• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.473-477
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• 2007

The development of advanced Insulated Gate Bipolar Transistor(IGBT)has enabled high-frequency switching operation and has improved the performance of PWM inverters for motor drive. However, the high rate of dv/dt of IGBT has adverse effects on motor insulation stress. In many motor drive applications, the inverter and motor are separated and it requires long motor feds. The long cable contributes high frequency ringing at the motor terminal and it results in hight surge voltage which stresses the motor insulation. The inverter output filter and RDC snubber are conventional method which can reduce the surge voltage. In this paper, we propose the new low loss snubber to reduce the motor terminal surge voltage. The snubber consists of the series connection of charging/discharging capacitor and the voltage-clamped capacitor. At IGBT turn-off, the snubber starts to operate when the IGBT voltage reaches the voltage-clamped level. Since dv/dt is decreased by snubber operating, the peak level of the surge voltage can be reduced. Also the snubber operates at the IGBT voltage above the voltage-clamped level, the snubber loss is largely reduced comparing with RDC snubber. The proposed snubber enables to reduce the motor terminal surge voltage with low loss.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.23-30
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• 2019

Automobiles are largely divided into passenger cars with less than five passengers and commercial vehicles such as construction machines, trucks, mixers, special lorries, and large buses. Automobile maintenance companies are also divided into passenger cars and commercial vehicles. Because commercial vehicles are the livelihood vehicles of individual carriers engaged in cargo transportation, passenger transportation, and construction, fast and accurate maintenance is important. Access to the expressway is also important because the car is large and uses highways. In addition, the time required for troubleshooting is long, so sufficient space must be secured for parking the vehicle, and ease of entry and exit of the vehicle in the maintenance shop should be fully considered. For this reason, commercial vehicle maintenance companies have higher initial investment costs than car maintenance companies, and it is difficult to supply and maintain maintenance personnel. Therefore, it is necessary to carefully examine and analyze various related factors for successful commercial vehicle maintenance company selection. However, most existing commercial vehicle maintenance companies often choose their location based on the empirical judgment of the founder, the customs and the case, without a clear analysis. In this study, we show how to derive the location selection factors to be considered when establishing professional maintenance company for commercial vehicles and to select the optimal location by using AHP (Analytic Hierarchy Process) method.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.520-527
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• 2005

In order to investigate the geochemical characteristics of surface sediments in streams of upper Yeongsan River drainage system, sediment samples from the main stream of Yeongsan river, Hwangryong river, Gwangju and Jiseok streams were collected and analyzed for grain size and metal and organic carbon contents. The metal contents in the sediments are mainly dependent on organic matter contents in the domestic sewage, grain size of the sediments and geology around the streams. Enrichment factor (EF) and index of geoaccumulation (Igeo) representing the degree of metal contamination in the sediments are relatively low in the main stream of Yeongsan river main stream, Hwangryong river and Jiseok stream. However, those of Gwangju stream show the EF maximum values of P=8.30, Cu=5.55, Zn=14.29 and Pb=7.45 and the Igeo maximum values of P=3.58, Cu=4.43, Zn=3.22 and Pb=1.59.

• 한국HCI학회:학술대회논문집
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• 2007.02b
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• pp.48-54
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• 2007

컴퓨터 네트워크의 발달로 인터넷이 실생활이 되면서, 온라인에서 인스턴트 메신저를 이용한 커뮤니케이션 방식이 확대되고 있다. 이러한 메신저에서는 이모티콘 및 플래시콘 혹은 윙크 등 과 같은 다양한 방식을 통해 감정을 표현할 수 있도록 제안하고 있다. 하지만, 아직까지 온라인의 감정표현은 흥미위주이며, 오프라인의 다양한 감정표현에 비해서 제한적이다 따라서 오프라인에서의 다양한 사용자 감정표현을 온라인에서 표현해 줄 수 있는 새로운 형태의 감성 커뮤니케이션 방법이 필요하다. 본 연구에서는 온라인 인스턴트 메신저의 사용행태 이해를 통해서 사용자들의 요구사항을 파악하고 이를 통해 제안할 수 있는 커뮤니케이션 방법을 모색하고자 한다. 실생활에서 사용자의 감정표현 방법을 바탕으로 온라인 메신저에 적용하여 새로운 감성 커뮤니케이션 방법을 제안하는 연구로, 감정어휘와 표현방법의 사용자 조사를 통해 감정표현 방법에 대한 컨셉을 제안하였다. 우선 메신저 사용 행태와 요구사항 도출을 위한 사용자 FGI를 진행하였다. 사용자 FGI로 얻어진 사용자들의 메신저 사용행태를 통해, 텍스트와 모션을 활용하는 '텍스트콘'을 컨셉 아이디어로 도출하였다. 아이디어에 적용하기 위해 모션을 감정으로 인해 파생되는 행동과 체감각 요소로 구분하였다. 구체적인 표현방법 및 적용 요소를 추출하기 위한 방법으로 온라인 설문조사를 실시하였으며 감정어휘와 표현방법(행동, 체감각)을 추출하였다. 추출된 내용은 '사용자 참여 관찰' 기법을 활용하여, 사용어휘와 행동을 정리하고 구제화하여 그 결과를 '텍스트콘'에 적용하였다. 본 연구는 사용자들이 메신저를 이용한 감정표현에 있어 텍스트를 선호하고 텍스트에 대한 요구사형에 있음을 확인하였으며, 감정표현 컨셉 아이디어 '텍스트콘'을 도출하였다. '사용자 참여 관찰' 기법을 활용하여 기존의 이모티콘으로 대표되는 그래픽 아이콘 중심의 사용자 감정표현 방법을 보조해줄 수 있는 방법으로 실생활에서 사용자가 표현하고 받아들이는 신체언와 행동을 적용하였다는 것에 그 의의가 있다. 또한, 감정에 의한 생리적 반응 요소를 외적인 반응과 내적인 반응으로 구분하여, '체감각'이라고 하는 내적반응을 중심표현방법으로 삼아, 기존과는 다른 시각으로 접근할 수 있었다.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.764-773
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• 2004

The soil in wildfire area Sacheon-myeon, Gangneung, Gangweon Province, Korea, were investigated to clarify pattern of the soils. The soils were classified into 5 types on the basis of vegetation, types of organic matter. thickness of soil horizons, and completeness of soil profile. Each type showed different erosion pattern and Landsat ETM image. Coverage of plant leaves, litter, root, ash and other organic matter was an important component that affected soil color and reflectance of Landsat image (digital number). Although the NDVI (Normalized Distribution Vegetation Index) method in the wildfire area did not show much difference in soil types, the applied supervised classification method showed characteristic pattern of Landsat ETM image of soil types. This study showed that the applied supervised Landsat TM image classification in wildfire area is an effective way to estimate the distribution of erosion pattern of soil in wildfire area.

• Journal of the Korean Home Economics Association
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• v.44 no.10
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• pp.57-66
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• 2006

The purpose of this study was to evaluate the relationship between the tactile sensation and mechanical properties of towel. Six kinds of towels with different surface structure and fiber composition were used for this study. To evaluate the tactility of towel, 36 adjectives were collected and then 11 adjectives were selected. The subjective evaluation was examined by one to one comparative method and by blind test for estimating the only the sense of touch of the towels. Kawabata's Evaluation system for fabrics was used to measure the mechanical properties which are tensile, bending, shear, compression, surface, weight, and thickness of six towels. The results are as follows; First, surface structure of the towels had an effect on estimation the sense of touch. Pile surface was evaluated thicker, compacter, more cushiony, and more elastic. Waffle surface was evaluated knottier and rougher, and microfiber suede surface was evaluated softer and denser. Second, the highest value of the mechanical properties measured were G, 2HG, B, and SMD of 100% cotton 100% pile, WC, T, and W of elban loop pile, WT, 2HB, and LC of 100% cotton cut pile, RT and MIU of microfiber suede, and RC of microfiber waffle. Third, the 11 adjectives were correlated with more than one mechanical property. 'Knotty' and 'rough' were correlated with MMD and SMD, 'soft' were correlated with B, 2HB, MMD, and SMD. 'Thick', 'heavy', 'compact', and 'elastic' were correlated with WC, T, and W, 'cushiony' was correlated with WC. 'Stiff' was correlated with B and 2HB, 'dry out' was correlated with RT, WC, MIU, and T. 'Dense' was correlated with RT and SMD.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.764-769
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• 2004

The DC Motor in a vehicle may cause noise and vibration because of high speed revolution, which can make a driver feel uncomfortable. There have been various studies attempting to solve these problems, focusing mostly on the causes of and ways to reduce noise and vibration. It is suggested that the noise in a DC Motor may be primarily due to interaction between a brush and a commutator. Brush noise, the most common noise in a DC Motor, results from a brush bounced from the surface of the commutator, fluctuation of the friction between the brush and the commutator, and the impact on the brush when passing over slots of the commutator. Based on the noise test, one of the most important design parameters was shown to be the roundness of the commutator. As the DC motor is used, the roundness of the commutator gets bigger with subsequent increase of the level of brush noise and vibration. There must be a threshold in order to prevent the brush noise from getting worse. Using the method of CAE is more efficient than the real test for purposes of looking for various design parameters to maintain the roundness of the commutator. In this study, the design process to reduce the brush noise is presented with the use of a computer model. The design parameters to reduce the brush noise and vibration are proposed by using FEM. The design parameters are used to reduce the noise and vibration of a DC motor and it is verified with the test results on a fan DC motor in a vehicle. This method may be applicable to various DC motors.

• Journal of IKEEE
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• v.22 no.3
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• pp.754-758
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• 2018

Analysis methods in the power system are static analysis, dynamic analysis and online analysis, offline analysis. The static analysis is used for the existing power system analysis method and the static analysis is mainly used for PSS / E. However, in the real system where the value changes in real time which we are using, dynamic analysis is required which can be analyzed in real time for accurate analysis. Therefore, attention is focused on EMS (Energy Management System) and importance is increasing. Among the various EMS systems, we will cover state estimation, which is a static on-line analysis that can receive and interpret data from the acquisition point in real time. DC systems are spreading in various fields such as DC load, DC distribution, renewable energy. As such, much attention and attention are focused on the DC system. In this paper, we have studied the feasibility through the case study and the interpretation of the state estimation that can be applied to the DC system.

• 한국HCI학회:학술대회논문집
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• 2006.02b
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• pp.727-732
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• 2006

국내 홈 네트워크 시장은 여러 업체가 컨소시엄을 구성하여 시범지역을 확대하는 등 점차 보편화 되어가고 그 응용 범위를 확대해 나가는 단계에 있다. 하지만 홈 네트워크 시장의 서비스 및 제품들을 사용하는 사용자들이나 기획 / 개발하는 개발자들이 실제로 체감하는 홈 네트워크 시장의 활성화 정도는 아직 부족한 면이 있다. 홈 네트워크 시장의 활성화 정도가 부족한 원인에는 여러 가지 문제점들이 있지만 그러한 문제점 가운데에는 홈 네트워크 시장의 주 구성원인 사용자와 개발자가 가지고 있는 문제점에 대한 서로간의 관점 차이로 인한 부분도 있을 것이다. 본 연구에서는 홈 네트워크 제품 및 서비스 사용자와 개발자 인터뷰를 통해 문제점을 조사하고 이에 대한 관점의 차이를 분석하고자 하였다. 구체적 문제점 파악을 위해 개발자 관점에서의 개발 프로세스는 '기획, 개발, 판매, 유지보수'의 단계로, 사용자 관점에서의 사용 프로세스는 '구매, 설치, 사용, 이전, AS, 폐기'의 단계로 구분하여 조사하였다. 문제점의 비교를 위해 개발 프로세스와 사용 프로세스를 하나의 제품 및 서비스 라이프사이클로 통합 정의하였고, '판매, 유지보수 / 구매, 설치, 사용, 이전, AS, 폐기' 단계에서 공통된 영역을 찾을 수 있었다. 이 영역에서 사용자와 개발자의 문제점 비교를 통해 두 그룹간의 관점의 차이를 도출하여 각 단계별 홈 네트워크 문제점에 대한 관점의 차이를 확인할 수 있었다.

• Journal of Acupuncture Research
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• v.32 no.3
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• pp.135-146
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• 2015

Objectives : This study was designed to evaluate clinical evidence of moxibustion treatment for knee pain. Methods : All processes were independently carried out by three investigators. A literature search was performed in 3 databases from their inception to May 2015. Ten reports were found based on their title, abstract and text. Following this, data extraction and analysis were done using a risk of bias(ROB) and through an assessment of multiple systematic reviews(AMSTAR). Results : 10 studies(6RCT, 2SR, 2CR) were included. Generally, indirect moxibustion was used for knee pain, but only one study indicated the use of direct moxibustion. Moxibustion was shown to be effective in treating knee pain, and the number of required treatments was fourteen on average. In assessing risk of bias, indefinite and uncertain information made all included trials subject to a high risk of bias. On the other hand, SR showed all evaluation items in the assessment of multiple systematic reviews, with the exception of an included or excluded studies list. Conclusions : Because of deficient study design or limited research planning, there is not sufficient evidence to allow for any conclusion about the efficacy of moxibustion for knee pain. Therefore, well-designed high quality trials are needed from now on.