16 research outputs found
Excitons at the B K edge of boron nitride nanotubes probed by x-ray absorption spectroscopy
We have performed a near-edge x-ray absorption fine-structure (NEXAFS) investigation of multi-walled boron nitride nanotubes (BNNTs). We show that the one-dimensionality of BNNTs is clearly evident in the B K edge spectrum, while the N K edge spectrum is similar to that of layered hexagonal BN (h-BN). We observe a sharp feature at the Ã* onset of the B K edge, which we ascribe to a core exciton state. We also report a comparison with spectra taken after an ammonia plasma treatment, showing that the B K edge becomes indistinguishable from that of h-BN, due to the breaking of the tubular order and the formation of small h-BN clusters
Dynamics of charged gibbsite platelets in the isotropic phase
We report on depolarized and non-depolarized dynamic light scattering, static
light scattering, and static viscosity measurements on interacting charged
gibbsite platelets suspended in dimethyl sulfoxide (DMSO). The average
collective and (long-time) translational self-diffusion coefficients, and the
rotational diffusion coefficient, have been measured as functions of the
platelet volume fraction \phi, up to the isotropic-liquid crystal (I/LC)
transition. The non-depolarized intensity autocorrelation function, measured at
low scattering wavenumbers, consists of a fast and a slowly decaying mode which
we interpret as the orientationally averaged collective and translational
self-diffusion coefficients, respectively. Both the rotational and the
long-time self-diffusion coefficients decrease very strongly, by more than two
orders of magnitude, in going from the very dilute limit to the I/LC transition
concentration. A similarly strong decrease, with increasing \phi, is observed
for the inverse zero-strain limiting static shear viscosity. With increasing
\phi, increasingly strong shear-thinning is observed, accompanied by a
shrinking of the low shear-rate Newtonian plateau. The measured diffusion
coefficients are interpreted theoretically in terms of a simple model of
effective charged spheres interacting by a screened Coulomb potential, with
hydrodynamic interactions included. The disk-like particle shape, and the
measured particle radius and thickness polydispersities, enter into the model
calculations via the scattering amplitudes. The interaction-induced enhancement
of the collective diffusion coefficient by more than a factor of 20 at larger
volume fractions is well captured in the effective sphere model, whereas the
strong declines both of the experimental translational and rotational
self-diffusion coefficients are underestimated
Remanufacturing approaches contributing to sustainable engineering Abordagens de remanufatura - uma contribuição para engenharia sustentável
Increasing use of resources by an increasing population with unequally distributed wealth make sustainability an urgent topic to pay attention to. A reference model for sustainability in engineering is presented referring to education and research, management, technology, processes and products as the relevant issues for a global change to sustainability. The European environmental laws for sustainable development are an attempt to cope with this challenge by legislative means. The provocative reality of practical implementation in dealing with electric and electronic products after their usage phases in Europe is illustrated. Laboratory developments in disassembly and testing demonstrate the feasibility of remanufacturing. In addition, approaches to increase the efficiency of remanufacturing by improving the product design are introduced.O crescente uso de recursos gerado pelo contínuo crescimento populacional inserido em um cenário de distribuição desigual de riqueza faz do termo sustentabilidade um tópico urgente para discussão. Neste artigo, apresenta-se um modelo de referência para sustentabilidade em engenharia que aborda questões relevantes para uma mudança global no caminho para a sustentabilidade, priorizando os seguintes elementos: educação e pesquisa; gestão, tecnologia, processos e produtos. As leis ambientais da União Européia esforçam-se para tratar com responsabilidade esse desafio de desenvolvimento sustentável. A realidade de implementações práticas em consideração a produtos eletro-eletrônicos depois de sua fase de uso é ilustrada no artigo. Desenvolvimentos em laboratório de desmontagens e testes demonstram a viabilidade da remanufatura. Além disso, abordagens para aumentar a eficiência do processo de remanufatura a partir de melhorias no processo de desenvolvimento do produto são também sugeridas
Fabrication of magnetic force microscopy probes via localized electrochemical deposition of cobalt
Magnetic force microscopy probes were obtained via the solution phase electrochemical deposition of cobalt nanostructures at the probe apexes. Single tips were fabricated in an atomic force microscope fluid cell. Multiple tips were produced in a single batch with an alternating potential in an electrochemical cell. The probes achieve 50 nm spatial resolution
Fabrication of magnetic force microscopy probes via localized electrochemical deposition of cobalt
Magnetic force microscopy probes were obtained via the solution phase electrochemical deposition of cobalt nanostructures at the probe apexes. Single tips were fabricated in an atomic force microscope fluid cell. Multiple tips were produced in a single batch with an alternating potential in an electrochemical cell. The probes achieve 50 nm spatial resolution
Spatial dependence of observed Raman frequencies and disorder in graphene monolayers
A micro-Raman investigation was carried out on several flakes of monolayer (1 L) graphene obtained by the micro-mechanical exfoliation technique and, then, put on a c-Si wafer coated by a SiO2 thin film. Some of the 1 L zones show a remarkable dispersion of the 2D-overtone wavenumber as a function of the position within the graphene sheet, and, in some case, a significant broadening of the E2g phonon (G band) is associated to
this wavenumber shift of 2D-band. Such effects were studied, in particular, for a 1 L zone characterized by a rather strong lattice disorder, as revealed by the strong D/G band intensity ratio, and for other zones quite ordered, showing a vanishing intensity of the D band. Moreover, by moving along different directions within
1 L graphene sheets, different trends for 2D wavenumber and E2g phonon bandwidth vs. position were observed. All these reported behaviours are explained in terms of different distributions of intrinsic uniaxial strain occurring within the 1 L graphene sheets
Recommending Movies Based on Mise-en-Scene Design
In this paper, we present an ongoing work that will ultimately result in a movie recommender system based on the Mise-en-Scène characteristics of the movies. We believe that the preferences of users on movies can be well described in terms of the mise-en-scène, i.e., the design aspects of movie making influencing aesthetic and style. Examples of mise-en-scène characteristics are lighting, colors, background, and movements. Our recommender system opens new opportunities in the design of new user interfaces able to offer a personalized way to search for interesting movies through the analysis of film styles rather than using the traditional classifications of movies based on explicit attributes such as genre and cast