• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1277-1282
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• 2003

The purpose of the present paper is to investigate the noise and vibration characteristics of externally pressurized air proceeding bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the width of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1028-1033
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• 2003

The purpose of this paper is to investigate the noise and vibration characteristics of externally pressurized air journal bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the length of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the length of the bearing.

• Language and Information
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• v.5 no.2
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• pp.75-86
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• 2001

Generic sentences assert generic properties of single individuals or those of plural individuals. It means the generic quantifier Gen can quantify over single and plural entities. Among the generic meaning information represented in terms of the tripartite structure, the information not in the nuclear scope part, but rather in the restrictor part is related to which individuals generic sentences assert of. The plurality in the nuclear scope part cannot be described by making the generic operator Gen quantify over plural entities: Generic sentences with collective predicates like gather, and those with dependent plurals predicate of generic properties of single individuals. On the contrary, the plural information in restrictor part leads Gen to quantify eve. plural entities.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.47-50
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• 2008

This paper presents a new water-lubricated hybrid sliding bearing for a high speed and high accuracy main shaft system, along with the numerical method used for its design. The porous material for the restrictor and the restriction parameter were chosen based on the special requirements of the water-lubricated bearing. Subsequent numerical calculations give the load capacity, stiffness, and friction power of different forms of water-lubricated bearings. The pressure distribution of the water film in a 6-cavity bearing is shown, based on the results of the numerical calculations. A comparison of oil-lubricated and water-lubricated bearings shows that the latter benefits more from improved processing precision and efficiency. An analysis of the stiffness and friction power results shows that 6-cavity bearings are the preferred type, due their greater stiffness and lower friction power. The average elevated temperature was calculated and found to be satisfactory. The relevant parameters of the porous restrictor were determined by calculating the restriction rate. All these results indicate that this design for a water-lubricated bearing meets specifications for high speed and high accuracy.

• Journal of Korean Association for Spatial Structures
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• v.2 no.1 s.3
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• pp.67-73
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• 2002

Measurement of fluctuating pressure by tube system is carefully designed due to the organ-pipe resonance. It is necessary to correct the pressure before analysis. The three method for correction the distortion fluctuation pressure short tube length and the frequency response functions and insert a restrictor in the tube to increase the damping. The first method is useful when the tube length is short. In second method, the distorted signal through the tubing transformed into the frequency domain, dividing by transfer function and inverse fourier transforming back into the time domain gives the required pressure signal. In this paper three types of tubing which have different length of 100cm, 150cm, 200cm were experimented the distorted signal and correct the distortion signal

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.425-431
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• 1999

Nowadays development of electric and optical devices needs precision more and more. This study focuses on hydrostatic journal bearing of grinding wheel spindle. It presents theoretical analysis about cylinder type self-controlled restrictor to control flux of oil flowing into pockets around the hydrostatic journal bearing. As a result of this analysis, optimal properties to maximize bearing stiffness such as initial cross distance, supply pressure, diameter of two supply holes, pre-load of spring and clearance between spindle and housing can be obtained. Therefore, by using them it is possible to estimate bearing stiffness and the performance of grinding wheel spindle can be improved.

• Tribology and Lubricants
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• v.33 no.5
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• pp.187-201
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• 2017

This paper presents the impact of couple stress lubricant on performance of slot-entry hydrostatic/hybrid journal symmetric/asymmetric bearings. Reynolds Equation using Finite Element Technique has been solved for the flow of couple stress and Newtonian lubricants in bearings. The results have been computed for concentric design pressure ratio(${\beta}^{\ast}=0.5$), slot width ratio (SWR = 0.25) and chosen parameters of couple stress lubricant ${\bar{l}}=5$, 10, 15. It is observed that numerically simulated outcomes for slot-entry journal bearings, considering the influence of couple stress lubricant indicate a substantial improvement in the performance of the bearing.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.289-296
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• 2018

The offshore subsea platforms are connected to subsea pipelines to transport gas/oil from wells. The pipe is a multilayered structure of polymer and steel for compensating both flexibility and strength. The pipe also requires reinforcement structures to endure the extreme environmental conditions. A vertebrae structure of bend restrictors is one of the reinforcement structures installed to protect the subsea pipe from excessive bending deformations. In this study, structural behaviors of the subsea pipeline with bend restrictors are investigated by the multi-body contact analysis in Abaqus 6.14-2. Contact forces of each bend restrictor extracted from the multi-body contact analysis can be boundary conditions for topology design optimization in Altair Hyperworks 13.0 Hypermesh-Optistruct. Multiple design constraints are considered to obtain a manufacturable design with efficient material usage. Through the multi-body contact analysis with optimized bend restrictors, it is confirmed that the bending performance of the optimized design is enhanced.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.320-327
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• 2017

The main function of an infuser is to ensure constant dosage of a drug. Elastomer drug infusers have been used widely owing to their economic advantages. The mechanism of the device is primarily based on the pressure created from the elastic material that contains the drugs. However, as the drug is infused and the internal pressure is reduced, the drug is not linearly infused at all times. This study involves investigating factors to improve the design of the infuser. The first factor is the range of proper deformation, which does not affect a significant amount of stress variation during infusion. The second is concerned with the flow restrictor and the associated design variables are recommended by employing finite element analysis and the factorial experiment technique. The last factor is related to the spring device connected to balloon. The results showed that the drug reservoir can compensate for unexpected pressure gradient drops.

• Tribology and Lubricants
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• v.7 no.2
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• pp.51-60
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• 1991

For the accurate run-out of a light rotor shaft the sliding bearings supplied with externally pressurized air are effectively applied, and it is important to predict the static and dynamic characteristics of rotor-bearing system. In this study direct numerical method is applied to solve the perturbed Reynolds' equation. To solve it the perturbed dimensionless mass flow rate is used as the boundary condition under the inherently-compensated restrictor. The dynamic characteristics of a rotor supported in the externally pressurized air bearings are analyzed, and as a result the orbit of the journal center is calculated. The theoretical results are investigated and discussed.