5,727 research outputs found
Magnetically assisted self-injection and radiation generation for plasma based acceleration
It is shown through analytical modeling and numerical simulations that
external magnetic fields can relax the self-trapping thresholds in plasma based
accelerators. In addition, the transverse location where self-trapping occurs
can be selected by adequate choice of the spatial profile of the external
magnetic field. We also find that magnetic-field assisted self-injection can
lead to the emission of betatron radiation at well defined frequencies. This
controlled injection technique could be explored using state-of-the-art
magnetic fields in current/next generation plasma/laser wakefield accelerator
experiments.Comment: 7 pages, 4 figures, accepted for publication in Plasma Physics and
Controlled Fusio
Marketing tecnológico, uma ferramenta de transferência de tecnologia: a experiência da Embrapa Soja.
Introdução; Conceitos; Interface marketing transferência de tecnologia; Ambiente de marketing; Modelos de transferência de tecnologia ou marketing tecnológico adotados pela Embrapa Soja; Ferramentas; Serviços; Meio eletrônico.bitstream/item/57798/1/Documentos-207.pd
Experimental observation of two-dimensional fluctuation magnetization in the vicinity of T_c for low values of the magnetic field in deoxygenated YBa_2Cu_3O_{7-x}
We measured isofield magnetization curves as a function of temperature in two
single crystal of deoxygenated YBaCuO with T_c = 52 and 41.5 K. Isofield MvsT
were obtained for fields running from 0.05 to 4 kOe. The reversible region of
the magnetization curves was analyzed in terms of a scaling proposed by Prange,
but searching for the best exponent . The scaling analysis carried
out for each data sample set with =0.669, which corresponds to the
3D-xy exponent, did not produced a collapsing of curves when applied to MvsT
curves data obtained for the lowest fields. The resulting analysis for the Y123
crystal with T_c = 41.5 K, shows that lower field curves collapse over the
entire reversible region following the Prange's scaling with =1,
suggesting a two-dimensional behavior. It is shown that the same data obeying
the Prange's scaling with =1 for crystal with T_c = 41.5 K, as well
low field data for crystal with = 52 K, obey the known two-dimensional
scaling law obtained in the lowest-Landau-level approximation.Comment: 4 pages, 3 figure
Modeling and Simulation of an Oxygen Delignification Industrial Process of Cellulosic Pulp using Kinetic Expressions and the software CADSIM Plus
<p>The Brazilian productive sector of pulp and paper represents a relevant contribution for the development of Brazil. To increase the competitiveness of Brazilian companies to an International level, products must have high standards of quality and high added value. Thus, the mathematical modeling and simulation of industrial processes ensures the stability of production. This study presents the fit of mathematical models for the Oxygen Delignification process of eucalyptus pulp of the industry Klabin Monte Alegre. The mathematical model estimates the kappa number after the reactor, based on two kinetic models given by the literature, one of these models considers oxygen excess in the reaction medium. The models showed a mean relative error of 10 %. The adjustment of the kinetic parameters equations was done in Matlab software, using classical methods of optimization, such as BFGS, DFP, Steepest Descent, Gauss Newton, Simplex and Levenberg Marquardt. The models were incorporated in the commercial simulator CADSIM Plus to provide an optimization tool to the pulp industries. The simulator predicts the kappa number after the Oxygen Delignification reactor. The results of the phenomenological models indicate that possibly there is excess of oxygen in the reaction media. Only the model that considered the presence of the oxygen in the kinetic equation was able to be implemented in the simulator CADSIM Plus, generating consistent results, with an absolute error of &plusmn; 2 kappa number. Application: The kinetic model applied to the CADSIM Plus software in this study may be used to optimize the Oxygen Delignification process either by reducing chemical consumptions or by testing different process conditions without changing production.</p>
Magnetic control of particle-injection in plasma based accelerators
The use of an external transverse magnetic field to trigger and to control
electron self-injection in laser- and particle-beam driven wakefield
accelerators is examined analytically and through full-scale particle-in-cell
simulations. A magnetic field can relax the injection threshold and can be used
to control main output beam features such as charge, energy, and transverse
dynamics in the ion channel associated with the plasma blowout. It is shown
that this mechanism could be studied using state-of-the-art magnetic fields in
next generation plasma accelerator experiments.Comment: 10 pages, 3 figure
Avaliação preliminar de populações de cenoura para reação à mistura populacional de Meloidogyne incognita raça 1 e Meloidogyne javanica.
bitstream/CNPH-2010/36464/1/bpd-61.pd
Electron trapping and acceleration by the plasma wakefield of a self-modulating proton beam
It is shown that co-linear injection of electrons or positrons into the
wakefield of the self-modulating particle beam is possible and ensures high
energy gain. The witness beam must co-propagate with the tail part of the
driver, since the plasma wave phase velocity there can exceed the light
velocity, which is necessary for efficient acceleration. If the witness beam is
many wakefield periods long, then the trapped charge is limited by beam loading
effects. The initial trapping is better for positrons, but at the acceleration
stage a considerable fraction of positrons is lost from the wave. For efficient
trapping of electrons, the plasma boundary must be sharp, with the density
transition region shorter than several centimeters. Positrons are not
susceptible to the initial plasma density gradient.Comment: 9 pages, 9 figures, 1 table, 44 reference
Genetic parameter and correlation estimates of processing traits in half-sib progenies of tropical-adapted carrot germplasm.
Setenta e quatro progênies meio-irmãs derivadas de 'Alvoradas' foram avaliadas durante o verão de 2005 no Distrito Federal (DF), em blocos casualizados com três repetições
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