• 한국수산과학회지
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• 제56권6호
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• pp.870-877
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• 2023

The purpose of this study was to assess the efficiency of nitrification based on ammonia loading rates and hydraulic air-loading rates in a moving bed bioreactor (MBBR) under seawater conditions. The goal was to provide foundational data for the design of these bio reactors. At an ammonia loading rate of 0.2 g TAN·m^-2 surface area·day^-1, the influent TAN concentration was determined to be 1.76±0.33 mg·L^-1, which is below the safe concentration for fish survival (2 mg·L^-1). Considering operational aspects, the optimal ammonia-loading rate was derived. Subsequently, experimental results for nitrification efficiency at the optimal ammonia-loading rate revealed that the optimum hydraulic air-loading rate was 1.8 L·air·m^-2 surface area·min^-1. This condition resulted in the lowest concentrations of TAN and NO₂-N in the influent water, thus establishing the optimal hydraulic air-loading rate. A regression equation was derived for the ammonia-removal rate (Y) based on the ammonia-loading rate (x) and expressed as a 0.5-order equation (Y=ax^0.5+b). Specifically, for TAN concentrations of 0-6 mg·L-1, the regression equation Y=0.1683x^0.5-0.13628, was established.

• 해양환경안전학회지
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• 제19권1호
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• pp.52-58
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• 2013

선박의 운항에 소요되는 운항비는 선박의 종류, 크기, 속력, 항행구역 등에 따라 다를 수 있지만, 연료비가 차지하는 비율은 50~60 %에 달하는 것으로 알려져 있다. 최근 국제 유가의 상승으로 인한 선박 운용비를 절감하기 위하여 중소형 선박에서도 저질연료유의 사용이 검토되고 있는 추세이다. 더 나아가 해운선사들은 연료소모량을 줄이기 위한 방법으로 감속운항을 취하고 있다. 따라서, 본 연구에서는 실선을 이용하여 해상에서의 선속대비 주기관의 연료소모량을 계측하고, 부하에 따른 전진계수 대비 속력과 연료소모량의 관계를 통해 상용연속출력보다 낮은 주기관 부하의 70 % 영역이 최적의 운항조건이라고 제안하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.101-106
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• 2006

Balance shaft has a key role in reducing a engine vibration in a vehicle and widely applied for current models. Since balance shaft module consists many sub-component and each part has its own operational characteristics, some different analysis backgrounds should be integrated into one sub-part in balance shaft module and this is the main obstacles in making a design process. Moreover, the balancing shaft is rotating in high speed and such condition requires large safety factors in a design process owing to a lot of unexpected problems with the overwhelming rotation. Balance shaft is the core-component generating the intended unbalance as well as cancelling the unbalance force or moment by the engine module. So, the balance shaft should meet the high fatigue resistance not to mention of NVH performance. In this paper, a design strategy focused on balance shaft is developed to build a optimal model considering a engine vibration. Putting the unbalance mass distribution as main design parameter, some candidate model is verifed with structural and fatigue analysis and most appropriate model is proposed here.

• 유통과학연구
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• 제18권1호
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• pp.85-94
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• 2020

Purpose: This study investigates the influence of VMI on the supply chain performance over time. By examining each supply chain member's ongoing performance, this study figures out how VMI allows the vendor to overcome the initial loss and eventually provides the benefit to every supply chain member. Research design, data, and methodology: The proposed mathematical model describes the supply chain system where a manufacturer and a retailer make the operational decisions to maximize their own profits. By using the numerical examples with arbitrary data, VMI and non-VMI are compared in terms of their profit changes over time. Results: The numerical analysis shows that VMI results in greater overall profits for both manufacturer and retailer than non-VMI, while the manufacturer make a loss in the early stage of VMI implementation. This study also examines the impacts of certain conditional factors on the performance of VMI. Conclusions: This study supports the idea that VMI leads to manufacturer's initial loss but it brings greater profits to both manufacturer and retailer than non-VMI after all. In addition, the result of this study provides the managerial implications about the particular condition that allows VMI to achieve a significant financial performance improvement over non-VMI.

• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.369-376
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• 2015

Recently KEPCO, KOGAS and other institutions are jointly conducting an R&D for the development and demonstration of the power generation system based on a natural gas/diesel engine on an island. As a preliminary study, co-combustion in the dual fuel engine, which is expected to produce a few mega-watts of electricity, was modeled and calculated using computational fluid dynamics (CFD). The applied key assumptions are 2-dimensional axisymmetric, transient and static volume chemical reaction. Based on the selected blending ratio, which is the key operating condition, natural gas is substituted instead of diesel fuel (basis of high heating value). Results showed that as the blending ratio increases, the reaction rate of the combustion increases and thus maximum temperature is reached more rapidly. For the optimal performance, various geometric or operational studies will further be conducted.

• 센서학회지
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• 제20권1호
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• pp.35-39
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• 2011

A disposable electrochemical immunosensor system has been developed for the detection of herbicide in aqueous samples. Disposable screen printed carbon electrodes(SPCE) were used as basic electrodes and an enzyme, horseradish peroxidase (HRP), and anti-herbicide antibodies was immobilised on to the working electrode of SPCE by using avidin-biotin coupling reactions. An herbicide-glucose oxidase conjugates have been used for the competitive immunoreaction with sample herbicides. The enzymatic reaction between the conjugated glucose oxidase and glucose added generates hydrogen peroxide, which was reduced by the peroxidase immobilised. The latter process caused an electrical current change, due to direct re-reduction of peroxidase by a direct electron transfer mechanism, which was measured to determine the herbicides in the sample. The optimal operational condition was found to be: $20\;{\mu}gl-1$ deglycosylated avidin loading to the working electrode and working potential +50 mV vs. Ag/AgCl. The total assay time was 15 min after sample addition. The detection limits for herbicides, atrazine and simazine, were found to be 3 ppb and 10 ppb, respectively.

• 대한전기학회논문지:전력기술부문A
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• 제53권4호
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• pp.221-226
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권4호
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• pp.221-221
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• 한국수자원학회논문집
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• 제42권9호
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• pp.759-771
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• 2009

장거리 용수공급 시스템에서 전력비용은 전체 운영비용의 큰 부분을 차지한다. 본 연구는 시간단위의 펌프와 배수지 시스템의 최적 운영계획을 평가하기 위해 동적계획기법에 기초한 방법론을 제시하고 있다. 해석방법은 운영비용 최소화 관점에서 펌프용량 확대를 전제로 현재 가용 펌프의 효율적 운전과 전력요금체계, 시간별 용수수요 추이 그리고 배수지 특성과 송수관로의 제약조건 등을 고려하였다. 이를 위해 적용 가능한 시스템 운영목적과 제약조건이 제시되었고 개발된 방법은 수도권 광역상수도 양주계통의 2개 가압장과 5개 배수지를 대상으로 적용하였다. 적용결과는 펌프 확장의 경우 상당한 수준의 운전비용을 절감할 수 있는 것으로 나타났으며, 이와 같은 방법은 기존 시스템의 최적운영은 물론 생애주기 비용 최소화 측면에서 신규 용수공급 체계의 설계 등에 적절히 활용될 수 있다.

• Archives of Pharmacal Research
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• 제3권1호
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• pp.7-12
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• 1980

Ampliciline was synthesized from 6-amino-pencillanic acid (6-APA) and D-.alpha. phenylglycine methyl ester by using amplicilin synthesizing enzyme from Peudomonas melanogenum (IAM 1655). The whole cell enzyme was immobilized by entrapping it in the polyacrylamide gel lattices. The polymer used in the enzyme entrapment was made from 150 mg per ml of acrylamide monomer and 8 mg per ml of N, N'-methylenebisacrylamide. About 200 mg/whole cell enzyme was mixed in the polymer for entrapment. The maximal activity retention after immobilization was 56%. The optimal pH values for the whole cell enzyme and the immobilized whole cell enzyme were 6.0 and 5.9, respectively. The optimal temperature for the enzyme activity were the same for both type of preparations. The enzyme stabilities against pH and heat increased for immobilized whole cell enzyme. Immobilized cell was more stable especially in the acidic condition while both type were found to be very suceptible to thermal inactivation at a temperature above 4.deg.C. The kinetic constants obtained from Lineweaver-Burk plot based on two substate reaction mechanism showed somewhat higher value for immobilized whole cell enzyme as compared to the whole cell enzyme : the Km value for 6-APA were 7.0 mM and 12.5 mM while Km values for phenylglycine methyl ester were 4.5 mM and 8.2 mM, respectively. Using the immobilized whole cell enzyme packed in a column reactor, the productivity of ampiciline was studied by varying the flow rate of substrate solution. At the space velocity, SV, 0.14 hr$^{-1}$ the conversion was 45%. Operational stability found in terms of half life was 30 hr at SV = 0.2 hr.