• 한국기계연구소 소보
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• s.15
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• pp.91-103
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• 1985

In this paper, temperature distribution and thermal stress are investigated considering engine peak pressure and the time average temperature distribution in the piston under running conditions for the diesel engine. The induced stress are calculated by the Finite Element Method(FEM). The results obtained are summerized as follows. 1) The results calculated by the FEM present good agreement with other numerical solution in literature. 2) It is confirmed that maximum compressive stress are induced in the part of outside wall between the piston crown and the pin bush. 3) In the axial direction, the hoop stresses are changed its sigh at the portion of crown near the inner wall side 4)Large gradient of temperature is shown in the piston crown near the side wall in the axial direction, in the part between the piton crown and the pin bush in radical direction 5)in case of stress distribution of piston wall surface in the axial direction, the hoop stress is a little greater than axial stress, and the latter is greater than the radial stress

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.268-273
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• 2000

기존의 웹 기반 학습 평가 시스템은 학습자의 선택 기회가 없는 상태에서 일방적으로 제시된 문제지로 평가하게 되거나, 문제 은행에서 임의로 추출한 문제도 단순히 무작위로나 난이도만을 고려하여 문제지를 구성하였고, 그 결과에 대한 성취도의 분석도 한 문제지에 대한 정오표 또는 점수로 단순하게 제시하기 때문에 학습자의 지속적인 학습 관리가 이루어지지 못하고 있다. 본 논문에서는 문제유형, 과목 및 단원 난이도, 문항 형태, 문항당 배점, 문항당 배당 시간등의 다양한 정보를 가진 유형별 문제 은행을 구축하였다. 학습자는 마치 문제집을 풀고 싶은 유형의 문제를 선택하듯이 문제 은행에서 문제를 자율적으로 구성하여 평가할 수 있는 유형별 문제지나 대학수학능력시험의 기준에 맞추어 자동 구성되는 종합 문제지로 다양하게 평가할 수 있다. 또한, 한문제지에 대한 결과뿐만 아니라 유형별, 월별 성취도 분석을 통하여 평가한 총점에 대한 획득한 점수의 누적 통계를 그래프로 일목요연하게 보여주어 한 학습자에 대한 지속적인 성취도 분석이 가능하도록 구축하였다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.9
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• pp.478-484
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• 2006

The paper presents methods of determining the capacity and installation positions of regenerative inverters installed in DC 1500V electric railway system. We suggested a method that approximates using parameters related to substations where regenerative inverters are installed, railway lines and operating motor cars, and another that calculates using regenerative power obtained from Train performance Simulation (TPS) and Power Flow Simulation (PFS). We carried out TPS and PFS for Seoul Subway Line $5{\sim}8$, calculating regenerative power and determining substations where regenerative inverters would be installed and the optimal capacity and number of inverters to be installed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.163-166
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• 2004

Epoxy composite reinforced with 3-D braided Glass/Aramid hybrid fabric was fabricated. FBG sensor was embedded along the braid yam in order to monitor the changes of the complicated inner region of the 3-D braid structure. The good linearity between Bragg wavelength and temperature was verified by several preliminary experiments. The strain inside 3-D braided beam was estimated using FBG sensor system, and the result was compared with the calculated value. It was found that FBG sensor system is very useful technique to investigate inside region of complicated structure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.92-98
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• 2015

This study investigates the durability of a two-passenger bicycle frame under non-uniform fatigue load. The bicycle frame of Model 1 installed with reinforcement support has a 20% lower maximum equivalent stress than the existing Model 2. Model 1 has a maximum total deformation that is less than half that of Model 2. Model 1 has a higher maximum fatigue life than Model 2. In addition, Model 1 has lower fatigue damage than Model 2. Thus, the bicycle frame of Model 1 installed with reinforcement support can be described as safer, as it offers more strength than Model 2. Applying this result to the design of a real two-passenger bicycle frame under non-uniform fatigue load can effectively prevent fatigue damage and improve durability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.107-112
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• 2012

Air flow and its pressure at electric fan according to three, four and five blades are analyzed in this study. As the number of blades increases at the same condition of specification, air tends to converge and becomes natural wind but higher power is consumed. And the velocity of wind is decreased as the space between winds becomes narrow. The turbulent flow is happened in the center of the body of revolution and the kinetic energy becomes largest in case of three blades. The pressure is decreased than atmospheric pressure from fan to outlet. As the number of blades increases, the pressure drop becomes smaller and is smallest in case of the fan with three blades. As the study result, The electric fan with three blades is thought to be effective in view of power consumption and design.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.68-75
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• 2012

This study aims at the structural analysis of vibration and fatigue according to the tie rod configuration. The maximum displacement amplitude is happened at 156Hz by harmonic vibration analysis, this tie rod model can be broken as the weakest state. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sine wave' becomes most stable. In case of 'Sine wave' with the average stress of 0MPa and the amplitude stress of 570MPa, the possibility of maximum damage becomes 70%. This stress state can be shown with 140 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. The structural result of this study can be effectively utilized with the design on tie rod by investigating prevention and durability against its damage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.65-71
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• 2011

This study analyzes about front axle through the analyses of stress, fatigue and vibration. Maximum equivalent stress is shown with the frequency of 60Hz in case of the harmonic vibration analysis applied with force. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of 0 to $-2{\times}10^5MPa$ and the amplitude stress of 0 to $-2{\times}10^5MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE Bracket history' or 'SAE transmission'. The structural result of this study can be effectively utilized with the design of front axle by investigating prevention and durability against its damage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.21-28
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• 2012

This study analyzes about automotive engine tension bearing through the structural analyses of fatigue and vibration. Maximum equivalent stress is shown at the lower of tensioner. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of 0 to $-10^{6}MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE Bracket history' or 'SAE transmission'. The structural result of this study can be effectively utilized with the design of tension bearing by investigating prevention and durability against its damage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.18-23
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• 2009

This study analyzes the thermal stress at automotive radiators on steady and transient states. The maximum displacement is shown at the lower corner of upper tank with the value of 0.51mm. The displacement becomes smaller at the center of radiator and it becomes larger at this edge. The maximum thermal stress with the value of 62 MPa is shown at the contact between upper tank and cooling plate. Thermal maximum stress with the transient state at the elapsed time of 10 second is lower than that at steady state as much as 0.7%.