20,118 research outputs found
Turbulence as observed by concurrent measurements made at NSSL using weather radar, Doppler radar, Doppler lidar and aircraft
As air traffic increases and aircraft capability increases in range and operating altitude, the exposure to weather hazards increases. Turbulence and wind shears are two of the most important of these hazards that must be taken into account if safe flight operations are to be accomplished. Beginning in the early 1960's, Project Rough Rider began thunderstorm investigations. Past and present efforts at the National Severe Storm Laboratory (NSSL) to measure these flight safety hazards and to describe the use of Doppler radar to detect and qualify these hazards are summarized. In particular, the evolution of the Doppler-measured radial velocity spectrum width and its applicability to the problem of safe flight is presented
Matrix inequalities from a two variables functional
Several matrix/operator inequalies are given. Most of them are unexpected
extensions of the Araki Log-majorization theorem, obtained thanks to a new
log-majorization for positive linear maps and normal operators (Theorem 2.9).
The main idea and technical tool is a two variables log-convex norm functional
(Theorem 1.2).Comment: Final version, to appear in International J. Math: Two corollaries on
Schur products have been added at the end of Section
Pinchings and Positive linear maps
We employ the pinching theorem, ensuring that some operators A admit any
sequence of contractions as an operator diagonal of A, to deduce/improve two
recent theorems of Kennedy-Skoufranis and Loreaux-Weiss for conditional
expectations onto a masa in the algebra of operators on a Hilbert space. We
also get a few results for sums in a unitary orbit
Numerical Simulations of Bouncing Jets
Bouncing jets are fascinating phenomenons occurring under certain conditions
when a jet impinges on a free surface. This effect is observed when the fluid
is Newtonian and the jet falls in a bath undergoing a solid motion. It occurs
also for non-Newtonian fluids when the jets falls in a vessel at rest
containing the same fluid.
We investigate numerically the impact of the experimental setting and the
rheological properties of the fluid on the onset of the bouncing phenomenon.
Our investigations show that the occurrence of a thin lubricating layer of air
separating the jet and the rest of the liquid is a key factor for the bouncing
of the jet to happen.
The numerical technique that is used consists of a projection method for the
Navier-Stokes system coupled with a level set formulation for the
representation of the interface. The space approximation is done with adaptive
finite elements. Adaptive refinement is shown to be very important to capture
the thin layer of air that is responsible for the bouncing
On a decomposition lemma for positive semi-definite block-matrices
This short note, in part of expository nature, points out several new or
recent consequences of a quite nice decomposition for positive semi-definite
matrices
SFNet: Learning Object-aware Semantic Correspondence
We address the problem of semantic correspondence, that is, establishing a
dense flow field between images depicting different instances of the same
object or scene category. We propose to use images annotated with binary
foreground masks and subjected to synthetic geometric deformations to train a
convolutional neural network (CNN) for this task. Using these masks as part of
the supervisory signal offers a good compromise between semantic flow methods,
where the amount of training data is limited by the cost of manually selecting
point correspondences, and semantic alignment ones, where the regression of a
single global geometric transformation between images may be sensitive to
image-specific details such as background clutter. We propose a new CNN
architecture, dubbed SFNet, which implements this idea. It leverages a new and
differentiable version of the argmax function for end-to-end training, with a
loss that combines mask and flow consistency with smoothness terms.
Experimental results demonstrate the effectiveness of our approach, which
significantly outperforms the state of the art on standard benchmarks.Comment: cvpr 2019 oral pape
Relationships Among Values, Achievement Orientations, and Attitudes in Youth Sport
This research examines the value-expressive function of attitudes and achievement goal theory in predicting moral attitudes. In Study 1, the Youth Sport Values Questionnaire (YSVQ; Lee, Whitehead, & Balchin, 2000) was modified to measure moral,competence, and status values. In Study 2, structural equation modeling on data from 549 competitors (317 males, 232 females) aged 12–15 years showed that moral and competence values predicted prosocial attitudes, whereas moral (negatively) and status values (positively)predicted antisocial attitudes. Competence and status values predicted task and ego orientation, respectively, and task and ego orientation partially mediated the effect of competence values on prosocial attitudes and of status values on antisocial attitudes, respectively. The role of sport values is discussed, and new research directions are proposed
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