• Journal of the Optical Society of Korea
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• 제14권1호
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• pp.22-27
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• 2010

Bit error rate (BER) monitoring is the ultimate goal of performance monitoring in all digital transmission systems as well as optical fiber transmission systems. To achieve this goal, optimization of the decision threshold must also be considered because BER is dependent on the level of decision threshold. In this paper, we analyze a pseudo-error counting scheme and propose an algorithm to achieve both BER monitoring and adaptive decision threshold optimization in optical fiber transmission systems. To verify the effectiveness of the proposed algorithm, we conduct computer simulations in both Gaussian and non-Gaussian distribution cases. According to the simulation results, BER and the optimum decision threshold can be estimated with the errors of < 20% and < 10 mV, respectively, within 0.1-s processing time in > 40-Gb/s transmission systems.

• 한국시뮬레이션학회논문지
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• 제26권3호
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• pp.55-63
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• 2017

곡사포의 사격오차는 탄착의 분산도와 탄착중심오차(MPI)를 포괄하는 용어로, 본 연구에서는 사격시험을 수행하지 않고 정량적 분석을 통해 사격오차를 예측하는 기법에 대해 논하고자 한다. 기존에도 곡사포의 사격오차를 예측하기 위한 분석기법은 있었지만, 오차에 관여하는 영향요소들에 대한 정보가 부족하여 활용이 제한되었다. 본 연구에서는 이런 문제를 해결하기 위해 누적된 시험이 수행된 기존 무기체계 시험결과를 활용하여, 오차의 원인이 되는 각 요소 값들을 역으로 산출하는 방식을 제안한다. 이 과정에서 항공공학 분야에서 흔히 사용되는 최적화 알고리즘을 이용한 입력계수 추출 방식을 도입하였다. 최적화 알고리즘으로는 CMA-ES라는 진화적 기법을 소개하며, 적용 결과에 대하여 해설하였다. 이런 과정을 통해 얻은 사격오차요인 값은 향후 신규 무기체계 개발에 있어 성능요구사항 산출에 사용될 수 있으며, 야전에서의 곡사포 정확도 향상에도 기여할 것으로 보인다.

• 전력전자학회논문지
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• 제25권3호
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• pp.227-234
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• 2020

This paper presents the methods for the modeling and parameter optimization of the electric vehicle battery. The state variables of the battery are defined, and the test methods for battery parameters are presented. The state-space equation, which consists of four state variables, and the output equation, which is a combination of to-be-determined parameters, are shown. The parameter optimization method is the key point of this study. The least square of the modeling error can be used as an initial value of the multivariable function. It is equivalent to find the minimum value of the error function to obtain optimal parameters from multivariable function. The SIMULINK model is presented, and the 10-hour full operational range test results are shown to verify the performance of the model. The modeling error for 25 degrees is approximately 1% for full operational ranges. The comments to enhance modeling accuracy are shown in the conclusion.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (2)
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• pp.700-702
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• 2004

A local-step optimization method is proposed to supplement the global-step optimization methods which adopt online update mode of internal weights and error energy as stop criterion in learning of multilayer perceptrons (MLPs). This optimization method is applied to the standard online error backpropagation(EBP) and the performance is evaluated for a speaker verification system.

• ETRI Journal
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• 제45권1호
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• pp.119-130
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• 2023

We propose a quantized gradient search algorithm that can achieve global optimization by monotonically reducing the quantization step with respect to time when quantization is composed of integer or fixed-point fractional values applied to an optimization algorithm. According to the white noise hypothesis states, a quantization step is sufficiently small and the quantization is well defined, the round-off error caused by quantization can be regarded as a random variable with identically independent distribution. Thus, we rewrite the searching equation based on a gradient descent as a stochastic differential equation and obtain the monotonically decreasing rate of the quantization step, enabling the global optimization by stochastic analysis for deriving an objective function. Consequently, when the search equation is quantized by a monotonically decreasing quantization step, which suitably reduces the round-off error, we can derive the searching algorithm evolving from an optimization algorithm. Numerical simulations indicate that due to the property of quantization-based global optimization, the proposed algorithm shows better optimization performance on a search space to each iteration than the conventional algorithm with a higher success rate and fewer iterations.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제10권2호
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• pp.128-133
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• 2010

This paper presents a method for estimating the parameters of dynamic models for induction motor dominating loads. Using particle swarm optimization, the method finds the adequate set of parameters that best fit the sampling data from the measurement for a period of time, minimizing the error of the outputs, active and reactive power demands and satisfying the steady-state error criterion.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.75-78
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• 2004

A mesh generation algorithm adapted to the mesh density map using the Delaunay mesh generation technique is developed. In the finite element analyses of the forging processes, the numerical error increases as the process goes on because of discrete property of the finite elements or severe distortion of elements. Especially, in the region where stresses and strains are concentrated, the numerical discretization error will be highly increased. However, it is too time consuming to use a uniformly fine mesh in the whole domain to reduce the expected numerical error. Therefore, it is necessary to construct locally refined mesh at the region where the error is concentrated such as at the die corner. In this study, the point insertion algorithm is used and the mesh size is controlled by moving nodes to optimized positions according to a mesh density map constructed with a posteriori error estimation. An optimization technique is adopted to obtain a good position of nodes. And optimized smoothing techniques are also adopted to have smooth distribution of the mesh and improve the mesh element quality.

• 한국지능시스템학회논문지
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• 제18권5호
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• pp.611-616
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• 2008

Error correcting codes는 일반적으로 soft error를 막기 위해서 사용된다. single error의 수정과 double error의 검출(SEC-DED) 코드들은 이런 목적으로 사용된다. 본 논문에서는 이러한 회로의 크기, 지연시간, 전력 소비를 선택적으로 최소로 하는 SEC-DED의 설계방법을 제안한다. 이러한 SEC-DED의 설계는 비선형 최적화 문제로 포함되는데 우리는 다목적 유전자 알고리즘을 이용하여 이 문제를 해결한다. 제안하는 방법은 여러 가지 SEC-DED code들을 제공하여 사용자의 환경에 따라 알맞은 회로를 선택할 수 있도록 한다. 제안하는 방법을 효율적인 ECC코드로 알려져 있는 odd-column weight Hsiao code에 적용하여 그 효율성을 입증하였다.

• 산업경영시스템학회지
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• 제43권2호
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• pp.1-13
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• 2020

There are several methods of peak-shaving, which reduces grid power demand, electricity bought from electricity utility, through lowering "demand spike" during On-Peak period. An optimization method using linear programming is proposed, which can be used to perform peak-shaving of grid power demand for grid-connected PV+ system. Proposed peak shaving method is based on the forecast data for electricity load and photovoltaic power generation. Results from proposed method are compared with those from On-Off and Real Time methods which do not need forecast data. The results also compared to those from ideal case, an optimization method which use measured data for forecast data, that is, error-free forecast data. To see the effects of forecast error 36 error scenarios are developed, which consider error types of forecast, nMAE (normalizes Mean Absolute Error) for photovoltaic power forecast and MAPE (Mean Absolute Percentage Error) for load demand forecast. And the effects of forecast error are investigated including critical error scenarios which provide worse results compared to those of other scenarios. It is shown that proposed peak shaving method are much better than On-Off and Real Time methods under almost all the scenario of forecast error. And it is also shown that the results from our method are not so bad compared to the ideal case using error-free forecast.

• 대한전자공학회논문지SD
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• 제45권1호
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• pp.43-49
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• 2008

본 논문에서는 Ant Colony Optimization(ACO)을 이용하여 Single-Error Correcting & Double-Error Detecting(SEC-DED)을 제공하는 메모리 ECC 체커 회로의 소비전력을 절감하는 방안을 제시한다. H-매트릭스를 통해 구현되는 SEC-DED 코드인 Hsiao 코드의 대칭성과 H-매트릭스 구성상의 높은 자유도를 이용하여 회로의 면적, 딜레이에 영향을 주지 않고 최소의 비트 트랜지션이 일어나도록 H-매트릭스를 최적화한다. 실험을 통하여 H-매트릭스의 최적화를 위한 ACO 매핑과 파라메터의 설정을 알아보고 이의 구현 결과를 랜덤 매트릭스 구성을 통한 방식 및 기존의 GA알고리즘을 이용한 최적화 방식과 비교하여 소비 전력이 기존의 방식에 비해 절감될 수 있음을 보여준다.