A NOTE ON TRANSIENT HEAT TRANSFER PROBLEMS WITH TEMPERATURE-DEPENDENT THERMAL CONDUCTIVITY AND THERMAL DIFFUSIVITY

In this work it is presented a numerical procedure for solving transient heat transfer problems in which the thermal diffusivity is strongly dependent on the temperature, with the aid of the Kirchhoff transformation associated to an usual finite difference approach. The first step consists of eliminating the nonlinear terms associated to the derivatives with respect to the position, by means of a Kirchhoff transformation, giving rise to a partial differential equation with only one nonlinear term (involving the coefficient of the derivative with respect to the time). The advance in time is carried out assuming the thermal diffusivity evaluated at a known temperature, giving rise to a semi-implicit scheme. Comparisons between this approach and the usual hypothesis are carried out in order to illustrate the effect of the dependence between the temperature and the thermal diffusivity. Some typical results are presented, based on the (6H-SiC) Silicon Carbide properties

Development of a sequential injection method for bromate determination in soil leachates

info:eu-repo/semantics/publishedVersio

On the Influence of Magnetic Fields on the Structure of Protostellar Jets

We here present the first results of fully three-dimensional (3-D) MHD simulations of radiative cooling pulsed (time-variable) jets for a set of parameters which are suitable for protostellar outflows. Considering different initial magnetic field topologies in approximate $equipartition$ with the thermal gas, i.e., (i) a longitudinal, and (ii) a helical field, both of which permeating the jet and the ambient medium; and (iii) a purely toroidal field permeating only the jet, we find that the overall morphology of the pulsed jet is not very much affected by the presence of the different magnetic field geometries in comparison to a nonmagnetic calculation. Instead, the magnetic fields tend to affect essentially the detailed structure and emission properties behind the shocks at the head and at the pulse-induced internal knots, particularly for the helical and toroidal geometries. In these cases, we find, for example, that the $H_\alpha$ emissivity behind the internal knots can be about three to four times larger than that of the purely hydrodynamical jet. We also find that some features, like the nose cones that often develop at the jet head in 2-D calculations involving toroidal magnetic fields, are smoothed out or absent in the 3-D calculations.Comment: 13 pages, 3 figures, Accepted by ApJ Letters after minor corrections (for high resolution figures, see http://www.iagusp.usp.br/~adriano/h.tar

Híbridos de bananeira ornamental com potencial para paisagismo.

Ao longo dos últimos anos, a floricultura brasileira vem adquirindo notável desenvolvimento e se caracteriza como um dos mais promissores segmentos da horticultura intensiva no campo dos agronegócios nacionais (JUNQUEIRA; PEETZ, 2008). Um dos aspectos que contribui para a expansão são as condições climáticas do Brasil que favorecem o cultivo de flores, tanto de clima temperado como tropical (FRANÇA; MAIA, 2008)

Magnetically Driven Outflows in a Starburst Environment

We here investigate the possibility that the observed collimated outflows in luminous infrared galaxies (LIGs) and some Seyfert galaxies can be produced in a starburst (SB) environment. A nuclear disk can be quickly produced by gas infall during star formation in a rotating, stellar cluster. We find that massive nuclear SBs with core disk masses M_d \sim 10^8 - 10^9 M_{\odot}, and supernova rates \nu_{SN} \simeq 5 \times 10^{-3} - 2 yr^{-1} (which are consistent with the \nu_{SN} values inferred from the observed non-thermal radio power in source candidates) may inject kinetic energies which are high enough to blow out directed flows from the accreting disk surface, within the SB lifetimes. In our models, the acceleration and collimation of the nuclear outflow are provided by magnetic fields anchored into the rotating SB-disk. The emerging outflow carries a kinetic power that is only a small fraction (a few percent) of the supernovae energy rate produced in the SB. Based on conditions determined from observed outflows and disks, we find that moderate disk magnetic fields (\gtrsim 8 \times 10^{-4} G) are able to accelerate the outflows up to the observed terminal velocities (\lesssim few 100 km s^{-1} in the case of the Seyfert galaxies, and \sim 400 - 950 km s^{-1} in the case of the LIGs). The outflow is produced within a wind zone in the disk of radius \lesssim 100 pc in the LIGs, and \lesssim 10 pc in the Seyferts, with wind mass loss to disk accretion rate ratios \dot M_w /\dot M_d \gtrsim 0.1 (where \dot M_d \sim 100 M_{\odot} yr^{-1}). The observation of rotating nuclear disks of gas within few 100 pc scales in source candidates like the LIG Arp 220, and magnetized outflows provide observational support for the picture drawn here.Comment: 31 pages, Latex file, 1 Figure, accepted for publication in the Astrophys. Journa

Sunki mandarin and Swingle citrumelo as rootstocks for rain-fed cultivation of late-season sweet orange selections in northern São Paulo state, Brazil.

In Brazilian regions affected by the citrus sudden death disease, sweet orange cultivation depends on the use of resistant rootstocks. Rangpur lime was mainly replaced by Swingle citrumelo and Sunki mandarin rootstocks, more drought-sensitive ones. The diversification of scion selections is also desirable aiming at the increasing demand for not from concentrate orange juice (NFC) that requires high-quality fruits. In this work, we evaluated the performance of 6 selections of Valencia (IAC, Dom João, Late Burjasot IVIA 35-2, Rhode Red SRA 360, Temprana IVIA 25 and Campbell) and Natal IAC sweet oranges grafted onto Swingle citrumelo and Sunki mandarin. The planting occurred in 2001 under rain-fed cultivation in Bebedouro, northern São Paulo state, Brazil. The outline was made through randomized blocks in a 7 × 2 factorial design (selections × rootstock), with 4 replications and 2 trees in unit. Both rootstocks performed well in the region. Sunki mandarin rootstock induced greater tree size and production per plant to the scion selections, 38 and 21%, respectively, plus higher precocity of production compared to Swingle citrumelo. The later determined a greater productive efficiency, as well as a greater percentage of juice in general, albeit with lower concentrations of soluble solids and acidity. Natal IAC, Valencia IAC and Rhode Red Valencia selections presented a higher accumulated production, on average, 218.6 kg?plant?1 (2004 ? 2008), and a higher productive efficiency (kg fruit?m?3 of canopy) due to their smaller tree size. All assessed selections produced fruits with high soluble solids content that were suitable for juice processing

Caracterização de híbridos ornamentais de bananeira.

As fruteiras ornamentais são uma alternativa para o segmento da floricultura, possuem grande plasticidade de uso podendo ser apreciadas como plantas de parques, jardins, flores de corte, plantas de vaso, folhagens e minifrutos ornamentais. O Banco de Germoplasma de Bananeira da Embrapa Mandioca e Fruticultura possui acessos de diferentes seções do gênero Musa.PDF. 120_11

Demanda de informação em sistemas agroflorestais para agricultura familiar sustentável no Nordeste paraense.

Práticas alternativas começam a ser vistas como uma garantia de preservação dos sistemas produtivos da agricultura familiar. O uso de sistemas alternativos para recuperação de áreas degradadas e/ou abandonadas é fundamental para alcançar sustentabilidade de unidades de produção familiar rurais, com propostas tecnológicas e baseadas no conhecimento e uso racional dos recursos naturais. Disponibilizar alternativas sustentáveis à recuperação de áreas degradadas com agricultura e pastagens com vistas ao uso sustentado da terra e melhoria de vida dos agricultores da Amazônia foi objetivo do projeto "Desenvolvimento e Validação de Estratégias Participativas de Recuperação de Áreas Agrícolas e Pastagens Degradadas na Amazônia", componente da Sub-Rede RECUPERAMAZ. Para viabilizar o processo de divulgação científica dos resultados de pesquisa, foi realizada uma ação de identificação de demanda por informação, aplicando-se metodologia apropriada e adaptada, para 81 agricultores familiares, representantes de 16 associações comunitárias rurais, distribuídos entre os municípios de Igarapé-Açu, Mãe do Rio e Concórdia do Pará, região Nordeste Paraense. Os resultados indicam que os agricultores apresentam um perfil que facilita o processo de divulgação dos resultados de pesquisas, com maior ou menor habilidade para uso de diferentes mídias e fontes. Demonstram interesse em "novos" conhecimentos, i.e. através das informações fornecidas por técnicos, pelas instituições governamentais e não-governamentais entre outros e demandam informações relacionadas às suas práticas agrícolas cotidianas para soluções de diferentes problemas