• 전산구조공학
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• 제8권4호
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• pp.173-180
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• 1995

본 논문에서는 그라우팅공법을 적용하여 진동원으로부터 전파되어 나가는 지반진동을 감소시키기 위한 연구를 수행하였다. 지반의 진동전파모델을 만들기 위해 직접구성에 의한 경계요소법이 사용되었고, 그라우팅층이 진동원의 바로 밑에 있는 것이 가장 진동감쇠효과가 좋으며 그라우팅층의 두께 및 폭이 일정값 이상이 될 필요가 없는 것으로 파악되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.655-658
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• 2003

The crack of concrete structure plays an important role in the durability and safety of structure. Therefore, the features such as width, length, and direction of that must be measured periodically. The conventional method of measurement of cracks is manually sketched, however. it takes a fairly long time and lacks quantitative objectivity. This study proposes the algorithm to extract and analyze cracks automatically. The proposed algorithm is composed of two sub-algorithms. The extraction algorithm includes elimination of effect due to light, binarization. and noise reduction. The analysis algorithm includes thinning process, labeling, and calculation of crack width, length, and direction. The test to demonstrate the algorithm is fulfilled using the images of cracks on real concrete surface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.597-600
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• 2002

In general, the function of intake structure, whether it be a open channel, a fully wetted tunnel, a sump or a tank, is to supply an evenly distributed flow to a pump station. An even distribution of flow, characterized by strong local flow, can result in formation of surface or submerged vortices, and with certain low values of submergence, may introduce air into pump, causing a reduction of capacity and efficiency, an increase in vibration and additional noise. Uneven flow distribution can also increase or decrease the power consumption with a change in total developed head. To avoid these sump problems pump station designers are considered intake structure dimensions, such as approaching upstream, baffle size, sump width, width of pump cell and so on. From this background, flow characteristics of intake within sump are Investigated numerically to obtain the optimal sump design data. The sump model is designed in accordance with HI code.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.498-501
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• 2002

In the conventional PWM converter, high-frequency switching techniques was used for high-density of energy, but occurred a lot of problems such as switching losses, switching voltage/current stresses, EMI(Electromgnetic Interference) and so on. To overcome these problems, various soft switching techniques have been presented. However these techniques are focused on reducing switching losses and voltage/current stresses . The simulation and experimental results are shown that the active clamp ZVS flyback converter with the proposed RPWM(Random Pulse Width Modulation) technique reduces the conducted noise.

• Journal of Welding and Joining
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• 제18권6호
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• pp.83-88
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• 2000

Variation of welded-joint hardness and tensile strength of a accelerated-cooled fine-grained ferritic-pearlitic steel with heat input was investigated. In a weld heat-affected zone, a softened zone was formed and it had lower hardness than that of a base metal. While the width of a softened zone increased continuously with an increase of heat input up to 100kJ/cm. the minimum hardness in a softned zone was almost constant after a continuos decrease up to 60KJ/cm. Because of a softened zone, the welded-joint was fractured in the HAZ and its maximum reduction of tensile strength was about 20%. Measured welded-joint tensile strength and calculated minimum tensile strength in a welded-joint was almost same, which means that the plastic restraint of a softened zone did not occur in this experiment. It is believed that as a softened zone width-to-specimen thickness ratio is as high as 2~6 in this experiment, the plastic restraint effect does not occur. Theoretical analysis shows that the plastic restraint effect occurs only when the ratio is below 0.5.

• Structural Engineering and Mechanics
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• 제48권3호
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• pp.383-394
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• 2013

Cold-formed profiles have been largely used in the building industry because they can be easily produced and because they allow for a wide range of sections and thus can be utilized to meet different project requirements. Attainment of maximum performance by structural elements with low use of material is a challenge for engineering projects. This paper presents a numerical study aimed at minimizing the weight of lipped and unlipped cold-formed channel columns, following the AISI 2007 specification. Flexural, torsional and torsional-flexural buckling of columns was considered as constraints. The simulated annealing method was used for optimization. Several numerical simulations are presented and discussed to validate the proposal, in addition to an experimental example that qualifies its implementation. The ratios between lips, web width, and flange width are analyzed. Finally, it may be concluded that the optimization process yields excellent results in terms of cross-sectional area reduction.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2009년도 추계학술대회
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• pp.50-51
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• 2009

선박은 충돌로 인한 침수, 화채 등 여러가지 이유로 긴급피난을 감행해야하는 경우가 많다. 특히, 선박의 경우 그 구조의 특성상 줍고 미로같은 복잡한 형태로 구성되어 신속한 탈출이 어렵다. 화재에 의한 인명손상의 경우 연기에 의한 질식사가 부분을 차지하므로 신속한 탈출은 생존율 향상에 중요한 역할을 한다. 이 연구에서는 기존과 제안된 선박구조에 대한 화재확산과 승무원 피난시간을 검토한다.

• 전력전자학회논문지
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• 제26권2호
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• pp.135-140
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• 2021

This study introduces a new pulse width modulation (PWM) method to reduce common-mode voltages (CMVs) and then compares its performance with other reduced CMV-PWM (RCMV-PWM) methods. CMVs should be reduced to ensure the electromagnetic compatibility and safety of grid-connected inverters. RCMV-PWM methods attempt to synthesize voltage references without zero vectors, which cause high CMV peaks. In these methods, the peak-to-peak magnitude of CMVs can be reduced by one-third of the conventional space-vector PWM. The introduced method splits every reference vector into two vectors to avoid the use of zero vectors. The performances of the RCMV-PWM methods are analyzed in accordance with the modulation index through simulation and experiment.

• 대한기계학회논문집B
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• 제21권9호
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• pp.1139-1148
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• 1997

Compression waves propagating in a high-speed railway tunnel develops large pressure fluctuations on the train body or tunnel structures. The pressure fluctuations would cause an ear discomfort for the passengers and increase the aerodynamic resistance of trains. As a fundamental research to resolve the pressure wave phenomenon in the tunnel, experiments were carried out by using a shock tube with an open end. A blockage to model trains inside the tunnel was installed on the lower wall of shock tube, thus forming a sudden cross-sectional area reduction. The compression waves were obtained by the fast opening gate valve instead of a conventional diaphragm of shock tube and measured by the flush mounted pressure transducers with a high sensitivity. The experimental results were compared with the previous theoretical analyses. The results show that the ratio of the reflected to the incident compression wave at the sudden cross-sectional area reduction increases but the ratio of the passing to the incident compression wave decreases, as the incident compression wave becomes stronger. This experimental results are in good agreements with the previous theoretical ones. The maximum pressure gradient of the compression wave abruptly increases but the width of the wave front does not vary, as it passes over the sudden cross-sectional area reduction.

• 한국도로학회논문집
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• 제4권2호
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• pp.33-42
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• 2002

포장은 건조수축이나 온도변화 또는 차량의 반복하중 등으로 인하여 균열이 발생하게 된다. 발생된 균열 부위로 우수의 침입 및 비압축성 물질이 침투하여 하부층의 지지력 저하, 과다한 스폴링, 2차 균열 등의 파손이 발생하게 된다. 이런 문제점을 해소하기 위해서는 균열폭을 제한하여 관리해야하며 이것은 정확한 균열폭 감지를 필요로 한다. 현재의 측정방법은 공간적 시간적으로 많은 제약을 받는 현미경을 이용한 육안조사가 전부인 실정이다. 본 연구의 목적은 망원렌즈를 장착한 자동포장상태 조사장비를 사용하여 도로에서 주위차량과 비슷한 속도로 주행하면서 가장 정확한 균열폭을 감지할수 있는 조건을 찾는 것이다. 본 연구는 모의조사를 통하여 균열폭 크기에 따른 카메라 초점거리를 결정하고 망원렌즈를 부착한 카메라로 노면을 확대 촬영한 자료를 이미지프로세싱 프로그램인 STADI-2에서 여러 가지 factor를 사용하여 산출된 균열폭과 현장조사를 통하여 현미경으로 실측한 균열폭을 비교 분석한 결과, 이미지프로세싱을 이용한 최적균열폭 감지조건을 제시하였다. 연구결과 CRCP(연속철근콘크리트포장)에서는 카메라 초점거리 75mm를 사용하여 균열폭 0.5mm$\sim$1.2mm일때 정확도 80%이상으로 측정 가능했으며 아스팔트포장에서는 카메라 초점거리 12.5mm를 사용하여 균열폭 1.8mm$\sim$3.3mm에서 90%의 정확도로 균열폭을 감지할 수 있었다.