• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1213-1220
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• 2008

In this study, the crashworthy design guidelines for the high speed EMU were derived and numerically evaluated. As for this high speed train, there are several different features from the KTX in that the conventional type bogies are adopted and the front end car (TC car) accommodates passengers. It is natural that the impact acceleration of the front end car should be controlled under the appropriate level stipulated at safety regulations for collision accidents. Also, car-to-car interfacing structures and devices should be deliberately designed to prevent overriding and telescoping mechanisms. As the first step for these design countermeasures, it was studied that how much impact energy should be absorbed at the energy absorbing zones and devices of each carbody to satisfy the impact acceleration regulations of the safety regulations. These results will be used as the crashworthy design guidelines for the high speed train in the next year research.

• 한국안전학회지
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• 제11권4호
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• pp.3-9
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• 1996

In this study, comparison of theoretical solutions with experimental results is examined through fracture conditions for the case of float glasses subjected static loading. The range of fracture generation limits and critical penetration energies are solved according to the impactor mass under the high velocity, and analytical method of fracture strength and penetration strength are presented. Also, fracture patterns are investigated according to impact velocities. The results obtained from this study are as follows ; 1) Radial cracks are generated from the loading point regardless of plate thickness in the case of the plate subjected to the static loading. In the case of high-speed impact, dimensions of ring cracks become to smaller and length of radial cracks becomes shorter with the rapidity of impact velocity. 2) Kinetic change volume of collision after/before is constant regardless of velocities over the range of critical penetration velocity. 3) Although the same impact energy is working, the critical penetration energy is increased with the shorter of impactor mass. 4) Although the same impact energy is working, the penetration fracture of lighter Impactor mass is generated more than that of heavier impactor mass, and the impulse of lighter impacter mass appear more than that of heavier impactor mass. Therefore, the penetration fracture in the case of greater impulse is generated earlier regardless of the of the dimensions of Impact loading.

• 한국재료학회지
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• 제26권11호
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• pp.611-622
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• 2016

Particle morphology change and different experimental condition analysis during composite fabrication process by traditional ball milling with discrete element method (DEM) simulation were investigated. A simulation of the three dimensional motion of balls in a traditional ball mill for research on the grinding mechanism was carried out by DEM simulation. We studied the motion of the balls, the ball behavior energy and velocity; the forces acting on the balls were calculated using traditional ball milling as simulated by DEM. The effect of the operational variables such as the rotational speed, ball material and size on the flow velocity, collision force and total impact energy were analyzed. The results showed that increased rotation speed with interaction impact energy between balls and balls, balls and pots and walls and balls. The rotation speed increases with an increase of the impact energy. Experiments were conducted to quantify the grinding performance under the same conditions. Furthermore, the results showed that ball motion affects the particle morphology, which changed from irregular type to plate type with increasing rotation speed. The evolution was also found to depend on the impact energy increase of the grinding media. These findings are useful to understand and optimize the particle motion and grinding behavior of traditional ball mills.

• 한국태양에너지학회 논문집
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• 제33권6호
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• pp.19-25
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• 2013

Energy generation from an instrumented Skystream 3.7 small wind turbine was used to investigate the effect of ambient turbulence levels on wind turbine power output performance. It is widely known that elevated ambient turbulence level results in decreased energy production, especially for large sized wind turbine. However, over the entire wind speed range from cut in to the rated wind speed, the measured energy generation increased as ambient turbulence levels elevated. The impact degree of turbulence levels on power generation was reduced as measured wind speed approached to the rated wind speed of 13m/s.

• Advances in materials Research
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• 제12권1호
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• pp.67-81
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• 2023

Basalt and poly-ester fibers along with epoxy resin were used to produce inter-ply, intra-ply and functionally gradient hybrid composites. In all of the composites, the relative content of basalt fiber to poly-ester fiber was equal to 50 percent. The flexural and charpy impact properties of the hybrid composites are presented with particular regard to the effects of the hybrid types, stacking sequence of the plies, loading direction and loading speed. The results show that with properly choosing the composition and the stacking sequence of the plies; the inter-ply hybrid composites can achieve better flexural strength and impact absorption energy compared to the intra-ply and functionally gradient composites. The flexural strength and impact absorption energy of the functionally gradient hybrid composites is comparable to, or higher than the intra-ply sample. Also, by increasing the loading speed, the flexural strength increases while the flexural modulus does not have any special trend.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.48-53
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• 2007

The objective of this paper is to investigate the influence of impact conditions on the impact characteristics of the stainless sheet for the case of the fixed boundary conditions. In order to examine impact characteristics of the sheet, three-dimensional finite element analyses and impact tests have been performed. High speed tensile tests have been carried out to obtain strain-stress relationships including the effects of the strain rate. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor have been introduced. The results of the FE analyses and the impact tests have been shown that the diameter of the impact head does not affect the absorption energy of the stainless sheet. In addition, it has been shown that the absorption rate of energy maintains almost $82.5\;\sim\;83.5\;%$ irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, the variation of stress and strain energy in the stainless sheet has been quantitatively examined.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.505-517
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• 2016

The structural integrity of a dual-purpose metal cask currently under development by the Korea Radioactive Waste Agency (KORAD) was evaluated, through numerical simulations and a model test, under high-speed missile impact reflecting targeted aircraft crash conditions. The impact conditions were carefully chosen through a survey on accident cases and recommendations from literature. In the impact scenario, a missile flying horizontally hits the top side of the cask, which is freestanding on a concrete pad, with a velocity of 150 m/s. A simplified missile simulating a commercial aircraft engine was designed from an impact loade-time function available in literature. In the analyses, the dynamic behavior of the metal cask and the integrity of the containment boundary were assessed. The simulation results were compared with the test results for a 1:3 scale model. Although the dynamic behavior of the cask in the model test did not match exactly with the prediction from the numerical simulation, other structural responses, such as the acceleration and strain history during the impact, showed very good agreement. Moreover, the containment function of the cask survived the missile impact as expected from the numerical simulation. Thus, the procedure and methodology adopted in the structural numerical analyses were successfully validated.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.782-788
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• 2014

Wind power generation has been viewed as a promising renewable energy to meet challenge of climate change. However, wind power is susceptible to climate change because previous investigation shows there are declining trends of the land surface wind speeds over middle and lower latitudes. Since long term variation trends is notably different from inter-annual random variation and could have notable impact on wind farm from planning perspective, observed meteorological data of Taiwan is investigated to find out long term variation trends of wind speed and its impact on wind power generation. It is discovered that wind speed in majority of stations in west coast of Taiwan have ascending trends while that of all investigated stations in east coast have descending trends. Since east of Taiwan is not suitable for wind power development for its higher likelihood suffering Typhoons and most of established wind farm locate in west coast of Taiwan, it is speculated that long term variation trend of wind do not have notable negative impact on wind power generation in Taiwan.

• 한국철도학회논문집
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• 제17권3호
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• pp.178-185
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• 2014

본 연구에서는 국내 고속철도노선 전과정 중 건설단계에 대하여 각 분야별(토목, 궤도, 건축 및 전철전력/신호통신분야) 주요 건설자재 및 중장비 에너지 사용량을 토대로 전과정평가(Life Cycle Assessment, LCA) 방법론을 적용하여 주요 환경부하 특성을 분석하였다. 그 결과, 분야별 환경영향 기여도는 토목분야가 약 89%로 가장 높게 나타났으며, 궤도 7%, 건축 2%, 전철전력분야 2% 순으로 나타났다. 가장 기여도가 높은 토목분야의 경우, 주요 영향평가 범주는 지구온난화, 자원고갈, 광화학산화물생성으로 각각 54%, 25%, 8%로 나타났으며, 주요 영향인자는 레미콘과 시멘트인 것으로 분석되었다. 향후 철도 건설단계에서의 전과정평가 적용은 정량적인 환경부하 산정을 통해 효율적인 저감방법을 도입할 수 있다.

• 콘크리트학회논문집
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• 제27권4호
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• pp.363-375
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• 2015

본 연구에서는 탄성변형 에너지를 이용하는 충격실험장치인 변형에너지 충격시험장치(SEFIM)의 변형률 속도를 증가시키기 위하여, 탄성변형 에너지가 저장되는 에너지 프레임의 직경 및 재질을 다르게 하여 그 영향을 조사하였다. 현재 강재를 에너지 프레임의 재질로 사용한 SEFIM의 발현 가능한 변형률 속도범위는 10-40 /sec까지이지만, 에너지 프레임의 재질과 직경을 다르게 하여 충격 시 변형률 속도가 72 /sec까지 증가되었다. 충격실험에 사용된 HPFRCCs는 장섬유 1%와 단섬유 1%를 함께 초고강도 콘크리트에 혼입하였다. 정적 변형률 속도에서 뿐만 아니라, 네 가지 종류의 에너지 프레임을 사용한 높은 변형률 속도(14-72 /sec)에서도 변형경화 거동을 나타내었다. 에너지 프레임의 직경을 기존의 35 mm에서 25 mm로 작게 변경함에 따라서 변형률 속도가 증가하였으며, 에너지 프레임 재질을 강재, 알루미늄 그리고 티타늄으로 변경함에 따라, 강재보다 높은 탄성파 속도를 가지고 많은 크기의 탄성변형 에너지를 저장할 수 있는 티타늄 합금을 사용한 경우 더욱 높은 변형률 속도(72 /sec)를 생성하였다. 알루미늄 재질의 에너지 프레임의 경우 충격실험 시 작용되었던 응력으로 인해 탄성영역을 벗어나 소성변형을 일으켜 파단되어 본래 가지고 있던 성질을 발현하지 못하였다.