• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.443-446
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• 2014

Recently the demand for natural gas as clean and safe energy due to concerns about global warming and interests in green ship is increasing. The dual fuel(DF) engine, one of environmentally friendly engines, is preferred for general merchant ships and power plants as well as LNG carriers. This is for the reasons of having higher efficiency and lower nitrogen and sulfur oxides emissions by operating on LNG fuel with a small amount of light fuel oil. In this study, the engine body vibration characteristics of 12V50DF in a generator set with engine-resilient-mounted, generator-rigid-mounted and flexible-coupling configuration are investigated through theoretical analysis and comprehensive vibration measurement. This analysis showed the dynamic behavior of engine excitation forces and seismic waves. And the suitable countermeasures for reducing vibration and safe operation are proposed.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.310-315
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• 1997

System-Integrated Modular Advanced Reactor (SMART), where major primary components such as modular helical steam generator and self regulating pressurizer are integrated into reactor vessel, is currently under development. The pressurizer is designed to control the primary pressure mainly with partial pressure of nitrogen gas and to maintain the fluid temperature as low as possible for the purpose of minimizing steam contribution. The steam generator (SG) is designed to produce super-heated steam inside tube at power operation. Because the in-vessel pressurizer and in-vessel SG are classified as the characteristic components of SMART, it is important to perform a steady state calculation of these components in order to evaluate the adoption of these components. A steady state analysis of the in-vessel pressurizer and in-vessel SG has been performed under normal power operation and the results show an acceptable performance of the components.

• Medical Lasers
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• 제8권1호
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• pp.28-31
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• 2019

Superficial fungal infections with dermatophytes, nondermatophyte molds, or yeasts are treated primarily with topical and/or systemic antifungal agents. Additional or alternative treatment modalities, particularly energy-delivering modalities, however, are used widely to induce fungicidal effects via selective photothermal reactions. In addition to light- or laser-based devices, plasma therapy also has antifungal properties. This report describes a Korean male patient with mycologically confirmed tinea pedis that was treated effectively with two sessions of nitrogen plasma treatment at one-week intervals using a plasma delivering system. Nitrogen plasma was prepared by loading a 0.28-ml inert nitrogen gas/pulse that was activated by a microwave generator. The other treatment settings were a nozzle diameter of 5 mm, pulse energy of 0.75 J, pulse duration of 7 msec, and two passes. One week after the first session of nitrogen plasma treatment, the patient exhibited marked reductions in scale and inflammation. One month after the final treatment, no clinical features of recurrence were found, and successive potassium hydroxide testing revealed negative results.

• 열처리공학회지
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• 제27권3호
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• pp.121-126
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• 2014

High-nitrogen Fe-18Mn-18Cr-N austenitic steels with higher yield strength have been recently developed and used for generator retaining rings because they have non-magnetic, high strength, high ductility, and good corrosion resistance. In the present study, a high-nitrogen Fe-18Mn-18Cr-0.61N austenitic steel was fabricated and then tensile and Charpy impact tests were conducted on them in order to investigate the effect of cold working on the mechanical properties. Although the yield and tensile strengths usually increased with cold working, the ductility and impact toughness significantly decreased after cold working. On the other hand, the high-nitrogen austenitic steel exhibited a ductile-brittle transition due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductile-brittle transition temperature obtained from Charpy impact tests could be remarkably increased by $60^{\circ}C$ after 20% cold working because of the enhanced cleavage-like brittle fracture.

• Environmental Engineering Research
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• 제25권2호
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• pp.251-257
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• 2020

This study was performed to verify the possibility of nitrification and denitrification in a single reactor. In batch type experiment, optimal point of experimental conditions could be found by performing the experiments. When supply location of microbubbles was located at half of width of the aeration tank and operating pressure of 0.5 bar, it was possible for zones in the aeration tank to be separated into anoxic and aerobic by controlling air suction rate according to operating pressure of the generator. To be specific, the concentration of dissolved oxygen (DO) in zone 1 and 2 of the aeration tank could be maintained as less than 0.5 mg/L. Also, in the case of concentration of oxygen in zone 3 and 4, the concentration of DO was increased up to 1.7 mg/L due to effects of microbubbles. In continuous flow type experiment based on the results of batch type experiments, the removal efficiency of nitrogen based on T-N was observed as 39.83% at operating pressure of 0.5 bar and 46.51% at operating pressure of 1 bar so it was able to know that sufficient air suction rate should be required for nitrification. Also, denitrification process could be achieved in a single reactor by using ejector type microbubble generator and organic matter and suspended solid could be removed. Therefore, it was possible to verify that zones could be separated into anoxic and aerobic and nitrification and denitrification process could be performed in a single reactor.

• 대한기계학회논문집B
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• 제30권2호
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• pp.170-176
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• 2006

A spark discharge aerosol generator using air as a carrier gas has successfully been applied to silver nanoparticle production. The spark discharge between two silver electrodes, which was periodically obtained by discharging the capacitor, produced sufficient high temperatures to evaporate a small fraction of the silver electrodes. The silver vapor was subsequently supersaturated by rapid cooling and condensed to silver nanoparticles by nucleation and condensation. The morphology of the generated particles observed by transmission electron microscope was spherical. The element composition of the nanoparticles was silver, which was determined by energy dispersive X-ray spectroscopy. The crystal phase of the particles spark-generated under air atmosphere was composed of silver and silver oxides phase, which was determined by Xray diffraction analysis. While the nanoparticles generated under nitrogen atmosphere had only silver phase. This XRD data indicates that some fraction of the evaporated silver vapor could be oxidized in air atmosphere by the reaction with oxygen. A stable operation of the spark discharge generator has been achieved. The size and concentration of the particles can be easily controlled by altering the repetition frequency, capacitance, gap distance and flow rate of the spark discharge system.

• 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.

• 대한기계학회논문집B
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• 제41권4호
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• pp.293-301
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• 2017

초임계 이산화탄소 발전사이클의 다양한 특성을 분석하기 위하여 Sub-kWe급의 소형 실험장치를 설계, 제작하였으며, 터보발전기를 개발하였다. 초임계 이산화탄소 발전용 터빈에서는 팽창비가 작고, 유량이 작기 때문에 터보발전기의 회전수가 높아지게 되고, 이에 따라 회전 부품의 선정, 터빈 공력설계, 축력 및 회전체 동역학 설계가 어려워지게 된다. 이에 터보발전기의 회전수를 줄이기 위하여 노즐의 여러 채널 중 1개의 노즐만 사용하는 부분유입 방법을 세계 최초로 초임계 이산화탄소 발전용 터보발전기에 적용하였으며, 회전체의 진동을 측정하여 부분유입 노즐을 적용함에도 회전체 안정성은 허용 범위내에 있음을 확인하였다.

• 한국결정성장학회지
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• 제13권5호
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• pp.205-210
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• 2003

스컬법에 의해 alexandrite-like cubic zirconia 단결정을 성장 시켰다. 스컬용융시 R.F generator는 35 ㎾, 2 MHz 였다. 단결정들은 전이금속이온인 Pr을 1 또는 1.5 wt%와 Nd를 0.5 또는 l wt%를 함께 첨가하여 성장시켰으며, 성장 후0.25 mm의 slice와 12 mm의 round brilliant cut으로 연마하였다. 연마석은 공기중 또는 질소분위기에서 $1000^{\circ}C$에서 2시간 열처리하였으며 optical absorption spectra($\lambda$ = 400∼700 nm)를 얻었다.

• 한국추진공학회지
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• 제21권2호
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• pp.26-31
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• 2017

고체 추진제의 환경적 문제는 고체 로켓에서 중요한 이슈로 부각되고 있다. 예를 들어 고체추진제의 산화제인 ammonium perchlorate (AP)는 염산과 같은 독성 가스와 대기 오염을 발생시켜 환경적 문제를 야기한다. 산화제 중 N-guanylurea dinitramide (GuDN)는 높은 성능과 압력 지수를 가지고 있으며, 가스발생기 추진제에서 연소하는 동안 친환경적인 연기를 배출하는 성질을 가지고 있기 때문에 환경친화적으로 효과적인 후보 물질이다. 본 논문에서는 가스발생기 추진제로서 특성에 대하여 이론적 분석, 추진제 제조공정성, 추진제 경도 특성 및 연소특성에 대하여 연구하였다.