634 research outputs found
BUNDLE BLOCK ADJUSTMENT WITH CONSTRAINED RELATIVE ORIENTATIONS
Abstract. This paper deals with bundle adjustment with constrained cameras, i.e. where the orientation of certain cameras is expressed relatively to others, and these relative orientations are part of the unknowns. Despite the remarkable interest for oblique multi-camera systems, an empirical study on the effect of enforcing relative orientation constraints in bundle adjustment is still missing. We provide experimental evidence that indeed these constraints improve the accuracy of the results, while reducing the computational load as well. Moreover, we report for the first time in the literature the complete derivation of the Jacobian matrix for bundle adjustment with constrained cameras, to foster other implementations
Statistics of pressure and of pressure-velocity correlations in isotropic turbulence
Some pressure and pressure-velocity correlation in a direct numerical
simulations of a three-dimensional turbulent flow at moderate Reynolds numbers
have been analyzed. We have identified a set of pressure-velocity correlations
which posseses a good scaling behaviour. Such a class of pressure-velocity
correlations are determined by looking at the energy-balance across any
sub-volume of the flow. According to our analysis, pressure scaling is
determined by the dimensional assumption that pressure behaves as a ``velocity
squared'', unless finite-Reynolds effects are overwhelming. The SO(3)
decompositions of pressure structure functions has also been applied in order
to investigate anisotropic effects on the pressure scaling.Comment: 21 pages, 8 figur
Multiscale velocity correlation in turbulence: experiments, numerical simulations, synthetic signals
Multiscale correlation functions in high Reynolds number experimental
turbulence, numerical simulations and synthetic signals are investigated.
Fusion Rules predictions as they arise from multiplicative, almost
uncorrelated, random processes for the energy cascade are tested. Leading and
sub-leading contribution, in the inertial range, can be explained as arising
from a multiplicative random process for the energy transfer mechanisms. Two
different predictions for correlations involving dissipative observable are
also briefly discussed
One-particle irreducible functional approach - a new route to diagrammatic extensions of DMFT
We present an approach which is based on the one-particle irreducible (1PI)
generating functional formalism and includes electronic correlations on all
length-scales beyond the local correlations of dynamical mean field theory
(DMFT). This formalism allows us to unify aspects of the dynamical vertex
approximation (D\GammaA) and the dual fermion (DF) scheme, yielding a
consistent formulation of non-local correlations at the one- and two-particle
level beyond DMFT within the functional integral formalism. In particular, the
considered approach includes one-particle reducible contributions from the
three- and more-particle vertices in the dual fermion approach, as well as some
diagrams not included in the ladder version of D\GammaA. To demonstrate the
applicability and physical content of the 1PI approach, we compare the
diagrammatics of 1PI, DF and D\GammaA, as well as the numerical results of
these approaches for the half-filled Hubbard model in two dimensions.Comment: 36 pages, 12 figures, updated versio
Resonant Superfluidity in an Optical Lattice
We study a system of ultracold fermionic Potassium (40K) atoms in a
three-dimensional optical lattice in the vicinity of an s-wave Feshbach
resonance. Close to resonance, the system is described by a multi-band
Bose-Fermi Hubbard Hamiltonian. We derive an effective lowest-band Hamiltonian
in which the effect of the higher bands is incorporated by a self-consistent
mean-field approximation. The resulting model is solved by means of Generalized
Dynamical Mean-Field Theory. In addition to the BEC/BCS crossover we find a
phase transition to a fermionic Mott insulator at half filling, induced by the
repulsive fermionic background scattering length. We also calculate the
critical temperature of the BEC/BCS-state and find it to be minimal at
resonance.Comment: 19 pages, 3 figure
Bundle Block Adjustment with Constrained Relative Orientations
This paper deals with bundle adjustment with constrained cameras, i.e. where the orientation of certain cameras is expressed relatively to others, and these relative orientations are part of the unknowns. Despite the remarkable interest for oblique multi-camera systems, an empirical study on the effect of enforcing relative orientation constraints in bundle adjustment is still missing. We provide experimental evidence that indeed these constraints improve the accuracy of the results, while reducing the computational load as well. Moreover, we report for the first time in the literature the complete derivation of the Jacobian matrix for bundle adjustment with constrained cameras, to foster other implementations
Influence of age at weaning and nutritive value of weaning diet on growth performance and caecal traits in rabbits
[EN] To investigate the relationship between dietary nutrient concentration and weaning age on growth performance and caecal characteristics of rabbits, a trial was carried out on 64 litters (eight rabbits/litter) comparing two weaning ages (25 vs. 34 d) and two diets (HC: high concentrated and LC: low concentrated diet) offered to the kits from 18 to 34 d of age. At 34 d of age 54 animals per group were caged individually and all were fed the LC diet until 45 d of age. All animals were then fed a standard fattening diet (37% neutral detergent fiber, 3.4% ether extract and 18.0% crude protein on dry matter basis) until slaughter at 80 d. The digestibility trial was performed from 56 to 60 d of age on another group of 16 rabbits (8 per diet). During the experimental period (18-80 d of age), feed intake and animal weights were recorded. Caecal volatile fatty acids were measured at 45 and 80 d of age, while microbiological analysis was performed at 25 and 34 d on healthy suckling rabbits. Digestibility of dry matter, protein, neutral detergent fiber, fat and energy was higher in rabbits fed the HC diet (by 7.7, 7.4, 13.1, 26.7, 10.6%, respectively; P<0.001) than in those fed the LC diet. Growth rate and feed conversion ratio (FCR) from 18 to 34 d improved by 7.7 and 9.5% in rabbits fed HC in comparison to the LC diet, respectively (P¿0.061). Diet offered around weaning did not influence growth rate or FCR from 34 to 80 d of age. Rabbits weaned earlier increased feed intake (by 67.8%) from 25 to 34 d, but reduced growth rate (by 26.8%) compared to animals weaned at 34 d (P<0.001). Early weaning reduced live weight during the entire fattening period (P¿0.018), as well as the FCR (by 4%; P<0.001). Caecal pH was lower at 45 d of age in rabbits weaned at 25 d than in those weaned at 34 d (5.53 vs. 5.83; P=0.019). Treatments did not affect total caecal VFA concentration, but HC diet decreased caecal acetic concentration and increased butyric acid level compared to the LC diet at 45 d (P¿0.001). HC diet tended to reduce caecal counts of Enterobacteriacae (P=0.093), while it did not affect facultative anaerobic bacteria, E. Coli and Costridium spp. The LC diet increased at 25 d the number of Clostridium perfringens in comparison with the HC group at the same age and in comparison with animals fed both two diets at 34 d (P<0.001). The values of E. Coli and Enterobacteriaceae increased (P¿0.008) from 25 to 34 d of age, whereas that of Clostridium spp. decreased. Weaning at 25 d increased mortality from 18 to 34 d compared with rabbits weaned at 34 d (7.02 vs. 2.46%, P=0.017). However, during the fattening period (34-80 d) rabbits weaned earlier showed lower mortality (7.41 vs. 17.6%; P=0.024).This work has been realized within the CUNISVEZZ research project financed by the Agricultural Department
of the Regione Lombardia as part of the 2004 research and development plan, d.g.r. 30/04/2004 n. VII/17326. The authors wish to thank Nicoletta Cesari for her technical assistance.Cesari, V.; Grilli, G.; Ferrazzi, V.; Toschi, I. (2009). Influence of age at weaning and nutritive value of weaning diet on growth performance and caecal traits in rabbits. World Rabbit Science. 17(4):195-205. https://doi.org/10.4995/wrs.2009.64419520517
Diagrammatic routes to nonlocal correlations beyond dynamical mean field theory
Strong electronic correlations pose one of the biggest challenges to solid
state theory. We review recently developed methods that address this problem by
starting with the local, eminently important correlations of dynamical mean
field theory (DMFT). On top of this, non-local correlations on all length
scales are generated through Feynman diagrams, with a local two-particle vertex
instead of the bare Coulomb interaction as a building block. With these
diagrammatic extensions of DMFT long-range charge-, magnetic-, and
superconducting fluctuations as well as (quantum) criticality can be addressed
in strongly correlated electron systems. We provide an overview of the
successes and results achieved---hitherto mainly for model Hamiltonians---and
outline future prospects for realistic material calculations.Comment: 60 pages, 42 figures, replaced by the version to be published in Rev.
Mod. Phys. 201
Heavy particle concentration in turbulence at dissipative and inertial scales
Spatial distributions of heavy particles suspended in an incompressible
isotropic and homogeneous turbulent flow are investigated by means of high
resolution direct numerical simulations. In the dissipative range, it is shown
that particles form fractal clusters with properties independent of the
Reynolds number. Clustering is there optimal when the particle response time is
of the order of the Kolmogorov time scale . In the inertial range,
the particle distribution is no longer scale-invariant. It is however shown
that deviations from uniformity depend on a rescaled contraction rate, which is
different from the local Stokes number given by dimensional analysis. Particle
distribution is characterized by voids spanning all scales of the turbulent
flow; their signature in the coarse-grained mass probability distribution is an
algebraic behavior at small densities.Comment: 4 RevTeX pgs + 4 color Figures included, 1 figure eliminated second
part of the paper completely revise
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