• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.937-944
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• 2013

This paper describes an improved model that can be used for configuring a non-contact pneumatic head to handle a large sheet of glass. The cylindrical head model is of a large size (70 mm). It operates on vortex flow, which can simultaneously generate suction and repulsion over the flat object's surface. The head allows for the minimal non-contact lifting of objects weighing over 3N by using reference conditions (working pressure and head dimensions). Additionally, a functional flow-guide is applied for inducing a developing tangential vortex flow to increase suction and repulsion to the reference head. The cylindrical flow-guide is associated with relatively low tangential velocity. The improved model generates greater lifting force than the reference model, as verified experimentally.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.11
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• pp.1279-1287
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• 2011

Weather strip is a functional component of a car body and doors for leaking protection, isolating outside noise and vibration reduction. Insert metal inserted to the weather strip plays a key role to keep the shape of the weather strip and increase its strength. Insert metal is mainly produced by a press process, which has low productivity and 40% material loss due to the scraps. To solve the problems, a high-speed rolling process for manufacturing the insert metal of weather strip is being attempted. In this study, the insert metal is manufactured by a high-speed rolling process, and its process variables: reduction, relative velocity of rollers and the number of passes, are optimized by using the FEA and the actual tests. The prototype was manufactured by the optimal process.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.166.1-166.1
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• 2011

The rotor design is fundamental to the performance and dynamic response of the Counter-rotating marine tidal current turbine. The wind industry has seen significant advancement single rotor blade technology, offering considerable knowledge and making it easy to transfer to tidal stream energy converters. In this paper, 3D flow and performance an alysis on a 100 kW counter-rotating marine current turbine blade was carried out by using the 3-D Navier-Stokes commercial solver(ANSYS CFX-11.0) to provide more efficient design techniques to design engineers. The front and rear rotor diameter is 8m and the rotating speed is 24.72rpm. Hexahedral meshing was generated by ICEM-CFD to achieve better quality of results. The rated power and its approaching stream velocity for design are 100 kW and 2 m/s respectively. The pressure distribution on the blade's suction side tells us that the pressure becomes low at the leading edge of the airfoil as it moves from the hub to the tip.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.507-510
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• 2007

Piston cores retrieved from the western Ulleung Basin, East Sea were analyzed to examine the potential for hydrocarbon generation and to determine the hydrocarbon indicators. 2D multi-channel reflection seismic and Chirp data were also investigated for mapping and characterizing the geophysical hydrocarbon indicators such as BSR (bottom simulating reflector), blank zone, pock-mark etc. High organic carbon contents and sedimentation rates that suggest good condition for hydrocarbon generation. High pressure and low temperature condition, and high residual hydrocarbon concentrations are favor the formation of natural gas hydrate. In the piston cores, cracks generally oriented to bedding may indicate the gas expansion. The seismic data show several BSRs that are associated with natural gas hydrates and underlying free gas. A number of vertical to sub-vertical blank zones were well identified in the seismic sections. They often show the seismic pull-up structures, probably indicating the presence of high velocity hydrates. Numerous pockmarks were also observed in the Chirp profiles. They may indicate the presence of free gas below the hydrate stability zone as well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1010-1014
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• 2002

A new type actuator has been designed and investigated to overcome thermal problems in slim optical disc drive which is adopted in mobile storage devices. Recently, in optical storage device technical trends, the size of optical disc drives is slimmer to adopt notebook computer and the spindle rotate velocity is faster to achieve high transfer rate and the power of actuator is higher to perform tilting, etc. However, these trends of optical disc drives tend to raise the environment temperature of drives, actuator power and parts temperature. Moreover, it is more difficult to remove the heat inside a drive and the temperature of an actuator increases and drive slims. As a result, increase of surface temperature of actuator body caused that second resonance of an actuator moves down to a lower frequency band and the performance of optical parts also deteriorates. Especially objective lens, coil and magnet of the actuator parts are easily damaged. To manage these thermal problems, in this paper an actuator with a hybrid blade, which is composed of vectra which has low thermal conductivity and magnesium which has high thermal conductivity, has been suggested and verified. Despite the high temperature environment, the proposed actuator showed good dynamic performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1252-1261
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• 2006

This paper summarizes theoretical work on the multichannel decentralized feedback control of sound radiation from aircraft trim panels using piezoceramic actuators. The aircraft trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. It is motivated by the localization of reduction in vibration of single channel active trim panels. 12-channel decentralized feedback control systems are investigated in terms of the reduction of noise and vibration for three configurations of sensor actuator pairs. Local coupling of the closely-spaced sensor and actuator pairs was modeled using single degree of freedom systems. The multichannel control system is characterized using the state-space model. For the stability point of view, the relative stability or robustness is evaluated by comparing the real part of eigenvalues of the system matrix for the three configurations. The control performance is also evaluated and compared for the three configurations. It is found that the multichannel system can lead to the globalization of the reduction in vibration and radiated noise. It does not appear to yield a significant improvement in the vibration because of decreased gain margin. However, the reduction in the radiated noise is remarkably improved due to the variation of the vibration pattern with the actuation configurations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.181-184
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• 2007

This paper deals with the method of vibration measurement of a gun barrel structure using mechanical filter. When a bullet with high speed is moving within a gun barrel type structure with low bending vibration frequencies, it is difficult to measure the bending vibration signals of the structure. For example, noncontact type sensors such as displacement or velocity sensor are not appropriate for the measurement of vibrational signals because of the movement effect of the equipment frame through the moving structures or effect of the ground vibration. One of contact type sensors such as accelerometer is profitable for measurement of vibrational signals because of its wide measurement ranges. In the case of a gun barrel structure including high vibrational signals like shock waves, however, it is necessary to propose vibration measurement method filtering high frequencies. The purpose of the paper is to propose the proper vibrational measurement technique filtering high frequencies of a gun barrel type structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.628-632
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• 2007

The purpose of study is to confirm a acceptable range of data errors in data collecting. To examine a acceptable range of data errors, emission level is calculated for a vehicle flow and heavy vehicle percentage as a function of small-sized velocity. According to road selected, noise level of detail influence road noise calculations. It can be concluded that a vehicle flow raised an error less than 5000(veh/h) for a maximum error in emission level of 3.01dB, and the more a heavy vehicle percentage have a low value, the more emission level is a slight difference. This analysis gives insight regarding the accuracy of traffic flow data that is needed to reach a certain level of accuracy for the resulting noise level.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.467-473
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• 2007

Flow visualization study to qualitatively define the flow field over a stealth UCAV(Uninhabited Combat Air Vehicle) configuration in a water tunnel has been conducted to clarify the basic aerodynamic performance. The test was performed at freestream velocity of 12.7 cm/sec which was corresponding to a Reynolds number of $1.4{\times}10^4$ based on mean aerodynamic chord. The development and breakdown of vortices illuminated by using dye were compared to the previous force and moment data. It was shown that the effect of the vortices generated by the main-body and junction are dominant in the low angle-of-attack region. However, in the high angle-of-attack region, the vortex generated by the fore-body mainly influenced the aerodynamic performance of the model.

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.7
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• pp.980-986
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• 1999

This study was done to ivestigate the fabrics thatminimized harmfulness of UVB(ultraviolet B) and that might product Vit. {{{{ {D }`_{3 } ^{ } }} by UVB. Twelve female subjects wearing in three different types i.e fabric A(UVB 100% protection) fabric B(UVB 50% protection) and bikinii were exposed to outdoor environment (Air Temp : 25℃, 42% R,H Air velocity : 0.13m/s UV does :6KJ/m2) Blood samples were taken 24 hours before the after the experiment in order to examine concentration of vit.{{{{ {D }`_{3 } ^{ } }} in the blood. During the experiment axillary temperature skin temperature of 7 areas(forehead Chest Upper arm, Hand Thigh Lower leg, Foot) were measured. The more irradiated areas by UVB were the more the concentration of serum 25(OH){{{{ {D }`_{3 } ^{ } }} were significantly. Mean skin temperature was significantly low levekl in wearing the fabric of UVB 50% protection (p<0.001) Axillary temperature was significantly high level in wearing the fabric of UVB 50% protection (p<0.001). Therefore the fabric of UVB 50% protection intercepts the radiation and has advantage to give off body heat over other fabrics