Search results for " degrees"
showing 10 items of 38 documents
Poincaré Surface of Sections, Mappings
2001
We consider a system with two degrees of freedom, which we describe in four-dimensional phase space. In this (finite) space we define an (oriented) two-dimensional surface. If we then consider the trajectory in phase space, we are interested primarily in its piercing points through this surface. This piercing can occur repeatedly in the same direction. If the motion of the trajectory is determined by the Hamiltonian equations, then the n + 1-th piercing point depends only on the nth. The Hamiltonian thus induces a mapping n → n + 1 in the “Poincare surface of section” (PSS). The mapping transforms points of the PSS into other (or the same) points of the PSS. In the following we shall limit …
Plus d'éducation, pour qui, pour quoi ?
2005
La question des "moyens" semble résumer les revendications syndicales des enseignants. Or l'élévation des niveaux de diplôme ne réduit pas les inégalités sociales et scolaires entre les élèves, ni le taux de chômage des jeunes. C'est qu'il faut autrement, et de façon plus politique, poser la question de l'allocation des ressources et de leur évaluation : qui doit bénéficier de plus d'école ?
The KAM Theorem
2016
This theorem guarantees that, under certain assumptions, in the case of a perturbation \(\varepsilon H_{1}(\boldsymbol{J},\boldsymbol{\theta })\) with small enough ɛ, the iterated series for the generator W(θ i 0, J i ) converges (according to Newton’s procedure) and thus the invariant tori are not destroyed. The KAM theorem is valid for systems with two and more degrees of freedom. However, in the following, we shall deal exclusively with the case of two degrees of freedom.
Influence of Geometrical Parameters, Wall Angle and Part Shape on Thickness Reduction of Single Point Incremental Forming
2014
Abstract The aim of this paper is to study the thickness reduction during the whole single point incremental forming process. The experimental setup is realized in such a way that the blank sheet is in the vertical position and forming is done using an anthropomorphic robot with six degrees of freedom. The vertical positioning of the blank sheet allows the on-line visualization using an optical measuring system of the major and minor strains and of the thickness reduction. The wall angle varied between values of 45 0 , 55 0 and 65 0 respectively. The logarithmic major strain and minor strains and logarithmic thickness reduction were analyzed in order to allow a comparison with values obtain…
State Estimation of a Nonlinear Unmanned Aerial Vehicle Model using an Extended Kalman Filter
2008
An Extended Kalman Filter is designed in order to estimate both state variables and wind velocity vector at the same time for a non conventional unmanned aircraft. The proposed observer uses few measurements, obtained by means of either conventional simple air data sensors or a low cost GPS. To cope with the low rate of the GPS with respect to the other sensors, the EKF algorithm has been modified to allow for a dual rate measurement model. State propagation is obtained by means of an accurate six degrees of freedom nonlinear model of the aircraft dynamics. To obtain joint estimation of state and disturbance, wind velocity components are included in the set of the state variables. Both stoc…
Differential geometric least angle regression: a differential geometric approach to sparse generalized linear models
2013
Summary Sparsity is an essential feature of many contemporary data problems. Remote sensing, various forms of automated screening and other high throughput measurement devices collect a large amount of information, typically about few independent statistical subjects or units. In certain cases it is reasonable to assume that the underlying process generating the data is itself sparse, in the sense that only a few of the measured variables are involved in the process. We propose an explicit method of monotonically decreasing sparsity for outcomes that can be modelled by an exponential family. In our approach we generalize the equiangular condition in a generalized linear model. Although the …
Quantum correlations in generalized spin star system
2006
The problem of detecting quantum signatures in the correlations formed in dynamical evolution of quantum bipartite systems receives a lot of attention in current literature. Generally speaking, the occurrence of correlations between two observables of a system does not necessarily reflect nonclassical behaviour. In this paper, the exact dynamics of a pair of uncoupled spins 1/2 interacting with a common spin 1/2 bath is investigated. Starting from a separable initial condition, the ability of the system to develop purely quantum correlations is brought to light. Physical interpretation of the concurrence function as well as a suggestion on how to measure it are given.
(H,ρ)-induced dynamics and large time behaviors
2018
Abstract In some recent papers, the so called ( H , ρ ) -induced dynamics of a system S whose time evolution is deduced adopting an operatorial approach, borrowed in part from quantum mechanics, has been introduced. Here, H is the Hamiltonian for S , while ρ is a certain rule applied periodically (or not) on S . The analysis carried on throughout this paper shows that, replacing the Heisenberg dynamics with the ( H , ρ ) -induced one, we obtain a simple, and somehow natural, way to prove that some relevant dynamical variables of S may converge, for large t , to certain asymptotic values. This cannot be so, for finite dimensional systems, if no rule is considered. In this case, in fact, any …
Particle Filtering for Tracking in 360 Degrees Videos Using Virtual PTZ Cameras
2019
360 degrees cameras are devices able to record spherical images of the environment. Such images can be used to generate views of the scene by projecting the spherical surface onto planes tangent to the sphere. Each of these views can be considered as the output of a virtual PTZ (vPTZ) camera with specific pan, tilt and zoom parameters. This paper proposes to formulate the visual tracking problem as the one of selecting, at each time, the vPTZ camera to foveate on the target from the unlimited set of simultaneously generated vPTZ camera views. Assuming that the selected vPTZ camera is a stochastic variable, the paper proposes to model the posterior distribution of the underlying stochastic p…
Spherically averaged versus angle-dependent interactions in quadrupolar fluids
2008
Employing simplified models in computer simulation is on the one hand often enforced by computer time limitations but on the other hand it offers insights into the molecular properties determining a given physical phenomenon. We employ this strategy to the determination of the phase behaviour of quadrupolar fluids, where we study the influence of omitting angular degrees of freedom of molecules via an effective spherically symmetric potential obtained from a perturbative expansion. Comparing the liquid-vapor coexistence curve, vapor pressure at coexistence, interfacial tension between the coexisting phases, etc., as obtained from both the models with the full quadrupolar interactions and th…