Research advances in cognitive ultra wide band radio and their application to sensor networks

The paper illustrates the novel concept of Cognitive UWB Radio, a wireless system based on UWB transmission able to self-adapt to the characteristics of the surrounding environment. First, salient features of UWB transmission are reviewed, and then, application of UWB characteristics to the problem of cognitive radio systems is discussed. Current ongoing studies and achieved results on a possible physical layer based on Prolate Spheroidal Wave Functions and consistent with the Cognitive UWB Radio paradigm are presented and analyzed, and their application to the sensor network scenario is discussed.     

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.     

Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation

Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r ₂ ≈ 835 mm ^?1 s^?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r ₂ relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg^?1 animal) as compared to current practice.     

SCR operation mode of diode strings for ESD protection

Diodes and diode strings in 90 nm and beyond technologies are investigated by measurement and device simulation. After a thorough calibration, the device simulator is utilised to achieve a better understanding and an enhanced device performance of diode strings under static and transient ESD conditions. Thereto, parasitic transistors and a so far neglected parasitic thyristor (SCR) in the diode string are regarded, exploited and optimised.     

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.     

Interferential lithography of 1D thin metallic sinusoidal gratings: Accurate control of the profile for azimuthal angular dependent plasmonic effects and applications

Nonlinear processes involved in the manufacture of nominally sinusoidal surface relief diffraction gratings generated by interference lithography can introduce distortions into the profile of these surfaces. Such distortions may dramatically affect both the specular reflectivity and diffracted efficiencies from such a surface [H. Raether, Phys. Thin Film 9 (1977) 145–261]. We shall consider in particular the case of metallic gratings used to investigate plasmonic effects that can be engineered for bio-sensing applications. To investigate these effects, interference lithography (IL) has been used for the generation of profile controlled sinusoidal plasmonic crystals. IL exposure contrast study has been performed to control the amplitude oscillation and the surface roughness quality. Bi-metallic layer of silver and gold have been systematically deposited with different film thicknesses. A comprehensive numerical model that studies the optical coupling to surface plasmon polaritons on Ag/Au gratings has been undertaken for the simulation of the reflectivity and azimuthal angle dependence [Z. Chen, I.R. Hooper, J.R. Sambles, J. Opt. A: Pure Appl. Opt. 10 (1) (2008) 015007]. This computation illustrates the sensitivity of individual features to specific harmonic components of the surface, for surface plasmon resonances recorded in both the zeroth and higher diffracted orders. The roughness surface control after development and after bi-metallic evaporation strongly contributes to tighten the width of the reflectivity peak. Optimization process has shown that for an Ag (37 nm) and Au (7 nm) metallic bilayer, a semi-amplitude of 20 nm provides the best reflectivity.