• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.227-233
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• 2002

For the purpose of high outlet pressure, compactness and low vibration and noise, modem reciprocating air compressors are tend to have a multi-stage W-type or V-type cylinder arrangement. An effective counter weight calculation method is presented for reducing the inertia forces of the compressor. This calculation method is using the complex representation and verified its validity. A design program for the counter weight of W-type or V-type air compressor was presented to the manufacturer, A designed counter weight was attached to the W-type or V-type air compressor. Vibration test results gave us improved performance.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.29-34
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• 2002

TIn this study, the counter-jet flows which designed for improvement of aerodynamic performance of the blunt body vehicle have been analyzed. The variations of the drag force and jet penetration depth due to changes in the stagnation properties of counter jet new such as total pressure, mach number, and total temperature. The counter jet flow, which is injected toward incoming supersonic freestream at stagnation region of blunt cone-cylinder vehicle, have been studied by using upwind flux difference splitting navier-stokes method. The changes in the stagnation pressure and Mach number resulted in large effects on the wall pressure and drag force, on the other hand tile total temperature changes did not.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.101-103
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• 1994

This report describes CRDCM(Counter Rotating DC Motor) that we have designed, manufactured and tested. CRDCM have two rotating rotors: one is a outer rotor as field set, another is a inner rotor as armature set. One of the most difficult problem is an elimination of the centrifugal force acting on brush when outer rotor is rotated. We solved a problem for centrifugal force of commutation brush by compensation set of counter mass through trial and error. It was verified the performance of motor at present.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.732-739
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• 2016

In Korea, the summer is hot and humid, and much electricity is consumed for air conditioning. Thus, the simultaneous usage of an indirect evaporative cooler and a common air conditioner could reduce the sensible heat and save electricity. This study developed a U-type cross-counter flow indirect evaporative cooler (IEC) made of plastic and paper. The efficiencies were compared with those of a cross-flow IEC. The specimen was $500mm{\times}500mm{\times}1000mm$. the results show that the indirect evaporation efficiencies of the cross-counter flow sample were 6-21% higher than those of the cross-flow sample. The pressure drops of the cross-counter sample were 51-66% higher. Thermal analysis based on the -NTU method predicted the experimental data within 10%. The electrical energy saved by the use of the cross-counter flow IEC was larger than that of the counter flow IEC, and the difference increases with the velocity. However, the the cross-counter IEC is two times larger than the cross-flow IEC, which may increase the material cost and water usage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.999-1011
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• 2015

In modern electronic warfare, RADAR is under constant threat of ECM(Electronic Counter Measures) signals from nearby jammers. The conventional linear frequency modulated(Linear-FM) waveform is easy to be intercepted to estimate its signal parameters due to its periodical phase transition. Recently, APCN(Advanced Pulse Compression Noise) waveform using random amplitude and phase transition was proposed for LPI(Low probability of Intercept). But random phase code signals such as APCN waveform tend to be sensitive to Doppler frequency shift and result in performance degradation during moving target detection. In this paper, random phase and code rate transition based radar waveform(RPCR) is proposed for Doppler tolerance improvement. Time frequency analysis is carried out through ambiguity analysis to validate the improved Doppler tolerance of RPCR waveform. As a means to measure the vulnerability of the proposed RPCR waveform against LPI, WHT(Wigner-Hough Transform) is adopted to analyze and estimate signal parameters for ECCM(Electronic Counter Counter Measures) application.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.615-623
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• 2005

In this research, an effective technique was examined to improve the drift running performance. Concretely, the driver model by which the counter steer was done was assumed to the model by which the vehicle body slip angle (and the vehicle body slip angle velocity) was feed back. Next, the effectiveness of the system which added the assist steer angle corresponding to the steering wheel angle velocity to a front wheel steer angle was clarified as a drift running performance improvement technique of the vehicle. As a result, because the phase advances when the differentiation steer assistance is added, it has been understood to be able to cover the delay of the counter steer when the drift running. Therefore, it has been understood that the drift control does considerably easily. Moreover, it has been understood that the differentiation steer assistance acts effectively at the drift cornering by which the drift angle is maintained in cornering and the severe lane change with a drift at a situation. That is, it was understood to be able to settle to the drift angle of the aim quickly at the time of the drift cornering because the delay of the control steer angle of the counter steer was improved. Moreover, it was understood for the transient overshoot of the vehicle tracks to be able to decrease, and to return to the state of stability quickly at the severe lane change.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.16-25
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• 2004

The flow and heat/mass transfer in the falling-film of a heat exchanger can be influenced by the motion of the surrounding refrigerant vapor. In this study, the effect of the vapor flow direction on the absorption heat transfer has been investigated for a falling-film helical coil which is frequently used as the absorber of ammonia/water absorption refrigerators. The experiments were carried out for different solution concentration. The heat and mass transfer performance was measured for both parallel and counter-current flow. The effect of vapor flow on the heat and mass transfer is found to be increased with decreasing solution concentration. In the experiments with low solution concentration, whose vapor specific volume is great, the counter-current flow of vapor resulted in uneven distribution of falling-film and reduced the heat transfer performance of the absorber. The direction of the vapor flow hardly affected the thermal performance as the solution concentration became stronger since the specific volume of the ammonia/water vapor was much smaller than that of the water vapor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.895-901
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• 2016

Nowadays, the axle counter has been developed to the wide range of the track circuit blocks as well as the wheel detection device. The axle counter, as becoming an important device for the high speed railway, must be guaranteed in accordance with the safety. With considering the safety and the high speed, performance evaluation a wheel detection sensor is described in this paper. To increase the safety, digital proximity sensor instead of analog is employed in the wheel detection sensor. Therefor the wheel detection sensor can minimize noisy signals caused by the harsh railway environments. And, to meet the high speed railway requirements, the performance of the wheel detection sensor is also successfully verified using the speed simulator at the velocity 500Km/h.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.5
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• pp.42-48
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• 2008

In this paper, we have introduced a Code Division Multiplexing transmission method which is similar to OFDM and analyze ECCM performances. We have verified CDM transmission method has a good LPI performance and a feasible ECCM performance. This capability could be useful for reduction of RF interference which occurs when many equipments operate densely in small area. The equipment that uses CDM transmission method supports variable transmission rate and order-wire effectively and conveniently to user. This CDM method has similar ECCM performance comparing to serial DS method. CDM method has good multi-path signal processing capability and could be useful for mobile communication environment.

• Journal of Computing Science and Engineering
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• v.7 no.4
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• pp.285-299
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• 2013

To enable hard real-time systems to take advantage of multicore processors, it is crucial to obtain the worst-case execution time (WCET) for programs running on multicore processors. However, this is challenging and complicated due to the inter-thread interferences from the shared resources in a multicore processor. Recent research used the combined cache conflict graph (CCCG) to model and compute the worst-case inter-thread interferences on a shared L2 cache in a multicore processor, which is called the CCCG-based approach in this paper. Although it can compute the WCET safely and accurately, its computational complexity is exponential and prohibitive for a large number of cores. In this paper, we propose three counter-based approaches to significantly reduce the complexity of the multicore WCET analysis, while achieving absolute safety with tightness close to the CCCG-based approach. The basic counter-based approach simply counts the worst-case number of cache line blocks mapped to a cache set of a shared L2 cache from all the concurrent threads, and compares it with the associativity of the cache set to compute the worst-case cache behavior. The enhanced counter-based approach uses techniques to enhance the accuracy of calculating the counters. The hybrid counter-based approach combines the enhanced counter-based approach and the CCCG-based approach to further improve the tightness of analysis without significantly increasing the complexity. Our experiments on a 4-core processor indicate that the enhanced counter-based approach overestimates the WCET by 14% on average compared to the CCCG-based approach, while its averaged running time is less than 1/380 that of the CCCG-based approach. The hybrid approach reduces the overestimation to only 2.65%, while its running time is less than 1/150 that of the CCCG-based approach on average.