• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.874-882
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• 2001

The static and fatigue tests have been carried out to verify the validity of a generalized residual strength degradation model. And a new method of parameter determination in the model is verified experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron. It is shown that the correlation between the experimental results and the theoretical prediction on the statistical distribution of fatigue life by using the proposed method is very reasonable. Furthermore, it is found that the correlation between the theoretical prediction and the experimental results of fatigue life in case of tension-tension fatigue data in composite material appears to be reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than maximum likelihood method and minimization technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1715-1724
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• 2013

The maximum lifetime data aggregation problem is to maximize the network lifetime as minimizing the transmission energy of all deployed nodes in wireless sensor networks. In this paper, we propose a simulated annealing algorithm to solve efficiently the maximum lifetime data aggregation problem on the basis of meta-heuristic approach in wireless sensor networks. In order to make a search more efficient, we propose a novel neighborhood generating method and a repair function of the proposed algorithm. We compare the performance of the proposed algorithm with other existing algorithms through some experiments in terms of the network lifetime and algorithm computation time. Experimental results show that the proposed algorithm is efficient for the maximum lifetime data aggregation problem in wireless sensor networks.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.449-450
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• 2007

오래 전 부터 영상처리와 컴퓨터 비전은 많은 분야에 응용되고 발전 되어 왔다. 그러한 기술 중에 최근 각광 받고 있는 그래프 짓(Graph cut) 알고리즘은 에너지함수를 최소화 하는 가장 강력한 최적화 기법중 하나이다. 그리고 일반적으로 Sobel, Prewitt, Roberts, Canny 에지(edge) 검출기 등은 영상처리에서 영상상의 에지를 검출하기 위해 이미 널리 사용되고 발전되어 온 기술이다. 물체에서의 윤곽만 검출하기 위해서는 우리가 원하지 않는 영상 위의 에지도 검출되기 때문에 예지 검출기만으로는 물체의 윤곽만을 검출하는 것은 불가능하다. 우리는 물체의 윤곽만 검출하기를 원하기 때문에 그래프 컷과 에지 검출기의 알고리즘을 결합하면 이러한 문제를 해결 할 수 있다는 것을 제안한다. 이 논문에서는 그래프 컷 알고리즘과 에지 검출기에 관해 간략하게 기술하고 그 결과를 보일 것이다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.8-14
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• 1998

This paper describes a novel real-time based optimal Pulse Width Modulation (PWM) method suitable for microprocessor-based PWM inverters. Optimal switching patterns minimizing the performance index corresponding to the distortion between the reference and the controlled output voltages are decided by on-line calculation using the microprocessor-implemented control system. To show the effectiveness of the proposed PWM scheme, digital simulation studies and experiments using a 16-bit single-chip microcontroller (Intel 80C196KC) are performed. The results obtained from these simulation studies and experiments show that the proposed PWM scheme has better performance than the other methods such as the natural PWM and the direct PWM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.236-244
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• 2012

The minimum energy broadcast problem is for all deployed nodes to minimize a total transmission energy for performing a broadcast operation in wireless networks. In this paper, we propose a Tabu search algorithm to solve efficiently the minimum energy broadcast problem on the basis of meta-heuristic approach in wireless sensor networks. In order to make a search more efficient, we propose a novel neighborhood generating method and a repair function of the proposed algorithm. We compare the performance of the proposed algorithm with other existing algorithms through some experiments in terms of the total transmission energy of nodes and algorithm computation time. Experimental results show that the proposed algorithm is efficient for the minimum energy broadcast problem in wireless sensor networks.

• Journal of Korean Institute of Industrial Engineers
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• v.35 no.4
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• pp.257-265
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• 2009

This paper considers the hybrid flow shop scheduling problem for the objective of minimizing the number of tardy jobs. In hybrid flow shops, each job is processed through multiple production stages in series, each of which has multiple identical parallel machines. The problem is to determine the allocation of jobs to the parallel machines at each stage as well as the sequence of the jobs assigned to each machine. Due to the complexity of the problem, we suggest search heuristics, tabu search and simulated annealing algorithms with a new method to generate neighborhood solutions. In particular, to evaluate and select neighborhood solutions, three surrogate objectives are additionally suggested because not much difference in the number of tardy jobs can be found among the neighborhoods. To test the performances of the surrogate objective based search heuristics, computational experiments were performed on a number of test instances and the results show that the surrogate objective based search heuristics were better than the original ones. Also, they gave the optimal solutions for most small-size test instances.

• Smart Media Journal
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• v.6 no.3
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• pp.9-14
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• 2017

This paper is a study on the hardware implementation of the encryption and decryption block of the lightweight block cipher algorithm LEA which can be used for tiny devices in IoT environment. It accepts all secret keys with 128 bit, 192 bit, and 256 bit sizes and aims at the integrated implementation of encryption and decryption functions. It describes design results of applying pipeline method for performance enhancement. When a decryption function is executed, round keys are used in reverse order of encryption function. An efficient hardware implementation method for minimizing performance degradation are suggested. Considering the number of rounds are 24, 28, or 32 times according to the size of secret keys, pipeline of LEA is implemented so that 4 round function operations are executed in each pipeline stage.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.715-718
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• 2014

맵리듀스(MapReduce)는 대용량 데이터의 병렬 처리에 사용되는 프로그래밍 모델이다. 데이터 큐브(data cube)는 대용량 데이터의 다차원 분석에 널리 사용되는 연산자로서, 주어진 차원 애트리뷰트들의 모든 가능한 조합에 대한 group-by 를 계산한다. 차원 애트리뷰트가 n 개일 때, 데이터 큐브는 총 $2^n$ 개의 group-by 를 계산한다. 본 논문은 맵리듀스 환경에서 데이터 큐브를 효율적으로 계산하는 방법을 제안한다. 제안 방법은 $2^n$ 개의 group-by 를 분할하고 이들을 ${\lceil}n/2{\rceil}$개의 맵리듀스 잡(job)을 통해 단계적으로 계산한다. 제안 방법은 각 맵리듀스 잡에서 맵 함수가 출력하는 중간결과의 크기를 최소화함으로써 총 계산 비용을 크게 줄인다. 실험을 통해 제안 방법은 기존 방법에 비해 데이터 큐브를 더 빠르게 계산함을 보인다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.353-353
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• 2020

기후변화에 적응하기 위해 많은 나라들이 수자원 관리 전략을 마련하고 있으며, 대체 수자원 활성화 방안에 관심을 기울이고 있다. 본 연구에서는 대체 수자원 활성화 방안 중 빗물 저류지의 용량 결정 방법을 제시하고자 한다. 빗물 저류지의 용량을 결정하기 위해 메타 휴리스틱 방법 중 하나인 입자 군집 최적화(particle swarm optimization; PSO)를 선정하였다. 이는 기존 실제 설계에 사용되고 있는 시행착오법보다 시간을 단축시킬 수 있다. 최적화 모형은 python의 pyswarm package를 이용해 구성하였다. 모형의 입력자료는 저류지 유입량과 목표 공급량, 목표 보장률이고, 목적함수는 빗물 저류지 용량의 최소화이다. 제약조건은 모의된 보장률이 목표 보장률 이상을 달성하는 것이다. 여기서, 보장률은 전체 모의 기간 중 목표 공급량을 공급한 기간의 비율이다. 제시한 방법론의 적용성을 검토하기 위해 실제 저류지가 설계된 인천의 청라지구 1공구를 선정하여 적용하였다. 최적화 모형의 입력 유입량은 SWMM으로 산정된 1995년부터 2004년까지의 유출량이며, 목표 공급량은 실제 설계에 활용된 용수 목적별 요구 수량이다. 여기서 용수 목적별 요구 수량은 대상지역의 노면 청소수, 화장실 세정수, 호수 유지수 등이다. 산정 결과 계산 시간은 약 30초 소요되며, 목표 보장률을 만족하는 저류지 용량이 결정되었다. 본 연구에 제시한 방법은 제약조건이 추가되어도 기존 시행착오법에 비해 간편함을 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3C
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• pp.141-148
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• 2010

Electrical noises like self potential, burst noises and 60-Hz electrical noises are one of the causes to reduce reliability of electrical resistivity survey. Even the PDC-R (Pseudo DC resisitivity) technique, recently developed, is suffering from the problem of low reliability due to electrical noises. That is, both DC-based and AC-based resistivity technique is subject to reliability problem due to electrical noises embedded in urban geotechnical sites. In this research, a new technique to enhance reliability of the PDC-R technique by minimizing influence of electrical noises was proposed. In addition, an automated procedure was also proposed to facilitate data analysis and interpretation of PDC-R measurements. The proposed technique is composed of two steps: 1. to extract information only related with the input current by means of multiple-filter technique, and 2. to undertake a task to sort out signal information only to show stable and reliable characteristics. This automated procedure was verified by a synthetic harmonic wave including DC shift, burst random noises and 60-Hz electrical noises. Also the procedure was applied to site investigation at urban areas for proving its feasibility and accuracy.