27,965 research outputs found
Segurança operacional de exploração florestal mecanizada.
bitstream/item/33956/1/CPATU-CirTec42.pd
Composição da lignina de três espécies forrageiras visando à produção de bioetanol.
Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
Construção de estradas florestais e transporte florestal rodoviário na região amazônica.
bitstream/item/33677/1/CPATU-CirTec6.pd
Massive stars and globular cluster formation
We first present chemodynamical simulations to investigate how stellar winds
of massive stars influence early dynamical and chemical evolution of forming
globular clusters (GCs). In our numerical models, GCs form in
turbulent,high-density giant molecular clouds (GMCs), which are embedded in a
massive dark matter halo at high redshifts. We show how high-density, compact
stellar systems are formed from GMCs influenced both by physical processes
associated with star formation and by tidal fields of their host halos. We also
show that chemical pollution of GC-forming GMCs by stellar winds from massive
stars can result in star-to-star abundance inhomogeneities among light elements
(e.g., C, N, and O) of stars in GCs. The present model with a canonical initial
mass function (IMF) also shows a C-N anticorrelation that stars with smaller
[C/Fe] have larger [N/Fe] in a GC. Although these results imply that
``self-pollution'' of GC-forming GMCs by stellar winds from massive stars can
cause abundance inhomogeneities of GCs, the present models with different
parameters and canonical IMFs can not show N-rich stars with [N/Fe] ~ 0.8
observed in some GCs (e.g., NGC 6752). We discuss this apparent failure in the
context of massive star formation preceding low-mass one within GC-forming GMCs
(``bimodal star formation scenario''). We also show that although almost all
stars (~97%) show normal He abundances (Y) of ~0.24 some stars later formed in
GMCs can have Y as high as ~0.3 in some models. The number fraction of He-rich
stars with Y >0.26 is however found to be small (~10^-3) for most models.Comment: 10 pages, 8 figures, accepted by Ap
On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining
Capitalizing on the recently proposed Fisher-Snedecor F composite fading
model, in this letter, we investigate the sum of independent but not
identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel
closed-form expression is derived for the moment generating function of the
instantaneous signal-to-noise ratio. Based on this, the corresponding
probability density function and cumulative distribution function of the sum of
i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently
employed in the analysis of multiple branch maximal-ratio combining (MRC).
Specifically, we investigate the impact of multipath and shadowed fading on the
outage probability and outage capacity of MRC based receivers. In addition, we
derive exact closed-form expressions for the average bit error rate of coherent
binary modulation schemes followed by an asymptotic analysis which provides
further insights into the effect of the system parameters on the overall
performance. Importantly, it is shown that the effect of multipath fading on
the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure
Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3
We present a magnetoresistive-photoresistive device based on the interaction
of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that
undergoes light-induced strain. The magnitude of the resistance and
magnetoresistance in the CoFe film can be controlled by the wavelength of the
incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic
magnetoresistance is detected due to an additional magnetoelastic contribution
to magnetic anisotropy of the CoFe film. This effect may find applications in
photo-sensing systems, wavelength detectors and can possibly open a research
development in light-controlled magnetic switching properties for next
generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape
Hierarchical Spatial Organization of Geographical Networks
In this work we propose the use of a hirarchical extension of the
polygonality index as a means to characterize and model geographical networks:
each node is associated with the spatial position of the nodes, while the edges
of the network are defined by progressive connectivity adjacencies. Through the
analysis of such networks, while relating its topological and geometrical
properties, it is possible to obtain important indications about the
development dynamics of the networks under analysis. The potential of the
methodology is illustrated with respect to synthetic geographical networks.Comment: 3 page, 3 figures. A wokring manuscript: suggestions welcome
Caracterização físico-hídrica de latossolo amarelo da região de Capitão Poço, Pará.
bitstream/item/42255/1/Boletim-Pesquisa-133-CPATU.pd
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