• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.661-667
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• 2002

With the increase of storage density, high rotational speed and high access technologies in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Up to now the researches of rubber mount for anti-vibration focused on how to calculate the static and the dynamic stiffness of rubber mount and loaned out consideration of the dimensional tolerance of rubber mount for anti-vibration. This paper presents the effects of dimensional tolerance of rubber mount for anti-nitration on the dynamic characteristics of optical disk drive by finite element analysis and dynamic test. The relation between dimensional tolerance and dynamic characteristics of optical disk drive is observed and discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.829-832
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• 2002

With the increase of storage density, high rotational speed and high access technologies in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Up to now the researches of rubber mount for anti-vibration focused on how to calculate the static and the dynamic stiffness of rubber mount and leaved out of consideration of the dimensional tolerance of rubber mount for anti-vibration. This paper presents the effects of dimensional tolerance of rubber mount for anti-vibration on the dynamic characteristics of optical disk drive by finite element analysis and dynamic test. The relation between dimensional tolerance and dynamic characteristics of optical disk drive is observed and discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.12
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• pp.1147-1152
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• 2007

This paper deals with a scheme for fault-tolerance improvement of real-time embedded systems, which engages an equidistant checkpointing technique to tolerate transient errors. Transient errors are caused by transient faults which are the most significant type of fault in reliable computer systems. Transient faults are assumed to occur according to a Poisson process and to be detected in a non-concurrent manner (e.g., checked periodically). The probability of the successful real-time task completion in the presence of transient errors is derived with the consideration of the possible effects of the transient errors. Based on this, a condition under which inserting checkpoints improves the fault-tolerance of the system is introduced and an optimal equidistant checkpointing strategy that achieves the highest fault tolerance is presented.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.44-50
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• 2010

Structural vibration is a significant problem in many multi-part or multi-component assemblies. In aircraft industry, structures are composed of various fasteners, such as bolts, snap, hinge, weld or other fastener or connector (collectively "fasteners"). Due to these, prediction and design involving dynamic characteristics is quite complicated. However, the current state of the art does not provide an analytical tool to effectively predict structure's dynamic characteristics, because consideration of structural uncertainties (i.e. material properties, geometric tolerance, dimensional tolerance, environment and so on) is difficult and very small fasteners in the structure cause a huge amount of analysis time to predict dynamic characteristics using the FEM (finite element method). In this study, to resolve the current state of the art, a new approach is proposed using the FEM and probabilistic analysis. Firstly, equivalent elements are developed using simple element (e.g. bar, beam, mass) to replace fasteners' finite element model. Developed equivalent elements enable to explain static behavior and dynamic behavior of the structure. Secondly, probabilistic analysis is applied to evaluate the PDF (probability density function) of dynamic characteristics due to tolerance, material properties and so on. MCS (Monte-Carlo simulation) is employed for this. Proposed methodology offers efficiency of dynamic analysis and reality of the field as well. Simple plates joined by fasteners are taken as an example to illustrate the proposed method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.5
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• pp.609-615
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• 2010

Angular contact ball bearings in a high speed spindles are under the extreme conditions, such as high temperature, big centrifugal force and thrust cutting forces. So, the assembly contacts between spindle shaft and inner ring bearings, bearing housing and outer ring of bearings are occasionally unstable at high speed revolution. Furthermore, the ball contact angle of a bearing, which influence stiffness and lifetime of bearings, are changed according to loads and rotational speed. To analyze internal forces of a bearing under high speed revolution, the ball contact are calculated using nonlinear equations in consideration of rotational speed, thrust loads and raceway form. Diameter increase of inner and outer ring by influence factors, such as internal forces to inner and outer ring, centrifugal force and temperature of inner and outer rings are calculated to establish stable state in bearing assembly in high speed spindle. Finally, contribution ratio of influence factor to assembly design tolerance of inner and outer rings are shown and the stable assembly design tolerance are proposed.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.29-33
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• 2013

The understanding of the strain dependence of critical current, $I_c$, in the reversible region is important for the evaluation of the performance of coated conductor (CC) tapes in practical applications. In this study, the stress/strain tolerance of $I_c$ in GdBCO CC tapes with stainless steel substrate stabilized by additional Cu and brass laminate was analyzed quantitatively through $I_c$-strain measurement at 77 K under self-field. The variation in irreversible strain limits of CC tapes by the addition of stabilizing layers was analyzed through the consideration of the pre-strain induced on the GdBCO coating film. The results were then compared with the ones previously reported for GdBCO CC tapes with Hastelloy substrate. As a result, GdBCO CC tapes with stainless steel substrate showed much higher strain tolerance of $I_c$ as compared with those adopting Hastelloy substrate.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.82-91
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• 1995

The purpose of this research is to develop a new real-time process control system. In this paper, a theoretical method for acquiring the control limit of cutting process(cutting surface) according to the required value(geometric tolerance) based on geometrical relations was propsed. In particular, the three following points are amphasized. Firstly, the process control was based on the cutting process, and the control limit was determined from the analysis of geometrical relations. Secondly, AMGD(Actual Measured Geometrical Deviation) was used as a new substitute value in process analysis. Thirdly, fuzzy reasoning was introduced to get the control limit flexibility according to the variations in the required value and general consideration of each measurememnt items.

• The Bulletin of The Korean Astronomical Society
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• v.24 no.2
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• pp.120-120
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• 1999

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.163-166
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• 2002

For the development of an all composite unmanned aerial vehicle (UAV), manufacturing consideration in design phase, works for composite parts fabrication, subassembly and final assembly are summarized. In design phase, to maximize the advantage of composite material, manufacturing processes such as cocuring, cobonding and secondary bonding are introduced. For the curing of designed parts, composite tools are designed and manufactured. Assembly jigs are designed to satisfy dimensional tolerance of the structure. Inspection criteria are established and applied to the manufacturing. Technical data about inspection items and methods are summarized as manufacturing specifications for the mass production of the UAV structure.