• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.132-135
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• 2000

In this paper, we propose to exploit a multi-code CDMA scheme for power line communication (PLC) systems, and its performance on non-Gaussian impulse and harmonic noises is presented. The proposed multi-code CDMA scheme utilizes convolutional coding and block interleaving to combat with the non-Gaussian noises, and simulation results indicate effective alleviation of these noises, and thus significant bit error rate improvement by the proposed scheme even under strict restriction of frequency band allowed in PLC systems.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.157-164
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• 2001

This paper performs static and dynamic tests of a multi-leaf spring and a tapered leaf spring to investigate their hysteretic characteristics. In the static test, trapezoidal input load is applied with 0.1Hz excitation frequency and with zero initial loading conditions. In the dynamic test, sinusoidal input load is applied with five excitation amplitudes and three excitation frequencies. In these tests, static and dynamic hysteretic characteristics of the multi-leaf spring and the tapered leaf spring are compared, and, the effects of excitation amplitudes and frequencies on dynamic spring rate are also shown. In this paper, actual vehicle tests are performed to study the effects of hysteretic characteristics of the large-sized truck's handling performance. The multi-leaf spring or the tapered leaf spring is used in the front suspension. The actual vehicle test is performed in a double lane change track with three velocities. Lateral acceleration, yaw rate and roll angle are measured using a gyro-meter located at the mass center of the cab. The test results showed that a large-sized truck with a tapered leaf spring needs to have an additional apparatus such as roll stabilizer bar to increase the roll stabilizer due to hysteretic characteristics.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.564-566
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• 2005

The relation between HPA (High Power Amplifier) and COMS (Communication Ocean Meteorological Satellite) multi-carrier is analyzed in this paper. MODAC (Meteorological and Ocean Data Application Center) has a primary mission to transmit processed data, HRIT (High Rate Information Transmission) and LRIT (Low Rate Information Transmission), which is normalized and calibrated by pre-processing. It is also replaced with the SOC (Satellite Operation Center) in emergency case and can transmit the command and ranging tones for operation of COMS. From the result of simulation with modelled HPA, it is found that the multi-carrier in one HPA can give rise to an inter-modulation which makes harmonic and spurious elements increase in-band. Under the environment of these increased parasitic elements, the degradation of multi-carrier's quality is estimated from the ratio of the amount of noise to total output power of HPA.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2118-2126
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• 2017

The large-scale power system blackouts have indicated that conventional protection relays that based on local signals cannot fit for modern power grids with complicated setting or heavily loaded-flow transfer. In order to accurately detect various faulted lines and improve the fault-tolerance of wide-area protection, a novel multi-section weighed fault matching and detecting algorithm is proposed. The real protection vector (RPV) and expected section protection vectors (ESPVs) for five fault sections are constructed respectively. The function of multi-section weighed fault matching is established to calculate the section fault matching degrees between RPV and five ESPVs. Then the fault degree of protected line based on five section fault degrees can be obtained. Two fault detecting criterions are given to support the higher accuracy rate of detecting fault. With the enumerating method, the simulation tests illustrate the correctness and fault-tolerance of proposed algorithm. It can reach the target of 100% accuracy rate under 5 bits error of wide-area protections. The influence factors of fault-tolerance are analyzed, which include the choosing of wide-area protections, as well as the topological structures of power grid and fault threshold.

• 대한전자공학회논문지SP
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• 제41권6호
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• pp.43-49
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• 2004

기존의 다중 클래스 SVMs은 클래스의 개수가 증가되면, 이진 클래스 SVMs의 수도 증가되어 분류를 위해 많은 시간이 요구된다. 본 논문에서는 분류 시간을 줄이기 위하여, PCA+LDA 특징 부 공간에서 NNR을 적용하여 클래스의 개수를 줄이는 방법을 제안한다. 제안된 방법은 PCA+LDA 특징 부 공간에서 간단한 NNR을 사용하여, 입력된 테스트 특징 데이터와 근접된 얼굴 클래스들을 추출함으로서 얼굴 클래스의 개수를 줄이는 방법이다. 클래스 개수를 줄임으로, 본 방법은 기존의 다중 클래스 SVMs에 비하여 훈련 횟수와 비교 횟수를 줄일 수 있고, 결과적으로 하나의 테스트 영상을 위한 분류 시간을 크게 줄일 수 있다. 또한 실험 결과, 제안된 방법은 NNC 기법보다 낮은 에러 율을 가지며, 기존의 다중 클래스 SVMs보다 동일한 에러 율을 갖지만, 보다 빠른 분류시간을 가짐을 확인할 수 있었다.

• 한국음향학회지
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• 제20권8호
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• pp.19-23
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• 2001

고속 저전력의 DSP (Programmable Digital Signal Processor)가 개발됨에 따라 이동통신 분야에서 시스템 및 단말기 등이 DSP를 사용하여 구현되고 있다. 본 논문에서는 DSP를 사용한 AMR (Adaptive Multi-rate) 음성부호화기의 멀티 채널 실시간 구현에 관하여 논한다. AMR 음성부호화 알고리즘을 250 MHz로 동작하는 32비트 정수형 DSP 칩인 TMS320C6202를 사용하여 구현하였다. 실시간 동작을 위하여 cross compile, 선형 어셈블리 최적화, TMS320C62xx 어셈블리 최적화 작업을 수행하였다. AMR 음성부호화기에 음성 데이터 입출력 기능 및 외부 CPU와의 통신기능을 포함하였다. DSP EVM 보드를 사용하여 AMR 음성부호화기를 개발하였고, ETRI에서 개발중인 비동기 IMT-2000 시스템 상에서 동작 및 기능을 검증하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.113-116
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• 2008

This work presents numerical optimization for design of staggered arrays of dimples printed on opposite surfaces of a cooling channel with a fast and elitist Non-Dominated Sorting of Genetic Algorithm (NSGA-II) of multi-objective optimization. As Pareto optimal front produces a set of optimal solutions, the trends of objective functions with design variables are predicted by hybrid multi-objective evolutionary algorithm. The problem is defined by three non-dimensional geometric design variables composed of dimpled channel height, dimple print diameter, dimple spacing and dimple depth to maximize heat transfer rate compromising with pressure drop. Twenty designs generated by Latin hypercube sampling were evaluated by Reynolds-averaged Navier-Stokes solver and the evaluated objectives were used to construct Pareto optimal front through hybrid multi-objective evolutionary algorithm. The optimum designs were grouped by k-mean clustering technique and some of the clustered points were evaluated by flow analysis. With increase in dimple depth, heat transfer rate increases and at the same time pressure drop also increases, while opposite behavior is obtained for the dimple spacing. The heat transfer performance is related to the vertical motion of the flow and the reattachment length in the dimple.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.284-287
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• 2001

Multi-pole anisotropic Sr-ferrite sintered magnets has been studied by powder injection molding under applied magnetic field. The orientation of anisotropic Sr-ferrite powders higher than 80% during injection molding is achieved at the following conditions; apparent viscosity lower then 2500 poise in 1000 $sec^{-1}$ shear rate and applied magnetic field higher then 4 kOe. For the high fluidity and strength of injection molded compact, and the effective binder removal without defects during solvent extraction and thermal debinding, the optimum multi-binder composition is paraffin wax(PW)/carnauba wax(CW)/HDPE = 50/25/25 wt%. The rate of binder removal is proportional to the mean particle size of Sr-ferrite powders whereas it is inversely proportional to the content of Sr-ferrite powders and the sample thickness. The high magnetic properties of Sr-ferrite sintered magnets are; 3.8 kG of remanent flux density, 3.4 kOe of intrinsic coercivity, and 1.2 kG of surface flux density (l-mm-thick) in the direction of applied magnetic field.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권3호
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• pp.271-275
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• 2008

근래의 지속적인 멀티미디어 기술의 발전과 컨덴츠를 이용하는 사용자의 향상된 욕구가 부합하여 새로운 실감 미디어 기술이 창출되고 있다. 그 중에서 다시점 비디오는 3차원 TV, 자유 시점 비디오 등의 기반 기술로써 활발하게 연구되고 있다. 하지만 시점 수의 증가에 따른 부호화 시간 증가, 비트율 증가 등이 문제점으로 작용한다. 본 논문에서는 다시점 비디오의 부호화 효율을 높이기 위해 향상된 GoGOP 구조를 제안한다. 즉, Key 프레임 위치 조절, 동적인 I 프레임 수 그리고 동적인 B 프레임 수를 이용하는 방법을 적용하여 향상된 GoGOP 구조를 제안하였다. 실험 결과, 본 논문에서 제안한 기법이 Anchor 구조와 비교하여 유사한 PSNR 값을 가지면서, 비트율이 상당히 감소하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권5호
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• pp.691-708
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• 2010

An important issue of supporting multi-users with diverse quality-of-service (QoS) requirements over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resource while, at the same time, to meet each communication service QoS requirement. In this work, we study the problem of a variety of communication services over multi-media heterogeneous cognitive OFDM system. We first divide the communication services into two parts. Multimedia applications such as broadband voice transmission and real-time video streaming are very delay-sensitive (DS) and need guaranteed throughput. On the other side, services like file transmission and email service are relatively delay tolerant (DT) so varying-rate transmission is acceptable. Then, we formulate the scheduling as a convex optimization problem, and propose low complexity distributed solutions by jointly considering channel assignment, bit allocation, and power allocation. Unlike prior works that do not care computational complexity. Furthermore, we propose the FAASA (Fairness Assured Adaptive Sub-carrier Allocation) algorithm for both DS and DT users, which is a dynamic sub-carrier allocation algorithm in order to maximize throughput while taking into account fairness. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.