• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.839-850
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• 2002

A performance simulation program for the turboprop engine (PT6A-62), which is the power plant of the first Korean indigenous basic trainer KT-1, was developed for performance prediction, development of an EHMS (Engine Health Monitoring System) and the flight simulator. Characteristics of components including compressors, turbines, power turbines and the constant speed propeller were required for the steady state and transient performance analysis with on and off design point analysis. In most cases, these were substituted for what scaled from similar engine components'characteristics with the scaling law. The developed program was evaluated with the performance data provided by the engine manufacturer and with analysis results of GASTURB program, which is well known for the performance simulation of gas turbines. Performance parameters such as mass flow rate, compressor pressure ratio, fuel flow rate, specific fuel consumption and turbine inlet temperature were discussed to evaluate validity of the developed program at various cases. The first case was the sea level static standard condition and other cases were considered with various altitudes, flight velocities and part loads with the range between idle and 105% rotational speed of the gas generator. In the transient analysis, the Continuity of Mass Flow Method was utilized under the condition that mass stored between components is ignored and the flow compatibility is satisfied, and the Modified Euler Method was used for integration of the surplus torque. The transient performance analysis for various fuel schedules was performed. When the fuel step increase was considered, the overshoot of the turbine inlet temperature occurred. However, in case of ramp increase of the fuel longer than step increase of the fuel, the overshoot of the turbine inlet temperature was effectively reduced.

• 유통과학연구
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• 제17권5호
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• pp.85-94
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• 2019

Purpose - The purpose of this study is to analyze the impact of customer's communication on sales performance in the online market. Research design, data, and methodology - This study uses linear regression analysis to examine the effects of product review characteristics which are the result of customer's communication, on sales performance by using product reviews of online marketplace Amazon. Result - The increase in the number of product reviews positively affected sales performance. An increase in extreme opinions in the product review has a positive effect on sales performance. The product review length has a negative effect on sales performance. Conclusions - This study has shown the online marketplace customers' communication can influence sales performance using product review big data. This study contributed to the theoretical completeness by analyzing all the products of the book category in Amazon online market. This research will complement the theories regard to the customer behavior affecting sales performance. We expect the empirical analysis result will provide empirical help to sellers, online marketplace operators, and customers. In particular, the number of letters in the product may negatively affect sales performance, so sellers need to consider this effect carefully when exposing product reviews.

• 한국유체기계학회 논문집
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• 제15권6호
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• pp.51-57
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• 2012

Performance evaluation of a compressor is conducted to develop 500W class ultra-micro gas turbine (UMGT) for power generation. The performance evaluation is essential to check the performance of the components of UMGT, a radial turbine, a centrifugal compressor, an angular combustor and a shaft, which have been already designed in previous researches. The purpose of this study is to introduce the development process of the performance testing equipments of the UMGT and to present the results of compressor performance test. For the performance evaluation of the compressor, two test equipments are developed and the initial test equipment uses commercial static air bearings with long shaft. In the improved test equipment, static air bearing is improved to increase rotating speed and compressed nitrogen gas is used for utility gas of the static air bearing to supply compressed air in a stable and steady way. To increase rotating speed to 320,000 rpm, 80% speed of design speed, compressed air is provided to the turbine. The performance map of the compressor with the 50%, 60%, 70%, 80% speed of design point is presented. The results of the performance test of compressor show a good agreement with the results of 3D CFD.

• The Journal of Asian Finance, Economics and Business
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• 제8권4호
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• pp.909-916
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• 2021

The purpose of the research to analyze SMEs' technological innovation performance in the Special Region of Yogyakarta based on green supply chains. This study's technology innovation performance is influenced by environmental management practices, green supply chain integration, and supply chain knowledge-sharing. This research is important because many SMEs are underdeveloped in terms of technology innovation performance. Technology innovation performance shows that innovation has a multi-dimensional ecological performance in organizations. Therefore, SMEs' sustainable supply chain could be achieved by managing operations, support, and information by focusing on environmental and social issues to maximize the entire chain. This study used primary data. The number of respondents in this study was 200 SMEs that have implemented green supply chain management practices. The data collection method used was a questionnaire. The data analysis technique tool used is a two-step approach to SEM-AMOS. The results of this study indicate that SMEs are willing to implement a green supply chain to increase their performance. The technological innovation performance model of this study is acceptable. The findings of this research suggest that companies must be encouraged to maintain and increase the implementation of green supply chain integration and better supply chain knowledge-sharing with improved technological innovation performance enhancements.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.946-952
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• 2005

The $CO_{2}$ refrigeration cycle is expected to reduce the compressor work and increase the COP by applying two-phase ejector as a device for the recovery of dissipated expansion energy. In this study, the performance of the cycle was simulated and effects of the ejector shapes on the performance of the $CO_{2}$ refrigeration cycle were investigated. The following results were obtained through the cycle simulation. The COP of the $CO_{2}$ refrigeration cycle with two-phase ejector flow which expansion is occured in the isentropic manner is increased by a maximum of 24 $\%$ than the basic cycle with expansion valve If the velocity nonequilibrium in the mixing process is assumed the COP of the cycle is increased with the increase of the length and the decrease of the section area of the mixing tube. The best cycle performance is obtained when the divergent angle of diffuser is 7.

• Journal of Advanced Marine Engineering and Technology
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• 제18권2호
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• pp.91-96
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• 1994

Intake gases other than air, which is composed of oxygen, nitrogen, carbon dioxide, and argon, are used to study their effects on the performance of the diesel engine experimentally. The engine is operated at constant speed and fixed fuel injection timing, and cylinder pressure and heat release rate are measured at various intake gas compositions. The results show that increase of oxygen concentration improves the performance of the engine generally. The adverse effect is observed when the oxygen concentration is increased over the critical oxygen concentration of this test, mainly because of the over-shortened ignition delay. Increase of carbon dioxide concentration degardes the performance of the engine, mainly due to the lower specific heat ratio of carbon dioxide. Adding argon gas to the intake gas improves the overall performance. Finally, it is found that two most influencing factors affecting the performance of the diesel engine in this study are ignition delay and speific heat ratio of the intake gas.

• 산업경영시스템학회지
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• 제21권45호
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• pp.145-154
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• 1998

The effects of secondary task on driving performance and subjective workload were investigated during a simulated driving. The driving performance was determined by the appropriateness of break timing. The driving simulator was provided by the Korea Road Traffic Safety Association. The subjective workload was tested by using a multidimensional measure such as NASA-TLX. Road was categorized into two types: narrow alley and wide street. The secondary task included pushing the number on the cellular phone, pushing radio channel, and conversing with a passenger. Seventeen subjects volunteered in the study. The data were analyzed by using SAS. Results showed that using the cellular phone and pushing channel during driving caused 3∼22% decline of driving performance and 42∼59% increase of subjective workload respectively. These results indicated that the secondary task could be potentially dangerous although there was not a significant performance decrease due to the notable increase of mental workload. In the future, if we can use a more sensitive and realistic driving simulator, the effects of secondary task under a dynamic driving situation can be investigated.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권1호
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• pp.28-36
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• 2010

Hardware implementation methods for Artificial Neural Network (ANN) have been researched for a long time to achieve high performance. We have proposed a Network on Chip (NoC) for ANN, and this architecture can reduce communication load and increase performance when an implemented ANN is small. In this paper, a multiple NoC models are proposed for ANN, which can implement both a small size ANN and a large size one. The simulation result shows that the proposed multiple NoC models can reduce communication load, increase system performance of connection-per-second (CPS), and reduce system running time compared with the existing hardware ANN. Furthermore, this architecture is reconfigurable and reparable. It can be used to implement different applications of ANN.

• 한국태양에너지학회 논문집
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• 제23권2호
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• pp.43-49
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• 2003

The thermal performance of the glass evacuated tube solar collector is numerically investigated. The glass evacuated tube solar collector consists of a two-layed glass tube, a copper tube, and the working fluid. The length and the diameter of the glass tube are 1,200mm and 38mm, respectively. The diameter, thickness, and length of the copper tube and the flow rate of air are considered as the important design and operating parameters of the collector. The effect of these parameters on the thermal performance of the collector are investigated. The results show that as the diameter, the thickness, and the length of the copper tube increase and the flow rate of the air decreases, the thermal performance and the outlet mean temperature increase.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.1-9
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• 2004

The general method which changes sub-cooling of refrigerant is to control the expansion valve in the state of mixing with liquid and gas phase. In this study, the performance of vehicle air conditioning system is to control either changing the expansion valve or adding the sub condenser. Therefore, this research finally is tested in case of the fourth test procedure, the second test was suitable for a valve opening area due to adjusting valve slope in comparison with the other test. The other test except for the second test happened to do liquid back due to the excessively liquified refrigerant into the system. In conclusion, the second test was appeared not to be influenced upon liquid back, and it is to expect positive performance by controlling an expansion valve. Therefore, it will be also useful to research for an increase of compressor efficiency Performance improvement of an air conditioner is to reinforce the suction performance of the evaporator and increase the sub-cooling, which make use of the sub-cooling system.