Dynamical Casimir effect with Robin boundary conditions in a three dimensional open cavity

We consider a massless scalar field in 1+1 dimensions inside a cavity composed by a fixed plate, which imposes on the field a Robin BC, and an oscillating one, which imposes on the field a Dirichlet BC. Assuming that the plate moves for a finite time interval, and considering parametric resonance, we compute the total number of created particles inside the cavity. We generalize our results to the case of two parallel plates in 3+1 dimensions.Comment: This work was presented in the Conference QFEXT09, held at the University of Oklahoma, Norman, OK, USA, September 21-25, 2009, and will appear in the proceedings of this conference. It contains 4 figure

O programa nacional de fortalecimento da agricultura familiar no Brasil: uma análise sobre a distribuição regional e setorial dos recursos.

No Brasil, as políticas públicas para o espaço rural sempre tenderam a priorizar a agricultura patronal, em detrimento dos agricultores familiares. Todavia, os estudos realizados pelos órgãos FAO - INCRA deram subsídio para a criação do Programa Nacional de Fortalecimento da Agricultura Familiar (PRONAF), resultando em um novo direcionamento dos investimentos públicos, os quais passaram a contemplar o segmento dos agricultores familiares. Entende-se o PRONAF como uma política não-compensatória, que, apesar de seus problemas, tem contribuído de fato para mudanças e melhorias no espaço agrário brasileiro. Desde sua criação no final da década de 1990, o PRONAF passou por várias mudanças em sua estrutura administrativa e operacional, a fim de alcançar seus objetivos e adequar-se face a complexa realidade social agrária brasileira. Sendo assim, o presente estudo visa discutir as ações do Estado por meio desse Programa, a partir de suas linhas de atuação, bem como analisar a distribuição de suas concessões de crédito regional e setorialmente. Assim, os procedimentos metodológicos utilizados para a realização deste trabalho compreendem pesquisa bibliográfica e documental, além de pesquisa em fontes secundárias, no intuito de obter dados e informações relevantes para a análise das relações sociais estabelecidas em meio a esse processo de concretização e espacialização desse Programa. Dentre as implicações do PRONAF pode-se notar em âmbito nacional, uma diminuição da disparidade regional brasileira, bem como a preocupação que o Programa tem demonstrado com os aspectos socioculturais locais e regionais, como forma de garantir que seus investimentos perpassem a dimensão econômica, mas valorize outras dimensões, a exemplo dos elementos culturais

Maravilha: a cultivar de arroz de sequeiro para os solos de mata em Rondonia.

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Further considerations of magnetic deinking for wastepaper recycling mills

Journal ArticleMagnetic de-inking has been shown to be an efficient process for the removal of certain toner particles from mixed office waste (MOW) furnishes. It is possible to achieve a dirt removal of 96% with the WHIMS (wet high intensity magnetic separator) if all toner particles present in the furnish are at least paramagnetic. However, the recycled MOW has a variety of toner particles thai vary from non-magnetic to ferromagnetic and , under these circumstance, it may be necessary to combine flotation with WHIMS in order to achieve a satisfactory level of dirt removal. On the other hand, flotation may not be necessary if agglomeration of non-magnetic and magnetic toner particles can be accomplished. In this regard, conditions for toner agglomeration have been examined and the toner agglomeration characterized. Specifically, the magnetic susceptibility of such aggregates has been measured in order to facilitate efficient magnetic de-inking for wastepaper recycle mills

Agglomeration and magnetic deinking for office paper

Journal ArticleMagnet deinking of office paper (OP) is a promising technology for the production of high quality secondary fiber. The technique is possible because a significant portion of the toner in OP furnish has a magnetic character. Toner magnetic susceptibility can vary from weakly paramagnetic to ferromagnetic depending on the iron oxide content of the toner partides.The amount of iron oxide in toners varies. It can contain as much as 65% by weight depending on the type of image development process used by electrophotography machines

Free movement in education

Chapters 9, 10, 11, 12, 13 and 14 focus on examples of migration taking place within formal education, with emphasis on student mobility at tertiary level. In keeping with some of the ideas already introduced in this book, there is recognition that young people, including students, tend to make their own mobility, using their agency to help them cope with the challenges of living in foreign countries. It is also largely up to these individuals to make value, and make sense, out of this mobility, and to secure the transition from one mobile learning phase to another. Therefore, while the topics discussed in the subsequent chapters are all substantially different, they share recognition of students’ role in managing their own mobility. As such, what we have are accounts of free movement in tertiary education; free in the sense of being guided by one’s own needs and desires, but not free in terms of emotional and economic costs.info:eu-repo/semantics/acceptedVersio

Effect of pH on pulping and flotation of mixed office wastepaper

Journal ArticleThe effect of pulping reagents on the deinking flotation of laser-printed wastepaper was investigated with regard to the removal efficiency of toner and mineral filler particles at different pH values. These results show that caustic pulping causes the toner to be released from the fibres as larger particles and a poor flotation response is obtained. On the other hand, neutral pulping not only causes the toner to be released as smaller particles but also increases the simultaneous flotation removal of toner and mineral filler particles. On the basis of these flotation results and atomic force microscopy force experiments, it is known that the remarkable removal of mineral fillers and toner particles under acidic conditions is related to the heterocoagulation of toner and filler particles