• ETRI Journal
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• v.29 no.3
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• pp.300-304
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• 2007

This paper proposes a new data-driven method for high-pass approaches, which suppresses slow-varying noise components. Conventional high-pass approaches are based on the idea of decorrelating the feature vector sequence, and are trying for adaptability to various conditions. The proposed method is based on temporal local decorrelation using the information-maximization theory for each utterance. This is performed on an utterance-by-utterance basis, which provides an adaptive channel normalization filter for each condition. The performance of the proposed method is evaluated by isolated-word recognition experiments with channel distortion. Experimental results show that the proposed method yields outstanding improvement for channel-distorted speech recognition.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.471-476
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• 2001

The characteristics of conjugated heat transfer in the inclined channel was experimentally investigated. The simulated module is attached to the bottom of the inclined channel and is heated with constant heat flux. The experimental parameters of this study are input power (Q = 3, 7W), inlet air velocity ($V_{i}=0.1{\sim}0.9m/s$) and inclined channel angle (${\varphi}=0{\sim}90^{\circ}$). The results show that input power was most effective parameter on the temperature differences between module and air. As the inclined channel angle increases, the temperatures of the module are increased. And we obtained the best condition on the conductive board when ${\varphi}=0^{\circ}$.

• Journal of information and communication convergence engineering
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• v.9 no.3
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• pp.251-255
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• 2011

In this paper, we investigate an adaptive cognitive radio (CR) scheme where a sensing duration and a detection threshold for spectrum sensing are adaptively determined according to the channel condition in a fading channel. We optimize the sensing duration and detection threshold of a secondary user to maximize the performance of the secondary user guaranteeing a primary user's secure communication. In addition, we analyze the effect of channel fading on the optimization of the sensing duration and detection threshold. Our numerical results show that the performance of the adaptive CR scheme can be drastically improved if a secondary user can take the advantage of channel information between primary and secondary users.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.233-236
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• 2012

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As a results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict the performance and evaluate a mini channel heat exchanger.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.867-872
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• 2016

We have investigated the channel mobility of AlGaN/GaN-on-Si recessed-metal-oxide-semiconductor-heterojunction field-effect transistors (recessed-MOS-HFET) with $SiO_2$ gate oxide. Both field-effect mobility and effective mobility for the recessed-MOS channel region were extracted as a function of the effective transverse electric field. The maximum field effect mobility was $380cm^2/V{\cdot}s$ near the threshold voltage. The effective channel mobility at the on-state bias condition was $115cm^2/V{\cdot}s$ at which the effective transverse electric field was 340 kV/cm. The influence of the recessed-MOS region on the overall channel mobility of AlGaN/GaN recessed-MOS-HFETs was also investigated.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.239-242
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• 2003

Transmit diversity using STBC(Space Time Block Code) provides the same diversity gain as MRRC(Maximal Ratio Receiver Combining), when the fading channel is constant across two consecutive symbols. But, when the channel condition is changed for the two consecutive symbols, the transmit diversity using STBC does not offer good performance due to the large doppler shift. In this paper, we have proposed a interference cancellation scheme for performance enhancement in transmit diversity using STBC over time selective fading channel. Simulation results for various doppler shift rates are presented for the transmit diversity using the proposed scheme.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.68-73
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• 1996

The full incompressible Navier-Stokes equations are numerically integrated to solve the unsteady channel flow using a new numerical scheme of second-order accuracy developed by the authors. It is well known that in spite of the symmetry in the boundary condition and geometry, asymmetry can develop with time-dependency in a channel with sudden expansion. The instability of the shear flow and the cross-channel pressure contribute to such asymmetric flow. In this paper, we successfully generated a channel flow in which vortex waves were propagated downstream due to the harmonically oscillating inlet flow. The structure of the eddies and wall vorticity are parametrically investigated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1448-1458
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• 1997

In this paper the reverse link of the GLOBALSTAR-the representative CDMA LEO satellite system and LEO mobile satellite channel are developed by the SPW software simulation tool. And the performance of the system is evaluated. GLOBALSTAR is designed to give cellular-type service to hand-held user terminals through a constellation of 48 LEO satellites in circular orbites with 1414 Km altitude. Since LEO mobile satellite system communicates with mobile unit, it is suffered from severe multipath fading and shadowing. The fast mobility of LEO satellites makes the channel condition time vering. So, the LEO mobile satellite channel is different from land mobile channels. In this unique LEO satellite channel, it is shown that the performance of the GLOBALSTAR reverse link is varied according to the elevational angle, but this variation is overcome by satellite path diversity.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.1
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• pp.44-49
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• 2011

The need of data transmission in oceans and other underwater mediums are increasing day by day, so as the research. The underwater medium is very different from that of air. Propagation of electromagnetic wave in water or underground is very difficult because of the conductivity of the propagation materials. In this case, we usually use acoustic signals as ultrasonic but, they are not easy to transfer long distance with coherent method because of time varying multipaths, Doppler effects and attenuations. So, we use non-coherent methods such as FSK or ASK to communicate between long distances. But, as the propagation speed of acoustic wave is very slow, BW of the channel is narrow. It is very hard to guaranty the enough speed for the transmission of digital image data. In previous studies, we proposed this data communication protocol theoretically. In this paper, an underwater channel is modeled and this protocol is tested in this channel condition. The results show that the protocol is 4-6 times faster than ASK. Some relations and results are shown depending on the data length, channel length, bit rate etc.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.4
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• pp.133-140
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• 2004

This study deals with human reaction speed according to human physical conditions (body size) such as head width, thickness, breast width, arm extent, and age. Especially, the results of this study are compared between young and old generation. According to this study, the thickness and extent factor do not have any correlation with human reaction speed, but width factors(head width, breast width, etc) have some correlation with human reaction speed. The result of this study can be used to find fitter person for a special job such as emergency condition job, sports man (because you can find a person having a good talent for it without test). Also, the purpose of this study is to find CNT (Channel Noise Time). The word of CNT is to explain the relation between Channel Noise and working speed. (Channel Noise is a kind of noise happening between the human information transmission channel.)