• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.245-255
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• 1997

The thermal characteristics of a disk such as temperature distribution, thermal behaviours and thermal stress during a braking operation has been analyzed for a high-speed train using the finite element method. The maximum stress for a pad loaded against a disk was occurred at the trailing and leading edges of the disk pad at the underlayer-backplate interface. The FEM results indictate that the thermal characterisics of the spot type pad shows good performance compared with those of the flat type pad. Thus, the spot type pad in brake system may be recommended for the high-speed train system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1501-1510
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• 2004

The pumping characteristics of a single-stage disk-type drag pump (DTDP) are calculated for the variation of the vertical clearance between a rotor and stator by the three-dimensional direct simulation Monte Carlo (DSMC) method. The gas flow mainly belongs to the molecular transition flow region. Spiral channels of a DTDP are cut on the both the upper and lower sides of a rotating disk, but a stationary disk is planar. The interaction between molecules is described by the variable hard-sphere model. The no time counter method is used as a collision sampling technique. The vertical clearance has a significant effect on the pumping performance. Experiments are performed under the outlet pressure range of 0.4∼533 Pa. When the numerical results are compared with the experimental data, the numerical results agree well quantitatively

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.168-171
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• 2005

In this paper, disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of traveling elastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumferenceof elastic disk bonded onto the piezoelectric ceramic disks is driven in both directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disk to bond onto both surfaces of a elastic disk, respectively. As the results, the diameter of elastic body is increased, the resonant frequency is decreased. The resonant frequency of the stator is about 92 kHz, which is composed with piezoelectric ceramic disks of 28 mm in diameter and 2 mm in thickness, and an elastic body of 32 mm in diameter and 2 mm in thickness. A driving voltage of 20 Vpp produces 200 rpm with a torque of 1Nm and an efficiency of about 10 %.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1470-1477
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• 2016

This study has designed and evaluated the safety of watertight damper for Offshore Rigs. The watertight damper is an improved design for conventional DN 350 butterfly valve. Numerical analysis has been performed to investigate the safety factor and seat leakage of the designed 3-type disk dampers. The structure analysis results present the deformations, the equivalent stresses and the safety factor. It was confirmed that the designed disk, rib-disk and streamlined disk of watertight damper are safe enough in maximum operating pressure of 0.98MPa. The results show that the disk damper had the smallest maximum deformations and stress among 3-type disk dampers and the safety factor was 4.3. Therefore it is confirmed that the disk damper has the most excellent strength. Also linear static structural analysis was individually conducted for disk and body. The results show that the maximum disk deformation was larger than the body deformation, Therefore the disk damper is causes no seat leakage.

• Journal of The Korean Astronomical Society
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• v.54 no.2
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• pp.71-88
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• 2021

We use N-body/hydrodynamic simulations to study the evolution of the spin of a Milky Way-like galaxy through interactions. We perform a controlled experiment of co-planar galaxy-galaxy encounters and study the evolution of disk spins of interacting galaxies. Specifically, we consider cases where the late-type target galaxy encounters an equally massive companion galaxy, which has either a late or an early-type morphology, with a closest approach distance of about 50 kpc, in prograde or retrograde sense. By examining the time change of the circular velocity of the disk material of the target galaxy from each case, we find that the target galaxy tends to lose the spin through prograde collisions but hardly through retrograde collisions, regardless of the companion galaxy type. The decrease of the spin results mainly from the deflection of the orbit of the disk material by tidal disruption. Although there is some disk material which gains the circular velocity through hydrodynamic as well as gravitational interactions or by transferring material from the companion galaxy, it turns out that the amount of the material is generally insufficient to increase the overall galactic spin under the conditions we set. We find that the spin angular momentum of the target galaxy disk decreases by 15-20% after a prograde collision. We conclude that the accumulated effects of galaxy-galaxy interactions will play an important role in determining the total angular momentum of late-type galaxies.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.620-622
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• 1992

Magnetic characteristics of a brushless disk type motor has been analyzed taking into account the magnetization distribution in the rotor magnet. This paper describes a method for calculating the 3D flux density in the air gap and calculates the induced voltage of the windings and the torque betweens the permanent magnet and the amateur current.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.204-206
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• 1997

The disk type Single-phase Switched Reluctance Motor has advantages of constructional simplicity, robustness and low cost. In this paper, We analyze the 3-D model of DSPSRM(Disk type Single-Phase Switched Reluctance Motor) by Finite Element Method for finding optimal design model.

• Journal of Astronomy and Space Sciences
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• v.4 no.1
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• pp.11-23
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• 1987

In dward nova we assume the primary star as a white dwarf and the secondary as the late type star which filled Roche lobe. Mass flow from the secondary star leads to the formation of thin accretion disk around the white dwarf. We use the $\alpha$ parameter as viscosity to maintain the disk form and propose that the outburst in dwarf nova cause the step increase of source term. With these assumptions we solve the basic equations of stellar structure using New-Raphson method. We show the physical parameters like temperature, density, pressure, opacity, surface density, height and flux to the radius of disk. Changing the value of $\alpha$, we compare several parameters when mass flow rate is constant with those of when luminosity of disk is brightest. At the same time, we obtain time-dependent variations of luminosity and mass of disk. We propose the suitable range of $\alpha$is 0.15-0.18 to the difference of luminosity. We compare several parameters of disk with those of the normal late type stars which have the same molecular weight of disk. These show the temperature and pressure of disk are similar to those of normal stars but the density of disk is lower. Maybe the outburst in dwarf nova is due to the variation of the $\alpha$ value instead of increment of mass flow from the secondary star.

• Journal of Institute of Convergence Technology
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• v.5 no.2
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• pp.1-6
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• 2015

Flying Saucer(flying disk type UFO) is a rotating disk that flies through the air. Thus, the aerodynamical features of the Flying Saucer can be estimated by taking a close look on the aerodynamics of the rotating disk. In the present paper, the aerodynamics of the rotating disk are reviewed focusing on the their application to the possibility of the UFO type VTOL aircraft. Finally, a combination of Avro Aircraft and Frisbee concepts is suggested as a possible new UFO type VTOL aircraft.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.669-672
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• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 (rpm) when input voltage was 55 (Vrms) and applied frequency 160.4 IkHz] under pre-load.