• 한국농공학회논문집
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• 제53권2호
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• pp.53-60
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• 2011

This study was conducted to investigate the effect of hydropower factors (watershed, gross head), operation ratio and unit electricity cost on the benefit-cost ratio (B/C ratio) of small hydropower using agricultural reservoirs. The equation of B/C ratio was expressed as a function of watershed area, gross head, operation ratio and unit electricity cost. The benefit increased with watershed area, gross head and unit electricity cost, while the cost increased with watershed area and gross head but decreased with operation ratio. The B/C ratio increased with watershed area, gross head, operation ratio and unit electricity cost. While the effect of gross head on the B/C ratio decreased with watershed area, the effect of operation ratio and unit electricity cost on the B/C ratio increased with watershed area. The operation ratio is an important factor to affect the B/C ratio and therefore we need to develop hydropower for the heightened dams to expect high operation ratio due to continuous water release. The unit electricity cost is also an important factor to affect the B/C ratio and the B/C ratio was always below 1 unless unit electricity cost is over 60 Won/kWh under given conditions. The reservoirs with economic feasibility for small hydropower development were three in 21 when the equation of B/C ratio was appled to the study reservoirs. The results can be used to choose the appropriate reservoir with economic feasibility for development of small hydropower.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.507-512
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• 2010

The effect of catholyte to anolyte amount ratio on the electrodialysis cell performance for HI concentration was investigated. For this purpose, the electrodialysis cell was assembled with Nafion 117 as PEM membrane and activated carbon fiber cloth as electrodes. The initial amount of catholyte was 310 g and that of anolyte varied from 1 to 3 of amount ratio. The calculated electro motive force (EMF) increased with time and the increment enhanced as the amount ratio of catholyte to anolyte decreased. The mole ratios of HI to $H_2O$ (HI molarity) in catholyte were almost the same and exceeded pseudo-azeotropic composition for all amount ratios after 2 h operation. The HI molarity continuously increased with time for 10 h operation. The mole ratio of $I_2$ to HI decreased in catholyte but increased in anolyte. The increment of mole ratio of $I_2$ to HI in anolyte rose as the amount ratio of catholyte to anolyte decreased. In case of 1:1 amount ratio, the cell operation was stopped for the safety at approximately 6 h operation, since the mole ratio of $I_2$ to HI reached solubility limit. The cell voltage of the electrodialysis cell increased with time and the rate of increase was high at low amount ratio. This suggests that the amount ratio of catholyte to anolyte not only crucially influences the cell voltage, but also cell operation condition.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.573-579
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• 2013

Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

• Industrial Engineering and Management Systems
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• 제1권1호
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• pp.19-28
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• 2002

An operation sequence of parts is one of the most important production factors in the design of cellular manufacturing systems. Many similarity coefficient method (SCM) based approaches have been proposed to solve cell formation problems in the literature. However, most of them do not consider the operation sequence factor. This study presents an operation sequence ratio (OSR) and modifies some existing similarity coefficients using the OSR to solver cell formation problems considering operation sequences. The computational results show that the OSR ratio is useful and robust in solving cell formation problems with operation sequences.

• 한국응용과학기술학회지
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• 제28권1호
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• pp.6-9
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• 2011

Step feed process was analyzed stoichiometrically for the optimal operation conditions in this study. In case of optimal operation conditions, minimum R (sludge recycling) value, r (internal recycling ratio) value, and n (influent allocation ratio) value for the step feed process to acquire the maximum TN removal efficiency were identified by theoretical analysis. Maximum TN removal efficiency, based on stoichiometric reaction, can be obtained by controlling n value for the step feed process.

• 전기학회논문지
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• 제65권4호
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• pp.539-546
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• 2016

With the growing interest of microgrid systems all over the world, many studies on microgrid operation are being carried out. The battery energy storage system(BESS) and the diesel generator are key equipments in the microgrid. In this paper, we analyze the characteristics of fuel consumption according to the power ratio of the diesel generator. Then, the formula to represent the unit cost of generation according to the power ratio of the diesel generator is derived. A new modeling of battery operation is presented considering the lifetime reduction according to increasing the cycles of charge/discharge operation of the battery. The methodology of determining the optimal operation of the battery and the diesel generator is presented by the use of the formula of fuel consumption of the diesel generator and the new modeling of battery operation. It is shown that this optimization methodology can be applied effectively for economical operation of the BESS and the diesel generator of a microgrid by case studies.

• 전자공학회논문지A
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• 제32A권11호
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• pp.71-78
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• 1995

Based on the popular 4-transistor SRAM cell, an analytical expression of the minimum cell ratio was derived by modeling the static read operation. By analyzing the relatively simple expression for the minimum cell ratio, which was derived assuming the ideal transistor characteristics, effects of the changes in supply voltage and process parameters on the minimum cell ratio was predicted, and the minimum power supply voltage for read operation was determined. The results were verified by simulations utilizing the suggested simulation method, which is suitable for monitoring the lower limit of supply voltage for proper cell operation. From the analysis, it was shown that the worst condition for cell operation is low temperature and low supply voltage, and that the operation margin can be effectively improved by reducing the threshold voltage of the cell transistors.

• 융합정보논문지
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• 제11권4호
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• pp.203-210
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• 2021

본 연구는 의료기관의 설립운영 관리주체에 따라 운영자금 조달방법별 조달비율과 이들이 경영성과에 미치는 영향을 살펴보고자 의료기관 회계정보 공시시스템에 등록된 재무정보를 이용하여 분석하였다. 분석방법은 설립운영 관리주체별 차이비교를 위하여 분산분석을 실시하였으며, 운영자금 조달방법별 조달비율이 경영성과에 미치는 영향은 로지스틱 회귀분석과 회귀분석을 실시하였다. 연구결과, 운영자금 대비 총수익 비율은 설립운영 관리주체에 따라 유의한 차이가 있었다. 그리고 운영자금 조달방법별 조달비율은 경영결과(적자, 흑자)와 유의하게 인과관계가 있는 것으로 확인되었으며, 운영자금 조달방법 조달비율이 경영성과에 미치는 영향은 설립운영 관리주체에 따라 차이가 있었다. 이상의 결과 의료기관의 운전자금 관리는 운영자금에 대한 수익의 비율을 고려한 비용관리를 우선적으로 적용하고 그 다음으로 내부운영자금을 활용하는 방안의 적용이 적절할 것으로 사료된다.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.201-208
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• 2004

Response characteristics of the CVT system for a parallel hybrid electric vehicle (HEV) are investigated. From the experiment, CVT ratio control algorithm for the optimal engine operation is obtained. To investigate the effect of the CVT system dynamic characteristics on the HEV performance, a hardware in the loop simulation (HILS) is performed. In the HILS, hardwares of the CVT belt-pulley and hydraulic control valves are used. It is found that the engine performance by the open loop CVT ratio control shows some deviation from the OOL in spite of the RCVs open loop control ability. To improve the engine performance, a closed loop control of the CVT ratio is proposed with variable control gains depending on the shift direction and the CVT speed ratio range by considering the nonlinear characteristics of the RCV and CVT belt-pulley dynamics. The HILS results show that the engine performance is improved by the closed loop control showing the operation trajectory close to the OOL.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.200-201
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• 2014

The construction industry in recent years, due to the multi-species engineering specialty, interest and importance of human resource management is growing. But, not many studies on the operation ratio are being proceeded due to the difficulty of casting people on site and actual survey. Thus, this study proposes the work type-specific quantitative operation ratio through work type-specific operation ratio analysis of reinforced concrete construction which takes up an important part of construction work.