1,721,957 research outputs found
Leo V. Ryan
No full textMarquette University alumnus Leo V. Ryan '49, who received the Distinguished Alumnus Award from Marquette's College of Business Administration in 1974
Dr. Leo V Josh Commencement
No full textFr. Reinert, Dr. Leo V Josh (Prof Emeritus) and Fr. Harrington Commencement 196
Leo V. Lehman, Lucas County, Ohio, 1969
No full textTerms associated with the photograph are: Lucas County Sheriffs Department | portrait | sergeant | Lehman, Leo V
Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V
Full text linkWe present a chemodynamical analysis of the Leo V dwarf galaxy, based on Keck II DEIMOS spectra of 8 member stars. We find a systemic velocity for the system of hvr i = 170.9 +2.1 −1.9 km s−1 , and barely resolve a velocity dispersion for the system, with σvr = 2.3 +3.2 −1.6 km s−1 , consistent with previous studies of Leo V. The poorly resolved dispersion means we are unable to adequately constrain the dark matter content of Leo V. We find an average metallicity for the dwarf of [Fe/H]= −2.48 ± 0.21, and measure a significant spread in the iron abundance of its member stars, with −3.1 ≤[Fe/H]≤ −1.9 dex, which cleanly identifies Leo V as a dwarf galaxy that has been able to self-enrich its stellar population through extended star formation. Owing to the tentative photometric evidence for tidal substructure around Leo V, we also investigate whether there is any evidence for tidal stripping or shocking of the system within its dynamics. We measure a significant velocity gradient across the system, of dv dχ = −4.1 +2.8 −2.6 km s−1 per arcmin (or dv dχ = −71.9 +50.8 −45.6 km s−1 kpc−1 ), which points almost directly toward the Galactic centre. We argue that Leo V is likely a dwarf on the brink of dissolution, having just barely survived a past encounter with the centre of the Milky Way
Preliminary results of a hover capable AUV attempting transitional flight
No full textThe actuators of an over-actuated AUV have been modeled and this information used to design a control algorithm that enables an vehicle to operate throughout a wide range of forward velocities. Both experimental and simulation results are presented for the performance of the through-body vertical tunnel thrusters, four independent control surfaces, and the interaction between the vehicle hull and actuators. The control algorithm has been tested and shown to work adequately well provided the vehicle acceleration is constraine
Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V
No full textWe present a chemodynamical analysis of the Leo V dwarf galaxy, based on the Keck II DEIMOS spectra of eight member stars. We find a systemic velocity for the system of nu(r) = 170.9(+2.1) (-1.9) km s(-1) and barely resolve a velocity dispersion for the system, with sigma nu(r) = 2.3(+3.2) (-1.6) km s(-1), consistent with previous studies of Leo V. The poorly resolved dispersion means we are unable to adequately constrain the dark-matter content of Leo V. We find an average metallicity for the dwarf of [ Fe/ H] =-2.48 +/- 0.21 and measure a significant spread in the iron abundance of its member stars, with -3.1 <= [ Fe/ H] <=-1.9 dex, which clearly identifies Leo V as a dwarf galaxy that has been able to self-enrich its stellar population through extended star formation. Owing to the tentative photometric evidence for the tidal substructure around Leo V, we also investigate whether there is any evidence for tidal stripping or shocking of the system within its dynamics. We measure a significant velocity gradient across the system, of dv d chi = -4.1(+2.8) (-2.6) km s(-1) arcmin(-1) ( or d nu/d chi=-71.9(vertical bar 50.8) (-45.6) km s(-1) kpc(-1)), which points almost directly towards the Galactic Centre. We argue that Leo V is likely a dwarf on the brink of dissolution, having just barely survived a past encounter with the centre of the Milky Way.European Research Council [ERCStG-335936]; NASA through Hubble Fellowship [51337]; Space Telescope Science Institute [NAS 5-26555, 51316.01]; NSF [AST-1412504, AST-1517649, PHY-1066293, AST-1514763, AST-1151462]; Packard FellowshipThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Experimentally verified model predictive control of a hover-capable AUV
No full textThis work presents the development of control systems that enable a hover-capable AUV to operate throughout a wide speed range. The Delphin2 AUV was built as part of this project and is used to experimentally verify the prototype control systems. This vehicle is over-actuated with; four through-body tunnel thrusters, four independently-actuated control surfaces and a rear propeller. The large actuator set allows the Delphin2 to operate at low speeds, using the through-body tunnel thrusters, and at high speeds, using the rear propeller and control surfaces. There lies a region between slow and high speed where neither the control surfaces nor tunnel thrusters are operating optimally. To maintain depth stability, both actuator sets are required to operate simultaneously. The model predictive control (MPC) algorithm is used to control the vehicle given its ability to handle multiple inputs and outputs along with system uncertainties. The basis of MPC is a mathematical model of the system to be controlled. Several experiments were conducted with the Delphin2 AUV to acquire the data necessary to develop this model. Bollard pull tests were used to measure thruster performance whilst wind-tunnel and open water experiments provided a measure of the control surfaces, hull and propeller performance. Depth control is the primary focus of this Thesis, however, pitch and surge control are also addressed. Three controllers are developed in this work, of increasing complexity; a depth and pitch controller for low speed operations, a depth and surge velocity controller for medium to high speed operation, and finally, a depth and surge velocity controller for operation from low to high speed operations. All three controllers are multi-input multi-output (MIMO) and use the MPC algorithm. Input constraints are imposed on both the absolute limits and the rate of change limits. Simulations re performed to aid in the design of each controller before it is implemented on the Delphin2 AUV and experimentally verified. The depth and pitch controller, developed for low speed operation, uses the front and rear vertical thrusters as the system inputs. This case demonstrates the implementation of the MPC algorithm and studies the effects of the various tuning parameters. A model sensitivity study is performed, showing that the controller can handle modelling errors of up to ~30%. The controller is experimentally tested and shows excellent performance with zero steady-state errors although there is an undesirably large overshoot of the depth demand. The simulation and experimental results match closely. The depth and surge controller uses the control surfaces and rear propeller as system inputs. Many of the forces and moments within this system are non-linear functions of the vehicles surge velocity. Therefore the standard MPC algorithm, that utilizes just one linearised model, would not be sufficient to capture the system dynamics of the vehicle throughout the full operational envelope. A time-variant MPC (TV-MPC) algorithm is developed and shown in simulation to have excellent performance. The controller did not perform as well when tested experimentally, however, depth regulation of ~0:3 m was achieved. This degradation in performance is due to inaccuracies in the estimation of the vehicles surge velocity. The final controller is also a depth and surge velocity controller, however, it is tasked with maintaining stability through-out the full speed range of the vehicle. All of the system inputs used for depth control are utilised by this controller; the two vertical through-body tunnel thrusters, horizontal control surfaces and the rear propeller. The design of the controller makes use of the TV MPC algorithm. To improve system performance a modification to the controllers cost function, used within the optimisation process, was made to penalise the use of the thrusters at high speeds. This enables the controller to use the thrusters at low speeds, when performing close range inspections, but then as surge velocity increases and the thrusters are no longer required, they are switched off. Both simulation and experimental results show excellent performance, although when the thrusters switch off, the depth control is similar to that of the previous controller due to poor surge velocity estimation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Leo V. Card, left, and J. E. McDonald, right. Miss Charee Moyse is on the scales
No full textLeo V. Card, left, and J. E. McDonald, right. Miss Charee Moyse is on the scales.https://mavmatrix.uta.edu/specialcollections_startelegram1940s/14559/thumbnail.jp
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