Swashplate feedback control for tilt-rotor aircraft

Changes in angle of attack in system were sensed indirectly by gages which responded to strains induced in wing structure. Output signals were amplified, filtered, and used to activate swashplate actuators. System provided significant reduction in blade loads and desirable changes in hub forces and moments

Time-asymptotic solutions of the Navier-Stokes equation for free shear flows using an alternating-direction implicit method

An uncoupled time asymptotic alternating direction implicit method for solving the Navier-Stokes equations was tested on two laminar parallel mixing flows. A constant total temperature was assumed in order to eliminate the need to solve the full energy equation; consequently, static temperature was evaluated by using algebraic relationship. For the mixing of two supersonic streams at a Reynolds number of 1,000, convergent solutions were obtained for a time step 5 times the maximum allowable size for an explicit method. The solution diverged for a time step 10 times the explicit limit. Improved convergence was obtained when upwind differencing was used for convective terms. Larger time steps were not possible with either upwind differencing or the diagonally dominant scheme. Artificial viscosity was added to the continuity equation in order to eliminate divergence for the mixing of a subsonic stream with a supersonic stream at a Reynolds number of 1,000

Local sensory control of a dexterous end effector

A numerical scheme was developed to solve the inverse kinematics for a user-defined manipulator. The scheme was based on a nonlinear least-squares technique which determines the joint variables by minimizing the difference between the target end effector pose and the actual end effector pose. The scheme was adapted to a dexterous hand in which the joints are either prismatic or revolute and the fingers are considered open kinematic chains. Feasible solutions were obtained using a three-fingered dexterous hand. An algorithm to estimate the position and orientation of a pre-grasped object was also developed. The algorithm was based on triangulation using an ideal sensor and a spherical object model. By choosing the object to be a sphere, only the position of the object frame was important. Based on these simplifications, a minimum of three sensors are needed to find the position of a sphere. A two dimensional example to determine the position of a circle coordinate frame using a two-fingered dexterous hand was presented

Surface enhancement of oxygen exchange and diffusion in the ionic conductor La2Mo2O9

Isotopic surface oxygen exchange and its subsequent diffusion have been measured using secondary ion mass spectrometry in the fast ionic conductor La2Mo2O9. A silver coating was applied to the sample surface to enhance the surface exchange process for dry oxygen. Contrary to previous studies performed using a wet atmosphere, no grain boundary diffusion tail was observed under these optimized dry exchange conditions. The activation energy for oxygen diffusion was found to be 0.66(+/- 0.09) eV at high temperature (>570 degrees C), and 1.25(+/- 0.01)eV at low temperature (<570 degrees C). Time-of-Flight secondary ion mass spectrometry was employed to investigate the correlation between the silver coating and the O-18 concentration on the sample surface. A close correlation between the presence of silver and oxygen incorporation on the surface was observed. (C) 2010 Elsevier B.V. All rights reserved

Wave Profile for Current Bearing Antiforce Waves

For fluid dynamical analysis of breakdown waves, we employ a one-dimensional, three-component (electrons, ions and neutral particles) fluid model to describe a steady-state, ionizing wave propagating counter to strong electric fields. The electron gas temperature and therefore the electron fluid pressure is assumed to be large enough to sustain the wave motion down the discharge tube. Such waves are referred to as antiforce waves. The complete set of equations describing such waves consists of the equations of conservation of mass, momentum and energy coupled with Poisson’s equation. Inclusion of current behind the wave front alters the set of electron fluid dynamical equations and also the boundary condition on electron temperature. For a range of experimentally observed current values, using the modified boundary condition on electron temperature, we have been able to integrate our modified set of electron fluid dynamical equations through the Debye layer. Our solutions meet the expected boundary conditions at the trailing edge of the wave. We present the wave profile for electric field, electron velocity, electron number density and electron temperature within the Debye layer of the wave

Ion yields and erosion rates for Si1−xGex(0x1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25–1 keV

We report the SIMS parameters required for the quantitative analysis of Si1−xGex across the range of 0 ≤ x ≤ 1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1−xGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1−x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x

A simulator study of the supersonic transport in the air traffic control system

Real time environment and control simulation of supersonic transport in air traffic control syste

Tracking daily fatigue fluctuations in multiple sclerosis : ecological momentary assessment provides unique insights

The preparation of this manuscript was supported by a UK Economic and Social Research Council (ESRC) PhD studentship (ES/1026266/1) awarded to DP. The study was funded by the Psychology Unit at the University of Southampton. The authors declare that they have no conflict of interest. The authors thank all participants of this study. Open access via Springer Compact Agreement.Peer reviewedPublisher PD