• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.649-656
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• 2016

Thick composite disks are utilized in the fast-rotating machines such as turbine disks, flywheels, and so on. The effects of rotating speed on the dynamic characteristics of thick composite disks are deeply studied in this paper. The dynamic governing equations of a rotating composite disk including transverse shear and rotary inertia are derived and then formulated into the finite element equation. Isotropic, circumferentially reinforced disk, and radially reinforced disk are selected for the numerical analysis. The inclusion of the transverse shear and rotary inertia into the governing equation of the rotating disks makes the natural frequency reduced as well as the critical speed. The present results show that the rotation of a thick disk may not reduce the effect of transverse shear and rotary inertia depending on anisotropy, thickness ratio and mode, unlike the results reported in other studies.

• Composites Research
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• v.18 no.4
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• pp.8-13
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• 2005

Rotating circular disks are widely used in data storage devices as well as in traditional industrial machines. Faster rotating speed is required in data storage devices for higher data transfer rate. In this Paper an application of composite materials to CD is proposed to increase critical speeds and the strength analysis was performed. A differential equation of displacement is derived for the analytic stress distribution of rotating polar orthotropic disk. The stress distributions for typical GFRP and CFRP disks and the maximum allowable speeds subjected to a constraint of tensile strength are presented in addition to polycarbonate disk. The results show that the application of CFRP to rotating disk can increase the maximum allowable rotating speed but this may not be applicable to GFRP disk.

• Composites Research
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• v.20 no.3
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• pp.43-49
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• 2007

Dynamic instability of rotating disks is the most significant factor to limit its rotating speed. Application of composite materials to rotating disks may enhance the dynamic stability leading to a possible design of rotating disks with lightweight and high speed. Whereas much work has been done on the effect of transverse shear and rotary inertia, called Timoshenko effect, on the dynamic behavior of plates, there is little work on the correlation between the effect and the rotation of disk, especially nothing in case of composite disks. The dynamic equations of a rotating composite disk are formulated with the Timoshenko effect and the vibrational analysis is performed by using a commercial package MSC/NASTRAN. According to the results, the Timoshenko effect goes seesaw in some modes, unlike the well-known fact that the effect decreases as the rotating speed increases. And it can be concluded, based only on the present results, that decrement of the Timoshenko effect by disk rotation grows larger as the thickness ratio decreases, the diameter ratio increases, the modulus ratio increases, and the mode number increases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1225-1232
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• 2000

In this paper, a new coupled resonator which expands free spectral ranges (FSR) of the W. G. mode resonators is presented. The proposed coupled resonator consists of two dielectric disks. The resonance frequency of the coupled resonator is equivalent to the frequency, which satisfies the individual resonance conditions of each disk at the same time. As the results, the FSR is expanded. The coupled resonator proposed in this paper at K-Band is fabricated by using dielectric disks and the dielectric straight waveguides. The validity of proposed coupled resonator was verified through experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.854-857
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• 2006

The centrifugal terce acting on a rotating disk creates the in-plane loads in radial and circumferential directions. Application of fiber reinforced composite materials to the relating disk can satisfy the demand for the increment of its rotating speed. However, the existing researches have been confined to lamina disks. This paper deals with the vibration analysis of rotating composite laminate disks. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating laminated disks. Galerkin's method is applied to obtain the series solution. The numerical results are given for the CFRP laminate disks with stacking sequence [0/90]s and [90/0]s.

• Journal of the Korean Arthroscopy Society
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• v.11 no.2
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• pp.122-127
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• 2007

Purpose: To know about the clinical characteristics such as causes, types, associated injuries and treatment of the lateral meniscus injuries. Materials and Methods: Retrospective analysis was performed for 129 lateral meniscus tears which were divided into 2 groups, Non-discoid and Discoid. Analysis included age and sex distribution, causes of injury, types and location of tear, associated injuries, and methods of treatment. Results: Both Non-discoid and Discoid were prevalent in man and Discoid group was equally distributed through 2nd to 5th decades and Non-discoid group was more prevalent in 4th to 5th decades. Sports injury was the most common cause in both groups and the Nondiscoid group tended to sustain minor injuries compared to Discoid group. Complex tear and body was most common type and site of tear in both groups. Associated injuries were common in Non-discoid group and isolated injuries were common in Discoid group. Partial meniscectomy was commonly done in Non-discoid group and subtotal meniscectomy in Discoid group based on the types of tear. Conclusion: Non-discoid and Discoid lateral meniscus injuries are similar in types and sites of injuries but different in causes of injury, associated injuries and methods of treatment. Therefore, proper diagnosis and treatment would be necessary according to the characteristics.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.176-179
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• 2005

Rotating annular disks are widely used in data storage devices such as CDs, DVDs(digital versatile disks), and HDs(hard disks) as well as in traditional industrial machines like sawing machines, turbines, brake disks. The exact stress distribution of rotating polar orthotropic disk is derived by solving directly the equilibrium equation instead of using stress function. Stress distributions for typical GFRP and CFRP disks are presented in addition to polycarbonate disk. The results show that the application of CFRP to rotating disk can increase the maximum allowable rotating speed but this may not be applicable to GFRP disk.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.982-989
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• 2006

The centrifugal force acting on a rotating disk creates the in-plane loads in radial and circumferential directions. Application of fiber reinforced composite materials to the rotating disk can satisfy the demand for the increment of its rotating speed. However, the existing researches have been confined to lamina disks. This paper deals with the stress and vibration analysis of rotating laminated composite disks. The maximum strain theory for failure criterion is applied to determine the strength of the laminate disk from which the maximum allowable speed is obtained. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating laminated disks. The Galerkin method is applied to obtain the series solution. The numerical results are given for the cross-ply laminated composite disks.

• Journal of the Korean Arthroscopy Society
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• v.13 no.2
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• pp.165-169
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• 2009

The lateral meniscus is morphologically more variable than the medial meniscus. An abnormal lateral meniscus also varies with respect to its size, shape and stability, and such variations can occur in any patient of any age. The most common variant is a discoid lateral meniscus. We recently encountered a patient with a discoid lateral meniscus for which the anterior horn of the meniscus was anomalously inserted into the anterior ACL. The patient was forty five years old women who had persistent pain for three to four years without any specific trauma history. She was preoperatively diagnosed as having discoid lateral meniscus by MRI, and was confirmed the presence of the complex tear and anomalous insertion of the anterior horn of the discoid lateral meniscus into the anterior ACL by arthroscopic examination. Arthroscopic subtotal meniscectomy was performed and the symptoms were improved after surgery.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.722-723
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• 2013