• Food Science and Biotechnology
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• v.16 no.6
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• pp.954-957
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• 2007

Gelation mechanism of xanthan-carob mixture (X/C) was investigated based on thermorheological behavior. Three X/C ratios (1:3, 1:1, and 3:1) were studied. Small amplitude oscillatory shear tests were performed to measure linear viscoelastic behavior during gelation. Temperature sweep ($-1^{\circ}C/min$) experiments were conducted. Using a non-isothermal kinetic model, activation energy (Ea) during gelation was calculated. At 1% total concentration, the Ea for xanthan fraction (${\phi}_x$)=0.25, 0.5, and 0.75 were 178, 159, and 123 kJ/mol, respectively. However, a discontinuity was observed in the activation energy plots. Based on this, two gelation mechanisms were presumed-association of xanthan and carob molecules and aggregation of polymer strands. The association process is the primary mechanism to form 3-D networks in the initial stage of gelation and the aggregation of polymer strands played a major role in the later stage.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.8
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• pp.1387-1395
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• 1997

Effects of the ambient air temperature and the opening position on the pattern of the clothing ventilation of a thermal manikin wearing an impermeable blouse were investigated by the trace gas method. Under an isothermal condition, the ventilation was governed by diffusion, and the ventilation rate through the wrist-openings was greatly affected by the distance from the openings. Under non-isothermal conditions, however, the ventilation was accelerated by the convection driven by the temperature gradient between the clothing microclimate and the surrounding air; the greater the temperature gradient, the greater the ventilation. Even though it was certainly affected by the ambient air temperature, the ventilation rate was more significantly influenced by the position of openings. The ventilation patterns at the arm and the body were distinctive.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.1
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• pp.11-18
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• 2000

In order to investigate the dehydriding properties of the $Mg_2NiH_x$ formed by hydrogen induced mechanical alloying, we performed isothermal thermogravimetry analysis at 453, 463, 473, 483, 493, 503 and 513K for 1 hours. Dehydrogenation kinetics were dependant strongly on the MA conditions which determine the In other words, kinds of synthesized hydrides phases and the crystal microstructures. The MA condition, 66:1 BCR(balls to chips mass ratio), especially 96h milling time, revealed the hydride phases of nano-/ amorphous state and the dehydriding activation energy of $43.4{\pm}3.6kJ/mole$.

• Journal of The Korean Astronomical Society
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• v.40 no.1
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• pp.29-36
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• 2007

The smoothed particle hydrodynamics (SPH) method is applied to construct the dispersion of fluctuations in quasi-hydrostatic configuration of an isothermal self-gravitating slab. The uncertainty of the implementation is evaluated, and a novel technique (acceleration error) is proposed to weaken this uncertainty. The two-fluid quasi-hydrostatic diffusion of small fluctuations is used to support the importance of the acceleration error. The results show that the uncertainty converges to a few percent by increasing of the SPH particle numbers. Considering the acceleration error weakens the uncertainty, and prohibits the serious dynamical consequences in slow dispersion of fluctuation in the quasi-hydrostatic evolution of the slab.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.108.1-108.1
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• 2011

Turbulence is ubiquitous in astrophysical fluids such as the interstellar medium(ISM) and the intracluster medium(ICM). There are many driving mechanisms which can inject energy into the fluid in variety driving scales, But the plausible driving scale of ISM/ICM turbulence are yet unknown. Therefore, understanding different statistical properties between turbulence with single driving scale and turbulence with double driving scale is required. In this work, we performed 3-dimensional isothermal compressible, magnetohydrodynamic(MHD) turbulence simulations. We drive turbulence in the Fourier space in two ranges, 2

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.462-468
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• 2004

Large eddy simulation(LES) methodology used to model isothermal non-swirling and swirling flows in a model gas turbine combustor. The LES solver was implemented on parallel computer consisting 16 processors. To verify the capability of LES code and characterize swirling flow, the results was compared with that of Reynolds Averaged Navier-Stokes(RANS) using k -$\epsilon$ model as well as experimental data. The results showed that the LES and RANS well predicted the mean velocity field of a non-swirling flow. Specially, the LES showed a very excellent prediction performance for the corner recirculation zone. In swirling flow, comparing with the results obtained by RANS, LES showed a better performance in predicting the mean axial and azimuthal velocities, and the central recirculation zone. Finally, unsteady phenomena of turbulent flow was examined with LES methodology.

• Journal of Magnetics
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• v.18 no.4
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• pp.405-411
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• 2013

The structural, magnetic and magnetocaloric properties of $CoMn_{1-x}Cr_xGe$ (x=0.05-0.125) have been investigated by using electron microscopy, x-ray diffraction, calorimetric and magnetic measurements. In this study, our aim is to justify the magnetocaloric effect by tuning the structural and magnetic transition temperature with Cr doping on CoMnGe pure system. The substitution of Cr for Mn leads to a decrease of both structural and magnetic transition temperatures. However, structural and magnetic transition temperatures do not close to each other. From magnetization measurement, we calculate that isothermal entropy change associated with magnetic transition can be as high as 3.82 J $kg^{-1}K^{-1}$ at 302 K in a field of 7 T. Meanwhile, structural phase transition contribution to isothermal entropy change is calculated as 5.85 J $kg^{-1}K^{-1}$ at 322 K for 7 T.

• Nuclear Engineering and Technology
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• v.33 no.1
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• pp.62-72
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• 2001

The one-dimensional finite element program was developed to analyze the coupled behavior of heat, moisture, and air transfer in unsaturated porous media. By using this program, the simulation results were compared with those from the laboratory infiltration tests under isothermal condition and temperature gradient condition, respectively. The discrepancy of water uptake was found in the upper region of a bentonite sample under isothermal condition between numerical simulation and laboratory experiment. This indicated that air pressure was built up in the bentonite sample which could retard the infiltration velocity of liquid. In order to consider the swelling phenomena of compacted bentonite which cause the discrepancy of the distribution of water content and temperature, swelling and shrinkage factors were incorporated into the finite element formulation. It was found that these factors could be effective to represent the moisture diffusivity and unsaturated hydraulic conductivity due to volume change of bentonite sample.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.4
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• pp.268-278
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• 1990

Hydrodynamic stability equations are formulated for natural convection flows adjacent to a heated or cooled, inclined, isothermal surface in pure water at $4^{\circ}C$, where the density variation with temperature becomes nonlinear. The resulting stability equations, when reduced to ordinary differential equations by a similarity transformation, constitute a two-point boundary-value problem, which was solved numerically. It is found from the obtained stability results that the neutral stability curves are systematically shifted to have lower critical Grashof numbers, as the inclination angle of upward-facing plate increases. Also, the nose of the neutral stability curve becomes blunter as the angle increases. It implies that the greater the inclination of the upward-facing plate, the more susceptible of the flow to instability for the wide range of disturbance wave number and frequency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.1
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• pp.64-72
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• 1989

Laminar natural convection heat transfer from a horizontal heat exchanger tube with one infinitely long vertical plate fin has been studied by a finite-difference numerical procedure. In predicting convective heat transfer from a circular tube, the thermal boundary condition at solid fluid interface is usually assumed to be isothermal. However, in reality, the thermal boundary condition is not isothermal, and the tube has the thickness and the conductivity. So the temperature at the interface is not known a priori to the calculation. This problem has the conjugate phenomena which occur between the tube conduction and external natural convection, and between the fin conduction and external natural convection. Numerical results are obtained to determine the effects of the conductivity of solid wall and the thickness of tube wall on heat transfer. It is found that the conduction causes significant influence on the natural convection heat transfer at low K and high ${\delta}$.