• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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• pp.37-44
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• 2021

The information products dramatically reduce the production costs of vertically differentiated products. Information products are also more likely to be affected by network externalities. Thus the proliferation of digital products is increasing the interests in network externality and vertical product differentiation. In step with this trend, the impact of network externalities on price competition in vertically differentiated markets has been continuously studied. Existing studies related to this topic have assumed that network externalities increase consumers' willingness to pay per unit quality. The results show that higher quality products are affected more by network externality. However, network externality is essentially a concept affected by the size of the consumer, not a concept associated with quality. In this work, unlike previous studies, we present a new market model that reflects the essential definition of network externality. Based on the proposed market model, we derive both simultaneous and sequential Nash equilibria and analyze them numerically. The main results obtained from the analysis can be summarized as follows. First, network externalities primarily increase the demand for low-quality products and have a secondary impact on the demand for high-quality products. Second, the larger the quality difference between products, the more profitable they are. It also has been shown that sequential pricing methods are more advantageous in terms of revenue than simultaneous pricing method.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.924-929
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• 1998

In this work, high pressure binary phase equilibria data of carbon dioxide with acetonitrile and acrylonitrile were obtained experimentally. A new static type experimental apparatus was built to measure temperature, pressure and phase equilibria composition. The accuracy of the experimental apparatus was tested by comparing the measured phase equilibria data of the carbon dioxide-acetonitrile system at $75^{\circ}C$ with those of McHugh and coworkers. The binary phase behavior data of carbon dioxide-acetonitirle system were measured from 2.4 to 14.5 MPa at $55^{\circ}C$, $75^{\circ}C$ and $100^{\circ}C$. Also, the phase equilibria of the system carbon dioxide-acrylonitrile were measured from 1.6 MPa up to 13.9 MPa at $45^{\circ}C$, $65^{\circ}C$, $85^{\circ}C$ and $105^{\circ}C$. The solubility of acetonitrile and acrylonitrile increases as the temperatures increases at constant pressure. Also, these two carbon dioxide-polar solute system have continuous critical-mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxide and acetonitrile or acrylonitrile. The experimental data obtained in this study were modeled using the Peng-Robinson equation of state. Good agreement between calculated and experimental results was observed.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.218-226
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• 1995

Ion exchange equilibria in bulk and rhizosphere soil collected from peach seedlings were studied to find exchange equations that could be used in chromatographic models dealing with movement and distribution of fertilizer ammonium and exchangeable cations in soil profiles. Soil samples were equilibrated with mixtures of $NH_4Cl$, KCI, and $CaCl_2$ solutions and then extracted with $Sr(NO_3)_2$ solution to determine exchangeable cation compositions at equilibrium. Exchange data were fitted to Vanselow's, Gapon's, and Kerr's equations, but those formulations did not adequately describe the equilibria. An empirical equation of the form : ${\frac{\alpha_i^m}{a_j^n}}=K{\frac{(iX)^{mPi}}{(jX)^{nPj}}}$ which has an exponent on each of the exchangeable cation concentrations could describe the equilibria very well over the range of treatments. In this equation ${\alpha}^i$ and ${\alpha}^j$ are activities of cation i and j with valences m and n respectively. (iX) and (jX) are concentrations of exchangeable cations. Mole or equivalent fractions can be considered as the exchangeable ion concentration unit. Arbitrary constants $P_i$ and $P_j$, and distribution coefficient K can be found with multiple regression for the logarithmic form of the equation.

• Journal of the Korean Mathematical Society
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• v.37 no.5
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• pp.707-720
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• 2000

Conley index is used study bifurcation from equilibria of full bounded solutions to parameter dependent families of ordinary differential equations of the form {{{{ {dx} over {dt} }}}} =$\varepsilon$F(x, t, $\mu$). It is assumed that F(x, t,$\mu$) is uniformly almost periodic in t.

• Journal of the Chungcheong Mathematical Society
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• v.13 no.1
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• pp.13-20
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• 2000

The purpose of this paper is to give a new existence theorem of a generalized weight Nash equilibrium for generalized multiobjective games by using the quasi-variational inequality due to Yuan.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.607-614
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• 1998

In this note we shall give a new existence theorem of equilibrium in social systems with coordination under general assump-tions by using the Kakutani fixed point theorem.

• Journal of the Chungcheong Mathematical Society
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• v.12 no.1
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• pp.53-61
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• 1999

The purpose of this paper is to give a new existence theorem of equilibrium in generalized fuzzy games with uncountable number of agents.

• Journal of applied mathematics & informatics
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• v.7 no.1
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• pp.247-255
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• 2000

The purpose of this paper is to give new existence theorems of equilibrium in abstract economies with uncountable number of agents and general preference correspondences.

• Bulletin of the Korean Mathematical Society
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• v.42 no.2
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• pp.257-267
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• 2005

The aim of this paper is to give three equilibrium existence theorems for generalized games with lower semi continuous constraint and preference multimaps by using Michael's continuous selection theorem.

• 한국전자현미경학회:학술대회논문집
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• 2000.05a
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• pp.81-84
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• 2000