3,508 research outputs found

    The value function of an asymptotic exit-time optimal control problem

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    We consider a class of exit--time control problems for nonlinear systems with a nonnegative vanishing Lagrangian. In general, the associated PDE may have multiple solutions, and known regularity and stability properties do not hold. In this paper we obtain such properties and a uniqueness result under some explicit sufficient conditions. We briefly investigate also the infinite horizon problem

    UV/Tio2 photocatalytic reactor for real textile wastewaters treatment

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    Textile dye wastewaters are characterized by strong colour, salts and other additives, high pH, temperature, chemical oxygen demand (COD) and biodegradable materials. Being aesthetically and environmentally unacceptable, these wastewaters need to be treated before their discharge. Anaerobic bioprocesses have been proposed as being environmentally friendly and relatively cheap; however, when applied to real effluent with a complex composition, they can fail. In this study, a photoreactor combining UV light and TiO2, immobilized in cellulosic fabric, was applied for the treatment of two industrial textile wastewaters. High colour and COD removal, and detoxification, were achieved for both wastewaters, at controlled pH of 5.5. Effluents showed very poor biodegradability due to their complex composition; thus, the proposed process is an efficient alternative

    Climate-dependent CO2 emissions from lakes

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    Inland waters, just as the world's oceans, play an important role in the global carbon cycle. While lakes and reservoirs typically emit CO2, they also bury carbon in their sediment. The net CO2 emission is largely the result of the decomposition or preservation of terrestrially supplied carbon. What regulates the balance between CO2 emission and carbon burial is not known, but climate change and temperature have been hypothesized to influence both processes. We analyzed patterns in carbon dioxide partial pressure (pCO2) in 83 shallow lakes over a large climatic gradient in South America and found a strong, positive correlation with temperature. The higher pCO2 in warmer lakes may be caused by a higher, temperature-dependent mineralization of organic carbon. This pattern suggests that cool lakes may start to emit more CO2 when they warm up because of climate ch

    Avaliação preliminar da influĂȘncia de barreira vegetal com sansĂŁo-do-campo (Mimosa caesalpiniaefolia Benth.) sobre a entomofauna em cultura de cafĂ© (Coffea arabica) orgĂąnico na regiĂŁo de Ivinhema, MS.

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    bitstream/item/68820/1/023-shimbori-avaliacao.pdfPublicado também no Cadernos de Agroecologia, v. 7, n. 2, 2012

    Cultivares de mandioca de mesa cultivadas sob manejo de base agroecolĂłgica em Dourados, MS, Brasil.

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    bitstream/item/68855/1/038-cultivares-motta.pdfPublicado também no Cadernos de Agroecologia, v. 7, n.2, 2012
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