Messanae Universitas Studiorum: No conditions. Results ordered -Date Deposited. 2017-07-22T18:46:30ZEPrintshttp://cab.unime.it/images/sitelogo.pnghttp://cab.unime.it/mus/2012-09-20T06:55:04Z2012-09-20T11:21:15Zhttp://cab.unime.it/mus/id/eprint/615This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6152012-09-20T06:55:04ZTorse forming vector field on a Sasakian manifoldSia $M(\phi,\eta,\xi,g)$ una varietà Sasakiana. Se ammette un "torse forming X" (K. Yano) cioè $\nabla X = \lambda dp + u \otimes X$ (dp: forma di saldatura di M, con 1 << $C^\infty M, u \in \land^1 M$), allora M è fogliettata dalle sotto varietà di dimensione 3, tangenti alle X, \phi X e \xi e la condizione necessaria e sufficiente perchè X sia "exterior concurrent" (R. Rosca) è che u sia chiuso. Vengono inoltre studiate altre proprietà di X, \phi X e \xi
legate all'Algebra di Lie, definita da X.Vito Carfì2012-09-19T10:27:00Z2012-09-20T11:29:14Zhttp://cab.unime.it/mus/id/eprint/679This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6792012-09-19T10:27:00ZConformal invariant operators on Riemmannian manifoldsIn this paper we study the decompositions problem, introducing a (r, r) -tensor algebra, r > 2. of conformal invariant operators, interpreting its elements P like endomorphisms on the vector space of (1, r - 1) -tensors. For geometrical reasons, the emphasis is on the family of conformal projections and on conformal splittings of tensors, generalizing the decomposition of Singer-Thorpe-Nomizu, given for the space of the curvature tensors. The extension of P to the set of (1, r - 1) -tensor fields and to the affine space $\mathcal{A}^1$_r-1$(M)$, generated by the parallel affine spaces of geometrical object fields of type (1, r - 1), having the difference or the skew symmetric part with respect to a pair of indices a (1, r - 1) -tensor field, leads to the problem of conformal decompositions of tensor fields and connections. As application, we study a closed diagram via conformal projections, which reflects the conformal gauge invariance of the exotic conformal Thomas connection and exotic Weyl conformal curvature tensor field. Are obtained invariants for some transformations of geometrical object fields, in particular connections, generalizing the known properties of the Weyl conformal curvature tensor field.
Key words: conformal invariant tensor algebra, conformal decompositions, conformal projections, gauge invariance.
MSC 2000: 53A55, 53B10, 53C99, 15A72Constantin UdristeIulia Elena Hirica2012-09-19T09:00:15Z2012-09-19T09:00:15Zhttp://cab.unime.it/mus/id/eprint/678This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6782012-09-19T09:00:15ZWavelet Estimate of Time SeriesIn this paper a wavelet technique to study time series by discrete wavelet coefficients, is proposed. Since time series are mainly represented by histograms we will use the Haar waveletes and the Haar wavelet interpolation [1,2]. Moreover we propose an improvement (from computational point of view) of the discrete Haar wavelet transform, called reduced Haar wavelet transform [1,2], allowing a local windowing of the transform. Due to their localization property, the wavelet coefficients of the histogram, together with the wavelet coefficients of the generalized derivative of the histogram, allow to study, with high level of accuracy, the rate of change as well as other characteristics of the time series. Numerical experiments with two kind of (financial) time series show the effectiveness of this technique.
AMS Classification: 35A35, 47A58, 65N13, 65F10, 76W05. JEL Classification: C63, E43.
Key words and phrases: Wavelets, Haar function, interpolation, time series.Carlo CattaniArmando Ciancio2012-09-19T08:52:43Z2012-09-19T08:52:43Zhttp://cab.unime.it/mus/id/eprint/676This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6762012-09-19T08:52:43ZPercolative phenomena in branched reverse micellesThe role played by the solvation water molecules on the macroscopically observed solgel transition in lecithin/cyclohexane/water reverse micelles in investigated. The self diffusion properties of both the surfactant and the water molecules entrapped in the micellar cores are investigated by Quasi Elastic Neutron Scattering, while dielectric relaxation and conductivity measurements furnish information on the structural relaxation processes taking place in the system. The obtained results are compared with the experimental indications for AOT/cyclohexane/water systems. The data from lecithin based systems can be interpreted only assuming that, contrary to AOT systems, the water molecules are entrapped at the interfaces without coalescing into an inner water pool. Also the charge transport mechanisms look very different in the two kinds of system. In particular, in the case of lecithin it is shown how the conductivity appears mainly due to inter-micellar bond percolation: it is suggested that the solvated water molecules can induce a change of the surface curvature, in such a way promoting the formation of branch points. The idea of the existence of a percolated network of branched cylindrical micelles agrees with the observed temperature dependence of the system conductivity. The study of the electrorheologic behaviour of the system under electric field confirms the existence of a percolated transient network in the gel phase.Francesco AliottaBarbara Fazio2012-09-19T08:41:41Z2012-09-19T08:41:41Zhttp://cab.unime.it/mus/id/eprint/671This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6712012-09-19T08:41:41ZDynamics of segmental relaxations for cyanurate-containing semi-interpenetrating polymer networksTwo series of semi-interpenetrating polymer networks (semi-IPNs) of the same linear polyurethane (LPU) and two different heterocyclic polymer networks (HPN-1 and HPN-2) based on thermally cured dicyanic ether of Bisphenol-A, were characterized by differential scanning calorimetry (DSC), complex dynamic modulus E* = E' + iE" and mechanical loss tangent (tan $\delta$ = E"/E', where E' and E" are the storage and loss components of the loss modulus, respectively). The temerature dependence of $\alpha_a$ and $\gamma$ relaxations were studied as a function of HPNs content. By the experimental results no large-scale structural heterogeneities were detected in sample with HPN-1. It has been observed that the inclusion of LPU softens both the HPN-1 and HPN-2 rigid networks which, on the contrary, affects the LPU chain motion by restricting the cooperative long-range segmental dynamics. Single glass transitions are observed in semi-IPN-1 which indicate an affinity between LPU and HPN-1 and also a large scale structural homogeneity.
Differently from semi-IPN-1, two glass transitions are observed in semi-IPN-2, where the absence of chemical intermolecular interactions is thought to give rise to a double phase amorphous network, each phase preserving the main morphological characteristics of the pure components.
Keywords: Anelasticity; Internal friction; Anharmonicity
Pacs index: 61.40 km or 62.40+iAntonio BartolottaGaetano Di MarcoFrancesco Farsaci2012-09-19T08:32:55Z2012-09-19T08:32:55Zhttp://cab.unime.it/mus/id/eprint/664This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6642012-09-19T08:32:55Z$S$-Ultralinear algebra in the space of tempered distributionsThe aim of this paper is to introduce some new concepts that provide the space of tempered distributions with others "linear" structures in addition to its natural structure of linear vector space. These new concepts give for the first time a precise mathematical meaning to the concepts of continuum linear superposition used in physics, engineering and in particular to the concept of "basis" in the "Physical Hilbert space" of quantum mechanics.
To this end, we must definte these new concepts and we must establish some their properties. The new concepts are:
1) nets of class $S$
2) operator generated by a $S$-nets of tempered distributions;
3) nets of class $\mathcal{LS}$;
4) ultralinear combinations of a net of class $\mathcal{LS}$;
5) product of two nets of class $\mathcal{LS}$;
6) the $S$-ultralinear span of a net of class $\mathcal{LS}$;
7) $S$-system of ultra generators;
8) $S$-extended linear independence;
9) $S$-ultra-bases;
10) contravariant components with respect to an $S$-ultra basis.
Mathematics Subject Classification (1991): 46F10, 46F99, 47A05, 47N50, 70A05, 70B05, 81P05, 81Q99.
Key words: Linear operator, tempered distribution, basis, quantum system, state, linear superposition, subspace, generators, linear independence, contravariant components.David Carfì2012-09-19T07:40:13Z2012-09-19T07:40:13Zhttp://cab.unime.it/mus/id/eprint/663This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6632012-09-19T07:40:13ZA theorem about the Goldbach hypothesis for secondary school studentsThe Goldbach hypothesis is analysed and a theorem, about it, is deduced. After a short summary of the mathematical background necessary to prove the theorem, this one is introduced and then demonstrated to explain it to secondary schools students.
Keywords: prime numbers, numbers theory, models theory, sets theoryUmberto Lucia2012-09-19T07:36:31Z2012-09-19T07:36:31Zhttp://cab.unime.it/mus/id/eprint/658This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6582012-09-19T07:36:31ZI numeri reali 2
Gli assi
L'assioma della relazione d'ordine totale e della continuità
I realiIn the second article on the real numbers, following the Artin's method, we obtain, in a new way, the field of real numbering adding only the axioms relative to total ordere and continuity.Rosanna Iembo2012-09-19T07:13:39Z2012-09-19T07:13:39Zhttp://cab.unime.it/mus/id/eprint/656This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6562012-09-19T07:13:39ZI numeri reali 1
L'operazione di addizione e di moltiplicazione nel piano affineThis is the first of two articles aimed at presenting the real numbers in a new way.
In the first article we introduce, throught the parallelogramm rule and the trapezium rule, the operations of addition and multiplication in the affine plane.Rosanna Iembo2012-09-19T07:10:14Z2012-09-19T07:10:14Zhttp://cab.unime.it/mus/id/eprint/655This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6552012-09-19T07:10:14ZEffective boundary conditions for the creeping flow of a suspensionWhile the average equations describing a suspension of particles have been continuously improved from year to year, it seems that no such progress has been made concerning the relevant boundary conditions. We here focus on the suspension slip velocity, and show how it can be deduced either from the momentum balance of the fluid phase, or from the momentum conservation of the whole suspension. An important role is played by the modifications of the particle distribution close to the boundaries. We show how to depict that parietal microstructure, using either the number density of particles, or the density of interfaces, or the particles volume fraction. Numerical results have been obtained long ago for dilute suspensions and we collect these pioneering results together with more recent ones obtained for shear flows and sedimentation flows. Experimental results for the slip velocity in non-dilute suspensions are scarce but they agree with one of the theoretical expressions derived here.
Key Words: suspensions of rigid particles, boundary conditions, slip velocity, microstructure close to boundaries.Daniel Lhuillier2012-09-19T07:01:09Z2012-09-19T07:01:09Zhttp://cab.unime.it/mus/id/eprint/653This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6532012-09-19T07:01:09ZOn "photon-like" particles coupled with an electromagnetic fieldThe dynamics of charged, zero rest mass particles acted on by an electromagnetic field is pointed out. If the external field has characteristic curves which are geodesics, then these curves can be reparametrized into solutions of the extended Lorentz equation, which represent charged "photon-like" particles. That is, uniformly moving zero rest mass particles with variable energy (or Planck-Einstein frequency). Simple examples are considered in which the energy goes to zero or infinity in a finite interval of time.Ermenegildo CacceseAngelo Raffaele Pace2012-09-19T06:56:10Z2012-09-19T06:56:21Zhttp://cab.unime.it/mus/id/eprint/652This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6522012-09-19T06:56:10ZPrecessioni regolari di un solido in campo gravitazionaleIn questa nota si dimostra l'esistenza di un'ampia classe di precessioni regolari per un corpo rigido soggetto all'attrazione gravitazionale emanante da un centro fisso, nell'ipotesi che il baricentro del solido descriva una traiettoria appartenente ad un piano contenente il centro di attrazione.Francesco Rigoli2012-09-19T06:52:51Z2012-09-19T06:53:13Zhttp://cab.unime.it/mus/id/eprint/650This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6502012-09-19T06:52:51ZSome remarks about actions of n-dimensional formal groups on algebras of characteristic zeroLet \underline{F} be a commutative formal group of dimension n over a field k of characteristic zero. In some cases, we give the explicit expressions of the endomorphisms $d_a$ associated to the formal group \underline{F}.Giovanni Molica Bisci2012-09-19T06:45:35Z2012-09-20T11:23:14Zhttp://cab.unime.it/mus/id/eprint/648This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/6482012-09-19T06:45:35ZProperties of noetherian rings in terms of their prefinite differential moduleE' noto che se A è un anello commutativo con identità contenente un campo k di caratteristica zero, A verifica buone proprietà derivanti dal suo modulo universale finito dei differenziali $D_k(A)$ (cf [3]).
Poiché, in generale, il modulo $D_k(A)$ non esiste sempre, è di interesse formulare, per un anello locale che già verifica alcune buone proprietà, risultati sul modulo universale prefinito dei differenziali. Tali buone proprietà sono ovviamente verificate dall'anello quando il $D_k(A)$ esiste finito.Mariafortuna Paratore