• Communications of the Korean Mathematical Society
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• v.19 no.3
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• pp.507-517
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• 2004

Let (2,2,2,2) be ramification indices for the Riemann sphere. It is well known that the regular branched covering map corresponding to this, is the Weierstrass P function. Lattes [7] gives a rational function R(z)= ${\frac{z^4+{\frac{1}{2}}g2^{z}^2+{\frac{1}{16}}g{\frac{2}{2}}$ which is chaotic on ${\bar{C}}$ and is induced by the Weierstrass P function and the linear map L(z) = 2z on complex plane C. It is also known that there exist regular branched covering maps from $T^2$ onto ${\bar{C}}$ if and only if the ramification indices are (2,2,2,2), (2,4,4), (2,3,6) and (3,3,3), by the Riemann-Hurwitz formula. In this paper we will construct regular branched covering maps corresponding to the ramification indices (2,4,4), (2,3,6) and (3,3,3), as well as chaotic maps induced by these regular branched covering maps.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3154-3158
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• 2008

A liquid rocket engine performance has been analyzed as a function of combustion pressure with LOx/RP-1R. The present method is verified by comparing the specific impulse for various combustion pressure with given pump head model. The optimal combustion pressure is between 150 bar and 200 bar for given efficiencies. Both the optimal combustion pressure and the specific impulse increase for increased turbine efficiency. The optimal combustion pressure decreases and the specific impulse increases for increased combustion efficiency. The pump efficiency and the turbine inlet temperature have the same qualitative effect as the turbine efficiency.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.330-333
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• 2008

The hybrid air-conditioner, where air is cooled both by convection and radiation, is developed. The indoor unit of the air-conditioner consists of radiation panel and dehumidification coil, where refrigeration R-134a is supplied by independent refrigeration cycles. Optimum refrigerant charge was 750g for both cycles. Optimum evaporation pressure was 3.7 bar for the radiation panel cycle and 3.9 bar for the dehumidification cycle. The cooling capacity of the radiation panel was 1.01 kW and that of the dehumidification coil was 0.94kW, which yielded COP of 3.3.

• Asian Journal of Turfgrass Science
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• v.18 no.4
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• pp.211-219
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• 2004

Transgenic zoysiagrass (Zoysia japonica cv. Zenith) plants have been obtained by particle bombardment of embryogenic callus with the plasmid pSMABuba, which contains hygromycin resistance (hpt) and bialaphos resistance (bar) genes. Parameters on DNA delivery efficiency of the particle bombardment were partially optimized using transient expression assay of a chimeric $\beta-glucuronidase$(gusA) gene driven by the CaMV 35S promoter. Stably transfarmed zoysiagrass plants were recovered with a selection scheme using hygromycin. Transgenic zoysiagrass plants were confirmed by PCR analysis with specific primer for bar gene. Expression of the transgene in transformed zoysiagrass plants was demonstrated by Reverse transcriptase (RT)-PCR analysis. All the tested transgenic plants showed herbicide BastaR resistance at the field application rate of $0.1\%-0.3\%$.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.1
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• pp.49-56
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• 1987

This study is a part f the research on the coupled vibration of train wheel with stepped thickness and rail. The research was conducted for the purpose of examining the dynamic characteristics of train wheel which considered the effect of rotatory inertia and preventing the vibrations of the high speed railway. The In-plane compressive stresses were computed by the rotation of train wheel and the reaction depending on the condition of rolling. The equation of transverse vibration of the train wheel was obtained by Lagrange's equation. As a result of study, it is known that the effect of rotatory inertia and the increment of thickness ratio, h over bar decrease frequency but the increment of radius ratio, r over bar increase frequency.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.18-21
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• 2008

The wetting behavior of molten Fe on ${\alpha}-Al_2O_3$ single crystals with three different crystallographic orientations, $R(01\bar{1}2),\;A(11\bar{2}0),\;and\;C(0001)$, was investigated using the sessile drop method under a 10%$H_2-Ar$ atmosphere at 1873 K. It was found that the differences in the contact angle of the three differently oriented ${\alpha}-Al_2O_3$ single crystals were not significant (within $5^{\circ}$, which corresponded to the changes in the work of adhesion of $157mJ/m^2$) due to the surface reconstruction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.23-31
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• 2016

In this study, we modified the conventional tensile split Hopkinson bar(TSHB) apparatus typically used for the high strength steel to evaluate the tensile deformation behavior of soft metallic sheet materials under high strain rates. Stress-strain curves of high purity single and multi-crystalline materials were obtained using this experimental procedure. Grain morphology and initial crystallographic orientation were characterized by EBSD(Electron Backscattered Diffraction) method measured in a FE-SEM(Field emission-scanning electron microscopy). The fractured surfaces were observed by using optical microscopy. The relationship between plastic deformation of aluminum crystalline materials under high-strain rates and the initial microstructure and the crystallographic orientations has been addressed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.78-86
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• 1992

This paper aims at investigating the effect of steel ratio and the magnitude of edge-ratio on the mechanical characteristics of reinforced concrete ring sector plate. The influence of steel bars was taken into account by coupling stiffness matrix of the steel bar element with that of the concrete plate element without dealing with separate element of steel bar and by establishing the composite stiffness matrix, which leads to the desirable result which does not increase th number of element could be obtained. Through case studies with 6 cases various steel ratios in ring sector plate supported at four edges and 4 cases with different open angles, the influence of the steel ratio was examined. A numerical analysis to find out the effect of the steel ratio d ue to above mentioned cases was carried out by 4 boundary conditions ; all edges clamped (B.C-1), all edges simply supported (B.C-2), curvilinear two edges clamped and other edges free (B.C-3) and curvilinear two edges simply supported and other edges free(B.C-4). The main results obtained are summarized as follows : 1. The effect of steel ratio on the magnitude of lateral deflection and x-directional bending moment at the center of sector plate and the midpoint of outer and inner curvilinear edges is almost the same up to $30^{\circ}$ of open angle. Beyond $30^{\circ}$ of the angle, the larger the angle, the greater the effect of ratio. 2. In design works using balanced steel ratio, the effect of steel bar can be ignored. But for larger open angles, especially greater than $90^{\circ}$, it proves desirable to consider the effect of steel bar. 3. The effect of the arc length of center circle/straight edge on lateral deflection and bending moment is remarkable in B.C-2. For larger open angle, the effect is also noted except for B.C-3 which turn out hardly affected. 4. The effect of the radius of curvature/straight side length on lateral deflection and x-directional bending moment is noted in B.C-2. As open angle increases, B.C-1 and B.C-3 almost agree and B.C-2 approaches B.C-4.

• Structural Engineering and Mechanics
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• v.24 no.6
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• pp.709-725
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• 2006

In this paper the buckling and post-buckling behavior of slender bars under self-weight are studied. In order to study the post-buckling behavior of the bar, a geometrically exact formulation for the non-linear analysis of uni-directional structural elements is presented, considering arbitrary load distribution and boundary conditions. From this formulation one obtains a set of first-order coupled nonlinear equations which, together with the boundary conditions at the bar ends, form a two-point boundary value problem. This problem is solved by the simultaneous use of the Runge-Kutta integration scheme and the Newton-Raphson method. By virtue of a continuation algorithm, accurate solutions can be obtained for a variety of stability problems exhibiting either limit point or bifurcational-type buckling. Using this formulation, a detailed parametric analysis is conducted in order to study the buckling and post-buckling behavior of slender bars under self-weight, including the influence of boundary conditions on the stability and large deflection behavior of the bar. In order to evaluate the quality and accuracy of the results, an experimental analysis was conducted considering a clamped-free thin-walled metal bar. As this kind of structure presents a high index of slenderness, its answers could be affected by the introduction of conventional sensors. In this paper, an experimental methodology was developed, allowing the measurement of static or dynamic displacements without making contact with the structure, using digital image processing techniques. The proposed experimental procedure can be used to a wide class of problems involving large deflections and deformations. The experimental buckling and post-buckling behavior compared favorably with the theoretical and numerical results.

• Progress in Medical Physics
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• v.26 no.3
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• pp.178-184
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• 2015

The Markus ionization chamber(R) is a small plane parallel ionization chamber widely used in clinical electron beam dosimetry. Plane parallel chambers were recommended for low energy electron dosimetry with the beam quality at $R_{50}<4.0g/cm^2$ (${\bar{E}}{\approx}10MeV$) according to TRS-398 protocol. However, the quality correction factors ($k_{Q,Q_0}$) of the Markus chamber was not presented in TRS-398 protocol for electron beam quality at $R_{50}<2.0g/cm^2$ (${\bar{E}}{\approx}4MeV$). In this study, the $k_{Q,Q_0}$ factors of the Markus chambers (PTW-34045) for beam qualities at $R_{50}=1.0$, 1.4, 2.0, 2.5, 3.0, and $5.0g/cm^2$ were determined by Monte Carlo calculations (DOSRZnrc/EGSnrc) and the dosimetric formalism of quality correction factor. The derived $k_{Q,Q_0}$ values were evaluated using the produced data based on TRS-398 and TG-51 protocols and known values for the Markus chamber.