40,463 research outputs found
Application of optimal control theory to the design of the NASA/JPL 70-meter antenna servos
The application of Linear Quadratic Gaussian (LQG) techniques to the design of the 70-m axis servos is described. Linear quadratic optimal control and Kalman filter theory are reviewed, and model development and verification are discussed. Families of optimal controller and Kalman filter gain vectors were generated by varying weight parameters. Performance specifications were used to select final gain vectors
Critical Exponents in a Quantum Phase Transition of an Anisotropic 2D Antiferromagnet
I use the two-step density-matrix renormalization group method to extract the
critical exponents and in the transition from a N\'eel
phase to a magnetically disordered phase with a spin gap. I find
that the exponent computed from the magnetic side of the transition is
consistent with that of the classical Heisenberg model, but not the exponent
computed from the disordered side. I also show the contrast between
integer and half-integer spin cases.Comment: 4 pages, 2 figure
A Survey of the Spacecraft Line-Of-Sight Jitter Problem
Predicting, managing, controlling, and testing spacecraft Line-of-Sight (LoS) jit- ter due to on-board internal disturbance sources is a challenging multi- disciplinary systems engineering problem, especially for those observatories hosting extremely sensitive optical sensor payloads with stringent requirements on allowable LoS jitter. Some specific spacecraft jitter engineering challenges will be introduced and described in this survey paper. Illustrative examples of missions where dynamic interactions have to be addressed to satisfy demanding payload instrument LoS jitter requirements will be provided. Some lessons learned and a set of recommended rules of thumb are also presented to provide guidance for analysts on where to initiate and how to approach a new spacecraft jitter design problem. These experience-based spacecraft jitter lessons learned and rules of thumb are provided in the hope they can be leveraged on new space system development projects to help overcome unfamiliarity with previously identified jitter technical pitfalls and challenges
Treatment of dogs with compensated myxomatous mitral valve disease with spironolactone-a pilot study
Spironolactone improves outcome in dogs with advanced myxomatous mitral valve disease (MMVD). Its efficacy in preclinical MMVD is unknown. The hypothesis was the administration of spironolactone to dogs with compensated MMVD demonstrating risk factors for poorer prognosis will decrease the rate of disease progression. The aim was to provide pilot data to evaluate preliminary effects and sample size calculation for a definitive clinical trial
Charged current neutrino induced coherent pion production
We analyze the neutrino induced charged current coherent pion production at
the energies of interest for recent experiments like K2K and MiniBooNE. Medium
effects in the production mechanism and the distortion of the pion wave
function, obtained solving the Klein Gordon equation with a microscopic optical
potential, are included in the calculation. We find a strong reduction of the
cross section due to these effects and also substantial modifications of the
energy distributions of the final lepton and pion.Comment: 11 pages, 6 figures. Some details and new references added; results
unchanged. Accepted in PR
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