10,342 research outputs found
Segmentation-assisted detection of dirt impairments in archived film sequences
A novel segmentation-assisted method for film dirt detection is proposed. We exploit the fact that film dirt manifests in the spatial domain as a cluster of connected pixels whose intensity differs substantially from that of its neighborhood and we employ a segmentation-based approach to identify this type of structure. A key feature of our approach is the computation of a measure of confidence attached to detected dirt regions which can be utilized for performance fine tuning. Another important feature of our algorithm is the avoidance of the computational complexity associated with motion estimation. Our experimental framework benefits from the availability of manually derived as well as objective ground truth data obtained using infrared scanning. Our results demonstrate that the proposed method compares favorably with standard spatial, temporal and multistage median filtering approaches and provides efficient and robust detection for a wide variety of test material
Symmetries and the cosmological constant puzzle
We outline the evaluation of the cosmological constant in the framework of
the standard field-theoretical treatment of vacuum energy and discuss the
relation between the vacuum energy problem and the gauge-group spontaneous
symmetry breaking. We suggest possible extensions of the 't Hooft-Nobbenhuis
symmetry, in particular, its complexification till duality symmetry and discuss
the compatible implementation on gravity. We propose to use the discrete
time-reflection transform to formulate a framework in which one can eliminate
the huge contributions of vacuum energy into the effective cosmological
constant and suggest that the breaking of time--reflection symmetry could be
responsible for a small observable value of this constant.Comment: 11 pages, more relevant refs, refining cutoff definition of
cosmological constant + eq.for regularized pressure adde
NASA/FAA helicopter simulator workshop
A workshop was convened by the FAA and NASA for the purpose of providing a forum at which leading designers, manufacturers, and users of helicopter simulators could initiate and participate in a development process that would facilitate the formulation of qualification standards by the regulatory agency. Formal papers were presented, special topics were discussed in breakout sessions, and a draft FAA advisory circular defining specifications for helicopter simulators was presented and discussed. A working group of volunteers was formed to work with the National Simulator Program Office to develop a final version of the circular. The workshop attracted 90 individuals from a constituency of simulator manufacturers, training organizations, the military, civil regulators, research scientists, and five foreign countries
Aerospace medicine and biology: A continuing bibliography with indexes (supplement 323)
This bibliography lists 125 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during April, 1989. Subject coverage includes; aerospace medicine and psychology, life support systems and controlled environments, safety equipment exobiology and extraterrestrial life, and flight crew behavior and performance
Estimating the Counterparty Risk Exposure by using the Brownian Motion Local Time
In recent years, the counterparty credit risk measure, namely the default
risk in \emph{Over The Counter} (OTC) derivatives contracts, has received great
attention by banking regulators, specifically within the frameworks of
\emph{Basel II} and \emph{Basel III.} More explicitly, to obtain the related
risk figures, one has first obliged to compute intermediate output functionals
related to the \emph{Mark-to-Market} (MtM) position at a given time T being a positive, and finite, time horizon. The latter implies an
enormous amount of computational effort is needed, with related highly time
consuming procedures to be carried out, turning out into significant costs. To
overcome latter issue, we propose a smart exploitation of the properties of the
(local) time spent by the Brownian motion close to a given value
The Lagrangian and Hamiltonian Aspects of the Electrodynamic Vacuum-Field Theory Models
We review the modern classical electrodynamics problems and present the
related main fundamental principles characterizing the electrodynamical
vacuum-field structure. We analyze the models of the vacuum field medium and
charged point particle dynamics using the developed field theory concepts.
There is also described a new approach to the classical Maxwell theory based on
the derived and newly interpreted basic equations making use of the vacuum
field theory approach. In particular, there are obtained the main classical
special relativity theory relations and their new explanations. The well known
Feynman approach to Maxwell electromagnetic equations and the Lorentz type
force derivation is also discussed in detail. A related charged point particle
dynamics and a hadronic string model analysis is also presented. We also
revisited and reanalyzed the classical Lorentz force expression in arbitrary
non-inertial reference frames and present some new interpretations of the
relations between special relativity theory and its quantum mechanical aspects.
Some results related with the charge particle radiation problem and the
magnetic potential topological aspects are discussed. The electromagnetic
Dirac-Fock-Podolsky problem of the Maxwell and Yang-Mills type dynamical
systems is analyzed within the classical Dirac-Marsden-Weinstein symplectic
reduction theory. The problem of constructing Fock type representations and
retrieving their creation-annihilation operator structure is analyzed. An
application of the suitable current algebra representation to describing the
non-relativistic Aharonov-Bohm paradox is presented. The current algebra
coherent functional representations are constructed and their importance
subject to the linearization problem of nonlinear dynamical systems in Hilbert
spaces is demonstrated.Comment: 70 p, revie
A trajectory-based understanding of quantum interference
Interference is one of the most fundamental features which characterizes
quantum systems. Here we provide an exhaustive analysis of the interfere
dynamics associated with wave-packet superpositions from both the standard
quantum-mechanical perspective and the Bohmian one.
From this analysis, clear and insightful pictures of the physics involved in
this kind of processes are obtained, which are of general validity (i.e.,
regardless of the type of wave packets considered) in the understanding of more
complex cases where interference is crucial (e.g., scattering problems, slit
diffraction, quantum control scenarios or, even, multipartite interactions). In
particular, we show how problems involving wave-packet interference can be
mapped onto problems of wave packets scattered off potential barriers.Comment: 27 pages, 12 figures (shortened version
East African topography and volcanism explained by a single, migrating plume
Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes. Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa. We devise paleogeographically constrained global models of mantle convection and, based on the evolution of flow in the deepest lower mantle, show that the Afar plume migrated southward throughout its lifetime. The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system (EARS), which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone, over the last ≈45 Myrs. We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate. The models suggest that the Afar plume became weaker as it migrated southwards, consistent with trends observed in the geochemical record
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