18,170 research outputs found
Numerical solution of open string field theory in Schnabl gauge
Using traditional Virasoro level-truncation computations, we evaluate
the open bosonic string field theory action up to level . Extremizing
this level-truncated potential, we construct a numerical solution for tachyon
condensation in Schnabl gauge. We find that the energy associated to the
numerical solution overshoots the expected value at level .
Extrapolating the level-truncation data for to estimate the vacuum
energies for , we predict that the energy reaches a minimum value at , and then turns back to approach asymptotically as . Furthermore, we analyze the tachyon vacuum expectation value (vev),
for which by extrapolating its corresponding level-truncation data, we predict
that the tachyon vev reaches a minimum value at , and then turns
back to approach the expected analytical result as .Comment: 37 pages, 9 figures, some typos correcte
Modeling the input history of programs for improved instruction-memory performance
When a program is loaded into memory for execution, the relative position of
its basic blocks is crucial, since loading basic blocks that are unlikely to be
executed first places them high in the instruction-memory hierarchy only to be
dislodged as the execution goes on. In this paper we study the use of Bayesian
networks as models of the input history of a program. The main point is the
creation of a probabilistic model that persists as the program is run on
different inputs and at each new input refines its own parameters in order to
reflect the program's input history more accurately. As the model is thus
tuned, it causes basic blocks to be reordered so that, upon arrival of the next
input for execution, loading the basic blocks into memory automatically takes
into account the input history of the program. We report on extensive
experiments, whose results demonstrate the efficacy of the overall approach in
progressively lowering the execution times of a program on identical inputs
placed randomly in a sequence of varied inputs. We provide results on selected
SPEC CINT2000 programs and also evaluate our approach as compared to the gcc
level-3 optimization and to Pettis-Hansen reordering
High coercivity induced by mechanical milling in cobalt ferrite powders
In this work we report a study of the magnetic behavior of ferrimagnetic
oxide CoFe2O4 treated by mechanical milling with different grinding balls. The
cobalt ferrite nanoparticles were prepared using a simple hydrothermal method
and annealed at 500oC. The non-milled sample presented coercivity of about 1.9
kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42.
After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and
saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence
ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To
investigate the influence of the microstructure on the magnetic behavior of
these samples, we used X-ray powder diffraction (XPD), transmission electron
microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by
the Williamson-Hall plot was used to estimate the average crystallite size and
strain induced by mechanical milling in the samples
Granulometria e conteúdos de carbono e nitrogênio do solo sob diferentes fitofisionomias da fazenda Nhumirim, Pantanal Sul-Mato-Grossense.
Análise de solos: finalidade e procedimentos de amostragem.
A análise de solos é o único método que permite, antes do plantio, conhecer a capacidade de um determinado solo suprir nutrientes para as plantas. É a forma mais simples, econômica e eficiente de diagnose da fertilidade das terras e constitui base imprescindÃvel para a recomendação de quantidades adequadas de corretivos e fertilizantes para aumentar a produtividade das culturas e, como consequência a produção e a lucratividade das lavouras.bitstream/CPAP-2010/57309/1/COT79.pd
Soil carbon and nitrogen stocks under natural forested savannah and cultivated pasture in the Pantanal, Mato Grosso do Sul, Brazil.
The goal of this study was to estimate the soil C and N stocks under Urochloa spp.pasture with a natural forested savannah as a reference.(Embrapa Gado de Corte. Documentos, 216). Coordenador Roberto Giolo de Almeida. II SIGEE. DisponÃvel em: . Acesso em: 30 nov. 2016
Os repositórios educacionais como auxiliares do ensino e suas múltiplas linguagens : vÃdeos
Neste trabalho é feita uma análise de um repositório educacional virtual: o Portal do Professor. Site governamental lançado pelo Ministério da Educação e da Cultura do Brasil (MEC) em parceria com o Ministério da Ciência e Tecnologia. O portal em questão se propõe a auxiliar a prática docente dos professores da Educação Básica (Educação Infantil, Ensino Fundamental e Médio, que no Brasil compreende crianças e jovens geralmente até os 17 anos). O portal oferece algumas ferramentas digitais, como textos digitais, aplicativos computacionais interativos, elementos visuais como fotos e desenhos, elementos auditivos, como sons, e elementos audiovisuais, foco de estudo deste trabalho. A articulação desses fatores, feita pelo próprio professor, pode resultar em aulas sobre determinado tema, que podem ser postadas e acessadas via internet
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