• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.303-306
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• 1997

In the case of a cooled air cooling applied to angular contact ball bearings in a high speed spindle unit,the heat generated heat in bearings is removed and the temperature of inner ring is decreased.. Therefore it is possible to increase the speed of spindle units.

• Communications of the Korean Mathematical Society
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• v.32 no.4
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• pp.991-997
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• 2017

We classify the extreme, exposed and smooth symmetric 3-linear forms of the unit ball of ${\mathcal{L}}_s(^3l^2_{\infty})$, respectively.

• Bulletin of the Korean Mathematical Society
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• v.29 no.2
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• pp.285-293
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• 1992

• Kyungpook Mathematical Journal
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• v.54 no.3
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• pp.341-347
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• 2014

We classify the exposed symmetric bilinear forms of the unit ball of $\mathcal{L}_s(^2d_*(1,{\omega})^2)$.

• Communications of the Korean Mathematical Society
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• v.36 no.4
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• pp.651-669
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• 2021

In this paper, we investigate some basic results on the slice regular Besov spaces of hyperholomorphic functions on the unit ball 𝔹. We also characterize the boundedness, compactness and find the essential norm estimates for composition operators between these spaces.

• Bulletin of the Korean Mathematical Society
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• v.56 no.2
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• pp.319-331
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• 2019

On the weighted Dirichlet space, by the Sobolev's embedding theorem, we characterize the compactness for operators which are finite sums of products of several Toeplitz operators. Moreover, the essential spectrum of Toeplitz operator is characterized.

• Journal of the Chungcheong Mathematical Society
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• v.34 no.3
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• pp.307-316
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• 2021

We provide a gap theorem of Simons' type for free boundary minimal and constant mean curvature surfaces in the unit ball in 3-dimensional Euclidean space.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.129-134
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• 2004

In this study, we investigated the effect of a nitrogen atom on the amorphization of V-Fe alloy through solid-gas reaction during mechanical alloying (MA). MA by planetary ball mill of $V_{70}Fe_{30}$ elemental powders was carried out under the nitrogen gas atmosphere. Amorphization has been observed after 160 hours of ball milling in this case. The DSC spectrum for the mechanically alloyed ($V_{70}Fe$_{30}$)_{0.89}N_{0.11}$ powders exhibits a sharp exothermic peak due to crystallization at about $600^{\circ}C$. Structural transformation from the bcc crystalline to amorphous states was also observed through X-ray and neutron diffractions. We take a full advantage of a negligibly small scattering length of the V atom in the neutron diffraction measurement. During amorphization process the octahedral unit, which is typical of a polyhedron formed in any crystal structures, was preferentially destroyed and transformed into the tetrahedral unit. Futhermore, neutron diffraction measurements revealed that a nitrogen atom is selectively situated at a center of the polyhedron formed by V atoms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.84-89
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• 2014

Data-driven method for fault diagnostics system often use machine learning technique. To use such technique proper signal processing should be implemented such as time synchronous averaging (TSA) for ball bearing systems. However, for journal bearing diagnostics systems not much has been researched, and yet a proper signal processing method has not been studied. Therefore, in this research an optimal datum unit for a reliable journal bearing diagnostics system along with angular resampling process is being suggested. Before extracting time and frequency domain features, angular resampling is applied to each cycle of vibration data. As to preserve the characteristics of vibration signal, averaging method is replaced by finding the optimal datum unit which strengthens statistical characteristics of vibration signal. Then 20 features were extracted for various cases, and those features are being evaluated by two criteria, separability and classification accuracy.

• The Korean Journal of Physiology
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• v.1 no.1
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• pp.91-101
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• 1967

The maximal oxygen intake (MOI) was determined in 54 males (23 nonathletes, 10 basketball players, 8 hand ball players, 7 weight lifters and 6 long distance runners) and in 49 females (24 non-athletes, 16 basketball players and 9 volley ball players) by using a treadmill method outlined in Part I of the present investigation and the following results were obtained: (1) The maximal aerobic work capacity varied from the lowest value of 1,008 kg-m/min in female non-athletes to the highest value of approximately 2,000 kg-m/min in male basketball players and long distance runners. Values of other groups varied from 1,400 kg-m/min in male non-athletes and female athletes to 1,800 kg-m/min in male hand ball players. (2) The MOI per unit body weight varied from the lowest value of 41.3 ml/min/kg in female non-athletes to the highest value of 67.6 ml/min/kg in male long distance runners. Values of other groups were in the order of 47 to 55 ml/min/kg. (3) The heart rate during maximal aerobic work performance varied from the lowest value of approximately 180 per min in female basketball players and male long distance runners to the highest value of 190 or above in nonathletes of both sexes. (4) An estimate of oxygen debt as measured during 15 minutes following the maximal work was 3.841 in female non-athletes, 4.681 in female athletes, 5.561 in male non-athletes and 6.321 in male athletes. These results indicate that the MOI per unit body weight as well as the oxygen debt of Korean non-athletes were comparable to, while corresponding values of Korean athletes were considerably lower than, those of other countries such as Japan, the United States of America and Europe.