Optical realization of bioinspired spiking neurons in the electron trapping material thin film

A thin film of electron-trapping material (ETM), when combined with suitable optical bistability, is considered as a medium for optical implementation of bioinspired neural nets. The optical mechanism of ETM under blue light and near-infrared exposure has the inherent ability at the material level to mimic the crucial components of the stylized Hodgkin-Huxley model of biological neurons. Combining this unique property with the high-resolution capability of ETM, a dense network of bioinspired neurons can be realized in a thin film of this infrared stimulable storage phosphor. When combined with suitable optical bistability and optical interconnectivity, it has the potential of producing an artificial nonlinear excitable medium analog to cortical tissue.     

Raman spectroscopy and in situ Raman spectroelectrochemistry of bilayer ¹²C/¹³C graphene

Bilayer graphene was prepared by the subsequent deposition of a (13)C single-layer graphene and a (12)C single-layer graphene on top of a SiO(2)/Si substrate. The bilayer graphene thus prepared was studied using Raman spectroscopy and in situ Raman spectroelectrochemistry. The Raman frequencies of the (13)C graphene bands are significantly shifted with respect to those of (12)C graphene, which allows us to investigate the single layer components of bilayer graphene individually. It is shown that the bottom layer of the bilayer graphene is significantly doped from the substrate, while the top layer does not exhibit a signature of the doping from the environment. The electrochemical doping has the same effect on the charge carrier concentration at the top and the bottom layer despite the top layer being the only layer in contact with the electrolyte. This is here demonstrated by essentially the same frequency shifts of the G and G' bands as a function of the electrode potential for both the top and bottom layers. Nevertheless, analysis of the intensity of the Raman modes showed an anomalous bleaching of the Raman intensity of the G mode with increasing electrode potential, which was not observed previously in one-layer graphene.     

Competition between the spring force constant and the phonon energy renormalization in electrochemically doped semiconducting single-walled carbon nanotubes

A detailed analysis of the in situ Raman spectroelectrochemical behavior of individual semiconducting single-walled carbon nanotubes (SWCNTs) is presented. Special attention has been paid to the development of the tangential (TG) mode frequency, which shifts when the externally applied potential Ve is shifted away from Ve=0. The magnitude and direction (upshift or downshift) of the tangential mode band has been found to be dependent on the diameter of the semiconducting tubes. For negative charging, the small-diameter tubes exhibit a downshift while the large-diameter tubes exhibit an upshift. This behavior is explained by a competition between two effects which cause opposite shifts in the TG mode frequency during negative charging: a phonon renormalization effect and a C-C bond weakening during the charging process. Positive charging always causes an upshift of the TG mode frequency. However, the magnitude of the upshift is dependent on the tube diameter.     

A domain decomposition method for discontinuous Galerkin discretizations of Helmholtz problems with plane waves and Lagrange multipliers

A nonoverlapping domain decomposition (DD) method is proposed for the iterative solution of systems of equations arising from the discretization of Helmholtz problems by the discontinuous enrichment method. This discretization method is a discontinuous Galerkin finite element method with plane wave basis functions for approximating locally the solution and dual Lagrange multipliers for weakly enforcing its continuity over the element interfaces. The primal subdomain degrees of freedom are eliminated by local static condensations to obtain an algebraic system of equations formulated in terms of the interface Lagrange multipliers only. As in the FETI‐H and FETI‐DPH DD methods for continuous Galerkin discretizations, this system of Lagrange multipliers is iteratively solved by a Krylov method equipped with both a local preconditioner based on subdomain data, and a global one using a coarse space. Numerical experiments performed for two‐ and three‐dimensional acoustic scattering problems suggest that the proposed DD‐based iterative solver is scalable with respect to both the size of the global problem and the number of subdomains. Copyright © 2009 John Wiley & Sons, Ltd.     

CADS-ML/DL: efficient cloud-based multi-attack detection system

International Journal of Information Security - With the increasing adoption of cloud computing, securing cloud-based systems and applications has become a critical concern for almost every...