• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.36-46
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• 2000

The performance improvement and emission reduction in a turbocharged D.I. diesel engine was studied experimentally in this paper. The system of intake port, fuel injection and turbochager are very important factors which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. Through these experiments it can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, fuel injection system and turbocharger. The swirl ratio of intake port was modified by hand-working and measured by impulse swirl meter. Through this steady flow test, we knew that the increase of swirl ratio is decreasing the mean flow coefficient, whereas the gulf factor is increasing. And the optimum results of engine performance and emission are as follows; the swirl ratio is 2.43, injection timing is BTDC 13。 CA, compression ratio is 16, combustion bowl is re-entrant 5$^{\circ}$, nozzle hole diameter is $\Phi$0.28＊6, turbocharger is GT40 model which are compressor A/R 0.58 AND turbine A/R 1.19.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.505-512
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• 2011

Recently, many researchers have analyzed the performance of the transcritical $CO_2$ refrigeration cycle in order to identify opportunities to improve the system energy efficiency. The reduction of the expansion process losses is one of the key issues to improve the efficiency of the transcritical $CO_2$ refrigeration cycle. In this study, the analytical study on the performance characteristics of $CO_2$ cycle with an ejector carried out with a variation of outdoor temperature, gascooler inlet air velocity, evaporator inlet air velocity, and evaporator inlet air temperature. As a result, the system performance could be improved over 85% by using an ejector for various operating condition because of the reduction of compressor work. Moreover, the cooling capacity increased about 18% for variable outdoor condition. Therefore, the high performance of an ejector system could be maintained for wide operating conditions and system reliability could be improved compared to that of a basic system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.108-113
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• 2006

Recently, Automobile manufactures have developing automotive exhaust system under consideration for improvement in engine performance. It thus develop many exhaust components. For example active muffler, semi-active muffler, electronic muffler etc. In this components consider enhanced back pressure and reduction noise. Especially, In recent years it develop the study of semi-active muffler. Semi-active muffler is simple structure and excel performance. Recently many forms semi-active muffler was developed and adopted to the actual use in consideration of cost and technical side for noise and vibration. This study had main objects about the recently developed the semi-active muffler. It was to show its combustion performance as well as its enhanced back pressure characteristics in design. Therefore if the precise analysis of the combustion pressure according to the back pressure transmission was carried out, it was understood that this study would be utilized in the design of the exhaust system such as the semi-active muffler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.334-337
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• 2005

The speech intelligibility is one of the most important factors in communication system. The speech intelligibility is related with speech to noise ratio. To enhance the speech to noise ratio, background noise reduction techniques are being developed. As a part of solution to noise reduction, this paper introduces directional microphone using beamforming method and speech filtering method. The directional microphone narrows the spatial range of processing signal into the direction of the target speech signal. The noise signal located in the same direction with speech still remains in the processing signal. To sort this mixed signal into speech and noise, as a following step, a speech-filtering method is applied to pick up only the speech signal from the processed signal. The speech filtering method is based on the characteristics of speech signal itself. The combined directional microphone and speech filtering method gives enhanced performance to speech intelligibility in communication system.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.371-378
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• 2002

The design concepts using vibration reduction techniques, or structural control, have been proposed recently to protect infrastructure against earthquakes. The magnetorheological(MR) fluid damper is one of the most promising new devices for structural vibration reduction because of its mechanical simplicity, high dynamic range, low power requirement, large force capacity and robustness. In this study, the seismic performance of MR devices are compared with that of NZ systems as an attempt to provide some data for improving seismic design techniques applied to structures. For nonlinear time domain analysis of a base isolation system, a six-story building model is considered as a numerical example. The ground acceleration data of El Centre 1940, Mexico City 1985 and Kobe 1995 earthquakes are used as seismic excitations. The results show that MR damper systems for outperform NZ systems in wide-ranging seismic excitations with respect to intensity and period characteristics.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1085-1090
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• 2007

In recent railway construction, the concrete slab track is getting highlighted as main stream in track type. However, it is the fact that there are different opinions in selection of the optimized spring coefficient of elastic pad. In this study, the performance of vibration reduction in different stiffness of rail pad for ballasted track was compared, and the changes in characteristics, such as static/dynamic deflection of components, vibration acceleration, insertion loss etc., were analysed by using ISI Program for various types of rail fastening system used in concrete slab track. It was concluded that the fastening system with softer pads has shown the better performance of vibration reduction in concrete slab track and the optimized static stiffness has been calculated to 21.1kN/mm for conventional railways, 17.6kN/mm for high-speed railways and 17.8kN/mm for subways.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.3
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• pp.215-220
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• 1997

CNG dual fuel engine for heavy duty diesel engine developed by AFS International in Canada has been equipped to a Korean city bus engine and tested to compare the engine performance and the emission characteristics with the existing diesel fueled engine. Also the dual-fuel engine was applied to the city bus for road test. The results are summarized as follows. Performance optimization has been carried out to have engine power equivalent to or better than the diesel fueled engine. Smoke is decreased by 85% by Korean smoke 3 mode test. By 13 mode test CO is increased by 453% and THC is increased by 2, 086%. NOx is decreased by 7% in laboratory. D-13 test mode was changed in 1996 Korean regulation. Even though THC is increased very much, it's not too serious problem since CO and HC emission of diesel engine is very little compared to gasoline engine and more than 75% of THC is CH$_4$. But the reduction technologies of CO and HC has to be considered.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.659-664
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• 2006

It is one of the most effective method for improving the performance of electric railway vehicles to make better the wheel-rail adhesion characteristics. To study adhesion characteristic is to develop the equivalent reduction machine to experiment on the adhesion system. The experiment system makes it possible to change the wheel-rail adhesion force with various adhesion parameters, and therewith to test the adhesion control system with the reduction machine in a laboratory. In this paper for improving adhesion performance show actually control methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.541-544
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• 2005

In this paper, admittance is introduced to represent electro-mechanical characteristics of piezoelectric structures and to predict the performance of piezoelectric shunt system. Finite element method is used to obtain numerical admittance. In order to illuminate the effect of noise reduction in the shunt system, two experimental setups were constructed. One is for matching the resonant shunt damping. The other is a standard test setup according to SAE J1400 used to measure the transmission loss for the smart panel with shunt circuit. Shunt performance and noise reduction of smart panel are realized by these two experiments.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.1
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• pp.74-83
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• 2007

These days business logistics has become one of the very important factors of logistics cost reduction and customer service satisfaction. In order to control business logistics more effectively, many companies must be concerned about logistics performance.This study aims at analyzing information system characteristic and logistics performance. The information system characteristic variables are considered IS resource, IS strategic role. The logistics performance variables are considered logistic cost, customer service.For data on the 301 sampled company, a mail survey using a questionnaire was conducted in this study. The following results were obtained.First, IS characteristic variables were significant for logistics performance. Specially, efficient management of IS manpower and IS planning, present IS were significant for logistics performance. Second, there also were IS manpower and IS planning, present IS that indentifing high logistics performance group and low logistics performance group.