• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.14-17
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• 1992

To analyze Nonvolatile SNOSFET(polySilicon-Nitride-Oxide-Semiconductor Field Effect Transistor) memory device, two dimensional numerical computer simulation program was developed. The equation discretization was performed by the Finite difference method and the solution was derived by the Iteration method. The doping profile of n-channel device which was fabricated by 1Mbit CMOS process was observed. The electrical potential and the carrier concentration distribution to applied bias condition were observed in the inner of a device. As a result of the write and the erase to memory charge quantity, the threshold voltage shift is expected. Therefore, without device fabrication, the operating characteristics of the device was observed under various the processing and the operating condition.

• Journal of applied mathematics & informatics
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• 제7권1호
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• pp.139-159
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• 2000

In this manuscript we study perturbed Newton-like methods for the solution of nonlinear operator equations in a Banach space and their discretized versions in connection with the mesh independence principle. This principle asserts that the behavior of the discretized process is asymptotically the same as that for the original iteration and consequently, the number of steps required by the two processes to converge to within a given tolerance is essentially the same. So far this result has been proved by others using Newton's method for certain classes of boundary value problems and even more generally by considering a Lipschitz uniform discretization. In some of our earlierpapers we extend these results to include Newton-like methods under more general conditions. However, all previous results assume that the iterates can be computed exactly. This is mot true in general. That in why we use perturbed Newton-like methods and even more general conditions. Our results, on the one hand, extend, and on the other hand, make more practical and applicable all previous results.

• Journal of applied mathematics & informatics
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• 제29권3_4호
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• pp.813-829
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• 2011

In this article, we present a numerical scheme for solving singularly perturbed (i.e. highest -order derivative term multiplied by small parameter) Burgers-Huxley equation with appropriate initial and boundary conditions. Most of the traditional methods fail to capture the effect of layer behavior when small parameter tends to zero. The presence of perturbation parameter and nonlinearity in the problem leads to severe difficulties in the solution approximation. To overcome such difficulties the present numerical scheme is constructed. In construction of the numerical scheme, the first step is the dicretization of the time variable using forward difference formula with constant step length. Then, the resulting non linear singularly perturbed semidiscrete problem is linearized using quasi-linearization process. Finally, differential quadrature method is used for space discretization. The error estimate and convergence of the numerical scheme is discussed. A set of numerical experiment is carried out in support of the developed scheme.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1800-1805
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• 2008

A "finite volume method" is proposed to predict heat transport in a spherical enclosure at micro/nanoscale with the Boltzmann transport equation (BTE). The gray version of the BTE with the relaxation time approximation has been applied. Pointing out similarity between radiative transfer equation (RTE) and BTE, the mapping process in RTE is adopted to treat the angular derivative term and linear algebraic discretization equation is derived by using the established method which is used in 2-D BTE in cartesian coordinates. The simulation results are compared to exact solution to RTE for various acoustic thicknesses and ratio of radii. The comparison shows that this method is logical and accurate, and it is possible to easily adopt various models in spherical BTE.

• Korea-Australia Rheology Journal
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• 제20권1호
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• pp.7-14
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• 2008

The objective of this work is to propose a procedure to simulate the flow in the LCM (Liquid Composites Molding) processes by finite difference discretization in a curvilinear coordinate system adapted to the shape of the saturated zone. The numerical results obtained are compared with experimental results obtained by an experimental device elaborated at our laboratory. It allows to realize linear and radial injections for different porosities and to observe the flow front kinetics. Numerical and experimental results are then compared with those of the literatures and excellent agreements are noticed. Finally, we suggest a concept of the capillary number to explain the variations of the permeability obtained for pressure values lower than 0.25 Bar.

• 한국정밀공학회지
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• 제20권12호
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• pp.148-158
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• 2003

In this paper, efficient and accurate contact search algorithm is proposed for the contact problems by the finite element method. A slave node and a maser contact segment is defined using the side of a finite element on the contact surface. The specific goal is to develop techniques of reducing the nonsmoothness of the contact interactions arising from the finite element discretization of the contact surface. Contact detection is accomplished by monitoring the territory of the slave nodes throughout the calculation for possible penetration of a master surface. To establish the validity of the proposed algorithm, some different process and geometries examples were simulated. Efforts are focused on the error rate that is based on the penetrated area through the simulations fur large deformation with contact surface between deformable bodies. A proposed algorithm offers improvements in contact detection from the simulation results.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1030-1036
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of space structure floating in space. In dealing with the dynamics of space structure, the use of Lagrange's equations of motion in terms of quasi-coordinates were suggested to derive hybrid equations of motion for rigid-body translations and elastic vibrations. The perturbation method is then applied to the hybrid equations of motion along with discretization by means of admissible functions. This process is very tiresome. Recently, a new approach that applies the perturbation method to the Lagrange's equations directly was proposed and applied to the two-dimensional floating structure. In this paper. we propose the application of the perturbation method to the Lagrange's equations of motion in terms of quasi-coordinates. Theoretical derivations show the efficacy of the proposed method.

• 소성∙가공
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• 제12권4호
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• pp.340-347
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• 2003

In the rigid-plastic finite element simulation of hot forging processes using hexahedral mesh, remeshing of a flash is important for design and control of the process to obtain desirable defect-free products. The mesh compression method is a remeshing technique which enables the construction of an effective hexahedral mesh in the flash. However, because the mesh is distorted during the compression procedure of the mesh compression method, when it is used in resuming the analysis, it causes discretization error and decreases the conversance rate. Therefore, mesh smoothing is necessary to improve the mesh quality. In this study, several geometric mesh smoothing techniques and optimization techniques are introduced and modified to improve mesh quality. Then, the most adaptive technique is recommended for the mesh compression method.

• 한국정밀공학회지
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• 제12권6호
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• pp.128-136
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• 1995

The problem addressed in this paper is that of the on-line computational burden of time-optimal control laws for quick, strongly nonlinear systems like revolute robots. It will be demonstrated that a large amount of off-line computation can be substituted for most of the on-line burden in cases of time optimization with constrained inputs if differential point-to- point specifications can be relaxed to cell-to-cell transitions. These cells result from a coarse discretization of likely swaths of state space into a set of nonuniform, contiguous volumes of relatively simple shapes. The cell boundaries approximate stream surfaces of the phase fluid and surfaces of equal transit times. Once the cells have been designed, the bang- bang schedules for the inputs are determined for all likely starting cells and terminating cells. The scheduling process is completed by treating all cells into which the trajectories might unex- pectedly stray as additional starting cells. Then an efficient-to-compute control law can be based on the resulting table of optimal strategies.

• Journal of applied mathematics & informatics
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• 제40권3_4호
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• pp.603-618
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• 2022

In this paper, a numerical solution of the generalized diffusion equation with a delay has been obtained by a numerical technique based on the Galerkin finite element method by applying the cubic B-spline basis functions. The time discretization process is carried out using the forward Euler method. The numerical scheme is required to preserve the delay-independent asymptotic stability with an additional restriction on time and spatial step sizes. Both the theoretical and computational rates of convergence of the numerical method have been examined and found to be in agreement. As it can be observed from the numerical results given in tables and graphs, the proposed method approximates the exact solution very well. The accuracy of the numerical scheme is confirmed by computing L₂ and L_∞ error norms.