• Geomechanics and Engineering
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• v.22 no.6
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• pp.553-564
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• 2020

In this study, a simple numerical approach for a circular tunnel opening in strain-softening surrounding rock is proposed considering out-of-plane stress and seepage force based on Biot's effective stress principle. The plastic region of strain-softening surrounding rock was divided into a finite number of concentric rings, of which the thickness was determined by the internal equilibrium equation. The increments of stress and strain for each ring, starting from the elastic-plastic interface, were obtained by successively incorporating the effect of out-of-plane stress and Biot's effective stress principle. The initial value of the outmost ring was determined using equilibrium and compatibility equations. Based on the Mohr-Coulomb (M-C) and generalized Hoek-Brown (H-B) failure criteria, the stress-increment approach for solving stress, displacement, and plastic radius was improved by considering the effects of Biot's effective stress principle and the nonlinear degradation of strength and deformation parameters in plastic zone incorporating out-of-plane stress. The correctness of the proposed approach is validated by numerical simulation.

• Journal of Korean Association for Spatial Structures
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• v.13 no.2
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• pp.75-82
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• 2013

For each cable component in a cable dome structure, pre-tension is needed for stability of whole the structure. The summation of these pre-tension at each joint should be zero to achieve the self equilibrium structure. The first step in cable dome structure analysis is to find the ratio of pre-tension in each member which can produce a stable and structure on self-equilibrium. In this paper, a new method based on the basic principle of closed force polygon for equilibrium system is proposed for the determination of self-equilibrium mode of cable dome structure. A single layer cable dome and two multi layer type domes have been analyzed. The ratios of cable members are determined by the presented method, and check the validation of the results by numerical calculation.

• Bulletin of the Korean Mathematical Society
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• v.51 no.2
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• pp.437-442
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• 2014

In this paper we prove Ekeland's variational principle in the setting of locally complete spaces for lower semi continuous functions from above and bounded below. We use this theorem to prove Caristi's fixed point theorem in the same setting and also for lower semi continuous functions.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.265-278
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• 2002

A concept test was administered to college students and teachers to identify their understanding of chemical equilibrium and equilibrium shift. The subjects were 53 freshmen in the General Chemistry class, 28 juniors in the Physical Chemistry class and 26 seniors from a university and 10 high school teachers in Seoul. Test items include the calculations of partial pressure and concentration of the gas in the mixture, the equilibrium constant cal-culation and the prediction of equilibrium shift when an inert gas is added to the gaseous reaction system, and the equilibrium concentration calculation and the prediction of equilibrium shift when water or common ion is added to the weak acid solution. The test was focused to identify whether the subjects can predict equilibrium shift using the reaction quotient change for the situations in which Le Chatelier principle is difficult to apply. The results showed that the achievements of teachers and juniors were significantly higher than those of freshmen and seniors. Many stu-dents had difficulties in predicting equilibrium shift using the reaction quotient while they could calculate partial pres-sure and concentration for the same situation. It means they are lack of conceptual understanding of chemical equilibrium shift.

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.494-499
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• 2007

In this paper, we have investigated how transmission network constraints can be modeled in an electricity market equilibrium model. Under Cournot competition assumption, a game model is set up considering transmission line capacity constraints. Based on locational marginal pricing principle, market clearing is formulated as a total consumers# benefit maximization problem, and then converted to a conventional optimal power flow (OPF) formulation with a linearized transmission model. Using market clearing formulation, best response analysis is formulated and, finally, Nash equilibrium is formulated. In order for illustration, a numerical study for a four node system with two generating firms and two loads are presented.

• Structural Engineering and Mechanics
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• v.7 no.2
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• pp.159-180
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• 1999

The present paper shows a new non-tensorial approach to derive basic equations for various structural analyses. It can be used directly in numerical computation procedures. The aim of the paper is, however, to show that the approach serves as an excellent tool for analytical purposes also, working as a link between analytical and numerical techniques. The paper gives a method to derive, at first, expressions for strains in general beam and shell analyses, and secondly, the governing equilibrium equations. The approach is based on the utilization of local fixed Cartesian coordinate systems. Applying these, all the definitions required are the simple basic ones, well-known from the analyses in common global coordinates. In addition, the familiar principle of virtual work has been adopted. The method will be, apparently, most powerful in teaching the theories of curved beam and shell structures for students not familiar with tensor analysis. The final results obtained have no novelty value in themselves, but the procedure developed opens through its systematic and graphic progress a new standpoint to theoretical considerations.

• Journal of Korean Society of Transportation
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• v.17 no.5
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• pp.69-78
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• 1999

This paper defines the reliable based route choice Principle and formulates the reliability based equilibrium traffic assignment using the Principle. The reliability is defined as the difference of travel demand and capacity using the interference theory of the system engineering. An efficient solution a1gorithm based on Frank-Wo1fe algolithm is Presented to calculate and compare the reliability based traffic assignment with conventional travel time based assignment using small and large scaled road networks. The results show that reliability based traffic assignment converges to equilibrium solution in a reasonable computing time. The equilibrium link flows between reliability and travel time based traffic assignment differ each other in the sense that reliability based assignment is assigned based on the maximum difference of travel demand and link capacity whilst travel time based is assigned on the shortest travel time.

• Journal of Environmental Impact Assessment
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• v.13 no.4
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• pp.213-222
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• 2004

Exergy is defined as the amount of work (entropy-free energy) a system can perform when it is brought into thermodynamic equilibrium with its environment. Exergy measures the distance from the inorganic soup in energy terms. Therefore, exergy can be considered as fuel for any system that converts energy and matter in a metabolic process. The aim of this study is to introduce structural dynamic modelling which is based on maximum exergy principle. Especially, almost ecological models couldn't explain algal succession until now. New model (structural dynamic model) is anticipated to predict or explain the succession theory. If the new concept using maximum exergy principle is used, algal succession can be explained in many actual cases. Therefore, It is estimated that structural dynamic model using maximum exergy principle might be a excellent tool to understand succession of nature from now on.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.156-159
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• 2003

The analytic solution of displacements of thin cylindrical pressure vessel made by carbon fiber T700/Epoxy was obtained using equilibrium equations of orthogonal curvilinear coordinate system. Equilibrium equations with the assumed displacement field were derived from a reasonable description of the behavior of thin elastic shells using principle of virtual work. Some analyses of the theoretical solution are presented and compared with the results of hydraulic tests of the pressure vessel.

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1327-1335
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• 2011

This paper demonstrates that there is a unique exponentially stable equilibrium state of a class of impulsive cellular neural network with delays. The analysis exploits M-matrix theory and generalized comparison principle to derive some easily verifiable sufficient conditions for the global exponential stability of the equilibrium state. The results extend and improve earlier publications. An example with its simulation is given for illustration of theoretical results.