Browsing by Author "Tsai, SS"

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Angular distribution of electrons elastically backscattered from amorphous overlayer systems
(2001-02-10)
Kwei, CM
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Tsai, SS
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Tung, CJ
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Monte Carlo calculations have been performed of the angular distribution of electrons elastically backscattered from amorphous overlayer systems composed of thin copper films and semi-infinite silicon substrates. These calculations showed that the angular distribution of the elastically reflected intensity was dependent on film thickness and electron energy. They also showed that elastically backscattered electrons were due substantially to one, two and three scatterings with single-scattering events contributing about half of the intensity. Based on these findings, we have derived a formula for the contribution from single-scattering events to the angular distribution of the elastically reflected intensity. Combining this formula and the Pi-approximation for multiple scattering, we were able to construct an analytic formula for the angular distribution of electrons elastically backscattered from overlayer systems. Results from this approach were in good agreement with those computed using Monte Carlo simulations. (C) 2001 Elsevier Science B.V, All rights reserved.
Motion information scalability for MC-EZBC
(2004-08-01)
Tsai, SS
;
Hang, HM
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Interframe wavelet video coding algorithm has received much attention lately because of its high coding efficiency and flexible temporal and spatial scalability. It combines the motion-compensated temporal filtering technique together with the wavelet embedded zeroblock coding technique. Blending these two techniques in a nice manner enables it achieving three types of scalability: SNR, temporal and spatial, in one single bit-stream. However, the performance of the interframe wavelet video coding at low bit-rates is less satisfactory because the bit-rate of the non-scalable motion information is too high. In this paper, we extend the framework of Motion Compensated Embedded Zero Block Coding (MC-EZBC) proposed by RPI (Improved MC-EZBC with Quarter-pixel Motion Vectors, ISO/IEC/JTCI SC29/WG11 doc. No. m8366, Fairfax, May 2002). Our major contribution is splitting the motion information in MC-EZBC into a few layers. At very low bit-rates only the "coarse" motion vectors are transmitted. Therefore, we are able to produce compressed bit streams at a lower bit-rate and the associated picture quality is significantly better than that of the original scheme. The overhead due to motion information partitioning is negligible at higher rates. Hence, the rate-distortion performance at high rates is about the same as that of the original scheme. In addition, a Hilbert curve scan order is proposed to increase the efficiency up to 5% in encoding the differential motion vectors. (C) 2004 Elsevier B.V. All rights reserved.