The Stability of Polar Oxide Surfaces

The structures of the polar surfaces of ZnO are studied using ab initio calculations and surface x-ray diffraction. The experimental and theoretical relaxations are in good agreement. The polar surfaces are shown to be very stable; the cleavage energy for the (0001)-Zn and (0001̅ )-O surfaces is 4.0J/m2 comparable to 2.32J/m2 for the most stable nonpolar (1010) surface. The surfaces are stabilized by an electronic mechanism involving the transfer of 0.17 electrons between them. This leads to 2D metallic surface states, which has implications for the use of the material in gas sensing and catalytic applications

Causalidade e transmissão de preços entre os níveis de mercados na cadeia do feijão em São Paulo.

O presente trabalho objetivou avaliar a causalidade e transmissão de preço entre os níveis de mercado da cadeia do feijão em São Paulo.CONAFE

Anti-symmetric rank-2 Matter Field on Superspace for N_{T}=2

In this work, we discuss the interaction between anti-symmetric rank-two tensor matter and topological Yang-Mills fields. The matter field considered here is the rank-2 Avdeev-Chizhov tensor matter field in a suitably extended $N_{T}=2$ SUSY. We start off from the $N_{T}=2$, D=4 superspace formulation and we go over to Riemannian manifolds. The matter field is coupled to the topological Yang-Mills field. We show that both actions are obtained as $Q-$exact forms, which allows us to write the energy-momentum tensor as $Q-$exact observables.Comment: 10 pages, no figure, LaTe

Benefícios fiscais na cadeia da soja em Goiás: apropriação pela estrutura de intermediação.

O objetivo deste artigo foi de perceber como, na cadeia da soja, as políticas fiscais garantem competitividade a poucos em detrimento dos demais, incorrendo a uma violação dos princípios constitucionais do direito tributário, privando a determinados elos as benesses dos benefícios fiscais. Para tanto, foram levantados os atores do SAG da soja e posteriormente enquadrados nos códigos CNAEs, para serem percebidos no banco de dados da SEFAZ-GO. Com o objetivo de quantificar estas políticas, as mesmas foram definidas, dentre todas as políticas de renúncia fiscal neste Estado, como beneficiadoras de apenas um ramo industrial da SAG da soja em Goiás

Análise da logística de transporte na comercialização da produção de soja na região Centro-Oeste com foco no modal rodoviário.

A soja é uma das mais importantes commodities nacionais, sendo um grão rico em proteínas, cultivado como alimento tanto para humanos quanto para animais. No Brasil, a população não possui hábito de consumir o grão in natura, o maior consumo é do óleo de soja, o farelo é utilizado na formulação de ração para aves e suínos. A produção brasileira de soja possui uma característica de migração para as regiões de fronteira agrícola, as regiões Centro-Oeste e Norte estão afastadas dos polos consumidores e dos corredores de exportação, na maioria dos casos o modal rodoviário é utilizado, mas dispõe de rodovias em estado de conservação de uso muitas vezes inadequado, o que onera ainda mais os custos de transporte. Assim, o objetivo do presente trabalho foi descrever o processo logístico de transporte da soja em grão da região Centro-Oeste, com foco no estado de uso das principais rodovias utilizadas para o transporte de soja, fazendo uma análise dos pontos críticos que afetam o complexo

Probabilistic Power Flow Simulation allowing Temporary Current Overloading

This paper presents a probabilistic power flow model subject to connection temperature constraints. Renewable power generation is included and modelled stochastically in order to reflect its intermittent nature. In contrast to conventional models that enforce connection current constraints, short-term current overloading is allowed. Temperature constraints are weaker than current constraints, and hence the proposed model quantifies the overload risk more realistically. Using such a constraint is justified the more by the intermittent nature of the renewable power source. Allowing temporary current overloading necessitates the incorporation of a time domain in our model. This substantially influences the choice of model for the renewable power source, as we explain. Wind power is modelled by use of an ARMA model, and appropriate accelerations of the power flow solution technique are chosen. Several IEEE test case examples illustrate the more realistic risk analysis. An example shows that a current constraint model may overestimate these risks, which may lead to unnecessary over-investments by grid operators in grid connections

Using the economic surplus method to assess economic impacts of new technologies: case studies of Embrapa.

Abstract - Assessment of economic impacts of new technologies delivers helpful information to justify investment efforts in research and development to generate new technologies. In Brazilian agricultural research and development, it?s a convention to assess economic impacts of technologies generated and adapted by EMBRAPA. As soon as new technologies are adopted, expost assessment is conducted to evaluate net benefits of its adoption. In agricultural research, the economic surplus method represents one of the suitable frameworks to measure the aggregated social benefits of a research project. With this method it is possible to estimate the return of investments by calculating a variation of consumer and producer surplus through a technological change originated by research results. Therefore, in a first step the gain of adoption i.e., increases in productivity, quality improvements, cost reduction etc. is estimated. In a second step, costs involved in generation and adaptation of the technology are enumerated. The difference between the gains and the costs of generation and transfer represents the net benefit of the technology, explained by the net present value, the internal rate of return and the benefit-costratio. The so far obtained results serve as additional information for each technology to improve its adoption by beneficiaries and to enable access to the new financing sources. Some examples of such technologies are (a) the finishing of lambs in confinement in the Brazilian semi-arid Northeast during the dry season, when feeding resources are scarce and the lamb meat prices are high; (b) strategic vermifugation of goats herds and sheep flocks in the Brazilian semi-arid areas; (c) standardized cuts for goat and sheep carcass and (d) enrichment of the native pastures in Brazilian Northeast with Cynodon dactylon for sheep production. The assessment of the economic impacts of these technologies estimated positive net present values for all four considered technologies, internal rates of return of 26.2% (a), 13.8% (b), 52.8% (c) and 31.0% (d) and the benefit-cost-ratios of 2.92 (a), 1.19 (b), 11.64 (c) and 3.37 (d)