• 지질공학
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• 제19권4호
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• pp.501-508
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• 2009

이 연구는 미원과 충주지역을 중심으로 한 옥천변성대 지역에서 절개지사면 토층붕괴와 관련하여 흙의 주요 특성을 알기위해 수행되었다. 실내시험을 위하여 붕괴지 토층과 인근의 비붕괴지 토층에서 35개 사면으로부터 불교란 시료와 교란 시료를 각각 채취하여 일련의 물성시험과 역학시험을 하였다. 분석결과에 의하면 붕괴지 사면의 토질특성은 흙의 활동지수(AMI)가 0.75 이상이고, 액성한계가 32% 이상, 함수비가 31% 이상일 때 붕괴에 취약한 것으로 나타났다. 그리고 붕괴지 토층의 소성지수는 습윤밀도 및 포화밀도와 상관성이 있으며, 소성지수가 크면 간극비가 작아도 붕괴에 취약한 것으로 나타났다. 입도분포는 점토의 함량보다는 모래나 자갈의 함량이 많을수록 붕괴에 더 영향을 미치는 것으로 나타났다.

• 한국해양공학회지
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• 제11권1호
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• pp.113-123
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• 1997

The welding residual stresses produced by welding frequently cause a crack and promote stress corrosion etc. in heat affected zone contained with external load and weakness of material. For the purpose pof relaxation of welding residual stress, post welding heat teratment(PWHT) is widely used. In this paper, the computer program which is based on Thermal-Elasto-plastic-creep theory for plane deformation on developed by finite element method (F.E.M) and verified its propriety by experimental measurement and also by using the developed computer program. The mechanical behavior of butt welding joint is clairfied during PWHT.

• ETRI Journal
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• 제35권2호
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• pp.352-355
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• 2013

Common stereoscopic three-dimensional (3D) display has a convergence and accommodation conflict that violates the natural human cognitive process of viewing. This weakness exposes the challenge in supporting fun factors while eliminating safety problems in the 3D viewing experience. Thus, human factors have become a major research topic. In this letter, we propose a 3D stereoscopic visualization platform that can expand the sense of a 3D space by fusing organically mixed stereoscopic displays to provide a continuous feeling of 3D depth. In addition, we present pilot test results to show the possibility of the technical implementation of the proposed platform and note ongoing research issues to be addressed.

• 한국터널지하공간학회 논문집
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• 제20권5호
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• pp.855-867
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• 2018

터널 굴진면 전방에 연약대가 존재할 때에는 종방향 아칭에 의해서 굴진면 직전영역에 응력이 증가되어 터널의 안정성이 영향을 받는다. 따라서 굴진면 전방에 연약대 존재 여부 및 연약대의 특성을 파악하여 이에 대한 대비책을 마련하는 것이 중요하다. 굴진면 전방 연약대의 예측 방법은 물리탐사 및 수치해석적 방법과 터널지보 및 보강방안에 대한 연구는 많이 이루어 졌으나 굴진면 전방 연약대의 폭과 이격거리에 따른 이완영역에 대한 연구는 미비한 실정이다. 본 연구에서는 굴진면 전방에 연약대 존재 시 연약대의 폭과 이격거리에 따른 이완영역에 대하여 실내모형실험을 통해 규명하였다. 모형시험기에 주문진 자연사를 이용하여 함수비 3.8%로 모형 원지반을 조성하였으며 모형 연약대는 모형 원지반과 같은 자연건조 상태의 주문진 자연사를 샌드커튼 방식으로 강사하여 조성하였다 연약대 폭과 굴진면과 연약대 간 이격거리를 변화시키며 실험을 수행하였다. 모형시험기는 상하반단면 굴착이 구현 가능하도록 제작하였으며, 토조 바닥에 로드셀을 설치하고 지표에 변위계를 설치하여 터널굴착에 따른 연직응력 및 지표변위를 측정하였다. 지표침하는 연약대의 폭에 상관없이 굴진면과의 이격거리가 0.25D 이내에서 급격히 증가하였고, 수직응력 및 수평응력 또한 이격거리가 0.5D 이내에서부터 증가하는 경향이 나타났다. 실험결과 종방향 아칭의 영향은 터널 전방 1.0D 영역 내부터 형성된다고 판단된다.

• Journal of Korean Neurosurgical Society
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• 제46권4호
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• pp.340-345
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• 2009

Objective : We investigated the locations of compressing vessels in hemifacial spasm. To approach compression sites, we described and evaluated the efficacy of the infranuchal infrafloccular (INIF) approach. Methods : A retrospective review of 31 consecutive patients who underwent microvascular decompression (MVD) through INIF with a minimum follow-up of 1 year was performed. Along the intracranial facial nerve, we classified the compression sites into the transitional zone (TRZ), the central nervous system (CNS) segment and the peripheral nervous system (PNS) segment. The INIF approach was used to inspect the CNS segment and the TRZ. Subdural patch graft technique was used in order to achieve watertight dural closure. The cranioplasty was performed using polymethylmethacrylate. The outcome and procedure-related morbidities were evaluated. Results : Twenty-nine patients (93%) showed complete disappearance of spasm. In two patients, the spasm was resolved gradually in 2 and 4 weeks, respectively. Late recurrence was noted in one patient (3%). The TRZ has been identified as the only compression site in 19 cases (61.3%), both the TRZ and CNS segment in 11 (35.5%) and the CNS segment only in 1 (3.2%). There was no patient having a compressing vessel in the PNS segment. Infection as a result of cerebrospinal fluid leak occurred in one patient (3%). Delayed transient facial weakness occurred in one patient. Conclusion : The TRZ and the CNS segment were more vulnerable area to the compression of vessels. We suggest that surgical avenue with the INIF approach provides early identification of this area.

• 한국정밀공학회지
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• 제29권10호
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• pp.1078-1088
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• 2012

In this paper, we present research experimental results about the different thickness T-joint welding of the high power continuous wave(CW) Nd:YAG laser for the secondary battery of a vehicle. Although the conventional method used for the secondary battery is a argon TIG welding, we utilize a laser welding to improve Tungsten Inert Gas(TIG) welding's weakness. The laser, which has a couple of advantage such as aspect ratio, low Heat Affected Zone(HAZ), good welding quality and fast productivity utilized in this work is a CW Nd:YAG laser. In order to observe laser welding sections, we used a optical microscope. Through the analysis of the metallographic, hardness, aspect ratio, and heat input, we obtained the desired data in condition of 1800 W laser beam power and 1.8 m/min and 2.0 m/min laser beam travel speeds. In order to compare electric resistances of the argon TIG welding and laser welding, we made an actual battery and the electric resistance of the laser welding is reduced by 40~45% comparing with the argon TIG welding.

• 한국철도학회논문집
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• 제9권2호
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• pp.230-236
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• 2006

For a short-term measurement to reduce an accident on a railroad crossing, it is necessary to find out the weakness and problems of existing equipment in the railroad transportation system. The analysis of railroad crossing accidents shows that main causes of accidents (24.9%) are the careless driving including an engine problem, damage on the safety equipment, slide on the snow, and an engine stop on the railroad crossing. Therefore, it is required to install a sensor, or to make a crossing gate at the exist for detecting obstacles on a railroad to prevent collisions among trains. This paper suggests 'a panel sensor using the strain gauge' to make up the weaknesses of the sensing Dead Zone, which are caused by using a laser method, and to detect any small objects passing railroads in order to reduce the errors, which are occurred in the earth magnetic field for controlling Exit Slide Crossing Arm Detector. The device, suggested in this paper, is verified with detecting any small objects passing the railroad, with judging entry decision clearly, and with controlling passing gate and obstruction warnings/cautions obstacles at the same time, through an experimental test.

• Journal of Welding and Joining
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• 제33권6호
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• pp.49-54
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• 2015

Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

• 한국지진공학회논문집
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• 제9권4호
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• pp.1-10
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• 2005

본 연구의 목적은 국내 실정에 적합한 원전 기초지반의 지진안정성을 평가할 수 있는 적절한 해석모델을 제시하는 것이다 입력지진의 작용방향, 경계조건, 해석모델의 폭 및 깊이, 단층연약대의 모델링방법 등의 해석조건에 대하여 활동면해석법, 등가정적해석법, 동적해석법을 적용하였다. 해석결과 측면경계조건은 등가정적 해석시 수평롤러, 동적해석시 전달경계, 해석영역의 폭은 구조물 폭의 5배 이상, 깊이는 구조물 폭의 2배 이상을 적용하는 것이 바람직한 것으로 나타났다.

• 설비공학논문집
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• 제20권11호
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• pp.711-717
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• 2008

Despite the fact that UFAD(Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of supplied air temperature and supplied flow rate on the performance of UFAD, especially focused on thermal comfort. Also this study has compared UFAD with conventional overhead air distribution system. In contrast to the well-mixed room air conditions of the conventional overheat system, UFAD system produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the occupied zone and more efficiently removes heat loads and contaminants from the space. Thermal comfort parameters were evaluated by CFD approach and then PMV was computed to detect the occupants' thermal sensation. Results show that radiative mean temperature plays crucial role on the evaluating PMV. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.