• 제목/요약/키워드: Theoretical Computation

검색결과 198건 처리시간 0.024초

전산해석을 통한 비정상 Mach Reflection Wave Configuration 확인 (CFD CONFIRMATION OF ABNORMAL SHOCK WAVE INTERACTIONS)

  • 후종민;양영록;장유;명노신;조태환
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2008년 추계학술대회논문집
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    • pp.92-96
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    • 2008
  • For the Mach reflection of symmetric shock waves, only the wave configuration of an oMR(DiMR+DiMR) is theoretically admissible. For asymmetric shock waves, an oMR(DiMR+InMR) will be possible if the two slip layers assemble a convergent-divergent stream tube while an oMR(InMR+InMR) is absolutely impossible. In this paper, an overall Mach reflection configuration with double inverse MR patterns is confirmed using the CFD technique. Classical two- and three-shock theories are also applied for the theoretical analysis. In addition, oscillations of shock wave patterns are computed for the interaction of a hypersonic flow and double-wedge-like geometries.

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지중매설관의 특성이 토양 - 공기 열교환기 성능에 미치는 영향 (Effects of Earth-Tube Characteristics on the Soil-Air Heat Exchanger Performances)

  • 김영복
    • Journal of Biosystems Engineering
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    • 제22권4호
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    • pp.459-468
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    • 1997
  • To optimize the design and operation of a soil- air heat exchanger system, the effects of variables characterizing system design and operation on the performance of the system were analyzed by a theoretical model which included the three-dimensional transient heat conduction equation. The solution of the theoretical model was acquired by a computer program that uses Finite Difference Methods and Gauss-Seidel iteration computation, in which the time discretization scheme was an implicit difference appoximation. The computer program was validated first by comparison of the results for different grid sizes. Air outlet temperature, energy gain, and heat exchange efficiency of the system were analyzed based upon the tube diameter, tube length, tube thickness, and tube thermal diffusivity.

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Theoretical Computation of the Capacitance of an Asymmetric Coplanar Waveguide

  • Song, Chan Mi;Kwon, Gina;Lee, Jong Min;Lee, Kang-Yoon;Yang, Youngoo;Hwang, Keum Cheol
    • Journal of Electrical Engineering and Technology
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    • 제13권1호
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    • pp.393-399
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    • 2018
  • An electrostatic boundary-value problem of a dielectric-wedge-backed, double-slotted conducting wedge is investigated to analyze an asymmetric coplanar waveguide with an infinite dielectric thickness using the Mellin transform and a mode-matching method. Our theoretical solution based on eigenfunction expansion and residue calculus is a rigorous and fast-convergent series form. Numerical computations are conducted to evaluate the potential field, capacitance, and characteristic impedance for various structures of the asymmetric coplanar waveguide. The computed results show good agreement with the simulated results.

MARGIN-BASED GENERALIZATION FOR CLASSIFICATIONS WITH INPUT NOISE

  • Choe, Hi Jun;Koh, Hayeong;Lee, Jimin
    • 대한수학회지
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    • 제59권2호
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    • pp.217-233
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    • 2022
  • Although machine learning shows state-of-the-art performance in a variety of fields, it is short a theoretical understanding of how machine learning works. Recently, theoretical approaches are actively being studied, and there are results for one of them, margin and its distribution. In this paper, especially we focused on the role of margin in the perturbations of inputs and parameters. We show a generalization bound for two cases, a linear model for binary classification and neural networks for multi-classification, when the inputs have normal distributed random noises. The additional generalization term caused by random noises is related to margin and exponentially inversely proportional to the noise level for binary classification. And in neural networks, the additional generalization term depends on (input dimension) × (norms of input and weights). For these results, we used the PAC-Bayesian framework. This paper is considering random noises and margin together, and it will be helpful to a better understanding of model sensitivity and the construction of robust generalization.

ON COMPUTATION OF MATRIX LOGARITHM

  • Sherif, Nagwa;Morsy, Ehab
    • Journal of applied mathematics & informatics
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    • 제27권1_2호
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    • pp.105-121
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    • 2009
  • In this paper we will be interested in characterizing and computing matrices $X\;{\in}\;C^{n{\times}n}$ that satisfy $e^X$ = A, that is logarithms of A. The study in this work goes through two lines. The first is concerned with a theoretical study of the solution set, S(A), of $e^X$ = A. Along the second line computational approaches are considered to compute the principal logarithm of A, LogA.

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JACOBI SPECTRAL GALERKIN METHODS FOR VOLTERRA INTEGRAL EQUATIONS WITH WEAKLY SINGULAR KERNEL

  • Yang, Yin
    • 대한수학회보
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    • 제53권1호
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    • pp.247-262
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    • 2016
  • We propose and analyze spectral and pseudo-spectral Jacobi-Galerkin approaches for weakly singular Volterra integral equations (VIEs). We provide a rigorous error analysis for spectral and pseudo-spectral Jacobi-Galerkin methods, which show that the errors of the approximate solution decay exponentially in $L^{\infty}$ norm and weighted $L^2$-norm. The numerical examples are given to illustrate the theoretical results.

High concentration ratio approximation of linear effective properties of materials with cubic inclusions

  • Mejak, George
    • Coupled systems mechanics
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    • 제7권1호
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    • pp.61-77
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    • 2018
  • This paper establish a high concentration ratio approximation of linear elastic properties of materials with periodic microstructure with cubic inclusions. The approximation is derived using first few terms of power series expansion of the solution of the equivalent eigenstrain problem with a homogeneous eigenstrain approximation. Viability of the approximation at high concentration ratios is proved by comparison with a numerical solution of the homogenization problem. To this end some theoretical result of symmetry properties of the homogenization problem are given. Using these results efficient numerical computation on a reduced computational domain is presented.

송전선로의 점퍼선 안전성 향상을 위한 횡진각 계산에 관한 연구 (A Study for Computation of Swaying Angle for Jumper Safety Improvement in the Overhead Line)

  • 안영주;신춘식;변기식
    • 한국안전학회지
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    • 제12권1호
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    • pp.44-50
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    • 1997
  • As jumpers for overhead transmission lines increase In size, it Is necessary to take into the characteristics of jumper swaying space in order to determine jumper reinforcements adequately. From the theory of a structure made of beams, formulas for the sideway swaying of overhead transmission lines due to wind are modeled. And also natural frequency of the vibrated jumper is estimated to check the system resonance. The theoretical results can be led good suggestions to improve the economy and reliability of jumper structure.

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유리기층의 레이저 텍스쳐링에 의한 미소융기의 형성 (Microbump formation during laser texturing of glass substrates)

  • 김동식;오부국
    • 한국레이저가공학회지
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    • 제4권3호
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    • pp.40-44
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    • 2001
  • Microbump formation during CO$_2$ laser texturing of glass substrates is examined in this paper. Experimental results show that different bump shapes (dome-shaped, with a central dimple, and with a peripheral rim) are generated depending on the laser fluence. A theoretical model for the process is suggested based on thermoelastic behavior but limited only to the dome-shaped bump. The dimensions (maximum height and base area) of the bump shows a logarithmic dependence on laser fluence as expected from the theory. Numerical computation reveals that the effect of thermal diffusion is not negligible for relatively long laser pulses.

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유도형 적산전력량계의 토오크측정 기술 (Torque measuring technique of induction watthour meter)

  • 박영태;강정홍;장석명;이성호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1998년도 하계학술대회 논문집 A
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    • pp.290-292
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    • 1998
  • The driving torque acting on a rotatable disk of watthour meter is proportional to the effective power. The aim of this paper is to show how the driving torque on a disk can be measured by a LVDT transducer. This driving torque is obtained by the theoretical computation. To verify the computated result, the LVDT as torque transducer, was used. A comparison is made between computed and measured torques.

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