• Journal of Pharmaceutical Investigation
• /
• v.2 no.2
• /
• pp.5-17
• /
• 1972

It was reported that cyclodextrin has a distinctive ability to form inclusion compound with a wide variety of compounds. The authors studied the stability of acetylsalicylic acid in cyclodextrin solution. From the results of this experiment, the decomposition of Aspirin in cyclodextrin solution was progressed according to the pseudofirt order reaction and its degradation rate constant was decreased and the thermodynamic activation energy of the degradation of aspirin was accetrated with the increase of cyclodextrin Conclusively, it was considered that cyclodextrin increased the stability of aspirin in aqueous solution by its inclusion compound formation.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.8
• /
• pp.715-719
• /
• 1996

Thin films of polyaniline (PANI) salts were in situ deposited on a Pt plate during either chemical polymerization or electrochemical polymerization. The oxidation states of the salt films were controlled by the applied DC potential. AC impedance of the Pt/PANI electrode were measured in monomer-free 1 N HCl solution in order to investigate the electrodic properties of the films at the following applied DC potentials: 0, 0.45 and 0.75 V vs. SCE. Very small differences in film conductivity according to its oxidation state were observed by analysis of the impedance spectra, the reasons of which are complicated by enriched water content in the film and possible decrease in the film thickness during the measurements. The electrochemical activity of the film/solution interface varied with its oxidation state. Stability of the film in 1 N HCl solution was also evaluated by impedance and cyclic voltammetry measurements.

• Bulletin of the Korean Chemical Society
• /
• v.4 no.5
• /
• pp.231-234
• /
• 1983

The stability constant for the complex of $UO_2^{2+}$ with a macrocyclic aminoether ligand, 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane, has determined in aqueous solution. The conductivity and pH metric measurements suggest that the ligand forms a stable 1:1 complex with $UO_2^{2+}$ ion, and the complex is an ionic form, $UO_2L^{2+}$, in aqueous solution. The fact that the ligand does not form a complex with lanthanides, such as $Ce^{3+}$, $Sm^{3+}$, and $Nd^{3+}$ ions, in aqueous solution suggests a possibility of separation of the lanthanide elements from uranium matrix using the macrocyclic aminoether ligand.

• Journal of the Korean Mathematical Society
• /
• v.42 no.5
• /
• pp.1071-1086
• /
• 2005

In this paper, we introduce a discrete time to the model to describe the time between infection of a CD4$^{+}$ T-cells, and the emission of viral particles on a cellular level. We study the effect of the time delay on the stability of the endemically infected equilibrium, criteria are given to ensure that the infected equilibrium is asymptotically stable for all delay. We also obtain the condition for existence of an orbitally asymptotically stable periodic solution.

• Journal of Korean Institute of Industrial Engineers
• /
• v.25 no.3
• /
• pp.290-297
• /
• 1999

In interior point methods for linear programming, we must solve a linear system with a symmetric positive definite matrix at every iteration, and Cholesky factorization is generally used to solve it. Therefore, if Cholesky factorization is not done successfully, many iterations are needed to find the optimal solution or we can not find it. We studied methods for improving the numerical stability of Cholesky factorization and the accuracy of the solution of the linear system.

• Journal of the Korean Mathematical Society
• /
• v.51 no.3
• /
• pp.473-493
• /
• 2014

This paper concerns with a class of delayed Nicholson's blowflies model with a nonlinear density-dependent mortality term. Under appropriate conditions, we establish some criteria to ensure that the solutions of this model converge globally exponentially to a positive almost periodic solution. Moreover, we give some examples and numerical simulations to illustrate our main results.

• Communications of the Korean Mathematical Society
• /
• v.29 no.4
• /
• pp.505-518
• /
• 2014

Considered here is the first initial boundary value problem for the two-dimensional g-Navier-Stokes equations in bounded domains. We first study the long-time behavior of strong solutions to the problem in term of the existence of a global attractor and global stability of a unique stationary solution. Then we study the long-time finite dimensional approximation of the strong solutions.

• Communications of the Korean Mathematical Society
• /
• v.33 no.3
• /
• pp.1039-1048
• /
• 2018

In this paper we study the dynamics of a general ${\omega}-periodic$ model. Necessary and sufficient conditions for the global stability of zero steady state of the model are given. The conditions under which there exists a unique periodic solutions to the model are determined. We also show that the unique periodic solution is the global attractor of all other positive solutions. Some applications to mathematical models for cancer and tumor growth are given.

• Communications of the Korean Mathematical Society
• /
• v.32 no.3
• /
• pp.579-600
• /
• 2017

In this paper we consider a semilinear pseudoparabolic equation with polynomial nonlinearity and infinite delay. We first prove the existence and uniqueness of weak solutions by using the Galerkin method. Then, we prove the existence of a compact global attractor for the continuous semigroup associated to the equation. The existence and exponential stability of weak stationary solutions are also investigated.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.3
• /
• pp.225-235
• /
• 2002

The color stability of current prosthetic composites is unknown, even though the quality of composite materials has been improving. This study examined the intrinsic color stability of various current prosthetic resins (ceramic-polymers) after an accelerated aging process and the extrinsic color stability after immersion in a coffee solution. By comparing the amount of discoloration after aging with that without aging, the effect of the accelerated aging process on external discoloration could be evaluated. Three current prosthetic composites (Artglass, Targis, Sculpture), one light polymerized direct composite (Z100) and one dental porcelain control (Ceramco) were assessed. The color changes (${\Delta}$E) of all the specimens were determined using the CIE $L^{*}a^{*}b^{*}$ color order system with a reflected spectrophotometer. The results were as follows: 1. The prosthetic composite materials subjected to the accelerated aging test showed no significant difference in color changes (p >.05). 2. In the coffee solution immersion test after the aging process, the color changes of the Targis and Artglass groups were not different from that of the Z100 group, which showed the highest color change. 3. In the immersion only test, a significantly high color change was observed in the sculpture glazing group. 4. The aging process influenced on the color changes more in the Targis, Artglass and Z100 groups than in the Sculpture and Ceramco groups.