• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.2
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• pp.71-75
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• 2021

Despite the development of computational resources, the need to analyze models is increasing. The size of model has been increased to analyze the entire structure more accurately and precisely. As the analysis model becomes larger and more complex, the computation time increases exponentially. Various industries use many structures that have repeated patterns. We focus on these structures with repeated patterns and propose a dynamic analysis method to efficiently calculate these repeated structures. To devise an efficient method for repeated structures, the substructuring scheme and the degree of freedom-based reduction method are used in this study. We modify the existing reduction method in consideration of the characteristics of the repeating structure. In the proposed method, the entire structure was expressed as a combination of substructures, where each substructure was represented as an unit cell of repeated structures. The substructures were condensed and assembled using the substructuring scheme and the modified condensation method. Finally, numerical examples were demonstrated to verify the efficiency and accuracy of proposed method.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.61-68
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• 2007

The problem on cyclic plate load tests was analyzed by finite element method using an anisotropic hardening constitutive model. The constitutive model was coded to user subroutine in ABAQUS. Using the result of the analysis, Young's moduli corresponding to various strain levels were evaluated by a back calculation method and were very similar to those of input. On the basis of the back calculation method plate loading tests were verified. As a result, deformation moduli could be evaluated practically from cyclic plate load tests with respect site conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.715-725
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• 2002

In this study, a method to determine the deformed shape of planar cable under vertical loads was presented. To obtain the deformed shape of cable by general cable theorem, a sag at arbitrary point is usually given. However, in general cases without a given sag, the proposed method determines the deformed shape of cable based on the equations of cable theorem and geometric compatibility by iterative way. The method was also extended to slove extensible cable. It was acknowledged from numerical analysis and model tests in laboratory that the proposed method is valid lot analysis of extensible cable as well as unextensible cable.

• Proceedings of the KOR-KST Conference
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• 1999.10a
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• pp.229-234
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• 1999

본 논문은 한국도로용량편람의 신호교차로 용량분석에서 차로이용계수를 적용하는 방법을 신호교차로 용량분석의 절차와 이동류 구분 측면에서 살펴보았다. 고찰한 결과 차로이용계수의 개선방향은 다음과 같다. 첫째, v/c 비에 따라 차로이용계수를 적용함으로써, 반복계산이 불필요하게 발생한다. 따라서 편람 개정시 이러한 반복계산을 없애는 값을 산정해야 한다. 둘째, 차로이용계수는 직진 전용차로를 통과하는 직진교통량에 대해서만 적용해야 한다. 실제 현장에서 교통량 조사 상황을 고려해보면, 상당히 불합리한 값을 도출한 것이다. 따라서 차로이용계수를 적용하는 이동류를 정확히 설명하고 그 문제점을 분명히 해야 한다. 셋째, 차로이용계수는 직진 이동류에 대해서만 있다. 우리 나라 전역에 있는 소규모 교차로를 고려해 볼 때, 차로이용계수는 다양한 차로군(lane group)에 대하여 추가적으로 조사연구가 필요하다.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.955-958
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• 2001

본 논문에서는 비동기 CDMA 시스템에서 다중접속에 의한 간섭을 제거하는 역상관기 중에서 반복 연산을 사용하여 계산량을 개선한 second-order stationary 기반의 반복적 역상관기와 수렴특성에 대하여 이론적으로 분석하고 모의실험을 통하여 성능을 검증하였다. 먼저 반복적 역상관기에서 수렴특성을 결정하는 수렴 인자를 유도하고 가장 빠른 수렴 특성을 보장하는 최적의 수렴상수를 상관행렬의 최대 및 최소 고유값으로 나타낼 수 있음을 증명하였다. 또한 최적의 수렴 상수와 반복회수에 따른 BER이 기존의 역상관기와 비슷한 성능을 가짐을 보였다.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.765-768
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• 2001

본 논문에서는 터보 TCM(Turbo Trellis Coded Modulation)에서 복호기 입력 전에 수신데이터를 이용하여 SNR을 추정하고, SNR에 따라 요구하는 성능을 만족하는 반복 복호수를 적응적으로 복호기 앞단에서 미리 설정하는 반복복호 제어기법을 제안한다. 성능분석결과 최대 반복 복호를 수행했을 때와 비교하여 성능 감소 없이 평균 반복 복호수를 줄일 수 있었다. 따라서 제안구조는 터보 TCM의 복호화 과정에서 문제점 중 하나인 복호 계산량과 지연을 성능 저하 없이 효율적으로 감소시킬 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5B
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• pp.608-614
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• 2001

본 논문에서는 비동기 CDMA 시스템에서 다중 접속 간섭의 영향을 줄이기 위해 제안된 역상관기 중에서 반복연산을 사용하여 계산량을 개선한 반복적 역상관기의 수렴특성에 대하여 분석하였고 이를 모의 실험을 통하여 검증하였다. 반복적 역상관기에서 수렴특성을 결정하는 수렴 인자를 유도하였고, 가장 빠른 수렴 특성을 보장하는 최적의 수렴 상수를 상관행렬의 최대 및 최소 고유값으로 나타낼 수 있음을 증명하였다. 또한 반복 과정의 중간 결과에 대한 최대 오차 범위를 유도하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.1-10
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• 1997

Current seismic design philosophy for reinforced concrete (RC) structures on energy dissipation through large inelastic defomations. A nonlinear dynamic analysis which is used to represent this behavior is time consuming and expensive, particularly if the computations have to be repeated many times. Therefore, the selection of an efficient yet accurate alogorithm becomes important. The main objective of the present study is to propose a new technique herein called the prediction approach with siffness measure (PASM) method in the convetional direct integration methods, the triangular decomposition of matrix is required for solving equations of motion in every time step or every iteration. The PASM method uses a limited number of predetermined decomposed effective matrices obtained from stiffness states of the structure when it is deformed into the nonlinear range by statically applied cyclic loading. The method to be developed herein will reduce the overall numerical effort when compared to approaches which recompute the stiffness in each time step or iteration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.965-972
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• 2005

In this paper, we first review LDPC codes in general and a belief propagation algorithm that works in logarithm domain. LDPC codes, which is chosen for second generation digital video broadcasting standard, are required a large number of computation due to large size of coded block and iteration. Therefore, we presented two kinds of low computational algorithm for LDPC codes. First, sequential decoding with partial group is proposed. It has same H/W complexity, and fewer number of iteration's are required at same performance in comparison with conventional decoder algerian. Secondly, early detection method for reducing the computational complexity is proposed. Using a confidence criterion, some bit nodes and check node edges are detected early on during decoding. Through the simulation, we knew that the iteration number are reduced by half using subset algorithm and computational complexity of early detected method is about $50\%$ offs in case of check node update, $99\%$ offs in case of check node update compared to conventional scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.1012-1019
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• 2015

This paper shows the acceleration of iterative physical optics(IPO) for radar cross section(RCS) by using two techniques effectively. For the analysis of the multiple reflection in the cavity, IPO uses the near field method, unlike shooting and bouncing rays method which uses the geometric optics(GO). However, it is still far slower than physical optics(PO) and it is needed to accelerate the speed of IPO for practical purpose. In order to address this problem, graphic processing unit(GPU) can be applied to reduce calculation time and adaptive iterative physical optics-change rate(AIPO-CR) method is also applicable effectively to optimize iteration for acceleration of calculation.