• 동력기계공학회지
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• 제20권6호
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• pp.87-92
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• 2016

This research dealt with performance characteristics of OTEC system applying an ejector and additional pump. Each system using five kinds of working fluids was analyzed, and primary parameters with respect to entrainment ratio were examined: Turbine gross power, evaporation capacity, pump work, efficiency and volume flow ratio. The primary results were as following. The efficiency of ejector-pump OTEC system was dependent on entrainment of the ejector. The degree of efficiency change was different from applied working fluid, and amount of pump work was turned out to be primary factor affected system efficiency. Meanwhile, optimized entrainment ratio was different from applied working fluid since their different vapor density. System efficiency at optimized entrainmet ratio of each working fluid was around 5%, showing minor difference each other.

• 수산해양기술연구
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• 제50권1호
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• pp.83-88
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• 2014

A new shell divider was manufactured according to the principle of the lever in order to improve working efficiency in collecting the gonad of Sea Urchin, Anthocidaris crassispina, around the coast of jeju. It was composed of three parts of a pair of handles for grasping power, a fulcrum and a pair of knives for action with 21cm in length and 13cm in width. The operating efficiency of the shell divider was tested out in three place of Jeju coast. Statistical significances of differences of working time between test groups were calculated according to the t-test with the level of significance. In dividing the shell of sea urchin, the average of about 3 seconds of working time by the shell divider was less than that by a knife. At the result of t-test, the statistical significance in the working time existed between the divider group and the knife group. On the other hand, the working time among the divider operators showed no significant differences. It is concluded that the shell divider is more efficient than a knife in traditional operating.

• 한국농촌생활과학회지
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• 제8권2호
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• pp.111-117
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• 1997

In this study we tried to give a decision on propriety of working conditions, to present ideas on reducing work loads. and to grope for efficiency of agricultural works. For this we examined the actual conditions of working environment, farmer's clothes, working posture, working methods, working time, resting state, fatigue recovery methods during cultivating lettuce in the winter greenhouse. And Ive improved harmful factors that affect farmer's health by considering results of previous study and farmer's subjective sensation. And we measured, compared, and analyzed the farmer's work loads before and after improvement. The results of this study are as follows ; 1. According to examine the actual conditions of cultivating lettuce in the winter greenhouse, farmers have experienced physical and mental chronic fatigue on the basis of the hot and humid crops-centered working environment, the rough ground condition, inconsistent arrangement of working stand and sorter, heavy-weared habits. and unsuitable working posture. 2. When we improved harmful factors that affect farmer's health, conformed the positive effects on important work efficiency index such as heart rate, electromyovolume, body temperature, and microclimate inside clothing and work loads were decreased by improving the hot and humid working environment, eliminating the hillock and obstacles of working path. deliver way, arranging the working stand and sorter consistantly, decreasing the clothing weight, improving the working postures and methods as using assistant appliances, alloting the working time and sequence effectively and presenting the light gymnastic exercises and rest for fatigue restoration.

• Journal of Information Technology Applications and Management
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• 제25권4호
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• pp.23-39
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• 2018

The purpose of this study was to investigate empirically whether the expected effects of smart work in organizations were different between job types and positions. The development of information technology is demanding innovation of working style within the enterprise. There is a tendency to prefer the face-to-face working style in traditional organizations in the case of some positions or job types. However, many companies are carrying out smart work such as teleworking or telecommuting, flexible working time. But many companies still stick to their existing working methods. There is also the causal relationship between accepting attitudes toward smart work and expectation effects, depending on the position and the job types, even within the same organization. As a result of research, causal relationship analysis showed that the significant factors affecting productivity were teleworking and increasing work efficiency. The national social cost savings were influenced by the improvement of quality of life and flexible working hours. In order to activate communication within the organization, there was a positive effect on the increase of work efficiency. Only flexible working hours between the general manager and subordinates showed a significant difference.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.91-97
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• 2013

Recently a novel cycle named organic flash cycle (OFC) has been proposed which has improved potential for power generation from low-temperature heat sources. This study carries out thermodynamic performance analysis of OFC using various working fluids for recovery of low-grade heat sources in the form of sensible energy. Special attention is focused on the optimum flash temperature at which the exergy efficiency has the maximum value. Under the optimal conditions with respect to the flash temperature, the thermodynamic performances of important system variables including mass flow ratio, separation ratio, heat addition, specific volume flow rate at turbine exit, and exergy efficiency are thoroughly investigated. Results show that the exergy efficiency has a peak value with respect to the flash temperature and the optimum working fluid which shows the best exergy efficiency varies with the operating conditions.

• 한국농공학회지
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• 제32권E호
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• pp.74-79
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• 1990

Important factors in evaluating solar collcetor efficiency are solar radiation, temperature and flow rate of the working fluid. The effects of these factors on the energy and the exergy gained by water, the working fluid, from the collector were analyzed. The results indicated that the collector efficiency and the energy and the exergy gained by the water from the collcetor increased with the increase of solar radiation. According to the exergy analysis, as the water temperature at the inlet of the collector increased, the exergy gained by the water increased while the energy gained by the water decreased. The water temperature at the outlet of the collector could be calculated with a mean error of 2.8%, and the energy and the exergy could be calculated theoretically with mean errors of 16.8% and 19.1%, respcetively.

• International Journal of Advanced Culture Technology
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• 제3권2호
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• pp.58-66
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• 2015

This paper aims to compare the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle (ORC) Machine using Isopentane as working fluid expanding. The working fluid has boiling point below boiling water and works in low-temperature sources between $80-120^{\circ}C$ which can be produced from waste heat, solar-thermal energy and geothermal energy etc. The experiment on ORC machine reveals that the suitability of high pressure pump for working fluid has result on the efficiency of work. In addition, Thermodynamics theory on P-h diagram also presented the effect of heat sources' temperature and flow rate on any work. Thus, the study and design on ORC machine has to concern mainly on pressure pump, flow rate and optimized temperature. Result experiment and calculate ORC Machine using centrifugal Turbine efficiency better than Tesla turbine 30% but Tesla Turbine is cheaper and easily structure. Further study on the machine can be developed throughout the county due to its low cost and efficiency.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.129-130
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• 2011

2009 Presidential Council on National Competitiveness to plan trying to the advancement in the construction industry 'design and engineering of the global competitiveness' in the content of weak points of the design and engineering capabilities to secure the overall problem. In domestic technological of design and engineering behind the other building construction sector about 70%. Especially hindrance factor was founded between design ordering organization, design firm and subcontractor in working design stage. In this paper carried out to hindrance factor that decrease the efficiency in working design stage for a strategy to improve the utilization of basic data.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.863-867
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• 2020

This study was conducted on financial data of 38 economic groups listed on Vietnam's stock market for the period 2009 - 2019 and it aims to provide an empirical evidence on the impact of working capital management policy on performance in all phases of the economic cycle of Vietnamese economic groups. The study uses FGLS estimation method with 2 dependent variables ROA, GOP, independent variables including INV, AR, AP, CCC, dummy variable representing different phases of the economic cycle, variables Control includes CAT, CR, LEV, SZ, GR. Research shows that the greater the level of investment by companies in liquid assets corresponding to a certain level of activity (shown by average days of inventory (INV), average days of collection. (AR), cash flow cycle (CCC)) the lower the rate of return on assets. The study also provides additional evidence of the negative effects of economic crisis on the performance of economic groups. The study also shows that the number of short-term asset cycles has a positive impact on operational efficiency, and the level of debt use has a negative impact on operational efficiency. This result implies that the managers of economic groups can increase the efficiency of businesses through a reasonable working capital policy.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.223-231
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• 2011

The thermal efficiency of energy-to-power conversion becomes uneconomically low when the temperature of heat source drops below $370^{\circ}C$. ORC (Organic Rankine Cycle) has attracted much attention in last few years due to its potential in reducing consumption of fossil fuels and relaxing environmental problems, and its favorable characteristics to exploit low-temperature heat sources. In this work thermodynamic performance of ORC using nine working fluids is comparatively assessed. Special attention is paid to the effect of system parameters such as turbine inlet temperature and pressure on the characteristics of the system such as volumetric flow rate and quality at turbine exit, latent heat, net work as well as thermal efficiency. Results show that in selection of working fluid it is required to consider various criteria of performance characteristics as well as the thermal efficiency. Results also show that the system efficiencies become same irrespective of kind of working fluid when the temperature of heat source decreases to low range.