• 한국자동차공학회논문집
• /
• 제20권2호
• /
• pp.56-63
• /
• 2012

Environment has become a main issue nowadays. People began to show big interest in "futuristic means of transportation", which is an efficient method in $CO_2$ emissions reduction and decreasing use of oil. Due to the noise and emissions of two-wheel vehicle of internal combustion engine, electric two-wheeled vehicles have been supplied in downtown. The electric two-wheeled vehicles use battery as power source. The performance of lithium-ion battery changes as the ambient temperature changes. In this paper, analysis of performance variance of electric two-wheeled vehicles influenced by the temperature using the chassis dynamometer and the environmental chamber was carried out.

• 한국유체기계학회 논문집
• /
• 제7권6호
• /
• pp.55-61
• /
• 2004

A numerical procedure for optimizing the shape of three-dimensional sedimentation tank is presented to maximize its sedimentation efficiency. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis for multi-phase flow. Standard $k-{\epsilon}$ model is used as a turbulence closure. Three design variables such as, tank height to center feed wall diameter ratio, blockage ratio of center feed wall and angle of distributor are chosen as design variables. Sedimentation efficiency is defined as an objective function. Full-factorial method is used to determine the training points as a means of design of experiment. Sensitivity of each design variable on the objective function has been evaluated. And, optimal values of the design variables have been obtained.

• 해양환경안전학회지
• /
• 제2권1호
• /
• pp.67-75
• /
• 1996

An innovative batch electrolytic system consisted of electrolytic basin, which was equipped with DSA(Dimensionally Stable Anode) type insoluble electrode, Ti/IrO2 anode and H-C metal cathode, and flotation separator was developed for the efficient treatment of shipboard emulsified oily wastewater. The electorod cleance and current density of elecrolytic basin to ensure maximum treatment efficiency of oily wastewater was evaluated as 6 mm, 3 A/dm3, respectively. The electrolytic efficiency of oily wastewater was affected by the operationtemperature, and it means that the temperature controller to ensure the stabiity of the process is required. The conductivity in the electrolytic basin was increased with the percentage of sea water in the oily wastewater, and over 90% of treatment efficiency of oily wastewater could be obtained at 7% of sea water. The oil removal rate was increased according to the increase of the quantity of electricity, and the maximum value of electrilyic rate constant was 288 mgoil/A.min. The information obtained from this study might be used for development of an efficient continuous electrolytic system treating the emulsified oily wastewater.

• 조명전기설비학회논문지
• /
• 제26권5호
• /
• pp.85-90
• /
• 2012

In this paper, it was investigated experimentally that diameter and polarity variation of corona wire electrode affected to ozone generation of the ozone generator using a wire-to-plate type electrode. The change in the diameter(D) of the corona wire electrode has a great effect upon ozone generation, higher influence appears in the positive corona discharge than the negative corona discharge. In the case of D=0.50[mm], maximum ozone generation and power efficiency could be obtained. However, in the case of smaller D than this, the ozone generation and efficiency decreases slowly and in the case of larger D, the ozone generation decreases rapidly. It means performance decline as an ozone generator. Therefore, ozone generation and power efficiency would increase through simple optimization of the corona electrode specification.

• Nuclear Engineering and Technology
• /
• 제53권6호
• /
• pp.2066-2073
• /
• 2021

The use of nuclear reactors is a large studied possible solution for thermochemical water splitting cycles. Nevertheless, there are several problems that have to be solved. One of them is to increase the efficiency of the cycles. Hence, in this paper, a thermal energy optimization of a Sulfur-Iodine nuclear hydrogen production cycle was performed by means a heuristic method with the aim of minimizing the energy targets of the heat exchanger network at different minimum temperature differences. With this method, four different heat exchanger networks are proposed. A reduction of the energy requirements for cooling ranges between 58.9-59.8% and 52.6-53.3% heating, compared to the reference design with no heat exchanger network. With this reduction, the thermal efficiency of the cycle increased in about 10% in average compared to the reference efficiency. This improves the use of thermal energy of the cycle.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권2호
• /
• pp.673-694
• /
• 2021

In this paper, we intend to study the energy efficiency (EE) optimization for a simultaneous wireless information and power transfer (SWIPT)-based distributed antenna system (DAS). Firstly, a DAS-SWIPT model is formulated, whose goal is to maximize the EE of the system. Next, we propose an optimal resource allocation method by means of the Karush-Kuhn-Tucker condition as well as an ergodic method. Considering the complexity of the ergodic method, a suboptimal scheme with lower complexity is proposed by using an antenna selection scheme. Numerical results illustrate that our suboptimal method is able to achieve satisfactory performance of EE similar to an optimal one while reducing the calculation complexity.

• 한국직업건강간호학회지
• /
• 제11권2호
• /
• pp.108-120
• /
• 2002

This study analyzed the managerial efficiency of 11 organizations, the branch centers of a occupational health service organization in Korea, using the Data Envelopment Analysis (DEA) method. The DEA is a good method for evaluating health services since it can handle multiple inputs and outputs simultaneously, and also identify the sources and amount of inefficiency. The author approached this study using two efficient models: the monetary value model and the real value model. The DEA method based on the monetary value model included cost factors, while the real value model excluded cost factors. The input variables used were manpower of physicians, medical technicians, nurses, industrial hygienists and administrators; labor, maintenance, and material expenses. The output variables used were the number of medical examinations, workplace evaluations, group health management services and income from each service. The major results were as follows: First, in the monetary value model, 6 out of 11 organizations (54.6%) showed an efficiency score of 1.0, which means that they have been operating in very efficient ways. However, 5 organizations (46.4%) showed themselves to be relatively inefficient. Second, in the real value model, 7 out of 11 organizations (63.4%) showed an efficiency score of 1.0, which means they have been operating efficiently, while 4 organizations (46.4%) showed themselves to be relatively inefficient. Third, the reliability of DEA method were analyzed by comparing the results of the monetary value model and real value model. The results of 8 out of 11 organizations were same in terms of being efficient or not. Thus, the DEA could be a valid application method for occupational health service organizations. Fourth, the organizations that displayed common inefficiency in both the monetary value model and in the real value model 3, 9, and 10, were also considered to be managed inefficiency from expertise opinion. In summary, this study evaluated the efficiency of occupational health service organizations applying the DEA method with different variables, and found that the results of analysis could be valid in terms of both modeling and expert sense. In the future, the DEA method will be used as a useful tool to identify and evaluate the efficiency of occupational health service organizations through more applications and refinements.

• 기술혁신연구
• /
• 제22권2호
• /
• pp.77-104
• /
• 2014

중소기업 R&D지원은 정책적으로 매우 중요하며 예산 또한 매년 증가하고 있다. 본 연구에서는 중소기업 R&D지원에 대한 성과를 종합적이고 체계적으로 분석할 수 있는 새로운 성과분석 방법을 제안하며 이 모델을 기반으로 중소기업청의 대표적인 R&D지원 사업에 대하여 실증분석하였다. 중소기업 R&D지원사업의 성과는 시차(time-lag)를 두고 발생하는데 이때, 단기적인 성과를 효율성, 중 장기적인 성과를 효과성으로 측정하였다. 효율성과 효과성을 나타내는 지표는 과거 선행연구를 기반으로 선정했으며 분석대상 사업별 사업목적, 취지, 내용 등의 특성을 반영하기 위해 지표별 가중치를 도출하였다. 이렇게 효율성과 효과성의 최종 점수가 도출되고 각 사업별 성과의 차이를 통계 검정하였다. 분석 결과, 중소기업청의 5개 R&D지원사업의 효율성은 통계적으로 유의한 차이를 나타냈으며 효과성은 통계적으로 차이가 없었다. 효율성 점수는 전반적으로 낮게 나타나며 효과성 점수는 보통이상으로 높은 수준을 보였다. 중소기업청의 R&D지원사업은 대체로 단기적인 성과인 효율성이 낮아 R&D수행상의 비효율을 초래하는 것으로 나타나는 반면, 중 장기적인 효과성에 대한 기대는 높아 R&D수행을 통한 사회경제적 파급효과는 클 것으로 예상된다. 그러나 효율성이 개선되지 않고는 지속적인 성과를 기대하기 힘들기 때문에 이에 대한 정책적 노력이 필요하다.

• Journal of Information Technology Applications and Management
• /
• 제27권1호
• /
• pp.1-13
• /
• 2020

This study aims to measure the efficiency and productivity change of 30 domestic construction companies from 2010 to 2018 using data envelopment analysis(DEA) and Malmquist productivity index (MI). In particular, we used the number of employees, capital stock, and non-current assets as input variables, and sales and net income as ouput variables for the analysis. The dataset used for the analysis of efficiency and productivity changes is the employee profile and financial statements for the companies from 2010 to 2018. We found that the MI of the 30 companies is greater than one since 2013. This is because many years of TEC (Technical Efficiency Change) is greater than 1, which means that the productivity index increases as the TEC increases. In addition, the MI value was less than 1, which lowered the productivity of construction firms in 2018. The results of the study may help decision makers to find effective future management plans by analyzing the internal and external factors.

• 수산해양기술연구
• /
• 제49권4호
• /
• pp.395-403
• /
• 2013

Fishing efficiency of the squid jigging vessel using the LED and metal halide fishing lamp combination was analyzed to reduce the cost for fishing operation utilizing the fishing light system for high degree of efficiency in the squid jigging fishery (one of the representative coastal and offshore fisheries in Korea). This study aims to improve the nature of existing LED lamps and to develop fan-shaped LED lights having 180W of power and ${\pm}45^{\circ}$ angle of light intensity distribution. The marine experiment for making a comparison of their fishing efficiency was tested by a 9.77 tons fishing vessel from Oct. through Dec. 2012. As a result, experimental fishing vessel showed slightly higher fishing efficiency than the average of metal halide lamp-equipped vessel and 20% energy savings. This means that the combination of LED and metal halide lamps would provide an efficient way to lower energy consumption while maintaining fishing efficiency.