• Communications of the Korean Mathematical Society
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• v.9 no.4
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• pp.905-915
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• 1994

Let $M_g$ be the moduli space of isomorphism classes of genus g smooth curves. It is a quasi-projective variety of dimension 3g - 3, when $g > 2$. It is known that a complete subvariety of $M_g$ has dimension $< g-1 [D]$. In general it is not known whether this bound is rigid. For example, it is not known whether $M_4$ has a complete surface in it. But one knows that there is a complete curve through any given finite points [H]. Recently, an explicit example of a complete curve in moduli space is given in [G-H]. In [G-H] they constructed a complete curve of $M_3$ as an intersection of five hypersurfaces of the Satake compactification of $M_3$. One way to get a complete curve of $M_3$ is to find a complete one dimensional family $p : X \to B$ of plane quartics which gives a nontrivial morphism from the base space B to the moduli space $M_3$. This is because every non-hyperelliptic smooth curve of genus three can be realized as a nonsingular plane quartic and vice versa. This paper has come out from the effort to find such a complete family of plane quartics. Since nonsingular quartics form an affine space some fibers of p must be singular ones. In this paper, due to the semistable reduction theorem [M], we search singular plane quartics which can occur as singular fibers of the family above. We first list all distinct plane quartics in terms of singularities.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.295-299
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• 2012

We investigated the crystal and the optical properties of GaN-based blue light emitting diodes (LEDs) which were simultaneously grown on c-plane (0001) and semipolar (11-22) GaN templates by using metal-organic chemical vapor deposition (MOCVD). The X-ray rocking curves (XRCs) full width at half maximums (FWHMs) of c-plane (0001) and semipolar (11-22) GaN templates were 275 and 889 arcsec, respectively. In addition, high-resolution X-ray ω-2θ scan showed that satellite peaks of semipolar (11-22) InGaN quantum-wells (QWs) was weaker and broader than that of c-plane (0001) InGaN QWs, indicating that the interface quality of c-plane (0001) QWs was superior to that of semipolar (11-22) QWs. Photoluminescence (PL) and electroluminescence (EL) results showed that the emission intensity and the FWHMs of polar c-plane (0001) LED were much higher and narrower than those of semipolar (11-22) LED, respectively. From these results, we believed that relative poor crystal quality of semipolar (11-22) GaN template might give rise to the poor interfacial quality of QWs, resulting in lower output power than conventional c-plane (0001) GaN-based LEDs.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.133-140
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• 2009

Presented in this paper is a method to generate round-endmill toolpaths for sculptured surfaces represented as a triangular mesh model. The proposed method is applicable in toolpath generation for ball-endmills and flat-endmills because the round-endmill is a generalized tool in three-axis NC (numerical control) milling. The method uses a wireframe model as the offset model that represents a cutter location surface. Since wireframe models are relatively simple and fast to calculate, the proposed method can process large models and keep high precision. Intersection points with the wireframe offset model and a tool guide plane are calculated, and intersection curves are constructed by tracing the intersection points. The final step of the method is extracting regular curves from the intersection curves including degenerate and self-intersected segments. The proposed method is implemented and tested, and a practical example is presented.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.328-332
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• 2000

Following the method described in ASTM E1737, J resistance curves are measured for Cr-Mo steel SA387, and Cr steel A240 which are used as piping materials in nuclear industry. Crack driving force diagrams are generated in order to find out instability points in crack growth. The $J_{appl}$ curves, which are used in the crack driving force diagram, are obtained from EPRI J estimation method and the finite element analysis. Crack growth instability points are plotted in load-crack length plane and the results are discussed.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.144-149
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• 1998

A new method to calculate the spin reorientation angle of cone anisotropy from magnetization curves of magnetically aligned powder is suggested. The spin reorientation angle of polycrystalline $Nd_2Fe_{14}B$ determined by this method coincided with the results obtained from torque magnetometry or magnetization measurements on single crystal. The underestimation of about 9% is expected if the basal plane anisotropy is neglected in determination of the spin reorientation angle of $Nd_2Fe_{14}B$ at 4.2 K.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.809-810
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• 2005

• Communications of the Korean Mathematical Society
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• v.38 no.4
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• pp.1261-1269
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• 2023

For a fixed parametrization of a curve in an orientable two-dimensional Riemannian manifold, we introduce and investigate a new frame and curvature function. Due to the way of defining this new frame as being the time-dependent rotation in the tangent plane of the standard Frenet frame, both these new tools are called flow.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1460-1468
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• 1995

The objective of this paper is to evaluate the material properties of SA106 Gr. C carbon steel and its associated weld manufactured for main steam system of Yonggwang 3,4 nuclear generating stations. A total of 43 tensile and 35 fracture toughness tests were performed and the effects of various parameters such as pipe size, crack plane orientation, test temperature, welding on material properties were discussed. Test results show that the effects of crack plane orientation, test temperature, and welding on fracture toughness were significant while the effects of pipe size, specimen orientation and test temperature on tensile properties were negligible. Especially the dependence of J-R curves on the crack plane orientation appears to be the characteristics of carbon steel.

• Journal of KSNVE
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• v.10 no.5
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• pp.849-858
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• 2000

In this paper the chaotic out-of-plane vibrations of the uniformly curved pipe with pulsating flow are theoretically investigated. The derived equations of motion contain the effects of nonlinear curvature and torsional coupling. The corresponding nonlinear ordinary differential equation is a type of nonhomogenous Hill's equation . this is transformed into the averaged equation by averaging theorem. Bifurcation curves of chaotic motion are obtained by Melnikov's method and plotted in several cases of frequency ratios. The theoretically obtained results are demonstrated by numerical simulation. And strange attractors are shown.

• Geomechanics and Engineering
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• v.4 no.1
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• pp.19-37
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• 2012

This paper presents the results of analytical and numerical analyses of the effects of performing a pressuremeter test or driving a pile in clay. The geometry of the problem has been simplified by the assumptions of plane strain and axial symmetry. Pressuremeter testing or installation of driven piles has been modelled as an undrained expansion of a cylindrical cavity. Stresses, pore water pressures, and deformations are found by assuming that the clay behaves like normally consolidated modified Cam clay. Closed-form solutions are obtained which allow the determination of the principal effective stresses and the strains around the cavity. The analysis which indicates that the intermediate principal stress at critical state is not equal to the mean of the other two principal stresses, except when the clay is initially isotropically consolidated, also permits finding the limit expansion and excess pore water pressures by means of the Almansi finite strain approach. Results are compared with published data which were determined using finite element and finite difference methods.