Experimental Study of Spacecraft Pose Estimation Algorithm Using

This paper presents a vision-based relative pose estimation algorithm and its validation through both numerical and hardware experiments. The algorithm and the hardware system were simultaneously designed considering actual experimental conditions. Two estimation techniques were utilized to estimate relative pose; one was a nonlinear least square method for initial estimation, and the other was an extended Kalman Filter for subsequent on-line estimation. A measurement model of the vision sensor and equations of motion including nonlinear perturbations were utilized in the estimation process. Numerical simulations were performed and analyzed for both the autonomous docking and formation flying scenarios. A configuration of LED-based beacons was designed to avoid measurement singularity, and its structural information was implemented in the estimation algorithm. The proposed algorithm was verified again in the experimental environment by using the Autonomous Spacecraft Test Environment for Rendezvous In proXimity (ASTERIX) facility. Additionally, a laser distance meter was added to the estimation algorithm to improve the relative position estimation accuracy. Throughout this study, the performance required for autonomous docking could be presented by confirming the change in estimation accuracy with respect to the level of measurement error. In addition, hardware experiments confirmed the effectiveness of the suggested algorithm and its applicability to actual tasks in the real world

Achieving Both Ultrahigh Electrical Conductivity and Mechanical Modulus of Carbon Films: Templating-Coalescing Behavior of Single-Walled Carbon Nanotube in Polyacrylonitrile

Promoting the feasibility of carbon films as electrode applications requires sufficient performances in view of both electrical and mechanical properties. Herein, carbon films with ultrahigh electrical conductivity and mechanical modulus are prepared by high temperature carbonization of polyacrylonitrile (PAN)/single-walled carbon nanotube (SWNT) nanocomposites. Achieving both performances is ascribed to remarkable graphitic crystallinity, resulting from the sequential templating???coalescing behavior of concentrated SWNT bundles (B-CNTs). While well-dispersed SWNTs (WD-CNTs) facilitate radial templating according to their tubular geometry, flattened B-CNTs sandwiched between carbonized PAN matrices induce vertical templating, where the former and latter produce concentric and planar crystallizations of the graphitic structure, respectively. After carbonization at 2500 ??C with the remaining WD-CNTs as microstructural defects, the flattened B-CNTs coalesce into graphitic crystals by zipping the surrounding matrix, resulting in high crystallinity with the crystal thicknesses of 27.4 and 39.4 nm for the (002) and (10) planes, respectively. For comparison, the graphene oxide (GO) containing carbon films produce a less-ordered graphitic phase owing to irregular templating, despite the geometrical consistency. Consequently, PAN/B-CNT carbon films exhibit exceptional electrical conductivity (40.7 ?? 104 S m???1) and mechanical modulus (38.2 ?? 6.4 GPa). Thus, controlling the templating???coalescing behavior of SWNTs is the key for improving final performances of carbon films

The CUAVA-2 CubeSat: A Second Attempt to Fly the Remote Sensing, Space Weather Study and Earth Observation Instruments

This paper presents the 6U CubeSat mission conducted by the ARC Training Centre for CubeSats, UAVs, and their Applications (CUAVA) at the University of Sydney. CUAVA-2, the second CubeSat project following the CUAVA-1 mission, builds upon lessons learned from its predecessor. CUAVA-1, the first satellite launched by CUAVA, carried first-generation payloads for earth observation goals and technology demonstrations but experienced communication difficulties. A fault root analysis was performed on CUAVA-1 to inform the design of CUAVA-2. The CUAVA-2 satellite incorporates a hyperspectral imager for applications in agriculture, forestry, coastal and marine environments, urban areas, water hazard assessment, and mineral exploration. It also includes a GPS reflectometry payload for remote sea state determination, as well as secondary payloads for technology demonstration and space weather study. This paper discusses the fault analysis findings, lessons learned, and design inputs from CUAVA-1, showcasing their integration into the CUAVA-2 satellite, which is scheduled for launch in February 2024

The CUAVA-1 CubeSat—A Pathfinder Satellite for Remote Sensing and Earth Observation

In this paper we report a 3U CubeSat named CUAVA-1 designed by the ARC Training Centre for CubeSats, UAVs, and Their Applications (CUAVA). CUAVA, funded by the Australian Research Council, aims to train students, develop new instruments and technology to solve crucial problems, and help develop a world-class Australian industry in CubeSats, UAVs, and related products. The CUAVA-1 project is the Centre’s first CubeSat mission, following on from the 2 Australian satellites INSPIRE-2 and UNSW-EC0 CubeSats that launched in 2017. The mission is designed to serve as a precursor for a series of Earth observations missions and to demonstrate new technologies developed by our partners. We also intend to use the satellite to provide students hands-on experiences and to gain experience for our engineering, science and industry teams for future, more complex, missions

Global, regional, and national burden of neurological disorders, 1990–2016 : a systematic analysis for the Global Burden of Disease Study 2016

Background: Neurological disorders are increasingly recognised as major causes of death and disability worldwide. The aim of this analysis from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 is to provide the most comprehensive and up-to-date estimates of the global, regional, and national burden from neurological disorders. Methods: We estimated prevalence, incidence, deaths, and disability-adjusted life-years (DALYs; the sum of years of life lost [YLLs] and years lived with disability [YLDs]) by age and sex for 15 neurological disorder categories (tetanus, meningitis, encephalitis, stroke, brain and other CNS cancers, traumatic brain injury, spinal cord injury, Alzheimer's disease and other dementias, Parkinson's disease, multiple sclerosis, motor neuron diseases, idiopathic epilepsy, migraine, tension-type headache, and a residual category for other less common neurological disorders) in 195 countries from 1990 to 2016. DisMod-MR 2.1, a Bayesian meta-regression tool, was the main method of estimation of prevalence and incidence, and the Cause of Death Ensemble model (CODEm) was used for mortality estimation. We quantified the contribution of 84 risks and combinations of risk to the disease estimates for the 15 neurological disorder categories using the GBD comparative risk assessment approach. Findings: Globally, in 2016, neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9·0 million [8·8–9·4]). The absolute number of deaths and DALYs from all neurological disorders combined increased (deaths by 39% [34–44] and DALYs by 15% [9–21]) whereas their age-standardised rates decreased (deaths by 28% [26–30] and DALYs by 27% [24–31]) between 1990 and 2016. The only neurological disorders that had a decrease in rates and absolute numbers of deaths and DALYs were tetanus, meningitis, and encephalitis. The four largest contributors of neurological DALYs were stroke (42·2% [38·6–46·1]), migraine (16·3% [11·7–20·8]), Alzheimer's and other dementias (10·4% [9·0–12·1]), and meningitis (7·9% [6·6–10·4]). For the combined neurological disorders, age-standardised DALY rates were significantly higher in males than in females (male-to-female ratio 1·12 [1·05–1·20]), but migraine, multiple sclerosis, and tension-type headache were more common and caused more burden in females, with male-to-female ratios of less than 0·7. The 84 risks quantified in GBD explain less than 10% of neurological disorder DALY burdens, except stroke, for which 88·8% (86·5–90·9) of DALYs are attributable to risk factors, and to a lesser extent Alzheimer's disease and other dementias (22·3% [11·8–35·1] of DALYs are risk attributable) and idiopathic epilepsy (14·1% [10·8–17·5] of DALYs are risk attributable). Interpretation: Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders. The scarcity of established modifiable risks for most of the neurological burden demonstrates that new knowledge is required to develop effective prevention and treatment strategies. Funding: Bill & Melinda Gates Foundation

The effect of interfacial interaction on the conformational variation of poly(vinylidene fluoride) (PVDF) chains in PVDF/graphene oxide (GO) nano composite fibers and corresponding mechanical properties

Poly(vinylidene fluoride) (PVDF)/graphene oxide (GO) nanocomposite fibers were dry-jet wet spun at the GO concentrations of 0, 1, and 2 wt% with respect to the polymer. The as-spun fibers were drawn in the draw ratio (DR) range of 2 to 6.5, and the correlation between the PVDF chain conformation and the mechanical properties of the fibers upon drawing has been studied by 2D correlation spectroscopy (COS) of Fourier-transformed infrared (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and tensile testing. The PVDF/GO nanocomposite fibers exhibited that the mobile PVDF crystals due to the conformational defects and kinks were nucleated because of the polar interaction between PVDF chains and functional groups of GO, whereas the control PVDF fiber showed the conventional conversion of crystal polymorphs (??? and ??? phases to ??? phase). As a result, the nanocomposite fiber showed dramatically improved toughness (enhanced by 1123% at a DR of 2 and 120% at a DR of 6.5) as compared to that of the control fiber. Furthermore, the tensile strength and modulus of the PVDF/GO (2 wt%) fiber were 394 MPa and 4.6 GPa, respectively, while those of the control PVDF fiber were 295 MPa and 3.9 GPa