• Tribology and Lubricants
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• v.39 no.1
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• pp.28-34
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• 2023

Because of their cleanliness, low friction, and high stiffness, aerostatic bearings are used in numerous applications. Aerostic bearings that use porous materials as means of flow restriction have higher stiffness than other types of bearings and have been successfully applied as guide bearings, which have high motion accuracy requirements. However, the performances of porous bearings exhibit strong nonlinearity and can vary considerably depending on design parameters. Therefore, accurate prediction of the performance characteristics of porous bearings is necessary or their successful application. This study presents a porous bearing design and performance analysis for a spindle used in wafer polishing. The Reynolds and Darcy flow equations are solved to calculate the pressures in the lubrication film and porous busing, respectively. To verify the validity of the proposed analytical model, the calculated pressure distribution in the designed bearing is compared with that derived from previous research. Additional parametric studies are performed to determine the optimal design parameters. Analytical results show that optimal design parameters that obtain the maximum stiffness can be derived. In addition, the results show that cross-coupled stiffness increases with rotating speed. Thus, issues related to stability should be investigated at the design stage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2201-2210
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• 2000

Vibration of a rotating disk-spindle system is analyzed by using Hamilton's principle, FEM and substructure synthesis. A rotating disk undergoes the rigid body motion and the elastic deformation. It s equation of motion is derived by Kirchhoff plate theory and von Karman nonlinear strain. A rotating shaft is described by Rayleigh beam theory considering the axial rigid body motion. The stationay shaft supporting the rotating disk-spindle-bearing system is modeled by Euler beam theory, and the stiffness of ball bearing is determined by A.B.Jones' theory. FEM is used to solve the derived governing equations, and substructure synthesis is introduced to assemble each structure of the rotating disk-spindle system. The developed theory is applied to the spindle system of a 35' computer hard disk drive with 3 disks to verify the simulation results. The simulation results agree very well with the experimental ones. The proposed theory may be effectively expanded to the complex structure of a disk-spindle system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2338-2343
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• 2015

An analytical model was developed in this study and then implemented into a tool for automation of FEA (Finite Element Analysis) of a spindle system for natural frequencies and modes in the universal FEA software, ANSYS. VBA of EXCEL was used for the implementation. It allowed graphic user interfaces (GUIs) to be developed for a user to interact with the tool and, in addition, an EXCEL spreadsheet to be used for data arrangement. A code was developed in the language of ANSYS to generate the geometric model of the spindle system, sequentially to construct the analytical model based on the information in the GUIs, and finally to perform computation for the FEA. Its automation of the model generation and analysis can help to identify a near optimal design of the spindle system under design in minimum time and efforts.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.11
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• pp.479-486
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• 2015

Model checking method is able to check all possible cases automatically and is applicable to specifications or design before actual implementation so that some critical systems have adopted this method actively. However, the current practice of software verification is largely dependant on basic methods such as manual testing because of lack of understanding about this rigorous method and high verification cost. In this paper we conducted an experimental research for the automated verification using the SPIN model checker on an online-game server to study the applicability of the technique in this domain. The results show that we could verify major features of the online-game server party system with 5~7 GB memory and within 10 minutes execution time, and also found a hidden system error that passed existing testing process. This result shows the possibility of rigorous and effective verification with reasonable cost in comparison to manual testing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.461-462
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• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1130-1135
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• 2001

This paper investigated the dynamic performance of HDD disk-spindle system to reduce disk fluttering. Rocking frequencies of the disk-spindle system and radial NRRO are measured to escape the ball defect frequencies and to determine the relative optimal position of the disk in the motor. It was found that disk fluttering was reduced by increasing disk thickness, inserting viscoelastic material between the disk and the spacer and decreasing the gap between the disk and the base.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.256-256
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• 2004

Micro/Meso 기계적 가공은 기존 MEMS 공정에서 제작할 수 없었던 높은 세장비(aspect ratio)를 가지는 제품을 가공할 수 있을 뿐만 아니라 보다 높은 가공 정밀도를 획득할 수 있다. 따라서, 미소 부품에 대한 마이크로/매소 단위의 미세 절삭 가공을 위해서는 공간적 측면과 에너지 소비, 정밀도 측면에서 효율적인 시스템을 구성하기 위해서 마이크로 머시닝 전용 기계가 요구된다. 이에 본 연구에서는 '마이크로 팩토리' 의 기본 공작기계인 마이크로 선반을 개발하여 초정밀 미소 절삭에 대한 연구를 진행 중에 있다.(중략)

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.5
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• pp.110-119
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• 2007

In an extended enterprise, there is a shift to shared services, cosourcing and outsourcing, and extending out to partners, suppliers, and customers to accomplish business objectives more effectively. Along with this critical need, executives should be aware of the need to focus on optimizing the value of their information technology and reducing the related risks. So IT governance is critical, and many companies including spin-off venture are providing IT governance solution, but very little is known about brand management and marketing strategy of IT governance solution provider. The purpose of this study is to investigate brand positioning of IT governance solution company focusing on spin-off venture. The results of this study are summarized as follows. First, brand management is needed in the spin-off venture. second, IT governance solution companies including spin-off venture must provide something more than functional value. That is, they actively seek to emotional or symbolic value for their customers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.261-267
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• 2009

The spindle with a built-in motor can be used to simplify the structure of machine tool system, while the rotor has unbalance mass inevitably. Therefore, it is important to recognize the effect of unbalance mass. This paper presents analysis of dynamic behavior of a high speed spindle with a built-in motor. The spindle is supported by the angular contact ball bearings and the rotor is fixed at the middle of spindle. The spindle used in CNC automatic lathe has been investigated using combined methodologies of finite elements and transfer matrices. The Houbolt method is used for the integration of the system equations and the dynamic behavior of spindle is obtained considering unbalance mass of rotor. Results show that increasing rotational speed of spindle magnifies the whirl responses of spindle seriously. Also the whirl responses of spindle are affected by the other factors such as unbalance mass and bearing stiffness.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.84-92
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• 2005

This work presents the feasibility of shunt damping far vibration suppression of the rotating HDD disk-spindle system using piezoelectric bimorph. A target vibration mode which significantly restricts the recording density increment of the drive is determined through modal analysis and a piezoelectric bimorph is designed to suppress unwanted vibration. After deriving the two-dimensional generalized electromechanical coupling coefficient of the shunted drive, the shunt damping of the system is predicted by simulating the displacement transmissibility using the coefficient. In addition, optimal design process using sensitivity analysis is undertaken in order to improve the shunt damping of the system. The effectiveness of the proposed methodology is verified through experimental implementation by observing the vibration characteristics of the rotating disk-spindle system in frequency domain.