Percepções sobre a educação a distância : um estudo preliminar à implantação da EaD pela Escola de Contas Públicas do TCDF

Trabalho de conclusão de curso (especialização)—Universidade de Brasília, Faculdade de Economia, Administração e Contabilidade, Departamento de Administração, Núcleo de Estudos e Pesquisas em Inovação e Estratégia, Tribunal de Contas do Distrito Federal, 2017.O presente trabalho objetiva identificar as percepções dos servidores do Tribunal de Contas do Distrito Federal sobre o Ensino a Distância, para isso se deve: identificar o nível de domínio dos servidores do TCDF no uso de ferramentas relacionadas à tecnologia da informação; Identificar barreiras pessoais e institucionais que possam contribuir para a evasão dos servidores do TCDF dos cursos a distância; Fornecer à Escola de Contas do TCDF subsídio que possa auxiliá-la no processo de implantação do Ensino a Distância

Atomic collapse, Lorentz boosts, Klein scattering, and other quantum-relativistic phenomena in graphene

Electrons in graphene, behaving as massless relativistic Dirac particles, provide a new perspective on the relation between condensed matter and high-energy physics. We discuss atomic collapse, a novel state of superheavy atoms stripped of their discrete energy levels, which are transformed into resonant states. Charge impurities in graphene provide a convenient condensed matter system in which this effect can be explored. Relativistic dynamics also manifests itself in another system, graphene p-n junctions. We show how the transport problem in the presence of magnetic field can be solved with the help of a Lorentz transformation, and use it to investigate magnetotransport in p-n junctions. Finally, we review recent proposal to use Fabry-Perot resonances in p-n-p structures as a vehicle to investigate Klein scattering, another hallmark phenomenon of relativistic dynamics.Comment: minireview, 9 pg

Atomically thin boron nitride: a tunnelling barrier for graphene devices

We investigate the electronic properties of heterostructures based on ultrathin hexagonal boron nitride (h-BN) crystalline layers sandwiched between two layers of graphene as well as other conducting materials (graphite, gold). The tunnel conductance depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Exponential behaviour of I-V characteristics for graphene/BN/graphene and graphite/BN/graphite devices is determined mainly by the changes in the density of states with bias voltage in the electrodes. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field; it offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel.Comment: 7 pages, 5 figure

SRGeJ045359.9+622444: A 55-min Period Eclipsing AM CVn Discovered from a Joint SRG/eROSITA + ZTF Search

AM CVn systems are ultra-compact binaries where a white dwarf accretes from a helium-rich degenerate or semi-degenerate donor. Some AM CVn systems will be among the loudest sources of gravitational waves for the upcoming Laser Interferometer Space Antenna (LISA), yet the formation channel of AM CVns remains uncertain. We report the study and characterisation of a new eclipsing AM CVn, SRGeJ045359.9+622444 (hereafter SRGeJ0453), discovered from a joint SRG/eROSITA and ZTF program to identify cataclysmic variables (CVs). We obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine the orbital period to be $P_\textrm{orb} = 55.0802 \pm 0.0003$ min. We constrain the binary parameters by modeling the high-speed photometry and radial velocity curves and find $M_\textrm{donor} = 0.044 \pm0.024 M_{\odot}$ and $R_\textrm{donor}=0.078 \pm 0.012 R_{\odot}$. The X-ray spectrum is approximated by a power-law model with an unusually flat photon index of $\Gamma\sim 1$ previously seen in magnetic CVs with SRG/eROSITA, but verifying the magnetic nature of SRGeJ0453 requires further investigation. Optical spectroscopy suggests that the donor star of SRGeJ0453 could have initially been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn system published to date, and its lack of optical outbursts have made it elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and optical surveys highlights the potential for discovering similar systems in the near future.Comment: Submitted to Ap

Perestroika

ix, 199 hlm.; 16.5 x 25 c

PERESTROIKA, PEMIKIRAN BARU UNTUK KAMI DAN DUNIA

xii; 199 hlm;15,5 x 24 c

Perestroika : Pemikiran Baru untuk Negara kami dan Dunia

Jakartavii, 199 hal.; 24 c