9,413 research outputs found
Virtual audio reproduced in a headrest
When virtual audio reproduction is simultaneously required in many seats, such as in aircraft or
cinemas, it may be convenient to use loudspeakers mounted inside each seat's headrest. In
this preliminary study, the feasibility of virtual audio reproduction in the headrest of a single seat
is explored using an inversion technique to compensate for crosstalk and the synthesis of head
related transfer functions. Although large changes in the magnitude of the signals reproduced
at the listener's ears are observed as the listener moves their head within the headrest, informal
listening tests indicate that the reproduced acoustic images are surprisingly stable in about an
eighth of an arc either side of the loudspeaker positions. Not surprisingly, frontal images are
more difficult to reproduce with headrest loudspeakers
Direct neutron capture cross sections of 62Ni in the s-process energy range
Direct neutron capture on 62Ni is calculated in the DWBA and the cross
sections in the energy range relevant for s-process nucleosynthesis are given.
It is confirmed that the thermal value of the capture cross section contains a
subthreshold resonance contribution. Contrary to previous investigations it is
found that the capture at higher energies is dominated by p-waves, thus leading
to a considerably increased cross section at s-process energies and a modified
energy dependence.Comment: 10 pages, 1 figure, corrected typos in Eq. 6 and subsequent paragrap
Secondary atomization of coal-water fuels for gas turbine applications
The main research objective is to determine the effect of coal-water
fuel (CWF) treatment on atomization quality when applied to an ultrafine
coal water fuel (solids loading - 50%) and at elevated pressures. The fuel
treatment techniques are expected to produce secondary atomization, i.e.,
disruptive shattering of CWF droplets subsequent to their leaving the
atomizing nozzle. Upon combustion, the finer fuel droplets would then yield
better burnout and finer fly ash size distribution, which in turn could
reduce problems of turbine blade erosion. The parallel objective was to
present quantitative information on the spray characteristics of CWF
(average droplet size and spray shape and angle) with and without fuel
treatment for purposes of application to the design of CWF-burning gas
turbine combustors.
The experiments include laser diffraction droplet size measurements and
high speed photographic studies of CWF sprays in the MIT Spray Test Facility
to determine mean droplet size (mass median diameter), droplet size
distribution, and spray shape and angle. For the spray tests at elevated
pressures, pressure vessels were constructed and installed in the spray test
rig. For support of data analyses, a capillary tube viscometer was used to
measure the CWF viscosity at the high shear rate that occurs in an atomizer
(> 104 sec' ).
A semi-empirical relationship was developed giving the CWF spray
droplet size as a function of the characteristic dimensionless parameters of
twin-fluid atomization, including the Weber number, the Reynolds number, and
the air-to-fuel mass flow ratio. The correlation was tested experimentally
and good agreement was found between calculated and measured drop sizes when
the high shear viscosity of the CWF was used in the semi-empirical equation.
Water and CWF spray tests at elevated pressure were made. Average
droplet sizes measured as a function of atomizing air-to-fuel ratios (AFRs)
at various chamber pressures show that the droplet mass median diameter
(MMD) decreases with increasing AFR at a given chamber pressure and
increases with increasing chamber pressure at a given AFR. In particular,
the results show that droplet sizes of CWF sprays decrease with increasing
chamber pressure if the atomizing air velocity is held constant.
Of the fuel treatment techniques investigated, the heating of CWF
(flash-atomization) was found to be very effective in reducing droplet size,
not only at atmospheric pressure but also at elevated pressure. Secondary
atomization by C02 absorption (used in a previous study) had given favorable
results on CWF combustion, but in this present case this fuel treatment did
not seem to have any observable effect on the drop size distribution of the
CWF spray at room temperature.
The spray angle was observed to reduce with increasing chamber pressure
for given atomizing conditions (AFR, fuel flow rate, fuel temperature). The
decreasing entrainment rate per unit length of spray with increasing chamber
pressure was mainly responsible for the reduction of the spray angle. The
heating of the CWF increased the spray angle, both at atmospheric and
elevated pressures. A model was developed to predict spray angle change for
the effects of the flash-atomization as a function of AFR, fuel flow rate,
and the superheat of the water
Attractor Metadynamics in Adapting Neural Networks
Slow adaption processes, like synaptic and intrinsic plasticity, abound in
the brain and shape the landscape for the neural dynamics occurring on
substantially faster timescales. At any given time the network is characterized
by a set of internal parameters, which are adapting continuously, albeit
slowly. This set of parameters defines the number and the location of the
respective adiabatic attractors. The slow evolution of network parameters hence
induces an evolving attractor landscape, a process which we term attractor
metadynamics. We study the nature of the metadynamics of the attractor
landscape for several continuous-time autonomous model networks. We find both
first- and second-order changes in the location of adiabatic attractors and
argue that the study of the continuously evolving attractor landscape
constitutes a powerful tool for understanding the overall development of the
neural dynamics
No evidence for absence of solar dynamo synchronization
Context: The old question of whether the solar dynamo is synchronized by the
tidal forces of the orbiting planets has recently received renewed interest,
both from the viewpoint of historical data analysis and in terms of theoretical
and numerical modelling. Aims: We aim to contribute to the solution of this
longstanding puzzle by analyzing cosmogenic radionuclide data from the last
millennium. Methods: We reconsider a recent time-series of C-inferred
sunspot data and compare the resulting cycle minima and maxima with the
corresponding conventional series down to 1610 A.D., enhanced by Schove's data
before that time. Results: We find that, despite recent claims to the contrary,
the C-inferred sunspot data are well compatible with a synchronized
solar dynamo, exhibiting a relatively phase-stable period of 11.07 years, which
points to a synchronizing role of the spring tides of the Venus-Earth-Jupiter
system.Comment: 8 pages, 7 figure
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