666 research outputs found
Design considerations of manipulator and feel system characteristics in roll tracking
A fixed-base simulation was performed to identify and quantify interactions between the pilot's hand/arm neuromuscular subsystem and such control system features of typical modern fighter aircraft roll rate command mechanizations as: (1) force versus displacement sensing side-stick type manipulator, (2) feel force/displacement gradient, (3) feel system versus command prefilter dynamic lag, and (4) flight control system effective time delay. The experiment encompassed some 48 manipulator/filter/aircraft configurations. Displacement side-stick experiment results are given and compared with the previous force sidestick experiment results. Attention is focused on control bandwidth, excitement (peaking) of the neuromuscular mode, feel force/displacement gradient effects, time delay effects, etc. Section 5 is devoted to experiments with a center-stick in which force versus displacement sensing, feel system lag, and command prefilter lag influences on tracking performance and pilot preference are investigated
Assessment of flying-quality criteria for air-breathing aerospacecraft
A study of flying quality requirements for air breathing aerospacecraft gives special emphasis to the unusual operational requirements and characteristics of these aircraft, including operation at hypersonic speed. The report considers distinguishing characteristics of these vehicles, including dynamic deficiencies and their implications for control. Particular emphasis is given to the interaction of the airframe and propulsion system, and the requirements for dynamic systems integration. Past operational missions are reviewed to define tasks and maneuvers to be considered for this class of aircraft. Areas of special concern with respect to vehicle dynamics and control are identified. Experience with the space shuttle orbiter is reviewed with respect to flight control system mechanization and flight experience in approach and landing flying qualities for the National Aerospace Plane (NASP)
SDSS J115517.35+634622.0: A Newly Discovered Gravitationally Lensed Quasar
We report the discovery of SDSSJ115517.35+634622.0, a previously unknown
gravitationally lensed quasar. The lens system exhibits two images of a quasar, with an image separation of 1{\farcs}832 \pm 0.007 . Near-IR
imaging of the system reveals the presence of the lensing galaxy between the
two quasar images. Based on absorption features seen in the Sloan Digital Sky
Survey (SDSS) spectrum, we determine a lens galaxy redshift of .
The lens is rather unusual in that one of the quasar images is only
0{\farcs}22\pm0{\farcs}07 () from the center of the
lens galaxy and photometric modeling indicates that this image is significantly
brighter than predicted by a SIS model. This system was discovered in the
course of an ongoing search for strongly lensed quasars in the dataset from the
SDSS.Comment: 18 pages, 6 figures. Accepted for publication in A
A Spectroscopic Survey of Faint Quasars in the SDSS Deep Stripe: I. Preliminary Results from the Co-added Catalog
In this paper we present the first results of a deep spectroscopic survey of
faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep
survey carried out by repeatedly imaging a 270 deg^2 area. Quasar candidates
were selected from the deep data with good completeness over 0<z<5, and 2 to 3
magnitudes fainter than the SDSS main survey. Spectroscopic follow-up was
carried out on the 6.5m MMT with Hectospec. The preliminary sample of this SDSS
faint quasar survey (hereafter SFQS) covers ~ 3.9 deg^2, contains 414 quasars,
and reaches g=22.5. The overall selection efficiency is ~ 66% (~ 80% at
g<21.5); the efficiency in the most difficult redshift range (2<z<3) is better
than 40%. We use the 1/V_{a} method to derive a binned estimate of the quasar
luminosity function (QLF) and model the QLF using maximum likelihood analysis.
The best model fits confirm previous results showing that the QLF has steep
slopes at the bright end and much flatter slopes (-1.25 at z<2.0 and -1.55 at
z>2.0) at the faint end, indicating a break in the QLF slope. Using a
luminosity-dependent density evolution model, we find that the quasar density
at M_{g}<-22.5 peaks at z~2, which is later in cosmic time than the peak of
z~2.5 found from surveys of more luminous objects. The SFQS QLF is consistent
with the results of the 2dF QSO Redshift Survey, the SDSS, and the 2dF-SDSS LRG
and QSO Survey, but probes fainter quasars. We plan to obtain more quasars from
future observations and establish a complete faint quasar sample with more than
1000 objects over 10 deg^2.Comment: 25 pages, 13 figures, accepted for publication in A
A comparison of health status in patients meeting alternative definitions for chronic fatigue syndrome/myalgic encephalomyelitis
BACKGROUND: Several diagnostic definitions are available for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) that varies significantly in their symptom criteria. This pilot study was conducted to determine whether simple biological and clinical measures differed between CFS/ME patients meeting the 1994 Centres for Disease Control and Prevention (CDC) criteria, the International Consensus Criteria (ICC), as well as healthy controls. METHODS: A total of 45 CFS/ME patients and 30 healthy controls from the South East Queensland region of Australia provided a blood sample, reported on their current symptoms, as well as aspects of their physical and social health using the Short-Form Health Survey (SF-36), and the World Health Organisation Disability Adjustment Schedule 2.0 (WHO DAS 2.0). Differences were examined using independent sample t-testing. RESULTS: Patients fulfilling the ICC definition reported significantly lower scores (pâ<â0.05) for physical functioning, physical role, bodily pain, and social functioning than those that only fulfilled the 1994 CDC definition. ICC patients reported significantly greater (pâ<â0.05) disability across all domains of the WHO DAS 2.0. CONCLUSIONS: These preliminary findings suggest that the ICC identifies a distinct subgroup found within patients complying with the 1994 CDC definition, with more severe impairment to their physical and social functioning
SDSS J092455.87+021924.9: an Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
We report the discovery of a new gravitationally lensed quasar from the Sloan
Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was
selected from among known SDSS quasars by an algorithm that was designed to
select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate
components, three of which are unresolved, are identified in photometric
follow-up observations obtained with the Magellan Consortium's 6.5m Walter
Baade telescope at Las Campanas Observatory. Two of the unresolved components
(designated A and B) are confirmed to be quasars with z=1.524; the velocity
difference is less than 100 km sec^{-1} according to spectra taken with the W.
M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar
component, designated C, has the colors of a quasar with redshift similar to
components A and B. The maximum separation of the point sources is 1.78". The
other two sources, designated G and D, are resolved. Component G appears to be
the best candidate for the lensing galaxy. Although component D is near the
expected position of the fourth lensed component in a four image lens system,
its properties are not consistent with being the image of a quasar at z~1.5.
Nevertheless, the identical redshifts of components A and B and the presence of
component C strongly suggest that this object is a gravitational lens. Our
observations support the idea that a foreground object reddens the fourth
lensed component and that another unmodeled effect (such as micro- or
milli-lensing) demagnificates it, but we cannot rule out the possibility that
SDSS0924+0219 is an example of the relatively rare class of ``three component''
lens systems.Comment: 24 pages, 6 figures, accepted by A
The Sloan Digital Sky Survey Quasar Lens Search. II. Statistical lens sample from the third data release
We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 (~4188 deg^2), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction-corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1" and 20" and flux ratios of faint to bright lensed images larger than 10^(â0.5). We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~ 1"-2") and one is a large separation (15") system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample
Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project
The dynamics of the core of the Sagittarius (Sgr) dwarf spheroidal (dSph)
galaxy are explored using high-resolution (R~22,500), H-band, near-infrared
spectra of over 1,000 giant stars in the central 3 deg^2 of the system, of
which 328 are identified as Sgr members. These data, among some of the earliest
observations from the SDSS-III/Apache Point Observatory Galactic Evolution
Experiment (APOGEE) and the largest published sample of high resolution Sgr
dSph spectra to date, reveal a distinct gradient in the velocity dispersion of
Sgr from 11-14 km/s for radii >0.8 degrees from center to a dynamical cold
point of 8 km/s in the Sgr center --- a trend differing from that found in
previous kinematical analyses of Sgr over larger scales that suggest a more or
less flat dispersion profile at these radii. Well-fitting mass models with
either cored and cusped dark matter distributions can be found to match the
kinematical results, although the cored profile succeeds with significantly
more isotropic stellar orbits than required for a cusped profile. It is
unlikely that the cold point reflects an unusual mass distribution. The
dispersion gradient may arise from variations in the mixture of populations
with distinct kinematics within the dSph; this explanation is suggested (e.g.,
by detection of a metallicity gradient across similar radii), but not
confirmed, by the present data. Despite these remaining uncertainties about
their interpretation, these early test data (including some from instrument
commissioning) demonstrate APOGEE's usefulness for precision dynamical studies,
even for fields observed at extreme airmasses.Comment: 15 pages, 3 figure
The Sloan Digital Sky Survey Quasar Lens Search. IV. Statistical Lens Sample from the Fifth Data Release
We present the second report of our systematic search for strongly lensed
quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive
follow-up observations of 136 candidate objects, we find 36 lenses in the full
sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release
5. We then define a complete sample of 19 lenses, including 11 from our
previous search in the SDSS Data Release 3, from the sample of 36,287 quasars
with i<19.1 in the redshift range 0.6<z<2.2, where we require the lenses to
have image separations of 1"<\theta<20" and i-band magnitude differences
between the two images smaller than 1.25 mag. Among the 19 lensed quasars, 3
have quadruple-image configurations, while the remaining 16 show double images.
This lens sample constrains the cosmological constant to be
\Omega_\Lambda=0.84^{+0.06}_{-0.08}(stat.)^{+0.09}_{-0.07}(syst.) assuming a
flat universe, which is in good agreement with other cosmological observations.
We also report the discoveries of 7 binary quasars with separations ranging
from 1.1" to 16.6", which are identified in the course of our lens survey. This
study concludes the construction of our statistical lens sample in the full
SDSS-I data set.Comment: 37 pages, 2 figures and 5 tables, accepted to A
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