10,429 research outputs found
Measurements of farfield sound generation from a flow-excited cavity
Results of 1/3-octave-band spectral measurements of internal pressures and the external acoustic field of a tangentially blown rectangular cavity are compared. Proposed mechanisms for sound generation are reviewed, and spectra and directivity plots of cavity noise are presented. Directivity plots show a slightly modified monopole pattern. Frequencies of cavity response are calculated using existing predictions and are compared with those obtained experimentally. The effect of modifying the upstream boundary layer on the noise was investigated, and its effectiveness was found to be a function of cavity geometry and flow velocity
Experimental pressure drop investigation of wetting and nonwetting mercury condensing in uniformly tapered tubes
Pressure drop of wetting and nonwetting mercury condensing in tapered tubes - turbogenerator system
Self-Consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential
We calculate the self-consistent response of an axisymmetric galactic disk
perturbed by an elliptical halo potential of harmonic number m = 2, and obtain
the net disk ellipticity. Such a potential is commonly expected to arise due to
a galactic tidal encounter and also during the galaxy formation process. The
self-gravitational potential corresponding to the self-consistent,
non-axisymmetric density response of the disk is obtained by inversion of
Poisson equation for a thin disk. This response potential is shown to oppose
the perturbation potential, because physically the disk self-gravity resists
the imposed potential. This results in a reduction in the net ellipticity of
the perturbation halo potential in the disk plane. The reduction factor
denoting this decrease is independent of the strength of the perturbation
potential, and has a typical minimum value of 0.75 - 0.9 for a wide range of
galaxy parameters. The reduction is negligible at all radii for higher
harmonics (m > or = 3) of the halo potential. (abridged).Comment: 26 pages (LaTex- aastex style), 3 .eps figures. To appear in the
Astrophysical Journal, Vol. 542, Oct. 20, 200
Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion
An open-ring ion trap, also referred to as transparent trap was initially
built up to perform - correlation experiments with radioactive
ions. This trap geometry is also well suited to perform experiments with
laser-cooled ions, serving for the development of a new type of Penning trap,
in the framework of the project TRAPSENSOR at the University of Granada. The
goal of this project is to use a single Ca ion as detector for
single-ion mass spectrometry. Within this project and without any modification
to the initial electrode configuration, it was possible to perform Doppler
cooling on Ca ions, starting from large clouds and reaching single
ion sensitivity. This new feature of the trap might be important also for other
experiments with ions produced at Radioactive Ion Beam (RIB) facilities. In
this publication, the trap and the laser system will be described, together
with their performance with respect to laser cooling applied to large ion
clouds down to a single ion.Comment: 9 pages, 13 figure
Controlling surface morphologies by time-delayed feedback
We propose a new method to control the roughness of a growing surface, via a
time-delayed feedback scheme. As an illustration, we apply this method to the
Kardar-Parisi-Zhang equation in 1+1 dimensions and show that the effective
growth exponent of the surface width can be stabilized at any desired value in
the interval [0.25,0.33], for a significant length of time. The method is quite
general and can be applied to a wide range of growth phenomena. A possible
experimental realization is suggested.Comment: 4 pages, 3 figure
Thermal field desorption spectroscopy of chemisorbed hydrogen for a single step site
The steady state molecular hydrogen ion yield from a single atomic step site of a [110]-oriented tungsten and of a [100]-oriented rhodium crystal is determined as a function of surface temperature using mass and energy resolved probe hole field ion microscopy. A second order kinetic model is developed to fit the experimental data thus obtaining the hydrogen binding energy. For local fields of about 3 V/Å the data are close to values obtained from thermal desorption spectroscopy. A comparison is made with calculations of the field-adsorption binding energy of atomic hydrogen on a jellium surface based on density functional theory
Nonflammable, antistatic, and heat-sealable film
Antistatic, heat-sealable, nonflammable films prepared from polyvinylidene fluoride and polyvinylidene chloride resin
Analytic models and forward scattering from accelerator to cosmic-ray energies
Analytic models for hadron-hadron scattering are characterized by analytical
parametrizations for the forward amplitudes and the use of dispersion relation
techniques to study the total cross section and the
parameter. In this paper we investigate four aspects related to the application
of the model to and scattering, from accelerator to cosmic-ray
energies: 1) the effect of different estimations for from
cosmic-ray experiments; 2) the differences between individual and global
(simultaneous) fits to and ; 3) the role of the
subtraction constant in the dispersion relations; 4) the effect of distinct
asymptotic inputs from different analytic models. This is done by using as a
framework the single Pomeron and the maximal Odderon parametrizations for the
total cross section. Our main conclusions are the following: 1) Despite the
small influence from different cosmic-ray estimations, the results allow us to
extract an upper bound for the soft pomeron intercept: ;
2) although global fits present good statistical results, in general, this
procedure constrains the rise of ; 3) the subtraction constant as
a free parameter affects the fit results at both low and high energies; 4)
independently of the cosmic-ray information used and the subtraction constant,
global fits with the odderon parametrization predict that, above GeV, becomes greater than , and
this result is in complete agreement with all the data presently available. In
particular, we infer at GeV and
at 500 GeV (BNL RHIC energies).Comment: 16 pages, 7 figures, aps-revtex, wording changes, corrected typos, to
appear in Physical Review
A new approach of endotoxic testing by using a monoclonal antibody against endotoxin (WN1-222/5) and flow cytometry
On the Lebesgue measure of Li-Yorke pairs for interval maps
We investigate the prevalence of Li-Yorke pairs for and
multimodal maps with non-flat critical points. We show that every
measurable scrambled set has zero Lebesgue measure and that all strongly
wandering sets have zero Lebesgue measure, as does the set of pairs of
asymptotic (but not asymptotically periodic) points.
If is topologically mixing and has no Cantor attractor, then typical
(w.r.t. two-dimensional Lebesgue measure) pairs are Li-Yorke; if additionally
admits an absolutely continuous invariant probability measure (acip), then
typical pairs have a dense orbit for . These results make use of
so-called nice neighborhoods of the critical set of general multimodal maps,
and hence uniformly expanding Markov induced maps, the existence of either is
proved in this paper as well.
For the setting where has a Cantor attractor, we present a trichotomy
explaining when the set of Li-Yorke pairs and distal pairs have positive
two-dimensional Lebesgue measure.Comment: 41 pages, 3 figure
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