• Journal of Welding and Joining
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• 제27권5호
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• pp.81-87
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• 2009

Recently, extruded aluminium-alloy panels have been used in the car bodies for the purpose of the light-weight of railway vehicles and FSW(Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. This paper presents the optimum design of the FSW process on A6005 extruded alloy for railway vehicles to improve its mechanical properties. Rotational speed, welding speed and tilting angle of the tool tip were chosen as design parameters. Three objective functions were determined; maximizing the tensile strength, minimizing the hardness and maximizing the difference between the normalized tensile strength and hardness. The tensile tests and the hardness tests for fifteen FSW experiments were carried out according to the central composite design table. Recursive model functions on three characteristic values, such as the tensile strength, the hardness difference(${\Delta}Hv$) and the difference of normalized tensile strength and ${\Delta}Hv$, were estimated according to the classical response surface analysis methodology. The reliability of each recursive function was verified by F-test using the analysis of variance table. Sensitivity analysis on each characteristic value was done. Finally, the optimum values of three design parameters were found using Sequential Quadratic Programming algorithm.

• 정보처리학회논문지D
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• 제13D권7호
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• pp.1027-1038
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• 2006

대용량 데이터베이스에서의 추천시스템은 많은 문제점들을 지니고 있으므로, 대규모 인터넷 쇼핑몰에 적합한 추천 시스템 구조와 데이터 마이닝 기법의 필요성이 요구되고 있다. 따라서 본 논문에서는 k-mean 클러스터링과 순차 패턴 기법을 이용한 VLDB(very large database) 기반의 상품 추천 시스템을 설계 및 구현한다. 본 논문에서는 사용자의 정보를 일괄처리하고 다양한 카테고리를 계층적으로 정의하며, 탐색엔진에 순차 패턴 마이닝 기법을 이용한다. 예측 모델을 만들기 위하여 사용자의 로그 데이터 중에서 카테고리에 대한 사용자의 선호도를 추출하여 이용한다. 본 논문에서는 실험과 성능 평가를 위하여 국내 인터넷 쇼핑몰에서 30일 동안 수집한 실제 데이터를 이용한다. 또한 성능평가를 위하여 추천 예측 정확율(PRP: Predictive Recommend Precision), 추천 예측 재현율(PRR: Predictive Recommend Recall), 정확도 인수(PF1 : Predictive Factor One-measure)를 제안하여 사용한다. 성능평가 결과 가장 빠른 추천시간 및 학습시간은 O(N)이었고, 다양한 실험에서의 측도들의 값이 상당히 우수하였다.

• 한국항공우주학회지
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• 제34권9호
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• pp.33-44
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• 2006

최근 공학적 설계문제들이 복잡해짐에 따라 크리깅을 이용한 근사최적화에 관한 연구가 활발하다. 따라서 본 논문에서는 개선된 확률론적 최적화 알고리즘을 제안함으로써 크리깅을 이용한 근사최적설계의 정확성과 효율성을 높이고자한다. 순차적 근사최적화 시 확률적인 설계영역으로의 이동을 위해 새로운 방법인 확률론적 국부화기법(SLM)을 제안하며, 고전적 계획법, 공간충진 계획법의 두 실험계획법을 사용함으로써 실험점 선정의 효율성을 높이고, 실험계획법의 종류에 따른 결과를 비교, 분석하였다. 또한 3부재 트러스, Sandgren의 압력용기 그리고 하니콤 인공위성 플랫폼 최적설계의 실제 공학적 문제에 적용함으로써 효율성을 검증하고자 한다.

• 설비공학논문집
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• 제12권3호
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• pp.284-291
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• 2000

A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.281-286
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• 2006

본 연구의 목적은 차세대 대체에너지로 각광받는 풍력발전 중에서 육상발전보다 여러 가지 이점이 있는 한국형 해상풍력터빈 블레이드의 최적형상설계를 위한 알고리즘을 구현하는 것이다. 블레이드 단면 익형의 양력과 항력 분포는 XFOIL을 이용하여 예측하였다. 첫 번째 수준의 설계변수인 각각의 블레이드 지름과 축 회전수에서 익형의 공력변수들과 최소에너지손실 조건을 이용하여 두 번째 설계변수인 각 블레이드 단면에서의 시위길이와 피치각 분포를 최적화하였다. 그리고 성능결과를 바탕으로 반응면을 구성하고, 확률적 방법을 이용하여 타당성 있는 설계공간까지 첫 번째 설계변수를 이동시키고 구배최적화 기법을 통해 각각의 제약함수를 만족하면서 목적함수를 죄대로 하는 최적블레이드 형상을 구현하였다. 설계된 최적형상에 대해 탈설계점 해석을 수행하여 성능을 구하였다.

• 한국통신학회논문지
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• 제21권11호
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• pp.2966-2977
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• 1996

As design of very large circuits is made possible by rapid development of VLSI technologies, efficient fault simulation is needed. Ingeneral, fault simulation requires many computer resources. As general-purpose multiprocessors become more common and affordable, these seem to be an attractive and effective alternative for fault simulation. Efficient fault simulation of synchronous sequential circuits has been reported to be attainably by using a linear iterative array model for such a circuit, and combining parallel fault simulation with russogate fault simulation. Such fault simulation algorithm is parallelized on a general-purpose multiprocessor with shard memory for acceleration of fault simulation. Through the experimenal study, the effect of the number of processors on speed-up of simulation, processor utilization, and the effect of multiprocessor hardware on simulation performance are studied. Some results for experiments with benchmark circuits are shown.

• 한국결정성장학회지
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• 제26권4호
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• pp.135-138
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• 2016

AlN 결정을 PVT(물리 기상 이동법, Physical Vapor Transport) 법으로 성장함에 있어 결정립의 성장 거동을 관찰하였다. 작은 AlN 결정립이 성장한 이후 결정립들은 이웃한 결정립과 합쳐지면서 성장하는 거동을 보였다. 이를 실체현미경을 이용하여 관찰한 결과를 보고하고자 한다.

• 대한임베디드공학회논문지
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• 제3권2호
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• pp.74-81
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• 2008

This paper describes a low-cost omnidirectional camera system designed for the intruder detection capability of a security robot. Moving targets on sequential images are detected first by an adaptive background subtraction technique, and the targets are identified as intruders if they fail to enter a password within a preset time. A warning message is then sent to the owner's mobile phone. The owner can check scene pictures posted by the system on the web. The system developed worked well in experiments including a situation when the indoor lighting was suddenly changed.

• 대한음성학회지:말소리
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• 제60호
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• pp.125-144
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• 2006

W3C announced a standard software architecture for multimodal context-aware middleware that emphasizes modularity and separates structure, contents, and presentation. We implemented a distributed multimodal interface system followed the W3C architecture, based on SCXML. SCXML uses parallel states to invoke both XHTML and VoiceXML contents as well as to gather composite or sequential multimodal inputs through man-machine interactions. We also hire Delivery Context Interface(DCI) module and an external service bundle enabling middleware to support context-awareness services for real world environments. The provision of personalized user interfaces for mobile devices is expected to be used for different devices with a wide variety of capabilities and interaction modalities. We demonstrated the implemented middleware could maintain multimodal scenarios in a clear, concise and consistent manner by some experiments.

• 품질경영학회지
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• 제48권1호
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• pp.51-68
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• 2020

Purpose: The primary objective of this research is to develop the optimal operating conditions as well as their associated design spaces for a Cryogenic Submerged Arc Welding(SAW) process by improving its quality and productivity simultaneously. Methods: In order to investigate functional relationships among quality characteristics and their associated control factors of an SAW process, a stepwise design of experiment(DoE) method is proposed in this paper. Based on the DoE results, not only a multi-dimensional design space but also a safe operating space and normal acceptable range(NAR) by integrating statistical confidence intervals were demonstrated. In addition, the optimal operating conditions within the proposed NAR can be obtained by a robust optimal design method. Results: This study provides a customized stepwise DoE method (i.e., a sequential set of DoE such as a factorial design and a central composite design) for Cryogenic SAW process and its statistical analysis results. DoE results can then provide both the main and interaction effects of input control factors and the functional relationships between the input factors and their associated output responses. Maximizing both the product quality with high impact strength and the productivity with minimum processing times simultaneously in a case study, we proposed a design space which can provide both acceptable productivity and quality levels and NARs of input control factors. In order to confirm the optimal factor settings and the proposed NARs, validation experiments were performed. Conclusion: This research may provide significant contributions and applications to many SAW problems by preparing a standardization of the functional relationship between the input factors and their associated output response. Moreover, the proposed design space based on DoE and NAR methods can simultaneously consider a number of quality characteristics including tradeoff between productivity and quality levels.