ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677829

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

From the view‐point of economy and durability, a methodology of mix proportioning for high‐performance concrete (HPC) based on the concept of using the “minimum volume of cement paste binder” is presented in this paper. Since the cement is the most expensive ingredient of concrete, and excessive cement in concrete usually results in a higher heat of hydration and increases creep and shrinkage that, in turn, adversely influences the durability of concrete, an essential mix‐design rule is to make HPC with a minimum amount of cement. Accordingly, the minimum void content for the mixture of dry coarse aggregate, sand and mineral admixture in HPC is a major controlling factor in the proposed methodology. Two approaches for properly estimating individual amount of concrete ingredients are presented and discussed. Finally, experimental results of high‐performance concrete manufacture according to the proposed proportioning methodology are shown and addressed for its validity.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677830

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A theoretical study is undertaken to investigate the nonlinear buckling behavior of fiber‐reinforced laminated composite plates under hygrothermal environments. The first‐order shear deformation plate theory is adopted herein in order to explain deflections, rotations, and dimensional and constitutive changes due to moisture‐induced swelling effects and temperature‐induced expansions and contractions. The finite element modeling is then employed as numerical analysis to describe the nonlinear buckling behavior of a laminated composite plate subjected to a variety of hygrothermal conditions for various boundary conditions. The governing equations of the nonlinear buckling behavior for laminated composite plates is solved by an iterative numerical method. The nonlinear buckling behavior of unsymmetric and symmetric laminated composite plates in hygrothermal environments are discussed as illustrative examples to demonstrate the significance of severe hygrothermal effects in buckling issues for laminated composite plates. It is anticipated that this work will be significantly relevant to applications in the defense, aerospace and manufacturing environments, where severe variations in moisture and temperature may occur.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677831

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The steady separated flow due to heated blocks mounted on one principal wall of a two‐dimensional channel has been numerically and experimentally studied. Numerical solutions of the Navier‐Stokes equations using the finite‐difference and the power‐law techniques have been obtained up to a Reynolds number of 2600. The effects of the Reynolds number and the block spacing on the fluid flow and heat transfer are investigated in detail. Results show that there exists two different types of flow between blocks, the D‐type and the K‐type flows. Furthermore, the Nusselt number monotonously increases or decreases along every face of the blocks. The calculated results of the reattachment length behind the second block and the local Nusselt number distribution compare well with the results obtained by the LDV and the naphthalene sublimation measurements, respectively. Heat transfer correlating equations are presented in terms of the Reynolds number and the block spacing.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677832

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Modal interaction usually occurs in a spinning disk under stationary load systems when two modes are almost degenerate. This paper investigates the mathematical structure of various types of modal interactions analytically by a two‐mode eigenfunction expansion technique. Emphasis is given to the effect of the number of load systems on the eigenvalues of the coupled system. Generally speaking, the frequency loci may merge together (when one of these two modes is a reflected wave) or veer away (when both modes are non‐reflected) when the difference between the numbers of nodal diameters of these two modes is equal to a multiple of the number of the stationary load systems. Otherwise, the natural frequency loci simply cross each other and no instability is induced. In applying these rules the number of nodal diameters of aforwardor areflectedwave is considered asnegative.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677833

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A finite element numerical procedure for the analysis of torsional behavior of cracked reinforced concrete pile is proposed. A trilinear torque‐twist model is used to represent the torsional response of the reinforced concrete pile element with maximum torsional stresses. The remaining part of the pile is modeled as a linear elastic torsional behavior. The soil torsional resistance along pile shaft is represented by the nonlinear springs, modeled as the hyperbolic function, acting at the midpoint of each pile element. The proposed hyperbolic function is compared against available experimental results and showed to be very satisfactorily. Both linear and nonlinear analyses were performed and showed the importance of taking into account the changing of pile stiffness once concrete has cracked.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677834

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The partial differential equation, describing the lateral deflection of textile, nonlinearly coupled with one ordinary differential equation, describing the whirling vibration of rotor with constant angular velocity, are investigated in the dynamic stability analysis. When the textile is wound on or off by the rotor, the mass, inertia and unbalance magnitude of rotor are time‐varying, and the length of textile is time‐dependent. The Galerkin method with time‐varying basis function is used to simplify the partial differential equation as a set of nonlinear time‐varying ordinary differential equations. Assuming the initial tension is characterized as a steady‐state value, superimposed by a small perturbation, the system will be a weakly non‐autonomous system. Thus the perturbation method can be used to obtain periodic solution for the system. Herein multiple‐scale method is used to obtain the domain of instability as a function of the perturbation frequency and perturbation amplitude. The results is used to estimate the location and extent of resonance instability due to the coupling of internal and parametric resonance.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677835

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper, we use the importance sampling (IS) method to evaluate the bit error rate (BER) for systems employing nonlinear synchronizers. It is shown by simulation results that the sample sizes required by the IS method for evaluating the BER of systems with nonlinear synchronizers are almost constant for various values of signal‐to‐noise ratio (SNR). This implies that the efficiency of IS to MC method approaches infinity as the SNR becomes very high. It is also shown in this paper that for differential decoding of QPSK signals, the error performance of a system with nonlinear synchronizer of size 15 is close to that of a coherent system.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677836

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The nearest neighbor (NN) searching problem has wide applications. In vector quantization (VQ), both the codebook generation phase and encoding phase (using the codebook just generated) often need to use the NN search. Improper design of the searching algorithm will make the complexity quite big as vector dimensionalitykor codebook sizeNincreases. In this paper, a fast NN searching method is proposed, which can then accelerate the LBG codebook generation process for VQ design. The method successfully modifies and improves the LAESA method. Unlike LAESA, the proposedk/2 “fixed” points (allocated far from the data) and the origin are used as thek/2+1 reference points to reduce the searching area. The overhead in memory is only linearly proportional toNandk.The time complexity, including the overhead, is of order O(kN). According to our experiments, the proposed algorithm can reduce the time burden while the distortion remains identical to that of the full search.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677837

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A globally exponentially (asymptotically) stabilizing composite feedback control is proposed in this paper for a general class of nonlinear multiple time‐delay singularly perturbed systems in which the slow subsystem is exponentially stable in the absence of the fast states. The chosen design manifold under this composite feedback control becomes an exact integral manifold and the trajectories of the closed‐loop systems are steered globally along the integral manifold to the origin exponentially, with some guaranteed convergence rate, for all sufficiently small singular perturbation parameterϵ.

ISSN:0253-3839    

DOI:10.1080/02533839.1996.9677838

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor