Charge confinement and Klein tunneling from doping graphene

In the present work, we investigate how structural defects in graphene can change its transport properties. In particular, we show that breaking of the sublattice symmetry in a graphene monolayer overcomes the Klein effect, leading to confined states of massless Dirac fermions. Experimentally, this corresponds to chemical bonding of foreign atoms to carbon atoms, which attach themselves to preferential positions on one of the two sublattices. In addition, we consider the scattering off a tensor barrier, which describes the rotation of the honeycomb cells of a given region around an axis perpendicular to the graphene layer. We demonstrate that in this case the intervalley mixing between the Dirac points emerges, and that Klein tunneling occurs.Comment: 11 pages, 5 figure

A Group Recommendation Model Using Diversification Techniques

In daily life groups are formed naturally, such as watching a movie with friends, or going out for dinner. In all these scenarios, using Recommendation Systems can be helpful by suggesting pieces of information (e.g. movies or restaurants) that satisfies all rather than a single member in the group. To do so, it is crucial to aggregate individual preferences of the group members aiming at satisfying all. Although there are consensus techniques to create the group profile, the recommendations still may be repetitive and overspecialized. This drawback sets precedent for adopting diversification techniques to group recommendations. In this paper, we propose a group recommendation model using diversification techniques that exploits different aggregation techniques over group preferences matrix. The experiments evaluate accuracy and diversity goals for the group recommendations. Results from the experiments point out that our approach achieved 1.8% of diversity increase and 3.8% of precision improvement over compared methods

Thermo-hydro-mechanical analysis of CO2 injection into deep aquifers

One of the biggest challenges for humanity is global warming and consequently, climate changes. Even though there has been increasing public awareness and investments from numerous countries concerning renewable energies, fossil fuels are and will continue to be in the near future, the main source of energy. Carbon capture and storage (CCS) is believed to be a serious measure to mitigate CO2 concentration. CCS briefly consists of capturing CO2 from the atmosphere or stationary emission sources and transporting and storing it via mineral carbonation, in oceans or geological media. The latter is referred to as carbon capture and geological storage (CCGS) and is considered to be the most promising of all solutions. Generally it consists of a storage (e.g. depleted oil reservoirs and deep saline aquifers) and sealing (commonly termed caprock in the oil industry) formations. The present study concerns the injection of CO2 into deep aquifers and regardless injection conditions, temperature gradients between carbon dioxide and the storage formation are likely to occur. Should the CO2 temperature be lower than the storage formation, a contractive behaviour of the reservoir and caprock is expected. The latter can result in the opening of new paths or re-opening of fractures, favouring leakage and compromising the CCGS project. During CO2 injection, coupled thermo-hydro-mechanical phenomena occur, which due to their complexity, hamper the assessment of each relative influence. For this purpose, several analyses were carried out in order to evaluate their influences but focusing on the thermal contractive behaviour. It was finally concluded that depending on mechanical and thermal properties of the pair aquifer-seal, the sealing caprock can undergo significant decreases in effective stress

Increasing returns to scale and international diffusion of technology: an empirical study for Brazil (1976-2000)

This article aims at exploring the empirical evidence regarding the effects of increasing returns to scale and international technological diffusion on the Brazilian manufacturing industry. Our departure point is a Kaldorian-type theoretical model that provides not only the positive effects of scale but also of diffusion on industrial performance. We use Vector Auto Regressive (VAR) for testing the model. VAR will estimate the coefficients related to industrial output, labor productivity, exports and the technological gap between the United States and Brazil. This technique also provides simulations for the short-term and long-term trajectories under exogenous shocks. The observations are on a three-month period basis and the sampling period runs from the second half of 1976 to the second half of 2000. The conclusion highlights both evidences of increasing returns on the Brazilian industry that faces, however, some structural constraints. Besides, the model also reveals Brazil's difficulties to catch uptechnological gap; increasing returns to scale; economic growth; Brazil

Energy dissipation devices for structures under blast

Terrorism pose a serious threat nowadays and many countries have the concern of protecting his people and most important buildings. This concern is an opportunity to strengthen the research of the behaviour of buildings under blast in order to reduce the magnitude of the effects of these catastrophic events. The present thesis aims to create a functional system to improve the security of critical buildings, either new or adapting old buildings to receive this new system. This system also tries to be cost efficient, so this can be used in most buildings. This thesis was centred in one system with two variations. The systems had the same lower reinforced concrete slab with 2,60 x 2,00 m and 0,12 m of thickness. The first system consisted in using 32 steel tubes of 76,1 mm outer diameter arranged uniformly and eight concrete panels, each one with 1,00 x 0,65 m and 0,07 m of thickness, on top of these tubes. The second system was the same concrete panels on top of 32 steel tubes with 48,3 mm outer diameter. To test these systems four blast trials were prepared: the first is the reference specimen and the other two using the two mentioned variations of the system. These slabs were tested simply supported in two parallel edges, with a span of 2,30 m. In all tests 6,00 Kg of the explosive Eurodyn 2000 were used at a distance of 1,85 m from the top of the slab to the centre of the explosive. The results show an improvement in the residual deformation and on the opening of the visible cracks of the base reinforced concrete slab

Dark/Visible Parallel Universes and Big Bang Nucleosynthesis

We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated.Comment: Invited talk at the Workshops "CompStar: the physics and astrophysics of compact stars", Tahiti, June 4-8, 2012, "New Directions in Nuclear Astrophysics", Castiglion Fiorentino, Italy, June 18-22, 2012, and "Carpathian Summer School of Physics", Sinaia, Romania, June 24 - July 7, 2012. To be published in AIP Proceeding

Towards a science of architecture?

O artigo tem origem nos resultados do trabalho de Iniciação Científica da segunda autora.O trabalho reflete sobre pesquisa e sobre o perfil de pesquisadores no Brasil, na área de Arquitetura. Utiliza informações publicamente disponíveis nas páginas da Internet do CNPq e da CAPES. Discute taxonomias correntes sobre a divisão da arquitetura em subáreas e sugere uma taxonomia própria a partir de um conceito também original de arquitetura. Comenta-se a distribuição da pesquisa e como ela é veiculada em livros, capítulos de livros, periódicos e anais de eventos. São propostos índices mediante os quais a produção intelectual de pesquisadores pode ser avaliada, e é analisada a distribuição da produção entre pesquisadores com bolsa ativa no CNPq. Comentase um banco de dados que está sendo montado sobre pesquisadores no Brasil e sugerem-se os aspectos que devem ser considerados para sua avaliação. Argumenta-se que este pode ser um ponto de partida para uma discussão mais ampla da produção de conhecimento em Arquitetura no país. ______________________________________________________________________________________ ABSTRACTThis paper ponders over research and researchers’ profile in the field of architecture. Its source is information publicly available in CNPq and CAPES web pages. It discusses current taxonomies on architecture sub-areas and suggests a taxonomy of its own that derives from a concept of architecture which is also original. The distribution of research works is commented, as well as the way it is edited and spread in books, book chapters, periodicals and conference proceedings. Indices are suggested, through which the intellectual production of researchers is evaluated, and the distribution of the production of researchers with a research grant from CNPq is commented. A data bank that is being developed about researchers in Brazil is discussed and also items that should be taken into consideration on their evaluation. It is suggested that this may be a starting point for a broader discussion of the production of knowledge in architecture in the country. ______________________________________________________________________________________ RESUMENEl texto discute el perfil de la investigación y de los investigadores en el área de arquitectura. Utiliza información pública disponible en las páginas de internet de CNPq y CAPES. Discute taxonomías comunes sobre sub-áreas de arquitectura y sugiere una taxonomía propia, a partir de un concepto de arquitectura que es también original. La distribución de trabajos de investigación es comentada, así como las maneras por las cuales ella es publicada en libros, capítulos de libros, periódicos especializados e anales de conferencias académicas. Índices son sugeridos, por los cuales la producción intelectual de los investigadores puede ser evaluada, y la producción entre investigadores con becas de CNPq es comentada. Un banco de datos que está siendo producido sobre investigadores en Brasil es discutido y aspectos por los cuales ellos deben ser evaluados es comentado. Es sugerido que esto pude ser un inicio para una discusión más amplia sobre la producción de conocimiento sobre arquitectura en el país