• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.70-78
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• 2010

Elitist nondominated sorting genetic algorithm (NSGA-II) is adopted and improved for multiobjective optimal reactive power flow (ORPF) problem. Multiobjective ORPF, formulated as a multiobjective mixed integer nonlinear optimization problem, minimizes real power loss and improves voltage profile of power grid by determining reactive power control variables. NSGA-II-based ORPF is tested on standard IEEE 30-bus test system and compared with four other state-of-the-art multiobjective evolutionary algorithms (MOEAs). Pareto front and outer solutions achieved by the five MOEAs are analyzed and compared. NSGA-II obtains the best control strategy for ORPF, but it suffers from the lower convergence speed at the early stage of the optimization. Several problem-specific local search strategies (LSSs) are incorporated into NSGA-II to promote algorithm's exploiting capability and then to speed up its convergence. This enhanced version of NSGA-II (ENSGA) is examined on IEEE 30 system. Experimental results show that the use of LSSs clearly improved the performance of NSGA-II. ENSGA shows the best search efficiency and is proved to be one of the efficient potential candidates in solving reactive power optimization in the real-time operation systems.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.232-240
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• 2022

To fulfill user expectations, the rapid evolution of software techniques and approaches has necessitated reliable and flawless software operations. Aging prediction in the software under operation is becoming a basic and unavoidable requirement for ensuring the systems' availability, reliability, and operations. In this paper, an improved evolutionary computing-driven extreme learning scheme (ECD-ELM) has been suggested for object-oriented software aging prediction. To perform aging prediction, we employed a variety of metrics, including program size, McCube complexity metrics, Halstead metrics, runtime failure event metrics, and some unique aging-related metrics (ARM). In our suggested paradigm, extracting OOP software metrics is done after pre-processing, which includes outlier detection and normalization. This technique improved our proposed system's ability to deal with instances with unbalanced biases and metrics. Further, different dimensional reduction and feature selection algorithms such as principal component analysis (PCA), linear discriminant analysis (LDA), and T-Test analysis have been applied. We have suggested a single hidden layer multi-feed forward neural network (SL-MFNN) based ELM, where an adaptive genetic algorithm (AGA) has been applied to estimate the weight and bias parameters for ELM learning. Unlike the traditional neural networks model, the implementation of GA-based ELM with LDA feature selection has outperformed other aging prediction approaches in terms of prediction accuracy, precision, recall, and F-measure. The results affirm that the implementation of outlier detection, normalization of imbalanced metrics, LDA-based feature selection, and GA-based ELM can be the reliable solution for object-oriented software aging prediction.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.352-359
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• 2010

In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.53-63
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• 2013

To guide the decision making of the expert engineer specialized in power system operation and control; the practical OPF solution should take in consideration the critical situation due to severe loading conditions and fault in power system. Differential Evolution (DE) is one of the best Evolutionary Algorithms (EA) to solve real valued optimization problems. This paper presents simple Differential Evolution (DE) Optimization algorithm to solving multi objective optimal power flow (OPF) in the power system with shunt FACTS devices considering voltage deviation, power losses, and power flow branch. The proposed approach is examined and tested on the standard IEEE-30Bus power system test with different objective functions at critical situations. In addition, the non smooth cost function due to the effect of valve point has been considered within the second practical network test (13 generating units). The simulation results are compared with those by the other recent techniques. From the different case studies, it is observed that the results demonstrate the potential of the proposed approach and show clearly its effectiveness to solve practical OPF under contingent operation states.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2009년도 춘계 종합학술대회 논문집
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• pp.715-719
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• 2009

RFID 기술를 이용한 다양한 응용분야에서 잘못된 RFID 리더기의 배치로 인해 리더기간의 간섭이 발생한다. 리더기 간의 간섭은 어떤 리더기가 다른 리더기의 동작에 간섭을 일으키는 신호를 송신하여 태그를 인식하는 것을 방해할 때 발생한다. RFID 시스템에서 리더기의 충돌 문제는 시스템 처리량과 인식의 효율성의 병목현상을 발생 시킨다. 본 논문에서는 RIFD 안테나 배치의 적합도를 높이기 위해서 진화 연산 기법을 이용한 새로운 RFID 리더기 배치 설계 시스템을 제안한다. 먼저, 주위 환경에 민감한 안테나의 전파 특성을 분석하고, 특성 데이터베이스를 구축한다. 그리고, 안테나를 최적으로 배치하기 위한 EA Encoding 기법과 Fitness 기법 및 유전잔 연산자를 제안한다. 제안하는 기법의 우수성을 보이기 위해서 시뮬레이션을 수행하였으며, 실험 결과, 약 100세대의 진화 연산을 통해 커버율 95.45%, 간섭율 10.29%의 RFID 안테나 배치의 적합도를 달성하였다.

• 한국지능시스템학회논문지
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• 제24권3호
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• pp.330-336
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• 2014

연속교반탱크반응기, 담수화 플랜트, 증류탑, pH 중화 프로세스 등을 포함한 많은 산업용 프로세스들은 높은 비선형성과 시변 특성으로 인해 제어가 까다로워 보다 정밀하고 안정된 성능을 가지는 제어기를 설계하려는 많은 노력들이 있어 왔다. 본 논문에서는 기존 연구의 단점을 개선한 CSTR 프로세스의 농도제어용 PID 제어기를 동조하는 문제를 다룬다. 액추에이터 포화 문제를 극복하기 위해 PID 제어기에는 적분기 안티와인드업 피드백 루프가 구성되며, PID 제어기의 파라미터는 전체 제어 프로세스가 만족스러운 설정치 추종 성능을 가지도록 진화연산(EA)에 의해 동조된다. 제안하는 방법은 시뮬레이션을 통해 설정치 추종 성능, 외란 억제 성능과 파라미터 변동에 대한 강인성을 확인한다.

• Nuclear Engineering and Technology
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• 제41권2호
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• pp.143-148
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• 2009

The increasing power and other demands on PWR fuel is leading to a demand for cladding that has low corrosion but that should also be robust with regard to mechanical behavior, impact of the irradiation environment and the coolant chemistry. The Optimized $ZIRLO^{TM}$ cladding is an evolutionary development of $ZIRLO^{TM}$ taking advantage of the long experience of the ZIRLO cladding but has significantly improved corrosion behavior. Recently, operation of Optimized ZIRLO to above 73 kWd/kgU has shown a reduction of the corrosion of almost 50%.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권7호
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• pp.317-322
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• 2005

Advantages of switched reluctance motor(SRM) include a simple structure, the ability of operation in hash environments and under partial hardware failures, and a wide speed range. However design of SRM for industrial applications is very difficult because motor's inherent none-linearity and sensitivity of design parameter. In this paper, an optimal method for determining design parameters of a switched reluctance motor is researched. The dominant design parameters are stator and rotor pole arc and switching on and off angle. The parameters affecting performance are examined and selected using evolutionary computations and commercial CAD Program. The proposed design process is very fast. reliable and easy to access. The simulated design method proposed is compared with conventional procedure.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.383-394
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• 2001

The stabilization control of inverted pendulum (IP) system is difficult because of its nonlinearity and structural unstability. In this paper, an Evolving Neural Network Controller (ENNC) without Error Back Propagation (EBP) is presented. An ENNC is described simply by genetic representation using an encoding strategy for types and slope values of each active functions, biases, weights and so on. By an evolutionary programming which has three genetic operation; selection, crossover and mutation, the predetermine controller is optimally evolved by updating simultaneously the connection patterns and weights of the neural networks. The performances of the proposed ENNC(PENNC)are compared with the one of conventional optimal controller and the conventional evolving neural network controller (CENNC) through the simulation and experimental results. And we showed that the finally optimized PENNC was very useful in the stabilization control of an IP system.

• 품질경영학회지
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• 제43권1호
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• pp.1-10
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• 2015

Purpose: It can be said that the 21st century is the age of creativity. However creativity has been relatively less considered in comparison with control and continuous improvement in quality management. How to incorporate creativity into quality management is treated in this paper. Methods: The opposing characteristics of quality and creativity are examined, and the possible outcomes resulted from the conflict are reviewed. Previous researches on managing evolutionary and revolutionary changes are also examined. Results: Quality and creativity require each other although they have incompatible characteristics, and can be incorporated into the innovation cycle. Conclusion: Creative thinking tools such as SIT should be included in the quality training and education for the effective operation of the innovation cycle.