior of solutions to the Cauchy problem. Then we solve this approximate problem by the finite element method for the spatial variable and the difference method for the time variable. Moreover a coupled numerical scheme for the Cauchy problem is presented. The error estimates are established.
TL;DR: Experiments using naphthalene sublimation technique were performed to investigate the heat transfer coefficients and friction factors for corrugated-fin and tube heat exchangers with different fin-spacing.
TL;DR: In this article, the authors provide three ballconvergence theorems as well as error estimates for certain iterative methods for solving nonlinear equations with non-differentiable operators in Banach spaces.
Abstract: This paper provides three ball-convergence theorems as well as error estimates for certain iterative methods for solving nonlinear equations with nondifferentiable operators in Banach spaces The results generalize and deepen those of Kantorovich [6], Mysovskii [8], Rheinboldt [10], Dennis [3], Yamamoto [12–15] and Zabrejko-Nguen[16]
TL;DR: In this article, the critical values of J- integral at initiation were independent of specimen geometries and crack depths and can be considered as the material constants, while the stress-strain fields in the crack tips of various specimens with different crack depths were in better agreement with the HRR solution in the plane stress case.
20 Aug 1990
TL;DR: In this article, the mechanisms of material erosion of Ag-base material contacts caused by breaking arcs up to several hundred amperes are studied and the factors influencing the contact erosion are analyzed; it is suggested that the electrode erosion should be the result of the heat force effects among arc, electrodes and environment.
Abstract: The mechanisms of material erosion of Ag-base material contacts caused by breaking arcs up to several hundred amperes are studied. The experiments breaking AC and half-wave sinusoidal current were carried out. The factors influencing the contact erosion are analyzed; it is suggested that the electrode erosion should be the result of the heat force effects among arc, electrodes, and environment. The main cause of obvious material transfer is the asymmetry of the heat force effects at two electrodes. It is indicated that there are two forms of liquid ejection: edge ejection and center ejection. The erosion modes are divided into several different modes, and each is detailed. A mode diagram is given, and the erosion features of Ag-base materials are described. >
TL;DR: In this article, the steady-state ionisation coefficient alpha and the electron attachment coefficient eta were measured in SF6/He gas mixtures using the steadystate Townsend method over the range 70
Abstract: The Townsend first ionisation coefficient alpha and the electron attachment coefficient eta were measured in SF6/He gas mixtures using the steady-state Townsend method over the range 70
TL;DR: In this paper, wear-corrosion tests of a composite metal containing WC particles were carried out in a water-sand medium containing various concentrations of sulphuric, hydrochloric and nitric acids.
TL;DR: In this article, an instrumented impact test was carried out by using the pre-cracked Charpy V-notch (PCVN) specimen to determine the J ld values in the upper shelf of API X-52 pipeline steel.
TL;DR: In this paper, a finite element program was developed based on Eisenberg's cyclic plasticity theory and the low cycle stress-strain response of the steels with duplex phase microstructures was calculated from the low cyclic curves of the single ferrite (steel F) and martensite (steel M) phase.
Abstract: — Fully reversed low cycle fatigue tests were carried out on 7 mm diameter cylindrical specimens of a dual phase steel treated to give five different microstructures, namely F—ferrite (+ little carbide particles), CF—continuous ferrite + 8.2% martensite, FM—49.1% ferrite + 50.9% martensite mixed structure, CM—continuous martensite + 22.4% ferrite and M—100% martensite. A finite element program was developed based on Eisenberg's cyclic plasticity theory and the low cycle stress-strain response of the steels with duplex phase microstructures was calculated from the low cyclic curves of the single ferrite (steel F) and martensite (steel M) phase. The experimental results show that fatigue performance of dual phase steel improves as martensite content is increased up to about 50%, thereafter it obviously deteriorates. During cyclic loading, the calculated plastic strain accumulated in ferrite is higher than that in martensite. Inhomogeneity of the plastic strain accumulation in steel CF is more pronounced than that in steel CM. In steel FM a relatively uniform strain distribution was found. Controlling the size of particle phase can result in an optimum strain distribution. Thus, the plastic deformation capability of the constituent phases can be enhanced leading to fatigue performance improvement. Crack initiation occurs easily at the ferrite/martensite interface with a coarse particle phase size, regardless of phase continuity. In steel CF, a crack initiates at the interface perpendicular to the stress axis and propagates in the ferrite matrix by deflecting around coarse martensite particles or by cutting fine martensite particles. In steel CM, a crack initiates at the interface along the stress axis and propagates in the martensite matrix through ferrite particles.
TL;DR: In this paper, the authors investigated the far field behavior of solutions to the Cauchy problem in one-dimensional nonlinear thermoelasticity, using the Fourier transform, the local-global existence, and the energy and decay estimates of solutions of the nonlinear equations.
Abstract: In this paper we investigate the far field behavior of solutions to the Cauchy problem in one-dimensional nonlinear thermoelasticity. We make use of the far field behavior of solutions of the linearized equations which is obtained by the Fourier transform, the local-global existence, and the energy and decay estimates of solutions of the nonlinear equations to obtain the desired results.
TL;DR: A couple of new results regarding set-valued measure are introduced and a theorem is offered which illustrates the application of set- valuation measure to fuzzy set- valued measure.
TL;DR: In this paper, a formulation and numerical implementation of boundary element methods (BEM) for the finite deformation problems of elastoplasticity is presented in updated Lagrangian description.
Abstract: A formulation and numerical implementation of boundary element methods (BEM) for the finite deformation problems of elastoplasticity is presented in this paper in updated Lagrangian description. This formulation has considered two kinds of traction rates. The velocity-gradient equation of inner point is fully deduced to meet the desire of higher order elements and cells. A scheme of iteration suitable for J 2 -flow theory is developed, too. Moreover an effective indirect quadrature is designed to overcome the diffuculty of evaluating Cauchy principal values of domain integrals; owing to this the quadratic isoparametric elements and cells are successfully introduced in the code BELEPA. Several numerical examples, including the necking of plate specimen, are presented at the end. An interesting phenomenon is observed from the results that the BEM analysis of necking is more sensitive to the initial imperfection of specimen than FEM analysis. Further investigation is needed to confirm this phenomenon.
TL;DR: In this paper, a modified Linear Elastic Fracture Mechanics (LEFM) parameter is proposed for a short through-thickness crack emanating from a notch root under elastic-plastic loading conditions.
Abstract: — The growth rate of a short fatigue crack that is partly or wholly embedded within the notch plastic zone, is affected by the extent and intensity of the elastic-plastic notch stress field and closure effect. The notch stress—strain field and plastic zone were analysed by the Finite Element Method (FEM). The growth rate and the closure curve for a short fatigue crack emanating from the notch root were measured. Based on the experimental and numerical analyses, a modified Linear Elastic Fracture Mechanics (LEFM) parameter is proposed for a short through-thickness crack emanating from a notch root under elastic—plastic loading conditions.
TL;DR: Etude de l'influence du diametre de lorifice, de lepaisseur du plateau and du debit de gaz sur le ruissellement de liquide.
Abstract: Etude de l'influence du diametre de l'orifice, de l'epaisseur du plateau et du debit de gaz sur le ruissellement de liquide
TL;DR: In this article, the authors studied the field in the N -phonon interaction of two two-level atoms with the radiation field initially in a squeezed state, and showed that the field can be squeezed in the presence of two level atoms.