• 대한기계학회논문집B
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• 제25권10호
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• pp.1293-1302
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• 2001

It is generally known that radial vane blowers with vaneless diffuser may generate mostly only a rotating stall but backward curved vane blowers may do both an impeller and a diffuser rotating stalls. In this study, it was found from the numerical and experimental results that the diffuser rotating stall does not appear in a radial vane because of the suppression for the diffuser stall appearance by occurring of impeller rotating stall in a large flow rate coefficient. The diffuser rotating stalls occurring when the width of diffuser is broaden fur a backward curved vane blower are classified definitely by the diffuser flow rate coefficient defined by adopting the varying diffuser width.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1161-1169
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• 2007

In this paper, the dynamic stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influence of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating cantilever pipe are derived by using extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the rotating angular velocity of a pipe. Also, the critical flow velocity and stability maps of the rotating pipe system for the variation each parameter are obtained.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.796-799
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• 2002

The stress of the rotating disc with several types of hole was investigated in detail in this paper. Maximum circumferential stress of rotating disc by changing hole shape with same area, were studied using FEM. The results obtained were as follows: 1. The disc which rotates at high speed is subjected to circumferential stress remarkably. 2. When the number of circular holes in rotating disc is four, stress reduction effect is maximum. 3. When shape of holes in rotating disc is cylindrical elongated hole, maximum circumferential stress of the rotating disc decreased most.

• 대한기계학회논문집B
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• 제31권12호
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• pp.1017-1023
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• 2007

This study is intended to analyze the effect of thin ink-film thickness around rotating printing roll on the printing quality in the gravure printing process which is used for making electronics circuit like a RFID tag with a conductive ink. The present work numerically estimates the film thickness around rotating roller partially immersed in ink for which the volume of fluid (VOF) method was adopted to figure out the film formation process around rotating roller. Parameter studies were performed to compare the effect of ink properties (viscosity, surface tension), operating condition (roller rotating speed, initial immersed angle) on the film thickness. The result indicates that the film thickness has a strong dependency on the rotating speed, while the surface tension has negligible effect.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.416-421
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• 2000

The performance of gas turbine engines is affected by instabilities, like as rotating stall and/or surge. Rotating Stall is a transient intermediate stage between normal flow and complete flow breakdown leading to engine surge. Rotating Stall is associated with large amplitude nonaxisymmetric flow variations rotating around the compressor annulus. This paper presents the evolutions of stall propagation in a compressor cascade by numerical analysis. The flow phenomena due to stall cells and propagation speed are examined using 2 dimensional Navier - Stokes equations.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.253-260
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• 2001

Rotating bogie frame will be used in the bogie for the Light Rail Train being developed. In development of the bogie, analyzed were the structural strength and fatigue characteristics of the rotating bogie frame. Defined load cases were applied for the analysis. No part of the rotating bogie frame is subjected to stress beyond the fatigue endurance limits of the material used when grinding the weldment of the lower plate link bend. It is concluded that the rotating bogie frame is considered safe in the view of the structural strength.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.99-105
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• 2009

Crack detection method of a rotating blade was suggested in this paper. A rotating blade was modeled with a cantilever beam connected to a hub undergoing rotating motion. The existence and the location of crack were able to be recognized from the vertical response of end tip of a rotating cantilever beam by employing Discrete Hidden Markov Model (DHMM) and Empirical Mode Decomposition (EMD). DHMM is a famous stochastic method in the field of speech recognition. However, in recent researches, it has been proved that DHMM can also be used in machine health monitoring. EMD is the method suggested by Huang et al. that decompose a random signal into several mono component signals. EMD was used in this paper as the process of extraction of feature vectors which is the important process to developing DHMM. It was found that developed DHMMs for crack detection of a rotating blade have shown good crack detection ability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.382-389
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• 2001

In the present study, local heat transfer rates for co-rotating disks with two modified hubs having ventilation holes are investigated for Rossby number of 0.04, 0.1 and 0.35 to evaluate the influence of incoming flows through hub holes. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients on the rotating disks using the heat and mass transfer analogy. Flow field measurements are conducted using Laser Doppler Anemometry (LDA) and numerical calculations are performed simultaneously to analyze the flow patterns induced by the disk rotation. The basic flow structure in a cavity between co-rotating disks consists of three regions; the solid-body rotating inner region, the outer region with turbulence vortices and the shroud boundary layer region. The heat/mass transfer. rates on the co-rotating disks are very low near the hub due to the solid-body rotation and those increase rapidly in the outer region due to turbulence mixing. The modified hubs with ventilation holes enhances significantly the heat/mass transfer rates on the region near the hub. The results also show that the heat transfer of Hub-2 is superior to that of Hub-1, but Hub-1 is more profitable for destructing the solid-body rotating inner region.

• 한국정밀공학회지
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• 제17권10호
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• pp.83-88
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• 2000

multi-beam optical drive is a method to improve the data transfer rate for the optical disc systems by parallel recording and reading on neighboring multi-tracks. In this paper, the beam rotating actuator, which is necessary for the multi-bean optical disc drive to from beam spots on multi-tracks simultaneously, has been developed. The Voice Coil Motor is used as a drive mechanism for high resolution and small size of the actuator. And rotating guide based on link structure is designed for frictionless and axisless rotation of rotating part including dove prism and for rotating in axis of geometric center of dove prism. The characteristics of the actuator are experimented by laser vibrometer, Polytec OFV1102 and a dynamic analyzer, HP35670A. It shows that the actuator has good linearity, rotating range $\pm0.34^\circ$, minimum rotating angle $0.0066^\circ$and natural frequency 113.9Hz. Therefore the actuator can be applied in a multi-beam optical disc system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.81-84
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• 2000

Rotating machine is used extensively and plays important roles in the industrial field. Therefore when rotating machine get out of order, it is necessary to know reasons then deal with the troubles immediately. So many studies far diagnosis of rotating machine are being done. However by this time most of study has an interest in gaining a high recognition But without considering error $rate^{(1)(2)(3)}$ , it is not desirable enough to apply h the actual application system. If the manager of system receives the result misjudging the condition of rotating machine and takes measures, we would lose heavily. So in order to play the creditable diagnosis, we must consider error rate. T h ~ t is. it must be able to reject the result of misjudgment. This study uses nearest neighbor classifier for diagnosis of rotating $machine^{(4)(8)}$ And the Smith's rejection $method^{(1)}$ used to recognize handwritten charter is done. Consequently creditable diagnosis of rotating machine is proposed.