• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.211-217
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• 1998

A disk rotor dynamic analysis program called by DR. DAP is developed for disk drive spindle systems to analyze dynamic characteristics in operation and to estimate the effects of excitation sources. It is applicable to design for stabilization and to select parts of disk drive spindle systems. The disk drive spindle system in this program is modeled as a flexible shaft with multiple flexible disks, which is supported by bearings and driven by electric motor, and its complicated coupled vibration characteristics are analyzed by using a substructure synthesis technique with the assumed-modes method. All the coupled modes of interest can be well predicted by the example of a three disk hard disk drive with the three tuning parameters. It is also shown that, with the introduction of the excitation sources associated with the defects of ball bearing systems, the magnetic unbalance of spindle motor, the program can well predict the stability of the system, i.e., the possibility of resonance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.239-244
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• 2009

This paper suggests a precision positioning control technique of a precision positioning stage with coupling effects. The precision positioning stage is supported by four flexible spring hinges and driven by two piezoelectric actuators. The dynamic characteristics of the precision positioning stage is modeled and identified by the FEM analysis. The dynamic characteristics of the stage are also identified by the frequency domain modeling technique based on the experimental data. Reliability of two modeling methods is examined by comparing the numerically and experimentally produced responses of the stage. This paper proposes a sliding mode control technique with integrator to improve the tracking ability of the precision positioning stage to the complex input signal using. To demonstrate the effectiveness of the proposed modeling schemes and control algorithm, experiment validations are performed.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.637-640
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• 2006

DuPont Teijin Films (DTF) have developed engineered substrates specifically for the flexible electronics market. $Teonex^{(R)}Q65$ is a biaxially oriented crystalline polyester with a tailored surface and it is emerging as a competitive material for the base substrate in OLED displays and active matrix backplanes. Given the dimensional reproducibility requirements in the display applications, uncontrolled moisture absorption during the processing cycle could potentially be far more significant than the inherent shrinkage of the base substrate. Understanding these effects and optimising the processing steps involved in device manufacture will be critical to achieving the ultimate performance that can be achieved with the base substrate.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.197-203
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• 2008

In the present study, we carry out numerical simulations of energy harvesting eel by using the immersed boundary method. Eel is modeled by a flexible filament and is placed behind a circular cylinder. We perform systematic simulations in order to explore the effects of Reynolds number. The instantaneous eel motion is analyzed under different conditions and surrounding vortical structures are identified. The flapping frequency of eel has been compared with that in case of plate alone as well as filament alone. As increasing Reynolds number, we can see that the flexible filament flaps passively by obtaining the Strouhal number of cylinder alone and filament with cylinder.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.197-203
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• 2008

In the present study, we carry out numerical simulations of energy harvesting eel by using the immersed boundary method. Eel is modeled by a flexible filament and is placed behind a circular cylinder. We perform systematic simulations in order to explore the effects of Reynolds number. The instantaneous eel motion is analyzed under different conditions and surrounding vortical structures are identified. The flapping frequency of eel has been compared with that in case of plate alone as well as filament alone. As increasing Reynolds number, we can see that the flexible filament flaps passively by obtaining the Strouhal number of cylinder alone and filament with cylinder.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.107-117
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• 1991

The dynamic stability problem of nonconservative system is one of the important problems. In this study, flexible missile with mass variation is regarded as a free Timoshenko beam subjected to a controlled follower force. The stability was studied numerically through the finite element method. Through the study, the obtained results are as follows: [1] Without force direction control (1) In the case of no mass reduction, the existence of concentrated mass increases critical follower force. (2) Mass reduction rate of the beam slightly effects on the change of critical follower force. [2] With force direction control (1) Shear deformation parameter S contributes insignificantly to the force at instability when $S{\geq}10^4$. (2) With mass variation, increase of concentrated mass increases critical follower force at instbility. (3) The type of promary instability is determined by the sensor location.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.45-48
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• 2007

This paper proposes a flexible selection method of feature vectors for speaker identification. In speaker identification, overlapped region between speaker models lowers the accuracy. Recently, a method was proposed which discards overlapped feature vectors without regard to the source causing the overlap. We suggest a new method using both overlapped features among speakers and non-overlapped features to mitigate the overlap effects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.579-584
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• 2008

A nano-imprinting stage has been widely used in various fields of nanotechnology. In this study, an analysis method of a nano-imprinting stage machine using FEM and flexible multi-body vibration has been presented. The simulation using CAE for the imprinting machine is to analyze vibration characteristics of 3-axis nano-imprinting stage and 4-axis nano-imprinting stage. Structural components such as the upper plate have been modeled with finite elements to analyze flexibility effects during the precision stage motion. In this paper flexible multi-body dynamic simulation is executed to support robust design of the precision stage mechanism.

• Steel and Composite Structures
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• v.16 no.4
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• pp.389-415
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• 2014

This study deals with dynamic model of composite sandwich panels with functionally graded flexible cores under low velocity impacts of multiple large or small masses using a new improved higher order sandwich panel theory (IHSAPT). In-plane stresses were considered for the functionally graded core and face sheets. The formulation was based on the first order shear deformation theory for the composite face sheets and polynomial description of the displacement fields in the core that was based on the second Frostig's model. Fully dynamic effects of the functionally graded core and face-sheets were considered in this study. Impacts were assumed to occur simultaneously and normally over the top and/or bottom of the face-sheets with arbitrary different masses and initial velocities. The contact forces between the panel and impactors were treated as internal forces of the system. Nonlinear contact stiffness was linearized with a newly presented improved analytical method in this paper. The results were validated by comparing the analytical, numerical and experimental results published in the latest literature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.472-478
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• 2000

The vibration of the hard disk drive (HDD) systems, which comprises flexible disks, flexible shafts, bearings, and base structures, are analyzed by a finite element method (FEM) to cope with complicated coupling effects between them. The natural frequencies and mode shapes of the uncoupled, axial and bending coupled vibrations are calculated. Modal testing of the HDD systems is performed to validate the finite element analysis (FEA) results. Good agreement was obtained between the computed and experimental results. Sizing design sensitivity analysis (DSA) of the system was performed with the thickness of base structure and bearing stiffness as design variables. The DSA results tell how can I increase or decrease eigenvalue of the system effectively.