Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.     

新型自振荡电源转换器VK05CFL

1.技术概述 VK05CFL是一种用于驱动微型荧光灯的自振荡转换器,采用意法半导体的VIPower M3-3专利技术制造而成,允许在同一芯片上集成控制部分和电源级。电源级是一个“发射器开关”,其构成是在级联配置内放置一个双极高压复合晶体管和一个低压MOSFET,因此,在高击穿电     

Improved transparency in energy-based bilateral telemanipulation

In bilateral telemanipulation algorithms based on enforcing time-domain passivity, internal friction in the devices poses an additional energy drain. This can severely decrease the obtainable transparency of these algorithms when high amounts of friction are present in the slave device. Based on a model of the friction, the dissipated energy can be estimated and reclaimed inside the energy balance of the control algorithm. Extending the energy balance which is monitored, decreases the net passivity of the telemanipulation system enforced by the control algorithm, which usually enforces passivity of just the bilateral controller. Experimental results are provided that demonstrate the effectiveness of the proposed approach in increasing the obtainable transparency. As long as the physically dissipated energy is underestimated, the telemanipulation system as a whole will remain passive. Thus the guaranteed stability property of the time-domain passivity algorithm is maintained.     

Soft‐Lithographed Up‐Converted Distributed Feedback Visible Lasers Based on CdSe–CdZnS–ZnS Quantum Dots

The development of a solution‐deposited up‐converted distributed feedback laser prototype is presented. It employs a sol–gel silica/germania soft‐lithographed microcavity and CdSe–CdZnS–ZnS quantum dot/sol–gel zirconia composites as optical gain material. Characterization of the linear and nonlinear optical properties of quantum dots establishes their high absorption cross‐sections in the one‐ and two‐ photon absorption regimes to be 1 × 10^?14 cm² and 5 × 10⁴ GM, respectively. In addition, ultrafast transient absorption dynamics measurements of the graded seal quantum dots reveal that the Auger recombination lifetime is 220 ps, a value two times higher than that of the corresponding CdSe core. These factors enable the use of such quantum dots as optically pumped gain media, operating in the one‐ and two‐photon absorption regime. The incorporation of CdSe–CdZnS–ZnS quantum dots within a zirconia host matrix affords a quantum‐dot ink that can be directly deposited on our soft‐lithographed distributed feedback grating to form an all‐solution‐processed microcavity laser.     

Self‐Assembly of Atomically Thin Chiral Copper Heterostructures Templated by Black Phosphorus

The fabrication of 2D systems for electronic devices is not straightforward, with top‐down low‐yield methods often employed leading to irregular nanostructures and lower quality devices. Here, a simple and reproducible method to trigger self‐assembly of arrays of high aspect‐ratio chiral copper heterostructures templated by the structural anisotropy in black phosphorus (BP) nanosheets is presented. Using quantitative atomic resolution aberration‐corrected scanning transmission electron microscopy imaging, in situ heating transmission electron microscopy and electron energy‐loss spectroscopy arrays of heterostructures forming at speeds exceeding 100 nm s^?1 and displaying long‐range order over micrometers are observed. The controlled instigation of the self‐assembly of the Cu heterostructures embedded in BP is achieved using conventional electron beam lithography combined with site specific placement of Cu nanoparticles. Density functional theory calculations are used to investigate the atomic structure and suggest a metallic nature of the Cu heterostructures grown in BP. The findings of this new hybrid material with unique dimensionality, chirality, and metallic nature and its triggered self‐assembly open new and exciting opportunities for next generation, self‐assembling devices.     

Security and delay issues in SIP systems

The deployment of multimedia over IP (MoIP), and in particular voice over IP services, requires to solve new security issues they introduce, before completely exploiting the great opportunities they offer to telecommunication market. Furthermore, the implementation of various security measures can cause a marked deterioration in quality of service, which is fundamental to the operation of an MoIP network that meets users' quality expectations. In particular, because of the time‐critical nature of MoIP and its low tolerance for disruption and packet loss, many security measures implemented in traditional data networks are simply not applicable in their current form. This paper presents an analysis of the security options of Session Initiation Protocol‐ (SIP)‐based MoIP architecture aimed at evaluating their impact on delay. In particular, each security option is analyzed in terms of clock cycles needed to perform the related operations. This parameter could be used to estimate the delay introduced by the security mechanisms. Moreover the paper proposes a rigorous definition of five security profiles, which provide different levels of security to a MoIP system. Copyright © 2009 John Wiley & Sons, Ltd.     

Fast full-search equivalent template matching by enhanced bounded correlation.

We propose a novel algorithm, referred to as enhanced bounded correlation (EBC), that significantly reduces the number of computations required to carry out template matching based on normalized cross correlation (NCC) and yields exactly the same result as the full search algorithm. The algorithm relies on the concept of bounding the matching function: finding an efficiently computable upper bound of the NCC rapidly prunes those candidates that cannot provide a better NCC score with respect to the current best match. In this framework, we apply a succession of increasingly tighter upper bounding functions based on Cauchy-Schwarz inequality. Moreover, by including an online parameter prediction step into EBC, we obtain a parameter free algorithm that, in most cases, affords computational advantages very similar to those attainable by optimal offline parameter tuning. Experimental results show that the proposed algorithm can significantly accelerate a full-search equivalent template matching process and outperforms state-of-the-art methods.     

Software‐defined network‐based prioritization to avoid video freezes in HTTP adaptive streaming

HTTP adaptive streaming (HAS) is becoming the de facto standard for video streaming services over the Internet. In HAS, each video is segmented and stored in different qualities. Rate adaptation heuristics, deployed at the client, allow the most appropriate quality level to be dynamically requested, based on the current network conditions. It has been shown that state‐of‐the‐art heuristics perform suboptimal when sudden bandwidth drops occur, therefore leading to freezes in the video playout, the main factor influencing users' quality of experience (QoE). This issue is aggravated in case of live events, where the client‐side buffer has to be kept as small as possible in order to reduce the playout delay between the user and the live signal. In this article, we propose a framework capable of increasing the QoE of HAS clients by reducing video freezes. The framework is based on OpenFlow, a widely adopted protocol to implement the software‐defined networking principle. An OpenFlow controller is in charge of introducing prioritized delivery of HAS segments, based on the network conditions and the HAS clients' status. Particularly, the HAS clients' status is obtained without any explicit clients‐to‐controller communication, and thus, no extra signaling is introduced into the network. Moreover, this OpenFlow controller is transparent to the quality decision process of the clients, as it assists the delivery of the segments, but it does not determine the actual quality to be requested. In order to provide a comprehensive analysis of the proposed approach, we investigate the performance of the proposed OpenFlow‐based framework in the presence of realistic Internet cross‐traffic. Particularly, we model two types of applications, namely, HTTP web browsing and progressive download video streaming, which currently represent the majority of Internet traffic together with HAS. By evaluating this novel approach through emulation in several multi‐client scenarios, we show how the proposed approach can reduce freeze time for the HAS clients due to network congestion up to 10 times compared with state‐of‐the‐art heuristics, without impacting the performance of the cross‐traffic applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of the si-conducting polymer interfacial properties using A-C impedance techniques

A study was made of the interfacial properties of Poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of “Quasi-Ohmic” and “non-Ohmic” contacts, respectively, of PP(C1O₄) and PP films doped with other counterions (BF₄ and para-toluene sulfonate) with p-Si, are explained in-terms of the conductivity of these films and the flat band potential,V _fb, of PP relative to that ofp-Si. The PP film seems to passivate or block intrinsic surface states present on thep-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and C1O₄ doped PP are compared.     

Carbon nanotubes/polydimethylsiloxanes systems for thermal management of miniaturized electronic components

The thermal performances of nanocomposite layers formed by Single-walled Carbon Nanotubes (SWCNT) dispersed in 2 different kind of polydimethyl-siloxane (PDMSO) matrices has been investigated by measuring the thermal resistance under conditions similar to the ones used for thermal management in microelectronics. A series of nanocomposite samples with thickness in the range 25 microm(-1) cm have been tested. The nanocomposites were prepared varying the amounts of nanotubes embedded in the matrix (from 0.1 to 5%w). In some cases also microsized graphites were mixed to the nanotube's fillers. For 25 micron thick layers, the thermal resistance of the neat silicone specimen can be reduced of 54% with the addition of 2%w carbon nanotubes. The variation of thermal conductivity as a function of the SWCNT's loading is reported and discussed. Furthermore the dispersion's effects of the nanotubes in the layers and the effects on the realization of a net-like system have been investigated.