Expansion algorithm for the density matrix

A purification algorithm for expanding the single-particle density matrix in terms of the Hamiltonian operator is proposed. The scheme works with a predefined occupation and requires less than half the number of matrix-matrix multiplications compared to existing methods at low (90%) occupancy. The expansion can be used with a fixed chemical potential in which case it is an asymmetric generalization of and a substantial improvement over grand canonical McWeeny purification. It is shown that the computational complexity, measured as number of matrix multiplications, essentially is independent of system size even for metallic materials with a vanishing band gap.Comment: 5 pages, 4 figures, to appear in Phys. Rev.

GESTÃO DE DADOS DE PRODUTIVIDADE PARA TOMADA DE DECISÃO EM REBANHO LEITEIRO

O gerenciamento adequado em determinada propriedade é de extrema importância para o produtor que visa ter um produto de qualidade e com uma boa produtividade, fazendo com que ocorra a diminuição de gastos na propriedade e de vacas com rendimento ruim. O projeto foi realizado no Instituto Federal Catarinense Campus Araquari, na unidade de ensino e aprendizagem (UEA) bovino cultura. A meta foi coletar dados e planilhar Posteriormente foi realizar comparações com outros períodos sobre a produtividade do setor, fazendo com que o manejo seja mais eficaz e produtivo. Com tudo observamos que seria necessário direcionar alguns ani maispara descarte, diminuindo gastos dentro da propriedade. O projeto nos mostrou também algumas orientações incorretas feitas dentro do instituto, que proporcionou dados zootécnicos favoráveis para a tomada de decisões

Airbag for the closing of pipelines on explosions and leakages

This paper is a result of international effort aimed at the construction of a device for quick closing of pipelines in the case of explosion propagation and/or chemical leakage. Such a problem exists in industries where flammable substances are transported by pipelines. The basic solution principle was the idea to use airbags similar to those utilized in cars. Two pipeline applications were taken into consideration: a low-pressure module able to suppress explosion propagation and a high-pressure module to stop leakages from, e.g. natural gas pipeline capable to be used for duct diameters up to 0.6 m, pressures up to 5 MPa and reaction times of 50 ms. It was necessary to construct a new airbag, capable of withstanding up to 10 bar pressure. The choice of material was critical to ensure sufficient strength and chemical resistance while retaining impermeability. CFD modeling of the bag deployment into a pipe flow and analysis of the bag shapes was also completed. Two gas generators were constructed and tested with novel propellant materials. Different airbag models were tested to evaluate their effectiveness. Risk analysis approach was applied to evaluate the safety and economic benefits of the new technology in different fields of application

Centroid Localization of Uncooperative Nodes in Wireless Networks Using a Relative Span Weighting Method

Increasingly ubiquitous wireless technologies require novel localization techniques to pinpoint the position of an uncooperative node, whether the target is a malicious device engaging in a security exploit or a low-battery handset in the middle of a critical emergency. Such scenarios necessitate that a radio signal source be localized by other network nodes efficiently, using minimal information. We propose two new algorithms for estimating the position of an uncooperative transmitter, based on the received signal strength (RSS) of a single target message at a set of receivers whose coordinates are known. As an extension to the concept of centroid localization, our mechanisms weigh each receiver's coordinates based on the message's relative RSS at that receiver, with respect to the span of RSS values over all receivers. The weights may decrease from the highest RSS receiver either linearly or exponentially. Our simulation results demonstrate that for all but the most sparsely populated wireless networks, our exponentially weighted mechanism localizes a target node within the regulations stipulated for emergency services location accuracy

The Role of Temporary Agency Work in Different Industrial Relations Systems - a Comparison between Germany and the USA

Although temporary agency work has been growing over the last decade, its use differs widely in different industrial relations systems. Drawing on theoretical and empirical insights, propositions are developed on why companies deploy temporary agency work. These propositions are then contrasted with case-study evidence collected in Germany and the USA to analyse the deployment of agency work in two different industrial relations systems and the role that agency work plays in these diverse settings. The main conclusions of the research are that differences in the deployment of temporary agency workers exist with regard to legal regulation and employers' strategies of labour use while similarities exist regarding the supply of agency labour. Copyright Blackwell Publishing Ltd/London School of Economics 2007.