Relating L-Resilience and Wait-Freedom via Hitting Sets

The condition of t-resilience stipulates that an n-process program is only obliged to make progress when at least n-t processes are correct. Put another way, the live sets, the collection of process sets such that progress is required if all the processes in one of these sets are correct, are all sets with at least n-t processes. We show that the ability of arbitrary collection of live sets L to solve distributed tasks is tightly related to the minimum hitting set of L, a minimum cardinality subset of processes that has a non-empty intersection with every live set. Thus, finding the computing power of L is NP-complete. For the special case of colorless tasks that allow participating processes to adopt input or output values of each other, we use a simple simulation to show that a task can be solved L-resiliently if and only if it can be solved (h-1)-resiliently, where h is the size of the minimum hitting set of L. For general tasks, we characterize L-resilient solvability of tasks with respect to a limited notion of weak solvability: in every execution where all processes in some set in L are correct, outputs must be produced for every process in some (possibly different) participating set in L. Given a task T, we construct another task T_L such that T is solvable weakly L-resiliently if and only if T_L is solvable weakly wait-free

Potencial da macaubeira como fonte de matéria-prima para produção de biodiesel.

bitstream/item/78012/1/doc-217.pd

Comparison Of Anisotropy Reduction Strategies For Transformation Optics Designs

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In this paper, we present new strategies to reduce anisotropy in transformation optics designs and compare them to other techniques. Perturbation functions are used to modify the original transformation to achieve a quasi-conformal map, resulting in a medium with isotropic properties. All strategies investigated have no effect on the original boundary conditions of the transformation, such that neither the initial design is affected nor are reflections at the boundaries introduced. The results show that there exists a clear compromise between the residual anisotropy and the required refractive index contrast in the optimized transformation, but the former can be made as small as desired when the degree of freedom provided by perturbation functions is increased, although it is never exactly zero.71Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Tungsten in barium stars

Classical barium stars are red giants that received from their evolved binary companions material exposed to the \textit{slow} neutron-capture nucleosynthesis, i.e., the $s$-process. Such a mechanism is expected to have taken place in the interiors of Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) stars. As post-interacting binaries, barium stars figure as powerful tracers of the $s$-process nucleosynthesis, evolution of binary systems, and mechanisms of mass transfer. The present study is the fourth in a series of high-resolution spectroscopic analyses on a sample of 180 barium stars, for which we report tungsten (W, $Z=74$) abundances. The abundances were derived from synthetic spectrum computations of the W\,{\sc i} absorption features at 4\,843.8~\AA\ and 5\,224.7~\AA. We were able to extract abundances for 94 stars; the measured [W/Fe] ratios range from $\sim0.0$ to $2.0$ dex, increasing with decreasing of metallicity. We noticed that in the plane [W/Fe] versus [$s$/Fe] barium stars follow the same trend observed in post-AGB stars. The observational data were also compared with predictions of the {\sc fruity} and Monash AGB nucleosynthesis models. These expect values between $-0.20$ and $+0.10$ dex for the [W/hs] ratios, whereas a larger spread is observed in the program stars, with [W/hs] ranging from $-0.40$ to $+0.60$ dex. The stars with high [W/hs] ratios may represent evidence for the operation of the intermediate neuron-capture process at metallicities close to solar.Comment: 11 pages, 4 figures, accepted for publication in MNRA

Qual é sua pegada?: o reflexo de seu consumo.

Pegada Ecológica. Consumo versus produção de lixo. O que são materiais recicláveis e não recicláveis. Resíduos recicláveis. Resíduos não recicláveis. Resíduos orgânicos. Resíduos químicos ou tóxicos. Resíduos potencialmente perigosos. Como contribuir para o equilíbrio do ambiente em que vivemos?. Curiosidades. Teste: Quanto você pesa para o planeta?. Fluxograma de gerenciamento dos resíduos gerais da Embrapa Arroz e Feijão. Canecas versus copos descartáveis. Colabore para uma empresa ambientalmente responsável.bitstream/CNPAF-2010/29764/1/doc-245.pd

High-resolution spectroscopic analysis of four new chemically peculiar stars

We present detailed chemical compositions of four stars on the first-ascent red giant branch that are classified as chemically peculiar, but lack comprehensive analyses at high spectral resolution. For BD+03{\deg}2688, HE 0457-1805, HE 1255-2324, and HE 2207-1746, we derived metallicities [Fe/H] $=-1.21$, $-0.19$, $-0.31$, and $-0.55$, respectively, indicating a range in Galactic population membership. In addition to atmospheric parameters, we extracted elemental abundances for 28 elements, including the evolutionary-sensitive CNO group and $^{12}$C/$^{13}$C ratios. Novel results are also presented for the heavy elements tungsten and thallium. All four stars have very large enhancements of neutron-capture elements, with high [La/Eu] ratios indicating enrichments from the slow neutron capture ($s$-process). To interpret these abundances, all indicative of [$s$/Fe] $> 1.0$, we compared our results with data from literature, as well as with predictions from the Monash and FRUITY $s$-process nucleosynthesis models. BD+03{\deg}2688, HE 1255-2324, and HE 2207-1746 show C/O $>1$, while HE 0457-1805 has C/O $<1$. Since HE 0457-1805 and HE 1255-2324 are binary stars, their peculiarities are attributable to mass transfer. We identified HE 0457-1805 as a new barium giant star, and HE 1255-2324 as a new CH star, in fact a higher metallicity analogue CEMP-$r/s$ star; the single object reported in literature so far with similar characteristics is the barium star HD 100503 ([Fe/H] $= -0.72$). A systematic monitoring is needed to confirm the binary nature of BD+03{\deg}2688 and HE 2207-1746, which are probably CH stars.Comment: 33 pages, 24 figures, accepted for publication in MNRA

Construindo a identidade agroecológica através de trocas de experiências entre assentamentos da reforma agrária no estado de São Paulo.

Resumo: Este trabalho faz parte do projeto ?Capacitação sócio-ambiental para construção de projetos de desenvolvimento sustentável em assentamentos rurais no estado de São Paulo?, uma parceria da Embrapa Meio Ambiente com o INCRA, MST e outras organizações de agricultores assentados. Assim, propomos apresentar uma etapa dos trabalhos que vem sendo desenvolvido nos assentamentos Itapeva e Sepé Tiaraju, nos respectivos municípios de Itapeva/SP e Ribeirão Preto/SP. Iniciado em 2009, este trabalho visa a assessorar e potencializar os trabalhos de transição agroecológica através da aproximação de agricultores assentados com processos diferentes de ocupação da terra, porém com mesmos objetivos de diversificação do sistema produtivo de forma sustentável. Abstract: This work is part of the project "Capacity building for social and environmental projects for sustainable development in rural settlements in the state of São Paulo, a partnership withEmbrapa Environment INCRA, MST and other organizations offarmers settled.Therefore, we propose to present a step in the work being donein the settlements and Itapeva Sepe Tiaraju, in their municipality of Itapeva / SP, Ribeirao Preto / SP. Started in 2009, this work aims to assist and enhance the work through the transitionalagro- ecological approach to resettled farmers with different processes acupaçao of the earth, but with the same objectivesof diversification of the productive system in a sustainable manner