• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.278-288
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• 1998

An efficient and useful method to improve the local stress field in a displacement-formulated finite element solution has been proposed using the theory of conjugate approximations for a stress field and the Loubignac's iterative method for a displacement field. Validity of the proposed method has been tested through three test examples, to improve the stress field and displacement field in the whole domain and the local regions. As a result of analysis on the test examples, it is found that the stress field in the local regions are approximated to those in the whole domain within a few iterations which have satisfied the original finite element equilibrium equation. In addition, it is found that the local stress field are by far better approximated to the exact stress field than the displacement-based stress field with the reduction of the finite-element mesh-size.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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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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• 2009.11a
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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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• v.36 no.5
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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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• v.32 no.6
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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.

• Journal of Industrial Technology
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• v.22 no.A
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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.

• Journal of Power System Engineering
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• v.10 no.3
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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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• 2006.11a
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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.

• Journal of Energy Engineering
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• v.7 no.2
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• pp.172-179
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• 1998

In this paper, an alternative method which can evaluate a marginal power exceeding yearly peak load for each load bus is proposed. The proportion of the marginal power to yearly peak load for each load bus is defined as Local Marginal Power Rate (LMPR). Furthermore, the composite system is separated base on the LMPR. The bottleneck facilities could be found, while the LMPR is estimated. Then, it is possible to provide information concerning improvement in the system reliability by bottleneck facilities. The IEEE Reliability Test System (RTS) is used to demonstrate the effectiveness of the proposed algorithm.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.2
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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.