11,683 research outputs found
Variable pitch fan system for NASA/Navy research and technology aircraft
Preliminary design of a shaft driven, variable-pitch lift fan and lift-cruise fan was conducted for a V/STOL Research and Technology Aircraft. The lift fan and lift-cruise fan employed a common rotor of 157.5 cm diameter, 1.18 pressure ratio variable-pitch fan designed to operate at a rotor-tip speed of 284 mps. Fan performance maps were prepared and detailed aerodynamic characteristics were established. Cost/weight/risk trade studies were conducted for the blade and fan case. Structural sizing was conducted for major components and weights determined for both the lift and lift-cruise fans
CVD of CrO2: towards a lower temperature deposition process
We report on the synthesis of highly oriented a-axis CrO2 films onto (0001)
sapphire by atmospheric pressure CVD from CrO3 precursor, at growth
temperatures down to 330 degree Celsius, i.e. close to 70 degrees lower than in
published data for the same chemical system. The films keep the high quality
magnetic behaviour as those deposited at higher temperature, which can be
looked as a promising result in view of their use with thermally sensitive
materials, e.g. narrow band gap semiconductors.Comment: 13 pages, 4 figure
Assessing soil N availability indices - is inorganic N enough?
Non-Peer ReviewedAssessing soil N availability is complicated enormously by the complexity of the N-cycle.
Over the years, several methods of estimating potentially available N have been suggested. In an
ongoing study, we have been assessing the suitability of a number of these methods for
predicting potential crop response to fertilizer N. In particular, we correlated amino-sugar N
levels to wheat yield across a variable landscape. This relatively new soil N test appears to be
sensitive to changes in organic matter quality as related to landscape position and holds some
promise for assessing potentially available N. The results presented here are preliminary
Evidence for Nodal superconductivity in SrScFePO
Point contact Andreev reflection spectra have been taken as a function of
temperature and magnetic field on the polycrystalline form of the newly
discovered iron-based superconductor Sr2ScFePO3. A zero bias conductance peak
which disappears at the superconducting transition temperature, dominates all
of the spectra. Data taken in high magnetic fields show that this feature
survives until 7T at 2K and a flattening of the feature is observed in some
contacts. Here we inspect whether these observations can be interpreted within
a d-wave, or nodal order parameter framework which would be consistent with the
recent theoretical model where the height of the P in the Fe-P-Fe plane is key
to the symmetry of the superconductivity. However, in polycrystalline samples
care must be taken when examining Andreev spectra to eliminate or take into
account artefacts associated with the possible effects of Josephson junctions
and random alignment of grains.Comment: Published versio
Colour Image Reproduction for 3D Printing Facial Prostheses
In this chapter, using colour 3D printing technology, a 3D colour image reproduction system is detailed for the semi-automated and accurate additive manufacturing of facial soft tissue prostheses. A protocol for 3D colour image reproduction was designed based on the six steps of processing. For this specific application, protocols for each sub‐process required development and details of each technique applied are discussed. The quality of facial prostheses was evaluated through objective measurement and subjective assessment. The results demonstrated that the proposed colour reproduction system can be effectively used to produce accurate skin colour with fine textures over a 3D shape, with significant savings in both time and cost when compared to traditional techniques
NIKA: A millimeter-wave kinetic inductance camera
Current generation millimeter wavelength detectors suffer from scaling limits
imposed by complex cryogenic readout electronics. To circumvent this it is
imperative to investigate technologies that intrinsically incorporate strong
multiplexing. One possible solution is the kinetic inductance detector (KID).
In order to assess the potential of this nascent technology, a prototype
instrument optimized for the 2 mm atmospheric window was constructed. Known as
the N\'eel IRAM KIDs Array (NIKA), it was recently tested at the Institute for
Millimetric Radio Astronomy (IRAM) 30-meter telescope at Pico Veleta, Spain.
The measurement resulted in the imaging of a number of sources, including
planets, quasars, and galaxies. The images for Mars, radio star MWC349, quasar
3C345, and galaxy M87 are presented. From these results, the optical NEP was
calculated to be around WHz. A factor of 10
improvement is expected to be readily feasible by improvements in the detector
materials and reduction of performance-degrading spurious radiation.Comment: Accepted for publication in Astronomy & Astrophysic
Spin polarized transport current in n-type co-doped ZnO thin films measured by Andreev spectroscopy
We use point contact Andreev reflection measurements to determine the spin
polarization of the transport current in pulse laser deposited thin films of
ZnO with 1% Al and with and without 2%Mn. Only films with Mn are ferromagnetic
and show spin polarization of the transport current of up to 55 0.5% at
4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mn
where the polarization is consistent with zero. Our results imply strongly that
ferromagnetism in these Al doped ZnO films requires the presence of Mn.Comment: Published versio
Evaluation of Interactions Between Oilfield Chemicals and Reservoir Rocks
The authors gratefully acknowledge Petroleum Technology Development Fund (PTDF) Nigeria for funding the PhD work from which the materials and results presented in this paper originated. The authors are also grateful to the Laboratory technicians in the School of Pharmacy and Life science and Gray School of arts, Robert Gordon University; and School of Engineering, University of Aberdeen for their technical support.Peer reviewedPublisher PD
Flux-dynamics associated with the Second Magnetisation Peak in iron-pnictide Ba_{1-x}K_xFe_2As_2
We report on isofield magnetic relaxation data on a single crystal of
with superconducting transition temperature = 32.7 K
which exhibit the so called fish-tail effect. A surface map of the
superconducting transition temperature shows that the superconducting
properties are close to homogeneous across the sample. Magnetic relaxation
data, M(t), was used to obtain the activation energy U(M) in order to study
different vortex dynamics regimes. Results of this analysis along with time
dependent measurements as a function of field and temperature extended to the
reversible region of some M(H) curves demonstrate that the irreversibility as
well the second magnetization peak position, , are time dependent and
controlled by plastic motion of the vortex state. In the region delimited by a
characteristic field Hon (well below ), and , the vortex dynamics is
controlled by collective pinning. For fields below Hon the activation energy,
, increases with field as expected for collective pinning, but the pinning
mechanism is likely to be in the single vortex limit.Comment: 8 pages, 8 figures, one tabl
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