• Structural Engineering and Mechanics
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• v.43 no.2
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• pp.211-223
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• 2012

This paper deals with large deformation post-buckling of a linear-elastic and hygrothermal beam with axially nonmovable pinned-pinned ends and subjected to a significant increase in swelling by an alternative method. Analytical approximate solutions for the geometrically nonlinear problem are presented. The solution for the limiting case of a string is also obtained. By coupling of the well-known Maclaurin series expansion and orthogonal Chebyshev polynomials, the governing differential equation with sinusoidal nonlinearity can be reduced to form a cubic-nonlinear equation, and supplementary condition with cosinoidal nonlinearity can also be simplified to be a polynomial integral equation. Analytical approximations to the resulting boundary condition problem are established by combining the Newton's method with the method of harmonic balance. Two approximate formulae for load along axis, potential strain for free hygrothermal expansion and periodic solution are established for small as well as large angle of rotation at the end of the beam. Illustrative examples are selected and compared to "reference" solution obtained by the shooting method to substantiate the accuracy and correctness of the approximate analytical approach.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.461-472
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• 2015

In this paper, the nonlinear static response of curled cantilever beam actuators subjected to the one-sided electrostatic field is focused on. By assuming the deflection function of electrostatically actuated beam, analytical approximate solutions are established via using Galerkin method to solve the equilibrium equation. The Pull-In voltages which determine the stability of the curled beam actuators are also obtained. These approximate solutions show excellent agreements with numerical solutions obtained by the shooting method and the experimental data for a wide range of beam length. Expressions of these analytical approximate solutions are brief and could easily be used to derive the effects of various physical parameters on MEMS structures.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.655-661
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• 2014

In this paper, a new two dimensional (2D) analytical modeling and simulation for a surrounding gate tunnel field effect transistor (TFET) is proposed. The Parabolic approximation technique is used to solve the 2-D Poisson equation with suitable boundary conditions and analytical expressions for surface potential and electric field are derived. This electric field distribution is further used to calculate the tunneling generation rate and thus we numerically extract the tunneling current. The results show a significant improvement in on-current characteristics while short channel effects are greatly reduced. Effectiveness of the proposed model has been confirmed by comparing the analytical results with the TCAD simulation results.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1471-1481
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• 2022

This paper aims to present a new method for obtaining an analytical solution for the Kaniadakis Doppler broadening (KDB) function. Also, in this work, we report the computational efficiencies of this solution compared with the numerical one. The solution of the differential equation achieved in this paper is free of approximations and is, consequently, a more robust methodology for obtaining an analytical representation of ψ_k. Moreover, the results show an improvement in efficiency using the analytical approximation, indicating that it may be helpful in different applications that require the calculation of the deformed Doppler broadening function.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.77-85
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• 1999

By assuming a linearly graded depletion edge approximation in the intrinsic MOS region and by taking into account the mobility variation dependent on both lateral and vertical fields, a physics-based analytical model for a short-channel(n-channel) MOSFET is suggested. Derived expressions for the threshold voltage and the drain current of typical MOSFET is structures could be used in a unified manner for all operating range. The threshold voltage was calculated by changing following variables : channel length, drain-source voltage, source-substrate voltage, p-substrate doping level, and oxide thickness. It is shown that the threshold voltage decreases almost exponentially as the channel length decreases. In addition, the short-channel threshold voltage roll-off, the channel length modulation and the electron mobility degradation can be derived within a satisfactory accuracy.

• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.61-68
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• 2001

In this paper, an analytical method and a difference approximation method to calculate the gradient of an objective function have been applied to the directivity optimization in an adaptive ultrasonic transducer which is combined with a point source array and an optimization algorithm (DFP method). To compare these two methods, quasi-ideal .beam with a beam width and direction specified are chosen as the desired directivity. As the numerical results, the difference approximation method shows better suppressive capacity of side lobe level, good stability in the convergence processing, faster convergence speed and excellent adaptability compared with the analytical method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.117-126
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• 2009

In order to test the accuracy between the modified mild slope equation (MMSE) without evanescent modes and the plane-wave approximation (PA) of eigenfunction expansion method, various numerical results from both models are presented. In this study, analytical solutions of two models are employed, one based on the MMSE derived by Porter (2003) and the other on the scatterer method of PA by Seo (2008a). Judging from direct comparisons against existing results of rapidly varying topography, the PA model gives better predictions of the wave propagation than the MMSE model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.310-317
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• 2006

In this paper, we propose a new sequential message-passing decoding algorithm of low-density parity-check (LDPC) codes by partitioning check nodes. This new decoding algorithm shows better bit error rate(BER) performance than that of the conventional message-passing decoding algorithm, especially for small number of iterations. Analytical results tell us that as the number of partitioned subsets of check nodes increases, the BER performance becomes better. We also derive the recursive equations for mean values of messages at variable nodes by using density evolution with Gaussian approximation. Simulation results also confirm the analytical results.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.491-496
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• 2003

In sensitivity analysis, semi-analytical method(SAM) reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Recently such errors of SAM resulted by the finite difference scheme have been improved by the separation of rigid body mode. But the eigenvalue should be obtained first before the sensitivity analysis is performed and it takes much time in the case that large system is considered. In the present study, by constructing a reduced one from the original system, iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The sensitivity analysis is performed by the eigenvector acquired from the reduced system. The error of SAM caused by difference scheme is alleviated by Von Neumann series approximation.

• Smart Structures and Systems
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• v.10 no.2
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• pp.155-179
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• 2012

This paper aims at assessing the seismic performance of Tuned Mass Dampers (TMDs) based on sets of recorded ground motions. For the simplest configuration of a structure-TMD assembly, in a comprehensive study characteristic response quantities are derived and statistically evaluated. Optimal tuning of TMD parameters is discussed and evaluated. The response reduction by application of a TMD is quantified depending on the structural period, inherent damping of the stand-alone structure, and ratio of TMD mass to structural mass. The effect of detuning on the stroke of the TMD and on the structural response is assessed and quantified. It is verified that a TMD damping coefficient larger than the optimal one reduces the peak deflection of the TMD spring significantly, whereas the response reduction of the main structure remains almost unaffected. Analytical relations for quantifying the effect of a TMD are derived and subsequently evaluated. These relations allow the engineer in practice a fast and yet accurate assessment of the TMD performance.