• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.771-775
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• 2011

This paper presents design process of linear induction motor in dynamic tester for catenary-current collection. To minimize length of rail for dynamic tester for catenary-current collection, accelerating performance of the linear induction motor is very important. So the design process of linear induction motor considered in this paper is different with general design process of linear induction motor, because dynamic tester has three type driving region, as accelerating region, constant speed region, and braking region. Considering accelerating performance of motor, distance and time from starting point to constant speed region were concerned for load condition of motor. Designed linear induction motor was analyzed by 2-dimensional finite element method. Using mechanical dynamics simulation with analysis result of 2-dimensional finite element method and accelerating performance of designed motor was proved.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.53.2-53.2
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• 2011

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles indicating the presence of a relativistic accretion disk model. Using a Monte Carlo technique, we compute the linear polarization of a double peaked broad emission line. A Keplerian accretion disk is adopted for the double peak emission line region and the Schwarzschild geometry is assumed in the emission region. Far from the accretion disk where flat Minkowski geometry is appropriate, we place a scattering region in the shape of a spherical shell sliced. We generate a line photon in the accretion disk in an arbitraray direction in the local rest frame and follow the geodesic of the photon until it hits the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the linear degree of polarization also shows a double peak structure. Under a favorable condition we show that up to 1% of linear degree of polarization may be obtained.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.131-134
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• 2003

In this paper, we consider the problem of finding the stability region in state space for uncertain linear systems with input saturation. For stability analysis, two Lyapunov functions are chosen. One is for the lineal region and the other is for the saturated legion. Piecewise Lyapunov functions are obtained by solving successive linear matrix inequalites(LMIs) relaxations. A sufficient condition for robust stability is derived in the form of stability region of initial conditions. A numerical example shows the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.4
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• pp.183-190
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• 2000

It is well-known that the poles of a system are closely related with the dynamics of the systems, and the pole assignment problem, which locates the poles in the desired regions, in one of the major problem in control theory. Also, it is always possible to assign poles to specific points for exactly known linear systems. But, it is impossible for the uncertain linear systems because of the uncertainties that originate from modeling error, system variations, sensing error and disturbances, so we must consider some regions instead of points. In this paper, we consider both the analysis and the design of robust pole assignment problem of linear system with time-varying uncertainty. The considered uncertainties are the unstructured uncertainty and the structured uncertainty, and the considered region is the circular region. Based on Lyapunov stability theorem and linear matrix inequality(LMI), we first present the analysis result for robust pole assignment, and then we present the design result for robust pole assignment. Finally, we give some numerical examples to show the applicability and usefulness of our presented results.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.2
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• pp.119-128
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• 1994

There are three important regions im Multiple Objective Linear Programming (MOLP). One is the region of efficient solutions, another is the region of weight to be used for finding efficient solutions, the third is the region of efficient (nondominated) objective values. In this paper, first, we find the condition of extreme point in the region of efficient objective values. Second, we find that the sum of the dimension of the weight region and the dimension of efficient objective values region is constant. Using the above, it is shown that we find the shape and dimension of weight region corresponding to the given region or efficient objective values and vice versa.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.1-23
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• 2005

The decentralized static output feedback design problem is considered. A constrained trust region method is developed that solves this optimal control problem when a complete set of state variables is not available. The considered problem is interpreted as a non-linear (non-convex) constrained matrix optimization problem. Then, a decentralized constrained trust region method is developed for this problem class exploiting the diagonal structure of the problem and using inexact computations. Finally, numerical results are given for the proposed method.

• Journal of The Korean Astronomical Society
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• v.44 no.2
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• pp.59-65
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• 2011

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with ${\Delta}{\mu}=0.1$. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.9-13
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• 1997

In this paper, the operation regions of a three-phase voltage-source PWM converter are defined: linear modulation region, allowed current region, linear control region, unity power-factor region, and power-factor decreasing region. Particularly, the power-factor decreasing region is first examined and defined as the region where both the sinusoidal input current control and the stable DC link voltage regulation can not be obtained with a unity power-factor operation. To avoid these undesirable effects, the optimal current vector is derived, which ensures the sinusoidal input current and the stable DC link voltage regulation with maximum power-factor available, and, in consequence, it extends the operation region of the PWM converter. The validity of the proposed control scheme is proved by the computer simulation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.129-135
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• 1998

The characteristic of load-distribution is investigated by using nonlinear analysis with a field loading test of existing bridge In this study, nonlinear load-distribution technique for quantitative analysis was adopted. The results were compared with linear solution technique with data from failure test at existing RCT-girder bridge and examine the adequacy of the failure mode. The results of this study showed that the linear solution technique and the proposed nonlinear solution technique agreed well in linear region but did not matched well in nonlinear region because of load-redistribution, and that the effect of load-redistribution was considered to analysis of nonlinear region by linear solution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1238-1246
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• 2004

Momentum exchange theory has been generally used for an analysis of the regenerative turbomachines due to its direct description of the complicate circulatory flow. However, because its application is limited only to linear region and its model equations are incomplete on three variables, it needs further refinements. In the present study it is improved by introducing a central pivot of circulatory flow. Also, by assuming linear circulatory velocity distribution, mean radii of inlet and outlet flows through the impeller are newly suggested. By applying control volume analysis to both linear region and the acceleration region, the governing equation on the circulatory velocity is derived. As a result, systematic performance analysis on the entire region of the incompressible regenerative turbomachines can be carried out based on the proposed model equations.