899 research outputs found
A note on the moment map on compact K\"ahler manifolds
We consider compact K\"ahler manifolds acted on by a connected compact Lie
group of isometries in Hamiltonian fashion. We prove that the squared
moment map is constant if and only if the manifold is
biholomorphically and -equivariantly isometric to a product of a flag
manifold and a compact K\"ahler manifold which is acted on trivially by .
The authors do not know whether the compactness of is essential in the main
theorem; more generally it would be interesting to have a similar result for
(compact) symplectic manifolds.Comment: 4 page
Homogeneous Hypercomplex Structures and the Joyce's Construction
We prove that any invariant hypercomplex structure on a homogeneous space where is a compact Lie group is obtained via the Joyce's
construction, provided that there exists a hyper-Hermitian naturally reductive
invariant metric on .Comment: 11 page
Numerical solution of three-dimensional rectangular submerged jets with the evidence of the undisturbed region of flow
The evolution of turbulent rectangular submerged free jets has been
investigated numerically with a two-dimensional (2D) approach by the
present authors and, by using the large eddy simulations (LES) at several
Reynolds numbers. The average numerical results confirmed the presence of
the undisturbed region of flow (URF) located between the slot exit and the
beginning of the potential core region (PCR) previously observed
experimentally at the University of Rome “Tor Vergata” by Gori and
coworkers. The 2D study of the present authors carried out under the
conditions previously investigated in the literature, showed that the URF has
a self-similar behavior, and proposed a new law for the evolution of the
momentum. The present paper extends the LES to three-dimensional (3D)
rectangular submerged free jets, in the range from Re =5,000 to
Re =40,000, showing that the self-similar behavior of URF is also present
in the 3D numerical simulations, as well as in the PCR and in the fully
developed region (FDR)
Herbal Medicine Today: Clinical and Research Issues
Herbal medicine is the use of medicinal plants for prevention and treatment of diseases: it ranges from traditional and popular medicines of every country to the use of standardized and tritated herbal extracts. Generally cultural rootedness enduring and widespread use in a Traditional Medical System may indicate safety, but not efficacy of treatments, especially in herbal medicine where tradition is almost completely based on remedies containing active principles at very low and ultra low concentrations, or relying on magical-energetic principles
A 2d-Numerical Study on Slot Jet Applied to a Wind Turbine as a Circulation Control Technique
The file attached to this record is the author's final peer reviewed version.A study on the feasibility of the Circulation Control
(CC) technique for wind turbines is proposed. The
CC was born in aeronautic field to improve the lift
force on the wings, allowing the short take-off and
landing of aircraft. It consists in blowing air at a
relatively high speed over a rounded trailing edge.
The thin jet of air remains attached to the convex
curved surface, imposing a certain curvature to the
outer streamlines, and, hence, increasing the lift force
of the airfoil. Aim of this study is to numerically
investigate the advantages on a wind turbine, based
on the S809 airfoil, taking into account the energy related
considerations, as the cost of the jet
production. The paper, after a thorough evaluation of
the increase of the generated power, finds that this
technique could be promising in the energy harvesting
aim
Thermophysical parameter estimation of multi-layer walls with stochastic optimization methods
The problem of the estimation of thermal conductivities of multi-layer walls is studied using genetic algorithms and simulated annealing. Parameter estimation is shown for the cases of three- and five- layer walls, comparing the two stochastic approaches and also contrasting them with deterministic gradient-based methods. It is shown how stochastic methods permit better performances than classical ones when initial estimations of parameter values are not available or when the problem becomes complex
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