• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.2
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• pp.260-264
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• 1987

We examine the effect of junction depth on the charge density solving numerically the general form of Poisson's equation for Gaussian $n^{+}$-p junctions. We also present an analytical model for the charge diopole due to the variation of the dielectric constant with doping.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.65-68
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• 2008

본 논문은 영한 과학기술 논문 자동번역 시스템을 대상으로 이루어진 수동 평가와 자동 평가 사이의 상관 관계를 밝힘으로써 수동 평가와 자동 평가 중에 한쪽의 방법에 의해서 평가가 이루어지더라도 다른 쪽의 수치를 파악할 수 있도록 하는데 목표가 있다. 본 논문에서 수행한 수동 평가는 5 인의 전문 번역가가 5 회에 걸쳐 평가한 결과이며, 자동 평가는 영어 원문 1,000 문장에 대한 8 인이 번역한 8,000 문장의 정답문(References)과 자동번역 결과를 어절 단위와 형태소 단위로 N-gram 비교를 통해 평가된 결과이다. 본 논문에서 도출된 식은 사용하는 평가 집합과 대상 번역 시스템 별로 자동 평가와 수동 평가 간의 상관 계수를 만들어내고 수동 번역률을 구하는 식을 동일하게 적용한다면 시스템의 자동 평가 결과로부터 성능을 직관적으로 해석하는데 상당히 도움이 될 것이다.

• Nuclear Engineering and Technology
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• v.24 no.3
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• pp.319-328
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• 1992

The Galerkin formulation of the finite element method is applied to the integral law of the first-order form of the one-group neutron transport equation in one-dimensional spherical geometry. Piecewise linear or quadratic Lagrange polynomials are utilized in the integral law for the angular flux to establish a set of linear algebraic equations. Numerical analyses are performed for the scalar flux distribution in a heterogeneous sphere as well as for the criticality problem in a uniform sphere. For the criticality problems in the uniform sphere, the results of the finite element method, with the use of continuous finite elements in space and angle, are compared with the exact solutions. In the heterogeneous problem, the scalar flux distribution obtained by using discontinuous angular and spatical finite elements is in good agreement with that from the ANISN code calculation.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.3
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• pp.345-351
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• 2024

The unitized regenerative fuel cell (URFC) is a method that can reduce costs and increase system simplification by unitizing a fuel cell system and a water electrolysis system. The spray method is suitable as the membrane electrode assembly (MEA) manufacturing method for URFC because it is easy to control the amount of catalyst, the size of the system is small, and economical manufacturing is possible. In this study, a numerical analysis of the effect of solution concentration on the spray method was performed to use it as basic data for the spray method to be used in MEA manufacturing. As result, as the Nafion solution concentration decreases it was found that the spray speed and the mass flow rate and the discrete phase model concentration increases and the spray range widens.

• Tunnel and Underground Space
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• v.14 no.6 s.53
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• pp.440-449
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• 2004

Rock mass includes natural discontinuities such as joints and faults during its formation. Discontinuities are also referred as planes of weakness because of their weak mechanical characteristics. In the design of underground structures, it is necessary to consider the properties of discontinuities to insure the stability. During the excavation of a tunnel, these discontinuities have to be identified as early as possible so that proper change in excavation method or support design can be made accordingly. The excavation of the tunnel in a stable rock mass causes a 3-dimensional arching effect around the excavation face. It was revealed by previous studies that the existence of a weak zone or a fault zone ahead of tunnel foe induces a typical displacement tendency of convergence. For better understanding of the meaning of influence/trend lines of various displacement components, three-dimensional numerical analyses were conducted while varying deformation moduli, thicknesses and orientations of discontinuities. Numerical results showed that the changes in influence/trend lines of various displacement components were very similar to those by measurements. The discrepancies from the expected values were dependent on the physical properties, thicknesses and orientations of discontinuities.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.3
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• pp.61-69
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• 2015

This study presents a probabilistic knowledge discovery method to interpret heart rate variability (HRV) based on time and frequency domain indexes, extracted using discrete wavelet transform. The knowledge induction algorithm was composed of two phases: rule generation and rule estimation. Firstly, a rule generation converts numerical attributes to intervals using ROC curve analysis and constructs a reduced ruleset by comparing consistency degree between attribute-value pairs with different decision values. Then, we estimated three measures such as rule support, confidence, and coverage to a probabilistic interpretation for each rule. To show the effectiveness of proposed model, we evaluated the statistical discriminant power of five rules (3 for atrial fibrillation, 1 for normal sinus rhythm, and 1 for both atrial fibrillation and normal sinus rhythm) generated using a data (n=58) collected from 1 channel wireless holter electrocardiogram (ECG), i.e., HeartCall$^{(R)}$, U-Heart Inc. The experimental result showed the performance of approximately 0.93 (93%) in terms of accuracy, sensitivity, specificity, and AUC measures, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.10
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• pp.538-550
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• 2017

In a PWR (Pressurized Water Reactor), the appropriate heat removal from the surface of fuel rod bundle is important for ensuring thermal margins and safety. Although many CFD (Computational Fluid Dynamics) software have been used to predict complex flows inside fuel assemblies with mixing vanes, there is no domestic regulatory guideline for the comprehensive evaluation of CFD software. Therefore, from the nuclear regulatory perspective, it is necessary to perform the systematic assessment and prepare the domestic regulatory guideline for checking whether valid CFD software is used for nuclear safety problems. In this study, to provide systematic evaluation and guidance on the applicability of CFD software to the domestic nuclear safety area, the results of the sensitivity analysis for the effect of the discretization scheme accuracy for the convection terms and turbulence models, which are main factors that contribute to the uncertainty in the calculation of the nuclear safety problems, on the prediction performance for the turbulent flow distribution inside the fuel assembly with split-type mixing vanes were explained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.5
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• pp.186-194
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• 2016

As a turbulence-enhancing device, a mixing vane installed at a spacer grid of the fuel assembly plays a role in improving the convective heat transfer by generating either swirl flow in the subchannels or cross flow between fuel rod gaps. Therefore, both configuration and arrangement pattern of a mixing vane are important factors that determine the performance of a mixing vane. In this study, in order to examine the flow distribution features inside $5{\times}5$ fuel assembly with swirl-type mixing vanes used in benchmark calculation of OECD/NEA, simulations were conducted with commercial CFD software ANSYS CFX R.14. Predicted results were compared to data measured from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. In addition, the effect of swirl-type mixing vanes on flow pattern inside the fuel assembly was described.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.365-372
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• 2016

Using the computational fluid dynamics (CFD) technique, we simulated the fluid flow in a Taylor reactor considering the aggregation and breakage of particles. We calculated the population balance equation (PBE) to determine the particle-size distribution by implementing the quadrature method-of-moment (QMOM). It was used that six moments for an initial moments, the sum of Brownian kernel and turbulent kernel for aggregation kernel, and power-law kernel for breakage kernel. We predicted the final mean particle size when the particle had various initial volume fraction values. The result showed that the mean particle size and initial growth rate increased as the initial volume fraction of the particle increased.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1711-1721
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• 1992

A nonlinear dissipative dynamical system can often have multiple attractors. In this case, it is important to study the global behavior of the system by determining the global domain of attraction of each attractor. In this paper we study the global behavior of a forced beam with two mode interaction. The governing equation of motion is reduced to two second-order nonlinear nonautonomous ordinary differential equations. When .omega. /=3.omega.$_{1}$ and .ohm.=.omega $_{1}$, the system can have two asymptotically stable steady-state periodic solutions, where .omega./ sub 1/, .omega.$_{2}$ and .ohm. denote natural frequencies of the first and second modes and the excitation frequency, respectively. Both solutions have the same period as the excitation period. Therefore each of them shows up as a period-1 solution in Poincare map. We show how interpolated mapping method can be used to determine the two four-dimensional domains of attraction of the two solutions in a very effective way. The results are compared with the ones obtained by direct numerical integration.