• 전기의세계
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• v.24 no.6
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• pp.35-38
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• 1975

금속과 원소반도체의 접촉으로 이루어진 점접촉트란지스터를 출발점으로 한 P-N접합트란지스터는 4반세기동안 반도체전자 소자의 중심이었다. 이와 같은 반도체소자는 단결정반도체의 특성을 이용한 것으로 그 제작에 있어 거의 완전에 가까운 결정구조와 극도의 화학적순수성이 요구되는 것이다. 이와 같은 요구조건은 접합형 반도체소자제작에 큰 제한을 주게 된다. Gunn Diode, Impatt Diode등으로 반도체소자는 Bulk형식의 것이 각광을 받게 되었으며 MOS형식의 FET에 이르러 신기원을 이루게 되었다. 이리하여 MOS기술은 Sapphire기반을 도입함으로써 SOS기법으로 발전을 거듭하게 되었다. 그러나 정질반도체의 이용이라는 근본적 개념에서는 이탈치못하고 있다. 이상과 같은 정질반도체소자에 대응하여 반대적 입장에서 불순물농도의 영향이 적은 비정질반도체의 연구가 70년이후 미국을 중심으로 활발하게 전개되고 있다. 그 연구 및 개발결과는 2년마다 이루어지는 액체비정질반도체국제회의에서 종합되고 있다. 이 분야에서의 연구는 1968년 Ovshinsky가 비산화물 Chalcogenide glass 비정질박막에서의 빠른 응답속도의 양극대칭성 Switching 현상 발견을 계기로 신국면을 개척하게 된 것이다. 이들 비정질반도체에 대한 물성론적 흥미와 응용면에 관한 기대로부터 전도기구의 해명과 응용회로의 개발연구가 급속히 진전되고 있다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.33-35
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• 2019

해상구조물은 그 특성상 해상에서 고립되어 있고, 액체상태 또는 가스 상태의 탄화수소 등을 다루고 있어 사고발생시 대형사고로 이어질 가능성이 크다. 이에 해상구조물에는 유엔해양법협약에 따라 500m라는 넓이의 안전수역이 설정되어 있으며 추가로 설정되는 제한 수역은 명확한 근거 없이 상이한 넓이로 설정되어 있다. 이에 본 연구에서는 선박의 조종성능 및 해상구조물에서 다루는 화물의 고유한 위험특성을 파악하여 표준화된 안전수역을 설정하는 방안을 제시하고자 한다. 이에는 국제해사기구의 조종성능기준인 선회경의 크기제한, 초기선회성능, 정지성능 등이 있다. 본 연구는 정량화된 안전수역 및 제한수역 설정 등에 대한 기준을 제시하는 데 도움을 줄 수 있을 것으로 사료된다.

• Journal of Plant Biotechnology
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• v.47 no.2
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• pp.179-184
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• 2020

Embryogenic calli from Codonopsis lanceolata L. were cultured in MS liquid media and supplemented with various concentrations of primary carbon sources to study the effects of carbohydrates and osmoticum on somatic embryogenesis and somatic embryo morphology. Sucrose, glucose, and a combination of 3% sucrose and various concentrations of sorbitol or mannitol as osmoticum were used as carbon supplements. The maximum number of somatic embryos per flask was greater in media exclusively supplemented with 3% sucrose (128.29) than exclusively glucose-supplemented media (47.67) and either supplement combination of 3% sucrose and osmoticum (95.67 with mannitol and 114.00 with sorbitol). The number of somatic embryos gradually decreased in media with increasing concentrations of combined osmoticum supplement. Decreases also occurred in the highest concentrations of sucrose- and glucose-supplemented media. The total frequency of somatic embryos with two cotyledons was slightly higher in medium with 3% + mannitol (24.09%) compared with exclusively sucrose (21.52%), glucose (21.22%), or 3% sucrose + sorbitol (22.13%). As concentrations of sucrose and glucose increased, the occurrence of two cotyledons and trumpet cotyledons gradually decreased and the occurrence of polycotyledon and globular stage embryos increased. Furthermore, as concentrations of 3% sucrose and osmoticum increased, the occurrence of trumpet cotyledon and globular stage embryos increased and the occurrence of polycotyledon gradually decreased. These results demonstrated that the somatic embryogenesis and occurrence of cotyledon morphology were influenced by the concentration of carbohydrates and combinations of 3% sucrose and osmoticum supplements.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.561-567
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• 2002

Xylitol is a 5-carbons carbohydrate, which can be replaced with sucrose for preventing caries. The replication of Streptococcus mutans and its formation of artificial plaque were studied in the media containing xylitol. The combined effect of xylitol and other carbohydrates on Streptococcus mutans was also studied. The replication of Streptococcus mutans was inhibited according to the increased concentration of xylitol. Streptococcus mutans replicated at the initial stage of incubation in the media containing glucose, fructose or lactose, while replicating from the beginning of incubation in the media containing fructose as combining with xylitol. The formation of artificial plaque by Streptococcus mutans was significantly reduced in the media containing with xylitol and fructose. These results indicated that the replication of Streptococcus mutans was inhibited according to the increased concentration of xylitol, and the formation of artificial plaque by Streptococcus mutans was significantly inhibited in the media containing xylitol and fructose.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.465-471
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• 2003

A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.111-118
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• 2005

The Protocol adopted in Sep. 1997 included the new Annex VI of MARPOL 73/78, which will enter into force on 19 May 2005. MARPOL Annex VI sets limits on sulphur oxide and nitrogen oxide emissions from ship exhausts and prohibits deliberate emissions of volatile organic compound (VOCs) from oil tanker in port and oil terminal. This study was conducted to find out countermeasures for the new Annex VI of MARPOL 73/78 and draw up a feasible management plan. The emission quantity of NOx and SOX from ships in Ulsan Port was calculated by U.S. EPA and Japan Marine Engineering emission factors of air pollutant from ship exhausts. In addition, volatile organic compound (VOCs) from oil tanker during the loading and discharging period, also calculated.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.380-385
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• 2018

With the tightening of environmental regulations (i.e., IMO Tier III), natural gas (NG) has been spotlighted as an eco-friendly fuel with few air pollutants other than nitrogen oxides (NOx) and sulfur oxides (SOx). For reasons of economic efficiency, it is mainly stored and transported in a liquid state at $-163^{\circ}C$, which is a cryogenic temperature, using a liquefied gas storage tank. Accordingly, it is necessary to reduce the boil-off gas (BOG) occurrence due to the heat flow according to the temperature difference between the inside and outside of the storage tank. Therefore, in this study, a BOG measurement test on an independent-type storage tank made up of SUS304L was carried out. The test results showed the tendency for BOG occurrence according to the temperature under different filling ratios.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.3
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• pp.285-291
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• 2022

In order to use the liquid rocket fuel, 1,5-diamino-4-methyltetrazolium azide, [DMT]⁺[N₃]^- and 1,5-diamino-4-methyltetrazolium cyanide, [DMT]⁺[CN]^- were synthesized and prepared the ionic liquid rocket fuel after dissolving the synthesized solid-type energetic chemicals in hydrazine, respectively. The thermal decomposition temperatures(T_d) and densities(d) of the prepared ionic liquid rocket fuels were about 200 ℃ and above 1.0 g/cm³ respectively. The ignition delay times(I_dt) of the ionic liqud rock fuels with [DMT]⁺[N₃]^- and [DMT]⁺[CN]^- were in a range of 26.6 - 82.5 ms and the 44.0 - 98.5 ms, respectively. These results mean that the synthesized tetrazolium salts could be used as an ionic liquid rocket fuels. The viscosities of the ionic liqud rock fuels with [DMT]⁺[N₃]^- and [DMT]⁺[CN]^-, which were dissolved in mixture solution of hydrazine/2-hydroxyethylhydrazine were to be 1.34 - 101 cP, and 1.29 - 80.5 cP, respectively. The synthesized ionic liquid rocket fuels in this study could be used as rocket fuel because the [I_dt(100 ms or less), T_d(150 ℃ or more), d(1.00 g/cm³ or more), and η(40.0~ 100 cP)] were achieved to satisfy the range of the used liquid rocket fuels.

• Clean Technology
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• v.21 no.3
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• pp.191-199
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• 2015

The SO_x emission from the ship diesel engines will do a negative influence to the human health and the environment. To reduce the negative environmental effect of the SO_x emission caused by the high traffic of ship movements, the SECA (SO_x emission control area) has been set on several province around world to carry out the severe emissions control and to meet the emissions control standard. To cut down the SO_x emission from the ships, the wet type scrubber is being used widely. In this work, we prepared a numerical model to simulate the spray type scrubber to study the motion of liquid droplets in the flow of the scrubber. For the analysis, the CFD (computational fluid dynamics) method was adopted. As a special topic of the study, we designed the wave plate type of mist eliminator to check the carry over of the uncontrolled water droplet to the exhaust. Numerical analysis is divided into two stages. At the first stage, the analysis was done on the basic scrubber without the mist eliminator, and then the second stage of analysis was done on the scrubber with the mist eliminator on several condition to check and compare with the basic scrubber. On the condition of the basic scrubber, 42.0% of the distributed water droplets were carried over to the exhaust. But by adding the designed droplet eliminator at the exhaust of the scrubber, only 3.4% of the distributed water droplets supplied to the scrubber was emitted to the atmosphere.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.4
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• pp.345-352
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• 2017

In this study, the effect of cryogenic liquefied natural gas leakage and loading on liquefied natural gas cargo hold is investigated to observe the performance of the polymer foam material that comprises the cryogenic insulation of the cargo hold. The primary barriers of liquefied natural gas carrier that are in contact with the liquefied natural gas will leak if damage is accumulated, owing to fluid impact loads or liquefied natural gas loading / unloading over a long period. The leakage of the cryogenic fluid affects the interior of the polymer foam, which is a porous closed cell structure, and causes a change in behavior with respect to the working load. In this study, mechanical properties of polyisocyanurate foam specimen, which is a polymer material used as insulation, are evaluated. The performance of the specimens, owing to the cold brittleness and the impregnation effects of the cryogenic fluids, are quantitatively compared and analyzed.