1,469 research outputs found
In-flight measurement of propeller noise on the fuselage of an airplane
In-flight measurements of propeller noise on the fuselage of an OV-10A aircraft were obtained using a horizontal and a vertical microphone array. A wide range of flight conditions were tested including changes in angle of attack, sideslip angle, power coefficient, helical tip Mach number and advance ratio, and propeller direction of rotation. Results show a dependence of the level and directivity of the tones on the angle of attack and on the sideslip angle with the propeller direction of rotation, which is similar to results obtained in wind tunnel tests with advanced propeller designs. The level of the tones at each microphone increases with increasing angle of attack for inboard-down propeller rotation and decreases for inboard-up rotation. The level also increases with increasing slideslip angle for both propeller directions of rotation. Increasing the power coefficient results in a slight increase in the level of the tones. A strong shock wave is generated by the propeller blades even at relatively low helical tip Mach numbers resulting in high harmonic levels. As the helical tip Mach number and the advance ratio are increased, the level of the higher harmonics increases much faster than the level of the blade passage frequency
Photodegradation Mechanisms of Tetraphenyl Butadiene Coatings for Liquid Argon Detectors
We report on studies of degradation mechanisms of tetraphenyl butadiene (TPB)
coatings of the type used in neutrino and dark matter liquid argon experiments.
Using gas chromatography coupled to mass spectrometry we have detected the
ultraviolet-blocking impurity benzophenone (BP). We monitored the drop in
performance and increase of benzophenone concentration in TPB plates with
exposure to ultraviolet (UV) light, and demonstrate the correlation between
these two variables. Based on the presence and initially exponential increase
in the concentration of benzophenone observed, we propose that TPB degradation
is a free radical-mediated photooxidation reaction, which is subsequently
confirmed by displaying delayed degradation using a free radical inhibitor.
Finally we show that the performance of wavelength-shifting coatings of the
type envisioned for the LBNE experiment can be improved by 10-20%, with
significantly delayed UV degradation, by using a 20% admixture of
4-tert-Butylcatechol.Comment: 12 pages, 9 figures. Submitted to JINS
Phenotypic and genetic variability of morphometrical traits in natural populations of Drosophila melanogaster and D simulans. I. Geographic variations
International audienc
Phenotypic and genetic variability of morphometrical traits in natural populations of Drosophila melanogaster and D simulans. II. Within-population variability
International audienc
Mean Field Theory of Sandpile Avalanches: from the Intermittent to the Continuous Flow Regime
We model the dynamics of avalanches in granular assemblies in partly filled
rotating cylinders using a mean-field approach. We show that, upon varying the
cylinder angular velocity , the system undergoes a hysteresis cycle
between an intermittent and a continuous flow regimes. In the intermittent flow
regime, and approaching the transition, the avalanche duration exhibits
critical slowing down with a temporal power-law divergence. Upon adding a white
noise term, and close to the transition, the distribution of avalanche
durations is also a power-law. The hysteresis, as well as the statistics of
avalanche durations, are in good qualitative agreement with recent experiments
in partly filled rotating cylinders.Comment: 4 pages, RevTeX 3.0, postscript figures 1, 3 and 4 appended
The Golden Channel at a Neutrino Factory revisited: improved sensitivities from a Magnetised Iron Neutrino Detector
This paper describes the performance and sensitivity to neutrino mixing
parameters of a Magnetised Iron Neutrino Detector (MIND) at a Neutrino Factory
with a neutrino beam created from the decay of 10 GeV muons. Specifically, it
is concerned with the ability of such a detector to detect muons of the
opposite sign to those stored (wrong-sign muons) while suppressing
contamination of the signal from the interactions of other neutrino species in
the beam. A new more realistic simulation and analysis, which improves the
efficiency of this detector at low energies, has been developed using the GENIE
neutrino event generator and the GEANT4 simulation toolkit. Low energy neutrino
events down to 1 GeV were selected, while reducing backgrounds to the
level. Signal efficiency plateaus of ~60% for and ~70% for
events were achieved starting at ~5 GeV. Contamination from the
oscillation channel was studied for the first
time and was found to be at the level between 1% and 4%. Full response matrices
are supplied for all the signal and background channels from 1 GeV to 10 GeV.
The sensitivity of an experiment involving a MIND detector of 100 ktonnes at
2000 km from the Neutrino Factory is calculated for the case of . For this value of , the accuracy in the
measurement of the CP violating phase is estimated to be , depending on the value of ,
the CP coverage at is 85% and the mass hierarchy would be determined
with better than level for all values of
Energy radiation of moving cracks
The energy radiated by moving cracks in a discrete background is analyzed.
The energy flow through a given surface is expressed in terms of a generalized
Poynting vector. The velocity of the crack is determined by the radiation by
the crack tip. The radiation becomes more isotropic as the crack velocity
approaches the instability threshold.Comment: 7 pages, embedded figure
Nanoscale broadband transmission lines for spin qubit control
The intense interest in spin-based quantum information processing has caused
an increasing overlap between two traditionally distinct disciplines, such as
magnetic resonance and nanotechnology. In this work we discuss rigourous design
guidelines to integrate microwave circuits with charge-sensitive
nanostructures, and describe how to simulate such structures accurately and
efficiently. We present a new design for an on-chip, broadband, nanoscale
microwave line that optimizes the magnetic field driving a spin qubit, while
minimizing the disturbance on a nearby charge sensor. This new structure was
successfully employed in a single-spin qubit experiment, and shows that the
simulations accurately predict the magnetic field values even at frequencies as
high as 30 GHz.Comment: 18 pages, 8 figures, 1 table, pdflate
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