• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제8권1호
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• pp.1-9
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• 2004

We knew attractive qualities of a rotation number for an analytic diffeomorphism, for example, Arnold tongues and staircase. Numerical computer simulation let us know easily that the pattern of rotation number of a non analytic homeomorphism is similar to its of an analytic homeomorphism for some cases. Also we define new rotation function and investigate it's properties.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2248-2253
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• 2008

A numerical study on oscillatory thermocapillary flow in half-zone has performed to understand the effect of axial rotation. 2d unsteady code is developed to observe the onset of oscillation. 2cs Silicone oil with Prandtl number of 26.5 is used as a working fluid. The critical temperature difference at onset of oscillation is investigated under the different aspect ratios and rotation modes. It is shown that the onset of oscillation is delayed when aspect ratio reduces and rotating speed increases. The oscillatory flow is strongly reduced under top rotation and co-rotation modes, while it is augmented under bottom rotation and counter-rotation modes. It is thought that interaction between return flow and bottom wall is important to explain the oscillatory flow.

• Earthquakes and Structures
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• 제11권6호
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• pp.1027-1041
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• 2016

Different incident angles of ground motions have been considered to evaluate the relationship between floor rotation and torsional irregularity coefficient. The issues specifically addressed are (1) variability in torsional irregularity coefficient and floor rotations with varying incident angles of ground motion (2) contradictory relationship between floor rotation and torsional irregularity coefficient. To explore the stated issues, an evaluation based on relative variation in seismic response quantities of linear asymmetric structure under the influence of horizontal bi-directional excitation with varying seismic orientations has been carried out using response history analysis. Several typical earthquake records are applied to the structure to demonstrate the relative variations of floor rotation and torsional irregularity coefficient for different seismic orientations. It is demonstrated that (1) Torsional irregularity coefficient (TIC) increases as the story number decreases when the ground motion is considered along reference axes of the structure. For incident angles other than structure's reference axes, TIC either decreases as the story number decreases or there is no specific trend for TIC. Floor rotation increases in proportion to the story number when the ground motion is considered along reference axes of structure. For incident angles other than structure's reference axes, floor rotation either decreases as the story number increases or there is no specific trend for floor rotation and (2) TIC and floor rotation seems to be approximately inversely proportional to each other when the ground motion is considered along reference axes of the structure. For incident angles other than structure's reference axes, the relationship can even become directly proportional instead of inversely proportional.

• 한국가시화정보학회지
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• 제10권3호
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• pp.25-29
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• 2012

This paper introduces a new parameter to design the $2{\times}2$ microfluidic centrifuge with single flow rotation positioned at the center of microchamber. The dimensional centrifugal acceleration momentum flux which is defined as the interfacial momentum flux divided by distance from the center of the chamber explains the flow rotation and its threshold provides a reference to expect single flow rotation. Through the numerical and experimental visualization of the flow rotation, the number and position of flow rotation in the $2{\times}2$ microfluidic centrifuge were examined. At a channel width of $50{\mu}m$ and chamber width of $250{\mu}m$, single flow rotation was obtained over at a Reynolds number of 300, while at a channel width of $100{\mu}m$ and chamber width of $500{\mu}m$, single flow rotation did not appear. The numerical analysis showed that the threshold centrifugal acceleration momentum flux to obtain single flow rotation was $3500kg/m{\cdot}s^2$.

• 제어로봇시스템학회논문지
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• 제6권5호
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• pp.376-382
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• 2000

A problem of relevant interest to some industries is that of the optimum two-dimensional layout. In this problem, one is given a number of rectangular sheets and an order for a specified number of each of certain types of two-dimensional regular and irregular shapes. The aim is to cut the shapes out of the sheets in such a way as to minimize the amount of waste produced. In this paper, we propose a genetic algorithms using rotation parameters by which the best pattern of layout is found.

• Journal of the Korean Statistical Society
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• 제29권1호
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• pp.29-44
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• 2000

In this paper, we consider one-level rotation designs with finite rotation groups such that the design satisfies two basic requirements: all rotation groups are included in any given survey period, and overlapping rates depend only on the time lag. First we present the necessary number of rotation groups and a rule for the length of time the sample units are to be in or out of the sample to satisfy the requirements. Second, an algorithm is presented to put rotation groups to proper positions in a panel in order to include all finite rotation groups for any survey period. Third, we define an one-level rotation pattern which is invariant in the survey period and has useful properties in practical sense.

• 전기학회논문지
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• 제59권10호
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• pp.1862-1868
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• 2010

A corona motor, as one of a powerful cooling means of microelectronic devices, has been employed because of its very simple structure of no coils and no brushes. In this paper, the effect of polarity of applied voltage and the number of blade corona electrodes on the fundamental properties of rotation of the motor was investigated. The I-V and rotation characteristics of the blade corona electrode were significantly different from the different polarities of applied voltages and the blade corona electrode numbers, due to the different space charge effect resulted by the different migration mobility of the positive and negative ions generated near the blade corona electrode tip of the rotor of the motor. The rotation speed of the motor was influenced significantly by the polarity of corona discharge, the number of blades, and mass of rotor. At the same corona current, an effective rotation can be obtained with the positive corona caused by the lower ion mobility. On the other hand, the higher rotation speed can be obtained with the negative corona resulted from its higher corona current. The highest rotation speed and energy efficiency can be obtained with the rotor having 4 blades.

• Korean Journal of Acupuncture
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• 제30권2호
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• pp.88-96
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• 2013

Objectives : In the acupuncture treatment of Korean Medicine, the Tonifying or Purging depending on how many times the needle is rotated has been used widely. However, there is little evidence about the optimal number of rotation. This study, therefore, was aimed to investigate the optimal number of rotation. Methods : Heart rate variation was measured before and after exercise in 20 healthy adults. Acupuncture was performed at PC6 immediately after exercise according to the protocol of each group without remaining. Pre-exercise and post-exercise measurements were compared and the rotation number that produced statistically significant difference was investigated. Results : Significant differences were found in the heart rate variation and R-R interval Average, between non-rotation group (control) and both of 15 times rotation group of tonifying and 6 times rotation group of purging. Conclusions : Significantly effective number of rotation in the effect of PC6 on the HR and RRAv was 15 times in the tonifying and 6 in the purging respectively.

• 대한수학회보
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• 제36권4호
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• pp.707-716
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• 1999

In this pater we study the continuity of rotation numbers of liftings of circle maps with degree one. And apply our result to prove that a positively equicontinuous flow of homeomorphisms on the circle $S^1$ is topologically conjugate to a continuous flow of rotation maps.

• 한국유체기계학회 논문집
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• 제12권1호
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• pp.51-56
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• 2009

The detailed heat transfer coefficient on a rotating dimpled channel were measured using the transient liquid crystal technique. The channel height to dimple diameter was 2, dimple center distance to dimple diameter was 1.5 and channel aspect ratio was 4. Tested Reynolds number based on the channel hydraulic diameter was varied from 15000 to 35000 and corresponding rotation number was ranged from 0.026 to 0.057. Results showed that the Coriolis force by rotation enhanced the heat transfer coefficient on the trailing surface. As the Reynolds number increased, i.e. rotation number decreased, the heat transfer coefficient increased and the thermal performance factor decreased.