497 research outputs found
Meta-pipeline: A new execution mechanism for distributed pipeline processing
The Caravela platform has been proposed by the authors of this paper to perform distributed stream-based computing on general purpose computation. This platform uses a secured execution unit called flow-model that prevents remote users to touch local information in a computer. The flow-model is assigned to local or remote processing units that execute its program. This paper is focused on a new execution mechanism that defines a pipeline composed by flow-models, called meta-pipeline, and is designed as a set of additional functions of the Caravela platform. The pipeline is executed automatically by the meta-pipeline runtime environment. This paper describes the execution mechanism and also presents an application example.info:eu-repo/semantics/acceptedVersio
An automatic visual analysis system for tennis
This article presents a novel video analysis system for coaching tennis players of all levels, which uses computer vision algorithms to automatically edit and index tennis videos into meaningful annotations.
Existing tennis coaching software lacks the ability to automatically index a tennis match into key events, and therefore, a coach who uses existing software is burdened with time-consuming manual video editing. This work aims to explore the effectiveness of a system to automatically detect tennis events. A secondary aim of this work is to explore the bene- fits coaches experience in using an event retrieval system to retrieve the automatically indexed events. It was found that automatic event detection can significantly improve the experience of using video feedback as part of an instructional coaching session. In addition to the automatic detection of key tennis events, player and ball movements are automati- cally tracked throughout an entire match and this wealth of data allows users to find interesting patterns in play. Player and ball movement information are integrated with the automatically detected tennis events, and coaches can query the data to retrieve relevant key points during a match or analyse player patterns that need attention. This coaching software system allows coaches to build advanced queries, which cannot be facilitated with existing video coaching solutions, without tedious manual indexing. This article proves that the event detection algorithms in this work can detect the main events in tennis with an average precision and recall of 0.84 and 0.86, respectively, and can typically eliminate man- ual indexing of key tennis events
Tunable high-energy ion source via oblique laser pulse incidence on a double-layer target
The laser-driven acceleration of high quality proton beams from a
double-layer target, comprised of a high-Z ion layer and a thin disk of
hydrogen, is investigated with three-dimensional particle-in-cell simulations
in the case of oblique incidence of a laser pulse. It is shown that the proton
beam energy reaches its maximum at a certain incidence angle of the laser
pulse, where it can be much greater than the energy at normal incidence. The
proton beam propagates at some angle with respect to the target surface normal,
as determined by the proton energy and the incidence angle
Pressure formulas for liquid metals and plasmas based on the density-functional theory
At first, pressure formulas for the electrons under the external potential
produced by fixed nuclei are derived both in the surface integral and volume
integral forms concerning an arbitrary volume chosen in the system; the surface
integral form is described by a pressure tensor consisting of a sum of the
kinetic and exchange-correlation parts in the density-functional theory, and
the volume integral form represents the virial theorem with subtraction of the
nuclear virial. Secondly on the basis of these formulas, the thermodynamical
pressure of liquid metals and plasmas is represented in the forms of the
surface integral and the volume integral including the nuclear contribution.
From these results, we obtain a virial pressure formula for liquid metals,
which is more accurate and simpler than the standard representation. From the
view point of our formulation, some comments are made on pressure formulas
derived previously and on a definition of pressure widely used.Comment: 18 pages, no figur
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