• 전기전자학회논문지
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• 제6권2호
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• pp.136-145
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• 2002

정상상태에서 소자 내부의 격자온도 분포를 해석할 수 있는 시뮬레이터를 개발하였다. Slotboom 변수를 사용하여 열흐름 방정식을 이산화하였고, 요소내에서 열전도율의 적분값을 해석적으로 구할 수 있는 방법을 제안하였다. 제안된 방법의 타당성을 검증하기 위해 $N^+P$ 접합 다이오드와 BJT에 대해 모의실험을 수행하였고 DAVINCI와 MEDICI의 결과와 비교하였다. $N^+P$ 접합 다이오드에서 순방향 인가전압이 1.4[V]일 때 격자 온도분포는 DAVINCI의 결과와 2%의 상대오차를 보였으며 BJT에서 컬렉터 전압이 5.0[V]이고 베이스 전압이 0.5[V]일 때 격자 온도분포는 MEDICI의 결과와 3%의 상대오차를 보였다. BANDIS에서 제안된 열전도율의 적분방법을 사용하는 경우 수렴을 위해 평균 3.45회의 행렬 연산이 필요하나 DAVINCI에서는 평균 5.1회의 행렬 연산이 필요하였고 MEDICI는 평균 4.3회 행렬연산이 필요하였다.

• 한국공간정보시스템학회 논문지
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• 제10권3호
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• pp.31-43
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• 2008

주행 시간 예측은 첨단 여행정보 시스템 (ATIS) 및 교통관리 시스템 (ITS)에서 필수적이다. 이를 위해 본 연구에서는 대용량의 데이터 분류에서 높은 정확도와 빠른 속도를 보장하는 $Na{\ddot{i}}ve$ Bayesian 분류화 기법을 기반으로 한 주행시간 예측 알고리즘을 제안한다. 제안된 알고리즘은 도로 네트워크 상에서 사용자 지정 주행 경로에 대하여 주행시간 예측이 가능하며, 또한 주어진 경로에 대해 시간대 별 평균 구간 속도를 고려하여 보다 정확한 주행 시간 예측을 수행한다. 제안된 알고리즘을 기존의 링크-기반 예측(link-based prediction)알고리즘[1] 및 Micro T* 알고리즘[2]과 성능 비교를 수행하였다. 성능 비교 결과, 제안된 기법이 타 예측기법에 비해 MARE (mean absolute relative error)가 크게 감소하여 성능이 향상되었음을 보였다.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2343-2351
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• 2024

Accurately predicting the thermal hydraulic parameters of a transient reactor core under different working conditions is the first step toward reactor safety. Mass flow rate and temperature are important parameters of core thermal hydraulics, which have often been modeled as time series prediction problems. This study aims to achieve accurate and continuous prediction of core thermal hydraulic parameters under instantaneous conditions, as well as test the feasibility of a newly constructed gated recurrent unit (GRU) model based on the soft attention mechanism for core parameter predictions. Herein, the China Experimental Fast Reactor (CEFR) is used as the research object, and CEFR 1/2 core was taken as subject to carry out continuous predictive analysis of thermal parameters under transient conditions., while the subchannel analysis code named SUBCHANFLOW is used to generate the time series of core thermal-hydraulic parameters. The GRU model is used to predict the mass flow and temperature time series of the core. The results show that compared to the adaptive radial basis function neural network, the GRU network model produces better prediction results. The average relative error for temperature is less than 0.5 % when the step size is 3, and the prediction effect is better within 15 s. The average relative error of mass flow rate is less than 5 % when the step size is 10, and the prediction effect is better in the subsequent 12 s. The GRU model not only shows a higher prediction accuracy, but also captures the trends of the dynamic time series, which is useful for maintaining reactor safety and preventing nuclear power plant accidents. Furthermore, it can provide long-term continuous predictions under transient reactor conditions, which is useful for engineering applications and improving reactor safety.

• 대한전기학회논문지
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• 제43권5호
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• pp.730-738
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• 1994

The major advantage of the short-term load forecasting technique using general exponential smoothing is high accuracy and operational simplicity, but it makes large forecasting error when the load changes repidly. The paper has presented new technique to improve those shortcomings, and according to forecasted the technique proved to be valid for two years. The structure of load model is time function which consists of daily-and temperature-deviation component. The average of standard percentage erro in daily forecasting for two years was 2.02%, and this forecasting technique has improved standard erro by 0.46%. As relative coefficient for daily and seasonal forecasting is 0.95 or more, this technique proved to be valid.

• Membrane and Water Treatment
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• 제9권5호
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• pp.363-371
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• 2018

In this work, it was investigated the usability of artificial bee colony (ABC) and genetic algorithm (GA) in modeling adsorption of Co(II) onto drinking water treatment sludge (DWTS). DWTS, obtained as inevitable byproduct at the end of drinking water treatment stages, was used as an adsorbent without any physical or chemical pre-treatment in the adsorption experiments. Firstly, DWTS was characterized employing various analytical procedures such as elemental, FT-IR, SEM-EDS, XRD, XRF and TGA/DTA analysis. Then, adsorption experiments were carried out in a batch system and DWTS's Co(II) removal potential was modelled via ABC and GA methods considering the effects of certain experimental parameters (initial pH, contact time, initial Co(II) concentration, DWTS dosage) called as the input parameters. The accuracy of ABC and GA method was determined and these methods were applied to four different functions: quadratic, exponential, linear and power. Some statistical indices (sum square error, root mean square error, mean absolute error, average relative error, and determination coefficient) were used to evaluate the performance of these models. The ABC and GA method with quadratic forms obtained better prediction. As a result, it was shown ABC and GA can be used optimization of the regression function coefficients in modeling adsorption experiments.

• 한국환경과학회지
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• 제22권9호
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• pp.1171-1180
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• 2013

Recent climate change has led to fluctuations in agricultural production, and as a result national food supply has become an important strategic factor in economic policy. As such, in this study, panel data was collected to analyze the effects of seven meteorological elements and using the Lagrange multipliers method, the fixed-effects model for the production of five types of food crop and the seven meteorological elements were analyzed. Results showed that the key factors effecting increases in production of rice grains were average temperature, average relative humidity and average ground surface temperature, while wheat and barley were found to have positive correlations with average temperature and average humidity. The implications of this study are as follow. First, it was confirmed that the meteorological elements have profound effects on the production of food crops. Second, when compared to existing studies, the study was not limited to one food crop but encompassed all five types, and went beyond other studies that were limited to temperature and rainfall to include various meterological elements.

• 전자공학회논문지D
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• 제34D권8호
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• pp.15-25
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• 1997

The integration method of carier concentrations to redcue the discretization error of th box integratio method used in the discretization of the three-dimensional poisson's equation is presented. The carrier concentration is approximated in the closed form as an exponential function of the linearly varying potential in the element. The presented method is implemented in the three-dimensional poisson's equation solver running under the windows 95. The accuracy and the convergence chaacteristics of the three-dimensional poisson's equation solver are compared with those of DAVINCI for the PN junction diode and the n-MOSFET under the thermal equilibrium and the DC reverse bias. The potential distributions of the simulatied devices from the three-dimensional poisson's equation solver, compared with those of DAVINCI, has a relative error within 2.8%. The average number of iterations needed to obtain the solution of the PN junction diode and the n-MOSFET using the presented method are 11.47 and 11.16 while the those of DAVINCI are 21.73 and 23.0 respectively.

• Journal of Communications and Networks
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• 제7권4호
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• pp.429-437
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• 2005

Sensor localization has become an essential requirement for realistic applications over wireless sensor networks (WSN). In this paper we propose an ad hoc localization algorithm that is infrastructure-free, anchor-free, and computationally efficient with reduced communication. A novel combination of distance and direction estimation technique is introduced to detect and estimate ranges between neighbors. Using this information we construct unidirectional coordinate systems to avoid the reflection ambiguity. We then compute node positions using a transformation matrix [T], which reduces the computational complexity of the localization algorithm while computing positions relative to the fixed coordinate system. Simulation results have shown that at a node degree of 9 we get $90\%$ localization with $20\%$ average localization error without using any error refining schemes.

• 대한음성학회지:말소리
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• 제67호
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• pp.149-166
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• 2008

In spoken document retrievals (SDR), subword (typically phonemes) indexing term is used to avoid the out-of-vocabulary (OOV) problem. It makes the indexing and retrieval process independent from any vocabulary. It also requires a small corpus to train the acoustic model. However, subword indexing term approach has a major drawback. It shows higher word error rates than the large vocabulary continuous speech recognition (LVCSR) system. In this paper, we propose an probabilistic slot detection and n-gram based string matching method for phone based spoken document retrievals to overcome high error rates of phone recognizer. Experimental results have shown 9.25% relative improvement in the mean average precision (mAP) with 1.7 times speed up in comparison with the baseline system.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.55-62
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• 2004

This paper addresses the method for figuring out the hole diameter on the mask containing the information about machining depth. With this mask e micro machining is carried out with a simple 2D movement of the mask. Based on e suggested method excimer laser ablation processes are modeled and determination of the optimal laser ablation conditions such as hole diameter, step size, mask movement velocity, etc. is completed. The excimer laser ablation simulation for creating 3D micro lens is carried out by employing determined ablation conditions to prove verification of the method. The results from simulation illustrated the average error of 140nm and e relative error of 2％.