• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.833-841
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• 2021

During the postulated severe accident of nuclear reactor, eutectic reaction leads to low-temperature melting of fuel cladding and early failure of core structure. In order to model eutectic melting with the moving particle semi-implicit (MPS) method, the eutectic reaction model is developed to simulate the eutectic reaction phenomenon. The coupling of mass diffusion and phase diagram is applied to calculate the eutectic reaction with the uniform temperature. A heat transfer formula is proposed based on the phase diagram to handle the heat release or absorption during the process of eutectic reaction, and it can combine with mass diffusion and phase diagram to describe the eutectic reaction with temperature variation. The heat transfer formula is verified by the one-dimensional melting simulations and the predicted interface position agrees well with the theoretical solution. In order to verify the eutectic reaction models, the eutectic reaction of uranium and iron in two semi-infinite domains is simulated, and the profile of solid thickness decrease over time follows the parabolic law. The modified MPS method is applied to calculate Transient Reactor Test Facility (TREAT) experiment, the penetration rate in the simulations are agreeable with the experiment results. In addition, a hypothetical case based on the TREAT experiment is also conducted to validate the eutectic reaction with temperature variation, the results present continuity with the simulations of TREAT experiment. Thus the improved method is proved to be capable of simulating the eutectic reaction in the severe accident.

• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.1179-1189
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• 2017

In this study, we propose an alternative method for discriminant analysis using a multivariate empirical distribution function to express multivariate data as a simple one-dimensional statistic. This method turns to be the estimation process of the optimal threshold based on classification accuracy measures and an empirical distribution function of data composed of classes. This can also be visually represented on a two-dimensional plane and discussed with some measures in ROC curves, surfaces, and manifolds. In order to explore the usefulness of this method for discriminant analysis in the study, we conducted comparisons between the proposed method and the existing methods through simulations and illustrative examples. It is found that the proposed method may have better performances for some cases.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.929-935
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• 2001

Two-dimensional computer simulations were conducted on percolation structure in which second phases of various aspect ratios were arranged in a lattice (matrix). The second phases were randomly arranged in an array with two different computational programs; one prohibiting an overlap among second phases and the other allowing the overlap. From the simulation prohibiting the overlap, it was predicted that a complete path was formed at less amounts of the second phase with higher aspect ratios. In the simulation allowing the overlap, a complete path throughout the array was formed by arranging the second phase of an aspect ratio of 1. 5, 20, 100 with less than 59%, 43%, 19%, 4% in the array, respectively.

• Coupled systems mechanics
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• v.7 no.3
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• pp.255-268
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• 2018

Stability of MBC1, a specific matching boundary condition, is proved for atomic simulations of a diatomic chain. The boundary condition and the Newton equations that govern the atomic dynamics form a coupled system. Energy functions that decay along with time are constructed for both the boundary with the same type atoms and the one with different type atoms. For a nonlinear chain, MBC1 is also shown stable. Numerical verifications are presented. Moreover, MBC1 is proved to be stable for a two dimensional square lattice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.29-34
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• 1993

In this paper, we used one-dimensional process simulator, SUPREM-II, and two-dimensional device simulator, MINIMOS 4.0 to extract optimal process parameter that can minimize degradation of device characteristics caused by process parameter variation in the case of short channel nMOSFET and pMOSFET device. From this simulation, we have derieved the relationship between process parameter and device characteristics. Here we have presented a method to extract process parameters from design trend curve(DTC) obtained by process and device simulations. We parameters to verify the validity of the DTC method. The experimental result of 0.8 $\mu\textrm{m}$ channel length devices that have been fabricated with optimal that reduces short channel effects, that is, good drain current-voltage characteristics, low body effects and threshold voltage of 1.0 V, high punchthrough and breakdown voltage of 12 V, low subthreshold swing(S.S) values of 105 mV/decade.

• 한국데이터정보과학회:학술대회논문집
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• 2006.04a
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• pp.163-169
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• 2006

This paper deals with the comparison of parameter estimation methods in a 3-parameter Kappa distribution which is sometimes used in flood frequency analysis. The method of moment estimation(MME), L-moment estimation(L-ME), and maximum likelihood estimation(MLE) are applied to estimate three parameters. The performance of these methods are compared by Monte-carlo simulations. Especially for computing MME and L-ME, ike dimensional nonlinear equations are simplied to one dimensional equation which is calculated by the Newton-Raphson iteration under constraint. Based on the criterion of the mean squared error, the L-ME is recommended to use for small sample size $(n\leq100)$ while MLE is good for large sample size.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.850-851
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• 2008

This paper compares and investigates the vibration and noise characteristics through simulations of 12/8 and 6/4 switched reluctance motors (SRMs). The radial force which is the main source of vibration is computed from two-dimensional(2D) transient magnetic finite element analysis (FEA) and compared in both time and frequency domain. At the same output power, the radial force of 6/4 SRM is found to be more than two times as that one of 12/8 SRM. Three-dimensional structural finite-element analysis (3D FEA) is used to study the mechanical characteristics. It can be concluded from static structural analysis that the maximum total deformation could be reduced to 1/26 if the motor is designed with 12/8 structure instead of 6/4. The dominant vibration modes are verified by modal analysis.

• Ocean Systems Engineering
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• v.10 no.3
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• pp.267-287
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• 2020

The dropped objects are identified as one of the top ten causes of fatalities and serious injuries in the oil and gas industry. It is of importance to understand dynamics of dropped objects under water to accurately predict the motion of dropped objects and protect the underwater structures and facilities from being damaged. In this paper, we study non-dimensionalization of two-dimensional (2D) theory for dropped cylindrical objects. Non-dimensionalization helps to reduce the number of free parameters, identify the relative size of effects of force and moments, and gain a deeper insight of the essential nature of dynamics of dropped cylindrical objects under water. The resulting simulations of dimensionless trajectory confirms that drop angle, trailing edge and drag coefficient have the significant effects on dynamics of trajectories and landing location of dropped cylindrical objects under water.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.49-54
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• 2006

The present study conducted a numerical modeling on the diesel SCR (selective catalytic reduction) system using ammonia as a reductant over vanadium-based catalysts $(V_2O_5-WO_3/TiO_2)$. Transient modeling for ammonia adsorption/desorption on the catalyst surface was firstly carried out, and then the SCR reaction was modeled considering for it. In the current catalytic reaction model, we extended the pure chemical kinetic model based on laboratory-scale powdered-phase catalyst experiments to the chemico-physical one applicable to realistic commercial SCR reactors. To simulate multi-dimensional heat and mass transfer phenomena, the SCR reactor was modeled in two dimensional, axisymmetric domain using porous medium approach. Also, since diesel engines operate in transient mode, the present study employed an unsteady model. In addition, throughout simulations using the developed code, effects of space velocity on the DeNOx performance were investigated.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.132-136
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• 2005

It is widely accepted that the reading mechanism of Super-RENS(super-resolution near field structure) and Super-ROM(super-resolution read only memory) is closely related with non-linear temperature dependent material properties such as refractive indices, phase change. Furthermore, the dynamic change of the temperature distribution also an essential part of reading mechanism of Super-RENS/ROM. Therefore, the knowledge of the temperature distribution as a function a time is one of the important keys to reveal the physics of reading mechanism in Super-RENS/ROM. We calculated time-dependent temperature distribution in a 3-dimensional Super-ROM disk structure when moving laser beam is irradiated. With a help of commercial software FEMLAB which employed finite element method, we simulated the temperature distribution of ROM structure whose pit diameter is 120-nm with 50-nm depth. Energy absorption by moving laser irradiation, time variations of heat transfer processes, heat fluxes, heat transfer ratios, and temperature distributions of the complicate 3-dimensional ROM structure have been obtained.