• Journal of the Korean Mathematical Society
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• 제56권6호
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• pp.1641-1654
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• 2019

In this paper we study the quasi-neutral limit of the compressible magnetohydrodynamic flows in the periodic domain ${\mathbb{T}}^3$ with the well-prepared initial data. We prove that the weak solution of the compressible magnetohydrodynamic flows governed by the Poisson equation converges to the strong solution of the compressible flow of magnetohydrodynamic flows as long as the latter exists.

• Communications of the Korean Mathematical Society
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• 제26권4호
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• pp.695-708
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• 2011

Based on the multiple-time-scale (MTS) method, a general formula has been presented for solving an n-th, n = 2, 3, ${\ldots}$, order ordinary differential equation with strong linear damping forces. Like the solution of the unified Krylov-Bogoliubov-Mitropolskii (KBM) method or the general Struble's method, the new solution covers the un-damped, under-damped and over-damped cases. The solutions are identical to those obtained by the unified KBM method and the general Struble's method. The technique is a new form of the classical MTS method. The formulation as well as the determination of the solution from the derived formula is very simple. The method is illustrated by several examples. The general MTS solution reduces to its classical form when the real parts of eigen-values of the unperturbed equation vanish.

• Journal of Energy Engineering
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• 제10권4호
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• pp.357-362
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• 2001

A bench type ammonia-water absorber heat exchange cycle was tested by varying the system charging concentration, refrigerating valve opening and weak solution flow rate. It was observed that the cooling capacity was increased as the system charging concentration was increased. Optimum system charging concentration was found for the coolong capacity of the system. The opening rate of refrigerant expansion valve had a direct influence on the refrigerant sub-cooling at the condenser outlet. Optimum sub-cooling was found to be 0~4$^{\circ}C$. As the weak solution flow rate increased the concentration of strong solution and the evaporating pressure decreased. There existed a optimum weak solution flow rate which maximized the cooling capacity and COP.

• Korean Journal of Agricultural Science
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• 제3권1호
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• pp.105-119
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• 1976

Sucrose, glucose, starches hydrolyzates and raw starchy materials hydrolyzates were caramelized using various catalysis and the caramel products were analysed, in order to carry out the basic research for the replacement of caramel coloring. The results obtained were summarized as follows. 1. The caramel which was manufactured by sucrose syrup being pH 3.5 adjusted by sulfuric acid showed strong color intensity and hue as well as good stability in the solutions of table salt, tannin and alcohol. 2. The product caramelized from sucrose syrup being pH 9.5 adjusted by sodium carbonate showed very strong color intensity and black color component, and was quite stable in alcohol solution but not in table salt and tannin solutions. 3. The caramel products made from sucrose syrup using ammonium salts of strong acid like $NH_4Cl$ and $(NH_4)_2SO_4$ as catalyst showed strong color intensity and black color component but hazy apparence in solution of table salt, tannin and alcohol. 4. The product caramelized from glucose syrup being pH 9.5 adjusted by sodium carbonate indicated strong color intensity but weak red color component and was transparent in solution of table salt and alcohol but hazy in tannin solution. 5. In glucose caramel using $NH_4Cl$, $(NH_4)_2SO_4$, $(NH_4)_2CO_3$ and $(NH_4)_2SO_3$ as catalyst, $NH_4Cl$ plot was very weak in color intensity and insufficient in red color component but stable in solution of table salt, tannin and alcohol. In the case of $(NH_4)_2CO_3$, $(NH_4)_2SO_4$ and $(NH_4)_2SO_3$ plots, all products were strong in color intensity but little insufficient in red color component. On the stability in solutions, $(NH_4)_2SO_3$ plot was stable in two solutions expect tannin solution, $(NH_4)_2CO_3$ plot was only stable in alcohol solution and $(NH_4)_2SO_3$ plot was only stable in table salt solution. 6. When the acid hydrolyzed starch syrups without neutralization were caramelized using $(NH_4)_2SO_4$ as catalyst, the potato starch hydrolyzate caramel showed higher in color intensity being similar to its of glucose caramel than sweet potato starch hydrolyzate caramel and corn starch hydrolyzate caramel. 7. Dried sweet potato powder, dried acorns powders, the acorns (from Q. serrata THUNB and Q. acutissima CARR.) powders extracted with water for 7 days and with 50% alcohol solution for 24 hrs were hydrolyzed by sulfuric acid in autoclave at $3.5kg/cm^2$ as pressure for 60 mins, and were caramelized using $(NH_4)_2SO_4$ as catalyst. It was supposed that all of those products were poor quality on color and stability in solutions at the viewpoint of food coloring matter.

• Journal of the Korean Mathematical Society
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• 제45권3호
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• pp.645-681
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• 2008

The Navier-Stokes system for heat-conducting incompressible fluids is studied in a domain ${\Omega}{\subset}R^3$. The viscosity, heat conduction coefficients and specific heat at constant volume are allowed to depend smoothly on density and temperature. We prove local existence of the unique strong solution, provided the initial data satisfy a natural compatibility condition. For the strong regularity, we do not assume the positivity of initial density; it may vanish in an open subset (vacuum) of ${\Omega}$ or decay at infinity when ${\Omega}$ is unbounded.

• Kyungpook Mathematical Journal
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• 제64권1호
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• pp.69-94
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• 2024

In this paper, we introduce an inertial self-adaptive projection method using Bregman distance techniques for solving pseudomonotone equilibrium problems in reflexive Banach spaces. The algorithm requires only one projection onto the feasible set without any Lipschitz-like condition on the bifunction. Using this method, a strong convergence theorem is proved under some mild conditions. Furthermore, we include numerical experiments to illustrate the behaviour of the new algorithm with respect to the Bregman function and other algorithms in the literature.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1303-1313
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• 2002

Effects of the reduced frequency of upstream wake on downstream unsteady boundary layer flow were simulated by using a Wavier-Stokes code. The Wavier-Stokes code is based on an unstructured finite volume method and uses a low Reynolds number turbulence model to close the momentum equations. The geometry used in this paper is the MIT flapping foil experimental set-up and the reduced frequency of the upstream wake is varied in the range of 0.91 to 10.86 to study its effect on the unsteady boundary layer flow. Numerical solutions show that they can be divided into two categories. One is so called the low frequency solution, and behaves quite similar to a Stokes layer. Its characteristics is found to be quite similar to those due to either a temporal or spatial wave. The low frequency solutions are observed clearly when the reduced frequency is smaller than 3.26. The other one is the high frequency solution. It is observed for the reduced frequency larger than 7.24. It shows a sudden shift of the phase angle of the unsteady velocity around the edge of the boundary layer. The shift of phase angle is about 180 degree, and leads to separation of the boundary layer flow from corresponding outer flow. The high frequency solution shows the characteristics of a temporal wave whose wave length is half of the upstream frequency. This characteristics of the high frequency solution is found to be caused by the strong interaction between unsteady vortices. This strong interaction also leads to destroy of the upstream wake strips inside the viscous sublayer as well as the buffer layer.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3443-3447
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• 2011

The spectroscopic behavior of catechin (5,7,3',4'-tetrahydroxyflavan-3-ol), has been studied in the presence and the absence of air using UV-vis absorption spectrophotometry and fluorescence spectroscopy. The UV-vis absorption spectrum of catechin shows a very sharp and strong absorption maximum peak at 275 nm in deaerated water. New absorption maximum peaks appeared in aerated water, as well as in basic aqueous solution, caused by the oxidation of catechin. The absorbances in the UV-vis absorption spectrum of catechin decreased when the solution was left in the dark for a long time. The fluorescence emission spectrum of catechin after a long time period differs markedly from that in freshly prepared solution; the fluorescence maxia shifted as time passes after adding catechin to the solutions. When the deaerated basic catechin solutions were left in the dark for a long time, their fluorescence quantum yields were found to be nearly zero. This suggests that the oxidized catechin molecules were seen to have slowly undergone successive chemical reactions in basic buffer solution.

• Bulletin of the Korean Mathematical Society
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• 제35권4호
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• pp.837-845
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• 1998

In this work, we consider Euler approxiamtion for one-dimensional jump-diffusion processes under Yamada-Watanabe type conditions on the coefficients which turns out to converge to the strong solution in uniform $L^1$-sense.

• East Asian mathematical journal
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• 제30권5호
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• pp.609-616
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• 2014

In this paper we consider hyperbolic equations related to the p-Laplacian with a nonsmooth kernel. By exploiting a suitable implicit time-discretization technique we obtain the existence of global strong solution.