165 research outputs found
Combinatorial Tools for Regge Calculus
In this short note we briefly review some recent mathematical results
relevant to the classical Regge Calculus evolution problem.Comment: 5 pages, LaTeX, no figures. To appear on the Proceedings of the 12th
Italian Conference on General Relativity and Gravitational Physic
The Use of HepRep in GLAST
HepRep is a generic, hierarchical format for description of graphics
representables that can be augmented by physics information and relational
properties. It was developed for high energy physics event display applications
and is especially suited to client/server or component frameworks. The GLAST
experiment, an international effort led by NASA for a gamma-ray telescope to
launch in 2006, chose HepRep to provide a flexible, extensible and maintainable
framework for their event display without tying their users to any one graphics
application. To support HepRep in their GUADI infrastructure, GLAST developed a
HepRep filler and builder architecture. The architecture hides the details of
XML and CORBA in a set of base and helper classes allowing physics experts to
focus on what data they want to represent. GLAST has two GAUDI services:
HepRepSvc, which registers HepRep fillers in a global registry and allows the
HepRep to be exported to XML, and CorbaSvc, which allows the HepRep to be
published through a CORBA interface and which allows the client application to
feed commands back to GAUDI (such as start next event, or run some GAUDI
algorithm). GLAST's HepRep solution gives users a choice of client
applications, WIRED (written in Java) or FRED (written in C++ and Ruby), and
leaves them free to move to any future HepRep-compliant event display.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 9 pages pdf, 15 figures. PSN THLT00
In-Cylinder Pressure Estimation from Rotational Speed Measurements via Extended Kalman Filter
Real-time estimation of the in-cylinder pressure of combustion engines is crucial to detect failures and improve the performance of the engine control system. A new estimation scheme is proposed based on the Extended Kalman Filter, which exploits measurements of the engine rotational speed provided by a standard phonic wheel sensor. The main novelty lies in a parameterization of the combustion pressure, which is generated by averaging experimental data collected in different operating points. The proposed approach is validated on real data from a turbocharged compression ignition engine, including both nominal and off-nominal working conditions. The experimental results show that the proposed technique accurately reconstructs the pressure profile, featuring a fit performance index exceeding 90% most of the time. Moreover, it can track changes in the engine operating conditions as well as detect the presence of cylinder-to-cylinder variations
Time-of-arrival formalism for the relativistic particle
A suitable operator for the time-of-arrival at a detector is defined for the
free relativistic particle in 3+1 dimensions. For each detector position, there
exists a subspace of detected states in the Hilbert space of solutions to the
Klein Gordon equation. Orthogonality and completeness of the eigenfunctions of
the time-of-arrival operator apply inside this subspace, opening up a standard
probabilistic interpretation.Comment: 16 pages, no figures, uses LaTeX. The section "Interpretation" has
been completely rewritten and some errors correcte
Simulations of Galactic Cosmic Ray Impacts on the Herschel/PACS bolometer Arrays with Geant4 Code
The effects of the in-flight behaviour of the bolometer arrays of the
Herschel/PACS instrument under impacts of Galactic cosmic rays are explored.
This instrument is part of the ESA-Herschel payload, which will be launched at
the end of 2008 and will operate at the Lagrangian L2 point of the Sun-Earth
system. We find that the components external to the detectors (the spacecraft,
the cryostat, the PACS box, collectively referred to as the `shield') are the
major source of secondary events affecting the detector behaviour. The impacts
deposit energy on the bolometer chips and influence the behaviour of nearby
pixels. 25% of hits affect the adjacent pixels. The energy deposited raises the
bolometer temperature by a factor ranging from 1 to 6 percent of the nominal
value. We discuss the effects on the observations and compare simulations with
laboratory tests.Comment: Experimental Astronomy, 2008, in pres
Positive-Operator-Valued Time Observable in Quantum Mechanics
We examine the longstanding problem of introducing a time observable in
Quantum Mechanics; using the formalism of positive-operator-valued measures we
show how to define such an observable in a natural way and we discuss some
consequences.Comment: 13 pages, LaTeX, no figures. Some minor changes, expanded the
bibliography (now it is bigger than the one in the published version),
changed the title and the style for publication on the International Journal
of Theoretical Physic
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