• Steel and Composite Structures
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• 제9권6호
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• pp.535-555
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• 2009

The harmony search method based optimum design algorithm is presented for geometrically non-linear semi-rigid steel frames. Harmony search method is recently developed metaheuristic algorithm which simulates the process of producing a musical performance. The optimum design algorithm aims at obtaining minimum weight steel frames by selecting from standard set of steel sections such as European wide flange beams (HE sections). Strength constraints of Turkish Building Code for Steel Structures (TS648) specification and displacement constraints were used in the optimum design formulation. The optimum design algorithm takes into account both the geometric non-linearity of the frame members and the semi-rigid behaviour of the beam-to-column connections. The Frye-Morris polynomial model is used to calculate the moment-rotation relation of beam-to-column connections. The robustness of harmony search algorithm, in comparison with genetic algorithms, is verified with two benchmark examples. The comparisons revealed that the harmony search algorithm yielded not only minimum weight steel frames but also required less computational effort for the presented examples.

• 소성∙가공
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• 제6권5호
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• pp.416-424
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• 1997

In the present study, a contact search and check algorithm for general tool surface described by triangular FE patch is proposed. To improve numerical stability, SEAM element using the linear Coons interpolation has been used. To check the proposed algorithm, both clover cup and L-shape cup deep drawing processes are calculated. The computed results shows that the proposed contact algorithm can be successfully applied for sheet metal forming processes with general shaped tools.

• Journal of Advanced Marine Engineering and Technology
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• 제40권2호
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• pp.138-145
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• 2016

This paper proposes an improved tabu search method for subset selection in multiple linear regression models. Variable selection is a vital combinatorial optimization problem in multivariate statistics. The selection of the optimal subset of variables is necessary in order to reliably construct a multiple linear regression model. Its applications widely range from machine learning, timeseries prediction, and multi-class classification to noise detection. Since this problem has NP-complete nature, it becomes more difficult to find the optimal solution as the number of variables increases. Two typical metaheuristic methods have been developed to tackle the problem: the tabu search algorithm and hybrid genetic and simulated annealing algorithm. However, these two methods have shortcomings. The tabu search method requires a large amount of computing time, and the hybrid algorithm produces a less accurate solution. To overcome the shortcomings of these methods, we propose an improved tabu search algorithm to reduce moves of the neighborhood and to adopt an effective move search strategy. To evaluate the performance of the proposed method, comparative studies are performed on small literature data sets and on large simulation data sets. Computational results show that the proposed method outperforms two metaheuristic methods in terms of the computing time and solution quality.

• 한국항행학회논문지
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• 제12권2호
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• pp.146-153
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• 2008

UWB(Ultra Wide-Band)통신 기술은 매우 짧은 펄스를 사용하기에 정밀한 동기 획득 제어가 필요하다. 고속 W-PAN 응용이나 저속 무선측위 응용 모두를 위해 정확한 UWB 신호의 동기 획득(Signal Acquisition)은 매우 중요하다. 본 논문에서는 UWB 다중경로 채널 환경에서 동기 획득을 위해 두 단계 신호 탐색기법을 이용하여 동기 획득 알고리즘을 제안한다. 첫 번째 단계는 수신된 신호전체 시간을 두고 탐색 구간을 절반으로 나눠 각각 나눠진 창의 전력 값의 합을 비교하여 더 큰 전력 값을 가지는 구간을 다음 탐색 창으로 잡는다. 이러한 과정을 반복하여 다음 탐색 창을 구한다. 비교된 값이 임계값을 넘을 때까지 탐색을 반복한다. 두 번째 단계에서는 첫 번째 단계에서의 구해진 탐색 창을 Fine Search 하기 위하여 Linear 탐색 알고리즘을 적용하여 검색한다. 이 제안 알고리즘을 UWB 다중경로 채널 환경에서 모의실험 결과 병렬 탐색 알고리즘에 비해 고속 동기 획득이 가능하고 SNR의 변화가 심한 환경에 적합한 특성을 확인하였다.

• 한국통신학회논문지
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• 제29권12C호
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• pp.1623-1632
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• 2004

본 논문에서는 전형적인 실내 무선 채널 환경에서 초광대역 (Ultra Wide Band; UWB) 신호의 고속 동기 획득을 위한 Single-Dwell 연속 통기 탐색 기반의 Linear 탐색 알고리즘 및 Bit Reversal 탐색 알고리즘에 대한 성능분석을 수행하였다. IEEE 802.15 Task Group 3a UWB 실내 무선 채널 환경에서 프레임 구간 및 탐색 단위 구간 등의 변화에 따른 모의실험 결과. Linear 탐색 알고리즘보다 Bit Reversal 탐색 알고리즘이 정규화된 평균 동기 획득 소요 시간에 대해 단연 우수함을 확인하였으며, 탐색 종료 구간의 범위 변화에 따른 정규화된 평균 동기 획득 소요 시간이 이상적인 경우와 거의 일치함을 확인하였다. 특히, Bit Reversal 탐색 알고리즘의 경우 탐색 단위 구간이 세밀할수록 동일한 소요 시간에 대해 더욱 정확한 동기 획득 성능을 얻음을 확인할 수 있었다.

• 전기학회논문지P
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• 제65권4호
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• pp.292-297
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• 2016

The first-order plus dead time(FOPDT) and second-order plus dead time(SOPDT), which describes a linear monotonic process quite well in most chemical and industrial processes and is often sufficient for PID and IMC controller tuning. This paper presents an application of heuristic harmony search(HS) optimization algorithm to the identification of linear continuous time-delay systems from step response. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. The effectiveness of the proposed identification method has been demonstrated through a number of simulation examples.

• Advances in Energy Research
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• 제4권4호
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• pp.255-274
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• 2016

This paper presents a novel symbiotic organisms search (SOS) algorithm to optimize both real power loss (RPL) and voltage stability limit (VSL) of a transmission network by controlling the variables such as unified power flow controller (UPFC) location, UPFC series injected voltage magnitude and phase angle and transformer taps simultaneously. Mathematically, this issue can be formulated as nonlinear equality and inequality constrained multi objective, multi variable optimization problem with a fitness function integrating both RPL and VSL. The symbiotic organisms search (SOS) algorithm is a nature inspired optimization method based on the biological interactions between the organisms in ecosystem. The advantage of SOS algorithm is that it requires a few control parameters compared to other meta-heuristic algorithms. The proposed SOS algorithm is applied for solving optimum control variables for both single objective and multi-objective optimization problems and tested on New England 39 bus test system. In the single objective optimization problem only RPL minimization is considered. The simulation results of the proposed algorithm have been compared with the results of the algorithms like interior point successive linear programming (IPSLP) and bacteria foraging algorithm (BFA) reported in the literature. The comparison results confirm the efficacy and superiority of the proposed method in optimizing both single and multi objective problems.

• East Asian mathematical journal
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• 제35권5호
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• pp.597-612
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• 2019

In this study, we propose a new logarithmic barrier approach to solve linear programming problem using the projective method of Karmarkar. We are interested in computation of the direction by Newton's method and of the step-size using minorant functions instead of line search methods in order to reduce the computation cost. Our new approach is even more beneficial than classical line search methods. We reinforce our purpose by many interesting numerical simulations proved the effectiveness of the algorithm developed in this work.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1281-1286
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• 2003

A line search algorithm to increase a convergence in Newton's method is developed and applied to nonlinear finite element analysis. The algorithm is based on the slack line search theory which is an efficient algorithm to determine initial acceleration coefficient, variable backtracking algorithm proposed by some researchers, and convergence criterion based on residual norm. Also, it is capable of avoiding exceptional diverging conditions. Developed program is tested in metal forming simulation such as forging and ring rolling. Numerical result shows the validity of the algorithm for a highly nonlinear system .

• 한국항행학회논문지
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• 제19권6호
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• pp.636-642
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• 2015

본 논문에서는 계단응답으로부터 시 지연을 갖는 선형 연속시스템을 식별하기 위해 HS 최적화 알고리즘을 적용에 관하여 연구하였다. 인식 모델은 1차 시 지연 모델 (FOPDT)로써, FOPDT은 많은 화학 공정과 HAVC 공정에 실효성이 있으며 PID 튜닝에도 적합하다. 최근에 개발된 HS 알고리즘은 완벽한 하모니를 찾아가는 음악적 과정을 개념화 한 것이다. 수학을 기반으로 하는 전통적 기법과 달리 HS는 확률적인 방법을 사용하므로 미분과 같은 수학적 접근을 필요로 하지 않는다. 제시된 인식 방법의 효과를 입증하기 위해 많은 수치 예를 수행하여 결과를 제시하였다.