• 한국레이저가공학회지
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• 제4권1호
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• pp.21-28
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• 2001

Simulation on the electron beam welding of Al 2219 alloy was carried out by using commercial FEM code MARC, which encounters moving heat sources. Due to axisymmetry of geometry, a half of the cylinder was simulated. A coupled thermo-mechanical analysis was carried out and subroutine for heat flux was substituted in the program. The material properties such as specific heat, heat transfer coefficient and thermal expansion coefficient were given as a function of temperature and the latent heat associated with a given temperature range is considered. As a result, the proper beam power is 60㎸${\times}$60㎃ and welding speed is 1∼1.5 m/min. The residual stress in the heat-affected zone as well as the fusion zone does not increase. It is necessary to use jigs for preventing distortion of cylinder and improving weld quality.

• Journal of Welding and Joining
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• 제30권2호
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• pp.70-75
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• 2012

In this study, effect of nitrogen volume in the shielding gas of Ar-$N_2$ mixing gas on the bead shape, hardness and microstructure of GTA welds of 3mm thick Commercial Pure Ti was investigated. As the nitrogen volume increased, the welding current for full penetration was reduced and hardness in the fusion zone significantly increased compared with that of the base metal, but there is no difference in the hardness of HAZ. Microstructure in the fusion zone with pure Ar gas changed from equiaxed alpha of the base metal to serrated alpha. On the other hand, microstructure using Ar-$N_2$ mixing gas changed to acicular alpha. With the increasing of nitrogen content, the amount of acicular alpha increased and the size of that was fine.

• 전기학회논문지
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• 제57권11호
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• pp.2047-2053
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• 2008

Auto-ID industries and their services have been improved since decades ago, and radio frequency identification (RFID) has been contributing in many applications. Product management can be the foremost example. In our industrial experiences, RFID in ultra high frequency (UHF) band provides much longer interrogation ranges than that of 13.56MHz; many more applications exist thereby. There should be several interesting and useful ideas on UHF RFID; however, those ideas can be limited due to the inevitable environmental circumstances that restrict the interrogation range in shorten value. This paper discusses the propagation interference among different types of readers (e.g, mobile RFID readers in stationary reader zone) in dense-reader environment. In most cases, UHF RFIDs in Korea will be dependent on the UHF mobile RFIDs. In this sense, the UHF mobile users accidently move into the stationary reader's interrogation zone. This is serious problem. In this paper, we analyze propagation loss and propose the effective channel allocation scheme that can contribute developing less-invasive UHF RFID networks. The simulation and practical measurement process using the commercial CAD tools and measurement equipments are presented.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.111.1-111.1
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• 2011

The solar energy is dramatically increasing as the alternative energy source and the silicon(Si) solar cell are used the most. In this study, the improved process and equipment for the metallurgical refinement of multicrystalline Si were evaluated for the inexpensive solar cell. The planar plane and columnar dendrite aheadof the liquid-solid interface position caused the superior segregation of impurities from the Si. The solidification rate and thermal gradient determined the shape of dendrite in solidified Si matrix solidified by the directional solidification(DS) method. To simulate this equipment, the commercial software, PROCAST, was used to solve the solidification rate and thermal gradient. Si was vertically solidified by the DS system with Stober process and up-graded metallurgical grade or metallurgical grade Si was used as the feedstock. The inductively coupled plasma mass spectrometry (ICP) was used to measure the concentration of impurities in the refined Si ingot. According to the result of ICP and simulation, the high thermal gradient between the two phases wasable to increase the solidification rate under the identical level of refinement. Also, the separating heating zone equipped with the melting and solidification zone was effective to maintain the high thermal gradient during the solidification.

• 도시과학
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• 제9권1호
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• pp.17-31
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• 2020

This study aims to analyze the relations among greenbelt, urban land surface temperature empirically in order to assess the environmental effects of the greenbelt in the Seoul metropolitan area, objectively. For this purpose, this study conducts an empirical analysis of impacts of greenbelt on urban land surface temperature using a multiple-regression model. The main data employed in the analysis include real-time air pollution data, Landsat 8-OLI Landsat imagery data, KLIS data and Jip-gye-gu data. The major findings are summarized as follows. NDVI has a negative (-) correlation with the land surface temperature, and the urban temperature is high in areas with poor vegetation. The land surface temperature is low in residential or commercial areas, while the temperature is high in industrial areas. The temperature is low in green fields, open spaces, and river areas. it is found that the urban land surface temperature is low in the greenbelt zone. In the greenbelt zone, there is an effect that reduces the land surface temperature by 1% on average, as compared to that at the center of the Seoul metropolitan area. Especially, the center of the Seoul metropolitan area, in a range from 0.6% to 1.9% of the average temperature, the temperature gets lower up to approximately 3km from the greenbelt boundary.

• 농촌계획
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• 제3권2호
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• pp.71-80
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• 1997

The city's countryside is adjusting to change by urbanization. The recent changes in rural landuse and damages of local landscape characteristics are very serious. But, few studies address the relationship between land-use and quality of landscape for these area. The aim of this study is to clarify causes and problems of the change through investigating changes of landscape as a function of land-use. The results are as follows 1) The change of landscape can be seen as a functional of land-use. Landscapes are characterized by changes of regional environments. These are the urban-rural fringe area which need special consideration for urban development and also for rural landscape quality. 2) 11 types of landscape patterns are found for landscape management. these are Regional commercial area, Apartment development, Recreation & seisure, Golfs, Housing complex, Industrial complex, Vinyl house, Rural village, Evaded facilities, Rivers, Cultural heritages. These landscape types are explained as 'stimuli-responses model'in Bryant's Forces of urbanization. 3) The policy implications of these study are as follows : First is the necessity of landscape management in Grown Management Zone and Natural Reserved Zone in the Metropolitan level, Second is the necessity of development control in semi- agricultural area. The last is the necessary of long range management plan in the urban-rural fringe area.

• 한국ITS학회 논문지
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• 제9권1호
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• pp.55-68
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• 2010

IEEE WAVE는 고속 이동 중인 차량 네트워크에서 운전자 안전 정보 및 상업적 서비스를 제공하기 위한 무선 전송 기술로써 현재 표준화가 활발히 진행 중이다. 본 논문에서는 IEEE WAVE를 기반으로 하는 안전운전 지원 서비스를 위한 응용계층 프로토콜과 이를 기반으로 하는 응용 시스템을 소개한다. 본 논문에서 다루는 안전운전 지원 서비스로는 공사구간 정보 서비스 및 사고차량 신고 서비스, 응급차량 알림 서비스, 프로브 서비스, 딜레마구간 의사결정 지원 서비스를 포함한다. 시스템의 기능 검증을 위하여 에뮬레이터 시스템을 구현하였으며 에뮬레이터는 차량과 도로의 모든 상황을 관리하는 에뮬레이터 서버와 각각의 기능 개체(차량 및 노변, 교통 센터)를 포함하는 클라이언트로 구성된다.

• 대한의생명과학회지
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• 제17권1호
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• pp.21-25
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• 2011

We have analyzed 11 different commercial brands provided by Daboo Culture and Art Center. This study was carried out to determine the antibacterial activity of water extract from puer tea ingredients against Staphylococcus aureus (S. aureus) and Listeria monocytogenes (L. monocytogenes). Antibacterial activity of the water extracts was shown against S. aureus and L. monocytogenes by paper disc method. In case of S. aureus, antibacterial activity of the extracts appeared as clear inhibitory zone. This antibacterial activity was greater along with pH and showed the highest effect at pH 10. In case of L. monocytogenes, antibacterial activity of the extract appeared as clear inhibitory zone. Some Puer tea appeared to be more powerful in antibacterial activity against S. aureus and L. monocytogenes. The polyphenol compounds were 3.46~8.68%, depending upon samples. In conclusion, puer tea is considered as a good choice for well-being food.

• 대한교통학회지
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• 제26권4호
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• pp.265-273
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• 2008

영상기반 교통감지시스템은 교통정보 수집을 기본으로 상충, 사고감지, 기후감지 등 다양한 정보를 수집하는 데 이용되고 있다. 본 논문은 VDS에서 검지영역을 설정할 때 단위거리별 픽셀길이를 자동 계산하여, 이를 기반으로 교통정보 및 상충정보를 수집하는 시스템을 개발한다. 본 알고리즘은 교차로에 검지영역 내 검지라인을 세분화하여 설정함으로써 교통정보의 정확도를 높이고, 개별차량의 교차로 통과속도 및 점유율을 자동으로 계산해 주며, 나아가 모든 교차로에 일반화하여 적용할 수 있다. 본 알고리즘은 분당교차로에 설치된 CCTV영상을 대상으로 실험하였으며, 상용화 제품과의 교통정보 비교분석을 통하여 알고리즘을 검증하였다.

• 열처리공학회지
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• 제3권2호
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• pp.32-36
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• 1990

For the accurate measurements of hardness in a material, it is necessary to have a thorough understanding of the effects of test variables on the accuracy of hardness value. For the rebound hardness test, major test variables are the radius of hammer ball tip, type of backing materials, size and roughness of the specimen. In this study, effects of these variables on Equo-Tip hardness value were investigated. Hardness measurements were carried out using WC balls with various sizes of worn-ot zone. The sample materials chosen for the experiments were commercial standard hardness blocks and SM45C steel bars subjected to either normalization or quench and temper treatments. As backing materials, aluminum, steel and rubber plates were used in all the experiments. Experimental results show that for the accurate measurements of Equo-tip hardness, it is necessary to use the hammer ball with a worn-out zone parameter of less than 0.23, and the recommended minimum thickness and width of the specimen are 25mm and 70mm, respectively. Further for the surface preparation, the specimens need to be polished with an emery paper of No. 400 or finer, and for the backing matrials, it is recommended to use steels or rubbers.