• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1542-1547
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• 2007

Laser surface treatment technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for mold parts. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface treatment for the case of SKD61 steel and SCM4 steel. From the results of the experiments, it has been shown that the maximum average hardness is approximatly 700${\sim}$780 Hv when the power, focal position and the travel of laser are 1,095 W, 0mm and 0.3 m/min, respectively. In samples treated with lower scanning speeds, some small carbide particles appear in the interdendritic regions. This region contains fine martensite and carbide in proportions which depend on the local thermal cycle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.312-315
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• 2004

A lubricated state of an automobile transmission can not be inspected directly with eyes. Thus, it needs to develop a more general method. Wear debris can be collected from the lubricants of operating transmission of an automobile and its morphology is directly related to the fiction condition of the interacting materials from which the wear particles originated in lubricated transmission. In this paper, to identify the friction condition for transmission gear by neural network, the wear test of ball-on-disk type and the analysis of friction state were carried out for carburized SCM420 and nitrocarburized NT100 under different experimental conditions. The four shape parameters($50\%$ volumetric diameter, aspect, roundness and reflectivity) of wear debris were calculated by the image processing system. They were used as input values to identify the moving condition of transmission gear by the neural network.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.4
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• pp.133-141
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• 2001

Rapid development in computer and network technology these days has created in environment in which decisions for manufacturing companies can be made in a much broader perspective. Especially, better decisions on production and distribution planning(PDP) problems can be made laking advantage of real time information from all the parties concerned. However, since the PDP problem-a core part of the supply chain management- is known to be the so-called NP-hard problem, so heuristic methods are dominantly used to find out solutions in a reasonable time. As one of those heuristic techniques, many previous studios considered genetic a1gorithms. A standard genetic a1gorithm applies rules of reproduction, gene crossover, and mutation to the pseudo-organisms so the organisms can pass along beneficial and survival-enhancing trails to a new generation. When it comes to representing a chromosome on the problem, it is hard to guarantee an evolution of solutions through classic a1gorithm operations alone, for there exists a strong epitasis among genes. To resolve this problem, we propose a hybrid genetic a1gorithm based on Silver-Meal heuristic. Using IMS-TB(Intelligent Manufacturing System Test-bed) problem sets. the good performance of the proposed a1gorithm is demonstrated.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.9
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• pp.823-834
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• 2008

Recently, interests for SRM have been increasing rapidly to automate the whole processes of supply chain from sourcing to procurement and improve the whole efficiency of supply chain by strategically managing the relationship with external partners (suppliers). The national procurement service of Korea is trying to build new paradigms by introducing SRM for improving the competitiveness of national public procurement service. For this, a new assessment model for evaluating and selecting suppliers with fairness and objectivity should be developed. In this paper, we propose a new SRM solution including a model that evaluates and grades of suppliers' capabilities of performing the contracts. We also explain the innovation of national public procurement system through this SRM solution.

• Journal of Sasang Constitutional Medicine
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• v.19 no.3
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• pp.176-187
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• 2007

1. Objectives The purpose of this research is to find out the Sasang Constitutional difference in Heart Rate Variability. 2. Methods We enrolled 8498 workers who tested for Heart Rate Variability(HRV) from September 1, 2005 to November 28, 2005 except works whose body constitusions were undetermined according to QSCCII. 3. Results & Conclusions The result of HRV of autonomic activity and stress resistance were arranged in the order of Soeumin, Soyangin and Taeumin. On the other hand Stress Index and Fatigue Index were arranged in the order of Taeumin, Soyangin and Soeumin. But autonomic balance was no significance relationship between Sasang Constitutions. This research has shown that there is a statistical significance between the HRV and Sasang Constitutions. The findings indicated that HRV could be useful mean to make a diagnosis of Sasang Constitution or apprehended Constitutional differences.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1290-1298
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• 2006

오늘날 B2B 전자상거래의 폭발적인 성장과 더불어 SCM상에서 e-Procurement의 중요성이 부각되고 있다. 그 중에서 다수의 구매자와 공급자가 참여하여 다양한 형태의 상거래를 수행하는 3자 관리 모델은 점차 시장이 확대되어 e-Procurement의 핵심요소로 여겨지고 있다. 하지만 현재의 e-Procurement의 3자 관리 모델은 방대한 제품 정보 중에서 구매자가 원하는 제품을 정확히 검색할 수 있는 기능이 미비하고 구매 물량에 따른 할인 가격과 공급자의 배송 정책을 고려한 납기일을 실시간으로 구매자에게 제공해 줄 수 있는 기능이 미흡한 실정이다. 또한 구매 프로세스의 주요 기능인 공급자의 선택에 있어 공급자에 대한 신뢰성이 결여되어 구매자의 비즈니스 요구사항을 채워주지 못하고 있다. 본 연구에서는 이러한 e-Procurement의 3자 관리 모델의 문제점을 해결하고 발전시키기 위해 (1)구매자의 제품 검색 시 시맨틱 웹을 이용한 카테고리 기반 검색 기법과 (2)비즈니스 룰과 웹서비스 기반으로 공급자의 가격 정책, 배송 정책에 따른 납기일을 고려한 검색, (3)구매자와 공급자의 단일 거래에 대한 서비스 품질을 측정하여 구매자에게 공급자의 신뢰성을 보장하는 제품 추천 e-Procurement 시스템을 제안한다.

• Polymer(Korea)
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• v.28 no.2
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• pp.149-153
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• 2004

The cesium hydrogen sulfate (CsHSO$_4$) crystal is a superprotonic conductor above 140$^{\circ}C$ and possesses protonic conductivity three to low orders of magnitude higher than that at room temperature. Recently, the possibility of it as an electrolyte material for fuel cell system draws much attention. However, its plasticity and absorption of humidity place a limitation on its application. In this study, composites consisting of CsHSO$_4$ and polyacrylonitrile were prepared, and their phase transition properties and the ionic conductivities were evaluated. When the content of CsHSO$_4$ was about 80 vol%, a mechanically strong film with the protonic conductivity of 1${\times}$10$\^$-3/ Scm$\^$-1/ were made.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.365-370
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• 2016

The study about VR (Virtual Reality) has been done from the 1960s, but technical limits and high cost made VR hard to commercialize. However, in recent, high resolution display, computing power and 3D sensing have developed and hardware has become affordable. Therefore, normal users can get high quality of immersion and interaction. However, HMD devices which offer VR environment have high latency, so it disrupts the VR environment. People are usually sensitive to relative latency over 20ms. In this paper, as adding the Electromyogram (EMG) sensors to typical IMU sensor only system, the latency reduction method is proposed. By changing software and hardware components, some cases the latency was reduced significantly. Hence, this study covers the possibility and the experimental verification about EMG sensors for reducing the latency.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.229-234
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• 2002

OFDM(Orthogonal Frequency Division Multiplexing) 전송방식은 SCM(Single Carrier Modulation)에 비해 우수한 여러 가지 장점들을 가지며, 방송시스템들 중 Eureka 147 DAB(Digital Audio Broadcasting) 시스템에 가장 먼저 채택되었다. 그러나 OFDM 신호의 높은 PAPR(Peak-to-Average Power Ratio) 특성은 D/A, A/D 변환기의 복잡도를 높이고, 고출력 증폭기의 효율성을 감소시키는 원인이 된다. 이를 개선하기 위한 방법 중에, SDT(Signal Distortion Technique)는 전송시스템의 규격 및 수신기의 변경 없이도 적용 가능하다는 장점을 갖는다. 본 논문에서는 SDT에 속하는 companding 기법을 Eureka 147 DAB 시스템에 적용하여 PAPR 개선정도에 따른 시스템의 요구 $E_2/N_0$ 및 out-of-band의 PSD 열화 정도를 분석하였으며, 이를 clipping 기법의 성능과 비교하였다. 모의실험 결과, $\mu$값이 2인 경우, companding 기법이 PAPR, $E_2/N_0$, out-of-band의 PSD 특성 모두에서 clipping 기법에 비해 우수한 성능을 나타냈다. 또한 $\mu$ 값을 고정시킨 경우, 정규화 값이 증가할수록 신호왜곡 정도가 줄어들어 $E_2/N_0$, out-of-band의 PSD 성능개선 정도는 증가하지만, 이와는 반대로 PAPR 값은 개선 정도가 줄어들었다.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.128-133
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• 2012

The present study aims to examine the influence of flame spray distance on the thermal behavior of micro-metal particles and the morphological characteristics of $Ni_{20}Cr$ layers coated on the preheated SCM415 substrates by using the conventional flame spray system. Commercially available nickel-based $Ni_{20}Cr$ particles with a mean diameter of $45{\mu}m$ were used. In addition, CFD simulations using a commercial code (FLUENT ver. 6.3.26) were conducted to estimate temperature and velocity distributions of the continuous and discrete phases before impact on the substrate. From FE-SEM images of coated layers on the substrates, it was observed that as the spray distance decreased, the metal particle morphology showed splash-like patterns and such a short stretch shape, resulting from higher particle momentums and the impact of partially melted particles. Moreover, it was found that the spray distance should be considered as one of important parameters in controlling the porosity and the adhesion strength.