• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.473-479
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• 2008

With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.272-274
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• 2011

최근 들어 케이블 방송망을 기반으로 한 디지털 방송, VoIP(Voice over Internet Protocol), VOD(Video on Demand), 영상전화, 이동전화, 무선 랜 로밍 등의 다양한 멀티미디어 서비스의 출현과 향후 도입될 새로운 융합형 멀티미디어 서비스의 수용을 위해 케이블 망의 고도화에 대한 요구가 제기되었다. 특히 유럽을 중심으로 이러한 요구를 만족시키기 위해 DVB(Digital Video Broadcasting)-C2 규격의 개발이 진행되었다. DVB-C2 규격에서는 기존의 게이블 전송 규격인 DVB-C에 대해 30% 이상의 전송 효율을 높이고자 새로운 변조 방식과 채널 오류정정 부호 방식을 도입하였다. 이에 본 논문은 본 논문에서는 DVB-C2 규격에서 도입된 채널 오류정정 부호인 BCH(Bose, Chaudhuri, and Hocquenghem) 부호와 LDPC(Low Density Parity Check) 부호의 연접 방식에 대한 성능을 검증하고자 한다. 이를 위해 개발된 시뮬레이터의 소개와 이를 통한 시험결과를 제시한다.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.2
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• pp.31-36
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• 2006

As two dimensional bar code can collect data and information quickly, it is used and recognized as a useful tool for the many industrial application field. But the information capacity of two dimensional bar code is still limited. Recently, the two dimensional AD bar code (analog-digital code) that can increase its application range and overcome capacity limitation is developed. In this paper, we implement an effective system which can transform text information into voice using two dimensional AD bar code and TTS(Text To Speech). It can be transmitted to blind people by capturing the AD bar code on the papers or the books.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.216-221
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• 2007

디지털 방송은 수많은 프로그램과 기존의 아날로그 방송에서 볼 수 없었던 다양한 서비스를 제공하며 발전하고 있다. 하지만 시청자들에게는 방송 서비스 채널과 기능이 많아질수록 원하는 채널을 검색하고 전환하는 과정이 어렵고 복잡한 일이 되어 버릴 수 밖에 없을 것이다. 이에 본 논문에서는 이러한 정보 획득과정의 축소를 위해 전통적인 리모콘으로 채널을 검색하고 이동하는 절차를 벗어나 음성인식을 통한 동적 EPG(Electronic Program Guide) 제어 시스템을 설계하고 구현하고자 한다. 이는 EPG정보와 시청자의 TV시청 성향 및 History를 기반으로 구동되는 시스템으로 음성대화의 구조적 정의가 가능한 VXML(VoiceXML) 인터프리터를 활용한다. 본 논문에서 제안하는 대화형 인터페이스는 다양한 디지털방송 서비스에 접목이 가능 할 것이며, 새로운 형태의 디지털 가전기기 파일럿 인터페이스 개발에 도움이 될 것이라 기대한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.236-241
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• 2008

With the advent of mobile phone, Digital multimedia broadcasting (DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion (THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.564-568
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• 2006

Smooth picture module is operated by vibration to tilt the light from the DMD (digital micro mirror device) of DLP projection TV, which makes the screen of the TV smoother and DMD chip cost lower. To satisfy the vibration characteristics of smooth picture module, it is designed by optimizing moment of inertia, spring constant and damping coefficient, using structural and fluid dynamic simulation that showed a good agreement with experimental data. To reduce the material cost and moment of inertia, engineering plastic is used and the reliability is estimated. A VCM (voice coil motor) type actuator for smooth picture has to satisfy performance requirements such as higher driving force, lower power consumption, and lower cost. The initial design and optimization for VCM was performed using FE analysis. It allowed us to optimize the design of magnetic circuit of the proposed actuator to obtain higher force while maintaining a lower cost.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.2
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• pp.51-58
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• 1993

This paper describes the development of a speaker-dependent isolated word recognizer as applied to voice dialing in a car noise environment. for this purpose, several methods to improve performance under such condition are evaluated using database collected in a small car moving at 100km/h The main features of the recognizer are as follow: The endpoint detection error can be reduced by using the magnitude of the signal which is inverse filtered by the AR model of the background noise, and it can be compensated by using variants of the DTW algorithm. To remove the noise, an autocorrelation subtraction method is used with the constraint that residual energy obtainable by linear predictive analysis should be positive. By using the noise rubust distance measure, distortion of the feature vector is minimized. The speech recognizer is implemented using the Motorola DSP56001(24-bit general purpose digital signal processor). The recognition database is composed of 50 Korean names spoken by 3 male speakers. The recognition error rate of the system is reduced to 4.3% using a single reference pattern for each word and 1.5% using 2 reference patterns for each word.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.159-164
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• 1998

We proposes a new detecting algorithm of DTMF tone for low bit ate vocoder so that we use DTMF tones for signalling inthe digital network. Using DTMF tones for signalling, we could not change the conventional IS-95 protocol and control the mobile phone. We apply the root finding to detection of formants and bandwidth to search whether DTMF tones or voice and moreover to find what's kinds of DTMF tones, for instance 1, 2, 3, ......., #, *, A, B, ...., etc. Consequently, proposed method has a good result which is 0.000944% average error rate. It is satisfied with rcommended error rate in ITU-T($\pm$1.8%).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2165-2172
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• 1998

Existing premises telecommucation wiring ad been installed for efficient telephone service. But premises wiring is currently ready to be reused as media for wideband digital services and Fiber-to-the-curb architecture. Electrical properties of premises wiring link have not characateized above frequencies for voice service. Accurte measurement of these characteristics are exssential for studies fof wideband ditital transmission system. On the other hand, the transmission qualities of premises wiring have been known to be worst in telecommunications access networks. So the knowledge of premises wiring sturucture as well as electrical properties is needed to improve the performance of premises wiring. In this paper, the structure of premises wiring is described in detail and electrical characteristics (characteristic impedance, SRL, attnuation, NEXT) about premises cables and stelecommucations link of representative apartment complex sare measured and naalyzed ove r16MHz range which is UTP Cat3 bandwidth.

• Korean Management Science Review
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• v.10 no.1
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• pp.107-125
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• 1993

Modern telecommunication switching systems are SPC(Stored Program Control) machines handling voice, data and other kinds of traffic, in an environment which tends to be fully digital switching and transmission. The throughput of such systems is determined by the real time capacity of its centralized or distributed control processors and by the traffic capacity of the switching network. Designers must verify the traffic and call processing capacity of the switching system and check its performance under traffic load before it is put into service. Verification of traffic and call processing capacity of switching systems is one of the problems treated by teletraffic studies ; teletraffic studies are based on stochastic process, queueing theory, simulations and other quantitative methods of decision making. This study suggests the general methodology to evaluate the throughput and performance of the ISDN switching system. TDX-10 ISDN switching system are employed to give illustrative examples of the methodologies discussed in this study.