A high-voltage lithium-ion battery prepared using a Sn-decorated reduced graphene oxide anode and a LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> cathode

This paper describes the preparation and characterization of a high-voltage lithium-ion battery based on Sn-decorated reduced graphene oxide and LiNi_0.5Mn_1.5O₄ as the anode and cathode active materials, respectively. The Sn-decorated reduced graphene oxide is prepared using a microwave-assisted hydrothermal synthesis method followed by reduction at high temperature of a mixture of (C₆H₅)₂SnCl₂ and graphene oxide. The so-obtained anode material is characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and electron diffraction spectroscopy. The LiNi_0.5Mn_1.5O₄ is a commercially available product. The two materials are used to prepare composite electrodes, and their electrochemical properties are investigated by galvanostatic charge/discharge cycles at various current densities in lithium cells. The electrodes are then used to assemble a high-voltage lithium-ion cell, and the cell is tested to evaluate its performance as a function of discharge rate and cycle number.     

Double Vivaldi antenna for wireless optical networks on chip

In this paper we present a double plasmonic Vivaldi antenna for on-chip optical wireless communication. The proposed antenna is a two-element broadside array fed by a silicon waveguide. The designs of the power splitter and of the hybrid Si-plasmonic coupler used for antenna excitation are described in detail. The array radiation characteristics are optimized through Finite Difference Time Domain simulations and the performance of a point-to-point link is evaluated. The proposed double Vivaldi array increases the gain of 3 dB with respect to a single antenna, improving the received power on a link of 6 dB when the double antenna is used for both transmitting and receiving sections.     

Temperature dependence of the time-resolved emissions of CsI:Tl

Abstract

Time-resolved emissions of Csl:T1 are investigated. The system is laser-excited in the A-band at 308 nm and the emissions are observed in the range 370–650 nm, from 30 K to 300 K. Their analysis by means of a deconvolution permits the valuation of decay-times down to 1 ns. At every temperature many bands are observed and some of them show slow and fast components. The decay-times of the fast components are in the range 1–10 ns while the slow ones are even longer than 1 μs. In many cases intermediate decay-times of the order of 100 ns exist. The competition among the bands interests the application of this system as active material for tunable solid-state laser.     

Quaternionic differential forms and symplectic Pontrjagin classes

Sunto Si considerano fibrati vettoriali quaternionali dotati di connessione quaternionale e si determinano forme differenziali rappresentanti delle classi simplettiche di Pontrjagin.

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Lavoro eseguito nell'ambito del gruppo G.N.S.A.G.A. del C.N.R.; esposto in una comunicazione a Oberwolfach, 7–13 Giugno 1981.     

When does coarsening occur in the dynamics of one-dimensional fronts?

Dynamics of a one-dimensional growing front with an unstable straight profile are analyzed. We argue that a coarsening process occurs if and only if the period lambda of the steady-state solution is an increasing function of its amplitude A. This statement is rigorously proved for two important classes of conserved and nonconserved models by investigating the phase diffusion equation of the steady pattern. We further provide clear numerical evidence for the growth equation of a stepped crystal surface.     

Phase transitions driven by state-dependent poisson noise

Nonlinear systems driven by state-dependent Poisson noise are introduced to model the persistence of climatic anomalies in land-atmosphere interaction caused by the soil-moisture dependence of the frequency of rainfall events. It is found that these systems may give rise to bimodal probability distributions, while the state variable randomly persists around the preferential states because of transient dynamics that are opposite to the long-term behavior. Mean-field analysis and numerical simulations of the spatially distributed systems reveal a symmetry-breaking bifurcation for sufficiently strong spatial diffusive couplings and intermediate noise intensities. In such conditions, the initial development of spatial patterns is followed by a stable configuration, selected on the bases of the initial conditions in correspondence of the remnants of the modes of the uncoupled system.