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181.
The variation of current density with bias or temperature is examined for DNA molecules of different configuration. To this end, the DNA molecule is represented as an equivalent electrical network whose behavior is then simulated with PSPICE. The results are found to be in close agreement with ones obtained within a physical model. It is established that the electrical response of a DNA molecule to an applied electric field depends on the boundary conditions and the potential profile along the molecule. This finding should contribute to the creation of a complete library of DNA-molecule configurations with prescribed electrical properties. 相似文献
182.
Self-induced effects in a passive polarization-independent vertical-cavity semiconductor gate are investigated numerically and experimentally. We demonstrate all-optical seed-pulse extraction for synchronization of differential phase-shift keying and ON-OFF keying packets at 10 Gb/s. Our results provide evidence that vertical-cavity gates, exploiting saturable absorption in semiconductor quantum-wells, exhibit attractive performances in terms of efficiency, power consumption, and polarization independency. 相似文献
183.
Seidel A.R. Bisogno F.E. Pinheiro H. do Prado R.N. 《Industrial Electronics, IEEE Transactions on》2003,50(6):1267-1274
This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out. 相似文献
184.
N.S. Chen S.F. Yu 《Photonics Technology Letters, IEEE》2004,16(7):1610-1612
The effect of external optical feedback on the transient response of antiresonant reflecting optical waveguide (ARROW) vertical-cavity surface-emitting lasers (VCSELs) is studied. It can be shown that the proper design of ARROW can suppress the excitation of high-order transverse leaky mode as well as increase the critical feedback strength so that stable high-power single-mode operation of VCSELs can be obtained even under the influence of strong external optical feedback. 相似文献
185.
A mismatch between demand and supply for bandwidth is common in transport carrier networks. This mismatch is generally a result of the disparity between a carrier's capacity buildout and its anticipated customer demand. A carrier with temporary bandwidth deficit or lack of presence in a geographical region and a carrier with surplus capacity in the right locations can be brought together by the emerging bandwidth exchange technology. Bandwidth exchange offers a win-win solution, in which the carrier with a deficit avoids losing revenue by buying capacity from the carrier with surplus, and the latter makes additional revenue by retail sale of its excess capacity. While the concept of real-time purchase and exchange of bandwidth has attracted a lot of attention, many technical challenges stand in the way of making it a reality. The purpose of this article is to provide an engineering framework for enabling real-time bandwidth exchange with committed quality of service and service level agreement among transport carriers. Special emphasis is given to identifying the architectural requirements and the enabling infrastructure necessary for building a viable bandwidth exchange that can be used for creating revenue out of surplus stranded capacity. Indepth analysis of cross-carrier service level agreement specification, capacity publication, route design, and service provisioning are also provided in the article. 相似文献
186.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献
187.
Can digital rights management be standardized? 总被引:1,自引:0,他引:1
With increasing use of the Internet as a content-distribution platform, mere interoperability of the codec is no longer sufficient if content owners are not prepared to distribute their content online for fear of piracy. Therefore, one also needs interoperability in the area of managing and protecting related intellectual property rights. To provide interoperability of digital rights management (DRM) systems to protect the content rather than the distribution channel, MPEG has embarked on developing intellectual property management and protection (IPMP) specifications targeted at the content itself that are natively built into its standards. It is the hope that such standards will allow for interoperability of content commerce systems, giving consumers more choice, while providing rights holders with the tools to effectively protect their assets and to develop complex and attractive business offering to tempt consumers. While it remains uncertain whether standardization is in fact the right vehicle to provide the e-content market with an impetus to grow, it appears that MPEG is working on a set of specifications with relatively good chances of helping to achieve this goal. 相似文献
188.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献
189.
Most comparisons between single carrier and multicarrier modulations assume frequency-domain linear equalization of the channel. We propose a new frequency-domain decision feedback equalizer (FD-DFE) for single carrier modulation, which makes use of a data block transmission format similar to that of the orthogonal frequency-division multiplexing with cyclic prefix (OFDM). The scheme is a nonadaptive DFE where the feedforward part is implemented in the frequency domain, while feedback signal is generated by time-domain filtering. Through simulations in a HIPERLAN-2 scenario, we show that FD-DFE yields a capacity very close to that of OFDM. This result is also confirmed by analytical derivations for a particular case. Furthermore, when no channel loading is considered, FD-DFE performs closely to OFDM for the same averaged frame error rate in a coded transmission. Design methods of the FD-DFE are investigated and a reduced complexity technique is developed, with the result that FD-DFE and OFDM have a similar computational complexity in signal processing 相似文献
190.