• 한국기계가공학회지
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• 제15권3호
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• pp.44-51
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• 2016

This paper presents the characteristics of the energy absorption in an expansion tube type impact absorber that is applied to a high weight drop tester and the use of a response surface methodology to predict the impact energy absorption. In order to identify the characteristics of the energy absorption, a set of finite element analysis was conducted with Abaqus Explicit. Moreover, the ISCD-II sampling method and a first order polynomial were used to build a response surface. As a result, we demonstrated that the impact energy could be controlled by four main design variables, namely an expansion pipe's thickness, inner radius, pressing die's expansion angle and expansion ratio. Additionally, we observed the relationship between the four main design variables and the impact energy absorbing time, displacement, and maximum impact force.

• 한국수소및신에너지학회논문집
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• 제17권2호
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• pp.234-240
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• 2006

Al film(135.5 nm thick) with Pd film(39.6 nm thick) on the top of it was made by thermal evaporation method. Hydrogen absorption of Al/Pd film was measured by quartz crystal microbalance(QCM) method at room temperature. The sample was activated by hydrogen absorption and desorption cycling at room temperature. Hydrogen was introduced into the film by increasing hydrogen gas pressure step by step up to 640 torr at room temperature. Hydrogen concentration reached up to 25% at $5{\sim}10$ torr. But at high pressure the concentration decreased. This strange tendency was not understood yet. Further study is needed to find out the mechanism of hydrogen absorption in Al in Al/Pd film.

• 한국전기전자재료학회논문지
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• 제30권12호
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• pp.817-821
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• 2017

As a ZnO varistor is subjected to electrical and environmental stresses, it degrades gradually, which may result in power interruption by short circuit. This study investigates changes in the electrical characteristics of ZnO varistors due to deterioration owing to energy absorption, and determines the optimal parameters for on-line diagnosis of the varistor. Two types of varistors were used for an accelerated aging experiment involving the application of the $8/20{\mu}s$ standard lightning impulse current. The electrical characteristics in terms of the reference voltage, total leakage current, resistive leakage current, and third-harmonic component of the total leakage current were measured, and their change rates were analyzed. The results revealed that the total leakage current increased slightly with an increase in the varistor absorbed energy, while the resistive leakage current and the third-harmonic component increased apparently. Therefore, the third-harmonic component of the total leakage current was proposed as the optimal parameter for on-line monitoring of ZnO varistor conditions.

• 한국수소및신에너지학회논문집
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• 제4권1호
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• pp.41-50
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• 1993

The hydrogen absorption and desorption characteristics of microencapsulated (CFM)$Ni_{4.7}Al_{0.2}Fe_{0.1}$ and $MmNi_4Fe$ powder with Ni and/or Cu by means of chemical plating method have been investigated. Initial hydrogen absorption rate and activation property were increased remarkably by encapsulation and subsequent compacting. Pellets abtained by compacting of Cu-encapsulated fine powder have fairly good strength even after 30 cycles of hydriding and dehydriding. Encapsulated alloy powder and their compacts show a good resistance to degradation by $O_2$ or CO in hydrogen.

• Korean Chemical Engineering Research
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• 제43권2호
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• pp.294-298
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• 2005

연소기체로부터 이산화탄소를 흡수하는 유동층 공정에 사용되는 흡수제의 흡수 및 재생 반응특성을 측정 및 고찰하였다. 유동층 공정을 위해서 제조된 흡수제 Sorb NH의 흡수 및 재생 반응속도는 순수한 $Na_2CO_3$보다 더 빨랐다. 흡수 반응에서 Sorb NH의 겉보기 활성화에너지는 -10,100 cal/g mol, 순수한 $Na_2CO_3$의 겉보기 활성화에너지는 -12,200cal/g mol이었다. 재생반응에서 Sorb NH의 겉보기 활성화에너지는 약 12,050 cal/g mol, 순수한 $Na_2CO_3$의 활성화에너지는 약 11,320 cal/g mol이었다.

• Composites Research
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• 제28권4호
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• pp.176-181
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• 2015

본 연구에서는 stuffed Whipple shield의 성능 향상을 목적으로, stuffed Whipple shield의 중간층에 적용되는 직물의 방탄 성능 향상 기법으로서 Z형 직물 디자인을 제안하였다. 직물은 경계조건에 의하여 충격 현상과 방탄 성능이 크게 변화하게 된다. 따라서 기존의 단순 적층식 직물과는 다른 경계조건을 갖는 Z형 직물을 제안하였고, Z형 직물의 방탄 성능을 확인하기 위하여 상용 프로그램 LS-DYNA를 이용한 아라미드 섬유사와 직물에 대한 충격해석을 수행하여 에너지 흡수 특성을 계산하고, 그 결과를 단순 적층식 섬유사와 직물의 경우와 비교하였다. 그 결과 Z형 직물은 단순 적층식 직물과는 다른 충격 거동을 보이고, 고속 영역에서 2 edge fixed, 4 edge fixed보다 높은 에너지 흡수율을 보이는 것을 확인하였다.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1241-1248
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• 2002

Performance extension of the absorption refrigerator with LiBr solution is often faced to operate very close to the crystallization limit. Especially in the development of an air-cooled cycle, the crystallization of working solution in the system is a very difficult problem to overcome. This paper describes the cycle of hot water driven absorption system using a new working absorption solution instead of LiBr solution to improve the efficiency. In this study, we found out the characteristics of new working absorption solution through the cycle simulation and compared LiBr solution to evaluate. The effect of cooling water temperature, weak solution flow rate, hot water temperature and hot water flow rate were also examined. The COP is increased 22% higher in the case of LiBr＋Li1＋LiC1＋LiNO$_3$＋$H_2O$, 2% LiBr＋HO(CH$_2$)$_3$OH＋$H_2O$ than that of LiBr solution for the same operation condition.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2003년도 추계 학술발표회 논문집
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• pp.271-276
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• 2003

• 청정기술
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• 제16권3호
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• pp.213-219
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• 2010

볼텍스튜브는 고압의 가스를 이용하여 고온 가스와 저온 가스를 분리하거나 입자상 물질의 분리에 사용할 수 있는 장치이다. 이러한 볼텍스튜브의 에너지분리 특성과 물질분리 특성을 활용하여, 연소가스로부터 $CO_2$를 흡수하는 장치의 핵심부품으로 적용할 수 있다. 본 연구에서는 $CO_2$ 흡수용 볼텍스튜브의 기본설계 자료를 구축하기 위하여 에너지분리 성능실험을 수행하였다. 설계를 위한 기초 자료를 확보하기 위하여, 볼텍스 발생기의 오리피스 직경, 노즐면적비 및 튜브의 길이가 에너지분리 특성에 미치는 영향력을 실험을 통하여 분석하였다. 결과적으로 오리피스 직경이 볼텍스튜브의 성능에 지배적인 설계인자임을 확인하였으며, 노즐면적비와 튜브길이의 영향력은 미미하였다. 오리피스 직경이 작고(Dc=0.6D), 노즐면적비가 중간 이상(AR=0.14~0.16)이며, 튜브 길이가 긴 모델(L=16D)이 저온 출구 측과 고온 출구 측의 열전달에서 가장 우수한 성능을 나타내었다. 본 연구의 결과는 $CO_2$흡수용 $100Nm^3$/hr급 볼텍스튜브의 기본설계 자료로 활용될 예정이다. 볼텍스튜브를 적용한 $CO_2$흡수 공정을 적용하면 기존의 대형 흡수탑 대비 상당한 공간과 에너지의 절감 효과가 기대된다.

• 한국생산제조학회지
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• 제21권4호
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• pp.588-592
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• 2012

This study concentrates the effect of hybridisation on the collapse mode and energy absorption for composite cylinders. The static collapse behavior of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell under quasi-static axial compressive load has been investigated experimentally. Eight different hybrids of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell were fabricated by autoclave. Eight types of composites were tested, namely, Al/carbon fiber/epoxy, Al/glass fiber/epoxy, Al/carbon-carbon-glass/epoxy, Al/carbon-glass-carbon/epoxy, Al/carbon-glass-glass/epoxy, Al/glass-glass-carbon/epoxy, Al/glass-carbon-glass/epoxy and Al/glass-carbon-carbon/epoxy. Collpase modes were highly dominated by the effect of hybridisation. The results also showed that the hybrid member with material sequence of Al-glass-carbon-carbon/epoxy exhibited good energy absorption capability.