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131.
Optical amplifiers and wavelength-multiplexing technology are transforming lightwave communications by providing cost-effective upgrades that will increase immensely the transmission capacity of long-distance telecommunications networks. A new generation of undersea cable systems using fiber optical amplifiers as repeaters has been developed for transoceanic applications, yielding a capacity almost ten times larger than conventional systems using opto-electronic regenerators. Terrestrial long-haul networks will benefit significantly from amplified wavelength-multiplexed transmission systems designed to access the large inherent bandwidth in the installed fiber. Successful deployment of these advanced systems requires a thorough understanding of optical amplifiers and the optical fiber medium, as their requirements interrelate through optical bandwidth, noise, dispersion, optical nonlinearities, and their impact on signal transmission. While the first commercial WDM amplified lightwave systems are deployed for point-to-point applications, optical transparency and wavelength multiplexing will be exploited for networking leading to the higher functionality and improved cost-effectiveness expected of photonic networks  相似文献   
132.
Many writers have examined the appearance-oriented nature of gay culture. Complementarily, scholars have explored some of the socio-psychological experiences of younger, as well as older, gay men. However, research and theory have not examined communication issues and problems at the intersection of these research domains. Our analysis represents the first systematic attempt to address communication between younger and older gay men in terms of social identity theory and related constructs (such as social comparison and the "black sheep effect") and in light of younger gay men's fears of growing older in a gay culture that places an excessively high value on physical appearance. In line with social identity theory, we suggest that some discrimination against older gay men may be, in part, a social creativity strategy invoked to communicatively enhance compromised self- or sexual-orientation social esteem.  相似文献   
133.
PCB印刷的未来   总被引:1,自引:0,他引:1  
推广应用喷墨打印技术,将推动着PCB生产加工的革命。 喷墨打印是一种不长的技术,目前还限于个人电脑的塑料盒上来生产便宜的有色的图形。这种技术,对于很多工业市场,包括流体制PCB来说,特  相似文献   
134.
Basic mechanisms for the buckling of a thin cylindrical shell under torsional loading are reviewed from a post-buckling perspective. Deflections are considered so far into the large-deflection range that the shell is allowed to fold to a flat two-dimensional form, in a mechanism reminiscent of a deployable structure. Critical and initial post-buckling effects are explored through concepts of energy minimization and hidden symmetries. For comparisons with the final large-deflection folded shape, a truss element program is employed. It is shown that, as buckling develops, the mode shape must change to accommodate both the symmetry-breaking aspects of the predominately inwards deflection, and the rotation of peak and valley lines of the buckle pattern necessary to accommodate the geometry of the final folded shape.  相似文献   
135.
136.
We introduce a general concept for the design of all-optical wavelength converters with pulse reformatting functionality. The novel wavelength converters are based on a single semiconductor optical amplifier followed by an optical filter. A microelectromechanical system-based realization is shown and simultaneous 40 Gb/s wavelength conversion, switching and signal format conversion is demonstrated. The new pulse reformatting optical filter device outperforms current schemes with respect to input-power requirements, input-power dynamic range and signal quality.  相似文献   
137.
Giles  R.C. Reichmann  K.C. 《Electronics letters》1987,23(22):1180-1181
Optical self-homodyne DPSK transmission has been achieved at 1 and 2 Gbit/s data rates with respective receiver sensitivities of ?34.4 dBm and ?32.4 dBm at 10?9 BER. No dispersion penalty was observed after transmission through 86 km of optical fibre with 17 ps/?m/km dispersion at the operating wavelength of 1.53 ?m.  相似文献   
138.
Zusammenfassung Eine allgemeine Theorie zur numerischen Berechnung eines konservativen Systems mitn Freiheitsgraden undm überlagerten Verzweigungspunkten wird dargestellt. Im Unterschied zu früheren Arbeiten wird kein Diagonalisierungsschema der totalen potentiellen Energie benötigt. Ein Störungsschema wird angegeben, umn–m verallgemeinerte Koordinaten mit Hilfe vonn–m Gleichgewichtsbedingungen zu eliminieren. Anschließend wird ein zweites Störungsschema angegeben, um die Ableitungen der 2 m –1 möglichen Äste der Last-Verformungskurven, die im kritischen Punkt entspringen, zu bestimmen. Anschließend wird die Theorie auf zweifache kritische Punkte angewendet, die beim Ausbeulen der durch gleichmäßigen Außendruck belasteten vollständigen Kugelschale auftreten.  相似文献   
139.
Nuclear dissipation in capture reactions is investigated using backtracing, a new analysis protocol. Combining analysis procedure with dynamical models, the difficult and long-standing problem of competition and mixing between quasifission and fusion-fission is solved for the first time. The nature of the relevant dissipation is determined as one-body dissipation. At low excitation energy where shell effects are strongly effective, the shape of the mass distribution could be a powerful check of the nature and the magnitude of the dissipation.  相似文献   
140.
Let G be a graph. If v is a vertex of G then the (? 1, v)-subgraphs of G are defined to be the point deletions of G, except for G ~ {v}, with v labeled on each. This paper first classifies all outerplanar blocks which have a pair of v-isomorphic (? 1, v)-subgraphs and next classifies all outerplanar blocks which have a pair of isomorphic point deletions. Finally, this classification is used to prove the Harary conjecture for outerplanar blocks, namely that an outerplanar block can be reconstructed from the isomorphism classes of its point deletions.  相似文献   
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