• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.124-131
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• 1997

흡착식 유회수기의 운전조건을 결정하는데 있어서 스키머의 구동속도와 기름의 물리.화학적 성질에 따른 스키머의 유회수율을 예측하는 것이 필요하다. 이 문제에 대한 이론적인 접근으로 수직구동 평판상에 부착된 기름층의 자유표면유동을 두가지 방법으로 조사하였다. 그 하나는 표면코팅시 얇은 유막에 대하여 수행하는 정상유동해석이며, 다른 방법으로는 스키머 표면유막에 대한 안정성해석이다. 해석은 기름층이 충분히 두꺼워서 스키머는 기름층에서만 작동한다고 가정하였다. 이론추정 결과는 롤러타입의 스키머에 대하여 계측한 실험치와 비교하였는데, 유막의 안정성해석 결과가 유회수기와 같이 상대적으로 고레이놀즈수에서 작동하는 유동의 경우에는 정상해석보다 좀 더 합리적으로 유막의 두께를 산정함을 알 수 있었다. 한편, 물위에 떠있는 얇은 유막층의 유회수성능도 실험하여서 주어진 유막두께에 대하여 롤러의 최적구동속도를 함께 조사하였다.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.991-993
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• 2003

본 논문에서는 영구자석 기기에서 발생하는 d-q축간의 상호 포화(cross saturation) 문제에 대해 다루었고, 이를 고려한 d축과 q축의 전류에 따른 전동기의 특성값을 수치 해석적으로 도출하는 방법을 제시하였다. 아울러 다층 회전자 구조를 지닌 매입형 영구자석 전동기(multi-layer buried magnet synchronous motor)의 d축 및 q축 인덕턴스 값을 교차 결합 특성(Cross-Coupling)을 고려하여 수치 해석적 기법을 통해 도출하였으며, 실험값과의 비교를 통해서 기존의 해석 방법보다 우수함을 입증하였다.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.20-22
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• 2005

본 연구에서는 유도기의 사용 환경과 운전 조건을 고려하여 출력 1 [MW]급의 대형 유도기를 설계하였다. 유도기의 설계사양은 당사의 유도기 설계 프로그램(=등가회로법)을 통하여 전체적인 사양을 도출하였고, 기계 방정식과 결합된 유한요소 해석 프로그램을 이용하여 세부적인 동특성을 해석하였다. 유도기의 설계 변수는 턴수, 슬롯면적, 운전전압으로 하였고, 구동 주파수 25~60 [Hzl의 범위에서 가장 효율이 높은 유도기를 설계하였다. 해석의 타당성을 검증하기 위하여 샘플용 유도기를 제작하고 부하 시험을 수행하여 해석결과와 비교하였다. 부하 시험은 구동 주파수 25$\sim$60 [Hz]의 범위에서 부하율을 25$\sim$100 [%]로 변화시켜 수행하였다.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.49.3-49.3
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• 2019

햇무리(halo) 모양 코로나질량방출(coroanl mass ejection) 현상은 1970년대 후반 처음 발견된 이후, 그 물리적 본질에 대해 많은 논쟁이 있었다. 우주 망원경 SOHO LASCO의 고분해능 관측이후, 햇무리 모양은 시선방향에 나란한 방향으로 팽창하며 진행하는 고깔모양의 자기 구조(cone-shaped magnetic flux rope)가 2차원 관측이미지에 투영된 것으로 해석하는 것이 정설이다. 우리는 이러한 해석이 사실인지 관측을 이용해 검증하고, 타당한 물리적 해석을 찾는다. 이를 위해 STEREO 우주선이 SOHO에서 관측한 태양의 측면을 관측했던 2010년부터 2012년 관측자료를 사용하고, SOHO에서 관측한 햇무리 모양의 코로나질량방출 현상의 측면 모습이 예전의 해석대로 고깔모양을 보여주는지 STEREO 우주선의 관측자료와 비교한다. 우리는 햇무리 모양이 시선방향에 상관없는 이 현상 고유의 모양임을 확인 했으며 극자외선 관측결과와 수치계산 결과와 비교하여 이 햇무리 모양은 파동 현상의 결과임을 알았다. 이는 코로나질량방출 현상과 관련한 해석에 많은 변화가 필요함을 의미한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.138-145
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• 2017

The purpose of this study is to establish a reasonable analytical method for the estimation of overall behavior characteristic from cracking to yielding of rebar and crushing of concrete and seismic performance of reinforced concrete shear wall with high-strength reinforcing bar. A total of 8 specimens of reinforced concrete walls which have constant aspect ratio and a variety of variables such as reinforcement ratio, reinforcement yielding strength, reinforcement details, concrete design strength, section shape and whether lateral restraint hoop were selected and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the proposed constitutive equation by the authors. The mean and coefficient of variation for maximum load from the experiment and analysis results was predicted 1.04 and 8%. The mean and coefficient of variation for displacement corresponding maximum load from the experiment and analysis results was predicted 1.17 and 19% respectively. The analytical results were predicted relatively well the fracture mode and the overall behavior until fracture for all specimens. These results are expected to be used as basic data for application of high-strength reinforcing bar to design codes in the future.

• Composites Research
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• v.23 no.3
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• pp.19-30
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• 2010

The present study describes a method for analytical solution to elastic field in structural elements of general symmetric laminated composite materials. The two dimensional plane stress elasticity problems under mixed boundary conditions are reduced to the solution of a single fourth order partial differential equation, expressed in terms of a single unknown function, called displacement potential function. In addition, all the components of stress and displacement are expressed in terms of the same displacement potential function, which makes the method suitable for any boundary conditions. The method is applied to obtain analytical solutions to two particular problems of structural elements consisting of an angle-ply laminate and a cross-ply laminate, respectively. Some numerical results are presented for both the problems with reference to the glass/epoxy composite. The results are highly accurate and reliable as all the boundary conditions including those in the critical regions of supports and loads are satisfied exactly. This verifies the method as a simple and reliable one as well as capable to obtain exact analytical solution to elastic field in structural elements of composite materials under mixed and any other boundary conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.604-613
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• 2018

In recent years, numerous train derailment accidents caused by deterioration and high speed technology of railways have increased. Guardrails or barriers of railway bridges are installed to restrain and prevent the derailment of the train body level. On the other hand, it can result in a high casualties and secondary damage. Therefore, a Derailment Containment Provision (DCP) within the track at the wheel/bogie level was developed. DCP is designed for rapid installation because it reduces the impact load on the barrier and inertia force on the steep curve to minimize turnover, fall, and trespass on the other side track of the bridge. In this paper, DCP was analyzed using LS-Dyna with a parameter study as the impact loading location and interface contact condition. The contact conditions were analyzed using the Tiebreak contact simulating breakage of material properties and Perfect bond contact assuming fully attached. As a result, the Tiebreak contact behaved similarly with the actual behavior. In addition, the maximum displacement and flexural failure was generated on the interface and DCP center, respectively. The impact analysis was carried out in advance to confirm the DCP design due to the difficulties of performing the actual impact test, and it could change the DCP anchor design as the analysis results.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.484-492
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• 2016

The turbine is an important component and has a significant impact on the thermodynamic efficiency of the organic Rankine cycle. A precise preliminary design is essential to developing efficient turbines. In addition, performance analysis and structural analysis are needed to evaluate the performance and structural safety. However, there are only a few exclusive studies on the development process of the radial inflow turbines for the organic Rankine cycle (ORC). In this study, a preliminary design of the ORC radial inflow turbine was performed. Subsequently, the performance and structural analysis were also carried out. The RTDM, which was developed as an in-house code, was used in the preliminary design process. The results of the performance analysis were found to be in good agreement with target performances. Structural analysis of the designed turbine was also carried out in order to determine whether the material selection for this study is suitable for the flow conditions of the designed turbine, and it was found that the selected aluminum alloy is suitable for the designed turbine. However, the reliability of the preliminary design algorithms and numerical methods should be strictly verified by an actual experimental test.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.747-761
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• 2011

This paper presents an investigation on the change in the statical behavior and the ultimate capacity of steel cable-stayed bridges after cable failure. Cable failure can occur due to fire, direct vehicle clash accidents, cable or anchorage fatigue, and so on. Moreover, the cable may be temporarily disconnected during cable replacement work. When cable failure occurs, the load, that was supported by the broken cable is first transferred to another cable. Then the structural state changes due to the interaction between the girder, mast, and cables. Moreover, it can be predicted that the ultimate capacity will decrease after cable failure, because of the loss of the support system. In this study, the analysis method is suggested to find the new equilibrium state after cable failure based on the theory of nonlinear finite element analysis. Moreover, the ultimate analysis method is also suggested to analyze the ultimate behavior of live loads after cable failure. For a more rational analysis, a three-step analysis procedure is suggested and used, which consisted of initial shape analysis, cable failure analysis, and live load analysis. Using this analysis method, an analytical study was performed to investigate the changes in the structural state and ultimate behavior of steel cable-stayed bridges.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1123-1124
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• 2011

본 논문에서는 ESW(Electro slag welding)의 용접을 위한 해석을 수행하였다. 특히, 열전달 해석을 통하여 부재내부에 발생하는 온도분포에 대한 해석을 수행하였으며, 이를 입력조건으로 하여 구조해석을 수행함으로써, 최종적은 부재내의 최고온도와 최대 변형량을 구할 수 있었다.