12,311 research outputs found
Universality of Einstein Equations for the Ricci Squared Lagrangians
It has been recently shown that, in the first order (Palatini) formalism,
there is universality of Einstein equations and Komar energy-momentum complex,
in the sense that for a generic nonlinear Lagrangian depending only on the
scalar curvature of a metric and a torsionless connection one always gets
Einstein equations and Komar's expression for the energy-momentum complex. In
this paper a similar analysis (also in the framework of the first order
formalism) is performed for all nonlinear Lagrangians depending on the
(symmetrized) Ricci square invariant. The main result is that the universality
of Einstein equations and Komar energy-momentum complex also extends to this
case (modulo a conformal transformation of the metric).Comment: 21 pages, Late
Evaluation of the magnetization direction effects on ferrite PM brushless fractional machines
Permanent magnets are frequently adopted in small brushless machines for automotive applications. Normally anisotropic ferrites, but some research on bonded magnets is being carried on. Several types of magnetization can be proposed, involving different levels of complexity in the magnetization process. In the paper a comparison between parallel and radial magnetization is described, taking into account on one side the major complexity of the radial process and on the other the small power derating of the paralle
PM fractional machines adopting bonded magnets: effect of different magnetizations on the energetic performance
The adoption of Permanent Magnets in small brushless machines for automotive applications is becoming frequent. Some research on bonded magnets is being carried on to substitute the ferrites. In the paper the parallel and radial magnetizations are considered: the different process complexity levels are analyzed and the effects on the iron losses and the energetic performances are evaluated by means of a simulation analysis and its experimental validatio
Science of Recording
In what follows I would like to recommend the creation of a new undergraduate course, or, rather, a brand new academic program, with all its MAs, BAs, and PhD programs, dean and faculty, freshmen and freshwomen, applications, debates on newspapers, government commissions, areas of study, Erasmus programs, facultyâs impact factor, and so on. The name of such a new academic program, or undergraduate course, would be âscience of recordingâ and it would be designed to address the new needs of our society, which, in entering the new century, has to face the challenge of a world that was mistakenly thought to be dominated by communication (and, unfortunately, by all sorts of wannabe orators) and that unexpectedly discovers itself as being dominated by recording. Donât worry, I am just kidding. I have no such intention. My aim is just to illustrate the signi?cance of writing and recording in our world, and to point out that such a significance has been sometimes overlooked, causing perspectival mistakes that, at least in my opinion, should be corrected, and there is no better occasion to start doing it than at a conference on the âPhilosophy of the Information Societyâ. No doubt that our society, and almost certainly every conceivable society, is a society of information: one cannot live without knowing; not even Robinson can do it. A fortiori in a complex society, one cannot live without knowing. It is often thought that that means that we live in a society of communication, both in the sense that communication is necessary for society and in the sense of an unprecedented expansion of communication in our time. I doubt both such contentions. Of course, a society must communicate in order to exist; but communication alone doesnât suf?ce. Indeed it seems a function that is subordinated to something more essential, namely recording. The idea I would like to sketch here is that we live in a society of recording and that this is the possibility condition of a society of communication, and, of course, of information. By saying that we are in a society of recording I just mean that if we look to all the transformations that have characterized our time we ?nd that they have mainly happened in the realm of recording and not in that of communication
Noether Charges, Brown-York Quasilocal Energy and Related Topics
The Lagrangian proposed by York et al. and the covariant first order
Lagrangian for General Relativity are introduced to deal with the (vacuum)
gravitational field on a reference background. The two Lagrangians are compared
and we show that the first one can be obtained from the latter under suitable
hypotheses. The induced variational principles are also compared and discussed.
A conditioned correspondence among Noether conserved quantities, quasilocal
energy and the standard Hamiltonian obtained by 3+1 decomposition is also
established. As a result, it turns out that the covariant first order
Lagrangian is better suited whenever a reference background field has to be
taken into account, as it is commonly accepted when dealing with conserved
quantities in non-asymptotically flat spacetimes. As a further advantage of the
use of a covariant first order Lagrangian, we show that all the quantities
computed are manifestly covariant, as it is appropriate in General Relativity.Comment: 43 pages, 3 figures, PlainTeX fil
LâEnvironmental Kuznets Curve nel Settore dei Rifiuti Solidi Urbani
This paper provides a specific application of the Environmental Kuznets Curve (EKC) theory in order to explain the correlation between income and household waste generation. The model highlights an U-shaped path of income-refuse relationship that verifies the existence of EKC depending on the effort of household recycling and consumption. The existence of delinking can derive by income and other socio economic variables that affect the shape of the curve. This model would be a particular application of the theory of delinking with the intent to be empirically implemented.Environmental Kuznets Curve, Waste Collection, Delinking, Waste policies
Universality of affine formulation in General Relativity theory
Affine variational principle for General Relativity, proposed in 1978 by one
of us (J.K.), is a good remedy for the non-universal properties of the
standard, metric formulation, arising when the matter Lagrangian depends upon
the metric derivatives. Affine version of the theory cures the standard
drawback of the metric version, where the leading (second order) term of the
field equations depends upon matter fields and its causal structure violates
the light cone structure of the metric. Choosing the affine connection (and not
the metric one) as the gravitational configuration, simplifies considerably the
canonical structure of the theory and is more suitable for purposes of its
quantization along the lines of Ashtekar and Lewandowski (see
http://www.arxiv.org/gr-qc/0404018). We show how the affine formulation
provides a simple method to handle boundary integrals in general relativity
theory.Comment: 38 pages, no figures, LaTeX+BibTex, corrected (restructured contents,
one example removed, no additional results, typos fixed) versio
Universities multistakeholder contribution to smart city ecosystem development
Purpose: This paper investigates the mutually advantageous value-driven innovations brought by Universities as a key actor in the development of innovation exploiting Smart City opportunities. The final aim is to under-stand the role, tasks and contribution of Universities in Smart City pro-jects. Methodology: The study followed an exploratory and qualitative meth-odology and consisted of 44 in-depth semi-structured interviews with Smart City experts. The choice of the respondents was adjusted to approve the direct and indirect effect of developing the smart ecosystem in various organizational multistakeholder environments. Results: The study found three main areas in which Universities may con-tribute to Smart City projects: a) knowledge/technology creation and transfer; b) social/societal involvement; c) ecosystem facilita-tor/networking.Implications: This paper offers several implications for different stake-holders such as policy makers, Universitiesâ top managers and firms. Impli-cations for policy managers imply the change in the approach to consumers because most of them do not understand why they need smart solutions. Moreover, it highlights that bureaucracy and lack of an innovative mental-ity kill smart city projects, so the governmental structures should be wired first. Finally, it calls for a huge financial platform (incentives and new fi-nancial mechanisms) and legal changes (legal frameworks should be aligned with peculiarities of Smart Cities).Implications for top managers of Universities are related to the rethink of Universities in smart city innovation ecosystems with the possibility to play an active role. Implications for MNEs and SMEs include that Univer-sities may help in understanding the opportunities around Smart City initi-atives (there is often opacity on the return of investments). At the same time, Universities may help in dealing with public governments and local stakeholders (public and private)
Caroline Ferraris-Besso, Assistant Professor of French
In this first column of the spring semester, Caroline Ferraris-Besso, Assistant Professor of French, shares which recent novel made her laugh out loud, her favorite cookbooks (and favorite brioche recipe!), and works that have inspired her academic writing
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