• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.36-52
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• 2021

As the application of nano-satellites constellation increases worldwide in the wake of New Space era, there is growing demand for the development of thrusters for precise attitude and orbit control of small satellites. Field Emission Electric Propulsion(FEEP) thruster uses a liquid metal as a propellant and accelerates the ionized liquid metal through a strong electric field at the tip of the metal surface. FEEP thruster technology is suitable for nano-satellites which require various missions for attitude and orbit control, because it provides thrust ranging from 1 µN to 1 mN with high specific impulse up to about 10,000 s and can be miniaturized due to its simple structure. In this paper, the basics of FEEP thrusters are introduced, then the current status of research and development of FEEP thrusters are presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5763-5768
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• 2015

A relief valve is a mechanical element to keep safety by controlling high pressure. Usually, the high pressure is relieved by using the spring force and letting the fluid to flow from another way out of system. When its normal pressure is reached, the relief valve can return to initial state. The relief valve should be designed for smooth operation and should satisfy the structural safety requirement under operating condition. The commercial software ANSYS/WORKBENCH is utilized for flow and structural analysis. Very high pressure may cause structural problem due to severe stress. The study suggests the design satisfying the structural design requirement

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.705-713
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• 2004

The objectives of this study were to evaluate the fluoride release and the change of surface roughness of fluoride releasing restorative materials after toothbrush-dentifrice abrasion. Seven commercially available fluoride releasing restorative materials (Fuji II LC Improved: FL, Compoglass F: CG, Dyract AP: DR, F2000: FT, Ariston: AT, Tetric: TR, and Gradia: GD) were selected as experimental materials. The results obtained were summarized as follows: 1. The AT, FL, and CF groups produce an initially large burst of fluoride release and comparatively low but continuous release of fluoride. But other groups produce no initial burst of fluoride and levels of release remain relatively constant. 2. The rate of fluoride release remains steady state after 40 days. The results of Tukey's test (P<.05), the fluoride release showed the order of decreasing rank as follows: AT > FL > compomers > TC and GD. 3. The surface roughness indicated that the highest value was observed in the FT group and the lowest value was observed in the CF group. The surface roughness of Tukey's test showed the significant differences between groups of FT, AT and FL and groups of CF, DR, GD and TC (P<0.05).

• Korean journal of applied entomology
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• v.47 no.3
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• pp.255-263
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• 2008

A wax-typed pheromone dispenser has been developed and applied to control outbreak of the oriental fruit moth, Grapholita molesta, in apple orchard. To optimize its application technique, this study analyzed effect of different amounts of the pheromone dispenser on mating disruption('MD') of G. molesta. Different pheromone dispenser amounts significantly influenced the MD effect assessed by cumulative male adult catches monitored respectively by sticky delta trap and food trap, and resulted in differential damage on host plants. In a field test during entire growing season, a standard amount(120 g per 0.117 ha) of wax-typed pheromone dispenser was proved to be effective to suppress outbreak of G. molesta adults and to prevent host plant damage as much as a current commercial MD product($Isomate^{(R)}$). This study also demonstrated an effectiveness of deployment of food trap barriers around MD-treated area to prevent immigration of mated females from outside untreated areas. These results indicate that the wax-typed pheromone dispenser can be applied to control field G. molesta populations and its co-application with fuod trap barriers would be optimal to maximize MD efficacy.

• Korean journal of applied entomology
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• v.46 no.3
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• pp.349-356
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• 2007

Three active components (Z8-12:Ac, E8-12:Ac, and Z8-12:OH) are known in sex pheromone of the oriental fruit moth, Grapholita molesta, and have been commercially available to apply for population monitoring and mating disruption. However, there have been variation among commercial products in pheromone composition and amount impregnated in each pheromone releaser. This study was performed to optimize factors influencing on pheromone monitoring of G. molesta by analyzing pheromone composition/amount, effective period of releaser, and trap type/placement in apple trees. High purity of Z8-12:Ac component was effective to attract males, in which 96% or more of cis acetate isomer component appeared to be optimal composition. Pheromone amounts ($0.01-1\;{\mu}g$) impregnated in each rubber dispenser did not give significant effect on monitoring during 90 days from June to August. "Delta" trap was much more efficient than "cone" trap to collect males. Trap installation was another factor, in which placing traps at canopy level was much efficient than at trunk or ground levels. Pheromone trap monitoring with these optimal factors indicated three to four adult peaks from June to September in addition to high overwintering population from April to May in pesticide-applied orchards in Andong, Korea.

• ETRI Journal
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• v.7 no.2
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• pp.49-58
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• 1985

본 고는 교환기에서 방출되는 전계 및 자계의 허용 규제치와 외부에서 들어오는 전계 및 자계에 대해 교환기가 얼마나 정상적인 동작을 할 수 있는가를 규정하고 있는 피방해 감도(EMC), 교환기에 의한 EMI 및 주변장치에서 발생하는 전자계의 규제에 대해 서술하고 이에 따른 측정 방법을 제시한다.

• Journal of the Korean Chemical Society
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• v.44 no.4
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• pp.343-349
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• 2000

Volatile Organic Compounds(VOCs) emitted form electronicSince toluene, xylene, cyclohexanone, and benzofuran will bring on the deleterious smell and the health risk, eventhough very small amount of these areexposed to human body, quantitative analysis was achieved by GC-MS system. As a result of these analyses, except PCB(CEM-1) of which is one of the electronic parts, the left of electronic parts represented, imme-diately form 30 minutes to 1 hour after heating, the trends that toluene, xylene, cyclohexanone and phenol were consecuticely emitted very high. and toluene, xylene, phenol, cyclohexanone, and benzofuran from most of the electronic parts were emitted very frequently within the measuring period. Finally, Trans of electronic parts showed the highest concentration of emission, and xylene(550~2482 ${\mu}g/m^2$) was the most noticeably emitting compound of VOCs.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.104-104
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• 1993

시방성 제제에 대한 연구는 주로 제제학적 수단에 의한 약효의 지속화로서 제제설계상 제형개발 및 투여제형에서의 약물방출 조절로 체내의 유효 혈중농도를 유지한다. 이에 약물 방출 조절용 물질의 하나로서 체내 분해가 가능하고 독성이 없는 생체 고분자인 Chitosan이 약물방출 담체로서 양호함에 착안하여 약물의 서방화를 기하고자 본 실험에 착수 하였다. 모델 약물로서는 sulfamethoxazole, acetaminophen, sylimarin을 사용하여 chitosan gel 과 혼합비를 달리하여 고형 문산체를 조제하고 이것을 formaldehyde, glutaraldehyde, 1acetaldehyde, butylaldehyde 4종의 aldehyde를 사용하여 농도에 따른 가교화가 in vitro에서의 약물용출에 미치는 영향을 검토하였으며, 또한 위장을 거쳐 소화효소 또는 장내미생물 효소에 의한 chitosan 분해로 약물 방출의 촉진을 실험한바 지견을 얻었기에 보고한다.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.580-587
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• 1995

1979. 3.28 미국 TMI-2의 사고를 계기로 개발된 증상기준 비상운전절차서는 고리 3,4/영광 1,2호기의 경우 '92. 2에 개정된 ERG-18를 근거로 하여 각 발전소 운전담당 자들에 의하여 확인 및 검증 (Verification S Validation) 작업을 통하여 금년부터 본격적으로 적용되기에 이르렀다. 그러나 비상운전절차서의 특성상 리 발전소별 특정 설정치의 계산에서 어려움을 겪었으며 아직도 재확인 작업을 통한 최적화 여지가 상 당부분 잔존하고 있다. 여기어서는 고압발전소인 고리-3,4/영장-1,2호기 비상운전절차서에 있어서 증기발생기에 공급되는 정상 밋 비상급수의 전체 상실사고시 노심 노출 방지 및 노심 열 제거를 위해 적응되는 기능회복절차서의 "2차 열제거원 상실시 조치" 중 방출 및 충전 운전의 성공적 시작점을 계산, 개정된 비상운전절차서와 비교하여 특정 발전소의 방출 및 충전 운전 설정치를 제시하였고, 이러한 결과로부터 현재 보수적으로 설정된 값의 완화를 유도하여 방출 및 충전 운전 시작전, 운전원으로 하여금 급수확보를 시도할 수 있는 시간여유의 연장을 도출할 수 있었다.도출할 수 있었다.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.48.2-48.2
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• 2016

태양계의 행성간 공간에는 수많은 티끌들이 흩어져 있다. 이들의 존재는 유성, 우주 탐사선의 검출기, 황도광 관측 등으로 확인되고 있으나, 이 티끌들의 수명이 길어야 수백만년에 불과하기에 태양계에는 지속적으로 티끌을 공급하는 기원천체가 있어야 한다. 최근의 광학적 (Yang & Ishiguro, 2015), 역학적 연구는 ~90% 이상의 행성간 티끌들이 혜성에서 방출되었을 것이라 추정하기에 이르렀다. 이러한 상황에서, 본 연구에서는 행성간 티끌구름의 구체적 양상을 설명하려는 목적으로 혜성에서 방출된 티끌들이 태양계에서 겪게 되는 역학 진화를 수치 계산을 통하여 추적하였다. 우리는 다양한 혜성 궤도 분포를 골고루 대표할 수 있도록 실제 혜성 중에서 대표 혜성들을 선정하고, 관측에 기반한 티끌 방출 모형을 이용하여 다양한 크기의 가상적 티끌을 이들 혜성에서 방출시켰다. 태양의 복사에 의한 끌림힘, 8개의 행성에 의한 중력 섭동을 고려하며 이 티끌들의 궤도 진화가 추적되었다. 티끌들의 최종 종착지가 살펴졌고, 정상 상태를 가정하고 행성간 티끌구름을 구성하여 실제 관측되는 티끌구름과 비교하였다. 이번 발표에서는 혜성에 의한 티끌공급량과 내행성계의 티끌 유출입량, 내행성계 티끌구름의 크기도수분포, 티끌구름의 궤도 요소 분포, 황도광의 밝기 분포 등이 수치 계산 결과와 비교되어 설명될 것이다.