11,369 research outputs found
Impingement of Cloud Droplets on 36.5-Percent-Thick Joukowski Airfoil at Zero Angle of Attack and Discussion of Use as Cloud Measuring Instrument in Dye-Tracer Technique
The trajectories of droplets i n the air flowing past a 36.5-percent-thick Joukowski airfoil at zero angle of attack were determined. The amount of water i n droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and cover a large range of flight and atmospheric conditions. With the detailed impingement information available, the 36.5-percent-thick Joukowski airfoil can serve the dual purpose of use as the principal element in instruments for making measurements in clouds and of a basic shape for estimating impingement on a thick streamlined body. Methods and examples are presented for illustrating some limitations when the airfoil is used as the principal element in the dye-tracer technique
Impingement of Water Droplets on NACA 65A004 Airfoil at 0 Deg Angle of Attack
The trajectories of water droplets in the air flowing past an NACA 6511004 airfoil at a n angle of attack of 0 deg were determined. The amount of water in droplet form impinging on the airfoil , the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented t o cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those previously reported for the same airfoil at angles of attack of 4 deg and 8 deg
Review of Cosmic Ray experiments with underground detectors
The most important underground detectors addressing Cosmic Ray physics are
described, with a special emphasis on the description of the used technology.Comment: Invited talk at 6th International Conference on advanced Technology
and Particle Physics, Villa Olmo, Como, Italy, October 5-9, 1998, To be
published in Nucl. Phys. B, Proc. Supp
Impingement of Water Droplets on NACA 65A004 Airfoil at 8 deg Angle of Attack
The trajectories of droplets in the air flowing past an NACA 65AO04 airfoil at an angle of attack of 8 deg were determined.. The amount of water in droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented to cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those previously reported for the same airfoil at an angle of attack of 4 deg
Effects of burying and removing dead leaves from the ground on the development of scab epidemics in an apple organic orchard.
Ascospores produced on scabbed leaves in the leaf litter constitute the primary
inoculum causing scab infections in apple orchards during the year. The trial, carried
out in a commercial organic orchard, permitted to evaluate the effects of the
removal of dead leaves located on the inter-row supplemented by the ploughing in of
the leaves left on the row, on the development of scab epidemics. From the first
recorded contamination to harvest time, lesions on leaves and fruits were counted to
determine reduction in disease incidence and severity, compared with the untreated
plots. Disease severity as a function of the distance from the untreated plot was also
observed, to evaluate the spore dispersal gradient within the orchard. The results
show that the ploughing in and the removal of the litter reduced disease incidence by
62% on leaves, and by almost 82% on fruits to harvest. Moreover, measurements of
the dispersal gradient show that the spores do not disperse, or little, beyond 20m of
the untreated zone
Comparison between S. T. radar and in situ balloon measurements
A campaign for simultaneous in situ and remote observation of both troposphere and stratosphere took place near Aire-sur-l'Adour (in southeastern France) on May 4, 1984. The aim of this campaign was a better understanding of the physics of radar echoes. The backscattered signal obtained with a stratosphere-troposphere radar both at the vertical and 15 deg. off vertical is compared with the velocity and temperature measurements made in the same region (about 10 km north of the radar site) by balloon-borne ionic anenometers and temperature sensors. In situ measurements clearly indicate that the temperature fluctuations are not always consistent with the standard turbulent theory. Nevertheless, the assumptions generally made (isotropy and turbulent field in k) and the classical formulation so derived for radar reflectivity are able to reproduce the shape of the radar return power profiles in oblique directions. Another significant result is the confirmation of the role played by the atmospheric stratification in the vertical echo power. It is important to develop these simultaneous in situ and remote experiments for a better description of the dynamical and thermal structure of the atmosphere and for a better understanding of the mechanisms governing clear-air radar reflectivity
High Metallicity Mg II Absorbers in the z < 1 Lyman alpha Forest of PKS 0454+039: Giant LSB Galaxies?
We report the discovery of two iron-group enhanced high-metallicity Mg II
absorbers in a search through 28 Lyman Alpha forest clouds along the PKS
0454+039 sight line. Based upon our survey and the measured redshift number
densities of W_r(MgII) <= 0.3 A absorbers and Lyman Alpha absorbers at z ~ 1,
we suggest that roughly 5% of Lyman Alpha absorbers at z < 1 will exhibit
"weak" Mg II absorption to a 5-sigma W_r(2796) detection limit of 0.02 A. The
two discovered absorbers, at redshifts z = 0.6248 and z = 0.9315, have W_r(Lya)
= 0.33 and 0.15 A, respectively. Based upon photoionization modeling, the H I
column densities are inferred to be in the range 15.8 <= log N(HI) <= 16.8
cm^-2. For the z = 0.6428 absorber, if the abundance pattern is solar, then the
cloud has [Fe/H] > -1; if its gas-phase abundance follows that of depleted
clouds in our Galaxy, then [Fe/H] > 0 is inferred. For the z = 0.9315 absorber,
the metallicity is [Fe/H] > 0, whether the abundance pattern is solar or
suffers depletion. Imaging and spectroscopic studies of the PKS 0454+039 field
reveal no candidate luminous objects at these redshifts. We discuss the
possibility that these Mg II absorbers may arise in the class of "giant" low
surface brightness galaxies, which have [Fe/H] >= -1, and even [Fe/H] >= 0, in
their extended disks. We tentatively suggest that a substantial fraction of
these "weak" Mg II absorbers may select low surface brightness galaxies out to
z ~ 1.Comment: Accepted The Astrophysical Journal; 25 pages; 6 encapsulated figure
Analysis of the Scanning Tunneling Microscopy Images of the Charge Density Wave Phase in Quasi-one-dimensional Rb0.3MoO3
The experimental STM images for the CDW phase of the blue bronze RbMoO3 have
been successfully explained on the basis of first-principles DFT calculations.
Although the density of states near the Fermi level strongly concentrates in
two of the three types of Mo atoms Mo-II and Mo-III, the STM measurement mostly
probes the contribution of the uppermost O atoms of the surface, associated
with the Mo-IO6 octahedra. In addition, it is found that the surface
concentration of Rb atoms plays a key role in determining the surface nesting
vector and hence the periodicity of the CDW modulation. Significant
experimental inhomogeneities of the b* surface component of the wavevector of
the modulation, probed by STM, are reported. The calculated changes in the
surface nesting vector are consistent with the observed experimental
inhomogeneities.Comment: 4 pages 5 Figure
Quantum Walks driven by many coins
Quantum random walks have been much studied recently, largely due to their
highly nonclassical behavior. In this paper, we study one possible route to
classical behavior for the discrete quantum random walk on the line: the use of
multiple quantum ``coins'' in order to diminish the effects of interference
between paths. We find solutions to this system in terms of the single coin
random walk, and compare the asymptotic limit of these solutions to numerical
simulations. We find exact analytical expressions for the time-dependence of
the first two moments, and show that in the long time limit the ``quantum
mechanical'' behavior of the one-coin walk persists. We further show that this
is generic for a very broad class of possible walks, and that this behavior
disappears only in the limit of a new coin for every step of the walk.Comment: 36 pages RevTeX 4.0 + 5 figures (encapsulated Postscript). Submitted
to Physical Review
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