• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1984년도 추계학술발표회 논문집
• /
• pp.100-106
• /
• 1984

Traditional methods for estimating the location of underwater target, i.e. the triangulation method and the wavefront curvature method, have been utilized. The location of a target is defined by the range and the bearing, which estimates can be obtained by evaluating the time delay between neighboring sensors. Many components of error occur in estimating the target range, among which the error due to the fluctuation of heading angle is outstanding. In this paper, the wavefront curvature method was used. We considered the error due to the heading fluctuation as the $\beta$-density process, from which we analized the range estimates with $\beta$-density function exist in some finite limits, and its mean value and variation are depicted as a function of true range and heading fluctuation. Given heading angles and sensor separation, maximum estimated heading errors are presented as a function of true range.

• 전기학회논문지
• /
• 제58권3호
• /
• pp.523-530
• /
• 2009

This paper presents a study on a small scale single-phase UPFC preliminary researches on power quality compensating schemes of electrical railway. As the UPFC is very complicated power-electronic system consisting of grid-connected transformers, four single phase inverters interconnected with dc-link capacitors and various electrical apparatuses, multiple controllers and control algorithms are needed, and entire UPFC has been modelled in the form of block diagrams and simulated by using Simulink. The main purpose of the compensating system is to manage reactive and active powers with the four single phase inverters, so, the control effort has been focused on the power flow control and has been realized through the hysteresis current control of the single phase inverters. And transport-delayed PLL with additional delay-time compensating term has been used to synchronize a grid voltage and the simulation results have shown that the compensating term could improve PLL performance under some frequency variation of the voltage.

• 기술사
• /
• 제30권1호
• /
• pp.125-136
• /
• 1997

위성을 이용한 무선 멀티미디어 서비스의 한 방안으로 위성 TDMA 방법에서 광대역 ISDN(BISDN)서비스를 적용하는 방안이 검토되고 있다 BISDN에서는 비동기 전송 모드인 ATM 방법에 의한 망 구성으로 다양한 멀티미디어 서비스가 가능하다. 본 논문에서는 지상 ATM망과 위성 TDMA 회선을 접속하기 위하여 위성을 이용한 ATM 접속과 서비스에 대한 새로 요구되는 기능으로 (1) 전송 품질 제어의 셀 지연 변이 보상 방법 (2)회선 효을의 향상 방법 (3) ATM 트래픽의 린PC 상태 (4) ATM 접속과 하드웨어 구성에 대한 기술적 사항을 분석하고, 위성 TDMA방법에서의 효율적인 BISDN서비스 수용을 검토하였다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 1999년도 춘계종합학술대회
• /
• pp.295-300
• /
• 1999

무선 ATM망에서 현재와 같은 멀티미디어 이동통신 서비스 제공을 위한 단말의 이동성 관리기법들이 많이 연구되고 있다. 본 논문에서는 이들 이동성 관리기법중 위치등록, 갱신, 그리고 핸드오프 제어기법에 대해 특성을 비교한다. 또한, 점차 소규모화되는 현재의 셀룰라 환경에서와 같이 빈번한 핸드오프 발생환경에 대하여 핸드오프 지연 및 통신단절시간과 속도변화에 따른 호 차단율 및 호 절단율을 비교하였다.

• Journal of Communications and Networks
• /
• 제12권4호
• /
• pp.346-357
• /
• 2010

Opportunistic scheduling provides the capability of resource management in wireless networks by taking advantage of multiuser diversity and by allowing delay variation in delivering data packets. It generally aims to maximize system throughput or guarantee fairness and quality of service (QoS) requirements. In this paper, we develop an extended proportional fair (PF) scheduling policy that can statistically guarantee three kinds of QoS. The scheduling policy is derived by solving the optimization problems in an ideal system according to QoS constraints. We prove that the practical version of the scheduling policy is optimal in opportunistic scheduling systems. As each scheduling policy has some parameters, we also consider practical parameter adaptation algorithms that require low implementation complexity and show their convergences mathematically. Through simulations, we confirm that our proposed schedulers show good fairness performance in addition to guaranteeing each user's QoS requirements.

• ETRI Journal
• /
• 제35권6호
• /
• pp.1075-1083
• /
• 2013

This paper describes an ultra-wideband (UWB) antenna that uses a ring resonator concept. The proposed antenna can operate in the entire UWB, and the IEEE 802.11a frequency band can be rejected by inserting a notch stub into the ring resonator. The experiment results indicate that the measured impedance bandwidth of the proposed antenna is 17.5 GHz (2.5 GHz to at least 20 GHz). The proposed UWB antenna has omnidirectional radiation patterns with a gain variation of 3 dBi (1 dBi to 4 dBi).

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.412-415
• /
• 2008

It is known that the address discharge delay time during an address period strongly depends on the wall charge leakage. It was observed that the wall charge leakage during an address period is related to both the address width and the ambient temperature. Accordingly, the effects of address electrode width on the address discharge and wall voltage variation during an address period were examined under variable temperatures.

• 한국정보통신학회논문지
• /
• 제4권2호
• /
• pp.323-336
• /
• 2000

단기간에 B-ISDN 서비스를 제공하기 위하여 광대역 종합 통신망은 지상 ATM과 넓은 서비스 지역을 커버할 수 있는 위성망의 결합을 요구하고 있다. 본 논문에서는 위성 B-ISDN을 실현하려 할 때 위성 TDMA와 지상 ATM 망의 접속시에 발생하는 셀 지연 변이를 보상하는 기존 방식들을 분석하고 그중 타임 스탬프 방식과 셀 간격정보 방식의 단점을 보완하는 부분 타임 스탬프 방식을 제시한다. 제안한 방법을 분석하고 시뮬레이션을 통하여 성능을 평가하여 제안 방식이 기존의 방식보다 우수하며 많은 장점을 가지고 있음을 보인다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
• /
• pp.103-105
• /
• 1993

This paper proposed a new direct vector control scheme using high frequency current injection. This scheme has some attractive features such as using no flux sensor or speed sensor, robustness of parameter variation, capability of accurate vector control at very low speed. Compared to other direct vector control scheme, this scheme doesn't depends on phase delay and difference of magnitude of estimated flux, rotor resistance and all inductances except stator resistance. These features are proved by computer simulation and experimental results.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.1025-1030
• /
• 2009

It is known that the classical tuning formula for typical PID controllers in general provides unsatisfactory results for industrial plants where the time delay exceeds the dominant lag time. For this reason, alternative strategies have been studied in order to cope with this problem and the most popular scheme is the Smith Predictor(SP). In this paper, the dynamic model of a unit apartment in the district heating system, which is the control process effected by the dead-time, is developed, and the on/off room temperature control method with the SP simulate using Matlab-Simulink. The simulation results show that the SP works effectively in outdoor temperature variation.