• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.267-273
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• 2018

Hydrothermal liquefaction of Chlorella vulgaris feedstock containing 80% (w/w) water was conducted in a batch reactor as a function of temperature (300, 325 and $350^{\circ}C$) and reaction times (5, 10 and 30 min). The biocrude yield, elemental composition and higher heating value obtained for various reaction conditions helped to predict the optimum conditions for maximizing energy recovery. To optimize the recovery of inorganic nutrients, we further investigated the effect of reaction conditions on the ammonium ($NH_4{^+}$), phosphate ($PO_4{^{3-}}$), nitrate ($NO_3{^-}$) and nitrite ($NO_2{^-}$) concentrations in the aqueous phase. A maximum energy recovery of 78% was obtained at $350^{\circ}C$ and 5 min, with a high energy density of 34.3 MJ/kg and lower contents of oxygen. For the recovery of inorganic nutrients, shorter reaction times achieved higher phosphorus recovery, with maximum recovery being 53% at $350^{\circ}C$ and 5 min. Our results indicate that the reaction condition of $350^{\circ}C$ for 5 min was optimal for maximizing energy recovery with improved quality, at the same time achieving a high phosphorus recovery.

• Ocean and Polar Research
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• 제26권2호
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• pp.361-365
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• 2004

Deep-sea Resources Research Center (DRRC) has been using a free-fall grab (FFG) for the resource evaluation of polymetallic nodules in the KODOS (Korea Deep Ocean Study) area, NE Pacific, since 1992. A FFG model (Model 4200, Benthos) adapting one glass buoy system (diameter 17 inch, net buoyance 25.4 kg) has been used until 1993. Since then, DRRC has carried out a study to increase the recovery rate of FFG and it was found that a revised system adapting an additional buoy (diameter 10 inch, net buoyance 4.5 kg) gives improved results. The nodule sampling tests were performed using two different models for the same study area and the resulting recovery rates were compared. The result shows no distinct difference in recovery time between two models, but average recovery rate of the revised model was increased to 99.44% from 96.06% of the original model.

• 대한조선학회 특별논문집
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• 대한조선학회 2013년도 특별논문집
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• pp.103-109
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• 2013

The Present work focuses on application of Organic Rankine Cycle - Waste heat Recovery System (ORC-WHRS) for marine diesel engine. ORC and its combined cycle with the engine were simulated and its performance was estimated theoretically under the various engine operation conditions and cooling water conditions. The working fluid, R245fa, was selected for the consideration of the heat source temperature, system efficiency and safety issues. According to the thermodynamic analysis, ~13.1% of system efficiency of the cycle was performed and it is about 4% of the mechanical power output of the considering Marine Diesel Engine. Also, addition of evaporator and pre-heater were studied to maximize output power of Organic Rankine Cycle as a waste heat recovery system of the marine diesel engine.

• 한국해양환경ㆍ에너지학회지
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• 제6권3호
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• pp.54-62
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• 2003

본 연구에서는 다양한 침몰선박 잔존유회수 방법 중에서 안전성과 경제성을 바탕으로 우리나라 해역특성에 적합한 무인 원격회수방법을 선정하였다. 이와 함께 우리나라 전 연안에서 회수작업을 실행할 수 있는 작업 수심 200m급 잔존유 무인회수시스템(Remotely Operated Recovery System)의 요구사양을 선정하고 회수장비에 대한 기본설계를 수행하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.160-161
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• 2022

Hydrogen is bridge fuel with high energy content and environmentally friendly to satisfy the stringent IMO regulation relating to greenhouse gas (GHG) emissions. There is growing interest in hydrogen in numerous nations and regions illustrated by an extensive range of research and development in technology. Regarding maritime applications, researchers have recognized the utilization of hydrogen as a fuel for fuel cells, a device that converts the chemical energy of the fuel to electrical energy. Solid oxide fuel cell (SOFC), with high working temperature, is easy to combine with the waste heat recovery cycles/devices to increase output power and thermodynamic performances as well. Furthermore, the cold energy from liquid hydrogen supplied to SOFC can also be used to generate more power. In this study, we proposed a SOFC integrated system with the idea of combining the waste heat recovery from the SOFC exhaust stream and cold energy utilization from LH₂. The designation is aimed to target small-scale vessel which uses electric propulsion for short distances voyage.

• 한국수산과학회지
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• 제52권3호
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• pp.232-240
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• 2019

Approximately 80% of the world's sea cucumbers Apostichopus japonicas are processed into dried sea cucumbers. The hot air-drying method is currently used in industry, but it has many problems, such as a short drying time, severe browning, high nutrition loss, and low recovery. In this study, the moisture absorption rate, dry recovery rate, and lipid nutrient composition of sea cucumber dried by heat pump decompression and with a hybrid dryer were investigated. The moisture absorption rates for hybrid-dried sea cucumbers at 24, 48, 72, 96, and 120 h were 241.3%, 427.7%, 652.0%, 721.0%, and 742.2%, respectively. The moisture absorption rates for hot air-dried sea cucumbers were 155.8%, 240.0%, 390.3%, 655.5%, and 667.4%, respectively. Thus, moisture absorption was faster and greater with hybrid drying than with hot air drying. The dry recovery rate at 24 h was greater for hybrid-dried sea cucumber (70.7%) than for hot air-dried sea cucumber (59.8%). Saturated fatty acid contents of the hybrid- and hot air-dried sea cucumbers were 30.0% and 37.5%, respectively. Moreover, greater ${\Sigma}n-3$ polyunsaturated fatty acid content was found in hybrid-dried sea cucumber (15.8%) than in hot air-dried sea cucumber (11.7%).

• Journal of information and communication convergence engineering
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• 제10권1호
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• pp.11-20
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• 2012

In a marine ubiquitous sensor network (USN) system using expensive sensors in the harsh ocean environment, it is very important to discover failures and devise recovery techniques to deal with such failures. Therefore, in order to perform failure modeling, this study analyzes the USN-based real-time water quality monitoring service of the Gaduri Aqua Farms at Songdo Island of Yeosu, South Korea and devises methods of discovery and recovery of failure by classifying the types of failure into system element failure, communication failure, and data failure. In particular, to solve problems from the perspective of data, this study defines data integrity and data consistency for use in identifying data failure. This study, by identifying the exact type of failure through analysis of the cause of failure, proposes criteria for performing relevant recovery. In addition, the experiments have been made to suggest the duration as to how long the data should be stored in the gateway when such a data failure occurs.

• 한국해양생명과학회지
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• 제6권2호
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• pp.117-123
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• 2021

Post-disturbance recovery pattern of subtidal soft corals-macroalgae mixed community and the role of water depth were investigated. The experiment was conducted in a subtidal rock wall of Munseom, Jeju Island, Korea for 2.5 years. Artificial disturbance was done at established treatment plots at depths of 10, 15 and 20 m and were then compared with undisturbed control plots. After disturbance, recovery of soft corals was very slow, whereas macroalgae quickly occupied the plots and reached a similar level as the control in 6 months, and this pattern was consistent at all water depths. This unbalanced speed of recovery caused higher macroalgae establishment than soft corals in treatment compared to control plots, indicating a possible phase shift in the community structure. This study provides an important implication for the necessity of monitoring the influence of disturbance at a larger scale, from a conservation perspective of soft corals in Jeju coast.

• 해양환경안전학회지
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• 제11권2호
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• pp.103-108
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• 2005

본 연구는 탱크로리용 디스크식 유회수기 개발을 위한 기초 연구로 기존 유회수기 디스크와 기름의 흡착이 가능하다고 판단되는 몇가지 재료의 디스크에 대한 유회수 차이를 실험을 통해 비교한 것이다. 실험 결과를 요약하면 다음과 같다. 모든 디스크에서 경유보다는 벙커 A유의 회수량이 높았으며, 경유에서는 디스크 소재별 유회수량이 모든 디스크에서 거의 차이가 없는 반면, 벙커 A유에서는 디스크 소재에 따라 회수 성능이 큰 차이를 보였다. 또한, 디스크 구동 시간대별 회수량은 경유의 경우, 모든 디스크 소재에서 초기 시간대부터 단위 구동 시간당 기름의 회수량 차이가 거의 없는 것으로 나타난 반면, 벙커 A유는 모든 소재에서 구동 초기시간에서 회수량이 직선적으로 증가하고 시간이 경과할수록 증가량이 완만한 경향을 보여 단위 구동 시간당 기름의 회수량이 시간에 따라 차이를 보이는 것으로 나타나 유류의 점도가 디스크 회수성능에 영향을 미치는 것을 알 수 있었다. 또한, 벙커 A유를 대상으로 전체 회수량에서 순수 유회수량과 함수량을 비교했을 때 창문용 알미늄 소재의 디스크는 다른 재질의 디스크에 비해 기름의 회수량은 차이가 없으면서 상대적으로 물의 회수량은 매우 적게 나타나는 것으로 조사되어 함수량을 고려한 유회수 효율을 고려했을 때 가장 이상적인 결과를 보여주고 있어, 본 연구에서 목적하는 탱크로리 유회수기 디스크 소재로서 가장 유리하다는 것을 알 수 있었다.

• 해양환경안전학회지
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• 제19권6호
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• pp.606-611
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• 2013

본 연구에서는 지역별 해상 기름회수능력을 설정할 목적으로 7개 항목에 대한 지역별 현황을 조사 분석하여 정규화한 결과와 계층분석과정을 이용하여 도출한 가중치를 바탕으로 권역내 각 지역별 위험도를 산출하였다. 산출된 위험도를 바탕으로 권역내 확보해야 하는 해상 기름회수능력인 $7,500k{\ell}$ 를 해당 지역의 위험도에 따라 해상 기름회수능력을 결정하여 지역별 적정 해상 기름회수능력을 제시하였다. 현행 해상 기름회수능력이 과하게 설정된 인천, 군산, 목포, 부산지역의 기름회수능력이 권역내 다른 지역으로 분산 배치되는 결과를 보였으며, 권역 중심지역의 경우 대산 $1,475k{\ell}$, 여수 $375k{\ell}$, 울산 $475k{\ell}$ 증가하는 것으로 나타났다. 해양사고의 원인적인 측면뿐만 아니라 환경 경제적인 측면까지 고려하여 제시된 지역별 해상기름회수능력 설정치는 현행 기준에 의한 설정치보다 균형적인 배치분포를 보이는 것으로 나타났다.