Synthetic and mechanistic studies of silylenium ions in solution

Abstraction of hydride from silyl hydrides by triphenylmethyl salts in methylene chloride apparently results in the formation of transient silylenium ions. Dimethylsilyl triphenylmethyl ether, dimethylsilyl t-butyl ether, benzyl dimethylsilyl ether, dimethylsilyl p-methoxybenzyl ether and dimethylsilyl diphenylmethyl ether, compounds with good carbocation leaving groups, afford cyclosiloxane oligomers in high yields under mild conditions suggesting the involvement of transient silylenium ions via abstraction of hydrides by triphenylmethyl salts. In the case of dimethylsilyl triphenylmethyl ether, triphenylmethyl cation can be regenerated in the reaction, so that triphenylmethyl salts can then be used as catalysts. From dimethylsilanone trapping experiments, it appears that these silylenium ions either decompose to free silanone or undergo an intermolecular silanone-transfer reaction. These results are the first to demonstrate the synthetic use of silylenium ions in solution;Olefins which contain both an ether group and a dimethylsilyl group on the same side of the double bond can cyclize into unsaturated five- and six-membered ring cyclic silyl ethers upon treatment with triphenylmethyl salts. Saturated compounds with an ether group and dimethylsilyl group can cyclize into saturated five- and six-membered ring cyclic silyl ethers. Mechanisms involving oxonium ion intermediates are proposed to account for the products;Attempts to generalize the same fragmentation process of silylenium ions to form silenes and disilenes failed. An attempt to use triphenylsilyl as the leaving group also failed to yield the desired cyclosiloxane oligomers using the same silylenium ion fragmentation scheme

Architectural Scene Reconstruction from Single or Multiple Uncalibrated Images

In this paper we present a system for the reconstruction of 3D models of architectural scenes from single or multiple uncalibrated images. The partial 3D model of a building is recovered from a single image using geometric constraints such as parallelism and orthogonality, which are likely to be found in most architectural scenes. The approximate corner positions of a building are selected interactively by a user and then further refined automatically using Hough transform. The relative depths of the corner points are calculated according to the perspective projection model. Partial 3D models recovered from different viewpoints are registered to a common coordinate system for integration. The 3D model registration process is carried out using modified ICP (iterative closest point) algorithm with the initial parameters provided by geometric constraints of the building. The integrated 3D model is then fitted with piecewise planar surfaces to generate a more geometrically consistent model. The acquired images are finally mapped onto the surface of the reconstructed 3D model to create a photo-realistic model. A working system which allows a user to interactively build a 3D model of an architectural scene from single or multiple images has been proposed and implemented

Gender Determination using Fingerprint Features

Several previous studies have investigated the gender difference of the fingerprint features. However, regarding to the statistical significance of such differences, inconsistent results have been obtained. To resolve this problem and to develop a method for gender determination, this work proposes and tests three fingertip features for gender determination. Fingerprints were obtained from 115 normal healthy adults comprised of 57 male and 58 female volunteers. All persons were born in Taiwan and were of Han nationality. The age range was18-35 years. The features of this study are ridge count, ridge density, and finger size, all three of which can easily be determined by counting and calculation. Experimental results show that the tested ridge density features alone are not very effective for gender determination. However, the proposed ridge count and finger size features of left little fingers are useful, achieving a classification accuracy of 75% (P-valu

A 3D ANALYSIS OF THE VOllEYBAll SPIKE

The purpose of this study was to identify and describe the biomechanical characteristics of the high school volleyball players jump spikes. Eleven elite male players participated in this study. Two Peak high-speed cameras (120 Hz) were genlocked to record the spiking action. The results showed that the spiking techniques of male high school volleyball players are quite similar to those of university volleyball players except for contact ball height. It is suggested that coaches should train the young players jumping ability and fast spiking motion in order to improve spiking power

Low-complexity face-assisted video coding

[[abstract]]This paper presents a novel face-assisted video coding scheme to enhance the visual quality of the face regions in video telephony applications. A skin-color based face detection and tracking scheme is proposed to locate the face regions in real-time. After classifying the macroblocks into the face and non-face regions, we present a dynamic distortion weighting adjustment (DDWA) scheme to drop the static non-face macroblocks, and the saved bits are used to compensate the face region by adjusting the distortion weighting of the face macroblocks. The quality of face regions will thus be enhanced. Moreover, the computation originally required for the skipped macroblocks can also be saved. The experimental results show that the proposed method can significantly improve the PSNR and the subjective quality of face regions, while the degradation introduced on the non-face areas is relatively insensitive to human perception. The proposed algorithm is fully compatible with the H.263 standard, and the low complexity feature makes it well suited to implement for real-time applications[[fileno]]2030144030041[[department]]電機工程學

Dynamic region of interest transcoding for multipoint video conferencing

This paper presents a region of interest transcoding scheme for multipoint video conferencing to enhance the visual quality. In a multipoint videoconference, usually there are only one or two active conferees at one time which are the regions of interest to the other conferees involved. We propose a Dynamic Sub-Window Skipping (DSWS) scheme to firstly identify the active participants from the multiple incoming encoded video streams by calculating the motion activity of each sub-window, and secondly reduce the frame-rates of the motion inactive participants by skipping these less-important subwindows. The bits saved by the skipping operation are reallocated to the active sub-windows to enhance the regions of interest. We also propose a low-complexity scheme to compose and trace the unavailable motion vectors with a good accuracy in the dropped inactive sub-windows after performing the DSWS. Simulation results show that the proposed methods not only significantly improve the visual quality on the active subwindows without introducing serious visual quality degradation in the inactive ones, but also reduce the computational complexity and avoid whole-frame skipping. Moreover, the proposed algorithm is fully compatible with the H.263 video coding standard. 1

Sodium Fluorescein Staining of the Cornea for the Diagnosis of Dry Eye: A Comparison of Three Eye Solutions

The purpose of this study was to identify which of the eye solutions is best for sodium fluorescein staining of the cornea to diagnose dry eye disease. The study included 173 eyes with suspected or known dry eye disease. The eyes were stained sequentially with sodium fluorescein and each of the following four conditions: balanced salt solution (BSS); BSS and cyclosporine 0.05% emulsion; BSS and lipids containing omega-3; and BSS, cyclosporine 0.05% emulsion, and lipids containing omega-3. Our results showed that compared to BSS alone, artificial tears with cyclosporine 0.05% emulsion and lipids containing omega-3 remain in the cornea for longer periods, thus allowing the clinician to evaluate tear break-up time and visualize corneal punctate erosions