1,721,251 research outputs found
Nonlinear elliptic Dirichlet problems in exterior domains: the role of geometry and topology of the domain
No full textImpact of Bias Temperature Instability (BTI) Aging Phenomenon on Clock Deskew Buffers
No full textIn this paper we analyze the effect of the Bias Temperature Instability (BTI) aging phenomenon on the delay of deskew buffers employed in high performance microprocessors. Our analysis shows that, during circuit lifetime, the delay induced by BTI on each deskew buffer within the microprocessor can be significantly different, depending on how each deskew buffer is configured after fabrication (to compensate clock skews occurring during the fabrication process) and the operating temperature. Therefore, we show that even if deskew buffers compensate skews among clock signals after fabrication, their different level of degradation during circuit lifetime can generate significant skews between clock signals after only some month of circuit operation in the field. Moreover, the variations in the delay of deskew buffers due to BTI can exceed the maximum compensation range enabled by such schemes, thus making skew compensation during circuit lifetime ineffective. Finally, we propose a simple mathematical model enabling to estimate the maximum skew among clock signals during the chip lifetime. The model can be used to activate proactive compensation approaches (e.g., clock frequency reduction) allowing to avoid malfunctions caused by an excessive skew among clock signals generated by BTI degradation of the deskew buffers
GRBs, SGRs by UHE leptons showering, blazing and re-brightening by precessing Gamma Jets in-off axis
No full textA list of questions regarding Gamma Ray Bursts (GRBs) and Soft Gamma Repeaters (SGRs) remain unanswered within the Fireball-cone and Magnetar explosive scenarios. A persistent, thin (less than micron-sr solid angle) precessing and spinning gamma jet, with a power output comparable to the progenitor supernova (SN) or XRay pulsar, may explain these issues. The precessing jets may have a few hours characteristic decay time, while their decreasing intensity follow a power law for thousands of years. The orientation of the spinning and precessing beam respect to the line of sight plays a key role : the farthest GRB events in widest cosmic volumes correspond generally to a very narrow and on-axis beam, while for the nearest ones sources are mostly observable off-axis. Consequentely the far ones are the hardest and the most bright and viceversa nearest one are mostly softer and longest ones as in Amati correlation. We expect that nearby off-axis GRBs would be accompanied by a chain of OT and radio bumps as in GRB030329-SN2003 and latest GRB060218-SN2006 events. Delayed blazing jets are observable in the local universe as X-Ray Flahes (XRFs) or short GRBs often as orphan afterglow event, and at closer distances as SGRs and anomalous X-ray Pulsars AXRPs. The gamma jet is originated by ultra-relativistic electron pairs showering via Synchrotron (or Inverse Compton) radiation. The electron pairs escape from the inner SN core thanks to a more penetrating couriers, the relativistic PeV muon pairs, themselves secondaries of inner UHE hadron jets. They are 'transparent' through the SN shells of matter and lights; they decay far away in to electron pairs (and later on) in gamma and neutrinos jets. Then GRBs (and SGRs) are not the most explosive event of the Universe, but just the most beamed ones
Energy instability and overdetermined elliptic problems in cones and cylinders: an approach via domain variations
Full text linkIn this thesis, we study semilinear elliptic problems in domains
that are constrained to be inside a fixed unbounded open set C, with appropriate boundary
conditions. Our aim is to understand how the geometry of C selects domains in which
positive solutions of the equation have special properties, mainly related to notions of
symmetry. Our arguments are primarily based on analyzing how the energy of a positive
solution in a domain varies when the domain moves inside C. We first consider the case
where C is generic. We show how to define an energy functional T when the equation
possesses more than one solution and compute the domain derivative of T. In the case
when C is a cone or a cylinder, we show that some special domains may be unstable
as critical points to the energy shape functional. This opens room for the search for
nonsymmetric domains with the same special properties, to be found, for example, by
local minimization of the energy functional. This is done by analyzing the sign of the
second derivative of the energy functional to understand the stability/instability of its
critical domains. Furthermore, we show that in a special class of domains, namely bounded
cylinders, solutions other than the one-dimensional ones do exist, under fairly general
assumptions on the nonlinearity. This is accomplished by means of bifurcation theory
and Morse index comparison
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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