• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.103-110
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• 2021

유연한 고무재료와 강재 보강판을 적층으로 구성한 탄성받침은 우수한 수직강성과 유연한 횡강성으로 교량의 내진보강용으로 널리 사용되고 있다. 무엇보다 시공이 간단하고 비용이 높지 않다는 장점을 지니고 있다. 고무재료의 한 종류인 합성고무는 천연고무에 비해 노화에 대한 저항성이 크지만 이 역시 다양한 열화요인으로 성능이 저하된다. 내진설계기준 및 내진성능평가요령에서는 이러한 노화의 특성을 반영하고 있지 않지만 관련 연구가 축적되면 이를 반영하는 것이 합리적이다. 합성고무를 대상으로 노화촉진시간과 노출시간을 변수로 하여 노화촉진시험을 수행하여 전단특성의 변화를 분석하였다. 노화가 진행될수록 최대전단응력과 전단변형율은 감소한다. 또한 동일한 전단변형률에서 전단강성이 크게 증가한다.

• Journal of the Korean Wood Science and Technology
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• 제47권3호
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• pp.344-359
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• 2019

Effects of various types of zeolite on the catalytic performance of hydrodeoxygenation (HDO) of bio-oil obtained from waste larch wood pyrolysis were investigated herein. Bifunctional catalysts were prepared via wet impregnation. The catalysts were characterized through XRD, BET, and SEM. Experimental results demonstrated that HDO enhanced the fuel properties of waste wood bio-oil, such as higher heating values (HHV) (20.4-28.3 MJ/kg) than bio-oil (13.7 MJ/kg). Water content (from 19.3 in bio-oil to 3.1-16.6 wt% in heavy oils), the total acid number (from 150 in bio-oil to 28-77 mg KOH/g oil in heavy oils), and viscosity (from 103 in bio-oil to $40-69mm^2/s$ in heavy oils) also improved post HDO. In our experiments, depending on the zeolite support, NiFe/HBeta exhibited a high Si/Al ratio of 38 with a high specific surface area ($545.1m^2/g$), and, based on the yield of heavy oil (18.3-18.9 wt%) and HHV (22.4-25.2 MJ/kg), its performance was not significantly affected by temperature and solvent concentration variations. In contrast, NiFe/zeolite Y, which had a low Si/Al ratio of 5.2, exhibited the highest improved quality for heavy oil at high temperature, with an HHV of 28.3 MJ/kg at $350^{\circ}C$ with 25 wt% of solvent.

• 대한건축학회논문집:구조계
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• 제35권3호
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• pp.43-48
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• 2019

Since the revision of the Rationalization of Energy Use Law, the spread of new and renewable energy in buildings has been promoted. In addition, the production of electric power and thermal energy is an important issue in the change of energy paradigm centered on the use of distributed energy. Among them, geothermal energy is attracting attention as a high-performance energy-saving technology capable of coping with heating / cooling and hot water load by utilizing the constant temperature zone of the earth. However, there is a disadvantage that the initial investment cost is high as a method of calculating the capacity of a geothermal facility by calculating the maximum load. The disadvantages of these disadvantages are that the geothermal energy supply is getting stagnant and the design of the geothermal system needs to be supplemented. In this study, optimization design of geothermal system was carried out using optimization tool. As a result of the optimization, the ground heat exchanger decreased by 30.8%, the capacity of the heat pump decreased by 7.7%, and the capacity of the heat storage tank decreased by about 40%. The simulation was performed by applying the optimized value to the program and confirmed that it corresponds to the load of the building. We also confirmed that all of the constraints used in the optimization design were satisfied. The initial investment cost of the optimized geothermal system is about 18.6% lower than the initial investment cost.

• 한국표면공학회지
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• 제54권3호
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• pp.119-123
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• 2021

SnO₂ single layer and SnO₂/Ag/SnO₂ (SAS) tri-layered films were deposited on the glass substrate by RF and DC magnetron sputtering at room temperature and then the effect of Ag interlayer on the opto-electrical performance of the films were considered. As deposited SnO₂ films show a visible transmittance of 85.5 % and a sheet resistance of 1.2×10⁴ Ω/□, the SAS films with a 15 nm thick Ag interlayer show a lower resistance of 18.8 Ω/□ and a visible transmittance of 70.6 %, respectively. The figure of merit based on the optical transmittance and sheet resistance revealed that the Ag interlayer in the SnO₂ films enhances the opto-electrical performance without substrate heating or annealing process.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.509-515
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• 2021

In this study, a pressure vessel for a heat pipe was fabricated by bonding a metal thin film using a polymer compound sheet. In order to confirm the applicability of the experimentally manufactured copper material thin heat pipe of 0.6 mm or less, the pressure resistance and effective thermal conductivity for pressure generated according to the type of the working fluid of the heat pipe were evaluated to suggest the commercialization potential of the thin heat pipe. As a result of evaluating the pressure resistance and effective thermal conductivity performance of the thin heat pipe, the following conclusions were drawn. 1) Using a PEEK-based polymer compound sheet, it was possible to fabricate a pressure vessel for a thin heat pipe with a pressure resistance of up to 1.0 MPa by bonding a copper thin film, and the possibility of commercialization was confirmed at a temperature below 120 ℃. 2) In the case of the effective thermal conductivity performance evaluation test, the effective thermal conductivity of ethanol was higher than that of FC72 and Novec7000, and in the case of ethanol, the maximum effective thermal conductivity was 2,851 W/mK at 3.0 W of heating.

• 전력전자학회논문지
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• 제26권6호
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.95-102
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• 2021

유연한 고무재료를 사용하는 탄성받침은 최근 교량의 내진보강용으로 많이 적용되고 있다. 그러나 다양한 요인에 의하여 고무재료의 노화가 진행되고 이로 인해 탄성받침의 전단강성에 변화가 생기고 이는 교량의 내진성능에 영향을 미친다. 천연고무를 대상으로 노화촉진시간과 노출시간을 변수로 하여 노화촉진시험을 수행하여 전단특성의 변화를 분석하였다. 노화가 진행될수록(노화촉진온도 및 노출시간이 증가할수록) 최대전단응력과 전단변형율은 감소한다. 또한 동일한 전단변형률에서 전단강성이 크게 증가한다. 이는 고무재료가 경화됨을 의미하며 탄성받침의 내진성능이 저하되는 것을 암시한다.

• 한국지열·수열에너지학회논문집
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• 제19권1호
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• pp.1-13
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• 2023

Many government in the world have conducted building energy performance certification program to reduce building energy consumption. In this study, a reference building and its HVAC system was modeled, and the energy load and consumption were estimated by the ECO2 program. The software is a simple building energy simulation program based on monthly calculated method. The building energy efficiency rating the the reference building was 1+ under baseline condition. The simulation results showed that the insulation performance slightly affected building energy load and consumption, but light density had a significant effect on them. The application of geothermal heat pumps gave improvement of building energy efficiency rating but it could not make it possible to get zero energy building(ZEB) certification. The ZEB 5 certification could be achieved by using photovoltaics, however getting better grade was difficult. The simulation results showed that the ZEB 4 certification, one grade higher than ZEB 5, could be attained by using more than one renewable energy source such as geothermal and solar energy in this study.

• 한국전자통신학회논문지
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• 제18권4호
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• pp.641-648
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• 2023

최근 4차 산업 혁명 중에서 인공지능의 급성장은 반도체의 성능 향상 및 회로의 집적을 기반으로 진보하였다. 전자기기 및 장비의 내부에서 연산을 돕는 트랜지스터는 고도화 및 소형화 되어 가며 발열의 제어 및 방열의 효율 개선이 새로운 성능의 지표로 대두되었다. DUT(Device Under Test) Shell은 트랜지스터의 검수를 위하여 정격 전류를 인가한 후, 임의의 발열 지점에서 전원을 차단한 상태에서, 방열을 통하여 트랜지스터의 내구도를 평가하여 불량 트랜지스터를 검출하는 장비이다. DUT Shell은 장비 내부의 방열 구조에 따라 동시에 더 많은 트랜지스터를 테스트할 수 있기 때문에 방열 효율은 불량 트랜지스터 검출 효율과 직접적인 관계를 갖는다. 이에 본 논문에서는 DUT Shell의 방열 최적화를 위하여 배치구조의 다양한 방법을 제안하고 전산유체역학을 이용하여 최적의 DUT Shell의 다양한 변형과 열 해석을 제안하였다.

• 한국수소및신에너지학회논문집
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• 제34권1호
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• pp.8-16
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• 2023

In this work, we report basic performance test results of a lab-scale three phase alternative current (AC) arc plasma torch system for plasma gas reforming applications. The suggested system primarily consists of three graphite electrodes inclined at 12.5° to the central axis, a 𝞥 150 mm cylindrical gas path and a three phase-60 Hz AC power supply. At air flow rate of 50 Lpm and arc currents of 100-175 A, test results revealed that plasma resistances were decreasing from 1.08 Ω to 0.53 Ω with the increase of plasma power from 9.3 kW to 13.8 kW, causing the decrease of power factor and increase of the line voltages. However, the injected air can be heated quickly up to the temperatures of >1,200℃ when injecting AC arc plasma powers of >10 kW.