• Journal of KIISE:Computer Systems and Theory
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• v.26 no.2
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• pp.136-144
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• 1999

정규 순환 방정식형태로 표현된 문제로부터 시스톨릭 어레이를 유도하기 위하여 일반적으로 공간-시간 사상 기법이 널리 이용되고 있다. 이 기법에서 공간 행렬은 주어진 문제 공간을 시스톨릭 어레이로 사상시키는 역할을 한다. 이러한 공간 행렬에 의해 유도되는 시시톨릭 어레이가 유효한 것이 되기 위해서 몇 가지의 제약 조건을 필요로 한다. 본 논문에서는 지역 의존 제약 조건을 기초로 하여 3차원의 문제 공간으로부터 2차원의 시스톨릭 어레이를 유도하는 공간 행렬의 계산 방법을 제시하고자한다. 먼저, 지역 의존 조건을 만족시키기위해 공간 행렬의 요소들이 가져야 하는 조건을 찾고 이 조건으로부터 가능한 트사 벡터들을 선정한다. 다음으로, 필요조건으로서 이러한 투사 벡터들로부터 지역 의존 조건을 만족시키는 공간 행렬을 가지는 투사 벡터들을 선별함으로써, 유효한 시스톨릭 어레이를 유도할 수 있는 모든 가능한 공간 행렬들을 구한다. 이렇게 구해진 가능한 모든 공간 행렬은 시스톨릭 어레이를 위한 캐드도구 또는 시뮬레이터에서 유용하게 이용될 수 있다.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.4
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• pp.367-373
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• 2011

Guided waves inspection techniques that are different with inspection technique by bulk waves are widely used in pipe line evaluation due to advantages of long distance inspection. However, most of pipe lines at industrial fields are buried and/or coated. In this case, due to the attenuation effect from soil and/or coating material, there are a lot of difficulty on inspection by conventional ultrasonic technique. In this paper, guided waves propagating patterns are calculated with respect to excitation mode by Normal Mode Expansion(NME). Guided waves patterns based on excited by single transducer and guided wave focusing technique have employed to analyze focusing pattern on a pipe. A longitudinal mode and high order flexural modes are used with various number of transducers to determine sensitivity. Guided waves energy excited by multi transducer with focusing algorithm was successfully focused at a desired point.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.506-514
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• 2012

This paper represents a method for designing of path following Line-of-Sight(LOS) guidance law based on vehicle kinematics. In general, a LOS guidance law which is composed of gains and approach length as design parameters is designed by empirical or trial-and-error method. These approaches cannot guarantee a precision tracking performance of guidance law consistently. Also, the design parameters should be redesigned with variations of vehicle maneuverability and flight velocity. Based on a vehicle kinematics with its velocity, the proposed method for designing of parameters not only minimizes the number of design parameters, also has a reliable and consistent tracking performance using variable guidance gain changed in accordance with flight velocity. This is validated by nonlinear simulation with $1^{st}$ order attitude response dynamics and flight experiments with given linear and circular path.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.627-636
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• 2021

This paper deals with a study for the guidance control of reusable launch vehicle. For this purpose, modeling of the equation of motion of a reusable launch vehicle with 6 degrees of freedom was performed. With this model, an optimal re-entry path was created and a path-following guidance control simulation was performed to follow the optimal re-entry path. For the design of the path-following guidance controller, the attitude controller applying a time-delay technique that is resistant to modeling uncertainty, disturbance and failure. And the nonlinear path-following guidance law were used. Guidance control simulation using a classical PD controller was performed and compared with the guidance control simulation of a reusable launch vehicle applying a time delay technique.

• Fire Science and Engineering
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• v.21 no.4
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• pp.115-122
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• 2007

Exiting systems are essential to prevent casualties in case of fire. However, existing guidance systems are lack of flexibility because their functionalities are fixed when they are planned. In this paper, a system is introduced which guides evacuees in realtime by processing data it gathers throughout various sensors in realtime. It is planned and designed to aid quick and efficient evacuation, and produced, installed and tested in an underground space to show its feasibility. In building the system, ubiquitous techniques are employed for its sensor network and evacuee positioning in an attempt to make it cheap and extendable.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.981-988
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• 2021

This paper presents a decentralized guidance algorithm for swarm flight of fixed-wing UAVs (Unmanned Aerial Vehicles). Considering swarm flight missions, we assume four representative swarm tasks: gathering, loitering, waypoint/path following, and individual task. Those tasks require several distinct maneuvers such as path following, flocking, and collision avoidance. In order to deal with the required maneuvers, this paper proposes an integrated guidance algorithm based on vector field, augmented Cucker-Smale model, and potential field methods. Integrated guidance command is synthesized with heuristic weights designed for each guidance method. The proposed algorithm is verified through flight tests using up to 19 small fixed-wing UAVs.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.12
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• pp.692-703
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• 2004

Communication induced checkpointing (CIC) is one of the checkpointing techniques to provide fault tolerance for distributed systems. Independent checkpoints that each distributed process produces without coordination are likely to be useless. Useless checkpoints, which cannot belong to any consistent global checkpoint sets, induce nondeterminant rollback. To prevent the useless checkpoints, CIC forces processes to take additional checkpoints at proper moment. The number of those forced checkpoints is the main source of failure-free overhead in CIC. In this paper, we present two new CIC protocols which satisfy 'No Z-Cycle (NZC)'property. The proposed protocols reduce the number of forced checkpoints compared to the existing protocols with the drawback of the increase in message delay. Our simulation results with the synthetic data show that the proposed protocols have lower failure-free overhead than the existing protocols. Additionally, we show that the classical 'index-based checkpointing' protocols are inefficient in constructing the consistent global cut in distributed executions.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.1
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• pp.119-123
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• 2006

In this paper, we propose fault diagnosis of induction motor based on PCA and MLP. To resolve the main drawback of MLP, we calculate the reduced features by PCA in advance. Finally, we develop the diagnosis system based on nonlinear classifier by MLP rather than linear classifier by conventional k-NN. By various experiments, we obtained better classification performance in comparison to the results produced by linear classifier by k-NN.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.3
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• pp.189-196
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• 2011

In this paper, we analyze the error performance of SIC-based signal detection methods in MIMO systems. Considered detection methods are SIC signal detection and LR-SIC signal detection. We derive BLER performance of the methods and the performance is confirmed by computer simulations.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.88-90
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• 2008

본 논문은 이중여자 유도형(DFIG) 풍력발전 시스템에서 유효전력과 무효전력을 직접적으로 제어하기 위해 가변구조제어의 일종인 스위칭 이득기반의 선형궤환(LFSG)제어기법을 제시한다. 개조된 직접전력제어기법 (DPC)과 공간벡터변조방식(SVM)은 제안하는 제어기법을 실현하기 위해 이용된다. 개조된 직접전력제어원리를 이용해서 설계된 LFSG제어기법은 널리 사용되고 있는 자속기준제어기법(FOC)에 비해서 간단한 제어구조로 강인성과 빠른 응답특성을 보인다. 시뮬레이션결과는 제안하는 제어전략의 타당성과 강인성을 확인해준다.