Search results for " light"
showing 10 items of 1141 documents
A Hardware and Secure Pseudorandom Generator for Constrained Devices
2018
Hardware security for an Internet of Things or cyber physical system drives the need for ubiquitous cryptography to different sensing infrastructures in these fields. In particular, generating strong cryptographic keys on such resource-constrained device depends on a lightweight and cryptographically secure random number generator. In this research work, we have introduced a new hardware chaos-based pseudorandom number generator, which is mainly based on the deletion of an Hamilton cycle within the $N$ -cube (or on the vectorial negation), plus one single permutation. We have rigorously proven the chaotic behavior and cryptographically secure property of the whole proposal: the mid-term eff…
Influence of temperature on the synthesis of thiol-stabilized CdTe nanoparticles in aqueous solutions
2010
We have investigated the evolution of thiol-capped cadmium telluride nanocrystals prepared in aqueous solutions at low and room temperature followed by heating at 50–100 °C. The UV–visible absorption spectra, as well as transmission electron microscopy, atomic force microscopy, and dynamic light scattering observations made it possible to reveal differences in size and structure originating from different heating temperatures. It was shown that minimization of the nucleation process temperature provided formation of larger nanoparticles than at higher temperatures.
FLUORINATED DERIVATIVES OF A POLYASPARTAMIDE BEARING POLYETHYLENE GLYCOL CHAINS AS OXYGEN CARRIERS
2008
Abstract In this paper the synthesis and characterization of new fluorinated polymers based on a polyaspartamide bearing polyethylene glycol (PEG) chains, are reported. The starting material was the α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHEA), a water soluble and biocompatible polymer, that has been derivatized with both polyethylene glycol (with a molecular weight of 2000 Da) and 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole. By varying the amount of the fluorinated oxadiazole, three samples have been prepared and characterized by FT-IR, 1H NMR, 19F NMR and UV–VIS spectroscopy. Size exclusion chromatography analysis of these copolymers revealed the occurrence of a self-asso…
Extended Investigation of the Aqueous Self-Assembling Behavior of a Newly Designed Fluorinated Surfactant
2009
The physicochemical behavior of the newly synthesized fluorinated 5-hydroxyamino-3-perfluoroheptyl-1,2,4-oxadiazin-6-one (PFHO) surfactant was investigated. Thermal analysis showed that the pure surfactant is thermally stable under an inert atmosphere to 135 degrees C, which is several degrees higher than the melting point (99 degrees C). PFHO is rather active at the water/air interface where it assumes a standing up configuration. It exhibits an enhanced self-assembling behavior; accordingly, the critical micellar concentrations at some temperatures are 2 orders of magnitude lower than those of a similar surfactant having the same phobicity, such as sodium perfluorooctanoate. Even in the d…
Solubilization of an Organic Solute in Aqueous Solutions of Unimeric Block Copolymers and Their Mixtures with Monomeric Surfactant: Volume, Surface T…
2008
The ability of aqueous systems, formed by unimeric copolymers and their mixtures with a monomeric surfactant, in solubilizing large quantities of 1-nitropropane (PrNO2) was explored. The copolymers are F68 and L64, which differ for the hydrophilicity, and the surfactant is sodium dodecanoate. For a better understanding of the mechanism of solubilization, thermodynamic (volume and differential scanning calorimetry), spectroscopy (steady-state fluorescence), viscosity, and interfacial investigations were carried out. PrNO2 causes the micellization of the unimeric copolymer, and the required amount of PrNO2 depends on the composition, the copolymer nature, and the temperature. Large quantities…
Structural Characterization of Zirconia Nanoparticles Prepared by Microwave-Hydrothermal Synthesis
2009
Nanocrystalline zirconia powders have been prepared by microwave-hydrothermal synthesis starting from aqueous solution of ZrOCl2·8H2O. Results of investigations on the aqueous suspension stability of the washed zirconia nanopowders by dynamic light scattering showed that the suspension, constituted by superaggregates of nanoparticles (131 ± 10 nm), was stable up to 15 days. Nanopowders were investigated by means of transmission electron microscopy and small angle x-ray scattering measurements which proved that the zirconia nanopowder is constituted by small primary nanoparticles of ca. 8 nm that agglomerate forming bigger aggregates of 50 ± 1 nm.
Static and dynamic light scattering by aqueous polyelectrolyte solutions: effect of molecular weight, charge density and added salt
1990
Abstract Aqueous solutions of quaternized poly(2-vinylpyridine) were investigated by static (SLS) and dynamic (DLS) light scattering over a wide range of polyelectrolyte, c pe , and salt concentrations, c s (10 −3 ≤ c pe ≤ 10 2 gl −1 , 10 −5.5 ≤ c s ≤ 10 −1 moll −1 ). Using DLS the cooperative diffusion coefficient D was measured as a function of c pe and c s . D exhibits a characteristic behaviour in each of three different concentration regimes. In the ‘dilute lattice’ regime, where λ = c pe c s ⪡ 1 , one diffusion coefficient is observed. In the transition regime, where λ ≈ 1, D increases with increasing polyelectrolyte concentration and a slow diffusive mode gradually appears. For λ ⪢ 1…
Sources of geomaterials in the Sicani Mountains during the Early Middle Ages: A case study of Contrada Castro, central western Sicily
2022
From 2017, an unknown rural settlement in Contrada Castro at Corleone (Palermo Province, western Sicily) was investigated as part of the `Harvesting Memories Project¿. The stratigraphic sequence, supported by radiocarbon dating, has demonstrated a reoccupation of a pre-Roman site during the transition between the Byzantine and Islamic periods. In particular, the main occupation occurred in the late 8th¿9th century when pottery kilns and a probable warehouse were constructed. During the 10th¿11th century, a new structure with different orientations replaced the previous buildings that had already collapsed. Specifically focusing on a perspective of the household production and its relationsh…
Persistenza della thòlos nell’architettura contemporanea
2020
La thòlos è una costruzione che può essere assunta come un inizio dell’architettura e che definisce principi che stanno oltre la storia e l’archeologia: rappresenta un archetipo legato al mondo litico, proveniente dall’oriente e diffuso sin dall’età greco-arcaica in tutto il Mediterraneo. Custodisce memorie di epoche mitiche e forme che affiorano con continuità nell’architettura, attraversa la storia e persiste nella modernità soprattutto negli spazi di culto e celebrativi. Lo spazio della thòlos consente di riprendere nel progetto contemporaneo alcuni temi i cui esiti conducono ad una architettura che è in antitesi alla continuità visiva interno-esterno e all’assenza di confini, che all’in…
Smart lighting in a historic context: a case study
2017
Purpose The purpose of this paper is to address a project for lighting an old town in Italy. Its originality lies in the holistic approach that aims to fulfil several objectives. One is to reduce energy consumption by using efficient lamps and advanced control systems; the second one is to make the network viable and useful for many purposes by integrating ICT devices; the third one is to provide a new identity to the older part of the city by using new technologies and design concepts; while the last one is to ensure street and pedestrian safety according to codes and standards. Design/methodology/approach The plan of the city of Bagheria and the stock of luminaires of the city are analys…