51,163 research outputs found
Considering Transmission Impairments in Wavelength Routed Networks
No full textAbstract — We consider dynamically reconfigurable wavelength routed networks in which lightpaths carrying IP traffic are on demand established. We face the Routing and Wavelength Assignment problem considering as constraints the physical impairments that arise in all-optical wavelength routed networks. In particular, we study the impact of the physical layer when establishing a lightpath in transparent optical network. Because no signal transformation and regeneration at intermediate nodes occurs, noise and signal distortions due to non-ideal transmission devices are accumulated along the physical path, and they degrade the quality of the received signal. We propose a simple yet accurate model for the physical layer which consider both static and dynamic impairments, i.e., nonlinear effects depending on the actual wavelength/lightpath allocation. We then propose a novel algorithm to solve the RWA problem that explicitly considers the physical impairments. Simulation results show the effectiveness of our approach. Indeed, when the transmission impairments come into play, an accurate selection of paths and wavelengths which is driven by physical consideration is mandatory. I
The identification by Raman microscopy and x-ray diffraction of iron-oxide pigments and of the red pigments found on Italian pottery fragments
No full textThe technique of Raman microscopy has been used to identify and characterise the pigments used in red shards of medieval and earlier items of pottery which have been found in various archaeological sites in the South of Italy. The research has led to the identification, on the basis of their characteristic Raman/resonance Raman spectra, of the red pigments as iron(III) oxide (e.g. Indian Red, Red Ochre or Venetian Red) and the yellow pigments as hydrated iron(III) oxyhydroxide (e.g. Yellow Ochre and Mars Yellow). X-ray powder diffraction experiments confirm the conclusions drawn above
Synthesis and characterization of Q-sized CdS particles in a four-components “water in oil” microemulsion”
No full textEmerging methods for fabricating functional structures by patterning and assembling engineered nanocrystals
No full textInorganic nanocrystals and nanoparticles have aroused increasing attention in the last years due to their original optoelectronic, thermodynamic, mechanical and catalytic properties, which are extremely attractive for fundamental understanding as well as for their huge potential in applications. The ability to strongly exploit the original potential of such nano-objects and access their properties relies on the ability to bridge the gap between the nanoscopic and mesoscopic scale. Indeed, to integrate nanoparticles in structures, materials and finally devices, their incorporation in processable systems, and their organization in morphologically controlled assembly and/or ordered arrays is crucial. The fabrication of 2/3 D patterned micro- and nanostructure is a promising strategy for integrating the nanoparticles in macroscopic entities in order to properly exploit their unprecedented functionality for biomedical, electronic, catalytic materials and devices. In this paper, different and complementary strategies able to engineer inorganic colloidal nanocrystals due to their organization in original functional materials and structures will be described
Reverse micellar systems: self organised assembly as effective route for the synthesis of coll oidal semiconductor nanocrystals
No full textNanoparticles can be obtained by using self-assembly molecules as a template, exploiting confined growth inside the surfactant film of microemulsion system. In this work, the feasibility of using quaternary water-in-oil microemulsion (CTAB/hexane/pentanol/water) to synthesise nanometer-sized structures of semiconductor material (CdS) with desired size distribution is described. Stochastic kinetic simulations have been utilised to account for the observed template effect of the microernulsion aggregate size on the nanocluster growth
Optical properties of nanocomposites based on (CdSe)ZnS core shell nanocrystals in cyclic olefin copolymer
No full textIn this work, organic capped CdSe and (CdSe)ZnS core shell colloidal nanocrystals (NCs), prepared by means of thermolysis of organometallic precursors and with high control on size and size dispersion, were dispersed into a transparent and thermoplastic cyclic olefin copolymer, namely TOPAS, by using toluene as common solvent. The obtained nanocomposite material was deposited by spin coating in thin films that were investigated by UV–vis spectroscopy as well as by TEM analysis. A preliminary comparison of the luminescence properties of CdSe core and (CdSe)ZnS core shell NCs in polymer was carried out. The effect of NC concentration, time and temperature on the optical properties of the composites was determined with the aim of a potential use of these materials for permanent photonic applications. The incorporation of luminescent (CdSe)ZnS NCs in the TOPAS copolymer can be potentially effective for the fabrication of novel optical devices by nanoimprint lithography
Semiconductor nanocrystals/M(II)-phthalocyanine heterojunctions:spectroscopic and photoelectrochemical properties
No full textSynthesis and structural characterisation of CdS nanoparticles prepared in a four components water in oil microemulsion
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