• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.2
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• pp.158-165
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• 2018

Recently there is a great interest in the bi-static sonar. However, since the transmitter and the receiver operate on different platforms, it may be necessary to operate the system in a non-cooperative mode. In this situation, the detection and localization performance are limited. Therefore, it is necessary to classify the received pulse from the transmitter to overcome the performance limitation. In this paper, we proposed a robust automatic pulse classification method that can be applied to real systems. The proposed method eliminates the effects of noise and multipath propagation through post-processing and improves the pulse classification performance. We also verified the proposed method through the sea experimental data.

• Tribology and Lubricants
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• v.34 no.3
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• pp.107-114
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• 2018

This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.