• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.264-266
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• 1999

본 논문에서는 한전의 전력 계통 시뮬레이터(KEPS)에서 수행되어질 2010년 한전 계획 계통의 축약 계통을 자동으로 구성하는 프로그램의 개발에 대한 연구를 기술하였다. 먼저 한전 계통의 계통 데이터의 효율적인 관리를 위하여 데이터베이스를 구축하였고, 이를 이용하여 원계통의 데이터를 입력받아서 축약 계통의 데이터를 생성해내는 동적 축약 프로그램을 개발하였다. 동적 축약 프로그램은 각 발전기들의 특성을 분석하여 그룹화하는 식별부분과 이러한 식별과정을 거쳐서 구성된 발전기 그룹을 합쳐서 등가발전기로 구성하는 통합부분으로 이루어져 있으며 식별과정의 결과를 파일로 출력해내고 이를 수정할 수 있도록 하였다. 생성된 축약 계통과 원계통에 대해 조류 계산 및 동적 모의를 시행하여 그 응답특성을 비교하였다.

• Computational Structural Engineering
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• v.6 no.2
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• pp.95-102
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• 1993

A modeling method is described to provide a smaller structural dynamic model which can be used to compare finite element model of a structure with its experimental counterpart. A structural dynamic model is assumed to be represented by dynamic stiffness matrix. To validate a finite element model, it is often necessary to condense a large degrees of freedom (dofs) to a relatively small number of dofs. For these purpose, static reduction techniques are widely used. However, errors in these techniques are caused by neglecting frequency dependent terms in the functions relating slave dofs and master dofs. An alternative method is proposed in this paper in which the frequency dependent terms are considered by expressing the reduced dynamic stiffness matrix with orthogonal polynomials. The reduced model has finally a minimum set of dofs, such as sensors and excitation points and it is under the same condition as the physical system. It is proposed that the reduced model can be derived from finite element model. The procedure is applied to example structure and the results are discussed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.589-596
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• 2014

Joints, fasteners or connected parts frequently have a significant effect on the dynamical behavior of assembled mechanical structures. Therefore, the analytical prediction of structural responses depends on the accuracy of joint modeling. This paper deals with the formulation and analysis of dynamic mechanism for joint flexibilities whose relevant magnitudes of stiffnesses are investigated by using linear and torsional springs. The equation of motion is derived by using a generic joint in the middle of clamped-clamped beam. A reanalysis due to changes in magnitudes of joint stiffnesses is based on the reduced analysis where the binomial series terms are used as basis vectors. The solution procedures are straightforward and the method can be readily used with a general finite element method. The computational effort needed by this approach is usually much smaller than the effort needed for complete vibration analysis. Two numerical examples show that accurate results are obtained efficiently by reducing the number of degree in the reduced model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.200-201
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• 2016

Recently, according to era of Internet of Things was opened, various mobile devices connected to the internet using wireless communication. Many IoT devices have limited communication performance. Thus, these devices efficiently forward data using an abbreviated ID method. However, movement of devices causes abbreviated ID confliction, and These conflict degraded network performance. Therefore it is important management of ID conflict. In this paper, we proposed an abbreviated ID conflict management method to improve the efficiency of communication in the dynamic IoT network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1720-1725
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• 2019

In this paper, we consider the efficiency of the scheme for for routing summary algorithms in discontiguous networks. Router than updating and transmitting the entire subnet information in the routing protocol, only the shortened update information is sent and the routing table is shortened to make the router resources more efficient and improve network stability and performance. However, if a discontiguous network is formed in the network design process, a problem arises due to the network contraction function and does not bring about the result of fundamental router efficiency. Using different major networks subnets one major network, causing problems in communication and routing information exchange if the configuration is incorrect. The algorithm proposed in this paper removes only the auto-summary algorithm from the existing algorithm, which increases the complexity and stability of the routing table and reduces the CPU utilization of network equipment from 16.5% to 6.5% Confirmed.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.46-50
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• 2011

In order to perform the satellite structural analysis, FE-Model(Finite Element Model) considering all mechanical properties is necessary. Generally, different companies develop several satellite components, and sometimes it is very difficult to obtain FE-Model. In this case, FE-Model reduction using superelement method can be good solution. For developing satellite, antenna manufacturer required satellite FE-Model to calculate microvibration induced by antenna operation, and condensed model using superelement method was provided. Superelement method is based on Craig-Bampton method, and it is applied to spacecraft FE-Model reduction in this paper. From modal analysis and the frequency response analysis results between full FE-Model and condensed model, the usefulness of reduced model is confirmed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.151-160
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• 2006

In this study, we propose a new efficient 2-noded hybrid-mixed element for curved beam vibrationshaving a uniform and non-uniform cross section. The present element considering transverse shear strain is based on Hellinger-Reissner variational principle and introduces additional nodeless degrees for displacement field interpolation in order to enhance the numerical performance. The stress parameters are eliminated by the stationary condition and then the nodeless degrees are condensed out by the Guyan reduction. In the performance evaluation process of the present field-consistent higher-order element, we carefully examine the effects of field consistency and the role of higher-order interpolation functions on the hybrid-mixed formulation. Several benchmark tests confirm e superior behavior of the present hybrid-mixed element for curved beam vibrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.238-243
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• 1994

본 논문에서는 여러가지 형태의 결합부에 적용할 수 있는 일반적인 모델링 기법에 대하여 기술하였다. 기존의 해석방법은 특정한 결합부에만 적용이 가능하고 유한요소해석과 실험이 상호 보완적인 관계를 가진 형태의 해석방법이므로 실험이 불가능한 경우에 대해서는 적용하기 어려운 경우도 있다. 본 논문에서는 별도의 실험을 수행하지 않고 결합부 영역만을 상세하게 유한요소 모델링을 하여서 선택된 자유도에 대한 유연성 행렬(Flexibility Matrix)을 구하여 결합부의 특성을 구하는 일반적 모델링 기법을 제시하였다. 이 방법은 수치적으로 축약할 수 없는 모델-결합부가 접촉면(Contact Surface)을 가지고 있는 구조물을 효과적으로 축약할 수 있는 장점이 있다. 또한 모델링되는 결합부의 경계조건의 영향을 배제할 수 있으며 결합부에 존재하는 비선형성도 적정범위내에서 선형화할 수 있다. 제시한 일반적 모델링 기법을 나사 결합부, 접착제 결합부(Glued Joints), 볼트 결합부에 적용하여 결합부이 특성을 구하였으며 실험을 통하여 제시한 해석방법의 타당성을 검증하였다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.43 no.1 s.307
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• pp.53-66
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• 2006

This paper proposes the combined image retrieval system that gives the same relevance as exhaustive search method while its performance can be considerably improved. This system is combined with two different retrieval methods and each gives the same results that full exhaustive search method does. Both of them are two-stage method. One uses condensation of feature vectors, and the other uses binary-tree clustering. These two methods extract the candidate images that always include correct answers at the first stage, and then filter out the incorrect images at the second stage. Inasmuch as these methods use equal algorithm, they can get the same result as full exhaustive search. The first method condenses the dimension of feature vectors, and it uses these condensed feature vectors to compute similarity of query and images in database. It can be found that there is an optimal condensation ratio which minimizes the overall retrieval time. The optimal ratio is applied to first stage of this method. Binary-tree clustering method, searching with recursive 2-means clustering, classifies each cluster dynamically with the same radius. For preserving relevance, its range of query has to be compensated at first stage. After candidate clusters were selected, final results are retrieved by computing similarities again at second stage. The proposed method is combined with above two methods. Because they are not dependent on each other, combined retrieval system can make a remarkable progress in performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.837-842
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• 2009

The efficient dynamic modeling of a satellite with flexible solar arrays is established by using the component mode synthesis technique. A flexible satellite model can be defined as the assembly of two sub-structures, central body and solar array. The reduced models of each substructure, which are expressed in each local frame, are coupled with respect to the satellite reference frame. The dynamic modeling method is applied to the numerical example of a satellite with a single solar array, and is verified by investigating the transfer function results with considering the solar array rotation.