• Proceedings of the KSME Conference
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• 2000.04a
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• pp.326-332
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• 2000

It should be essentially considered as important points that design of case in electronic product which simultaneously satisfied with structural stability and molding form in respect to developmental period and economical aspect. Especially, a shape of air vents grille, which is made to emit heat happen to be in the internal of product, must satisfy durability and strength but We have no quantitative data because to be done by experience of designer. So, in this study, We will propose that structure of optimal and method of design in air vents grille, which to reduce a lot of loss of time and cost due to trial and error of design and to stabilize in the BALLISTIC Impact test as to estimate strength with external appearance of product, using linear analysis.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.597-602
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• 2008

Most of structural analyses are concerned with the deformation and stress in a body subjected to external loads. In many fields, however, the interpretation of inverse problems is needed to determine surface tractions or internal stresses. In this study, the inverse processes by using the finite elements and the boundary elements are formulated for the evaluation of internal residual stresses from displacements measured on a remote surface. Small errors in the measured displacements often result in a substantial loss of accuracy of an inverse system. We use the Tikhonov regularization techniques to regularize the ill-conditioned system. Advantages and disadvantages are discussed through numerical examples.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.183-193
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• 2012

Compressive property of high strength concrete with amorphous metal fibers subject to high temperature has been investigated. The measure of this investigation includes explosive spalling, weight loss, residual compressive strength, strain at peak stress, elastic modulus, and residual energy absorption capacity after exposure to $400^{\circ}C$, $600^{\circ}C$and $800^{\circ}C$. In addition to the amorphous metal fiber, two other types of fibers (polypropylene fiber and hooked-end steel fiber) were also included in this investigation for comparison. The experimental program was conducted with high strength concrete using several combinations of the fiber types. The testing result shows that the concrete with amorphous metal fibers plus polypropylene fibers shows a superior behavior than those using other combination or single fiber type ingredient.

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.185-191
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• 2009

Polystyrene/multi-walled carbon nanotube (PS/MWCNT) composites were prepared by the use of latex technology. The monodisperse PS latex was synthesized by an emulsifier-free emulsion polymerization from styrene/potassium persulfate/water system in the presence of ethanol. The MWCNTs were first treated with acid mixture to eliminate impurities, dispersed in deionized water driven by ultrasonicator, and then mixed with the PS latex. From these mixtures, PS/MWCNT composites were prepared by freeze-drying and subsequent compression molding. In the small-amplitude oscillatory shear experiments, both complex viscosity and storage modulus increased with increasing MWCNT content. A pronounced effect of MWCNT content was observed, resulting in larger storage modulus and stronger yield behavior at low frequencies when compared to unmodified PS. It showed a transition from viscous to elastic behavior with increasing MWCNT content. Over the MWCNT content of 3 wt%, the storage modulus was higher than the loss modulus across all frequencies.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.242-247
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• 2007

Energy savings and environmental protection policies have been the general trend in the engine design. The friction power loss associated with the cam mechanism has become important. But it is difficult to measure the torque of rotating valvetrain in real engine environment because most of conventional torque meters are axial type. The objective of this paper is to develop new equipment which can be installed in a rotating camshaft. It uses strain gages to measure the elastic deformation of torque sensor which replaces the cam sprocket. It includes telemetry to transmit torque data via Bluetooth and induction power system to provide adequate power to rotating torque meter. The developed torque meter has good linearity and thermostability. It was installed in a real engine, and successfully measured the valvetrain torque.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.127-131
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• 2003

Foil gas bearing is a noncontact bearing operated by coupled interaction between hydrodynamic pressure of viscous fluid and elastic deformation of foil structure. It has valuable advantages, such as low power loss, long life, oilless environment and low vibration, over conventional bearings for the high speed applications. A high speed BLDC motor adopting the foil bearing has been developed. It is designed to have 38㎾ power at 100,000 RPM for a cryogenic cooler whose operating fluid is neon. In this paper, structural development details especially for the foil gas bearing and rotordynamics are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.994-995
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• 2014

Supporting stiffness of seats is an important component affecting dynamic characteristics cognized by a passenger. To analyze dynamic characteristic of a seat for vehicles operating on various road conditions, the seat vibration from road irregularity should be understood and compared. In this study, the seat is analyzed as distributed supporting system. The dynamic stiffness is measured using masses. The characteristic of the seats is analyzed by measuring distributed dynamic stiffness. The distributed dynamic stiffness of the seat is estimated on various locations and the effects of each component such as spatial distribution, compression level and vibration amplitude are analyzed. The influence of seat cover, elastic support and flexible polyurethane foam on the measured stiffness was analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.191-195
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• 2003

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

• Journal of the Korea Society for Simulation
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• v.9 no.3
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• pp.1-11
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• 2000

This paper proposes the practical echo-signal synthesis models - UTAHID (Underwater TArget by Highlight Distribution) & M-UTAHID(Modified UTAHID) - of underwater target for active sonar engineering At high frequencies all the echo components that are the specular reflected waves and various elastic scattering wave scan be regarded the summation of individual echo from some equivalent scattering centers, so the underwater target is characterized by highlights distributed in spatial target structure. Proposed models are compared with characteristics of random distributed model & equivalent interval highlight model, and analyzed target strength, echo-elongation effect, target time spread loss and so on. Thus these can be efficiently used in various real systems related to underwater target echo-signal synthesis on active sonar and acoustic countermeasure.

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.369-374
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• 2001

It was estimated that the anti-vibration measures at the source location of railroad are the most active and effective ones. Among CWR(Continuously Welded Rail), elastic rail fastener, floating slab, ballast mat, under sleeper pad, etc. like these various kinds of measures in the source, under sleeper pad as an anti-vibration measure was constructed at the railroad track supporting structures in the Jeon-la Line. In this study, through the field measurement of vibration at the railroad track supporting structures and nearby the ground, the vibration reduction effect of under sleeper pad were evaluated by insertion loss. As a result, vibration reduction effects were 5.0∼12.5㏈ on the concrete slab of the bridge, 3.9∼7.5㏈ on the ground nearby the bridge respectively.