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991.
An experimental study of an optical burst switching network based on wavelength-selective optical switches 总被引:1,自引:0,他引:1
Li Xinwan Chen Jianping Wu Guiling Wang Hui Ye Ailun 《Communications Magazine, IEEE》2005,43(5):S3-10
In this article we report the system structure and test results of an experimental optical burst switching network with three edge router's and one core node. Wavelength-selective switches developed for this system and their characteristics are depicted. The implementation and performance of our new scheme for the just-in-time protocol are described. We also report experimental results of FTP and VOD services on this system. Some parameters, including traffic rate, average burst data length, and assembly time, are studied. 相似文献
992.
Peak-to-average power reduction in space division multiplexing based OFDM systems through spatial shifting 总被引:2,自引:0,他引:2
A new method to reduce the peak-to-average power ratio (PAPR) in space division multiplexing systems applying orthogonal frequency division multiplexing is proposed. The method applies spatial shifting to partial transmit sequences to achieve a decreased PAPR on all transmit branches. 相似文献
993.
J. Chen J. B. Xu K. Xue J. An N. Ke W. Cao H. B. Xia J. Shi D. C. Tian 《Microelectronics Reliability》2005,45(1):137-142
Transition-metal compound TiC60 thin films were grown by co-deposition from two separated sources of fullerene C60 powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C60 structure with certain amount of sp3 bonds and a rough surface with a large number of nanoclusters. z–V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm2 and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE. The respective field enhancement factors are estimated to be 99–355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC60 thin films can be ascribed to structural variation of C60 in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C60 matrix. 相似文献
994.
Tsukada T. Hashimoto Y. Sakata K. Okada H. Ishibashi K. 《Solid-State Circuits, IEEE Journal of》2005,40(1):67-79
A decoupling circuit using an operational amplifier is proposed to suppress substrate crosstalk in mixed-signal system-on-chip (SoC) devices. It overcomes the parasitic inductance problem of on-chip capacitor decoupling. The effect of the proposed decoupling circuit is not limited by parasitic fine impedance. A 0.13-/spl mu/m CMOS test chip showed that substrate noise at frequencies from 40 MHz to 1 GHz was incrementally suppressed by sequentially activating three of the proposed circuits in parallel. The power dissipation of each circuit was 3.3 mW at a 1.0-V power supply. The test chip measurement showed that the proposed decoupling reduced crosstalk by 31% at 200 MHz, whereas it was reduced by 4.4% with capacitor decoupling. This 7:1 ratio, or 17 dB, corresponds to the gain of the opamp. Design of the opamp and its feedback loop for active decoupling is simple, making the opamp useful for SoC applications. 相似文献
995.
Video Compression - From Concepts to the H.264/AVC Standard 总被引:10,自引:0,他引:10
Sullivan G.J. Wiegand T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(1):18-31
Over the last one and a half decades, digital video compression technologies have become an integral part of the way we create, communicate, and consume visual information. In this paper, techniques for video compression are reviewed, starting from basic concepts. The rate-distortion performance of modern video compression schemes is the result of an interaction between motion representation techniques, intra-picture prediction techniques, waveform coding of differences, and waveform coding of various refreshed regions. The paper starts with an explanation of the basic concepts of video codec design and then explains how these various features have been integrated into international standards, up to and including the most recent such standard, known as H.264/AVC. 相似文献
996.
An efficient algorithm for the random packing of spheres can significantly save the cost of the preparation of an initial configuration often required in discrete element simulations. It is not trivial to generate such random packing at a large scale, particularly when spheres of various sizes and geometric domains of different shapes are present. Motivated by the idea of compression complemented by an efficient physical process to increase packing density, shaking, a new approach, termed compression algorithm, is proposed in this work to randomly fill any arbitrary polyhedral or cylindrical domains with spheres of various sizes. The algorithm features both simplicity and high efficiency. Tests show that it takes 181 s on a 1.4-GHz PC to complete the filling of a cylindrical domain with a total number of 26,787 spheres, achieving a packing density of 52.89%. 相似文献
997.
Aqueous solutions of five selected non-ionic surfactants: Triton (i-octylphenolethoxylates), Tergitol (2,6,8-trimethyl-4-nonanoloxethylates), Symperonic (n-nonylphenol-oxethylates) and Brij (fatty alcohol ethoxylates) were investigated in this study. Using the bioluminescent bacteria Vibrio fischeri the toxicity of the surfactants solutions were determined. An attempt was made to relate rather low biodegradability of nonionic surfactant solutions measured by the BOD5/COD ratio (ranging from 1 to 17%) to their toxicity. The ozonation process was carried out in a 1.5 dm3 stirred cell reactor equipped with two ozone detectors. The following parameters were analyzed: pH, COD, BOD5, DOC, TOC, polarography as well as UV spectrum. The positive effect of ozonation, represented by decay of UV absorption, was visible in almost complete destruction of the surfactants, with exception of Triton X-705 (only 65% degradation after absorption of 2000 mgO3/dm3). The most striking results were obtained in toxicity tests for ozonated solutions of the non-ionic surfactants – an increase of the bacterial growth inhibition (1.5 to 4 times increase in toxicity due to ozonation). The obtained results were discussed taking into account the literature and our own experimental data on mechanisms of ozonation and biodegradation of non-ionic surfactants of the Triton-type and similar chemical structures. 相似文献
998.
A kinetic model for simulation of the MTO process over SAPO-18 catalyst in a wide range of operating conditions has been proposed. The kinetic model predicts the experimental evolution of reaction products with time on stream, which follows three consecutive periods: initiation (where olefin production increases), a period of maximum olefin production and a period in which this production decreases. The kinetic scheme takes into account these three steps that evolve with time on stream: formation of active intermediate compounds, an step where olefins are formed by reaction of oxygenates (methanol/DME) with these intermediates and deactivation of intermediates by degradation to coke. The presence of water in the reaction medium attenuates the reaction rate of these steps. Discrimination of kinetic equations and calculation of the parameters of best fit have been carried out by solving the mass conservation equations of the individual components of the kinetic scheme together with the kinetic equation for deactivation and taking into account the effect of water on the kinetics of each step. 相似文献
999.
Magnus Rnning Florian Huber Hilde Meland Hilde Venvik De Chen Anders Holmen 《Catalysis Today》2005,100(3-4):249-254
In order to investigate the effect of cerium oxide on Cu–Zn-based mixed-oxide catalysts four catalyst samples were characterized by means of XRD, in situ XANES and thermogravimetric analysis. The activity of the catalyst samples was tested for the forward water–gas shift reaction. Cerium oxide was found to increase the crystallinity of the ZnO phase indicating a segregation of the Cu and ZnO phases. The TOF of the water–gas shift reaction based on chemisorption data was found to be independent of composition and preparation conditions of the four catalyst samples. In contrast, the catalyst stability depends on composition and preparation conditions. Cerium oxide impregnated before calcination of the hydrotalcite-based Cu–Zn precursors leads to a more stable water–gas shift catalyst. 相似文献
1000.
A method of calculating the dynamic deflection of rigidly plastic plates resting on a viscoelastic bed with complex piecewise-smooth support contours composed of sections of straight lines and circles under impact and explosion loading is presented. The general solution, which includes previously known partial solutions for circular and polygonal plates, is obtained. The results of calculation of the deflection of a square hinge-supported plate with rounded corners are presented for the case of the presence and absence of a plastic base.Translated from Problemy Prochnosti, No. 9, pp. 62–66, September, 1991. 相似文献