• Journal of the Korean Applied Science and Technology
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• v.26 no.2
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• pp.191-198
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• 2009

We have tested the stability of paeoniflorin, a new cosmetic ingredient, extracted from the roots of Paeoniae lactiflora. The stability of aqueous paeoniflorin solution at pH 3, 5 and 7 varied by adding buffer solution was tested at $0^{\circ}C,\;25^{\circ}C,\;40^{\circ}C,\;and\;65^{\circ}C$. The test was performed with or without UV light. The solution of paeoniflorin was stable at pH 3.0, however, the recovery rate of paeoniflorin was 40% at pH 7.0. The stability of paeoniflorin solution was decreased as the pH of paeoniflorin solution was increased by pH 7.0. The effect of storage temperature of paeoniflorin solution shows that the stability of paeoniflorin solution was decreased as the temperature was increased. The stability of paeoniflorin was rather good under UV light than the condition given above $40^{\circ}C$. The stability of paeoniflorin in W/O emulsions shows similar pattern to that of aqueous solution.

• International Journal of Industrial Entomology and Biomaterials
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• v.33 no.2
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• pp.138-143
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• 2016

In the present study, silk fibroin (SF) was dissolved in $CaCl_2/H_2O/EtOH$ solution at $85^{\circ}C$. After the dissolution, the SF solution was cooled down and stored at $4^{\circ}C$ for 28 d. The stability of the solution's viscosity and electrospinnability was observed to examine the stability of SF molecules during storage in $CaCl_2/H_2O/EtOH$ solution. The viscosities of $SF/CaCl_2/H_2O/EtOH$ solution and SF formic acid solution did not change during 28 days' storage of SF in $CaCl_2/H_2O/EtOH$ solution. The electrospinnability of the SF solution, mean diameter of the electrospun SF fiber, and crystallinity index of electrospun SF web did not change, regardless of the length of the storage period. These results imply that SF molecules do not degrade during 28 days' storage in $CaCl_2/H_2O/EtOH$ solution.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.193-200
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• 1999

Since Broms and Bennermark(1967) suggested the face stability criterion based on laboratory extrusion tests and field observations, the face stability of a tunnel driven in cohesive material has been studied by several authors. And recently, more general solution for the tunnel front is given by Leca and Panet(1988). They adopted a limit state design concept to evaluate the face stability of a shallow tunnel driven into cohesionless material and showed that the calculated upper bound solution represented the actual behavior reasonably well. In this study, two factors are simultaneously considered for assessing tunnel face stability: One is the effective stress acting on the tunnel front calculated by upper bound solution; and the other is the seepage force calculated by numerical analysis under the condition of steady state ground water flow. The model tests were performed to evaluate the seepage force acting on the tunnel front and these results were compared with results of numerical analysis. Consequently, the methodology to evaluate the stability of a tunnel face including limit analysis and seepage analysis is suggested under the condition of steady state ground water flow.

• Korean Journal of Mathematics
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• v.4 no.1
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• pp.39-43
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• 1996

Large-time asymptotic behavior of the solutions of interacting population reaction-diffusion systems are considered. Polynomial stability was proved.

• Journal of applied mathematics & informatics
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• v.31 no.3_4
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• pp.577-594
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• 2013

In this paper, we study the global stability and the existence of almost periodic solution of high-order Hopfield neural networks with distributed delays of neutral type. Some sufficient conditions are obtained for the existence, uniqueness and global exponential stability of almost periodic solution by employing fixed point theorem and differential inequality techniques. An example is given to show the effectiveness of the proposed method and results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.820-833
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• 1995

An analysis is performed to examine the equilibrium state and the stability of modeled Reynolds stress equations for homogeneous turbulent shear flows. The system of the governing equations consists of four coupled ordinary differential equations. The equilibrium states are found by the steady state solution of the governing equations. In order to investigate the stability of the system about its state in equilibrium, and eigenvalue problem is constructed. As a result, constraints for the coeffieients in the model equations are obtained by the stability condition of the equilibrium state as well as by their physically realizable bounds. It is observed that the models with pressure-strain rate correlation that are linear in the anisotropy tensor are stable and produce reasonable equilibrium tensor do not behave properly. Stability considerations about three most commonly used models are given in detail in the final section.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.7 no.1
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• pp.25-31
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• 2003

The concepts of stability of algorithms for solving the symmetric and generalized symmetric-definite eigenproblems are discussed. An algorithm for solving the symmetric eigenproblem $Ax={\lambda}x$ is stable if the computed solution z is the exact solution of some slightly perturbed system $(A+E)z={\lambda}z$. We use both normwise approach and componentwise way of measuring the size of the perturbations in data. If E preserves symmetry we say that an algorithm is strongly stable (in a normwise or componentwise sense, respectively). The relations between the stability and strong stability are investigated for some classes of matrices.

• YAKHAK HOEJI
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• v.56 no.2
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• pp.74-79
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• 2012

Citrate-capped silver nanoparticles (AgNPs) are widely used in industry, consumer products and medical appliances. However, information on the toxicity, environmental fate and toxicokinetics are not enough. In this study, stability of citrate-capped AgNPs was investigated using different types of isotonic solution, which is important in the toxicokinetic study by the exposure route of intravenous injection. Size, morphology, zeta potential and ion formation were investigated in isotonic solutions for the physico-chemical characterization of AgNPs. Aggregation and precipitation of AgNPs were observed in saline or phosphate-buffered saline while they were stable without precipitation in 2% glycerol of isotonic solution. The average size of AgNPs in 2% glycerol was 6~10 nm, which was almost same as that in water-based suspension of AgNPs. Zeta potential was ranged from -30 mV to -60 mV, which was in the range of original stock AgNPs. The stability was maintained during the whole experimental period of 48 hours. Furthermore, the stability was not changed in different temperature (10~36$^{\circ}C$) and at different concentrations (10~1,000 ppm). The osmolarity of the AgNPs suspension was $299{\pm}1$ mOsm/kg which was in isotonic range. These data suggest that AgNPs in 2% glycerol solution can be used for the preparations of intravenous injection for toxicokinetic study without undesired disturbance of blood isotonicity.

• Honam Mathematical Journal
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• v.26 no.1
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• pp.45-59
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• 2004

In this paper we obtain the general solution the functional equation $a^2f(\frac{x-2y}{a})+f(x)+2f(y)=2a^2f(\frac{x-y}{a})+f(2y).$ The type of the solution of this equation is Q(x)+A(x)+C, where Q(x), A(x) and C are quadratic, additive and constant, respectively. Also we prove the stability of this equation in the spirit of Hyers, Ulam, Rassias and $G\check{a}vruta$.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.517-522
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• 2006

In this paper, we obtain the general solution and the generalized Hyers-Ulam stability of the multi-additive functional equation $f(x1+x2,y1+y2,z1+z2)={\Sigma}_{1{\le}i,j,k{\le}2}\;f(x1,yj,zk)$.