• Title/Summary/Keyword: Working efficiency

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Performance Analysis of Ejector-Pump Thermal Energy Conversion System Using Various Working Fluids (이젝터-펌프 온도차발전시스템의 작동유체별 성능분석)

  • Yoon, Jung-In;Seol, Sung-Hoon;Son, Chang-Hyo;Choi, Kwang-Hwan;Kim, Young-Bok;Lee, Ho-Saeng;Kim, Hyeon-Ju;Moon, Jung-Hyun
    • Journal of Power System Engineering
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    • v.20 no.6
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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.

Analysis on operating efficiency of shell divider using the principle of the lever for the purple sea urchin, Anthocidaris crassispina (지렛대 원리를 이용한 성게 껍질 분할기 작업 능률 분석)

  • Park, Young-Seok;Kim, Byung-Yeob;Lee, Chang-Heon
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.50 no.1
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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.

A Study for Farmers to Reduce Work Load on the Different Working Conditions (part I) - Cultivating Lettuce in the Winter Greenhouse - (농민의 작업환경별 노동부담 경감방안에 관한 연구(I) -겨울철 비닐하우스에서 상추재배 작업을 중심으로-)

  • 김명주;최정화
    • Korean Journal of Rural Living Science
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    • v.8 no.2
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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.

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An Exploratoy Study on Influence Factors for Expectation Effect of Smart Work and the Attitude Difference between Positions and Job Types (스마트워크의 기대효과 영향요인과 직급/직무 간 수용태도 차이 간 탐색연구)

  • Park, Kiho
    • Journal of Information Technology Applications and Management
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    • v.25 no.4
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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.

Characteristics of Thermodynamic Performance of Organic Flash Cycle (OFC) (유기 플래쉬 사이클(OFC)의 열역학적 성능 특성)

  • Kim, Kyounghoon;Jung, Youngguan;Park, Sanghee
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.1
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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.

Exergy Analysis of Solar Collector

  • 이석건;이현우
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.32 no.E
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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.

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A comparing on the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle

  • Thawichsri, Kosart;nilnont, Wanich
    • International Journal of Advanced Culture Technology
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    • v.3 no.2
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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.

A study on the hindrance factors for improving efficiency of the working design (실시설계단계 효율성 향상을 위한 저해요소 분석 - 'ㅇㅇ동 문화 및 집회시설' 사례를 중심으로 -)

  • Kim, Sung-Sik;Park, Jung-Lo;Kim, Ju-Hyung;Kim, Jae-Jun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2011.11a
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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.

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A Study on the Efficiency Improvement of the Power Generation Process Using New Working Fluids Composed of Methane, Ethylene, Ethane, and Propane and the Cold Heat Contained in the Liquefied Natural Gas (메탄, 에틸렌, 에탄 및 프로판으로 구성된 새로운 작동 유체와 액화 천연가스의 냉열을 활용한 발전 공정의 효율 향상에 대한 연구)

  • JUNGHO CHO
    • Transactions of the Korean hydrogen and new energy society
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    • v.35 no.3
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    • pp.318-323
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    • 2024
  • In this paper, computer modeling works have been performed for the power generation Rankine cycle using new working fluids and liquefied natural gas (LNG) cold heat. PRO/II with PROVISION released January 2023 from AVEVA company was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle. Optimal working fluid composition was determined to maximize LNG cold heat to increase power generation efficiency and net power production.

Impact of Working Capital Management on Firm Performance in Different Business Cycles: Evidence from Vietnam

  • NGUYEN, Co Trong
    • The Journal of Asian Finance, Economics and Business
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    • v.7 no.12
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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.