• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.617-621
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• 1998

Optical sensing techniques have been associated with high sensitivity and precise measurements and attracted considerable attention in recent years. In this paper, two channels TDM(Time Division Multiplexing) fiber-optic hydrophone array for the underwater applications was fabricated and their acoustic characteristics were investigated by using the acoustic water tank. A fiber length of the order of 100m is wounded at the hollow cylinder type aluminum mandrel. An unbalanced interferometer (discrete Mach-Zehnder type) was used. Sound detection performance is tested in the underwater tank with 2kHz continuous sound source. Finally, it is shown that two channels TDM(Time Division Multiplexing) fiber-optic hydrophone array can detect 2kHz sound stably.

• Korean Journal of Animal Reproduction
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• v.11 no.3
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• pp.206-217
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• 1987

Testes from the drake and the gander have been examined by the electron microscopy in thin sections in order to examine the spermiogenesis and the structure of spermatozoa. The spermiogenesis can be divided into three stages: early spermatid, nuclear elongation, and matured spermatid. In the early spermatid of the drake, there are thread-like material in the nucleus, a prominent nuclear envelope around the nucleus, and big lumens in the cytoplasm. The shape of the gander's mitochondria in the early spermatid is slender compared to that of the drake, and the inner membrane of the mitochondria is thicker than the outer membrane. The distal centriole of the drake and the gander in the early spermatid is a long hollow cylinder form. In the nuclear elongation stage, elongated nucleus forms two or three cross sections in one spermatid cell and it is surrounded by the amorphous sheath. The nucleus of the matured spermatid is compact and its apical end is covered with acrosome cap and acrosome spine. The axoneme is surrounded by the amorphous material.

• Transactions of Materials Processing
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• v.12 no.3
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• pp.214-220
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• 2003

In the case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. There have been few studies about condenser tube extruded by porthole die. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to variation of chamber length in porthole die. The welding chamber height in condenser tube was calculated by using finite element method. Forming analysis results for condenser tube would provide useful information for the optimal design of porthole die.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.772-775
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• 2003

A bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is a hollow cylinder, which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the force applied to the shaft and the relative deformation of a bushing is nonlinear and exhibits features of viscoelasticity. A force-displacement relation for bushings is important for multibody dynamics numerical simulations. For the nonlinear viscoelastic axial response, Pipkin-Rogers model, the direct relation of force and displacement, has been derived from Lianis model and the sinusoidal input was used for Pipkin-Rogers model, and the affection of displacement with frequency change was studied with Pipkin-Rogers model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.33-41
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• 2002

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to variation of chamber length. in porthole die. Estimation was carried out using finite element method. Porthole die is analyzed in as non-steady state. Analytical results provide useful information the optimal design of porthole die.

• Composites Research
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• v.16 no.1
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• pp.34-41
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• 2003

A cure process control model was proposed to optimize the curing process of thick filament wound structure. There are two types of smart cure, one is that the boundary conditions of the hollow cylinder are same between inner surface and outer surface, and the other is that inner surface temperature is slightly higher than outer surface to initiate cure reaction from the inner side to the outer side to reduce residual stress.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.474-478
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• 2004

A bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is a hollow cylinder, which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the force applied to the shaft and the relative deformation of a bushing is nonlinear and exhibits features of viscoelasticity. A force-displacement relation for bushings is important for multibody dynamics numerical simulations. For the nonlinear viscoelastic axial response, Pipkin-Rogers model, the direct relation of force and displacement, has been derived from Lianis model and the sinusoidal input was used for Pipkin-Rogers model, and the affection of displacement with frequency change was studied with Pipkin-Rogers model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.641-647
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• 2008

In this paper, we have studied the basic discharge characteristics of ac-type cylindrical microcavity structure. The structure has a two electrodes, which are positioned in the bottom of the cavity and in the side wall of the cylinder, respectively. The discharge showed asymmetric phenomena depending on the position of a cathode electrode. When the bottom electrode was a cathode, the discharge was stronger even though the area of the cathode was smaller than that of the anode. Simulation results revealed that the focused electric field toward the bottom electrode increased ion density in the space which in turn strengthened the cathode sheath and ionization process.

• Journal of Ocean Engineering and Technology
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• v.35 no.3
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• pp.216-228
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• 2021

In the present study, the performance of a floating oscillating water column (OWC) device has been studied in regular waves. The OWC model has the shape of a hollow cylinder. The linear potential theory is assumed, and a matched eigenfunction expansion method(MEEM) is applied for solving the diffraction and radiation problems. The radiation problem involves the radiation of waves by the heaving motion of a floating OWC device and the oscillating pressure in the air chamber. The characteristics of the exciting forces, hydrodynamic forces, flow rate, air pressure in the chamber, and heave motion response are investigated with various system parameters, such as the inner radius, draft of an OWC, and turbine constant. The efficiency of a floating OWC device is estimated in connection with the extracted wave power and capture width. Specifically, the piston-mode resonance in an internal fluid region plays an important role in the performance of a floating OWC device, along with the heave motion resonance. The developed prediction tool will help determine the various design parameters affecting the performance of a floating OWC device in waves.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.9 no.3
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• pp.161-169
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• 1980

In order to enhance the thermal energy storage capacity of cement mortar and to improve the effective thermal conductivity of paraffin waxes, cement- sand- paraffin wax mixture was investigated. By means of finite difference method, the transient temperature distribution in a hollow cylinder with phase change using average composite properties was obtained, and compared with experimental results. It was shown that the heat absorbed by mixture with $25\%$ paraffin fraction was as much as $50\%$ more than either a concrete mortar or pure paraffin wax in the case of ${\Delta}T=\;18.25^{\circ}C$.