• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.258-263
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• 2003

CDMA 이동전화 서비스가 활성화되면서 유선과 무선의 경계를 허무는 대표적인 서비스로 Wireless PABX 서비스가 등장하였다. PABX(사설교환기)가 설치된 지역에서는 이동전화 단말기가 무선전화기를 대체하며 이 지역을 벗어날 경우 일반 이동전화기로 동작하는 서비스이다. SKTelecom은 Wireless PABX(이하 모바일존 서비스) 서비스를 제공하기 위해 기존의 CDMA2000 1X 시스템의 확장 시스템과, ALL-IP 시스템의 Multi-vendor 시스템을 채택하였다. 이러한 Multi-vendor 시스템의 관리와 서비스 품질관리를 위하여 SKTelecom은 고장관리시스템 구성 관리시스템, 서비스 품질감시 시스템 등의 망관리시스템을 구현하였다. 본 논문은 이동전화 서비스와 모바일존 서비스의 차이점을 분석하고, 고장/구성/품질관리 시스템을 통한 효율적인 서비스 관리방안을 제안한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.84-88
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• 1992

Laser beam hardenling of 12%-Cr steel has been evaluated by using a continuous wave 3 kW CO$\_$2/ laser with a hardening mirror set. Experiment was performed on the optimum hardening condition with a laser power of 2.85kW and travel speed of 10 and 5 m/min. Multi passes have been alsotried to find the hardening characteristics of partly overlapped zone. The black paint to use at high temperature was adopted to increases the absorptivity of laser beam energy with the wavelength of 10.6 .mu. m at the surface of bese metal. The microstructure of the hardened layers was observed by using a light microscopy. SEM and TEM. A fine lamellar martensite formed in the hardened zones exhibits very high Vickers microhardness of 600 Hv, whereas the tempered martesite distributes in the base metal with Vickers microhardness of 240 Hv. It has been found that laser hardening with multi pass showed no significant drop of the hardness between adjacent passes.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.760-765
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• 2000

The study deals with the development of a computational procedure for evaluating the temperature rise in dry and lubricated multi-layered contacts of head/disk interface. A transient computational model with a transformed rectangular computational domain is utilized. A model and a computational method for micro-contact with sub-lubricated zone, including friction heat generation, have been presented. The model was applied, taking full account of the changes in contact area and contact load due to frictional heating. The computational distribution of temperature is obtained with the analytical findings for various composition and contact conditions. Especially, a rapid rise ($220^{\circ}C$ or above) in read head temperature lese to a saturation in the influence of a thermal spike on signal performance. This general class of problems can be treated provided that heat generation distribution and layer properties are known.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.106-116
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• 1997

In this paper, using MATLAB SIMULINK, a generalized design methodology was suggested for multi pass transmission(MPT) by classifying the vehicle power train as prime mover, MPT and vehicle dynamics. This approach enables a designer to investigate the influence of each transmission component by simple combination of system components without changes of overall program. Using the design methodology, a MPT consisting of CVT, 2, clutches and reduction gears was designed for a braking energy regenerative flywheel hybrid vehicle. The CVT is essential in order to connect the engine and flywheel speed with the vehicle speed. For the purpose of smooth clutch operation, control algorithm was suggested by introducing dead zone for the clutch engagement. Using the SIMULINK model, performance of the flywheel hybrid vehicle with MPT was investigated. It was observed from the simulation results that the MPT vehicle showed better fuel economy, 47% than that of AT vehicle, 27% than that of CVT vehicle for ECE-15 driving cycle. Especially destinct fuel efficiency improvement was obtained for city driving cycle requiring more frequent stop and start.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.417-421
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• 2007

최근 홈 네트워크에 대한 관심이 높아짐에 따라 관련 기술을 이용하여 실생활에 적용하려는 연구가 활발히 진행되고 있다. 이러한 홈 네트워크 기술들 중에 무선 통신 기술인 Binary CDMA(Code Division Multiple Access)는 2.4Ghz의 RF영역을 사용하여 데이터를 전송한다. Binary CDMA는 Bluetooth보다 전송거리가 길며, 기존의 CDMA와 비슷한 성능을 보이면서 회로가 단순하여 가격이 저렴하다는 장점이 있다. 본 논문은 이러한 Binary CDMA 기술을 기반으로 가정 내 Multi Zone/Multi Source 오디오 시스템의 설계 및 구현을 제안한다. 구현된 시스템은 신뢰성 있는 무선 홈 오디오 시스템 구축을 위해 이 논문에서 제시하고 있는 무선 오디오 시스템 기기간의 망 구성 및 초기화 메커니즘을 적용하였다.

• Journal of the Korean Society of Safety
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• v.8 no.1
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• pp.64-70
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• 1993

Serious injuries and deaths due to multi-jointed robot occur when a man mispercepts. especially during robot teaching and maintenance work. Since industrial robots often operate with unpredictable motion patterns, establishment of safe speed limit of robot arm is indispensable. An experimental emergency conditions were simulated with a multi-jointed robot. and response characteristics of human operators were measured. The result showed that failure type, robot arm axis. and robot arm speed had significant effects on human reaction time. The reaction time was slightly increased with robot arm speed. though it showed somewhat different pattern owing to failure type. Furthermore the reaction time to the axis which could flex or extend. acting on a workpiece directly. was fastest and its standard deviation was small. The robot arm speed limit securing a‘possible contact zone’based on overrun distance was about 25cm/sec. and in this sense the validity of safe speed limits suggested by many precedent researchers were discussed.

• 연구논문집
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• s.31
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• pp.23-43
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• 2001

An experimental investigation on the reduction of nitrogen oxide emission from swirling, turbulent diffusion flames was conducted using multi air staged combustor, The combustor utilizes swirler to dampen fuel/air mixing, allowing an extended residence time for fuel pyrolysis and fuel-N conversion chemistry in an locally fuel-rich environment prior to burnout. This process also allow to reduce thermal NOx formation to lessen the temperature of reaction zone. The aerodynamic process therefore emulates the conventional staged combustion process, but without the need for the physically separate fuel-rich and -lean stages. Parametric studies on the ratios of each staged air and droplet size were carried out the feasibility of fuel/air mixing for low NOx combustion with diesel and pyridine mixed diesel fuel oil.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.85-90
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• 2014

In this paper, the transient thermal and residual stress analysis of the welding of 9% Ni steel plates using the FEA software ABAQUS are presented. The 9% Ni steel plates are welded manually with welding consumables of 70% Ni based Inconel type super-alloys (YAWATA WELD B (M)), producing a multi-pass/multi-layer butt weld. For these materials, temperature dependant mechanical and thermal material properties are used in the analysis. The back gouging is considered in welding process simulation. The FE thermal results are validated by comparing the real fusion profile and heat affected zone (HAZ). In addition, the continuous indentation test was conducted to measure the strength of base metal, HAZ and weld metal.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.17-32
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• 2006

The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

• Spatial Information Research
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• v.10 no.2
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• pp.331-343
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• 2002

Recently, as various fields of applications using space-borne imagery have been emphasized, interests on integrated analysis or fusion using multi-sources are also increasing. In this study, to investigate applicability of multiple imageries for further regional-scaled application, DN value analysis and multi-resolution classification by using KOMPSAT EOC imagery and Landsat 7 ETM+image data in the Namyangju-city area were performed, and then this classified results were compared to land-use thematic data at the same area. In case of classified results by using muff-resolution image data, it is shown that linear-type features can be easily extracted. furthermore, it is expected that multi-resolution classified image can be effectively utilized to urban environment analysis, according to results of similar pattern by comparative study based on multi-buffered zone analysis or so-called distance analysis along main road features in the study area.