• Journal of Power System Engineering
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• v.5 no.1
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• pp.50-56
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• 2001

Jet pumps are used in a great number of engineering applications. In the present study, jet shapes, mixing chamber shapes, and numerical methods for predicting the performance of an annular-type jet pump are investigated to determine the optimal turbulence model. The flow fields are simulated by solving the momentum and the continuity equations with the standard ${\kappa}-{\epsilon}$ and the RNG ${\kappa}-{\epsilon}$ turbulence models at different Reynolds numbers. After that, they are compared with the corresponding experimental data to determine the optimal model. Next, various calculations are conducted to find an optimal shape using the selected turbulence model. The study shows us that the RNG ${\kappa}-{\epsilon}$ model predicts the performance more exactly, and also shows that the most effective performance can be achieved with $12^{\circ}$ reducing angle and 130mm throat length.

• Journal of Korean Society of Rural Planning
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• v.14 no.1
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• pp.23-32
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• 2008

Landscape structure is important to understand a complex patterns and interaction with adjacent habitat in rural area. The aim of this study is to analyze relationship between landscape structure and insect spatial distribution in rural area to suggest applicable possibility of landscape structure as biological indicator. For this purpose, first, four landscape structure criteria such as distance from the forest; density of farmland-forest ecotone; landscape continuity; and field size are selected. Secondly, these criteria are applied to Gangsang-myeon, Yangpyeong-gun where mosaic feature are conserved at various spatial scale. Thirdly, application of landscape structure criteria is verified using correlation with species number, species diversity, and species richness of insect. As a result, it could be suggested that the landscape structure criteria are useful for explaining insect spatial distribution.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.513-518
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• 2007

A polygon-wise constant curvature natural element approximation is presented in this paper for the numerical implementation of the abstract Kirchhoff plate model. The strict continuity requirement in the displacement field is relaxed by converting the area integral of the curvatures into the boundary integral along the Voronoi boundary. Curvatures and bending moments are assumed to be constant within each Voronoi polygon, and the Voronoi-polygon-wise constant curvatures are derived in a selective manner for the sake of the imposition of essential boundary conditions. The numerical results illustrating the proposed method are also given.

• Communications of the Korean Mathematical Society
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• v.37 no.1
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• pp.163-176
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• 2022

In this paper, we introduce some new classes of generalized mappings and prove some common fixed point theorems for a pair of asymptotically regular mappings. Our results extend and improve various well-known results due to Kannan, Reich, Wong, Hardy and Rogers, Ćirić, Jungck, Górnicki and many others. In addition to it, a sequential fixed point for a mapping which is the point-wise limit of a sequence of functions satisfying Ćirić-Proinov-Górnicki type mapping has been proved. Supporting examples have been given in strengthening hypotheses of our established theorems.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.29-35
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• 1999

Soil structure and organic matter have been known to strongly affect water flow and solute transport, yet little information is available concerning soil hydraulic properties related to soil physical and chemical properties in the forest site. The purpose of this study was to quantify the spatial variability and spatial correlation of the measured parameter values from the plots established with the rainfall simulator on Japanese larch(Larix leptolepis) dominated site in Kwangju. Kyunggi-Do. Measurement of soil water flux and retention were made with the inherent soil texture, soil structure, and organic matter. The method was based on the observation that when water was applied at a constant rate to the soil surface on each plot. The method was simple to apply and consists of following steps: (i) Wet the soil from a rainfall simulator with several known discharge rates on a relatively leveled soil surface with and without organic matter. (ii) Once the borders of the ponded zone were steady, saturated hydraulic conductivity( $K_{s}$) and the matric flux function(F) was evaluated from a regression of flux vs. the reciprocal of the ponded area. A conductivity of the form $K_{i+}$$_1$ $_{c}$= $K_{i}$( $_{c}$) [1-d /dz] where flux continuity implies. For this, continuity of matric potential at the interface at all times are as follows: $_1$( $Z_{c}$) = $_2$( $Z_{c}$) = $_{c}$ for steady state intake from water ponded on the soil surface. Results of this investigation showed the importance of understanding spatial variability in wide differences of water retention and saturated hydraulic conductivity with respect to pore geometry and organic matter contents which influenced the water flux throughout the soil profile.l profile.ile.

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.695-706
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• 1996

In the control system $ \dot{x} = f(t,x(t)) + g(t,x(t))\dot{u}, x(0) = \bar{x}, t \in [0,T], $ this paper shows that the map from u with $L^1(m)$-topology to $x_u$ with $L^1(\mu)$-topology is Lipschitz continuous where f is $C^1$, $\mu$ is the Stieltjes measure derived from the function g which is not smooth in the variable t and $x_u$ is the solution of the above system corresponding to u under the assumption that $\dot{u}$ is bounded.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.985-999
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• 2018

This paper is devoted to the existence and uniqueness of $L^p$ (p > 1) solutions for general time interval multidimensional backward stochastic differential equations (BSDEs for short), where the generator g satisfies a ($p{\wedge}2$)-order weak monotonicity condition in y and a Lipschitz continuity condition in z, both non-uniformly in t. The corresponding stability theorem and comparison theorem are also proved.

• Journal of the Chungcheong Mathematical Society
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• v.7 no.1
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• pp.25-32
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• 1994

Let A be a (complex) Banach algebra. The object of the this paper shall be remove the continuity of the derivation in the recently theorems. We prove that every derivation D on A satisfying [D(a), a] ${\in}$ Prad(A) for all a ${\in}$ A maps into the radical of A. Also if ${\alpha}D^3+D^2$ is a derivation for some ${\alpha}{\in}C$ and all minimal prime ideals are closed, then D maps into its radical.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1144-1146
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• 2005

This paper presents the optimal design reducing the rotor inertia in order to improve the driving characteristic of BLDCM for robots. The parallel Genetic Algorithm is performed to rotor inertia minimization in optimal design. Also, velocity profile with finite jerk method is introduced to reduce vibration of BLDCM. As a result, a torque characteristic is same although rotor inertia is reduced 2/3 compared with prototype model. And, maximum vibration value is reduced by 63.4[%1 according to apply finite jerk.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.7 no.2
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• pp.1-11
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• 2003

We suggest a method of $C^2$ surface extension with the aid of well-controlled functions. The extended surface is $C^2$ continuous along the old boundary. The function of the extension surface is obtained by replacing the monomials in the quadratic Taylor polynomial of the given surface-representing function by other functions subject to some boundary conditions. We present several sets of control functions. In order to illustrate our suggestion, it is shown that surfaces with a circular boundary and a square boundary can be extended using several base functions.