• 대한수학회지
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• 제44권2호
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• pp.407-442
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• 2007

The study of Euclidean submanifolds with finite type "classical" Gauss map was initiated by B.-Y. Chen and P. Piccinni in [11]. On the other hand, it was believed that for spherical sub manifolds the concept of spherical Gauss map is more relevant than the classical one (see [20]). Thus the purpose of this article is to initiate the study of spherical submanifolds with finite type spherical Gauss map. We obtain several fundamental results in this respect. In particular, spherical submanifolds with 1-type spherical Gauss map are classified. From which we conclude that all isoparametric hypersurfaces of $S^{n+1}$ have 1-type spherical Gauss map. Among others, we also prove that Veronese surface and equilateral minimal torus are the only minimal spherical surfaces with 2-type spherical Gauss map.

• 한국통신학회논문지
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• 제31권12C호
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• pp.1129-1134
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• 2006

In this paper, we analyze the cycle structure of punctured finite-length RA-type LDPC codes and design interleavers which have good memory efficiency and avoid short cycles. Furthermore, we introduce the check-node merging scheme for punctured finite-length RA-type LDPC codes and design simple interleavers. Simulation results show that punctured finite-length RA-type LDPC codes using the proposed simple interleavers have better performance than those with random and S-random interleavers.

• 대한수학회지
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• 제41권2호
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• pp.379-396
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• 2004

In this article, we study rotation surfaces in the 4-dimensional pseudo-Euclidean space E$_2$$^4$. Also, we obtain the complete classification theorems for the flat rotation surfaces with finite type Gauss map, pointwise 1-type Gauss map and an equation in terms of the mean curvature vector. In fact, we characterize the flat rotation surfaces of finite type immersion with the Gauss map and the mean curvature vector field, namely the Gauss map of finite type, pointwise 1-type Gauss map and some algebraic equations in terms of the Gauss map and the mean curvature vector field related to the Laplacian of the surfaces with respect to the induced metric.

• 소음진동
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• 제9권1호
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• pp.49-59
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• 1999

The mechanism of Stewart platform has many advantages for kinematic analysis and control. Thus there have been many research about employing this mechanism in the new type of machine tool. Since the vibration caused during the manufacturing process has a severely adverse effect on the machining precision. it is very important to enhance the vibrational characteristics. However. it is not easy to use finite element model for the vibration analysis. That is because the vibration behaviors of the structure vary in a complicated manner according as the length of links varies. In this paper, a Stewart platform type of machine tool is modeled in finite element method and then updated by using the experimental modal data. Finally. the static and dynamic characteristics of the finite element model are predicted and then discussed.

• Journal of the Korean Wood Science and Technology
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• 제23권3호
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• pp.8-15
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• 1995

This analytical study was carried out to make quality and productivity up in designing the frame-type furniture with semi-rigid joint by understanding the mechanical and structural behavior of the joint and by evaluating the validity of application of the time-saving Finite Element Method to its structural analysis. Slope deflection equation for rigid joint was modified to describe the moment-rotation behavior of semi-rigid joint and the joint stiffness factor(Z) could be calculated to lessen the experimental expense. It was proved that Finite Element Analysis with imaginary elements having equivalent MOE to the semi-rigid joint could be the alternative method for the structural analysis of the frame-type furniture, comparing the internal rotation of the 2-dimensional beam-to-column model with two-pin(wooden dowel) from the finite element method with other available theoretical and experimental rotation value.

• 한국압력기기공학회 논문집
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• 제13권1호
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• pp.84-91
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• 2017

This paper is proposed to select the optimal finite element type in finite element analysis. Based on the NUREG reports, static analyses were performed using a commercial analysis program, $ABAQUS^{TM}$. In this study, we used a nonlinear kinematic hardening model proposed by Chaboche. The analysis result of solid elements by inputting the same material constants was different from the results of the NUREG report. This is resulted from the difference between shell element and solid element. Therefore, the material constants that have similar result to the experimental result were determined and compared according to element type. In case of using solid element for efficient finite element analysis, we confirmed that the use of C3D8I element type(incompatible mode 8-node linear brick element) leads the accurate result while reducing the analysis time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.674-677
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• 2002

In this paper, two kinds of windmill type motors which have a disk shape and a ring shape piezoelectric ceramics were studied. And characteristics of two models were compared with each others. A windmill type ultrasonic motor is composed of a stator, a rotor, and a ball bearing. The stator is made of a piezoelectric ceramics and two metals endcaps. When the piezoelectric ceramics vibrate, displacement of torsonal vibration appear at metal endcaps. The motor with 11.0[mm] diameter was studied by finite element analysis. The voltage of 100[V] was supplied at each model. Resonance frequency of 206.875[KHz] was obtained at the disk type, but ring type was 137.562[KHz]. The maximum torsonal displacement of $1.112[{\mu}m]$ was obtained at the disk type, but ring type was $1.698[{\mu}m]$.

• 대한수학회논문집
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• 제12권1호
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• pp.79-86
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• 1997

It is well-known that a null 2-type surface in 3-dimensional Euclidean space $E^#$ is an open portion of circular cylinder. In this article we prove that a surface with 2-type and 1-type Gauss map in $E^3$ is in fact of null 2-type and thus it is an open portion of circular cylinder.

• Korean Journal of Mathematics
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• 제20권2호
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• pp.185-191
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• 2012

Let D be an integral domain and SF(D) be the set of star operations of finite type on D. We show that if ${\mid}SF(D){\mid}$ < ${\infty}$, then every maximal ideal of D is a $t$-ideal. We give an example of integrally closed quasi-local domains D in which the maximal ideal is divisorial (so a $t$-ideal) but ${\mid}SF(D){\mid}={\infty}$. We also study the integrally closed domains D with ${\mid}SF(D){\mid}{\leq}2$.

• 대한수학회지
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• 제36권4호
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• pp.773-785
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• 1999

Shifts of finite type are represented by nonnegative integral square matrics, and conjugacy between two shifts of finite type is determined by strong shift equivalence between the representing nonnegative intergral square matrices. But determining strong shift equivalence is usually a very difficult problem. we develop splittings and amalgamations of nonnegative integral matrices, which are analogues of those of directed graphs, and show that two nonnegative integral square matrices are strong shift equivalent if and only if one is obtained from a higher matrix of the other matrix by a series of amalgamations.