170,198 research outputs found
Cuban independence [music] : march and two step /
No full textFor piano.; Also available online http://nla.gov.au/nla.mus-an12022054
Alberta Stroke Program Early CT Score Infarct Location Predicts Outcome Following M2 Occlusion
No full textCo-author Nils Henninger is a doctoral student in the Millennium PhD Program (MPP) in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.BACKGROUND: Although it is generally thought that patients with distal middle cerebral artery (M2) occlusion have a favorable outcome, it has previously been demonstrated that a substantial minority will have a poor outcome by 90 days. We sought to determine whether assessing the Alberta Stroke Program Early CT Score (ASPECTS) infarct location allows for identifying patients at risk for a poor 90-day outcome. METHODS: We retrospectively analyzed patients with isolated acute M2 occlusion admitted to a single academic center between January 2010 and August 2012. Infarct regions were defined according to ASPECTS system on the initial head computed tomography. Discriminant function analysis was used to define specific ASPECTS regions that are predictive of the 90-day functional outcome as defined as a modified Rankin Scale score of 3-6. In addition, logistic regression was used to model the relationship between each individual ASPECT region with poor outcome; for evaluation and comparison, odds ratios, c-statistics, and Akaike information criterion values were estimated for each region. RESULTS: Ninety patients with isolated M2 were included in the final analysis. ASPECTS score CONCLUSION: Infarction in ASPECTS regions M3 and M6 are key predictors of functional outcome following isolated distal M2 occlusion. These findings will be helpful in stratifying outcomes if validated in future studies.Millennium Ph
Semi-Analytic motion planning with actuator constraints on 3-D Lie groups
No full textThis paper describes a global motion planning method for vehicles with actuator constraints based on the semi-Analytic solution of minimum energy-Type curves on the frame bundle of connected surfaces of arbitrary cross sectional curvature. The method is semi-Analytic and solves the boundary-value problem arising from the geometric framing of the Pontryagin's maximum principle applied to the vehicle kinematics where the velocities are defined analytically in terms of three parameters. Numerical shooting on an iterative Lie group expression of the curve in the group is then employed to match the group boundary conditions. This approach has the advantage that an analytic description of the control accelerations can be derived and enables actuator constraints to be incorporated via time reparametrization. The method is applied to a practical example from space mechanics, the spacecraft docking problem with actuator constraints
Enhancing Station-Keeping Control With the Use of Extended State Observers
No full textRecently there has been a resurgence of interest in missions to the moon and a major challenge of such missions is to provide a continuous communication between the Earth and the Moon’s far side. Orbits around the L2 Earth-Moon Lagrange point have been a topic of interest in this field due to their potential for constant communication with both the Earth and the Moon, however the Lagrange point orbits are innately unstable and so station-keeping control is required to maintain them. Station-keeping problems are highly nonlinear and a traditional approach to control design is first to linearize the nonlinear system. However, this first-order approximation introduces errors if there are large injection errors. This paper demonstrates how a simple Extended State Observer (ESO) can be used to improve the convergence time of spacecraft to the reference orbit given with large injection errors. Additionally, solar radiation pressure (SRP) a dominant disturbance in deep-space, can lead to inefficient station-keeping if it is not taken into account in the reference orbit design. New reference orbits can be designed that exploit the SRP perturbation but this assumes that it is known apriori. Here we show how an ESO could provide an in-orbit measurement of the SRP which could be used to modify the reference trajectory to a more fuel efficient one. Finally, it is shown how an ESO can be used to estimate, not only the disturbance, but simultaneously the velocity of the spacecraft meaning that only the position of the spacecraft is required
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John Henninger Reagan
No full textThis study of the life of John Henninger Reagan covers the period from his birth, 1818 to his appointment by Governor James S. Hogg to the Chairmanship of the Texas Railroad Commission in 1891. Reagan came to Texas in May 1839, serving in the Cherokee War of that year. For two years, 1840-1842 he was surveyor of Nacogdoches County. He began the study of law in 1844, and was admitted to the bar in 1846. Reagan was member of the Second Legislature, 1847-1848. He continued the practice of law until his election as Judge of the Ninth Judicial District in 1852. He resigned the judgeship to enter Congress in 1857, serving until the outbreak of the War in 1861. He was a member of the Secession Convention and was chosen a member of the Confederate Congress. President Jefferson Davis appointed him Postmaster-General of the Confederacy which portfolio he held till the close of the War. His political disabilities having been removed in 1874 he reentered Congress in that year serving until his election to the United States Senate in 1887. At the request of Governor Hogg he accepted the chairmanship of the Railroad Commission which he held until his retirement in 1903. He died at Palestine Texas, March 1905. Work on the period from 1891 until his death in 1905 is in progressHistor
Rupture propagation and radiation : comparisons between interface constitutive laws including damage and friction
No full textTrajectory generation and tracking on SE(3) for an underactuated AUV with disturbances
No full textThis paper describes the trajectory tracking of an underactuated autonomous underwater vehicle (AUV) with three control inputs (surge, yaw and pitch moment) that operates in the presence of time-varying disturbances. The AUV kinematics are described in global coordinates as a Hamiltonian system on the Lie group SE(3) and the boundary-value problem arising from the geometric framing of Pontryagin's Maximum Principle is applied to the vehicle kinematics. This 6-dimensional boundary value problem is solved using a numerical shooting method and a novel semi-analytical Lie group integrator. The integrator uses Rodrigue's formula to express the exact solution of the solution curves, is symplectic and preserves energy and momentum. Inverse dynamics is applied to construct an inner-loop controller, which accounts for constraints on maximum torque and force via time reparametrization. This inner-loop control, which would drive the AUV along the reference trajectory in perfect conditions, is combined with a disturbance observer to construct an outer-loop controller, which ensures stability in the presence of bounded disturbances. Simulation results complete the work
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Shared human-robot path following control of an unmanned ground vehicle
No full textThis paper considers the shared path following control of an unmanned ground vehicle by a single person. A passive measure of human intent is used to blend the human and machine inputs in a mixed initiative approach. The blending law is combined with saturated super-twisting sliding mode speed and heading controllers, so that exogenous disturbances can be counteracted via equivalent control. It is proven that when the proposed blending law is used, the combined control signals from both the human and automatic controller respect the actuator magnitude constraints of the machine. To demonstrate the approach, shared control experiments are performed using an unmanned ground vehicle, which follows a lawn mower pattern shaped path
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