• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.125-132
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• 2002

This paper shows an experimental magnetic levitation table using one degree-of-freedom active control. The magnetic levitation table using repulsions of permanent magnets was theoretically presented already. Thus the objective of this paper is to prove stable levitation with only one degree-of-freedom active control experimentally. For the design of the system, at first, permanent magnets are selected. Secondly, the spring constants of the virtual spring are obtained by simulation. Thirdly, the moving magnets are arranged using a stable layout relation. Fourthly, a linear voice coil motor is designed. Finally, the magnetic levitation system is manufactured. The phenomenon of stable levitation in the manufactured table is proven by means of dynamic time and frequency responses. The differences between the theoretical natural frequencies and experimental ones are analyzed. Also, stable range in the control direction is shown experimentally.

• Communications of the Korean Mathematical Society
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• v.31 no.3
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• pp.423-431
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• 2016

Images and inverse images of (almost) stable cubic sets are discussed. We show that the image and inverse image of stable cubic sets are also stable. Conditions for the image of almost cubic sets to be an almost cubic set are provided. The complement, the P-union and the P-intersection of (inverse) images of (almost) stable cubic sets are considered.

• Journal of the Korean Mathematical Society
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• v.58 no.2
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• pp.501-523
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• 2021

We study the geometry of the moduli space of elliptic stable maps to projective space. The main component of the moduli space of elliptic stable maps is singular. There are two different ways to desingularize this space. One is Vakil-Zinger's desingularization and the other is via the moduli space of logarithmic stable maps. Our main result is a proof of the direct geometric relationship between these two spaces. For degree less than or equal to 3, we prove that the moduli space of logarithmic stable maps can be obtained by blowing up Vakil-Zinger's desingularization.

• Journal of Korean Physical Therapy Science
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• v.3 no.2
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• pp.963-973
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• 1996

The purpose of this study was to evaluate and compare the limits of stability(LOS) at different sensory conditions in normal 20 years of age. The LOS was measured at stable surface, and unstable surface and the subjects stood with the feet contacted and 4 inches between the feet with the eyes open and the eyes closed. In this study, 20 physical therapy major subjects were evaluated at Wonkwang Public Health Junior College. In this study applied the paired t-test, and Kruskal-Wallis 1-way ANOVA to determine the statistical significance of results at 0.01 level of significance. The results were as follows: 1. The mean of lateral limits of stability was b.67 degree at stable surface with the eyes open and standing with the feet contacted. 2. The mean of anteroposterior limits of stability was 9.78 degree at stable surface with the eyes open and standing with the feet contacted. 3. The mean of lateral limits of stability was 15.10 degree at stable surface with the eyes open and standing with 4 inches between the feet. 4. The mean of anteroposterior limits of stability was 11.72 degree at stable surface with the eyes open and standing with 4 inches between the feet. 5. The anterior-posterior and lateral limits of stability significantly decreased with the eyes closed(p<0.01). 6. The anterior-posterior and lateral limits of stability significantly decreased at unstable surface(p<0.01). 7. There was no significant difference of limits of stability as the height and foot length(p>0.01).

• Journal of the Chungcheong Mathematical Society
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• v.16 no.1
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• pp.113-121
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• 2003

This paper is concerned with some properties of stable domains and limit functions. Using the relationship between cycles of periodic stable domains and orbits of critical points and using the Sullivan theorem [19], we prove that the value of a constant limit function in some stable domain for a rational function f of degree at least two lies in the closure of the set of critical orbits of f.

• Honam Mathematical Journal
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• v.29 no.4
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• pp.649-652
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• 2007

In this note we provide a generalization of the Schur-Cohn test. If $p_n$ be a polynomial of degree n then $p_n$ is a reduced-stable polynomial whose reduced degree is equal to r if and only if $D_n\;:=\;P_nQ_n^{-1}$ is a contraction such that rank ($I-D_nD_n^*$) = r.

• Structural Engineering and Mechanics
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• v.4 no.5
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• pp.529-540
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• 1996

The dynamic buckling mechanism of a single-degree-of-freedom dissipative/nondissipative gradient system is thoroughly studied, employing energy criteria. The model is chosen in such a manner, that its corresponding static response is associated with all types of distinct critical points. Under a suddenly applied load of infinite duration, it is found that dynamic buckling, occurring always through a saddle, leads to an escaped motion, which is finally attracted by remote stable equilibrium positions, belonging sometimes also to complementary paths. Moreover, although the existence of initial imperfection changes the static behaviour of the system from limit point instability to bifurcation, it is established that the proposed model is dynamically stable in the large, regardless of the values of all other parameters involved.

• Journal of the Chungcheong Mathematical Society
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• v.36 no.1
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• pp.1-8
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• 2023

Let C be a smooth projective curve and W a symplectic bundle over C of degree w. Let π : 𝕃𝔾(W) → C be the relative Lagrangian Grassmannian over C and S_d(W) be the space of Lagrangian subbundles of degree w -d. Then Kontsevich's space ${\bar{\mathcal{M}}}_g$(𝕃𝔾(W), β_d) of stable maps to 𝕃𝔾(W) is a compactification of S_d(W). In this article, we give an upper bound on the dimension of ${\bar{\mathcal{M}}}_g$(𝕃𝔾(W), β_d), which is an analogue of a result in [8] for the relative Lagrangian Grassmannian.

• Communications of the Korean Mathematical Society
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• v.34 no.1
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• pp.113-125
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• 2019

In this paper, we introduce the elimination ideal $I_D(G)$ associated to a simple finite graph G. We obtain the upper bound of Castelnuovo-Mumford regularity of elimination ideal for various classes of graphs.

• Journal of the Korea Society of Computer and Information
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• v.8 no.1
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• pp.7-12
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• 2003

Because some systems limit the supported maximal degree, the degree reduction of NURBS is necessary in Parametric curves and surfaces of the different geometric modeling systems. Therefore an approximate degree reduction method of NURBS curves was introduced in this research. Also the existing Eck's B$\'{e}$zier degree reduction method and knot removal algorithm were used to reduce data in the degree reduction process. Finally we found that this method was stable, efficient for implementations, and easy to use algorithms.