• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.639-644
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• 2001

Sequence Code Division Multiple Access) and TDMA(Time Division Multiple Access) system. In this system, the narrowband TDMA signals can cause intolerant interferences to CDMA signals. In this paper, DS-CDMA/TDMA frequency sharing system have been analyzed in AWGN(Additive white Gaussian Noise), MAI (Multi Access Interference) and NI(Narrowband Interference) environment. Also, performance improvement has been obtained by adopting an adaptive notch filtering scheme using complex filter bank and CCI canceller.

• Annual Conference of KIPS
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• 2004.05a
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• pp.1577-1580
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• 2004

여러 응용 서비스를 유 무선을 포함한 다양한 네트웍을 통해 제공하기 위해서는 네트웍에 적응할 수 있는 서비스 형태가 요구된다. 그 가운데 멀티미디어 서비스의 경우 네트웍이 서로 다른 환경에 적응할 수 있는 해결책으로 트랜스코딩 기술이 제시되었다. 하지만, 트랜스코딩을 위해 필요한 복호 부호의 처리 과정은 실시간으로 제공되는 멀티미디어 스트리밍의 경우에 제약조건으로 작용하고, 이에 따른 처리 과정을 대폭 줄이는 일부 기술들은 사용자 측의 서비스 품질에 문제점을 안고 있다. 본 논문에서는 트랜스코딩을 통한 처리 과정과 사용자 측 서비스 품질의 두 가지 측면을 고려하는 frame dropping 시의 모션 벡터 합성 기법에 대해서 언급한다. 또한, 본 논문에서는 기존의 기법과는 달리 양방향 예측 프레임이 포함된 경우에도 적용할 수 있는 확장성을 제공한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.883-892
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• 2004

Recently, in order to improve high speed data transmission and spectral efficiency in wireless communication systems, the study on the combination OFDM and space-time coding is active. Also, a solution to improve system capacity in multiuser systems is to use adaptive antennas. In a system using STBC, the signals transmitted from two transmit antennas are superposed at the receive antenna and the interference between two transmit antennas of a user occures. Thus it is difficult to apply the conventional beamforming techniques for single antenna to the systems using space-time coding. In this Paper, we present the MMSE beanforming technique using training sequence for STBC-OFDM systems in reverse link and evaluate the performance by using various parameters in TU and HT channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1126-1132
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• 1999

In this paper, we consider the superposed 16-QAM CDMA system for subband coded (SBC) image transmissions. We divide the SBC image bit into two group according to its significance. First, we investigate the average bit error rate (BER) of the overall system when the significance of bits is ignored. Next, we investigate the optimal signal constellation and processing gain that maximizes the peak signal-to-noise ratio (PSNR) of SBC image, subject to a fixed power and bandwidth constraint. We examine the performance improvement over the conventional equal distane, equal processing gain system, and the equal error protection (EEP) system.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.140-145
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• 2023

When performing stress analysis for a nozzle in nuclear power plants, the nozzle loads should be determined conservatively. Existing stress analysis report of 3-D nozzle loads in nuclear power plants often provide only load magnitude not the sign (direction). Since calculated stress distribution depends on load direction, determining critical load directions for conservative stress analysis is crucial. In this study, an efficient method for determining critical load directions in nozzle loads is proposed. In the proposed method, stresses are firstly calculated using elastic finite element (FE) analysis for the uni-axial load in each direction. Then stress distributions for the multi-axial loads are analytically calculated using the principle of superposition. The calculated stress values are verified by comparing with FE analysis results under multi-axial loading. By using this method, the complex task of determining conservative load directions can be simplified.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.717-726
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• 2003

This paper presents the methods that design the Wavelet-based pitch detector for 2,4 kbps Harmonic-CELP Coder, and that achieve the effective waveform interpolation by decision window shape of the transition region, Waveform interpolation coder operates by encoding one pitch-period-sized segment, a prototype segment, of speech for each frame, generate the smooth waveform interpolation between the prototype segments for voiced frame, But, harmonic synthesis of the prototype waveforms between previous frame and current frame occur not only waveform errors but also discontinuity at frame boundary on that case of pitch halving or doubling, In addtion, in transition region since waveform interpolation coder synthesizes the excitation waveform by using overlap-add with triangularity window, therefore, Harmonic-CELP fail to model the instantaneous increasing speech and synthesis waveform linearly increases, First of all, in order to detect the precise pitch period, we use the hybrid 1st pitch detector, and increse the precision by using 2nd ACF-pitch detector, Next, in order to modify excitation window, we detect the onset, offset of frame by GCI, As the result, pitch doubling is removed and pitch error rate is decreased 5.4% in comparison with ACF, and is decreased 2,66% in comparison with wavelet detector, MOS test improve 0.13 at transition region.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.4
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• pp.124-137
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• 2018

The main purpose of this study is to find the hotspots of crimes that occur frequently in the space and to derive the appropriate CCTV installation location. One of the characteristics of crime is clustered around past occurrence area, and these crimes are strongly correlated. It is also possible to find the cause of the clusters and the variables that affect the crime through the history of the crime. In addition to the traditional OLS model, spatial differential model including spatial autocorrelation and spatial error model were used to select the variables influencing the five major crime rate, the theft rate and the foreign resident rate. The variables affecting the Five major crimes were positive (+) sign for the welfare and the rate of the bar cluster rate, and negative (-) for the street density. The CCTV area occupies 46% of the hotspots based on the overlapping of the areas where the elderly people are crowded, the bar cluster, many multicultural families, and the areas with low density of street lamps. It turned out. Taking into account the current CCTV operation, the total number of new cases to cover the risk point was 89.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.122-132
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• 2010

AT-DMB system has been developed to increase data rate up to double of conventional T-DMB in the same bandwidth while maintaining backward compatibility. The AT-DMB system adopted hierarchical modulation which adds BPSK or QPSK signal as enhancement layer to existing DQPSK signal. The enhancement layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of conventional T-DMB service coverage. But this causes the enhancement layer signal of AT-DMB susceptible to fading effect in transmission channel. A turbo code which has improved error correction capability than convolutional code, is applied to the enhancement layer signal of the AT-DMB system for compensating channel distortion. However there is a need for other solutions for better reception of AT-DMB signal in receiver side without increasing transmitting power. In this paper, we propose adaptive array antenna system with Eigen-space beamforming algorithm which benefits beamforming gain along with diversity gain. We analyzed the reception performances of AT-DMB system in indoor and mobile environments when this new smart antenna system and algorithm is introduced. The computer simulation results are presented along with analysis comments.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.4
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• pp.305-312
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• 2014

In this study, in order to quantitatively confirm walking rehabilitation degree, we analyzed EMG pattern simulated abnormal gait and normal gait by applying a curve fitting. We calculated the suitable high-order function for EMG signal, and classified them into 5 groups by using cluster analysis. Depending on the distance from normal pattern group, we listed the pattern group and then the distribution of each variables were confirmed. The amplitude-decreased pattern was the most similar to the normal pattern, but the reversed pattern showed the lowest similarity. Due to the smaller overlapping range, the distribution of the groups were possible to classify using the value of variable. The standard deviation of each term coefficient was compared to indicate the quantitative rehabilitation extent, and the higher value was confirmed as the pattern is close to the normal pattern. Consequently, the representation of quantitative rehabilitation extent is expected to contribute to the more effective rehabilitation method study.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.69-75
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• 2010

Advanced T-DMB(Terrestial DMB )system which is a new portable mobile broadcasting system has been developed to increase data rate up to double of conventional T-DMB in same bandwidth while maintaining backward compatibility, using hierarchical modulation method. The Advanced T-DMB system realize high qualification of conventional T-DMB system by adding BPSK signal or QPSK signal as enhanced layer to existing DQPSK signal. The enhanced layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of existing T-DMB service area. But this causes the enhanced layer signal of Advanced T-DMB susceptible to fading effect in transmission channel. In this paper we applied the duo-binary turbo code which has powerful error correction capability to the enhanced layer signal for compensating channel distortion. And the computer simulation results about the performance of the duo-binary turbo code in Advanced T-DMB system are presented along with analysis comments.