• 한국환경과학회지
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• 제21권7호
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• pp.805-813
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• 2012

The removal property of Cu and Zn ions by chemical precipitation and adsorption using zeolite(Z-C1) prepared from coal fly ash(CFA) were evaluated in this study. Adsorption kinetic and equilibrium mechanisms described to analyze parameters and correlation factors with Lagergen $1^{st}$ and $2^{nd}$ order model and Langmuir and Freundlich model. Analysis of adsorption kinetics data revealed that the pseudo $2^{nd}$ order kinetics mechanism was predominant. The equilibrium data in pH 3 - 5 were able to be fitted well to a Langmuir model, by which the maximum adsorption capacities($q_{max}$) were determined at 124.9 - 140.1 mg $Cu^{2+}/g$ and 153.2 - 166.9 mg $Zn^{2+}/g$, respectively. We found that Z-C1 has a potential application as absorbents in metal ion recovery with low pH.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권1호
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• pp.1-5
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• 2013

Global climate changes affect the local hydrologic cycle, and subsequently, require changes in water resource management strategies of Korea. Variations in precipitation and urbanization have adverse effects on the reasonable and efficient utilization of groundwater resources. Groundwater management strategies of Korea have been implemented based on the evaluation of "sustainable yield", which is calculated from the amount of annual recharge. However, this sustainable yield has no consideration of natural discharge and dynamic equilibrium of the groundwater system. Therefore, for the effective groundwater management strategies of the following decades, we need representative and reliable observations, and have to develop methods for the systematic analysis and interpretations of the data to draw valid information in linkage of natural and societal environmental changes.

• Structural Engineering and Mechanics
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• 제7권2호
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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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.405-411
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• 1998

An iterative numerical computational algorithm is presented to design a plate of shell element subjected to membrane and flexural forces. Based on equilibrium consideration, equations for capacities of top and bottom reinforcements in two orthogonal directions have been derived. The amount of reinforcement is determined locally, i. e., for each sampling point, from the equilibrium between applied and internal forces. One case of design is performed for a hyperbolic paraboloid saddle shell (originally used by Lin and Scordelis) to check the design strength against a consistent design load, therefore, to verify the adequacy of design practice for reinforced concrete shells. Based on nonlinear analyses performed, the analytically calculated ultimate load exceeded the design ultimate load from 14-43% for an analysis with relatively low to high tension stiffening, ${\gamma}$ =5~20 cases. For these cases, the design method gives a lower bound on the ultimate load with respect to Lower bound theorem. This shows the adequacy of the current practice at least for this saddle shell case studied. To generalize the conclusion many more designs-analyses are performed with different shell configurations.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1993년도 가을 학술발표회 논문집
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• pp.63-68
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• 1993

Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

• 한국조리학회지
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• 제3권
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• pp.5-22
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• 1997

A foodservice manager always is concerned with which of the menus or potential menus, or which of the menu items is best for the operation. A menu may be profitable but not popular, or vice versa. How dose one compare one menu with another\ulcorner A technique to accomplish this is Menu Scoring, which was developed by Michael Hurst. It can be used to analyze possible menu changes by estimating sales of the new items and seeing what the new menu score will be. But menu scoring considers food costs, limited menu and relation only. After the menu score is calculated, management can determine more effectively why one score differs from another. Thus, this study is focused on the general equilibrium effect analysis. It will be attained from menu formation and menu type. I concluded that one can also change menu prices and see how menu popularity and profitability and the resulting menu score are affected through this study.

• Journal of applied mathematics & informatics
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• 제29권5_6호
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• pp.1193-1204
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• 2011

In the present paper we consider a differential-algebraic prey-predator model with stage structure for prey and harvesting of predator species. Stability and instability of the equilibrium points are discussed and it is observed that the model exhibits a singular induced bifurcation when the economic profit is zero. It indicates that the zero economic profit brings impulse, i.e. rapid expansion of the population and the system collapses. For the purpose of stabilizing the system around the positive equilibrium, a state feedback controller is designed. Finally, numerical simulations are given to show the consistency with theoretical analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.212-217
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• 1993

A 2-dimensional FEM/GEM program was developed for analyzing forming processes of an arbitrarily shaped draw-die, in which plane strain condition is assumed and linear line elements are employed. FEM formulation adopted a new algorithm for solving force equilibrium as well as non-penetration condition simultaneously. For the case of numerical divergence at nearly final forming stages and the initial guess in Newton-Raphson iterations, geometric force equilibrium method(GEM) is also introduced. The developed program was tested with the simulation of stamping processes of automotive bonnet inner pannel in order to verify the usefulness and validity of FEM/GEM formulation.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제14권1호
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• pp.1-16
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• 2010

An epidemic model with Classical Kermack-Mckendrick incidence rate under a limited resource for treatment is proposed to understand the effect of the capacity for treatment. We have assumed that treatment function is strictly increasing function of infective individuals and becomes constant when the number of infective is very large. Existence and stability of the disease free and endemic equilibrium are investigated, boundedness of the solutions are shown. Even in this simple version of the model, backward bifurcation and multiple epidemic steady states can be observed with some sets of parameter values. Hopf-bifurcation analyses are given and numerical examples are provided to help understanding.

• 한국해양공학회지
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• 제17권6호
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• pp.77-82
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• 2003

The absorption of water into an anti-corrosive organic coating, such as alkyd and urethane resin coating, was investigated, using a quartz crystal microbalance (QCM). Anticorrosive properties of the coatings were also measured, by means of electrochemical impedance spectroscopy (EIS). The overall absorption of water in the coating is determined by the chemical nature of resin, and decreases with increasing thickness. The enhancement of anti-corrosive performance, through increase of coating thickness, was more remarkable in the case of the coating that hadlower equilibrium water absorption. The absorption kinetics curves were Fickian in nature. The EIS analysis confirmed that the resin, having lower equilibrium water absorption, shows higher anti-corrosive performan.