• Journal of Computational Design and Engineering
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• 제3권4호
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• pp.349-362
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• 2016

The numerical solutions of unsteady hydromagnetic natural convection Couette flow of a viscous, incompressible and electrically conducting fluid between the two vertical parallel plates in the presence of thermal radiation, thermal diffusion and diffusion thermo are obtained here. The fundamental dimensionless governing coupled linear partial differential equations for impulsive movement and uniformly accelerated movement of the plate were solved by an efficient Finite Element Method. Computations were performed for a wide range of the governing flow parameters, viz., Thermal diffusion (Soret) and Diffusion thermo (Dufour) parameters, Magnetic field parameter, Prandtl number, Thermal radiation and Schmidt number. The effects of these flow parameters on the velocity (u), temperature (${\theta}$) and Concentration (${\phi}$) are shown graphically. Also the effects of these pertinent parameters on the skin-friction, the rate of heat and mass transfer are obtained and discussed numerically through tabular forms. These are in good agreement with earlier reported studies. Analysis indicates that the fluid velocity is an increasing function of Grashof numbers for heat and mass transfer, Soret and Dufour numbers whereas the Magnetic parameter, Thermal radiation parameter, Prandtl number and Schmidt number lead to reduction of the velocity profiles. Also, it is noticed that the rate of heat transfer coefficient and temperature profiles increase with decrease in the thermal radiation parameter and Prandtl number, whereas the reverse effect is observed with increase of Dufour number. Further, the concentration profiles increase with increase in the Soret number whereas reverse effect is seen by increasing the values of the Schmidt number.

• Journal of applied mathematics & informatics
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• 제42권3호
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• pp.607-623
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• 2024

This article studies the effects of heat generation/absorption and thermal radiation on the unsteady magnetohydrodynamic (MHD) Casson fluid flow past a vertical plate through rotating porous medium with constant temperature and mass diffusion. It is assumed that the plate temperature and concentration level are raised uniformly. For finding the exact solution, a set of non-dimensional partial differential equations is solved analytically using the Laplace transform technique. The influence of various non-dimensional parameters on the velocity are discussed, including the effects of the magnetic parameter M, heat generation/absorption Q, thermal radiation parameter R, Prandtl number Pr, Schmidt number Sc, permeability of porous medium parameter, Casson fluid parameter γ, on velocity, temperature, and concentration profiles, which are discussed through several figures. It is found that velocity, temperature, and concentration profiles in the case of heat generation parameter Q, Casson fluid parameter γ, thermal Grashof number Gr, mass Grashof number Gc, Permeability Porous medium parameter K, and time t have retarding effects. It is also seen that the magnetic field M, Thermal Radiation parameter R, Prandtl field Pr, Schmidt number Sc have reverse effects on it.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.257-262
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• 2001

The objective of this study is to compare compressive strength and rebound number of Schmidt hammer of concrete using basalt aggregate to that using granite aggregate. And is to provide the reference data on the standardization of nondestructive test of concrete. According to test results, compressive strength of concrete using basalt aggregate is highly estimated under the same rebound number compared to that using granite aggregate about 5~15%. It is urgently that newly suggested estimation formula of compressive strength using basalt aggregate must be prescribed because estimation formula of compressive strength of concrete using basalt aggregates overestimates the strength compared to that using granite aggregate.

• 대한기계학회논문집B
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• 제29권7호
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• pp.846-853
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• 2005

In this paper, mass transfer in turbulent flow around a rotating circular cylinder is investigated by Direct Numerical Simulation for Schmidt numbers Sc=1 and 1670. Correlation between Sherwood and Reynolds number predicted agrees well with other experimental results over both Sc. Reynolds analogy identified at Sc=1 definitely causes a strong correlation between concentration fluctuation and streamwise velocity. For Sc=1670, it is found that positive small values of concentration fluctuations are observed more frequently than the case of Sc=1 particularly out of the range of Nernst diffusion layer in the viscous sub-layer. This fact is fully confirmed by detailed statistical study using a probability density function of concentration fluctuations.

• Communications for Statistical Applications and Methods
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• 제30권1호
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• pp.49-63
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• 2023

A lot of studies on the summary measures of predictive strength of categorical response models consider the likelihood ratio index (LRI), also known as the McFadden-R², a better option than many other measures. We propose a simple modification of the LRI that adjusts for the effect of the number of response categories on the measure and that also rescales its values, mimicking an underlying latent measure. The modified measure is applicable to both binary and ordinal response models fitted by maximum likelihood. Results from simulation studies and a real data example on the olfactory perception of boar taint show that the proposed measure outperforms most of the widely used goodness-of-fit measures for binary and ordinal models. The proposed R² interestingly proves quite invariant to an increasing number of response categories of an ordinal model.

• 한국연소학회지
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• 제20권3호
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• pp.1-7
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• 2015

The laminar lifted jet flames for methane diluted with helium and nitrogen in co-flow air have been investigated experimentally. Such jet flames could be lifted in both buoyancy-dominated and jet momentum dominated regimes (even at nozzle exit velocities much higher than stoichiometric laminar flame speed) despite the Schmidt number less than unity. Chemiluminescence intensities of $OH^*$ radical (good indicators of heat release rate) and the radius of curvature for tri-brachial flame were measured using an intensified charge coupled device (ICCD) camera and digital video camera at various conditions. It was shown that, an increase in $OH^*$ concentration causes increase of edge flame speed via enhanced chemical reaction in buoyancy dominated regime. In jet momentum dominated regime, an increase in radius of curvature in addition to the increased $OH^*$ concentration stabilizes such lifted flames. Stabilization of such lifted flames is discussed based on the stabilization mechanism.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.83-86
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• 2015

The Laminar lifted methane jet flames diluted with helium and nitrogen in co-flow air have been investigated experimentally. The chemiluminescence intensities of $OH^{\ast}$ and $CH_2O^{\ast}$ radicals and the radius of curvature for tri-brachial flame were measured using an intensified charge coupled device (ICCD) camera, monochromator and digital video camera. The product of $OH^{\ast}$ and $CH_2O^{\ast}$ is used as a excellent proxy of heat release rate. These methane jet flames could be lifted in buoyancy and jet dominated regimes despite the Schmidt number less than unity. Lifted flames were stabilized due to buoyancy induced convection in buoyancy-dominated regime. It was confirmed that increased $OH^{\ast}$ and $CH_2O^{\ast}$ concentration caused an increase of edge flame speed via enhanced chemical reaction in buoyancy dominated regime. In jet momentum dominated regime lifted flames were observed even for nozzle exit velocities much higher than stoichiometric laminar flame speed. An increase in radius of curvature in addition to the increased $OH^{\ast}$ and $CH_2O^{\ast}$ concentration stabilizes such lifted flames.

• 천문학회보
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• 제46권1호
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• pp.32.3-33
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• 2021

We present H I gas kinematics and star formation activities of NGC 6822, a dwarf galaxy located in the Local Volume at a distance of ~ 490 kpc. We perform profile decomposition of the line-of-sight velocity profiles of the high-resolution (42.4" × 12" spatial; 1.6 km/s spectral) H I data cube taken with the Australia Telescope Compact Array (ATCA). For this, we use a new tool, the so-called BAYGAUD (BAYesian GAUssian Decompositor) which is based on Bayesian Markov Chain Monte Carlo (MCMC) techniques, allowing us to decompose a line-of-sight velocity profile into an optimal number of Gaussian components in a quantitative manner. We classify the decomposed H I gas components of NGC 6822 into bulk-narrow, bulk-broad, and non_bulk with respect to their velocity and velocity dispersion. We correlate their gas surface densities with the surface star formation rates derived using both GALEX far-ultraviolet and WISE 22 micron data to examine the impact of gas turbulence caused by stellar feedback on the Kennicutt-Schmidt (K-S) law. The bulk-narrow component that resides within r25 is likely to follow the linear extension of the Kennicutt-Schmidt (K-S) law for molecular hydrogen (H2) at the low gas surface density regime where H I is not saturated.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.17-20
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• 2003

Separation of MEK(methylethylketone) was carried out experimentally by a flat membrane contactor using a variety of extracting organic compounds. A correlation equation of Sherwood number was determined in terms of Reynolds number and Schmidt number for the flat membrane contactor system. This correlation equation was applied to get theoretically the overall mass transfer coefficient of MEK: it was compared to the experimental one. It was found that they are in good agreement.

• 콘크리트학회논문집
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• 제16권3호
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• pp.327-334
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• 2004

본 연구에서는 초기재령에서 고강도콘크리트의 압축강도 발현 특성 검토 및 해석 그리고 콘크리트와 거푸집간의 부착강도 특성을 분석하며, P형 슈미트해머를 이용한 반발도와 압축강도간의 상관관계를 검토하므로서 실무의 고강도콘크리트 측면 거푸집 탈형과 연관한 관련규정의 적합성을 재검토하고, 아울러 거푸집제거와 연관한 효율적인 품질관리 방법에 대하여 제안하고자 한다. 연구결과에 따르면, W/B가 증가할수록 응결시간은 감소하는 것으로 나타났으며, 본 연구의 범위에서 로지스틱 모델에 의한 강도증진 해석 결과 압축강도 8MPa를 발휘하는 시간과 적산온도는 17${\~}$20시간, $21{\~}25^{\circ}D{\cdot}D$ 정도로 나타났다. 거푸집과 콘크리트의 부착강도는 종결시점에서 가장 크게 나타났으며 그 이후에는 감소함을 보였고, 거푸집에 부착되어 박리되는 콘크리트의 양은 응결이전에 크게 나타났으며, 그 이후에는 점차적으로 감소하는 경향을 보였다. P형 슈미트해머에 의한 반발도 실험결과 압축강도 발현시점보다 약 2${\~}$3시간 정도 빠르게 측정할 수 있으며, 반발도가 32 이상이면 측면 거푸집을 탈형 할 수 있는 시기로 품질관리가 가능할 것으로 판단되었다.