6,706 research outputs found
Control law synthesis and optimization software for large order aeroservoelastic systems
A flexible aircraft or space structure with active control is typically modeled by a large-order state space system of equations in order to accurately represent the rigid and flexible body modes, unsteady aerodynamic forces, actuator dynamics and gust spectra. The control law of this multi-input/multi-output (MIMO) system is expected to satisfy multiple design requirements on the dynamic loads, responses, actuator deflection and rate limitations, as well as maintain certain stability margins, yet should be simple enough to be implemented on an onboard digital microprocessor. A software package for performing an analog or digital control law synthesis for such a system, using optimal control theory and constrained optimization techniques is described
A deep i-selected multi-waveband galaxy catalogue in the COSMOS field
In this paper we present a deep and homogeneous i-band selected
multi-waveband catalogue in the COSMOS field covering an area of about 0.7
square-degree. Our catalogue with a formal 50 percent completeness limit for
point sources of i~26.7 comprises about 290.000 galaxies with information in 8
passbands. We combine publicly available u, B, V, r, i, z, and K data with
proprietary imaging in H band. We discuss in detail the observations, the data
reduction, and the photometric properties of the H-band data. We estimate
photometric redshifts for all the galaxies in the catalogue. A comparison with
162 spectroscopic redshifts in the redshift range 0 < z < 3 shows that the
achieved accuracy of the photometric redshifts is (Delta_z / (z_spec+1)) ~0.035
with only ~2 percent outliers. We derive absolute UV magnitudes and investigate
the evolution of the luminosity function evaluated in the rest-frame UV at 1500
Angstrom. There is a good agreement between the LFs derived here and the LFs
derived in the FORS Deep Field. We see a similar brightening of M_star and a
decrease of phi_star with redshift. The catalogue including the photometric
redshift information is made publicly available.Comment: 20 pages, 17 figures, accepted for publication in MNRAS; high
resulution paper: http://www.mpe.mpg.de/~gabasch/COSMOS/cosmos.pd
Rotational properties of the binary and non-binary populations in the Trans-Neptunian belt
We present results for the short-term variability of Binary Trans-Neptunian
Objects (BTNOs). We performed CCD photometric observations using the 3.58 m
Telescopio Nazionale Galileo, the 1.5 m Sierra Nevada Observatory telescope,
and the 1.23 m Centro Astronomico Hispano Aleman telescope at Calar Alto
Observatory. We present results based on five years of observations and report
the short-term variability of six BTNOs. Our sample contains three classical
objects: 2003MW12, or Varda, 2004SB60, or Salacia, and 2002 VT130; one detached
disk object: 2007UK126; and two resonant objects: 2007TY430 and 2000EB173, or
Huya. For each target, possible rotational periods and/or photometric
amplitudes are reported. We also derived some physical properties from their
lightcurves, such as density, primary and secondary sizes, and albedo. We
compiled and analyzed a vast lightcurve database for Trans-Neptunian Objects
(TNOs) including centaurs to determine the lightcurve amplitude and spin
frequency distributions for the binary and non-binary populations. The mean
rotational periods, from the Maxwellian fits to the frequency distributions,
are 8.63+/-0.52 h for the entire sample, 8.37+/-0.58 h for the sample without
the binary population, and 10.11+/-1.19 h for the binary population alone.
Because the centaurs are collisionally more evolved, their rotational periods
might not be so primordial. We computed a mean rotational period, from the
Maxwellian fit, of 8.86+/-0.58 h for the sample without the centaur population,
and of 8.64+/-0.67 h considering a sample without the binary and the centaur
populations. According to this analysis, regular TNOs spin faster than
binaries, which is compatible with the tidal interaction of the binaries.
Finally, we examined possible formation models for several systems studied in
this work and by our team in previous papers.Comment: Accepted for publication in Astronomy and Astrophysics (June 26th,
2014); minor changes with published version; 21 pages, 17 figures, 7 table
Linking Billy Sunday and the Mystique of the Middle West to the Religious History of Iowa
Breadboard linear array scan imager using LSI solid-state technology
The performance of large scale integration photodiode arrays in a linear array scan (pushbroom) breadboard was evaluated for application to multispectral remote sensing of the earth's resources. The technical approach, implementation, and test results of the program are described. Several self scanned linear array visible photodetector focal plane arrays were fabricated and evaluated in an optical bench configuration. A 1728-detector array operating in four bands (0.5 - 1.1 micrometer) was evaluated for noise, spectral response, dynamic range, crosstalk, MTF, noise equivalent irradiance, linearity, and image quality. Other results include image artifact data, temporal characteristics, radiometric accuracy, calibration experience, chip alignment, and array fabrication experience. Special studies and experimentation were included in long array fabrication and real-time image processing for low-cost ground stations, including the use of computer image processing. High quality images were produced and all objectives of the program were attained
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