1,076 research outputs found
Adaptive Control of Truss Structures for Gossamer Spacecraft
Neural network-based adaptive control is considered for active control of a highly flexible truss structure which may be used to support solar sail membranes. The objective is to suppress unwanted vibrations in SAFE (Solar Array Flight Experiment) boom, a test-bed located at NASA. Compared to previous tests that restrained truss structures in planar motion, full three dimensional motions are tested. Experimental results illustrate the potential of adaptive control in compensating for nonlinear actuation and modeling error, and in rejecting external disturbances
Adaptive Control of Truss Structures for Gossamer Spacecraft
Neural network-based adaptive control is considered for active control of a highly flexible truss structure which may be used to support solar sail membranes. The objective is to suppress unwanted vibrations in SAFE (Solar Array Flight Experiment) boom, a test-bed located at NASA. Compared to previous tests that restrained truss structures in planar motion, full three dimensional motions are tested. Experimental results illustrate the potential of adaptive control in compensating for nonlinear actuation and modeling error, and in rejecting external disturbances
Toward Microarcsecond Astrometry for the Innermost Wobbling Jet of the BL Lacertae Object OJ 287
The BL Lacertae object OJ 287 is a very unusual quasar producing a wobbling
radio jet and some double-peaked optical outbursts with a possible period of
about 12 yr for more than one century. This variability is widely explained by
models of binary supermassive black hole (SMBH) or precessing jet/disk from a
single SMBH. To enable an independent and nearly bias-free investigation on
these possible scenarios, we explored the feasibility of extremely
high-precision differential astrometry on its innermost restless jet at
mm-wavelengths. Through re-visiting some existing radio surveys and very long
baseline interferometry (VLBI) data at frequencies from 1.4 to 15.4 GHz and
performing new Very Long Baseline Array (VLBA) observations at 43.2 GHz, we
find that the radio source J08541959, 7.1 arcmin apart from OJ 287 and no
clearly-seen optical and infrared counterparts, could provide a nearly ideal
reference point to track the complicated jet activity of OJ 287. The source
J08541959 has a stable GHz-peaked radio spectrum and shows a jet structure
consisting of two discrete, mas-scale-compact and steep-spectrum components and
showing no proper motion over about 8 yr. The stable VLBI structure can be
interpreted by an episodic, optically thin and one-sided jet. With respect to
its 4.1-mJy peak feature at 43.2 GHz, we have achieved an astrometric precision
at the state-of-art level, about 10 as. These results indicate that future
VLBI astrometry on OJ 287 could allow us to accurately locate its jet apex and
activity boundary, align its restless jet structure over decades without
significant systematic bias, and probe various astrophysical scenarios.Comment: 10 pages, 3 figures, 2 tables, accepted for publication in
Astrophysical Journal Letter
Anti-inflammatory and antiarthritic effects of piperine in human interleukin 1β-stimulated fibroblast-like synoviocytes and in rat arthritis models
Transcortical Alterations in Na+-K+ ATPase and Microtubule-Associated Proteins Immunoreactivity in the Rat Cortical Atrophy Model Induced by Hypoxic Ischemia
To identify the chronological transcortical
change in the contralateral hemisphere
following ischemic insults, we investigated the
changes in microtubule associated protein
(MAP) and Na+-K+ ATPase expressions in the
peri-infarct zone and contralateral hemisphere,
including the hippocampus. Two days after
hypoxic ischemia, Na+-K+ ATPase immunoreactivity
was significantly enhanced in the
contralateral cortex and was maintained up to 7
days after ischemia, whereas Na+-K+ ATPase immunoreactivity in the peri- and infarct zones
was unaffected by hypoxic ischemia. In contrast,
2 to 7 days after ischemia, MAP1A and MAP2
immunoreactivity in the ipsi- and contralateral
cortex significantly decreased, whereas in layer
V, MAP1 immunoreactivity obviously accumulated
in the neurons and their processes. In the
hippocampus, 2 days after insults both MAP1A
and MAP2 immunoreactivity was significantly
reduced within the ipsi- and contralateral
hippocampus. In the contralateral hippocampus,
however, the distribution of MAP2 immunoreactivity
recovered to the sham level 7 days
after ischemia, whereas MAP1A immunoreactive
axons remained 2 months after
ischemia. The results suggest that the unilateral
elevation of Na+-K+ ATPase immunoreactivity
reflects elevated neuronal activity. In addition,
this asymmetric hyperexcitability might play an
important role in the recovery or the
reorganization of the brain, accompanied by
transcortical changes in MAPs expression
Successful Treatment of Stereotactic Body Radiation Therapy Combined with Transarterial Chemolipiodolization for Hepatocellular Carcinoma with Biliary Obstruction
Conventional radiation therapy (RT) is a widely recognized treatment for hepatocellular carcinoma (HCC). However, conventional RT plays only a limited role in HCC treatment because of its low efficacy and the low tolerance of the liver for this modality. Stereotactic body radiation therapy (SBRT) was recently developed and represents the most advanced radiation therapy technique currently available. It can deliver a high dose in a short time to well-defined hepatic tumors, with rapid dose fall-off gradients. We believe that SBRT with transarterial chemolipiodolization (TACL) may prove promising as a combined treatment modality for HCC due to its precision and relative safety. Here we present a case of successful treatment of advanced HCC with obstructive jaundice using this combined modality
Isolated Double-Chambered Right Ventricle in a Young Adult
Double-chambered right ventricle (DCRV) is a rare congenital heart disorder in which the right ventricle is divided by an anomalous muscle bundle into a high pressure inlet portion and a low pressure outlet portion. We report a case of isolated DCRV without symptoms in adulthood, diagnosed through echocardiography, cardiac catheterization and cardiac magnetic resonance imaging
Augmenting Adaptive Approach to Control of Flexible Systems
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77087/1/AIAA-2441-416.pd
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