3,867 research outputs found
Bondgraph modelling and simulation of the dynamic behaviour of above-knee prostheses
A mathematical model was used to investigate the dynamic behaviour of an above-knee (AK) prosthesis in the swing phase and to analyse the influence of mass and mass distribution on the maximal stump load and the required energy. The model consists of a bondgraph model of the prosthesis and a “walking” model which predicts the walking velocity, step length and the femoral trajectory. Equipment was developed to measure the inertial properties of the components of the prosthesis. \ud
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Through computer simulation, stickdiagrams of the swing phase and graphs of the variation with time of the hip and stump forces were obtained. It was found that for a normal AK prosthesis with a knee-lock mechanism the axial stump load is greatest at the beginning and at the end of the swing phase. At a walking velocity of 5 km/hr the maximum axial stump load amounts to 2.1 times the static weight of the prosthesis. \ud
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The maximum axial stump force appeared to be almost directly proportional to the total mass of the prosthesis but independent of the mass distribution. The required energy also increased with the mass of the prosthesis but is' dependent on mass distribution. \ud
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Because of their comparable weights the influence of the shoe is almost equal to the influence of the prosthetic foot. Thus lightweight shoes should be used with lightweight prosthetic feet in order to add to their advantages
Verbindingsmaatlat voor de landbouw : ontwikkeling van een indicator die een beeld geeft van de verbinding tussen een biologisch landbouwbedrijf en zijn omgeving : onderdeel van koepelproject Duurzaamheidprestaties Biologische Landbouw
Eén van de kenmerken van duurzaamheid, in de traditionele people, plant, profit indeling, is de mate waarin landbouw zich weet te verbinden aan de maatschappij. Deze studie focust zich op de ontwikkeling van een indicator die de mate van verbinding weergeeft. Omdat verbinding het resultaat is van een complexe sociale interactie die lastig meetbaar is, is er geen indicator beschikbaar die direct iets zegt over de mate van verbinding die een bedrijf of een sector weet te realiseren. Omdat er weinig informatie wordt vastgelegd over verbindingen die ondernemers aangaan in bestaande databases is ervoor gekozen om een indicator te ontwikkelen die direct door de ondernemer ingevuld kan worden. In deze studie is een eerste aanzet gedaan voor de ontwikkeling van deze duurzaamheidsindicator voor verbindingen
A new limit on the Ultra-High-Energy Cosmic-Ray flux with the Westerbork Synthesis Radio Telescope
A particle cascade (shower) in a dielectric, for example as initiated by an
ultra-high energy cosmic ray, will have an excess of electrons which will emit
coherent \v{C}erenkov radiation, known as the Askaryan effect. In this work we
study the case in which such a particle shower occurs in a medium just below
its surface. We show, for the first time, that the radiation transmitted
through the surface is independent of the depth of the shower below the surface
when observed from far away, apart from trivial absorption effects. As a direct
application we use the recent results of the NuMoon project, where a limit on
the neutrino flux for energies above \,eV was set using the Westerbork
Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to
set a limit on the flux of ultra-high-energy cosmic rays.Comment: Accepted for publication in Phys. Rev.
Raising the accuracy of determination the moment of inertia of rotorsflywheels mechanical gyroscope in method of torsional oscillations
HST Snapshot Survey of Post-AGB Objects
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB
objects are shown. The aim of the survey is to complement existing HST images
of PPN and to connect various types of nebulosities with physical and chemical
properties of their central stars. Nebulosities are detected in 15 of 33
sources. Images and photometric and geometric measurements are presented. For
sources with nebulosities we see a morphological bifurcation into two groups,
DUPLEX and SOLE, as previous studies have found. We find further support to the
previous results suggesting that this dichotomy is caused by a difference in
optical thickness of the dust shell. The remaining 18 sources are classified as
stellar post-AGB objects, because our observations indicate a lack of
nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE
based on their infrared colors. The cause of the differences among the groups
are investigated. We discuss some evidence suggesting that high progenitor-mass
AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass
AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources
probably have low mass progenitors and do not seem to develop nebulosities
during the post-AGB phase and therefore do not become planetary nebulae.Comment: 21 pages, 11 figure
Shifts in rhizosphere fungal community during secondary succession following abandonment from agriculture
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