11,482 research outputs found

    A wavelength rerouting algorithm in wide-area all-optical networks

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    This paper considers rerouting and minimization of incurred disruption due to rerouting in a wide-area all-optical wavelength division multiplexed (WDM) network with random circuit arrivals and departures. One limitation of such a network is the wavelength continuity constraint imposed by the all-optical cross-connect switches which do not allow a circuit to be placed on a nonwavelength-continuous route. Wavelength rerouting is proposed to rearrange certain existing circuits to create a wavelength-continuous route in order to accommodate a new circuit. To reduce the disruption period, move-to-vacant wavelength-retuning (MTV_WR) is used as the basic operation of circuit migration, in which a circuit is moved to a vacant wavelength on the same path, and parallel MTV WR rerouting is used to reroute multiple circuits. An optimal algorithm is developed to minimize the weighted number of rerouted circuits with parallel MTV_WR rerouting. In our test network, wavelength rerouting can effectively alleviate the wavelength continuity constraint by reducing call blocking probability an average of 30% while reducing the number of rerouted circuits and the disruption period.published_or_final_versio

    Performance of large-size superconducting coil in 0.21T MRI system

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    A high-temperature superconductor (HTS) was used on magnetic resonance imaging (MRI) receiver coils to improve image quality because of its intrinsic low electrical resistivity [1], [2]. Typical HTS coils are surface coils made of HTS thin-film wafers. Their applications are severely limited by the field of view (FOV) of the surface coil configuration, and the improvement in image quality by HTS coil is also reduced as the ratio of sample noise to coil noise increases. Therefore, previous HTS coils are usually used to image small in vitro samples, small animals, or peripheral human anatomies [3]-[5]. We used large-size HTS coils (2.5-, 3.5-, and 5.5-in mean diameter) to enhance the FOV and we evaluated their performance through phantom and human MR images. Comparisons were made among HTS surface coils, copper surface coils, and cool copper surface coils in terms of the signal-to-noise ratio (SNR) and sensitivity profile of the images. A theoretical model prediction was also used to compare against the experimental result. We then selected several human body parts, including the wrist, feet, and head, to illustrate the advantage of HTS coil over copper coil when used in human imaging. The results show an SNR gain of 200% for 5.5-in HTS coil versus same size copper coils, while for 2.5- and 3.5-in coils it is 250%. We also address the various factors that affect the performance of large size HTS coils, including the coil-to-sample spacing due to cryogenic probe and the coil-loading effect.published_or_final_versio

    Mesoscopic phenomena in Au nanocrystal floating gate memory structure

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    Author name used in this publication: K. C. ChanAuthor name used in this publication: P. F. LeeAuthor name used in this publication: J. Y. Dai2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Plasmonic colloidal nanoparticles with open eccentric cavities via acid-induced chemical transformation

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    Surface-enhanced Raman spectroscopy (SERS) has been considered a promising technique for the detection of trace molecules in biomedicine and environmental monitoring. The ideal metal nanoparticles for SERS must not only fulfill important requirements such as high near-field enhancement and a tunable far-field response but also overcome the diffusion limitation at extremely lower concentrations of a target material. Here, we introduce a novel method to produce gold nanoparticles with open eccentric cavities by selectively adapting the structure of non-plasmonic nanoparticles via acid-mediated surface replacement. Copper oxide nanoparticles with open eccentric cavities are first prepared using a microwave-irradiation-assisted surfactant-free hydrothermal reaction and are then transformed into gold nanoparticles by an acidic gold precursor while maintaining their original structure. Because of the strong near-field enhancement occurring at the mouth of the open cavities and the very rough surfaces resulting from the uniformly covered hyperbranched sharp multi-tips and the free access of SERS molecules inside of the nanoparticles without diffusion limitation, adenine, one of the four bases in DNA, in an extremely diluted aqueous solution (1.0 pM) was successfully detected with excellent reproducibility upon laser excitation with a 785-nm wavelength. The gold nanoparticles with open eccentric cavities provide a powerful platform for the detection of ultra-trace analytes in an aqueous solution within near-infrared wavelengths, which is essential for highly sensitive, reliable and direct in vivo analysis.None1132sciescopu

    Effects of fear-avoidance beliefs on Chinese patients with neck pain.

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    Key Messages 1. The Chinese version of the Fear-Avoidance Beliefs Questionnaire (FABQ) has good content validity, testretest reliability, internal consistency, construct validity, responsiveness, and factor structure. Thus, fear-avoidance beliefs can be used in Chinese patients with neck pain. 2. The validated FABQ facilitates future research on the effects of fear-avoidance behaviour on patients with neck pain and hence a better service for and evaluation of patients with neck pain can be provided. It may also facilitate cross-cultural studies on this common problem between western and Chinese populations. 3. The construct of fear-avoidance beliefs can be applied to patients with neck pain. 4. The fear-avoidance beliefs are an important psychosocial measure in predicting future disability level and return to complete work capacity (immediately and 3 months after physiotherapy).published_or_final_versio

    Multi-pulse addressing of a Raman quantum memory: configurable beam splitting and efficient readout

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    Quantum memories are vital to the scalability of photonic quantum information processing (PQIP), since the storage of photons enables repeat-until-success strategies. On the other hand the key element of all PQIP architectures is the beam splitter, which allows to coherently couple optical modes. Here we show how to combine these crucial functionalities by addressing a Raman quantum memory with multiple control pulses. The result is a coherent optical storage device with an extremely large time-bandwidth product, that functions as an array of dynamically configurable beam splitters, and that can be read out with arbitrarily high efficiency. Networks of such devices would allow fully scalable PQIP, with applications in quantum computation, long-distance quantum communications and quantum metrology.Comment: 4 pages, 3 figure

    Excess Enthalpies of Mixing of Binary Mixtures of NaCl, KCl, NaBr and KBr in Mixed Ternary Solvent Systems at 298.15 K

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    Excess enthalpies of mixing for six possible binary combinations of solutions of NaCl, KCl, NaBr and KBr in mixed ternary solvents composed of formamide, 1,4-dioxane and water have been determined using a flow microcalorimeter at constant ionic strengths of 0.500 and 1.000 mol kg–1 at 298.15 K. Unlike the case of water, the data do not supportYoung’s cross square rule. Pitzer’s virial coefficient theory has been utilized to obtain binary and ternary interaction parameters, i.e. θH and ψH. The data were also analysed in terms of the Friedman model and it was found that interactions between solvated ions are dictated not only by coulombic interactions but also by appreciable asymmetric effects.Keywords: Enthalpy of mixing, ternary solvents, Pitzer theory, Friedman model, cross square rule

    3D simulation of morphological effect on reflectance of Si3N4 sub-wavelength structures for silicon solar cells

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    In this study, we investigate the reflectance property of the cylinder, right circular cone, and square pyramid shapes of silicon nitride (Si3N4) subwavelength structure (SWS) with respect to different designing parameters. In terms of three critical factors, the reflectance for physical characteristics of wavelength dependence, the reflected power density for real power reflection applied on solar cell, and the normalized reflectance (reflected power density/incident power density) for real reflectance applied on solar cell, a full three-dimensional finite element simulation is performed and discussed for the aforementioned three morphologies. The result of this study shows that the pyramid shape of SWS possesses the best reflectance property in the optical region from 400 to 1000 nm which is useful for silicon solar cell applications
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