• 한국전산유체공학회지
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• 제8권3호
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• pp.50-55
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• 2003

Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In the present work, the accuracy of a Fractional step method, which is widely used in LES simulation, has been increased to the fourth-order accurate compact Pade discretization. To validate the present code, the flow-field past a cylinder was simulated and compared with experiment. A good agreement with experiment was achieved.

• 품질경영학회지
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• 제38권1호
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• pp.42-51
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• 2010

For the fractional factorial designs, the resolution-IV designs can be used when we want to estimate the main effects and to investigate the structure of the non-negligible two-factor interaction effects, when the three-factor and higher order interaction effects are all negligible. However we need to add the additional treatment combinations in order to identify the influential interactions for the resolution-IV fractional factorial designs. In this paper we investigate the statistical structure for 3-level resolution-IV designs constructed by fold-over scheme and introduce a method for analyzing the influential two-factor interactions.

• 대한수학회지
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• 제51권1호
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• pp.203-224
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• 2014

We propose and analyze a spectral Jacobi-collocation approximation for fractional order integro-differential equations of Fredholm-Volterra type. The fractional derivative is described in the Caputo sense. We provide a rigorous error analysis for the collection method, which shows 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.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.152-157
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• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권3호
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• pp.313-320
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• 2013

The fractional slot windings are widely used in rotating machine in order to increase the flexibility of design and improve the voltage waveform. However, the MMF wave of fractional-slot windings are found to contain unique harmonic component, which are designated as even order space flux harmonics, fractional number flux harmonics, or both. They may cause stray loss and stator core vibration. This paper proposes new winding methods "novel interspersed windings" and "expanded group windings" to reduce these harmonics. The advantages of two proposed windings are verified by using numerical analysis and measurement test of winding model.

• Geomechanics and Engineering
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• 제19권4호
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• pp.295-305
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• 2019

The present paper is concerned with the investigation of disturbances in orthotropic thermoelastic medium by using fractional order heat conduction equation with three phase lags due to thermomechanical sources. Laplace and Fourier transform techniques are used to solve the problem. The expressions for displacement components, stress components and temperature change are derived in transformed domain and further in physical domain using numerical inversion techniques. The effect of fractional parameter based on its conductivity i.e., ($0<{\alpha}<1$ for weak, ${\alpha}=1$ for normal, $1<{\alpha}{\leq}2$ for strong conductivity) is depicted graphically on various components.

• Steel and Composite Structures
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• 제42권6호
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• pp.723-732
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• 2022

The present research is concerned to study the effect of fractional parameter and rotation on the propagation of Rayleigh waves in an orthotropic magneto-thermoelastic media with three-phase-lags in the context of fractional order theory of generalized thermoelasticity with combined effect of rotation and hall current. The secular equations of Rayleigh waves are derived by using the appropriate boundary conditions. The wave properties such as phase velocity, attenuation coefficient are computed numerically and the numerical simulated results are presented through graphs to show the effect on all the components. Some special cases are also discussed in the present investigation.

• Coupled systems mechanics
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• 제12권2호
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• pp.103-125
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• 2023

The present research is focused on the study of plane harmonic waves in a two-dimensional orthotropic magneto-thermoelastic media with fractional order theory of generalized thermoelasticity in the light of two-temperature and rotation due to time harmonic sources. Here, we studied three types of waves namely quasi-longitudinal (QL), quasi-transverse (QTS) and quasi thermal (QT) waves. The variations in the wave properties such as phase velocity, attenuation coefficient and specific loss have been noticed with respect to frequency for the reflected waves. Further the value of amplitude ratios, energy ratios and penetration depth are computed numerically with respect to angle of incidence. The numerical simulated results are presented graphically to show the effect of fractional parameter based on its conductivity (0<α<1 for weak, α=1 for normal, 1<α≤2 for strong conductivity) on all the components.

• 전기전자학회논문지
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• 제3권1호
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• pp.39-49
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• 1999

This paper describes a 1 GHz, low-phase-noise CMOS fractional-N frequency synthesizer with an integrated LC VCO. The proposed frequency synthesizer, which uses a high-order delta-sigma modulator to suppress the fractional spurious tones at all multiples of the fractional frequency resolution offset, has 64 programmable frequency channels with frequency resolution of $f_ref/64$. The measured phase noise is as low as -110 dBc/Hz at a 200 KHz offset frequency from a carrier frequency of 980 MHz. The reference sideband spurs are -73.5 dBc. The prototype is implemented in a $0.5{\mu}m$ CMOS process with triple metal layers. The active chip area is about $4mm^2$ and the prototype consumes 43 mW, including the VCO buffer power consumption, from a 3.3 V supply voltage.

• 대한수학회지
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• 제53권4호
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• pp.929-967
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• 2016

Let p(t, x) be the fundamental solution to the problem $${\partial}^{\alpha}_tu=-(-{\Delta})^{\beta}u,\;{\alpha}{\in}(0,2),\;{\beta}{\in}(0,{\infty})$$. If ${\alpha},{\beta}{\in}(0,1)$, then the kernel p(t, x) becomes the transition density of a Levy process delayed by an inverse subordinator. In this paper we provide the asymptotic behaviors and sharp upper bounds of p(t, x) and its space and time fractional derivatives $$D^n_x(-{\Delta}_x)^{\gamma}D^{\sigma}_tI^{\delta}_tp(t,x),\;{\forall}n{\in}{\mathbb{Z}}_+,\;{\gamma}{\in}[0,{\beta}],\;{\sigma},{\delta}{\in}[0,{\infty})$$, where $D^n_x$ x is a partial derivative of order n with respect to x, $(-{\Delta}_x)^{\gamma}$ is a fractional Laplace operator and $D^{\sigma}_t$ and $I^{\delta}_t$ are Riemann-Liouville fractional derivative and integral respectively.