• 한국소음진동공학회논문집
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• 제14권4호
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• pp.267-275
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• 2004

This research is concerned with the development of a real-time adaptive PPF controller for the active vibration suppression of smart structure. In general, the tuning of the PPF controller is carried out off-line. In this research, the real-time learning algorithm is developed to find the optimal filter frequency of the PPF controller in real time and the efficacy of the algorithm is proved by implementing it in real time. To this end, the adaptive algorithm is developed by applying the gradient descent method to the predefined performance index, which is similar to the method used popularly in the optimization and neural network controller design. The experiment was carried out to verify the validity of the adaptive PPF controller developed in this research. The experimental results showed that adaptive PPF controller is effective for active vibration control of the structure which is excited by either impact or harmonic disturbance. The filter frequency of the PPF controller is tuned in a very short period of time thus proving the efficiency of the adaptive PPF controller.

• 전산구조공학
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• 제8권2호
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• pp.123-132
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• 1995

Genetic Algorithms(GA)는 생명체의 자연진화 법칙에 기초한 최적화 방법으로 그 범용성이 높이 평가되어지고 있다. 기존의 GA는 대부분 설계변수로 2진수형 코드를 사용하는데, 이는 실수형 설계변수로 구성된 최적화 문제를 해결하기 위해 컴퓨터 주 기억용량을 많이 사용하여야 하며, 계산 시간 면에서도 비효율적이고 또한 국부탐색 능력도 떨어지는 단점이 있다. 따라서 본 연구에서는 GA에 의한 최적화과정에서 실수형 설계변수를 직접 사용할 수 있도록 교배와 돌연변이 과정을 새로이 정식화하였다. 그리고 여러 형태의 단일 및 다목적함수 최적화 문제에 대해 실수형 GA와 2진수형 GA의 결과를 비교 검토하였다. 비교 검토 결과, 실수형 GA의 성능이 2진수형 GA보다 우수함을 알 수 있었고, 일반 최적화 방법으로 실수형 GA를 사용하여도 무방하리라 본다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.350-353
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• 2007

This paper presents an real-time implementation of H.264/AVC High 4:4:4 Predictive profile decoder using general-purpose processors by exploiting multi-threading technique and Single Instruction Multiple Data (SIMD) instructions without any quality degradation. We analyze differences between the existing High profile and High 4:4:4 Predictive profile decoder, and show various optimization techniques to decode high fidelity and high definition (HD) video in real-time. Simulation results show that the proposed decoder can play high fidelity HD video at average 40 frames per seconds (fps) for the IBBrBP bistream and about 50 fps for the Intra-only bitstream.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.12-19
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• 2000

In this paper, not only the development of optimizing of friction welding with more reliability and more applicability but also development of in-process real-time weld quality(such as strength and toughness) evaluation technique by acoustic emission for friction welding of the engine exhaustive valve(SUH3-SUH35 dissimilar steels of 12.3mm, 16mm, 20mm and 24mm in diameters) were performed, comparing with the other FRW matches of materials such as SUH3 to SUH31, SUH3 to STS303 and SUH3 to STS304. As an important result, the techniques for dissimilar friction welding optimization of engine heat resisting steels SUH3 and SUH35( 12.3mm, 16mm, 20mm, 24mm) and its real-time weld quality evaluation by AE were developed, considering on both diameter and carbon equivalent effects.

• 한국해양공학회지
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• 제15권2호
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• pp.79-87
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• 2001

In this paper, not only the development of optimizing of friction welding with more reliability and more applicability but also the development of in-process real-time weld quality (such as strength and toughness) evaluation technique by acoustic emission for friction welding of the engine exhaustive valve (SUH3-SUH35 dissimilar steels of 12.3mm, 16mm, 20mm, and 24mm in diameters) were performed, comparing with the other FRW matches of materials such as SUH3 to SUH31, STS303 and SUH3 to STS304. As an important result, the techniques for dissimilar friction welding optimization of engine heat resisting steels SUH3 and SUH35 (12.3mm, 16mm, 20mm, and 24mm) and its real-time weld quality evaluation by AE was developed, considering on both diameter and carbon equivalent effects.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.324-329
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• 2000

Object of a real-time system, that performs exact information based on the real-time constraint. is required for an improvement of high reliability. The fault-tolerant task scheduling strategy of multiprocessor as using a distributed memory based on a hardware redundancy can be improved into a high reliability of the real-time system. Therefore, this paper is shown to analyze the reliability of the system by using the transfer parameter and make the modeling in reference to a minimization of the fault-tolerant task scheduling strategy which uses a percentage of task missing and deadline parameter based on optimization task size.

• 전기학회논문지
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• 제59권1호
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• pp.184-191
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• 2010

Many researchers have been considering genetic algorithms to system optimization problems. Especially, real-coded genetic algorithms are very effective techniques because they are simpler in coding procedures than binary-coded genetic algorithms and can reduce extra works that increase the length of chromosome for wide search space. Thus, this paper presents a fuzzy system design technique to improve the performance of the fuzzy system. The proposed system consists of two procedures. The primary tuning procedure coarsely tunes fuzzy sets of the system using the k-means clustering algorithm of which the structure is very simple, and then the secondary tuning procedure finely tunes the fuzzy sets using enhanced real-coded genetic algorithms based on the primary procedure. In addition, this paper constructs multiple fuzzy systems using a data preprocessing procedure which is contrived for reflecting various characteristics of nonlinear data. Finally, the proposed fuzzy system is applied to the field of time series prediction and the effectiveness of the proposed techniques are verified by simulations of typical time series examples.

• 한국해양공학회지
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• 제29권3호
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• pp.263-269
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• 2015

This paper proposes a new approach for solving the weather routing problem by dividing it into two phases with the goal of fuel saving. The problem is to decide two optimal variables: the heading angle and speed of the ship under several constraints. In the first phase, the optimal route is obtained using the Real-Time Adaptive A* algorithm with a fixed ship speed. In other words, only the heading angle is decided. The second phase is the speed scheduling phase. In this phase, the original problem, which is a nonlinear optimization problem, is converted into a geometric programming problem. By solving this geometric programming problem, which is a convex optimization problem, we can obtain an optimal speed scheduling solution very efficiently. A simple case of numerical simulation is conducted in order to validate the proposed method, and the results show that the proposed method can save fuel compared to a constant engine output voyage and constant speed voyage.

• 한국전산유체공학회지
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• 제9권1호
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• pp.34-40
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• 2004

Recently with growth in the capability of super computers and Parallel computers, shape design optimization is becoming easible for real problems. Also, Computational Fluid Dynamics(CFD) techniques have been improved for higher reliability and higher accuracy. In the shape design optimization, analysis solvers and optimization schemes are essential. In this work, the Roe's 2nd-order Upwind TVD scheme and DADI time march with multigrid were used for the flow solution with the Euler equation and FDM(Finite Differenciation Method), GA(Genetic Algorithm) and Kriging were used for the design optimization. Kriging were applied to 2-D airfoil design optimization and compared with FDM and GA's results. When Kriging is applied to the nonlinear problems, satisfactory results were obtained. From the result design optimization by Kriging method appeared as good as other methods.

• 대한기계학회논문집A
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• 제28권1호
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• pp.48-54
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• 2004

Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. In practical applications, it is customary to transform the dynamic loads into static loads by dynamic factors, design codes, and etc. But the optimization results with the unreasonably transformed loads cannot give us good solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple loading conditions which are not costly to include in modem structural optimization. In this research, the proposed algorithm is applied to the optimization of flexible multibody dynamic systems. The equivalent static load is derived from the equations of motion of a flexible multibody dynamic system. A few examples that have been solved before are solved to be compared with the results from the proposed algorithm.