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951.
Goel S. Elgamel M.A. Bayoumi M.A. Hanafy Y. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(4):867-878
Scaling down to deep submicrometer (DSM) technology has made noise a metric of equal importance as compared to power, speed, and area. Smaller feature size, lower supply voltage, and higher frequency are some of the characteristics for DSM circuits that make them more vulnerable to noise. New designs and circuit techniques are required in order to achieve robustness in presence of noise. Novel methodologies for designing energy-efficient noise-tolerant exclusive-OR-exclusive- NOR circuits that can operate at low-supply voltages with good signal integrity and driving capability are proposed. The circuits designed, after applying the proposed methodologies, are characterized and compared with previously published circuits for reliability, speed and energy efficiency. To test the driving capability of the proposed circuits, they are embedded in an existing 5-2 compressor design. The average noise threshold energy (ANTE) is used for quantifying the noise immunity of the proposed circuits. Simulation results show that, compared with the best available circuit in literature, the proposed circuits exhibit better noise-immunity, lower power-delay product (PDP) and good driving capability. All of the proposed circuits prove to be faster and successfully work at all ranges of supply voltage starting from 3.3 V down to 0.6 V. The savings in the PDP range from 94% to 21% for the given supply voltage range respectively and the average improvement in the ANTE is 2.67X. 相似文献
952.
M. J. O’Sullivan C. G. Walker M. L. O’Sullivan T. D. Thompson A. B. Philpott 《Telecommunication Systems》2006,33(4):353-376
The problem of designing fibre-optic networks for local-access telecommunications generates (at least) three non-trivial subproblems.
In the first of these subproblems one must determine how many fibre-optic cables (fibres) are required at either end of a
street. In the next subproblem a minimum-cost network must be designed to support the fibres. The network must also provide
distinct paths from either end of the street to the central exchange(s). Finally, the fibre-optic cables must be placed in
protective covers. These covers are available in a number of different sizes, allowing some flexibility when covering each
section of the network. In this paper we describe a dynamic programming (DP) formulation for finding a minimum-cost (protective)
covering for the network (the third of the subproblems). This problem is a generalised set covering problem with side constraints
and is further complicated by the introduction of fixed and variable welding costs. The DP formulation selects covers along
each arc (in the network), but cannot exactly model the fixed costs and so does not guarantee optimality. We also describe
an integer programming (IP) formulation for assessing the quality of the DP solutions. The cost of the networks constructed
by the IP model is less than those designed using the DP model, but the saving is not significant for the problems examined
(less than 0.1%). This indicates that the DP model will generally give very good solutions. Furthermore, as the problem dimensions
grow, DP gives significantly better solution times than IP. 相似文献
953.
Supermedia-enhanced Internet-based telerobotics 总被引:4,自引:0,他引:4
Elhajj I. Ning Xi Wai Keung Fung Yun-Hui Liu Hasegawa Y. Fukuda T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(3):396-421
This paper introduces new planning and control methods for supermedia-enhanced real-time telerobotic operations via the Internet. Supermedia is the collection of video, audio, haptic information, temperature, and other sensory feedback. However, when the communication medium used, such as the Internet, introduces random communication time delay, several challenges and difficulties arise. Most importantly, random communication delay causes instability, loss of transparency, and desynchronization in real-time closed-loop telerobotic systems. Due to the complexity and diversity of such systems, the first challenge is to develop a general and efficient modeling and analysis tool. This paper proposes the use of Petri net modeling to capture the concurrency and complexity of Internet-based teleoperation. Combined with the event-based planning and control method, it also provides an efficient analysis and design tool to study the stability, transparency, and synchronization of such systems. In addition, the concepts of event transparency and event synchronization are introduced and analyzed. This modeling and control method has been applied to the design of several supermedia-enhanced Internet-based telerobotic systems, including the bilateral control of mobile robots and mobile manipulators. These systems have been experimentally implemented in three sites test bed consisting of robotic laboratories in the USA, Hong Kong, and Japan. The experimental results have verified the theoretical development and further demonstrated the stability, event transparency, and event synchronization of the systems. 相似文献
954.
Mantooth B.A. Weiss P.S. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(11):1785-1802
One of the ultimate miniaturizations in nanotechnology is molecular electronics, where devices will consist of individual molecules. There are many complications associated with the use of molecules in electronic devices, such as the electronic perturbations in the molecule associated with being bonded to an electrode, how electrons traverse the metal-molecule junction, and the difficulty of macroscopically addressing single to very few molecules. Whether fabricating a test structure or a usable device, the use of self-assembly is fundamental to the fabrication of molecular electronic devices. We will discuss how to fabricate self-assembled monolayers into test assemblies and how to use intermolecular interactions to direct molecules into desired positions to create nanostructures and to connect functional molecules to the outside world. These assemblies serve as test structures for measurements on single or bundled molecules. The development of several experimental techniques, including various scanning probes, mercury drop junctions, break junctions, nanopores, crossed wires, and other techniques using nanoparticles have enabled the ability to test these structures and make reproducible measurements on single molecules. Many of these methods have been developed to test molecules with potential for integration into devices such as oligo (phenylene-ethynylene) molecules and other /spl pi/-conjugated molecules, in ensemble or single-molecule measurements. 相似文献
955.
G. Casalbore‐Miceli M.C. Gallazzi S. Zecchin N. Camaioni A. Geri C. Bertarelli 《Advanced functional materials》2003,13(4):307-312
Voltammetric and spectrophotometric measurements of poly(3,3″‐dipentoxy‐3′‐dicyanoethenyl‐2,2′:5′,2″‐terthiophene) (polyCN) films, in connection with other experimental evidence, reveal a normal oxidative, but a peculiar reductive behavior consisting of trapping of the negative charge during the cathodic scan. Another interesting property of polyCN films is the tendency to form strong intramolecular and intermolecular associations, probably charge‐transfer (CT) complexes. These properties could account for the fact that the photovoltaic performance does not improve when polyCN is blended with a polythiophene donor. 相似文献
956.
Nobel A.B. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(1):83-98
This paper considers several aspects of the sequential prediction problem for unbounded, nonstationary processes under pth power loss /spl lscr//sub p/(u,v)=|u-v|/sup p/, 1
相似文献
957.
A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise 总被引:1,自引:0,他引:1
Mizuochi T. Ishida K. Kobayashi T. Abe J. Kinjo K. Motoshima K. Kasahara K. 《Lightwave Technology, Journal of》2003,21(9):1933-1943
We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise. 相似文献
958.
As already documented in the literature, fractal image encoding is a family of techniques that achieves a good compromise between compression and perceived quality by exploiting the self-similarities present in an image. Furthermore, because of its compactness and stability, the fractal approach can be used to produce a unique signature, thus obtaining a practical image indexing system. Since fractal-based indexing systems are able to deal with the images in compressed form, they are suitable for use with large databases. We propose a system called FIRE, which is then proven to be invariant under three classes of pixel intensity transformations and under geometrical isometries such as rotations by multiples of /spl pi//2 and reflections. This property makes the system robust with respect to a large class of image transformations that can happen in practical applications: the images can be retrieved even in the presence of illumination and/or color alterations. Additionally, the experimental results show the effectiveness of FIRE in terms of both compression and retrieval accuracy. 相似文献
959.
Self-organized public-key management for mobile ad hoc networks 总被引:6,自引:0,他引:6
In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories are not well-suited for securing ad hoc networks. We propose a fully self-organized public-key management system that allows users to generate their public-private key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, our approach does not require any trusted authority, not even in the system initialization phase. 相似文献
960.
Performance limitation due to statistical Raman crosstalk in a WDM system with multiple-wavelength bidirectionally pumped Raman amplification 总被引:1,自引:0,他引:1
A general theoretical model of statistical Raman crosstalk and its impact on system performance in a multiwavelength bidirectionally pumped Raman fiber amplifier (RFA) is developed for the first time, where we have taken modulation statistics, dispersion-induced pulse walk-off and signal-induced pump depletion into account. Two kinds of statistical Raman crosstalk, from signal-induced forward-pump depletion and from signal-signal Raman interaction, are included in one model. Formulas for normalized Raman crosstalk, Raman crosstalk-induced relative intensity noise spectral density, and its variance and system performance impact in terms of Q penalty are presented for both a single-span system and a dispersion-compensated multispan wavelength-division-multiplexed (WDM) link. Based on these formulas, we numerically investigate the impact of Raman crosstalk on system performance in a three-wavelengths bidirectionally pumped 40 /spl times/ 40-Gb/s WDM system for various fiber types. In addition, Raman crosstalk in a four-wavelength bidirectionally pumped RFA was experimentally measured. The results agree well with our theory. 相似文献