5,415 research outputs found
Redundant actuator development study
Current and past supersonic transport configurations are reviewed to assess redundancy requirements for future airplane control systems. Secondary actuators used in stability augmentation systems will probably be the most critical actuator application and require the highest level of redundancy. Two methods of actuator redundancy mechanization have been recommended for further study. Math models of the recommended systems have been developed for use in future computer simulations. A long range plan has been formulated for actuator hardware development and testing in conjunction with the NASA Flight Simulator for Advanced Aircraft
Mutants and SU(3)_q invariants
Details of quantum knot invariant calculations using a specific
SU(3)_q-module are given which distinguish the Conway and Kinoshita-Teresaka
pair of mutant knots. Features of Kuperberg's skein-theoretic techniques for
SU(3)_q invariants in the context of mutant knots are also discussed.Comment: 17 pages. Published copy, also available at
http://www.maths.warwick.ac.uk/gt/GTMon1/paper18.abs.htm
Invariants of genus 2 mutants
Pairs of genus 2 mutant knots can have different Homfly polynomials, for
example some 3-string satellites of Conway mutant pairs. We give examples which
have different Kauffman 3-variable polynomials, answering a question raised by
Dunfield et al in their study of genus 2 mutants. While pairs of genus 2 mutant
knots have the same Jones polynomial, given from the Homfly polynomial by
setting v=s^2, we give examples whose Homfly polynomials differ when v=s^3. We
also give examples which differ in a Vassiliev invariant of degree 7, in
contrast to satellites of Conway mutant knots.Comment: 16 pages, 20 figure
A Method for siting and prioritizing the removal of derelict vessels in Florida Coastal Waters: test applications in the Florida Keys
Increased boating activities and new waterfront developments have contributed an
estimated 3,000 dismantled, abandoned, junked, wrecked, derelict vessels to Florida
coastal waters. This report outlines a method of siting and prioritizing derelict vessel
removal using the Florida Keys as a test area. The data base was information on 240
vessels, obtained from Florida Marine Patrol files. Vessel location was plotted on 1:250,000
regional and 1:5,000 and 1:12,000 site maps. Type of vessel, length, hull material, engine,
fuel tanks, overall condition, afloat and submerged characteristics, and accessibility, were
used to derive parametric site indices of removal priority and removal difficulty.
Results indicate 59 top priority cases which should be the focus of immediate clean
up efforts in the Florida Keys. Half of these cases are rated low to moderate in removal
difficulty; the remainder are difficult to remove. Removal difficulty is a surrogate for
removal cost: low difficulty -low cost, high difficulty - high cost. The rating scheme offers
coastal planners options of focusing removal operations either on (1) specific areas with
clusters of high priority derelict vessels or on (2) selected targeted derelicts at various,
specific locations. (PDF has 59 pages.
Redundancy of hydraulic flight control actuators
The constraint of requiring airplanes to have inherent aerodynamic stability can be removed by using active control systems. The resulting airplane requires control system reliability approaching that of the basic airframe. Redundant control actuators can be used to achieve the required reliability, but create mechanization and operational problems. Of numerous candidate systems, two different approaches to solving the problems associated with redundant actuators which appear the most likely to be used in advanced airplane control systems are described
Measurement of retinal vessel widths from fundus images based on 2-D modeling
Changes in retinal vessel diameter are an important sign of diseases such as hypertension, arteriosclerosis and diabetes mellitus. Obtaining precise measurements of vascular widths is a critical and demanding process in automated retinal image analysis as the typical vessel is only a few pixels wide. This paper presents an algorithm to measure the vessel diameter to subpixel accuracy. The diameter measurement is based on a two-dimensional difference of Gaussian model, which is optimized to fit a two-dimensional intensity vessel segment. The performance of the method is evaluated against Brinchmann-Hansen's half height, Gregson's rectangular profile and Zhou's Gaussian model. Results from 100 sample profiles show that the presented algorithm is over 30% more precise than the compared techniques and is accurate to a third of a pixel
Prediction of unstable crack length in aluminium alloys
A method was set down for predicting the unstable length of a
crack in a flat sheet of aluminium alloy subjected to a steady tensile
stress.
The basis of the method was to take the work done to failure in
the 'neck' region of a tensile test specimen and apply it, with a
suitable constraint factor, to the flat sheet to give the work rate
required to propagate the crack.
Experimental evidence is produced in support of the method
Alien Registration- Ryder, Percy R. (Gorham, Cumberland County)
https://digitalmaine.com/alien_docs/31601/thumbnail.jp
Prediction of unstable crack length in aluminium alloys
A method was set down for predicting the unstable length of a
crack in a flat sheet of aluminium alloy subjected to a steady tensile
stress.
The basis of the method was to take the work done to failure in
the 'neck' region of a tensile test specimen and apply it, with a
suitable constraint factor, to the flat sheet to give the work rate
required to propagate the crack.
Experimental evidence is produced in support of the method
Superfluid Helium Orbital Resupply Coupling
The resupply of superfluid helium to satellites and other space-based experiment packages can increase the useful longevity of these devices far beyond their present life expectancies which are many times determined by the supply of helium coolant. The transfer of superfluid helium to spacecraft in space will require a reusable coupling that functions at 1.8 Kelvin with little heat leak and low pressure drop. Moog has designed the Helium Resupply Coupling to meet these operational requirements. Initially, the coupling manual mode operation will be demonstrated on orbit by an EVA crew member during the Space Shuttle borne Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The ultimate application will use robotic (automatic) coupling operation to which the present design readily adapts. The utilization of Moog's exclusive Rotary Shut-Off (RSO) technology in the development of the Superfluid Helium Resupply Coupling is described. The coupling not only performs the function of a flow control valve and disconnect but also provides adequate safety features for a shuttle launched man-rated payload. In addition, the coupling incorporates the necessary features to provide the high thermal isolation of the internal flow path from the external environment
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