436 research outputs found
Resource-constrained FPGA Design for Satellite Component Feature Extraction
The effective use of computer vision and machine learning for on-orbit
applications has been hampered by limited computing capabilities, and therefore
limited performance. While embedded systems utilizing ARM processors have been
shown to meet acceptable but low performance standards, the recent availability
of larger space-grade field programmable gate arrays (FPGAs) show potential to
exceed the performance of microcomputer systems. This work proposes use of
neural network-based object detection algorithm that can be deployed on a
comparably resource-constrained FPGA to automatically detect components of
non-cooperative, satellites on orbit. Hardware-in-the-loop experiments were
performed on the ORION Maneuver Kinematics Simulator at Florida Tech to compare
the performance of the new model deployed on a small, resource-constrained FPGA
to an equivalent algorithm on a microcomputer system. Results show the FPGA
implementation increases the throughput and decreases latency while maintaining
comparable accuracy. These findings suggest future missions should consider
deploying computer vision algorithms on space-grade FPGAs.Comment: 9 pages, 7 figures, 4 tables, Accepted at IEEE Aerospace Conference
202
Autonomous Rendezvous with Non-cooperative Target Objects with Swarm Chasers and Observers
Space debris is on the rise due to the increasing demand for spacecraft for
com-munication, navigation, and other applications. The Space Surveillance
Network (SSN) tracks over 27,000 large pieces of debris and estimates the
number of small, un-trackable fragments at over 1,00,000. To control the growth
of debris, the for-mation of further debris must be reduced. Some solutions
include deorbiting larger non-cooperative resident space objects (RSOs) or
servicing satellites in or-bit. Both require rendezvous with RSOs, and the
scale of the problem calls for autonomous missions. This paper introduces the
Multipurpose Autonomous Ren-dezvous Vision-Integrated Navigation system
(MARVIN) developed and tested at the ORION Facility at Florida Institution of
Technology. MARVIN consists of two sub-systems: a machine vision-aided
navigation system and an artificial po-tential field (APF) guidance algorithm
which work together to command a swarm of chasers to safely rendezvous with the
RSO. We present the MARVIN architec-ture and hardware-in-the-loop experiments
demonstrating autonomous, collabo-rative swarm satellite operations
successfully guiding three drones to rendezvous with a physical mockup of a
non-cooperative satellite in motion.Comment: Presented at AAS/AIAA Spaceflight Mechanics Meeting 2023, 17 pages, 9
figures, 3 table
Performance Study of YOLOv5 and Faster R-CNN for Autonomous Navigation around Non-Cooperative Targets
Autonomous navigation and path-planning around non-cooperative space objects
is an enabling technology for on-orbit servicing and space debris removal
systems. The navigation task includes the determination of target object
motion, the identification of target object features suitable for grasping, and
the identification of collision hazards and other keep-out zones. Given this
knowledge, chaser spacecraft can be guided towards capture locations without
damaging the target object or without unduly the operations of a servicing
target by covering up solar arrays or communication antennas. One way to
autonomously achieve target identification, characterization and feature
recognition is by use of artificial intelligence algorithms. This paper
discusses how the combination of cameras and machine learning algorithms can
achieve the relative navigation task. The performance of two deep
learning-based object detection algorithms, Faster Region-based Convolutional
Neural Networks (R-CNN) and You Only Look Once (YOLOv5), is tested using
experimental data obtained in formation flight simulations in the ORION Lab at
Florida Institute of Technology. The simulation scenarios vary the yaw motion
of the target object, the chaser approach trajectory, and the lighting
conditions in order to test the algorithms in a wide range of realistic and
performance limiting situations. The data analyzed include the mean average
precision metrics in order to compare the performance of the object detectors.
The paper discusses the path to implementing the feature recognition algorithms
and towards integrating them into the spacecraft Guidance Navigation and
Control system.Comment: 12 pages, 10 figures, 9 tables, IEEE Aerospace Conference 202
The remote monad design pattern
Remote Procedure Calls are expensive. This paper demonstrates how to reduce the cost of calling remote procedures from Haskell by using the remote monad design pattern, which amortizes the cost of remote calls. This gives the Haskell community access to remote capabilities that are not directly supported, at a surprisingly
inexpensive cost.
We explore the remote monad design pattern through six models of remote execution patterns, using a simulated Internet of Things toaster as a running example. We consider the expressiveness and optimizations enabled by each remote execution model, and assess the feasibility of our approach. We then present a full-scale case
study: a Haskell library that provides a Foreign Function Interface to the JavaScript Canvas API. Finally, we discuss existing instances of the remote monad design pattern found in Haskell libraries
Characterisation of CART-containing neurons and cells in the porcine pancreas, gastro-intestinal tract, adrenal and thyroid glands
<p>Abstract</p> <p>Background</p> <p>The peptide CART is widely expressed in central and peripheral neurons, as well as in endocrine cells. Known peripheral sites of expression include the gastrointestinal (GI) tract, the pancreas, and the adrenal glands. In rodent pancreas CART is expressed both in islet endocrine cells and in nerve fibers, some of which innervate the islets. Recent data show that CART is a regulator of islet hormone secretion, and that CART null mutant mice have islet dysfunction. CART also effects GI motility, mainly via central routes. In addition, CART participates in the regulation of the hypothalamus-pituitary-adrenal-axis. We investigated CART expression in porcine pancreas, GI-tract, adrenal glands, and thyroid gland using immunocytochemistry.</p> <p>Results</p> <p>CART immunoreactive (IR) nerve cell bodies and fibers were numerous in pancreatic and enteric ganglia. The majority of these were also VIP IR. The finding of intrinsic CART containing neurons indicates that pancreatic and GI CART IR nerve fibers have an intrinsic origin. No CART IR endocrine cells were detected in the pancreas or in the GI tract. The adrenal medulla harboured numerous CART IR endocrine cells, most of which were adrenaline producing. In addition CART IR fibers were frequently seen in the adrenal cortex and capsule. The capsule also contained CART IR nerve cell bodies. The majority of the adrenal CART IR neuronal elements were also VIP IR. CART IR was also seen in a substantial proportion of the C-cells in the thyroid gland. The majority of these cells were also somatostatin IR, and/or 5-HT IR, and/or VIP IR.</p> <p>Conclusion</p> <p>CART is a major neuropeptide in intrinsic neurons of the porcine GI-tract and pancreas, a major constituent of adrenaline producing adrenomedullary cells, and a novel peptide of the thyroid C-cells. CART is suggested to be a regulatory peptide in the porcine pancreas, GI-tract, adrenal gland and thyroid.</p
Botulinum toxin in gastric submucosa reduces stimulated HCl production in rats
BACKGROUND: Botulinum toxin blocks acetylcholine release from nerve endings and acts as a long term, reversible inhibitor of muscle contraction as well as of salivary, sweat gland, adrenal and prostatic secretions. The aim of the present study is to investigate whether gastric submucosal injection of botulinum toxin type A reduces stimulated gastric production of HCl. METHODS: Sixty-four rats were randomized in two groups and laparotomized. One group was treated with botulinum toxin-A 10 U by multiple submucosal gastric injections, while the second group was injected with saline. Two weeks later, acid secretion was stimulated by pyloric ligation and acid output was measured. Body weight, food and water intake were also recorded daily. RESULTS: HCl production after pyloric ligation was found to be significantly lower in botulinum toxin-treated rats (657 ± 90.25 micromol HCl vs. 1247 ± 152. P = 0.0017). Botulinum toxin-treated rats also showed significantly lower food intake and weight gain. CONCLUSIONS: Botulinum toxin type A reduces stimulated gastric acidity. This is likely due either to inhibition of the cholinergic stimulation of gastric parietal cells, or to an action on the myenteric nervous plexuses. Reduction of growth and food intake may reflect both impaired digestion and decreased gastric motility
Labour-market marginalisation after mental disorders among young natives and immigrants living in Sweden
Intimal Hyperplasia in Balloon Dilated Coronary Arteries is Reduced by Local Delivery of the NO Donor, SIN-1 Via a cGMP-Dependent Pathway
<p>Abstract</p> <p>Background</p> <p>To elucidate the mechanism by which local delivery of 3-morpholino-sydnonimine (SIN-1) affects intimal hyperplasia after percutaneous transluminal coronary angioplasty (PTCA).</p> <p>Methods</p> <p>Porcine coronary arteries were treated with PTCA and immediately afterwards locally treated for 5 minutes, with a selective cytosolic guanylate cyclase inhibitor, 1 H-(1,2,4)oxadiazole(4,3-alpha)quinoxaline-1-one (ODQ) + SIN-1 or only SIN-1 using a drug delivery-balloon. Arteries were angiographically depicted, morphologically evaluated and analyzed after one and eight weeks for actin, myosin and intermediate filaments (IF) and nitric oxide synthase (NOS) contents.</p> <p>Results</p> <p>Luminal diameter after PCI in arteries treated with SIN-1 alone and corrected for age-growth was significantly larger as compared to ODQ + SIN-1 or to controls (p < 0.01). IF/actin ratio after one week in SIN-1 treated segments was not different compared to untreated segments, but was significantly reduced compared to ODQ + SIN-1 treated vessels (p < 0.05). Expression of endothelial NADPH diaphorase activity was significantly lower in untreated segments and in SIN-1 treated segments compared to controls and SIN-1 + ODQ treated arteries (p < 0.01). Restenosis index (p < 0.01) and intimal hyperplasia (p < 0.01) were significantly reduced while the residual lumen was increased (p < 0.01) in SIN-1 segments compared to controls and ODQ + SIN-1 treated vessels.</p> <p>Conclusions</p> <p>After PTCA local delivery of high concentrations of the NO donor SIN-1 for 5 minutes inhibited injury induced neointimal hyperplasia. This favorable effect was abolished by inhibition of guanylyl cyclase indicating mediation of a cyclic guanosine 3',5'-monophosphate (cGMP)-dependent pathway. The momentary events at the time of injury play crucial role in the ensuring development of intimal hyperplasia.</p
Somatostatin, substance P and calcitonin gene-related peptide-positive intramural nerve structures of the human large intestine affected by carcinoma.
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