• Journal of Biosystems Engineering
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• 제19권4호
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• pp.291-300
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• 1994

It is desired to operate tractor engines at or near maximum torque much of the time in field operation to increase fuel efficiency. To do this it is necessary to reduce engine speed and to shift gears to higher ratios as frequently as possible. Because of load variations in most drawbar work and inconvenience in gear shift, however, gear-type transmission are usually set in one ratio at unnecessarily high engine speeds, and engine-torque variations are used to compensate for changes in drawbar load. As a result, the most of time the tractor is not operated efficiently in terms of fuel consumption and work output. The objective of this study was to develop an automatic control system which is able to operate a tractor equipped with gear transmission under the optimal condition in terms of fuel efficiency with automatic governor setting and gear shift. An indoor experimental test set which can be used to simulate tractor operation, control engine speed and transmission ratio was developed in the previous paper. In this paper, the performance of the optimal operation system is reported. Through a series of tests, it was found that the automatic control system for optimal operation of tractors with gear transmission had a satisfactory performance.

• 동력기계공학회지
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• 제11권4호
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• pp.12-17
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• 2007

Recently, many small and medium size diesel vehicles have been equipped with turbocharger and EGR system to get high performance and reduce $NO_x$ emissions but its application to heavy-duty diesel engine is not common yet. In this work, the simulation model for EURO-3 engine was developed using WAVE and then its performance and emission level were verified by comparing with experimental results. The possibility of current EURO-3 engine equipped with LPL EGR system which would be satisfied the EURO-5 regulation are examined. ESC 13 mode was chosen as the primary engine test mode, and the injection timing and fuel quantity were changed to compensate the lost engine performance caused by EGR. The system developed in this study shows that the current EURO-3 engine could satisfy EURO-5 $NO_x$ regulation by applying LPL EGR.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.193-198
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• 2000

For an inverter-driven compressor, the discharge temperature increased with a rise of frequency, Therefore, it is necessary to control the discharge temperature at high frequencies in order to obtain system reliability and efficiency. This paper describes the effects of liquid injection system on the performance of an inverter-driven scroll compressor. Experiments were performed at ASHRAE-T conditions. Frequency was altered from 45 to 105Hz. As results of the present work, the refrigerant discharge temperature fur the injection system was dropped approximately $10{\sim}20^{\circ}C$ as compared to those for the non-injection system. The COP of the compressor was improved approximately $0.8{\sim}9.3%$ at high frequencies(75, 90, and 105 Hz).

• 한국산학기술학회논문지
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• 제22권4호
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• pp.42-48
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• 2021

최근 4차산업혁명을 통해 융합 기술이 발달하면서, 국방 분야에서도 이러한 흐름을 바탕으로 무기체계의 첨단화, 고도화 등을 모색하고 있다. 하지만 첨단 기술을 바탕으로 개발되는 무기체계의 성능시험은 여러 변수들이 존재하며, 실제 운용환경에서 시험을 수행하기에 많은 어려움이 따른다. 이러한 문제점을 극복하기 위한 방안으로 M&S 자원을 적극 활용하여 그 성능을 입증하고 있으나, 사용 중인 M&S 자원의 신뢰성을 보증할 수 있는 수단을 추가로 요구하고 있다. 이에 따라 위한 VV&A 업무 수행을 통해 M&S 자원의 신뢰성을 확보하고 있다. VV&A 업무의 지속적인 요구와 수행으로 인해 관련 제도 등은 많은 발전이 이루어졌지만, 업무 수행을 위한 도구나 기법 등은 제도에 맞추어 발전하지 못하여 업무 수행에 있어 비효율적인 부분이 존재하며, 체계적인 시스템의 부재로 인하여 보안 등 여러 안전사고가 발생할 수 있는 위험성을 다수 내포하고 있다. 본 논문에서는 수행중인 국방M&S VV&A 업무의 문제점 분석을 통해 보다 효율적이고 안전한 방법을 모색하고, 이를 기반으로 업무의 발전방향을 제시하고자 한다.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.150-157
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• 2008

The main objective of this paper is to investigate the performance characteristics of a $CO_2$ air conditioning system for fuel cell electric vehicles (FCEV). The present air conditioning system for FCEV uses the electrically driven compressor and electrically controlled expansion valve for $CO_2$ as a working fluid. The experimental work has been done with various operating conditions, which are quite matching the actual vehicle's driving conditions such as different compressor speed and high pressure to identify the characteristics of the system. Experimental results show that the cooling capacity and coefficient of performance (COP) were up to 6.3kW and 2.5, respectively. This paper also deals with the development of optimum high pressure control algorithm for the transcritical $CO_2$ cycle to achieve the maximum COP.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.383-384
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• 2023

Using the CSI(Construction Safety Management Integrated Information) data, a comparative analysis was conducted by work type and construction cost according to whether the construction sites were subject to making a safety management plan or not. As a result, by type of work, the ratio of deaths in non-plan sites was high in mechanical facilities and earthworks, and the operation performance of the system was much higher in sites that were less than 5 billion won of construction cost.

• 한국의료질향상학회지
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• 제5권2호
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• pp.224-237
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• 1998

Background : This is an investigative study to analyse the importance of works perceived by Quality Improvement(QI) Coordinators and to evaluate their current work performances using the questionnaires developed by the investigator. Methods : The data were collected from 37 subjects over two weeks period from Oct. 1 to Oct. 17, 1998 and analysed by the descriptive statistics of SPSS program. The items of questionnaire are consisted of 13 work domains including 73 activities based on Quality Management(QM) Coordinator's job description of National Association for Healthcare Quality:data collection & analysis, communication, monitoring, evaluation, accreditation, tool development, policy development, program development, self development, education & trainning, system design, planning, and consultation & support. Results : 1) Of the performances in 13 work domains, the frequencies of the work performed were accreditation(89%), planning(88%), communication(83%), data collection & analysis(82%), monitoring(76%), policy development(72%), consultation & support (71%), education & trainning(70%), self development(68%), evaluation(63%), tool development(61%), program development(44%) and system design(43%) in order. 2) For the importances (1=not important, 5=very important), the policy development(4.46) scored highest then monitoring(4.42), planning(4.41), education & trainning(4.38), communication(4.35), evaluation(4.34) tool development (4.30), data collection & analysis(4.29), program development(4.22), consultation & support(4.22), accreditation(4.15), self development(4.05) and system design(3.98) in order. 3) There was a difference between the work performance and the perceived importance. The results showed the low performances in policy development, monitoring, education & trainning and evaluation which ranked high by the perceived importance and the high performances in accreditation, data collection & analysis, self development, communication and consultation & support which ranked middle to low by the perceived importance. 4) The reasons for low performances of QI Coordinators were the lack of clear assignment for the responsibility and allowed authority for work to QI Coordinators(30.8%), insufficient member of QI Coordinators(13.9%), lack of hospital director's interest(11.5%), low motivation of QI Coordinators (10.6%) and insufficient knowledge & experience of QI Coordinators (8.8%). Conclusion : Most works were perceived important by QI Coordinators, but there was a difference in the work performance. The works performed over 70% were related with accreditation, data collection & analysis, communication, planning and monitoring, on the other hand under 50% in performances were related with system design, program development, tool development and evaluation.

• 설비공학논문집
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• 제16권7호
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• pp.615-622
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• 2004

Recently, the hybrid system combining fuel cell and gas turbine has drawn much attention owing to its high efficiency and ultra low emission. It is now on the verge of world wide development and various system configurations have been proposed. A national project funded by Korean government has also been initiated to develop a pressurized hybrid system. This work aims at presenting design performance analysis for various possible system configurations as an initial step for the system development. Study focuses are given to major design options including the power ratio between gas turbine and fuel cell, reforming method (internal or external), reforming heat source (reforming burner, cathode hot air, fuel cell heat release) and steam supply method for reformer (anode gas recirculation, external steam generator). A wide variation in performance among different configurations has been predicted.

• 산업경영시스템학회지
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• 제11권18호
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• pp.59-69
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• 1988

This study represents the method of application of W.S(Work Sampling) to determine job sequence. The result shows job sequence which has the came performance measure of optimal job sequence is selected by average number of 199 sampling. In the case, the optimal job sequence is not selected within the sampling number of 921 which satisfy the reliability of 99.5% and precision of 99%, the deviation is very little which 0.73%. This improves the possibility of application of W.S method to select optimal job sequence is very high.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권3호
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• pp.207-220
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• 2011

Coarse-grained reconfigurable architecture (CGRA) based embedded systems aims to achieve high system performance with sufficient flexibility to map a variety of applications. However, the CGRA has been considered as prohibitive one due to its significant area/power overhead and performance bottleneck. In this work, I propose reconfigurable multi-array architecture to reduce power/area and enhance performance in configurable embedded systems. The CGRA-based embedded systems that consist of hierarchical configurable computing arrays with varying size and communication speed were examined for multimedia and other applications. Experimental results show that the proposed approach reduces on-chip area by 22%, execution time by up to 72% and reduces power consumption by up to 55% when compared with the conventional CGRA-based architectures.