• 전기전자학회논문지
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• 제1권1호
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• pp.120-137
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• 1997

정지궤도 위성과 지구국간 광통신을 대기상태와 앙각의 함수로써 해석할 수 있는 한모델(Han's model)을 제시하였다. 한모델에서는 대기상태를 맑은날, 구름낀 날, 안개, 헤이즈, 비, 눈의 여섯가지 전형적인 상태로 구분한다. 비트오류을 $10^{-7}$을 만족하는 데이터 전송속도를 한모델을 이용하여 상향링크와 하향링크에 대해 해석하였다. 상향링크시의 포인팅손실이 하향링크시의 대기에 의한 공간 가간섭 저하보다 크기 때문에 데이터 전송속도는 하향링크 보다 오히려 상향링크시에 제한됨을 알 수 있었다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.755-758
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• 2016

본 논문에서는 바이너리 프로그램에서 함수가 호출될 시 바이너리 내에서 어떠한 방법으로 함수를 호출하는지 설명한다. 그리고 그 함수를 호출할시 필요한 요소들과 C언어 파일의 동적링크 컴파일 과정과 그 요소들을 이어주는 '링커'라는 개념을 설명하고, 정적링크와 동적링크를 차이점을 비교 분석한다. 또한 동적 링크를 활용하여 취약점을 공격하는 Return To Dynamic Linker에 대해 간략히 서술하며 테스트바이너리에 시험해본다.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2002년도 제41회 학술발표회논문집
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• pp.97-139
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• 2002

The aim of the present study is to find a good quality user equilibrium assignments under time varying condition. For this purpose, this study introduces a dynamic network loading method that can maintain correct flow propagation as well as flow conservation, and it develops a novel solution algorithm that does not need evaluation of the objective function by modifying the Schittenhelm (1990)'s algorithm. This novel algorithm turns out to be efficient and convenient compared to the conventional Frank-Wolfe (1956) algorithm because the former finds solutions based on routes rather than links so that it can maintain correct flow propagation intrinsically in the time-varying network conditions. The application of dynamic user equilibrium (DUE) assignment model with this novel solution algorithm to test networks including medium-sized one shows that the present DUE assignment model gives rise to high quality discrete time solutions when we adopt the deterministic queuing model for a link performance function, and we associate flows and costs in a proper way.

• 한국도로학회논문집
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• 제13권1호
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• pp.49-57
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• 2011

이 연구는 청주시의 가로구간 교통사고를 다루고 있다. 연구의 목적은 가로구간의 기능별 사고모형을 개발하는 데 있다. 이를 위해서 이 연구는 전체 472개의 세부구간으로 분리된 주간선도로와 보조간선도로의 사고 자료를 이용하여 적합한 모형을 개발하는데 중점을 두고 있다. 연구의 주요 결과는 다음과 같다. 첫째, 주간선과 보조간선도로의 사고특성에 대한 t 검정은 두 도로의 사고건수와 EPDO에 차이가 있는 것으로 나타나 기능별 사고모형 개발이 적절한 것으로 분석된다. 둘째, 주간선도로의 EPDO와 사고건수는 모두 ZINB모형이 적합한 것으로 분석된다. 셋째, 보조간선도로 EPDO는 ZINB모형, 그리고 사고건수는 ZIP모형이 최적인 것으로 분석된다. 마지막으로 주간선도로 사고모형(ZINB)의 공통변수는 교통량과 굴곡점수, 보조간선도로의 EPDO모형(ZINB)과 사고건수모형(ZIP) 공통변수는 평균종단경사인 것으로 평가된다.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.799-809
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• 2002

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

• Communications for Statistical Applications and Methods
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• 제16권6호
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• pp.937-943
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• 2009

가변용량 네트워크에서의 각 링크는 서로 독립이며 용량한계가 설정되어 있다. 각 링크는 각동하거나 작동불능의 두 상태로 구별되며 작동불능 상태의 링크는 유량을 통과시킬 수 없다. 주어진 네트워크는 미리 설정된 기정용량이상의 최대 전송용량이 가능할 때 작동된다고 한다. 본 논문에서는 가변용량 네트워크에서 기정용량이 주어졌을 때의 각 링크의 용량에 관한 구조적 중요도와 신뢰성 중요도를 정의하고, 네트워크 성능지수에 관련한 링크 중요도 척도를 제시한다. 또한 다양한 구조의 네트워크에서의 수치예제를 통하여 제시된 척도를 비교분석한다.

• 한국정밀공학회지
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• 제13권11호
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• pp.132-142
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• 1996

This paper presents a technique to model and control a manipulator which has a flexible link and moves in a vertical plane. The flexible link is modeled as an Euler-Bernoulli Beam. Elastic deformation of the flexible link is represented using the assumed modes method. A comparison function which satisfies all geometric and natural boundary conditions of a cantilever beam with an end mass is used as an assumed mode shape. Lagrange's equation is utilized for the development of a discretized model. This paper presents a simple technique to improve the correctness of the developed model. The final model including the shortening effect due to elastic deformation correlates very well with experimental results. The free body motion simulation shows that two assumed modes for the representation of the elastic deformation is proper in terms of the model size and correctness. A control algorithm is developed using PID control technique. The proportional, integral and derivative control gains are determined based on dominant pole placement method with a rigid one-link manipulator. A position control simulation shows that the control algorithm can be used to control the position and residual oscillation of the flexible one-link manipulator effectively.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.469-472
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• 2008

In this paper, we discuss the recent trends on the passive UHF RFID tag chip design techniques and several important system parameters. We also summarize link budget studies on both conventional and modem UHF RFID communications. The paper highlights the reverse link limited case, which has known to be the minor concern if reader continuous wave (CW) can reach the tag in sufficient level. This makes sense when the tag sensitivity is rather high (over 10-12${\mu}W$); however, since the tag chip fabrication technologies have been developed by time, the tag chip threshold levels are now less-dominant in determining link margin. If the tag limitation can be alleviated, the forward link limited case can be resolved; thus, we rather focus on the path-loss problem. Since the path-losses are still exist in both forward and reverse links, and it can be doubled while CW travels the reader-tag-reader path because forward link and reverse link are on the same distance. Consider if reader receiver sensitivity is very high in the worst case. In this case, weaken tag response (i.e., backscatters) cannot reach the level that reader receiver can process tag data; bit-error rate can be higher. Overall, backscatter levels should be high enough so that reader receiver can correctly function. After discussing link budget, we carried out practical measurements on fading effects between two circularly polarized UHF RFID antennas in a small scale area.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1072-1077
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• 2004

This paper provides a new approach to analyze the stability of a general multi-link TCP Vegas, which is a kind of feedback-based congestion algorithm. Whereas the conventional approaches use the approximately linearized model of the TCP Vegas along equilibrium pints, this approach models a multi-link TCP Vegas network in the form of a piecewise linear multiple time-delay system. And then, based on the exactly characterized dynamic model, this paper presents a new stability criterion via a piecewise and multiple delay-dependent Lyapunov-Krasovskii function. Especially, the resulting stability criterion is formulated in terms of linear matrix inequalities (LMIs).

• 전력전자학회논문지
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• 제23권4호
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• pp.281-285
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• 2018

An isolated feedback method for measuring the inverter DC-link voltage is proposed. This method provides a simple and economical solution to inverter control systems that use a flyback converter as a controller power supply. In the proposed method, data on the DC-link voltage are acquired when the primary side voltage appears on the secondary side of the flyback transformer, thereby eliminating the need to adopt an extra signal isolation method. To solve the non-synchronization problem between the flyback converter switching and main controller sampling, the external interrupt function of the micro-controller is used as a trigger signal for the A/D conversion.