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

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

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

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

Relaxation of strained silicon on Si0.5Ge0.5 virtual substrates

Strain relaxation has been studied in tensile strained silicon layers grown on Si0.5Ge0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60° dislocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain

Study of the application of hydrogen fuel to long-range subsonic transport aircraft, volume 2

The feasibility, practicability, and potential advantages/disadvantages of using liquid hydrogen as fuel in long range, subsonic transport aircraft of advanced design were studied. Both passenger and cargo-type aircraft were investigated. To provide a valid basis for comparison, conventional hydrocarbon (Jet A) fueled aircraft were designed to perform identical missions using the same advanced technology and meeting the same operational constraints. The liquid hydrogen and Jet A fueled aircraft were compared on the basis of weight, size, energy utilization, cost, noise, emissions, safety, and operational characteristics. A program of technology development was formulated

Coal-shale interface detection system

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through

Optimisation studies on strain-engineered Germanium heterostructures

The physical gate lengths of state-of-the-art CMOS devices are 45 nm and are anticipated to reach just 20 nm by 2007. Due to the prohibitive capital expenditure required for next-generation CMOS technologies, leading device manufacturers are now exploring exotic device architectures and novel substrates in which significant device performance enhancements may by obtained using the existing device fabrication infrastructure. This thesis reports studies made on an initial evaluation of hole transport properties in strained Ge channels and comprises physical and electrical characterisation of these heterostructures as well as the analysis of SiGe layers using secondary ion mass spectrometry. The initial work of thesis describes the growth, characterisation and optimisation of a novel strained Ge substrate. The substrate technology was developed using a hybrid-epitaxy technique in which a SiGe strain-relaxed buffer layer, so called "virtual substrate", was grown using a ultra-high vacuum chemical-vapour deposition growth technique and the active strained Ge layer was grown using a solid-source molecular-beam epitaxy growth technology. An advanced chemical cleaning procedure has been developed which includes a modified Piranha etch. The novel cleaning procedure enables the successful integration of the two growth techniques. Significant hole carrier transport enhancements were observed for holes contained within the strained Ge channel. Optimisation of the hole mobility was achieved by the reduction of carrier scattering such as interface roughness scattering and point defect scattering. The optimisation methods employed included growth temperature iterations to reduce Ge channel roughening via elastic relaxation and, channel thickness iterations were also employed in order to minimize channel roughening and defect nucleation. Post-growth annealing procedures were used to combat defects arising from low temperature growth. The Ge heterostructures were grown on strain relaxed buffer layers, terminating with a Ge content of 60%. The optimised strained Ge channel thickness was found to be 20 nm and the growth temperature of the active layers was reduced to 350°C so as to minimise surface roughening. As grown point defects were eliminated at an optimised post-growth anneal temperature of 650°C for 30 minutes under dry N2• Hall mobilities reached 1910 cm2Ns at room temperature rising to 26,900 cm2Ns at 10K. A magneto-conductivity transfonnation measurement and maximum entropy mobility spectrum analysis revealed a room temperature drift mobility of 2700 cm2Ns at a carrier density of l.Ox1012 cm-2 . This result represents a 15-fo1d increase in hole mobility compared to conventional Si substrates at comparable effective fields. The second and important part of this thesis addresses charging effects observed when profiling undoped SiGe layers and the quantification of Ge fraction within SiGe layers using secondary ion mass spectrometry. Due to the highly resistive spreading resistance found for undoped SiGe layers when profiled using an O2+ incident beam, charging effects were found to mask the true layer profile. In order to overcome this problem a new approach is discussed for the first time. By illuminating the sample with a red laser light (wavelength 635mn) electron-hole pairs were created via photon absorption. The excess charge carriers were sufficient to overcome localised charging effects induced by the primary ion beam during SIMS analysis. In this manner, total charge suppression was achieved, thereby enabling a true determination of the SiGe sample profile to be obtained via SIMS. Finally, an analytical method enabling the accurate determination of Ge content of SiGe layers is discussed. The method employs a comparative ion yield methodology and enables both the spatial distribution and Ge concentration of SiGe layers to be accurately determined from a single SIMS measurement

Wave climate model of the Mid-Atlantic shelf and shoreline (Virginian Sea): Model development, shelf geomorphology, and preliminary results

A computerized wave climate model is developed that applies linear wave theory and shelf depth information to predict wave behavior as they pass over the continental shelf as well as the resulting wave energy distributions along the coastline. Reviewed are also the geomorphology of the Mid-Atlantic Continental Shelf, wave computations resulting from 122 wave input conditions, and a preliminary analysis of these data

The care of chickens

The purpose of this article is to provide purchasers of young chickens with an out- -1- line of the procedures and problems associated with successful chicken raising, and perhaps to serve as a reminder to those poultry farmers who already have a good knowledge of the subject. The wide range of subject matter has made it necessary to present much of the material in a condensed form, and reference should be made to various departmental leaflets for an elaboration of many of the points mentioned in this article. The advisory service of the Department of Agriculture, Poultry Branch, is available to poultry farmers seeking information. Instruction on all matters relating to poultry husbandry will be freely given and visits to farms by field officers can be arranged