• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1237-1244
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• 2015

A gerotor can be manufactured in a miniature size because it has a high discharge per cycle and a simple structure. Gerotors are widely used for the lubrication oil of an engine and as the hydraulic source of an automatic transmission. Recently, improvements in fuel efficiency and noise reduction have come to the fore in the automobile industry, and it has been necessary for better fuel efficiency to continuously improve the flow rate and noise of internal gear pumps through the optimal design of the gerotor and port shape. In this study, gerotors were generated based on the equations derived for a lobe shape with multiple profiles (ellipse 1-elliptical involute-ellipse 2). The ranges of the design parameters were considered to prevent a cusp and loop. In addition, the optimal lobe shape was obtained by determining the influence of the lobe shape on the performances (flow rate, irregularity, etc.), according to the values of the design parameters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.111-117
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• 1990

The hydraulic line haulers are now widely used to haul the main line, but the other hauling operations are still done manually in most pot fisheries. The oval type hooks which are connected between the loops and the post are tested for basic capability by the universal tension meter in order to develop the automatic separating system. The pots attached to the oval type hooks are separated automatically from the loops while the oval type hooks are running through the trumpet separator with the side roller and the results are as follows: 1. The tension of the large oval hooks (ø3.1mm) for missing pots and the compressive load at the end of hooks by hand are about 60kg and 6kg, and range of tension for passing through the trumpet is 11~15kg. 2. Automatic separating ratio of the pots with the large oval hooks is about 99% when the trumpet separator is attached to front or rear of the side roller in the laboratory. 3. The separating ratio of the pot with the large oval hooks while hauling operation in the sea is about 97% when the trumpet separator is oriented on the port bulwark departed 2m from the side roller.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.609-615
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• 2012

In LSP (laser shock peening) treatment, the laser source geometries when the laser beam strikes the metal target area are diverse. The laser spot geometry affects the residual stress field beneath the treated surface of the metallic materials, which determines the characteristics of the pressure pulse. In this paper, detailed finite-element (FE) simulations on laser shock peening have been conducted in order to predict the magnitude and of the residual stresses and the depth affected in Inconel alloy 600 steel. The residual stress results are compared for circular, rectangular, and elliptical laser spot geometries. It is found that a circular spot can produce the maximum compressive residual stresses near the surface but generates tensile residual stresses at the center of the laser spot. In the depth direction, an elliptical laser spot produces the maximum compressive residual stresses. Circular and elliptical spots plastically affect the alloy to higher depths than a rectangular spot.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.1-9
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• 2002

There is the high possibility of crack initiation from mechanical joints, which are widely used in aircraft fuselages, due to the development of stress concentration and contact pressure. In this paper, the mixed-mode stress intensity factors at the surface and deepest points of an inclined quarter elliptical corner crack in mechanical joints are analyzed by the weight function method. The coefficients included in the weight function are obtained by finite element analyses for reference loadings. Critical angle at which mode I stress intensity factor becomes maximum is determined by analyzing the variation of stress intensity factors along incline angle of crack and the effects of the amount of clearance and crack depth on the critical angle are investigated.

• Journal of KIISE:Software and Applications
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• v.31 no.9
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• pp.1161-1170
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• 2004

This paper proposes to segment skin color areas using a clustering algorithm. Most of previously proposed clustering algorithms have some difficulties, since they generally detect hyperspherical clusters, run in a batch mode, and predefine a number of clusters. In this paper, we use a well-known elliptical clustering algorithm, an EM algorithm, and modify it to learn on-line and find automatically the number of clusters, called to an EAM algorithm. The effectiveness of the EAM algorithm is demonstrated on a task of skin color region segmentation. Experimental results present the EAM algorithm automatically finds a right number of clusters in a given image without any information on the number. Comparing with the EM algorithm, we achieved better segmentation results with the EAM algorithm. Successful results were achieved to detect and segment skin color regions using a conditional probability on a region. Also, we applied to classify images with persons and got good classification results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.455-462
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• 2017

The magnetic interaction between elliptic Janus magnetic particles are investigated using a direct simulation method. Each particle is a one-to-one mixture of paramagnetic and nonmagnetic materials. The fluid is assumed to be incompressible Newtonian and nonmagnetic. A uniform magnetic field is applied externally in a horizontal direction. A finite-element-based fictitious domain method is employed to solve the magnetic particulate flow in the creeping flow regime. In the magnetic problem, the magnetic field in the entire domain, including the particles and the fluid, is obtained by solving the governing equation for the magnetic potential. Then, the magnetic forces acting on the particles are calculated via a Maxwell stress tensor formulation. In a single particle problem, it is found that the orientation angle at equilibrium is affected by the aspect ratio of the particle. As for the two-particle interaction, the dynamics and the final conformation of the particles are significantly influenced by the aspect ratio, the orientation, and the spatial positions of the particles. For the given positions of the particles, the fluid flow is also influenced by the orientation of each particle. The self-assembly structure of the particles is not a fixed one, but it varies with the above-mentioned factors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.15-20
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• 2005

Two-dimensional incompressible Navier-Stokes flow solver is developed using SIMPLER method to study the unsteady viscous flow physics over two-dimensional ellipses. Unsteady viscous flows over various thickness-to-chord ratios of 0.6, 0.8, 1.0, and 1.2 elliptic cylinders are simulated at different Reynolds numbers of 200, 400, and 1,000. This study is focused on the understanding the effects of Reynolds number and elliptic cylinder thickness on the drag and lift forces. The present numerical solutions are compared with available experimental and numerical results and show a good agreement. Through this study, it is observed that the Reynolds number and the cylinder thickness affect not only the frequency of the force oscillations but also the mean values and the amplitudes of the total drag and lift forces significantly.

• Applied Microscopy
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• v.24 no.4
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• pp.1-12
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• 1994

Various plastids in leaf and bracteal tissues of Cannabis sativa L. were examined by electron microscopy. Young chloroplasts without starch grain in mesophyll cells were ellipsoidal, and osmiophilic globules within them were common in stroma. During the plastid differentiation, the mature chloroplasts in mesophyll were changed in shape depending on the numbers and sizes of starch grain in stroma. Electron-dense granular substances were occurred along the outer membrane of chloroplasts in mesophyll. Typical plastids with reticulate body were present in the glandular trichomes. Electron-grey material appeared along the surface of a plastid. A light area in reticulate body is considered to represent junction point of thylakoids.

• Journal of the Korean Institute of Gas
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• v.18 no.2
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• pp.48-54
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• 2014

A unique optical waveguide structure is proposed to enhance the optical characteristics of alcohol screening sensors. This structure is then simulated. The structure consists of two elliptical waveguides that have a common focus to one side and has an IR source and detector at each of the other focal points of the ellipses. When the angle between the two elliptical waveguides is increased from 30 degrees to 90 degrees, the maximum level of irradiance is greatly decreased, falling from $2.23{\times}10^6 W/m^2$ to $5.74{\times}10^5W/m^2$. However, the diameter of the incident rays is at a minimum of 1.86mm and the total incident flux is less than 10% lower when compared to the structure at $90^{\circ}$. It can be seen from the simulation results that this structure might enhance the sensitivity of an optical gas sensor which has a large absorption wavelength.

• The Korean Journal of Applied Statistics
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• v.16 no.1
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• pp.101-115
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• 2003

Lately there has been much theoretical and applied interest in linear models with non-normal heavy tailed error distributions. Starting Zellner(1976)'s study, many authors have explored the consequences of non-normality and heavy-tailed error distributions. We consider hierarchical models including selection models under a skewed heavy-tailed e..o. distribution proposed originally by Chen, Dey and Shao(1999) and Branco and Dey(2001) with Dirichlet process prior(Ferguson, 1973) in order to use a meta-analysis. A general calss of skewed elliptical distribution is reviewed and developed. Also, we consider the detail computational scheme under skew normal and skew t distribution using MCMC method. Finally, we introduce one example from Johnson(1993)'s real data and apply our proposed methodology.