• 한국경영과학회지
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• 제21권1호
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• pp.31-50
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• 1996

In this paper we prescribe a replication server scheme with an algorithm DRF (Differential Refresh File) to refresh multiple materialized views and replicas in distributed environments. Before sending relevant tuples in server sites to client sites, an effective tuple reduction scheme is developed as a preprocessor to reduce the transmission cost. Because it utilizes differential files with out touching base relations, the DRF scheme can help to minimize the number of locks, which enhances the system's performance.

• 한국통신학회논문지
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• 제35권7A호
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• pp.731-742
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• 2010

We propose an incremental relaying protocol in conjunction with opportunistic communication for differential modulation with an aim to make efficient use of the degrees of freedom of the channels by exploiting a imited feedback signal from the destination. In particular, whenever the direct link from the source to the destination is not favorable to decoding, the destination will request the help from the opportunistic relay (if any). The performance of the proposed system is derived in terms of average bit error probability and achievable spectral efficiency. The analytic results show that the system assisted by the opportunistic relaying can achieve full diversity at low SNR regime and exhibits a 30㏈ gain relative to direct transmission, assuming single-antenna terminals. We also determine the effect of power allocation on the bit error probability BEP) performance of our relaying scheme. We conclude with a discussion on the relationship between the given thresholds and channel resource savings. Monte-Carlo simulations are performed to verify the analysis.

• 한국전자파학회논문지
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• 제14권8호
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• pp.891-897
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• 2003

본 논문에서는 원형의 직교편광기를 새로이 제작하여 무선광 차동검출기를 구성하고 잡음광 소거에 활용하였다. 직교편광기는 2개의 반원형 편광기의 통과축이 서로 수직이 되도록 접합하여 1개의 원형을 이루며, 이를 모터로 구동하여 신호광의 편파와 매칭을 시킴으로써 잡음광의 간섭을 소거하였다. 적외선 광필터가 부착된 단일의 포토트랜지스터를 사용할 때에 비하여 직교편광기를 사용한 차동검출기에서 잡음의 세기가 약 20 dB 감소하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.329-331
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• 2003

PROSET2000 that is integrated protective management system had developed and used in order to automate the setting process of protective relays in transmission system protection. PROSET2000 have database for relay setting and automated for relay setting program within. This paper proposed PCM current differential relay setting program point of Object Oriented Programming paradigm using Unified Modeling Language about additional relay in PROSET2000. Nevertheless each relay uses same current differential but setting method is different. This paper discribed different thing about setting method of each relay and evaluated more effective and corrective relay setting program using UML.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.42-44
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• 1994

This paper presents the method of estimating integral coefficients of new distance relaying algorithm for transmission line protection. The proposed method is based on the differential equation calculates impedance value by approximation of integral term of integro-differential equation which relate voltage with current. As a result, we can determine the integral coefficients in least square error sense in frequency domain and we take into consideration the analog filter characteristics and frequency domain characteristics of the system to be protected. The simulation results showed that these coefficients can be successfully used to obtain impedance value in distance relay.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.770-781
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• 2006

This paper defined design constraints for the compound CVTs (continuously variable trans-missions) by combining power-circulation-mode CVTs and power-split-mode CVTs, which were proposed for connecting 2K-H I-type differential gear to V-belt-type CVU (Continuously Variable Unit). The design constraints are the necessary and sufficient conditions to avoid geometrical interferences among elements in the compound CVTs, and to guarantee smooth assembly between the power-circulation-mode CVT and power-split-mode CVT Two com-pound CVTs were designed and manufactured in accordance with the design constraints. With these compound CVTs, theoretical analysis and performance experiments were conducted. The results showed that the design constraints were valid and effective design method, and that the designed compound CVTs had the improved performance.

• Current Optics and Photonics
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• 제7권5호
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• pp.537-544
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• 2023

Differential phase contrast (DPC) microscopy, a central quantitative phase imaging (QPI) technique in cell biology, facilitates label-free, real-time monitoring of intrinsic optical phase variations in biological samples. The existing DPC imaging theory, while important for QPI, is grounded in paraxial diffraction theory. However, this theory lacks accuracy when applied to high numerical aperture (NA) systems that are vital for high-resolution cellular studies. To tackle this limitation, we have, for the first time, formulated a nonparaxial DPC imaging equation with a transmission cross-coefficient (TCC) for high NA DPC microscopy. Our theoretical framework incorporates the apodization of the high NA objective lens, nonparaxial light propagation, and the angular distribution of source intensity or detector sensitivity. Thus, our TCC model deviates significantly from traditional paraxial TCCs, influenced by both NA and the angular variation of illumination or detection. Our nonparaxial imaging theory could enhance phase retrieval accuracy in QPI based on high NA DPC imaging.

• 대한전자공학회논문지SD
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• 제41권4호
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• pp.29-40
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• 2004

본 논문에서는 유한 차분 시간 영역(FDTD, Finite Differential Time Domain)법과 완전 정합층(PML, Perfectly Matched Layer) 방법을 이용하여 반도체 다층 배선이 평행하게 인접하거나, 교차하면서 인접하는 구조뿐 아니라. 평행하게 인접하면서 다른 평면상에 두 배선이 존재하는 3차원 다층 배선 구조에 대한 컴퓨터 수치 분석 방법을 보고한다. 평행한 인접 배선 구조에서는 수평 거리를 변화시키면서 출력 결과를 비교하였으며, 교차한 인접 배선 구조에서는 수직 거리를 변수로 하여 시간 영역과 주파수 영역에서의 출력 결과를 정량적으로 비교하였다. 또한, 평행하게 인접하면서 다른 평면상에 두 배선이 존재하는 3차원 다층 배선 구조에 대해서는 수평 거리와 수직 거리를 각각 변화시켜 가면서 출력되는 누화 특성을 측정하고 비교하였다.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.13-22
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• 1997

Power flow characteristics of a hydro-mechanical transmission system(HMT) are investigated for tracked vehicle in steering. A HMT consisting of two hydrostatic pump motors(HST), several planetary gear trains and steer differential gear is considered. In order to obtain the direction and magnitude of the power flow of the HMT, network theory for the general power transmission is used. Network model for the HMT in steering is developed, which consists of shafts, nodes and transmission elements such as clutch, gear, etc. Power flow analysis procedure consists of two stages : (1) traction force analysis in steering, (2) power flow analysis in HMT. Torque and speed of every transmission element of the HMT is determined from the network analysis. Also, efficiency, mechanical and hydraulic power loss including HST, are obtained. In addition, the regenerative power flow resulting from steering can be studied in graphic display. The power flow analysis program(PCSTEER) developed in this work can be used as a useful design tool for the tracked vehicle with HMT.

• 대한전자공학회논문지TC
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• 제46권3호
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• pp.26-31
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• 2009

60 GHz 대역에서 multi-gigabit 전송률을 달성하기 위하여 제안된 ECMA 표준은 프리앰블과 데이터 부분으로 구성된 버스트 (burst)를 통하여 데이터 송수신을 수행하며 프리앰블과 데이터 부분에서는 동작 모드에 따라 다양한 변조 방식이 사용된다. 따라서 다양한 변조 방식을 지원할 수 있는 수신 알고리듬의 설계가 필수적이다. 본 논문에서는 ECMA 표준 중 DBPSK (Differential Binary Phase Shift Keying)와 DQPSK (Differential Quadrature Phase Shift Keying) 그리고 OOK (On-Off Keying) 변조 방식을 지원하는 multi-gigabit packet 송수신 시스템을 위한 수신 알고리듬을 설계하였다. 설계된 수신 알고리듬은 동일한 구조 및 동작 방식을 통하여 고려한 모든 변조 방식들을 지원할 수 있을 뿐만 아니라 하드웨어 구현 복잡도가 낮은 장점을 지닌다.