2,380 research outputs found
Functional calculus for generators of symmetric contraction semigroups
We prove that every generator of a symmetric contraction semigroup on a
-finite measure space admits, for , a H\"ormander-type
holomorphic functional calculus on in the sector of angle
. The obtained angle is optimal.Comment: 26 pages, minor corrections and slight changes of notation. Some
changes in Sections 4, 6 and
Bellman function and linear dimension-free estimates in a theorem of Bakry
By using an explicit Bellman function, we prove a bilinear embedding theorem
for the Laplacian associated with a weighted Riemannian manifold
having the Bakry-Emery curvature bounded from below. The embedding, acting on
the cartesian product of and ,
, involves estimates which are independent of the dimension of the
manifold and linear in . As a consequence we obtain linear dimension-free
estimates of the norms of the corresponding shifted Riesz transform. All
our proofs are analytic.Comment: 16 pages, to appear in Journal of Functional Analysis; identical to
v2 except that the first-named author's address was update
Stability of Ge-related point defects and complexes in Ge-doped SiO_2
We analyze Ge-related defects in Ge-doped SiO_2 using first-principles
density functional techniques. Ge is incorporated at the level of ~ 1 mol % and
above. The growth conditions of Ge:SiO_2 naturally set up oxygen deficiency,
with vacancy concentration increasing by a factor 10^5 over undoped SiO_2, and
O vacancies binding strongly to Ge impurities. All the centers considered
exhibit potentially EPR-active states, candidates for the identification of the
Ge(n) centers. Substitutional Ge produces an apparent gap shrinking via its
extrinsic levels.Comment: RevTeX 4 pages, 2 ps figure
Whitney coverings and the tent spaces for the Gaussian measure
We introduce a technique for handling Whitney decompositions in Gaussian
harmonic analysis and apply it to the study of Gaussian analogues of the
classical tent spaces of Coifman, Meyer and Stein.Comment: 13 pages, 1 figure. Revised version incorporating referee's comments.
To appear in Arkiv for Matemati
SVILUPPO DI UN SISTEMA INDOSSABILE DI MONITORAGGIO DI POSTURA E MOVIMENTO UMANO BASATO SU TECNOLOGIA BLUETOOTH
Oggetto di questa tesi Ăš la progettazione e realizzazione di un sistema indossabile, che con lâutilizzo di accelerometri e tecnologie wireless, sia capace di monitorare il movimento e la postura di una persona. Il nucleo del presente lavoro di tesi Ăš un dispositivo elettronico wireless, microcontrollato, di dimensioni contenute, trasportabile dallâutente, che preleva i segnali digitali modulati PWM da una coppia di accelerometri, posta direttamente sul corpo del soggetto. I dati acquisiti vengono trasmessi e registrati in tempo reale ma anche elaborati al fine di estrarne parametri significativi sulla postura del soggetto sotto esame
Automatic Concept Extraction in Semantic Summarization Process
The Semantic Web offers a generic infrastructure for interchange, integration and creative reuse of structured data, which can help to cross some of the boundaries that Web 2.0 is facing. Currently, Web 2.0 offers poor query possibilities apart from searching by keywords or tags. There has been a great deal of interest in the development of semantic-based systems to facilitate knowledge representation and extraction and content integration [1], [2]. Semantic-based approach to retrieving relevant material can be useful to address issues like trying to determine the type or the quality of the information suggested from a personalized environment. In this context, standard keyword search has a very limited effectiveness. For example, it cannot filter for the type of information, the level of information or the quality of information.
Potentially, one of the biggest application areas of content-based exploration might be personalized searching framework (e.g., [3],[4]). Whereas search engines provide nowadays largely anonymous information, new framework might highlight or recommend web pages related to key concepts. We can consider semantic information representation as an important step towards a wide efficient manipulation and retrieval of information [5], [6], [7]. In the digital library community a flat list of attribute/value pairs is often assumed to be available. In the Semantic Web community, annotations are often assumed to be an instance of an ontology. Through the ontologies the system will express key entities and relationships describing resources in a formal machine-processable representation. An ontology-based knowledge representation could be used for content analysis and object recognition, for reasoning processes and for enabling user-friendly and intelligent multimedia content search and retrieval.
Text summarization has been an interesting and active research area since the 60âs. The definition and assumption are that a small portion or several keywords of the original long document can represent the whole informatively and/or indicatively. Reading or processing this shorter version of the document would save time and other resources [8]. This property is especially true and urgently needed at present due to the vast availability of information. Concept-based approach to represent dynamic and unstructured information can be useful to address issues like trying to determine the key concepts and to summarize the information exchanged within a personalized environment.
In this context, a concept is represented with a Wikipedia article. With millions of articles and thousands of contributors, this online repository of knowledge is the largest and fastest growing encyclopedia in existence.
The problem described above can then be divided into three steps:
âą Mapping of a series of terms with the most appropriate Wikipedia article (disambiguation).
âą Assigning a score for each item identified on the basis of its importance in the given context.
âą Extraction of n items with the highest score.
Text summarization can be applied to many fields: from information retrieval to text mining processes and text display. Also in personalized searching framework text summarization could be very useful.
The chapter is organized as follows: the next Section introduces personalized searching framework as one of the possible application areas of automatic concept extraction systems. Section three describes the summarization process, providing details on system architecture, used methodology and tools. Section four provides an overview about document summarization approaches that have been recently developed. Section five summarizes a number of real-world applications which might benefit from WSD. Section six introduces Wikipedia and WordNet as used in our project. Section seven describes the logical structure of the project, describing software components and databases. Finally, Section eight provides some consideration..
Modeling epidemics by means of the stochastic description of complex systems
The aim of this article is to show a way in which the problem of predicting the evolution of an epidemic may be tackled by describing it in the framework of Boltzmannâs kinetic theory, as it has been developed and applied in the last years to complex systems by a suitable modification of the Boltzmann equation, via a suitable reinterpretation of state variables and the introduction of the notion of «functional subsystems». Accordingly, in this article we model an arbitrary (national) population S as a complex system, split in two functional subsystems, the first containing all single individuals of S and the second containing the «care tools», that are to be meant as available places in hospitals with a suf- ficient number of physicians and of equipments for intensive cares. The state variable on the first subsystem will be the «health state», and the state variable on the other will be the «effectiveness». We shall then write a system of nonlin- ear ordinary differential equations which gives the evolution of the probability distribution on the set of possible values of the health states. By assigning data partly on the basis of plausibility assumptions and partly as estimated from those furnished by institutions of Campania region, the system takes a form allow- ing the numerical simulation of such evolution, which will be performed and presented in a forthcoming paper
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Life Course Effects of Polyvictimization: Associations with Depression and Crime
Exposure to multiple forms of victimization has been shown to have increasingly negative outcomes, but their unique trajectory-setting effects have been largely unexplored. Using a life course approach, this paper examines the trajectory-setting effects of childhood polyvictimization into early adulthood. I use a nationwide sample including 3,652 respondents after cleaning and preparation. Seemingly unrelated regressions were used to predict depression and criminal behavior in childhood and adulthood. Results suggest childhood polyvictimization sets children on a negative trajectory which grows increasingly worse through the life course. Researchers and interventions should take these trajectory-setting effects into account when attempting to aid polyvictims
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