• 수산해양기술연구
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• 제51권4호
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• pp.512-519
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• 2015

A historical tragic disaster happened by capsizing the passenger ship Sewol at South Western Sea of Korea in 16, April 2014. The ship which left Incheon harbour to bound for Jeju port passed Maengol strait and reached to approach of Byung Pung island, and then capsized and sank with a sudden inclination to the portside in the mean time of starboard the helm. In this time, the ship which has very poor stability without sufficient ballast waters and with over loading cargo listed port side caused by the centrifugal force acting to the outside of turning. A lot of cargoes not fastened moved to the port side consequently, and the ship came to beam end to capsize and sank in the end. No crews including especially captain would offer their own duties in a such extremely urgent time, as a result, enormous number of victims broke out including a lot of student. In this report, author carried out some calculation on the factors which influenced on the stability of the ship, i.e. the ship's speed, the rudder angle, the weight of cargoes and distance of movement, the surface effect of liquid in the tank. We found out that the most causes of capsize were the poor stability with heavy cargoes and insufficient amount of ballast water against the rule, and the cargoes unfastened moved one side to add the inclination as well. Above all, the owner be blamable because of the illegally operating the ship without keeping the rule.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.668-673
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• 2012

Biohydrogen production from organic wastewater by anaerobically activated sludge fermentation has already been extensively investigated, and it is known that hydrogen can be produced by glucose fermentation through three metabolic pathways, including the oxidative decarboxylation of pyruvic acid to acetyl-CoA, oxidation of NADH to $NAD^+$, and acetogenesis by hydrogen-producing acetogens. However, the exact or dominant pathways of hydrogen production in the anaerobically activated sludge fermentation process have not yet been identified. Thus, a continuous stirred-tank reactor (CSTR) was introduced and a specifically acclimated acidogenic fermentative microflora obtained under certain operation conditions. The hydrogen production activity and potential hydrogen-producing pathways in the acidogenic fermentative microflora were then investigated using batch cultures in Erlenmeyer flasks with a working volume of 500 ml. Based on an initial glucose concentration of 10 g/l, pH 6.0, and a biomass of 1.01 g/l of a mixed liquid volatile suspended solid (MLVSS), 247.7 ml of hydrogen was obtained after a 68 h cultivation period at $35{\pm}1^{\circ}C$. Further tests indicated that 69% of the hydrogen was produced from the oxidative decarboxylation of pyruvic acid, whereas the remaining 31% was from the oxidation of NADH to $NAD^+$. There were no hydrogen-producing acetogens or they were unable to work effectively in the anaerobically activated sludge with a hydraulic retention time (HRT) of less than 8 h.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.465-469
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• 2006

Two mesophilic trickling bed bioreactors filled with two different types of media, hydrophilic- and hydrophobic-cubes, were designed and tested for hydrogen production via anaerobic fermentation of sucrose. Each reactor consisted of a column packed with polymeric cubes and inoculated with heat-treated sludge obtained from anaerobic digestion tank. A defined medium containing sucrose was fed with changing flow rate into the capped reactor, hydraulic retention time and recycle rate. Hydrogen concentrations in gas-phase were constant, averaging 40% for all conditions tested. Hydrogen production rates increased up to $10.5 L{\cdot};h^{-1}{\cdot}L^{-1}$ of reactor when influent sucrose concentrations and recycle rates were varied. Hydrophobic media provided higher value of hydrogen production rate than hydrophilic media at the same operation conditions. No methane was detected when the reactor was under a normal operation. The major fermentation by-products in the liquid effluent of the both trickling biofilters were acetate and butyrate. The reactor filled with hydrophilic media became clogged with biomass and bio gas, requiring manual cleaning of the system, while no clogging occurred in the reactor with hydrophobic media. In order to make long-term operation of the reactor filled with hydrophilic media feasible, biofilm accumulation inside the media in the reactor with hydrophilic media and biogas produced from the reactor will need to be controlled through some process such as periodical backwashing or gas-purging. These tests using trickling bed biofilter with hydrophobic media demonstrate the feasibility of the process to produce hydrogen gas in a trickle-bed type of reactor. A likely application of this reactor technology could be hydrogen gas recovery from pre-treatment of high carbohydrate-containing wastewaters.

• 비파괴검사학회지
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• 제35권5호
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• pp.358-366
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• 2015

본 논문에서는 자주포, 전차 및 장갑차 등 지상궤도전투장비에 적용되는 비파괴검사 방안 검토 및 설계방안에 대해서 연구하였다. 비파괴검사 방안 중에서 지상궤도전투장비 비파괴검사자의 기량검증 요건은 미군규격에서 최초로 언급 되었으며, 이후 국내 지상궤도전투장비 무기 개발시 국방규격에도 적용되었다. 그러나 민 군 규격통일화사업을 통해 방산용 비파괴검사자의 자격은 기존 항공분야에서 적용중이던 NAS410이 항공/방산 공용규격으로 통합화 되었다. 본 연구에 대한 설계방안의 검증은 자주포에 사용되는 Al 단조품에 대해 최적설계된 액체침투탐상검사 방법을 적용하여 제품의 신뢰성 및 건전성을 확인하였다.

• 한국수산과학회지
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• 제39권2호
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• pp.72-77
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• 2006

Enrofloxacin (ENRO) is one of the most commonly used fluoroquinolones for treating bacterial disease in olive flounder (Paralichthys olivaceus) farming, but its withdrawal time for industrial-scale farming has not been well established. Withdrawal times of ENRO following oral administration were evaluated in olive flounder under field conditions. Fish were held in an inland fish tank and fed a commercial mediated diet containing 5 mg/kg of ENRO for 9 days. Seven fish per sampling point were examined during and after treatment. ENRO and its major metabolite, ciprofloxacin (CIP), were analyzed using high-performance liquid chromatography with a fluorescence detector. The concentration of ENRO and CIP in muscle increased during the medication period, and then decreased rapidly The sum of ENRO and CIP concentration in olive flounder peaked on day 6, with a maximal concentration in muscle of 4.30 mg/kg. ENRO residues were eliminated rapidly; at 10 days post treatment, the level in muscle was 0.10 mg/kg, but it took about 50 days to be reduced to below 0.1 mg/kg. After 60 days, the residual concentration was below 0.1 mg/kg in all samples. The level of ENRO accumulation at the beginning of oral administration was variable, according to the farming conditions, but the overall exhaustion time was almost the same. We concluded that an adequate withdrawal period of enrofloxacin is 60 days in the case of oral administration.

• 한국추진공학회지
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• 제25권1호
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• pp.1-11
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• 2021

포고 현상은 액체추진 로켓에서 발생하는 축방향의 동적 불안정 진동이다. 동체의 고유진동수와 추진제 공급계의 주파수가 가까와 지면 전체 시스템이 불안정 현상을 보인다. 포고 현상을 예측하기 위해 1단의 추진제 (산화제 및 연료) 탱크는 쉘 요소로, 나머지 구성 요소인 엔진 및 상단은 mass-spring으로 모델링하여 구조해석을 수행하였다. 추진제 공급계의 압력 및 유량 섭동예측에는 transmission line model이 사용되었다. 본 논문에서는 이와 같이 수행된 구조 및 유체 모델링을 통합하여 폐루프 전달함수를 구성하였다. 포고 억제기는 수동적인 방법으로 압력 섭동을 흡수하는 분 기관 및 accumulator로 구성되며 추진제 공급계 중간에 위치한다. 발사체의 비행과정 동안 포고현상을 억제하는 설계 최적화를 위한 설계변수로는 분기관 및 accumulator의 직경 및 길이로 설정하였다. 목적함수로는 포고 억제기의 질량, 그리고 추진제 질량에 따른 폐루프 전달함수의 에너지 최소화로 설정하여 다목적함수 최적화를 수행하였다.

• Ocean and Polar Research
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• 제33권3호
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• pp.303-308
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• 2011

Polar psychrophiles which thrive under extreme conditions such as cold temperature, high salinity, and high dose ultraviolet light, emerge as novel targets for biotechnology. To prevent genetic drift and the possibility of contamination by subculturing, cryopreservation was employed for two psychrophilic microalgae, Porosira sp. (KOPRI AnM0008) and Pyramimonas sp. (KOPRI AnM0046), which have anti-freeze activities. Five cryoprotectants (dimethyl sulphoxide, ethylene glycol, glycerol, methanol and propylene glycol) showed toxicity at 20-30% (v/v). The optimal cryoprotectant concentration and equilibration time were less than 20% and 10 min, respectively. Cryopreservation was carried out in the presence of cryoprotectants either by direct freezing in liquid nitrogen ($LN_2$) or controlled freezing using a controlled rate freezer followed by storage in the $LN_2$ tank. As a result, Pyramimonas sp. (KOPRI AnM0046), a psychrophilic chlorophyta was revived. Cryopreserved Porosira sp. was not revived from either freezing protocols probably due to the silicic cell wall and its relatively large cell size. In the case of Pyramimonas sp. (KOPRI AnM0046), the controlled freezing method showed higher revival yield than the direct freezing method.

• 한국안전학회지
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• 제35권6호
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• pp.25-31
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• 2020

Boiling Liquid Expanding Vapor Explosion(BLEVE) can cause not only economic damage to the plant but also serious casualties. LPG accidents account for 89.6 percent of all accidents caused by gas leaks in Korea over the past nine years, while casualties from accidents also account for 73 percent of all accidents, according to statistics from the Korea Gas Safety Corporation. In addition, a potential explosion and a fire accident from one LPG storage tank may affect the nearby storage tanks, causing secondary and tertiary damage (domino effect). The safety distance standards for LPG used by LPG workplaces, charging stations, and homes in Korea have become stricter following the explosion of LPG charging stations in Bucheon. The safety distance regulation is divided into regulations based on the distance damage and the risk including frequency. This study suggests two approaches to optimizing the safety distance based on the just consequence and risk including frequencies. Using the Phast 7.2 Risk Assessment software by DNV GL, the explosion overpressure and heat radiation were derived according to the distance caused by BLEVE in the worst-case scenario, and accident and damage probability were derived by considering the probit function and domino effect. In addition, the safety distance between LPG tanks or LPG charging stations was derived to minimize damage effects by utilizing these measures.

• 공업화학
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• 제25권2호
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• pp.142-146
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• 2014

9성분계 모델 콜타르 유분 중에 함유된 질소고리화합물(NHC)의 분리를 분배평형에 의해 검토했다. 원료로서는 NHC group (NHCs; quinoline (Q), iso-quinoline (iQ), indole (In), quinaldine(Qu)), 2환 방향족 화합물 group (BACs; 1-methylnaphthalene (1MN), 2-methylnaphthalene (2MN), dimethylnaphthalene (DMN)), biphenyl (Bp)과 phenyl ether (Pe)로 제조한 모델 콜타르 유분을, 용매로서는 메탄올 수용액을 각각 사용했다. 액-액 접촉 장치로서는 회분 교반기를 각각 사용했다. 평형조작 온도가 상승함에 따라 NHCs의 분배계수는 증가했으나, 역으로 BACs를 기준한 NHCs의 선택도는 감소했다. 초기 물/용매의 체적비가 감소함에 따라 BACs를 기준한 NHCs의 선택도는 급격히 감소했으나, NHCs의 분배계수는 증가했다. 일정 조건하에서, 각 group별 분배계수와 BACs를 선택도의 순서는 NHCs > Bp > BACs > Pe와 NHCs > Bp > Pe를 각각 나타냈다. 또한 전체 성분에 대한 분배계수의 순서는 In > iQ = Q > Qu > Bp > 1MN = 2MN > Pe > DMN을 나타냈다. 메탄올 추출에 의해 얻어진 NHCs의 최대 수율과 BACs를 기준한 NHCs의 최대 선택도는 각각 94%, 23이었다. 본 연구를 통해 얻어진 실험적 결과를 이용하여 콜타르 중에 함유된 NHCs의 회수공정을 검토했다.

• 한국가스학회지
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• 제5권4호
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• pp.40-48
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• 2001

본 연구에서는 LPG 충전소에 대하여 Fussel-Vesely 중요도와 RDF 및 RIF 중요도를 수행하여 위험성 등급(Risk Rank)을 설정하였다 설정된 위험성 등급에서 위험성이 가장 큰 장치 및 설비에 대하여 정량적 위험성 분석을 수행하였다. LPG 충전소에 대한 중요도 분석결과 외부사고가 가장 위험하다고 확인되었으며, ekda 으로 구조물 결함과 파이프 배관의 부식의 위험등급이 높았다. 정량적 위험성 분석 결과로는 LPG 충전소 저장탱크의 완전히 파열하였을 경우에 대한 BLEVE의 경가 발생하였을 경우에 복사열에 의해 공정 설비에 손해를 입히기에 충분한 거리는 46.3m로 분석되었다.