The Experts below are selected from a list of 49296 Experts worldwide ranked by ideXlab platform
Liqun Chen - One of the best experts on this subject based on the ideXlab platform.
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DETC2005-84439 REDUCTION OF VIBRATION FOR AN AXIALLY MOVING STRING WITH A TENSIONER
2020Co-Authors: Liqun Chen, Wei ZhangAbstract:ABSTRACT This paper deals with reducing transverse vibration for an axially moving string by a damped tensioner. The Governing Equation and the boundary conditions are derived for the system. Based on the analysis of the reflection and transmission of waves propagating along the string, the maximal energy dissipation is realized by determining the optimal damping. To simulate numerically the effect of vibration reduction, the Crank-Nicolson scheme is applied to discretize the Governing Equation of the string. The numerical results demonstrate the optimality of the determined damping in suppressing the transverse vibration
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stability analysis and numerical confirmation in parametric resonance of axially moving viscoelastic plates with time dependent speed
European Journal of Mechanics A-solids, 2013Co-Authors: Youqi Tang, Liqun ChenAbstract:Abstract In this paper, stability in parametric resonance of axially moving viscoelastic plates subjected to plane stresses is investigated. The plate material obeys the Kelvin–Voigt model in which the material time derivative is used. The generalized Hamilton principle is employed to obtain the Governing Equation. The axial speed is characterized as a simple harmonic variation about the constant mean speed. The Governing Equation can be regarded as a continuous gyroscopic system with small periodically parametric excitations and a damping term. The method of multiple scales is applied to the Governing Equation to establish the solvability conditions in principal and summation parametric resonances. The natural frequencies and modes of linear generating Equation are numerically calculated based on the given boundary conditions. The necessary and sufficient condition of the stability is derived from the Routh–Hurwitz criterion. Some numerical examples are presented to demonstrate the effects of related parameters on the frequencies and the stability boundaries. The differential quadrature scheme is developed to solve numerically the linear generating system and the primitive Equation model. The numerical calculations confirm the analytical results.
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nonlinear combination parametric resonance of axially accelerating viscoelastic strings constituted by the standard linear solid model
Science China-technological Sciences, 2010Co-Authors: Liqun Chen, Hao Chen, Hu Ding, C W LimAbstract:Nonlinear combination parametric resonance is investigated for an axially accelerating viscoelastic string. The Governing Equation of in-planar motion of the string is established by introducing a coordinate transform in the Eulerian Equation of a string with moving boundaries. The string under investigation is constituted by the standard linear solid model in which the material, not partial, time derivative was used. The Governing Equation leads to the Mote model for transverse vibration by omitting the longitudinal component and higher order terms. The Kirchhoff model is derived from the Mote model by replacing the tension with the averaged tension over the string. The two models are respectively analyzed via the method of multiple scales for principal parametric resonance. The amplitudes and the existence conditions of steady-state response and its stability can be numerically determined. Numerical calculations demonstrate the effects of the string material parameters, the initial tension, and the axial speed fluctuation amplitude. The outcomes of the two models are qualitatively and quantitatively compared.
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stability in parametric resonance of axially accelerating beams constituted by boltzmann s superposition principle
Journal of Sound and Vibration, 2006Co-Authors: Xiaodong Yang, Liqun ChenAbstract:Stability in transverse parametric vibration of axially accelerating viscoelastic beams is investigated. The Governing Equation is derived from Newton's second law, Boltzmann's superposition principle, and the geometrical relation. When the axial speed is a constant mean speed with small harmonic variations, the Governing Equation can be treated as a continuous gyroscopic system with small periodically parametric excitations and a damping term. The method of multiple scales is applied directly to the Governing Equation without discretization. The stability conditions are obtained for combination and principal parametric resonance. Numerical examples demonstrate that the increase of the viscosity coefficient causes the lager instability threshold of speed fluctuation amplitude for given detuning parameter and smaller instability range of the detuning parameter for given speed fluctuation amplitude. The instability region is much bigger in lower order principal resonance than that in the higher order.
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stability in parametric resonance of axially moving viscoelastic beams with time dependent speed
Journal of Sound and Vibration, 2005Co-Authors: Liqun Chen, Xiaodong YangAbstract:Stability in transverse parametric vibration of axially accelerating viscoelastic beams is investigated. The Governing Equation is derived from Newton's second law, the Kelvin constitution relation, and the geometrical relation. When the axial speed is a constant mean speed with small harmonic variations, the Governing Equation can be regarded as a continuous gyroscopic system under small periodically parametric excitations and a damping term. The method of multiple scales is applied directly to the Governing Equation without discretization. The stability conditions are obtained for combination and principal parametric resonance. Numerical examples are presented for beams with simple supports and fixed supports, respectively, to demonstrate the effect of viscoelasticity on the stability boundaries in both cases.
Paotung Hsu - One of the best experts on this subject based on the ideXlab platform.
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an inverse approach for estimation of the surface heat flux distribution on a horizontal elliptical tube with laminar film condensation
Chemical Engineering Journal, 2002Co-Authors: Paotung Hsu, Yihhsiung Liu, Shenggwo Wang, Chaokuang ChenAbstract:Abstract A direct method is developed for determining the wall heat flux in film condensation on a horizontal elliptical tube. A finite-difference method is employed to discretize the condensation domain, and then a linear inverse model is constructed to identify the unknown conditions. The inverse analysis is based on the assumption that the film thickness measurements are available over the domain. Our approach is to rearrange the matrix forms of the differential Governing Equation and estimate the unknown surface conditions. Then, the linear least-squares method is adopted to find the solution. For condensation problem, the Governing Equation is non-linear. The present woke proposes a transformed treatment for solving both inverse and direct problems. In contrast to the traditional approach, the advantage of this method in inverse analysis is that no prior information is needed on the functional form of the unknown quantities, no initial guess is required and the iterations of calculation process need be done only once. Finally, the effects of measurement errors, sensor positions and the measurement points on the inverse solutions are discussed.
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an inverse problem for determining the wall heat flux in laminar film condensation on a finite sized horizontal plate with a variable heat flux
Journal of Physics D, 1999Co-Authors: Paotung HsuAbstract:An inverse model for determining the wall heat flux in filmwise condensation on a horizontal plate is presented. The inverse analysis is based on the film-condensation-thickness readings taken at several different points on the plate. Finite-difference methods are employed to discretize the problem domain and then a linear inverse model is constructed to identify the unknown conditions. This approach taken is to rearrange the matrix forms of the differential Governing Equation and estimate the unknown surface conditions. Then, the linear least-squares method is adopted to find the solution. In the direct problem, the present study considers that the boundary condition at the plate edge can be directly obtained from the concept of minimum energy inherited from the condensate flow rate rather than arbitrarily assumed. For the condensation problem, the Governing Equation is nonlinear. This paper proposes a linear transformation for solving both inverse and direct problems. In contrast to the traditional approach, the advantage of applying this method to inverse analysis is that no prior information on the functional form of the unknown quantities is needed, no initial guess is required and the iterations of the calculation process need be done once only.
Chaokuang Chen - One of the best experts on this subject based on the ideXlab platform.
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an inverse approach for estimation of the surface heat flux distribution on a horizontal elliptical tube with laminar film condensation
Chemical Engineering Journal, 2002Co-Authors: Paotung Hsu, Yihhsiung Liu, Shenggwo Wang, Chaokuang ChenAbstract:Abstract A direct method is developed for determining the wall heat flux in film condensation on a horizontal elliptical tube. A finite-difference method is employed to discretize the condensation domain, and then a linear inverse model is constructed to identify the unknown conditions. The inverse analysis is based on the assumption that the film thickness measurements are available over the domain. Our approach is to rearrange the matrix forms of the differential Governing Equation and estimate the unknown surface conditions. Then, the linear least-squares method is adopted to find the solution. For condensation problem, the Governing Equation is non-linear. The present woke proposes a transformed treatment for solving both inverse and direct problems. In contrast to the traditional approach, the advantage of this method in inverse analysis is that no prior information is needed on the functional form of the unknown quantities, no initial guess is required and the iterations of calculation process need be done only once. Finally, the effects of measurement errors, sensor positions and the measurement points on the inverse solutions are discussed.
Haisheng Shu - One of the best experts on this subject based on the ideXlab platform.
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free vibration analysis of closed moderately thick cross ply composite laminated cylindrical shell with arbitrary boundary conditions
Materials, 2020Co-Authors: Dongyan Shi, Qingshan Wang, Haisheng ShuAbstract:A semi-analytic method is adopted to analyze the free vibration characteristics of the moderately thick composite laminated cylindrical shell with arbitrary classical and elastic boundary conditions. By Hamilton’s principle and first-order shear deformation theory, the Governing Equation of the composite shell can be established. The displacement variables are transformed into the wave function forms to ensure the correctness of the Governing Equation. Based on the kinetic relationship between the displacement variables and force resultants, the final Equation associated with arbitrary boundary conditions is established. The dichotomy method is conducted to calculate the natural frequencies of the composite shell. For verifying the correctness of the present method, the results by the present method are compared with those in the pieces of literatures with various boundary conditions. Furthermore, some numerical examples are calculated to investigate the effect of several parameters on the composite shell, such as length to radius ratios, thickness to radius ratios and elastic restrained constants.
Mohamed Abdelsabour Fahmy - One of the best experts on this subject based on the ideXlab platform.
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a new lrbfcm gbem modeling algorithm for general solution of time fractional order dual phase lag bioheat transfer problems in functionally graded tissues
Numerical Heat Transfer Part A-applications, 2019Co-Authors: Mohamed Abdelsabour FahmyAbstract:AbstractThe main objective of this article is to propose a new hybrid modeling algorithm based on combining local radial basis function collocation method (LRBFCM) and general boundary element method (GBEM) for solving time fractional-order dual phase lag bioheat transfer problems in functionally graded tissues. The LRBFCM was developed and implemented using an implicit time-stepping technique and Caputo time fractional derivative for solving the fractional-order Governing Equation without dual phase lags. Due to suitability of the GBEM for modeling of bioheat transfer in functionally graded tissues. Therefore, GBEM is applied for solving the dual phase lags Governing Equation without fractional-order derivative. The numerical results are depicted graphical forms to show the effects of functionally graded parameter, fractional-order parameter and anisotropy on the nonlinear temperature distribution. Also, these numerical results demonstrate the validity and accuracy of the proposed algorithm and technique.
