• Nuclear Engineering and Technology
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• 제3권1호
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• pp.21-31
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• 1971

금속의 소성변형에 필요한 일의 일부는 전표면자유에너지 (Total Surface Free Energy)의 변화에 소모된다. 전표면자유에너지 변화는 비표면 자유에너지 (Specific Surface Free Energy)에 의해 변화하며 비표면자유에너지는 분위기에 따라 달라 진다. 열역학적규명, 체적불변율과 흡착으로 인한 두 개의 판이하게 다른 강화 혹은 약화를 초래하는 전위(Dislocation) 상호작용기구를 기반으로 금속의 소성변형으로 인한 가공경화, 응력 및 에너지에 미치는 분위기의 영향을 이론식으로 도출했다. 이론식은 진공중금속표면장력 (${\gamma}$$_{s}$), 개면장력 (${\gamma}$$_{se}$ ), 포면전위밀도($\rho$$_{s}$), 내부전위 밀도($\rho$$_{i}$)와 표면노출율(f)의 함수로 표시할 수 있었다. 이론식을 이용하여 각기 다른 분위기내에서의 금속의 기계특성을 예측 비교해봤다.다.다.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.317-333
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• 2022

Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

• Journal of Biosystems Engineering
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• 제36권3호
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• pp.217-222
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• 2011

This study was carried out in order to reduce the amount of underground water which is used in the double layered single span plastic greenhouse for retaining heat. For this research, two plastic green houses of the double layered single span plastic greenhouse were installed. There was equipped of internal small tunnel for keeping warm air in the interior of the house. Then the internal small tunnel for keeping warm air was fitted with PVC duct of 50 cm in diameter filled with subsurface water. The surplus solar energy in the greenhouse was stored in the water in the PVC duct. Four FCUs (Fan Coil Unit), which has the capacity of 8,000 kcal per hour, were installed in the middle of the house, and a circulation motor in heat storage water tank was operated from 10:30 a.m. to 16:00 p.m. in order to circulate water between the water tank and the FCUs. Consequently about 5 degrees celsius could be maintained in the interior of the internal small tunnel for keeping warm air with the external temperature of lower than minus 5 degrees celsius. It appeared that the alteration of an internal temperature of the house was flexible depending on the sunlight during daytime. To prevent the water freezing, mixing antifreezing liquid in the water or operating FCU continuously was needed. Also, in order to use the surplus solar thermal energy on plastic green house of water curtain system efficiently, storing the surplus heat during daytime simultaneously finding a method of using water curtain systematic underground water happened to be important. As a result of this research, when the house's interior temperature is below zero the operation of FCU appeared to be impossible. Considering the amount of water used in the house with water-curtain-heating system is 150~200 ton per day, using the system mentioned in this research showed that reducing the underground water more than 80% in order to maintain the internal temperature as the level of 5 degree celsius at the extreme temperature of minus 5 degrees celsius.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4671-4678
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• 2022

The purpose of this comprehensive research is to observe the impact of scintillator crystal type on entire detection process. For this aim, MCNPX (version 2.6.0) is used for designing of a physical plastic scintillation detector available in our laboratory. The modelled detector structure is validated using previous studies in the literature. Next, different types of plastic scintillation crystals were assessed in the same geometry. Several fundamental detector properties are determined for six different plastic scintillation crystals. Additionally, the deposited energy quantities were computed using the MCNPX code. Although six scintillation crystals have comparable compositions, the findings clearly indicate that the crystal composed of PVT 80% + PPO 20% has superior counting and detecting characteristics when compared to the other crystals investigated. Moreover, it is observed that the highest deposited energy amount, which is a result of the highest collision number in the crystal volume, corresponds to a PVT 80% + PPO 20% crystal. Despite the fact that plastic detector crystals have similar chemical structures, this study found that performing advanced Monte Carlo simulations on the detection discrepancies within the structures can aid in the development of the most effective spectroscopy procedures by ensuring maximum efficiency prior to and during use.

• 한국공간구조학회논문집
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• 제6권2호
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• pp.131-136
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• 2006

It is important to evaluate energy absorption capacity of frames required during a design earthquake. An inelastic computer analysis based on mathematical modelling of energy absorbing frames and elements makes it possible to evaluate required energy absorption capacity. But such an analysis sometimes consumes much computation time particularly in case of complicated structural system. This paper presents a proposal to predict energy absorption of multi-bent steel frames by simple equivalent linear method.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.186-186
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• 2015

We have introduced multifunctional ITO single thin films formed by normal sputtering system equipped with a plasma limiter which effectively blocks the bombardment of energetic negative oxygen ions. MFSS ITO also possesses high gas diffusion barrier properties simultaneously low resistivity even it deposited at room temperature without post annealing on plastic substrate. Nano-crystalline enhancement by Ar energy has energy window from 20 to 30 eV under blocking NOI condition. Effect of blocking NOI and optimal Ar energy window enhancement facilitate that resistivity is minimized to $3.61{\times}10^{-4}{\Omega}cm$ and the WVTR of 100 nm thick MFSS ITO is $3.9{\times}10^{-3}g/(m^2day)$ which is measured under environmental conditions of 90% relative humidity and 50oC that corresponds to a value of ${\sim}10^{-5}g/(m^2day)$ at room temperature. The multifunctional MFSS ITO with low resistivity, and low gas permeability will be highly valuable for plastic electronics applications.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.173-181
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• 1997

To investigate the effects of haunch repair on the system seismic performance of steel moment-resisting frames (steel MRFs), a case study was conducted for a 13-story frame damaged during the 1994 Northridge earthquake. It was assumed that only those locations with reported damage would be repaired with haunches. A new analytical modeling technique for the dual panel zone developed by the author was incorporated in the analysis. Both the inelastic static and dynamic analyses did not indicate detrimental side effects resulting from the repair. As a result of the increased strength in dual panel zones, yielding in these locations were eliminated and larger plastic rotation demand occurred in the beams next to the shallow end of the haunches. Nevertheless, the beam plastic rotation demand produced by the Sylmar record of 1994 Northridge earthquake was still limited to 1.7% radians. The repair resulted in a minor increase in earthquake energy input. In the original structure, the panel zones should dissipate about 80%(for the Oxnard record) and 70%(for the Sylmar record) of the absorbed energy, assuming no brittle failure of moment connections. After repair, the energy dissipated in the panel zones and beams were about equal.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2000년도 전지기술심포지움
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• pp.51-62
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• 2000

Large plastic Li-ion (PLI) cells (25 to 28-Ah) were fabricated for an EV application. The 28-Ah cells showed high specific energy (160 Wh/kg), high specific power (526 W/g), excellent round-trip energy efficiency $(92\%)$, and low self-discharge rate ($6\%$ in 30 days). A 25-Ah cell of an earlier design showed good cycle life of up to 750 cycles at $100\%$ DOD to $80\%$ of its initial capacity, while cycle life test of a 28-Ah cell of a later design is in progress. Preliminary safety tests were also carried out using 6-Ah cells of a similar electrode design giving very encouraging results for development of a safe hish-energy density PLI battery for EV application.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.261-268
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• 1999

The seismic performance of precast concrete panel structures tested previously has been evaluated in this paper. Hysteretic curves of test specimens are idealized to elasto-plastic curves to get reliable yielding and ultimate displacements. For the idealized curves, ductility and energy dissipation capacity of specimens have been evaluated using a few guide lines. In addition, the strength capacity of specimens is checked for the strength demand caused by the design earthquake load including overturning moment effects. The result shows while the strength of specimen with joint box for vertical continuity is little bit lower than that of specimen connected by welding, the ductility of the former is higher than that of the latter. The energy dissipation ratios of PC specimens are ranged from 83% to 96% of that of Re specimen and the average of those are shown 90%.

• 한국공간구조학회논문집
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• 제23권3호
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• pp.45-55
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• 2023

The purpose of this study has a purpose to evaluate shear ability, ductility and energy dissertation of specimens that is to be applied to jacket using wrapping method. The experiments was conducted as a condition that simultaneously applied axial load and transverse force. The results of experiments represent story-displacement ratio, the stiffness, energy dissertation, plastic rotation which mean seismic resistance ablity on structure. And It represents the form of crack ditribution and failure in extreme stages. Based on the results of this experiment, Design examples are given to show the performance evaluation for the column reinforcing of old school buildings using nonlinear analysis is going to be conducted. Therefore, it is possible to apply the seismic retrofit method to public facilities.