• 설비공학논문집
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• 제15권4호
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• pp.318-328
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• 2003

Numerical simulation using computational fluid dynamics (CFD) is performed to calculate the velocities and temperature profiles of air in adjacent to a worker within the individual local air conditioning system. The calculation domain is the space of ㄴ between walls and a worker in the climate room. The fresh air is supplied from the three different inlets located on the right, left and center wall in the climate room. In this study, the calculated data of velocities and temperature profiles of air in the nearest the skin of a worker are used to calculate the PMV (Predicted Mean Vote) for evaluation of thermal comfort of a worker in the local air conditioning system. Because the data of veto-cities temperature profiles of air in adjacent to a worker and the PMV of a worker are the design parameters of the local air conditioning system. The results of calculation show that the fresh air velocity and injection position are closely related to the PMV value. In individual air condition system of ㄴ, the appropriate PMV are obtained when the fresh air velocity and position are 1.0 m/s, throat of a worker and are 1.5 m/s, head of a worker, respectively. The method of numerical calculation is effective to obtain the optimum velocity and position of the fresh air for optimum the PMV and energy saving in individual local air conditioning system.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.142-147
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• 2009

In order to achieve performance assessment and optimal control of a double-skin system, an accurate simulation model is required. In the previous study, a lumped simulation model of such system was developed. As a follow-up of the previous research, the first objective of this paper is to investigate how the mathematical model should be calibrated according to system configuration(cavity width, depth, height, airflow pattern, local environment, etc.). And the second objective of this study is to discuss the effect of local weather information. In conclusion, this paper describes that the model should be recalibrated according to configuration. And it is necessary to have local weather information for accurate prediction and optimal control of the system.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.420-429
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• 2004

The local power density should be estimated accurately to prevent fuel rod melting. The local power density at the hottest part of a hot fuel rod, which is described by the power peaking factor, is more important information than the local power density at any other position in a reactor core. Therefore, in this work, the power peaking factor, which is defined as the highest local power density to the average power density in a reactor core, is estimated by fuzzy neural networks using numerous measured signals of the reactor coolant system. The fuzzy neural networks are trained using a training data set and are verified with another test data set. They are then applied to the first fuel cycle of Yonggwang nuclear power plant unit 3. The estimation accuracy of the power peaking factor is 0.45% based on the relative $2_{\sigma}$ error by using the fuzzy neural networks without the in-core neutron flux sensors signals input. A value of 0.23% is obtained with the in-core neutron flux sensors signals, which is sufficiently accurate for use in local power density monitoring.

• ETRI Journal
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• 제32권6호
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• pp.932-939
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• 2010

In this paper, a fast migration method is proposed. Our method executes local relocation on a model placement where an additional module is added to it for modification with a minimum number of displacements. This method is based on mean-field annealing (MFA), which produces a solution as reliable as a previously used method called simulated annealing. The proposed method requires substantially less time and hardware, and it is less sensitive to the initial and final temperatures. In addition, the solution runtime is mostly independent of the size and complexity of the input model placement. Our proposed MFA algorithm is optimized by enabling module rotation inside an energy function called permissible distances preservation energy. This, in turn, allows more options in moving the engaged modules. Finally, a three-phase cooling process governs the convergence of problem variables called neurons or spins.

• 산업기술연구
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• 제22권A호
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• pp.29-36
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• 2002

A damage detection algorithm using vibration modes is applied to the ring structures and the modal behaviors of the slightly asymmetric rings are examined. Mode shape change, MSER(modal strain energy ratio) and MCR(modal curvature ratio) are investigated to identify the locations of faults or damages The above fault detection parameters are calculated and compared by the finite element analysis on rings with designed local damages. Damages are modeled as a reduced stiffness in the analysis The results show that MSER and MCR can be proper parameters to detect local damages in the ring structures.

• 동력기계공학회지
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• 제10권3호
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• pp.38-44
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• 2006

Failure assessment of steam generator tube are very important for the integrity of energy plants. In pipes of energy plants, sometimes, the local wall thinning may result from severe erosion-corrosion damage. Recently, the effects of local wall thinning on fracture strength and fracture behavior of piping system have been well studied. In this paper, the elasto-plastic analysis is performed by FE code ANSIS on steam generator tube with wall thinning. We evaluated the failure mode, fracture strength and fracture behavior from FE analysis. It was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the thinned area.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.153-156
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• 2006

The domestic solar radial ion data have been measured at 16 different sites all over the country since the beginning of 1980. It is very important that the fundamental data for the estimation and assessment of local solar radiation can be secured this project. In order to estimate available energy resource from solar radiation, it is necessary to have enough data, more than 30 years In any country. However since we have collected solar radiation(global radial ion including direct normal radiation) data only for 10 years we still need to measure insolation to secure the reliability and standardization of measured local solar radial ion data. In brief, the major activities on this R&D include rout me maintenance of the national network for insolation data measurement, evaluation of the collected data, and reliability enhancement for assessing the quality of solar radiation data as well.

• 에너지공학
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• 제7권2호
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• pp.172-179
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• 1998

본 연구에서는 복합계통의 수송능력을 평가하던 종래의 연구결과를 발견시켜,‘각 지역에 공급되는 전력이 예측된 최대부하에 대해 얼마만큼의 여유가 있는가’를 계산하는 방법을 제안한다. 각 부하모선의 수송여유에 따른 지역간 분할의 내용을 소개하며, 계산과정에서 병목선로도 탐색하도록 하였다. 그 결과 계통에서 취약한 수송여유를 보이는 부하모선의 신뢰도 향상에 관한 자료를 얻을 수 있었다. 제안한 앨고리즘을 IEEE 신뢰도 모델계통에 적용하여 그 유용성을 검증하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제21권2호
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• pp.63-73
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• 2017

Segmenting the image into multiple regions is at the core of image processing. Many segmentation formulations of an images with multiple regions have been suggested over the years. We consider segmentation algorithm based on the multi-phase level set method in this work. Proposed method gives the best result upon other methods found in the references. Moreover it can segment images with intensity inhomogeneity and have multiple junction. We extend our method (GLIF) in [T. Dultuya, and M. Kang, Segmentation with shape prior using global and local image fitting energy, J.KSIAM Vol.18, No.3, 225-244, 2014.] using a multiphase level set formulation to segment images with multiple regions and junction. We test our method on different images and compare the method to other existing methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2616-2618
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• 2005

Time-frequency analysis (TFA) method was applied to identify the integrity of the internal local surface of a pipe where some chemical corrosions are likely to occur by acid mixed in the coolant of nuclear power plants. The spalling out of internal material pieces by corrosion induces some transient signals and the change of structural vibration of a local point in the pipe. It is therefore possible to detect the corrosion detachment through the measurement of the transient acoustic signals or the vibration signals. In this presentation, the TFA was configured on the vibrational signal data of the pipe and it is identified that the TFA can Provide an important information, i.e., the amplitude fluctuations in the instantaneous frequency of each characteristic frequency.