• Title/Summary/Keyword: Backward Mode

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Initial Investigation on Consolidation with Adaptive Dynamic Threshold for ABR Multicast Connections in ATM Networks (비동기 전송모드 망의 점대다중점연결을 위한 적응동적임계치기반 병합알고리즘)

  • Shin, Soung-Wook;Cho, Kwang-Hyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.7 no.11
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    • pp.962-966
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    • 2001
  • The major problem at a branch point for point-to-multipoint available bit rate(ABR) services in asynchronous transfer mode (ATM) networks is how to consolidate backward resource management(BRM) cells from each branch for a multicast connection. In this paper, we propose an efficient feedback consolidation algorithm based on an adaptive dynamic threshold(ADT) to eliminate the consolidation noise and the reduce the consolidation delay. The main idea of the ADT algorithm lies in that each branch point estimates the ABR traffic condition of the network through the virtual queue estimation and the transmission threshold of the queue level in branch points is adaptively controlled according to the estimation. Simulation results show that the proposed ADT algorithm can achieve a faster response in congestion status and a higher link utilization compared with the previous works.

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Improvement of Element Stability using Adaptive Directional Reduced Integration and its Application to Rigid-Plastic Finite Element Method (적응성 선향저감적분법에 의한 요소의 안정성 향상과 강소성 유한요소해석에의 적용)

  • Park, K.;Lee, Y.K.;Yang, D.Y.
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.3
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    • pp.32-41
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    • 1995
  • In the analysis of metal forming processes by the finite element method, there are many numerical instabilities such as element locking, hourglass mode and shear locking. These instabilities may have a bad effect upon accuracy and convergence. The present work is concerned with improvement of stability and efficiency in two-dimensional rigid-plastic finite element method using various type of elemenmts and numerical intergration schemes. As metal forming examples, upsetting and backward extrusion are taken for comparison among the methods: various element types and numerical integration schemes. Comparison is made in terms of stability and efficiency in element behavior and computational efficiency and a new scheme of adaptive directional reduced integration is introduced. As a result, the finite element computation has been stabilized from the viewpoint of computational time, convergency, and numerical instability.

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Hybrid RANS/LES simulation of Base-Bleed in Supersonic Flows (초음속 유동장에서 기저 분출 유동의 대와류 난류 모사)

  • Shin, Jae-Ryul;Won, Su-Hee;Choi, Jeong-Yeol
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.332-335
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    • 2008
  • The purpose of this study is analysis of flow field where is around of injector of supersonic combustor which is bluff-body stabilized flame and hyper-mixer type of supersonic combustor injector by using hydrogen or hydrocarbon fuel. Various schemes are evaluated to supersonic backward step flow filed with massive separation region in validation step. Compounded scheme of 5th-order TVD-MUSCL, Roe FDS, S-A DES/DDES has a good performance in base and base-bleed flow.

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Next Generation Terrestrial DTV Transmission Technology (차세대 지상파 DTV 전송기술)

  • Kim, Sung-Hoon;Choi, Jin-Soo;Hong, Jin-Woo
    • Proceedings of the IEEK Conference
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    • 2008.06a
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    • pp.9-11
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    • 2008
  • In this paper, we describe a 1/4 rate robust modulation algorithm for Enhanced-xVSB system which is fully backward compatible with ATSC 8-VSB standard. Laboratory test results of proposed Enhanced-xVSB 1/4 rate mode is shown a significantly improved reception performance under multipath as well as AWGN channel. We suggest an Enhanced-xVSB terrestrial broadcasting system for in-band Pedestrian/Portable TV broadcasting service.

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Design of a Novel Lumped Element Backward Directional Coupler Based on Parallel Coupled-Line Theory (평행 결합선로 이론에 근거한 새로운 집중 소자형 방향성 결합기 해석 및 설계)

  • 송택영;이상현;김영태;천창율;박준석
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2002.11a
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    • pp.157-160
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    • 2002
  • In this paper, a novel lumped equivalent circuit for a conventional parallel directional coupler is proposed. The equivalent circuit and design formula for the presented lumped element coupler is derived based on the even-and odd-mode properties of a parallel-coupled line. By using the derived design formula, we have designed the 3㏈ and 10㏈ lumped element directional couplers at the center frequency of 100Mhz. Furthermore, a chip type directional coupler has been designed to fabricate with multilayer configurations by employing the Low Temperature CofiredCeramic (LTCC) process. Designed chip-type directional coupler has a 10㏈-coupling value at the center frequency of 2㎓. Excellent agreements between simulations and measurements on the designed directional couplers show the validity of this paper

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The Sound Field Reconstruction of a Korean Bell Using an Error Minimization Scheme in the BEM-Based Acoustical Holography (경계요소법에 기초한 음향 홀로그래피에서 오차 최소화 과정에 의한 한국 종의 음장 재구성)

  • 김철희;이장무;강연준
    • Journal of KSNVE
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    • v.9 no.1
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    • pp.131-140
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    • 1999
  • A method to reconstruct the sound field around a Korean bell is developed. The sound radiation problem is formulated based on the boundary element method by using the algorithm of the acoustical holography. Sound pressures at the hologram surface are measured and used as input data for the analysis program that was developed in this study. An error minimization scheme is presented to overcome difficulties that arise in the backward reconstruction of the BEM-based acoustical holography In the model fictitious source surfaces were also introduced to reduce the complexity stemmed from the source shape. The sound field associated with the (4.0) vibrational mode of the Korean bell was visualized and verified experimentally.

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Analysis of Receiving Performance in DVB-S2 BC Mode (DVB-S2 BC 모드의 수신성능 분석)

  • Do Gunchang;Sohn Won;Kim Taehoon;Kim Naesu
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2004.11a
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    • pp.169-174
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    • 2004
  • 이 논문에 서 는 DVB-S2 BC(Backward Compatibility) 모드에서 복조방식 에 따른 수신성 능을 분석하였다. 송신기는 DVB-S(HP)와 DVB-S2(LP) 스트림을 계층적 비대칭 8-PSK로 변조시킨 신호를 전송하며, 수신기는 계층적 변조 신호를 복조하기 위하여 LSB 에서 MSB순으로 복조하는 방식과 사분면 추정지수와 LLR 계산기를 이용한 계층적 복조방식을 적용할 수 있다. 이 논문은 두 복조방식에 대한 성능분석을 AWGN 및 비선형 채널에서 통계적 분석과 모의실험을 통하여 수행하였다.

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Development of VVVF Inverter Control System for Propulsion System (차량용 VVVF 인버터 제어시스템 개발)

  • Kim, B.S.;Lee, K.C.;Lee, H.S.;Kim, S.W.;Park, Y.C.;Kim, J.H.
    • Proceedings of the KIEE Conference
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    • 1994.07a
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    • pp.249-251
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    • 1994
  • This paper introduces an implementation of high performance voltage source inverter system based on 16bit micro-processor and DSP for the application to modem rolling stock traction system. In contrast with other industry oriented inverter system, this system requires precise control action complying with various load condition and high overload capability. An asynchronous PWM generation and 3' pulse mode technology are adopted in order to improve compliant starting torque characteristics at starting phase and soft backward-forward starting motion.

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Back-up Control of Truck-Trailer Vehicles with Practical Constraints: Computing Time Delay and Quantization

  • Kim, Youngouk;Park, Jinho;Paik, Joonki
    • IEIE Transactions on Smart Processing and Computing
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    • v.4 no.6
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    • pp.391-402
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    • 2015
  • In this paper, we present implementation of backward movement control of truck-trailer vehicles using a fuzzy mode-based control scheme considering practical constraints and computational overhead. We propose a fuzzy feedback controller where output is predicted with the delay of a unit sampling period. Analysis and design of the proposed controller is very easy, because it is synchronized with sampling time. Stability analysis is also possible when quantization exists in the implementation of fuzzy control architectures, and we show that if the trivial solution of the fuzzy control system without quantization is asymptotically stable, then the solutions of the fuzzy control system with quantization are uniformly ultimately bounded. Experimental results using a toy truck show that the proposed control system outperforms a conventional system.

Turbulence Enhancement Characteristics Analysis of Inclined-Tumbles for Various SCV Configurations (SCV형상별 경사텀블유동의 난류증가 특성 해석)

  • Lee, J.W.;Kang, K.Y.;Choi, S.H.;Park, S.C
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.234-242
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    • 1998
  • It has been demonstrated that the in-cylinder turbulence is enhanced by inclined swirl with a SCV(swirl control valve). The inclined-tumble flow measurement and analysis were performed for various types of intake systems that generated several different combinations of swirl ratio and tumble ratio in the cylinder. Experiments were conducted in a 4-valve optically accessed transparent research engine using a backward-scatter LDV mode under motoring condition at 1,000rpm. The influence of swirl/tumble levels on the characteristics of turbulence was analysed. This study presents experimental results of the inclined-tumble flow structure, including the flow motion phenomena, angular momentum and turbulence intensity.

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