1,723,276 research outputs found
Joint functional calculi and a sharp multiplier theorem for the Kohn Laplacian on spheres
Full text linkLet b be the Kohn Laplacian acting on (0; j)-forms on the unit sphere in Cn. In a recent paper of Casarino, Cowling, Sikora and the author, aspectral multiplier theorem of Mihlin{Hormander type for b is proved in the case 0 < j < n &#x100000; 1. Here we prove an analogous theorem in the exceptionalcases j = 0 and j = n &#x100000; 1, including a weak type (1; 1) endpoint estimate. We also show that both theorems are sharp. The proof hinges on an abstractmultivariate multiplier theorem for systems of commuting operators.<br/
Generalized uncertainty inequalities
Full text linkThe Heisenberg-Pauli-Weyl (HPW) uncertainty inequality on Rn says that,. Let H be a Hilbert space; we obtain inequalities of the form,. for a pair of positive self-adjoint operators T, L on H satisfying a "balance condition" involving certain operator norms of their spectral projectors. This extends a result of Ciatti et al. (Adv Math 215(2):616-625, 2007) since our hypotheses allow growth rates other than polynomial, e.g., exponential ones. As examples of applications, we obtain HPW-type inequalities on Riemannian manifolds, Riemannian symmetric spaces of non-compact type, homogeneous graphs and unimodular Lie groups. © 2009 Springer-Verlag
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Novel Spatial 3-DoF Constant-Force Generator for the Static Balancing of Parallel Robots
No full textA statically-balanced mechanism can remain in indifferent equilibrium at a continuous set of poses while the actuators exert zero work, as the links’ weight is resisted by conservative balancing forces. This can be achieved, for example, by adding counterweights or springs. Studies on gravity balancing frequently target parallel robots, to increase their intrinsic advantages of high stiffness and smaller motor size. Here, it is considered how to balance a 3-DoF kinematic chain for applications on parallel robots, such that the chain generates a constant force on the end-effector. The design does not include counterweights and has most of the auxiliary balancing elements on the fixed base, thus reducing the inertia of moving elements; the motion is transmitted through a lightweight system of gears, pulleys and synchronous belts. The design also leaves greater freedom in the selection of the spring, which (unlike most previous works) may have nonzero free length
Analysis of joint spectral multipliers on Lie groups of polynomial growth
Full text linkWe study the problem of L p-boundedness (1 < p < ∞) of operators of the form m(L 1,·,L n) for a commuting system of self-adjoint left-invariant differential operators L 1,·, L n on a Lie group G of polynomial growth, which generate an algebra containing a weighted subcoercive operator. In particular, when G is a homogeneous group and L 1,·,L n are homogeneous, we prove analogues of the Mihlin-Hörmander and Marcinkiewicz multiplier theorems
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Il Miglioramento Continuo nel Contesto Internazionale: Parlano i Numeri
No full textLe imprese italiane hanno mostrato un crescente interesse verso il Miglioramento Continuo – MC - come strumento fondamentale per poter migliorare le proprie prestazioni. Ma – ci si chiede - nell’implementazione delle pratiche e degli strumenti di MC, quali sono le peculiarità che ad oggi differenziano le imprese italiane rispetto al resto del mondo? E poi: l’impatto che il MC produce sulle prestazioni è analogo per tutte le nazioni o, invece, si differenzia in funzione del paese di appartenenza?
Attingendo alla seconda survey CINet che vede coinvolte 544 imprese che fanno parte di un database internazionale distribuito su 10 paesi, questo articolo ha lo scopo di capire lo status quo del Miglioramento Continuo in Italia rispetto al contesto internazionale
Development of a Multibody-Based Dynamic Model of the Rear Hitch Subsystem of an Agricultural Tractor
Full text linkThis work deals with the implementation of the dynamic model of a subsystem typically present in agricultural tractors, namely a mechanical-hydraulic digital twin of the rear hitch. A multibody model of the rear hitch mechanical subsystem was developed in Simscape Multibody and integrated with the hydraulic system model developed in Simulink. Finally, a preliminary control logic to ensure the correct operation of the device was designed and its performance was assessed through simulations. The first simulation results appear promising
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