• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.33-42
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• 2009

A polymer-based flexible neural probe was fabricated for monitoring of neural activities from a brain. To improve the insertion stiffness, a 5 ${\mu}m$ thick biocompatible Au layer was electroplated between the top and bottom polymer layers. The developed neural probe penetrated a gel whose elastic modulus is similar to that of a live brain tissue without any fracture, To minimize mechanical residual stress and bending from the probe, two new methods were employed: (1) use of a thermal annealing process after completing the device and (2) incorporation of multiple different layers to compensate the residual stress between top and bottom layers. Mechanical bending around the probe tip was clearly removed after employing the two processes. In electrical test, the developed probe showed a proper impedance value to record neural signals from a brain and the result remained the same for 72 hours. In simple in-vitro probe characterization, the probe showed a great removal of residual stress and an excellent recording performance. The in-vitro recording results did not change even after 1 week, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.250-263
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• 2001

The up and down speed of heddle frames that produce woven cloth by insertion of weft yarns between warp yarns has been increased recently much for productivity improvement, which induces higher inertial stresses and vibrations in the heddle frame. the heddle frame is required to reduce its mass because the heddle frame contributes the major portion of the stresses in the heddle frames during accelerating and decelerating. Conventional aluminum heddle frames have fatigue life of around 5 months at 550rpm due to their low fatigue flexural strength as well as low bending stiffness. In this work, since carbon/epoxy composite materials have high specific fatigue strength(S/p), high specific modulus(E/p), high damping capacity and sandwich construction results in lower deflections and higher buckling resistance, the sandwich structure composed of carbon/epoxy composite skins and polyurethane foam were employed for the high-speed heddle frame. The design map for the sandwich beams was accomplished to determine the optimum thickness and the stacking sequences for the heddle frames. Also the effects of the number of ribs on the stress of the heddle frame were investigated by FEM analyses. Finally, the high-speed heddle frames were manufactured with sandwich structures and the static and dynamic properties of the aluminum and the composite heddle frames were tested and compared with each other.

• Tribology and Lubricants
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• v.38 no.5
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• pp.205-212
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• 2022

This paper presents experimental measurements of the structural characteristics of a two-pad beam-type gas foil journal bearing and its rotordynamic performance for a high-speed motor-driven turbocompressor. The test bearing had two top foils and two beam foils, each with an arc length of ~180°. Each beam foil was etched to obtain 40 beams with six geometries of different lengths and widths. The insertion of beam foils into the bearing housing produces equivalent beam heights. The structural tests of the bearing with a non-rotating journal revealed a smaller bearing clearance and larger structural stiffness for the load-on-pad configuration than for the load-between-pads configuration. Rotordynamic performance measurements during driving tests up to 100 krpm demonstrated synchronous vibrations and subsynchronous vibrations with large amplitudes. The test was repeated after inserting the shim between the top foil and beam foil to reduce the bearing radial clearance. The reduced bearing clearance resulted in a reduction in the peak amplitude of the synchronous vibrations and an increase in the speed at which the peak amplitude occurred. In addition, the onset speed and amplitude of the subsynchronous vibrations were dramatically increased and diminished, respectively. The rotor coast-down tests at 100 krpm show that the reduction in the bearing clearance extends the time to rotor stop, thus implying an improvement in hydrodynamic pressure generation and a reduction in bearing frictional torque.