• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.3
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• pp.96-104
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• 1983

In wire transmission systems using a coaxial cable or cable pair, the cable loss caused by the transmission characteristic of the cable varies depending on the length of the cables or variation in the ambient temperature, and usually takes the form close to a $\sqrt f$ characteristic. In order to compensiate for such loss, an actove variable automatic equalizer with a tandam combination of feedback and feedforward was presented. The automatic equalizer to be described here overcomes many of the disadbantages associated with the conventional passive variable equalizers, which include the need for inducters, a complex design procedure, and incompatibility with modern dldctronic control systems that are very complicated. This design has advanatges over other active variable equalizer design and it is especially applicable to precision equalization at frequencies bellow 1MHz.

• Journal of the Korea Computer Industry Society
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• v.2 no.2
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• pp.165-180
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• 2001

This study is on the design and performance evaluation of a multi medium access control(MAC) protocol for multimedia access in the wireless ATM network. In general, MAC protocols for multimedia data transmission are classified into the fixed slot allocation algorithm that allocates base-station slots equally over terminals, and the dynamic slot allocation algorithm that with flexible penetration. The conventional slot allocation algorithms assign slots based on the average bandwidths required for various services types. Although the algorithms have a wide bandwidth for real-time-variant services, the slots are being wasted due the service types. To improve the slot waste problem, this thesis proposes a method that minimizes the waste by assigning variable slots based on the most appropriate bandwidth after a base-station analyzes the service type requested from terminals.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.293-296
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• 1998

본 논문에서는 다양한 멀티미디어 서비스를 위해 가변율 half rate 음성 부호화기를 설계하였다. 유, 무성음과 묵음의 구분을 위해 본 논문에서는 프레임 에너지와 음성 파라메터들을 이용한 효과적인 voicing 결정 알고리즘을 사용하였다. 유성음을 위한 half rate 음성 부호화기는 저속에서 좋은 특성을 보이는 generalized AbS구조를 이용하였다. LPC 계수는 LSP 계수로 변환한 후 predictive 2-stage VQ를 통해서 양자화하며, 여기 신호는 음질저하를 최소화하며 복잡도를 감소시킨 shift 방식의 대수적 고정 코드북 구조를 사용하고, 적응코드북과 여기코드북의 이득은 VQ로 양자화 하였다. 무성음을 위한 부호화기는 대부분이 유성음을 위한 부호화기와 동일하지만, 무성음에서는 피치간 상관도가 매우 낮으므로 피치 보간 방법을 사용하지 않고 개루프로 피치 lag를 찾은 후 전체 프레임에 사용한다. 1 kb/s 부호화기는 묵음 구간과 주변소음 구간에 사용되며 이 구간의 신호를 피치 성분이 미약한 주변소음들로 제한하고 이에 최적인 부음성 부호화기를 설계하였다. 최종적으로 완성된 가변율 half rate 부호화기는 voice activity factor(VAF)가 0.47인 시험음성에서 약 2.6 kb/s의 평균 전송률을 보였다. 주관적 음질 평가의 일환으로 IS-96 표준 코덱인 가변율 8 kb/s QCELP와 A-B preference 시험을 실시하였다. 시험 결과 평균전송률이 약 2배인 가변율 8 kb/s QCELP 보다 우수한 음질 성능을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1177-1181
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• 2006

In this paper, we proposed the new wavelength tunable filter for wide tunability of fiber ring laser. The proposed filter consists of the cascaded connection of Fiber Reflection Mach-Zehnder Interferometer and Sagnac filter or of hybrid filter and fiber Reflection Mach-Zehnder Interferometer. The simulation shows that the continuous tunable range of 50nm can be obtained and that more stable single mode operation of ring laser can be expected due to narrow FWHM. of filter spectrum.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.11-16
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• 2016

In this paper, an experimental study on the aerodynamic characteristics of a variable span wing flying inside a channel guideway is accomplished using wind tunnel testing. A variable span wing with a NACA 0012 airfoil section was fabricated and actuated using a linear servo motor. The aerodynamic effects of 1) wing aspect ratio, 2) ground effect, and 3) the gap between the wingtip and the wing fence were investigated. It was found that both ground effect and wing fence gap increased lift. Also, the wing fence gap does not significantly affect drag. Therefore, it was found that a variable span mechanism can be used as an effective high lift device when flap use is limited.

• The Korean Journal of Applied Statistics
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• v.21 no.5
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• pp.727-738
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• 2008

If a cointegrating relation is affected by important economic and political events occurred in the sample period, the assumption of the time-invariant cointegrating vector is violated, which leads to the misrep-resentation of the actual relations between the variables. From such a viewpoint, this study utilizes the recursive estimation process in testing for the stability of the long-run equilibrium of the domestic stock market system and then attempts to develop the framework for stabilizing time-variant cointegraing relations by introducing the dummy variables where the structural changes are found to exist.

• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.153-156
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• 2004

광 전송 마이크로 셀룰라 시스템과 부반송파 다중 송신 시스템 같은 마이크로파 광 전송기술을 이용한 시스템들은 송신기의 비선형성에 의해서 발생하는 많은 왜곡 성분들, 특히 레이저 다이오드에서 발생한 왜곡 성분들에 의해서 많은 성능의 제한을 받는다. 이러한 왜곡 성분들을 제거하기 위해서 광 피드포워드 방식을 이용한 광 송신기를 제안하였다. 제작된 피드포워드 선형화 아날로그 광 송신기는 2.1 GHz 투톤 실험에서 38 dB의 IMD 개선 효과를 보였다. 여기에서 위상 천이기와 전압 가변 감쇄기는 신호 크기 허용오차를 0.1 dB, 위상 허용오차 $1^{\circ}$범위 이내에서 설계하였다. 이를 위해서 세밀한 위상과 크기의 조정이 가능한 위상 천이기와 전압 가변 감쇄기를 제작하였고, 측정한 결과, 전압 가변에 따른 위상 변화량과 크기 변화량은 각각 위상 천이기는 $90^{\circ}$, 전압 가변 감쇄기는 14 dB를 기록하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.579-582
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• 2011

Variable mechanism perceives height and location of the person who use Kiosk system then control the machine to proper height and location. In this paper, we propose ADALINE-Fuzzy logic system control method for control height and direction of the variable kiosk. To prove usefulness of proposed system, we performed Widrow-Hoff delta rule experiment and carried out examination and comparison of control performance about heigh and direction of the person using kiosk system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.97-106
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• 2005

Since traffic engineering in 1950's, 'speed control technology' has experienced tremendous growth and developed constantly. However, speeding remains a major safety concern on many roadways. Many crashes is believed to be the result of driving too fast. Recently the speed reduction device, the speed monitoring display with ITS technologies have developed and introduced in many countries including our nation, Korea. Therefore This paper describes an evaluation of the use of a speed monitoring display, speed limit sign, and school zone sign. Two conditions were evaluated; without installation of Speed Monitoring Display, in Operation of Speed Monitoring Display.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.28-36
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• 2016

Theoretical model of a variable thrust solid rocket motor with a pintle nozzle was derived. For the chamber pressure control, classical model linearization and proportional-intergral controller was used. And then two types of gain scheduling controller were suggested to imporve controller performance for the non-linear propulsion model. Considering characteristics of systems, control gains were scheduled by chamber pressure or free volume. Step responses of each controllers were compared. As a result, the proper control algorithm about characteristics of variable thrust rocket motor was suggested.