Automotive turbochargers are known to have operation into the self-excited unstable vibration region. In the past these instabilities have been accepted as unavoidable, but recent developments in analysis and instrumentation may make it possible to reduce or eliminate them. A test stand has been developed at Virginia Tech to measure the vibrations of a 3.9 liter diesel engine stock turbocharger with both stock floating bushing journal bearings and also custom design fixed geometry bearings. Vibration spectrum content clearly identifies the shaft instabilities and provides the basis for additional evaluation of current and future improved bearing design modifications. The current results, for a series of custom fixed geometry journal bearings, show a shift in the frequencies of the two unstable modes for the no load operating condition. These results can be compared to the linear analysis predicted instability frequencies to better understand the actual response of the high speed turbocharger. This paper documents the spectrum content for three different bearing designs and compares the results to a stock floating bush journal bearing result for the same no load operating condition.
We propose a robust high dynamic range (HDR) video synthesis algorithm using the superpixel-based illuminance-invariant motion estimation technique. The proposed algorithm first selects an input frame in an alternating exposed input video as the reference. Then, the correspondences between two adjacent frames are estimated by employing a feature descriptor, which is robust against illuminance variation, and a superpixel segmentation technique. Next, the input frames are warped to the reference frame using the estimated motion maps. Finally, the final HDR frame is synthesized by constructing a weight map, which can handle complex motions and poor exposures by considering the underlying structures in the input frames. Experimental results on real test sequences show that the proposed algorithm can provide high-quality HDR videos compared with those obtained by state-of-the-art algorithms in terms of both subjective and objective evaluations. INDEX TERMS High dynamic range (HDR) video synthesis, HDR imaging, motion estimation.
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