5,993 research outputs found
Clinical ophthalmic ultrasound improvements
The use of digital synthetic aperture techniques to obtain high resolution ultrasound images of eye and orbit was proposed. The parameters of the switched array configuration to reduce data collection time to a few milliseconds to avoid eye motion problems in the eye itself were established. An assessment of the effects of eye motion on the performance of the system was obtained. The principles of synthetic techniques are discussed. Likely applications are considered
Telecommunications system design for the Mariner Mars 1971 spacecraft
The configuration of the Mariner Mars 1971 spacecraft telecommunications system is detailed, with particular attention to modifications performed to accommodate the orbital mission. The analysis and planning for launching are also discussed
Riccati parameter modes from Newtonian free damping motion by supersymmetry
We determine the class of damped modes \tilde{y} which are related to the
common free damping modes y by supersymmetry. They are obtained by employing
the factorization of Newton's differential equation of motion for the free
damped oscillator by means of the general solution of the corresponding Riccati
equation together with Witten's method of constructing the supersymmetric
partner operator. This procedure leads to one-parameter families of (transient)
modes for each of the three types of free damping, corresponding to a
particular type of %time-dependent angular frequency. %time-dependent,
antirestoring acceleration (adding up to the usual Hooke restoring
acceleration) of the form a(t)=\frac{2\gamma ^2}{(\gamma t+1)^{2}}\tilde{y},
where \gamma is the family parameter that has been chosen as the inverse of the
Riccati integration constant. In supersymmetric terms, they represent all those
one Riccati parameter damping modes having the same Newtonian free damping
partner modeComment: 6 pages, twocolumn, 6 figures, only first 3 publishe
A High-Fidelity Realization of the Euclid Code Comparison -body Simulation with Abacus
We present a high-fidelity realization of the cosmological -body
simulation from the Schneider et al. (2016) code comparison project. The
simulation was performed with our Abacus -body code, which offers high force
accuracy, high performance, and minimal particle integration errors. The
simulation consists of particles in a box,
for a particle mass of with $10\
h^{-1}\mathrm{kpc}z=0<0.3\%k<10\
\mathrm{Mpc}^{-1}h0.01\%$. Simulation snapshots are available at
http://nbody.rc.fas.harvard.edu/public/S2016 .Comment: 13 pages, 8 figures. Minor changes to match MNRAS accepted versio
Closed-Loop Control of Constrained Flapping Wing Micro Air Vehicles
Micro air vehicles are vehicles with a maximum dimension of 15 cm or less, so they are ideal in confined spaces such as indoors, urban canyons, and caves. Considerable research has been invested in the areas of unsteady and low Reynolds number aerodynamics, as well as techniques to fabricate small scale prototypes. Control of these vehicles has been less studied, and most control techniques proposed have only been implemented within simulations without concern for power requirements, sensors and observers, or actual hardware demonstrations. In this work, power requirements while using a piezo-driven, resonant flapping wing control scheme, Bi-harmonic Amplitude and Bias Modulation, were studied. In addition, the power efficiency versus flapping frequency was studied and shown to be maximized while flapping at the piezo-driven system\u27s resonance. Then prototype hardware of varying designs was used to capture the impact of a specific component of the flapping wing micro air vehicle, the passive rotation joint. Finally, closed-loop control of different constrained configurations was demonstrated using the resonant flapping Bi-harmonic Amplitude and Bias Modulation scheme with the optimized hardware. This work is important in the development and understanding of eventual free-flight capable flapping wing micro air vehicle
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