• 한국군사과학기술학회지
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• 제27권3호
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• pp.428-435
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• 2024

The important factors in the design of the gun propellant are impetus, flame temperature and pressure. In this paper, we considered a nitrocellulose based propellant composition that replaced sensitive NG(Nitroglycerin) with RDX(Cyclotrimethylenetrinitramine) and DEGDN(Diethylene glycol dinitrate) which high energy and low sensitivity. Particle size and content of RDX are the two main factors that affect the burning stability of RDX-based propellants. Among them, the characteristics of the propellant according to the particle size of RDX were confirmed. The relative combustion rate(R.Q., Relative Quickness) of the propellant changed according to the RDX particle size, and internal ballistics of properties of propellant were also varied. The particle size of RDX can be confirmed as a major factor in the combustion and internal ballistics characteristics of the propellant.

• 대한화학회지
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• 제40권8호
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• pp.557-564
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• 1996

각기 다른 양이온$(Na^+, Li^+, K^+, NH_4^+)$을 구조이성질체인 일련의 합성 올리고당에 첨가함으로써, 양이온의 결합정도가 올리고당의 연결위치에 따라 달라지리라는 것을 FAB CAD MS/MS(Fast Atom Bombardment Collision Activated Dissociation Mass Spectrometry/ Mass Spectrometry)를 이용하여 안정성 측면에서 연구하였다. 알카리 양이온화된(cationized) 올리고당들은 양성자화(protonated)된 형태보다 더 큰 안정성을 나타내어 -40 eV의 충돌 에너지 수중에서 연결부위와 작용기들이 분절된 스펙트럼형태를 보인 반면, 양성자화된 올리고당은 -10 eV에서 에서 같은 정도의 분절을 보였다. 첨가된 양이온 중, 칼륨 양이온이 첨가된 올리고당이 다른 것에 비해 안정화되어 triple quadrupole기종의 허용에너지 조건하에서는 분절이온을 생성하지 않는다. 다른 양이온화된 올리고당들은 충돌기체인 argon의 압력이 0.8mTorr 상태에서 양이온의 종류에 따라$Nap^+>Li^+>NH_4^+$순으로 안정성을 나타내었다. 올리고당과 결합하는 금속양이온들은 질소를 포함하고 있는 아미노당에 위치하며, 이는 아미노당을 포함하는 분절이온마다 각 양이온에 해당하는 만큼의 질량이 이동된 분절피크들이 나타나는 것으로 설명 가능하다. 또한 양이온화된 것이 양성자화된 것보다 더 큰 안정성을 지니는 이유는 금속 양이온과 아미노당의 N-acetyl 작용기 및 fucose의 산소 사이에 크라운에테르 형태의 결합을 형성하는 것으로 설명할 수 있다. 이 때 참여한 금속 양이온의 크기 및 연결위치-이성질 부분의 구조적 형태에 따라 결합정도의 차이를 보여 각기 다른 분절스펙트럼의 형태를 나타내며 안정성면에서도 1-6>1-4>1-3 연결위치의 순으로 나타났다.

• 한국해양환경ㆍ에너지학회지
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• 제16권3호
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• pp.181-188
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• 2013

인간의 인위적 활동에 의한 이산화탄소의 배출 증가는 지구 온난화의 원인 중 하나로 알려져 있으며, 기상이변 등과 같이 지구 환경에 막대한 영향을 미치고 있다. 이로 인해 최근 들어 이산화탄소 배출량을 규제하기 위한 움직임이 활발해지고 있다. 또한 배출된 이산화탄소의 환경영향을 평가하기 위해, 일본 조선학회 산하의 IMPACT 위원회에서는 자연의 개발로 인한 환경영향과 경제성을 동시에 고려하여 평가할 수 있는 포괄적 지표인 Triple I (III)를 제안하고 있다. 본 연구에서는 III를 적용하여 컨테이너 선박의 운항 시 배출되는 이산화탄소로 인한 환경영향 및 경제성에 대해 생애주기 평가를 통해 정량적으로 비교하였다. 또한 선박의 규모 변화 및 운항 항로의 변경에 따른 포괄적 환경영향평가를 실시하였다. 결과적으로 선박의 운항에 의한 포괄적 환경영향평가는 선박의 규모보다는 이산화탄소 배출량과 밀접한 선박의 운항 항로에 보다 더 민감한 것으로 판단되었다.

• 한국농공학회논문집
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• 제60권2호
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• pp.85-93
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• 2018

This study investigated the structural behavior and field applicability of sandwich type GFRP arches with polymer mortar in core. As a result, in case of crack loading and failure loading, total strains at crown were the highest; the fracture strain at crown was 0.01690, which is 4.2 times greater than the fracture strain (0.004) of cement concrete. The 3 % deflection load was 17.42 kN, the flexural strength was $163.98{\times}10^{-3}GPa$, and the flexural elastic modulus was 11.884 GPa. From load-deflection relationship up to 3.5 % deflection, 3D analysis results and experimental values were observed to be almost identical. It was considered reasonable to set a deflection rate limit to be 3 % for structural safety purpose. The standard external flexural strength of semicircular arch used in this study was approximately 2.64 times higher than that of hume pipe (2 type standard) and tripled composite pipe. The external pressure strength at fracture was approximately 1.57 times higher than that of hume pipe. It was confirmed that the implementing semicircular arch had mechanically more advantage than the circular pipe. Optimum member thickness was 8~53 mm according to arch radius of 450~1,800 mm and cover depth of 2~10 m. It was found that the larger strength could be obtained even if the thickness of member was smaller than that of concrete structure. In field application study, figures and equations were derived for obtaining applicable cover depth and optimum member thickness according to loading conditions. These would be useful data for design and manufacture of sandwich type semicircular arch.

• Current Photovoltaic Research
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• 제2권4호
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• pp.168-172
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• 2014

Under concentrated illuminations, the solar cells show higher efficiencies mainly due to an increase of the open circuit voltage. In this study, InGaP/InGaAs/Ge triple-junction solar cells have been grown by a low pressure metalorganic chemical vapor deposition. Photovoltaic characteristics of the fabricated solar cells are investigated with a class A solar simulator under concentrated illuminations from 1 to 100 suns. Ideally, the open circuit voltage should increase with the current level when maintained at the same temperature. However, the fabricated solar cells show degraded open circuit voltages under high concentrations around 100 suns. This means that the heat sink design is not optimized to keep the cell temperature at $25^{\circ}C$. To demonstrate the thermal degradation, changes of the device performance are investigated with different bonding conditions and heat sink materials.

• 한국세라믹학회지
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• 제48권6호
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• pp.487-492
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• 2011

The effect of the application of lanthanum strontrium manganite and yttria-stabilized zirconia (LSM-YSZ) nano-composite fabricated by pulsed laser deposition (PLD) as a cathode of solid oxide fuel cell (SOFC) is studied. A gradient-structure thin-film cathode composed of 1 micron-thick LSM-YSZ deposited at an ambient pressure ($P_{amb}$) of 200 mTorr; 2 micron-thick LSM-YSZ deposited at a $P_{amb}$ of 300 mTorr; and 2 micron-thick lanthanum strontium cobaltite (LSC) current collecting layer was fabricated on an anode-supported SOFC with an ~8 micron-thick YSZ electrolyte. In comparison with a 1 micron-thick nano-structure single-phase LSM cathode fabricated by PLD, it was obviously effective to increase triple phase boundaries (TPB) over the whole thickness of the cathode layer by employing the composite and increasing the physical thickness of the cathode. Both polarization and ohmic resistances of the cell were significantly reduced and the power output of the cell was improved by a factor of 1.6.

• 에너지공학
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• 제10권3호
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• pp.188-194
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• 2001

정유공장으로부터 발생하는 중잔사유를 이용하는 가스화 복합발전 플랜트에 대한 공정모사를 수행하였다. 가스화 복합사이클의 발전계통을 모델링하기 위해 본 연구는 MS7001FA 가스터빈이 공기분리장치와 연계되어 있고, 공기분리장치를 위한 공기 추출과 공기분리장치로 부터의 질소희석이 이루어진다고 가정하였다 가스터빈의 폐열은 삼중압력의 페열회수 증기발생장치로부터 회수하였다. 가스터빈의 합성가스 연료는 중잔사유가 Shell 가스화 및 Sulfinol-SCOT-Claus 공정을 거쳐 발생되는 것으로 가정하였다. 공정 최적화 결과로부터, 가스화 복합사이클의 효율이, 질소 희석이 없는 경우와 있는 경우에 대해, 공기추출비 20% 또는 40∼60%에서 가장 우수했다. 그리고, 연소지의 질소희석은 NOx 저감에 매우 바람직하고 현저한 효과를 가져오나, 반면에 가스터빈의 운전조건을 써지 조건에 가깝게 이동시킴을 알 수 있었다.

• 대한화장품학회지
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• 제24권3호
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• pp.116-122
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• 1998

It is well known that all-trans-retinol is not only very unstable in heat, light, air, and water, but also skin-irritant despite a good anti-wrinkle effect. Therefore, it is very difficult to stabilize retinol and make the safe retinol containing cosmetics by using a certain concentration of retinol with real effect. In order to dissolve these problems and apply retinol for skin care cream, firstly retinol is to be encapsulated in the vesicle called Liposphere (pseudo-liposome) which is made by homogenizing under high pressure the mixtures of lecithin, retinol, caprylic/capric triglyceride, and hydroalcoholic solution ; and then this retinol containing Liposphere is to be intercalated in lamellar liquid crystal layer which is prepared by emulsifying in an optimal ratio the mixtures composed of non-ionic emulsifier (cetearyl glucoside, sorbitan stearate & sucrose cocoate etc), cetearyl alcohol, stearic acid, cholesterol, and ceramide. In addition, the stability of the retinol containing oil in water cream by adding the polymeric emulsifier such as acrylate /C10-30 alkyl alkylate crosspolymer is to be ensured even at 55 C. Retinol containing oil in water cream prepared through above procedure could be very stable at 45 C for at least 50 days. The structure identification of lamellar liquid crystal was determined using polarized light microscope and electron microscope Conclusively, we could make the very stable retinol containing oil in water cream by triple procedure, that is, encapsulation of retinol in Liposphere, intercalation of retinol in lamellar liquid crystal layer, and assurance of the high temperature stability of cream even at 55 C.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.828-836
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• 2008

To develop an engineering-model of hydrogen-fueled ultra-micro combustor for Ultra Micro Gas Turbine(UMGT), we reviewed and summarized the problems in downsizing combustors, and determined a suitable burning method. The key issue to actualize practical ultra-micro combustors is reducing heat loss from the combustor to compressor and turbine. The reduction of heat loss was discussed from 3 different viewpoints; heat-insulation material, high-space-heating-rate combustion, and combustor-insolated gas turbine structure. Use of heat-insulation material induced the heat loss reduction to the surroundings. The heat loss ratio decreased substantially in reverse proportion to space heating rate, leading the idea that it could be reduced by burning at a high space heating rate. By settling the combustor insolated from the compressor and turbine, the heat transfer from the combustor to the compressor and turbine becomes smaller. For a selection of the suitable burning method, comparison between 2 burning methods, flat-flame and swirling-flamer types, was conducted. Synthetically the flat-flame burning method was confirmed to be more suitable for ultra-micro combustors than latter one. Base on them, an engineering-model of hydrogen-fueled flat-flame ultra-micro combustor was developed. To obtain high overall heat-insulation, heat-resistant and strength, the engineering-model combustor had triple layer structure with an advanced ceramic, a heat insulation material and a stainless steel. To simplify heat transfer issue in the combustor, it was isolated from the other components. Furthermore it was designed by considering structure, size, material, velocity, pressure loss and prevention of flashback.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.723-732
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• 2022

Cracking ammonia inside solid oxide fuel cell (SOFC) stack is a compact and simple way. To prevent sharp temperature fluctuation and increase cell efficiency, the decomposition reaction should be spread on whole cell area. This leading to a question that, how does anode thickness affect the conversion rate of ammonia and the cell voltage? Since the 0D model of SOFC is useful for system level simulation, how accurate is it to use equilibrium solver for internal ammonia cracking reaction? The 1D model of ammonia fed SOFC was used to simulate the diffusion and reaction of ammonia inside the anode electrode, then the partial pressure of hydrogen and steam at triple phase boundary was used for cell voltage calculation. The result shows that, the ammonia conversion rate increases and reaches saturated value as anode thickness increase, and the saturated thickness is bigger for lower operating temperature. The similar cell voltage between 1D and 0D models can be reached with NH₃ conversion rate above 90%. The 0D model and 1D model of SOFC showed similar conversion rate at temperature over 750℃.