电信级以太网在海外市场的应用案例研究

电信级以太网可以在单一网络上传输语音、视频和互联网接入业务,并允许更高集成度的应用,比如桌面的语音和视频会议、语音中附加各种丰富数据、即时消息服务集成等各种应用.电信级以太网被赋予更高的传输和处理速度、更小的时延和更高的可靠性,可以在远程和安全等应用中加强网络的存储能力,完善网络的虚拟化,增强服务器的性能.这些因素也使用于外部服务和内部解决方案的快速灾难备份成为可能.     

Linewidth measurements and phase locking of Josephson oscillatorsusing RSFQ circuits

We present a technique for linewidth measurement and phase-locking of Josephson oscillators using digital rapid single-flux-quantum (RSFQ) circuits. The oscillator consists of a resistively shunted 6 μm×6 μm Nb/AlO_x/Nb Josephson tunnel junction that is integrated with RSFQ input and output circuits. A cascade of RSFQ T flip-flops is used to directly monitor the output of the Josephson oscillator. Spectral characteristics have been measured directly for oscillator frequencies ranging from 10-50 GHz. The linewidth can be reduced by over 100 times by phase-locking the oscillator to an RSFQ pulse train generated by an external sinusoidal signal. These Josephson oscillators can be used as on-chip stable high frequency clocks for RSFQ circuits     

Josephson effect gain and noise in SIS mixers

The authors report measurements of gain and noise in SIS mixers at 230 and 492 GHz. Measurements were made of relatively high gain and noise associated with Josephson currents that have not been previously reported. These measurements show that Josephson currents are increasingly important as operating frequencies are raised. The techniques used to make these measurements are discussed. Measurements made with hot and cold black-bodies are shown to be inaccurate at high frequencies. The problem is that SIS mixers do not always respond linearly to the signal power incident on them. This is particularly important when (1) very broad band mixers are used and (2) Josephson effect currents are important. Both of these circumstances are present in the quasioptical SIS mixers favored for 500 GHz and higher. Monochromatic signals were used to measure gain and noise to get around these problems     

An oscillatory flow phenomenon in microtube flows of thermally responsive fluids

A simple asymptotic model for the flow of a thermally responsive fluid in a microtube is derived. At low temperatures these fluids behave as a Newtonian fluid; however, above a critical temperature they (reversibly) form gel-like structures. Also, because of the small length scales involved in microfluidic flows, viscous heating can become significant. This can lead to gelation simply from the temperature change due to viscous heating. Our model takes into account viscous heating, as well as possible conduction through the channel walls. The rheology of the thermally responsive fluid is modelled using a bi-viscosity model, with the gel phase being represented by a constant large viscosity. The model is then used to show that, when the viscous heating exceeds a critical level, an oscillatory flow behaviour can occur. These oscillations eventually become damped out as the system reaches a steady state; however, the time it takes for this to occur can become excessively large. The physical mechanisms that cause the oscillatory behaviour are examined, and the criteria for the oscillatory flow to occur are determined. Some analysis of the oscillations and the timescales involved therein are also presented.     

Regulatory practice and politics: Lessons from independent regulation in Indian electricity

Although independent regulatory agencies are emerging worldwide, there remains little understanding about how they operate in practice, particularly in developing countries. This paper seeks to examine the practice of electricity regulation in India, using case studies of three state-level electricity regulators. Based on documentary analysis and interviews with regulators, government, utilities and stakeholders, the paper examines how regulation is shaped by institutional and political context, how regulators make decisions in practice, and how they engage with stakeholders and with what effects.Based on the Indian experience, we suggest that in a rapidly changing electricity sector, the separation between the political and economic content of regulatory decisions, as is often advocated, may not be feasible or indeed desirable. Instead, we suggest a more proactive regulatory approach where governments give regulators the latitude to proactively steer the sector. For this approach to be viable, regulators need to build adequate technical capacity, institutional legitimacy, and democratic legitimacy in their dealings with stakeholders. This approach entails a bolder, and more challenging vision of regulation, but one that promises greater transformational potential than does the model of technocratic and apolitical regulation.     

Eigenspectra for flocculation quality estimation

We present an image analysis algorithm for flocculation quality estimation in high-solids slurries, and demonstrate its performance using inline process images of oil sands tailings flocculation. While a skilled human operator can often successfully evaluate such images, variations in feed as well as the lack of isolated flocs or spatial reference-points inherent in a high-solids slurry can cause conventional image analysis techniques to fail. We overcome these challenges by recasting the images in Fourier space, discarding phase information, and applying an eigenfaces-inspired image recognition algorithm to the resulting spectra. Each image is represented using a few projection coefficients onto an orthogonal basis and evaluated using likelihood-based classification schemes. This algorithm shows a high degree of success evaluating the flocculation quality of 129 batch and inline flocculation experiments (5,610 images total) utilizing feed tailings from two different oil sand producers at a variety of feed dilutions and flocculant dosing levels.     

Cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode

The cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode, with graded bandgap layers at the heterostructure interfaces, was investigated for the first time. DC measurements show that the dark current of the diode decreases sharply as the temperature decreases from 300 to 200 K. A factor of 1000 in dark current reduction was found for this photodiode, when it was cooled from room temperature to about 150 K. Similar modulation bandwidths were found for this device for temperatures between 9 and 300 K, with a bandwidth greater than 20 GHz. No degradation was found in performance at cryogenic temperature compared to room temperature. This enables direct integration of high-speed photodiodes with superconductive and other cryogenic electronics