• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.523-535
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• 2011

The precipitable water vapor (PW) was estimated using Global Navigation Satellite System (GNSS) from several GNSS stations within the Korean Peninsula. Nearby radiosonde sites covering the GNSS stations were used for the comparison and validation of test results. GNSS data recorded under typical and severe weather conditions were used to generalize our approach. Based on the analysis, we have confirmed that the derived PW values from the GNSS observables were well agreed on the estimates from the radiosonde observables within 10 mm level. Assuming that the GNSS observables could be a good weather monitoring tool, we further tested the performance of the current WAAS tropospheric delay model, UNB3, in the Korean Peninsula. Especially, the wet zenith delays estimated from the GNSS observables and from UNB3 delay model were compared. Test results showed that the modelled approach for the troposphere (i.e., UNB3) did not perform well especially under the wet weather conditions in the Korean Peninsula. It was suggested that a new model or a near real-time model (e.g., based on regional model from GNSS or numerical weather model) would be highly desirable for the Korean WA-DGNSS to minimize the effects of the tropospheric delay and hence to achieve high precision vertical navigation solutions.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.3
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• pp.337-342
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• 2009

This paper concerns delay-range-dependent robust stability and stabilization for time-delay nonliner system via T-S fuzzy model approach. The time delay is assumed to be a time-varying continuous function belonging to a given range. On the basis of a novel Lyapunov-Krasovskii functional, which includes the information of the range, delay-range-dependent stability criteria are established in terms of linear matrix inequality. It is shown that the new criteria can provide less conservative results than some existing ones. Moreover, the stability criteria are also used to design the stabilizing state-feedback controllers. Numerical examples are given to demonstrate the applicability of the proposed approach.

• The Journal of the Acoustical Society of Korea
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• v.14 no.3
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• pp.28-36
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• 1995

In this paper, a double loop control model using leaky delay LMS algorithm are proposed for active noise control. The proposed double loop control model estimates the loudspeaker characteristic and the error path transfer function with on-line using only gain and acoustic time delay to reduce computation burden. The control of error signal through double loop control scheme makes the more robust cntrol system. The input signal of filter to estimate acoustic time delay is used difference between input signal of input microphone and adaptive filter output. And also, in nonstationary environments, the leaky delay LMS algorithm is employed to counteract parameter drift of delay LMS algorithm. For practical noise signal, the proposed double loop control model reduces noise level about 12.9 dB.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.959-964
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• 2018

In this paper, it was firstly confirmed that the drain current of the depleted SOI MOSFET operated in the high frequency response delay occurs by the inductive parasitic. Depleted SOI MOSFET cannot be applied as a conventional high-frequency MOSFET model because the response delay of the drain current is generated in accordance with the drain voltage fluctuation. This response delay may be described as a non-quasi-static effect, and the SOI MOSFET generated the response delay by the inductive parasitics compared to typical MOSFET. It is confirmed that depleted SOI MOSFET's RF characteristics can be well reproduced with the proposed method including the drain current response delay.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.6
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• pp.762-767
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• 2008

This paper introduces a $L_{\infty}$-gain state feedback fuzzy controller design for the time delay nonlinear system represented by Takagi-Sugeno(T-S) fuzzy model. First, the T-S fuzzy model is employed to represent the time delay nonlinear system. Next based on the fuzzy model, a fuzzy state feedback controller is developed to achieve $L_{\infty}$-gain performance. Finally, sufficient conditions are derived for $L_{\infty}$-gain performance. The sufficient conditions are formulated in the format of linear matrix inequalities (LMIs). The effectiveness of the proposed controller design methonology is finally demonstrated through numerical simulations.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.163-165
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• 2005

최근 GPS의 이상 현상에 대한 대비 핀 독자 항법 시스템을 구축하기 위해 유럽의 갈릴레오 일본의 QZSS 등 세계 선진각국의 GPS에 독립적인 위성항법시스템을 구축하고 있으며 GPS의 백업 용도로 지상항법 시스템인 Loran의 현대화 작업 등이 진행되고 있다. 국내에서도 독자항법에 대한 필요성이 거론되었고 해양수산부는 해상 밀 국내 전 지역을 커버할 수 있는 신호 영역을 가진 DGPS 신호의 대체항법 및 시각동기 인프라로서의 활용성에 대해 정책적으로 접근하고 있다. GPS 보정 정보를 방송하는 DGPS 비콘 신호는 중파 대역으로 지표를 따라 전파되는 특성이 있다. 지표를 따라 전파되는 지표파는 지형의 전도율과 고도에 의해 전파의 전파시 추가 지연이 발생하고 이 추가 지연은 항법 린 시각동기에 오차를 유발하게 된다. 본 논문은 DGPS 신호가 지형의 특성에 따라 지연되는 전파 특성 및 전파지연모델을 소개하고 해당 전파지연모델 구현 결과를 기존 연구결과와 비교$\cdot$검증하여 그 결과를 제시한다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8S
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• pp.2620-2630
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• 2000

본 논문에서는 규칙 기반 추론 기법을 이용하여 LAN 상의 지연 장애 검출 알고리즘과 장애를 유발시킨 호스트에 대한 위치 확인 알고리즘 및 장애 원인 분석 알고리즘을 제시하고자 한다. 이를 위해 지연 장애 검출 모델과 RBR 기반 장애 검출 규칙 모델을 제시하고 있다. 또한 충돌율 검출 규칙과 이용률 검출 규칙을 적용하여 지연 장애 검출 알고리즘을 설계하였고, 최대 패킷 출력 호스트 파악 규칙을 적용하여 장애 위치 탐색 알고리즘을 설계하였다. 그리고 패킷 유형 분석 규칙과 장애 원인 파악 규칙을 적용하여 장애 원인 분석 알고리즘을 설계하였다. 이를 통하여 LAN 상의 지연 장애를 검출하고 진단하는 기법을 제시하고자 한다. 이와 같이 제시한 지연 장애 검출 및 진단 기법을 실제 네트워크 환경에 직접 적용시켜 봄으로써 본 논문에서 제시한 장애 검출 및 진단 기법의 정확성과 적용성을 확인하였다. 이러한 기법은 네트워크 관리자가 LAN 상의 장애를 진단하고 원인을 해결하는데 큰 도움을 줄 것으로 기대된다.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.419-428
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• 2008

IEEE 802.15.4 reserves transmission time to support real-time transport by sending GTS request packets to the PAN coordinator in advance. This paper introduces GTS-FAT technique to reduce the reservation time by giving a higher sending priority to GTS request packets than data packets. Differently from the conventional scheme where these two kinds of packets share a single transmission queue, GTS-FAT scheme allocates two queues with two different contention window sizes like IEEE 802.11e. This paper also proposes an analytical GTS delay model by combining the two legacy models for 802.15.4 and 802.11e to accurately predict the GTS-FAT delay over a given network topology. Our analysis shows that GTS-FAT reduces GTS service delay by up to 50% at the expense of the data delay by only up to 6.1% when GTS request packets four times outnumber data packets.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.9
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• pp.78-85
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• 2000

A new analytical VLSI interconnect delay model is presented and its accuracy is experimentally verified. In the model, the transmission line parameter variations due to skin effect, proximity effect, and silicon substrate effect are taken into account. That is, the circuit model of the interconnect line that includes these effects is newly developed and analyzed. For the model verification, test patterns combined the coplanar structure with microstrip were designed by using 0.35${\mu}m$ CMOS process technology. It is shown that the accuracy of the model is less than about 10% error.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.68-74
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• 1998

This paper deals with a model reduction problem for the linear systems with state delay. After defining the controllability/observability Gramians, the concept of a balanced model for the linear systems with state delay is introduced. Based on solutions of linear matrix inequalities, the model reduction method with guaranteed error bounds is developed. In order to demonstrate the efficacy of teh suggested method, a numerical example is also performed.