• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.1966-1973
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• 2023

Virtual reality technology has been widely used in the field of nuclear and radiation safety, dose rate computing in virtual environment is essential for optimizing radiation protection and planning the work in radioactive-controlled area. Because the CPU-based gamma dose rate computing takes up a large amount of time and computing power for voxelization of volumetric radioactive source, it is inefficient and limited in its applied scope. This study is to develop an efficient gamma dose rate computing code and apply into fast virtual simulation. To improve the computing efficiency of the point kernel algorithm in the reference (Li et al., 2020), we design a GPU-based computing framework for taking full advantage of computing power of virtual engine, propose a novel voxelization algorithm of volumetric radioactive source. According to the framework, we develop the GPPK(GPU-based point kernel gamma dose rate computing) code using GPU programming, to realize the fast dose rate computing in virtual world. The test results show that the GPPK code is play and plug for different scenarios of virtual simulation, has a better performance than CPU-based gamma dose rate computing code, especially on the voxelization of three-dimensional (3D) model. The accuracy of dose rates from the proposed method is in the acceptable range.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.629-632
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• 1997

This paper presents the design method of controller which is combined Genetic Algorithms with the Generalized minimum variance self tuning controller. It is shown that the controllers adapts to changes in the system parameters with time delays and noises. The self tuning effect is achieved through the recursive least square algorithm at the parameter estimation stage and also through the Robbins-Monro algorithm at the stage of optimizing a polynomial parameters. The computer simulation results are presented to illustrate the procedure and to show the performance of the control system.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.607-612
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• 1998

In this paper, a controller using fuzzy-genetic algorithms is proposed for pat-tracking of WMR. A fuzzy controller is implemented so as to adjust appropriate crossover rate and mutation rate. A genetic algorithms is also implemented to have adaptive adjustment of control gain during optimizing process. To check effectiveness of this algorithms, computer simulation is applied.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.847-852
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• 1993

In this paper, we present a recursive algorithm for the auto-tuning of PID controllers by optimizing a GPC criterion. Also, we develop an intelligent PID controller by combination of a recursive algorithm together with a supervisor, that allows to adjust the main controller parameters (prediction horizon, control weighting, sample time etc.) using some simple rules which is mainly built up through relay tuning experiments. The intelligent PID controller has been implemented successfully on an IBM PC/AT and some simulation results are presented.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.968-971
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• 1996

In this paper, feedback controller is designed for ball-beam system using genetic algorithms. A genetic algorithms are implemented for optimizing gain parameters of feedback controller. We can find optimal point in multi-dimensional search space by using genetic algorithms. Performance of controller is tested by simulation of ball-beam system.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.452-455
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• 1999

Genetic algorithm is well known as the efficient algorithm which can solve a difficult problem. Network design considering reliability is NP-hard problem with cost, distance, and volume. Therefore genetic algorithm is considered as a good method for this problem. This paper suggests the reliable network which can be constructed with minimum cost using genetic algorithm and the rank method based on reliability for improving the performance. This method shows more excellent than existing method and confirms the result through simulation.

• ETRI Journal
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• v.27 no.6
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• pp.798-801
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• 2005

This Letter proposes a scheme that supports a fast handover effectively in hierarchical mobile IPv6 networks (F-HMIPv6) by optimizing the associated data and control flows during the handover. By NS-2 simulation, we show that the proposed scheme can give better handover performance than a simple combination of existing schemes.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.662-668
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• 2006

The effects of fuel injection nozzle hole on the NOx emission and fuel oil consumption of medium speed diesel engine HYUNDAI HiMSEN 6H21/32 engine are investigated by engine performance simulation. The results of performance simulation are verified by experimental results of NOx omission fuel oil consumption, cylinder pressure, and heat release rate according to the variation of the number of fuel injection nozzle hole and engine load. The performance simulations are also carried out to optimize the fuel injection nozzle of 6H21/32 engine in respect to the NOx emission and fuel oil consumption. The engine performance measurements are performed to verify the results of performance simulation and to investigate the effects of fuel injection nozzle on engine performance. The results of measurement indicate that significant NOx reduction can be achieved with minimum deterioration in fuel oil consumption by optimizing the geometry of fuel injection nozzle on 6H21/32 engine.

• Journal of Internet of Things and Convergence
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• v.7 no.4
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• pp.9-14
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• 2021

In computing systems that require high reliability, the method of predicting the lifetime of a storage device is one of the important factors for system management because it can maximize usability as well as data protection. The life of a solid state drive (SSD) that has recently been used as a storage device in several storage systems is linked to the life of the NAND flash memory that constitutes it. Therefore, in a storage system configured using an SSD, a method of accurately and efficiently predicting the lifespan of a NAND flash memory is required. In this paper, a method for optimizing the lifetime prediction of a flash memory-based storage device using the frequency of NAND flash memory failure is proposed. For this, we design a cost matrix to collect the frequency of defects that occur when processing data in units of Drive Writes Per Day (DWPD). In addition, a method of predicting the remaining cost to the slope where the life-long finish occurs using the Gradient Descent method is proposed. Finally, we proved the excellence of the proposed idea when any defect occurs with simulation.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.361-366
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• 2009

We propose the performance enhancing method optimization of an asynchronous 2.5 Gbps/1.25 Gbps optical subscriber network with inverse RZ (Return to Zero) coded downstream and NRZ (Non Return to Zero) upstream re-modulation by adjusting threshold level control of a receiver. We theoretically analyze the BER (Bit Error Rate) performance by modeling the occurrence of BER by simulation with MATLAB according to the types of downstream data. The results have shown that the normalized threshold level in an optical receiver could be saturated at 1/3 as the SNR (Signal to Noise Ratio) increases. The needed SNR for obtaining the BER $10^{-9}$ can be reduced by $\sim$5 dB by optimizing the normalized threshold level at 1/3 instead of by using the conventional receiver with threshold level of 0.5. The proposed system can be a useful technology for asynchronous optical access networks with asymmetric upstream and downstream data rates, because the improved minimum receiving power could replace a light source with a source with lower power and lower cost in an OLT (Optical Line Termination).