3,553 research outputs found
Optimal On-Off Attitude Control for the Brazilian Multimission Platform Satellite
This work deals with the analysis and design of a reaction thruster attitude control for the Brazilian Multimission platform satellite. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high nonlinear control action. This work considers the Pulse-Width Pulse-Frequency (PWPF) modulator which is composed of a Schmidt trigger, a first-order filter, and a feedback loop. PWPF modulator holds several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption. The Linear Gaussian Quadratic (LQG) technique is used to synthesize the control law during stabilization mode and the modulator is used to modulate the continuous control signal to discrete one. Numerical simulations are
used to analyze the performance of the attitude control. The LQG/PWPF approach achieves good stabilization-mode requirements as disturbances rejection and regulation performance
Germinação de sementes de jacarandá do pará (Dalbergia spruceana Benth.), coletadas em belterra - PA.
Variabilidade entre isolados de Trichoderma spp. quanto à capacidade de inibir o crescimento de Cylindrocladium sp. em cultivo pareado.
bitstream/CENARGEN/29462/1/bp186.pd
Cobb's collar and chronic renal failure
Pontificia Univ Catolica Campinas, Campinas, SP, BrazilUniv Fed Sao Paulo, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Sao Paulo, SP, BrazilWeb of Scienc
Processor-in-the-Loop Simulations Applied to the Design and Evaluation of a Satellite Attitude Control
Forward scattering amplitudes in the imaginary time formalism
We study, in the imaginary time formalism, the relation between loops and
on-shell forward scattering tree amplitudes in thermal field theories. This
allows for an efficient evaluation, at all temperatures, of Green's functions
with causal retarded boundary conditions. We present an application of this
relation in quantum gravity coupled to scalar matter fields. We show that at
one or two loops, involving planar diagrams, the 1PI retarded thermal Green's
functions may respectively be expressed in terms of connected forward
scattering tree amplitudes of one or two on-shell particles.Comment: 15 pages, four figures. Published in Physical Review D (typos
corrected
Thermal gauge theories with Lagrange multiplier fields
We study the Yang-Mills theory and quantum gravity at finite temperature, in
the presence of Lagrange multiplier fields. These restrict the path integrals
to field configurations which obey the classical equations of motion. This has
the effect of doubling the usual one--loop thermal contributions and of
suppressing all radiative corrections at higher loop order. Such theories are
renormalizable at all temperatures. Some consequences of this result in quantum
gravity are briefly examined.Comment: 8 pages, 4 figures. To appear in the Canadian Journal of Physics
(typos corrected
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