1,709 research outputs found
Surface Bundles With Non-Zero Signature
In this paper we develop a new technique that yields infinitely many surface
bundles with non-zero signature.Comment: 8 page
Partial Discharge in Electronic Equipments
Tato disertaÄŤnĂ práce se vÄ›nuje studiu částeÄŤnĂ˝ch vĂ˝bojĹŻ (PD) zpĹŻsobenĂ˝ch poklesem spolehlivosti a Ĺľivotnosti elektronickĂ˝ch zaĹ™ĂzenĂ a systĂ©mĹŻ. Diagnostika PD je dnes známá metoda pro vysokĂ© napÄ›tĂ u vysoko-vĂ˝konnĂ˝ch zaĹ™ĂzenĂ. V pĹ™ĂpadÄ› elektronickĂ˝ch zaĹ™ĂzenĂ PD testovánĂ nenĂ ale běžnÄ› pouĹľĂváná metoda, pĹ™estoĹľe je zde takĂ© potenciál pro vysokĂ© elektrickĂ© zatĂĹľenĂ vzhledem k velmi krátkĂ© vzdálenosti. Tato práce je zaměřena na vyšetĹ™ovánĂ PD ÄŤinnosti u elektronickĂ˝ch zaĹ™ĂzenĂ. Bylo navrĹľeno a provedeno pracovištÄ› pro diagnostiku PD v elektronickĂ˝ch zaĹ™ĂzenĂch. PracovnĂ frekvence se pohybuje od nÄ›kolika stovek Hz aĹľ 100 kHz. MaximálnĂ amplituda PD testovanĂ©ho napÄ›tĂ je vyššà neĹľ 10 kV. Navzdory jednoduchĂ© konstrukci toto zaĹ™ĂzenĂ pĹ™inášà vysokou spolehlivost měřenĂ. VĂce neĹľ 300 PD testĹŻ bylo provedeno na rĹŻznĂ˝ch elektronickĂ˝ch zaĹ™ĂzenĂch a elektronickĂ˝ch součástĂ,napĹ™. na planárnĂch transformátorech a elektronickĂ˝ch komponentách pouĹľĂvanĂ˝ch pĹ™i vysoko-napěťovĂ˝ch mÄ›niÄŤĂchThis dissertation thesis is devoted to study of partial discharge (PD) caused decrease of reliability and lifetime of electronic equipments and systems. PD diagnostic is nowadays well known method for high voltage high power equipments but in case of electronic devices PD testing it is not used routinely despite that there is also a potential for high electric load due to extremely short distances. The risk of PD caused failure is here extremely high because of high working frequency and consequently high repetition rate of PD events. Therefore, this work is focused on investigation of PD activity in electronic equipments. The workplace for PD diagnostic in electronic devices based on switched power supply was designed and made. Working frequency ranges from several hundreds of Hertz up to 100 kHz. The maximal amplitude of PD testing voltage is higher than 10 kV. Despite the simple design this equipment brings high repeatability and reliability of measurement. More than 300 PD tests were made on different electronic devices and electronic components, on planar transformers, and on components for voltage gate drivers for use in high voltage power converters. Possibilities of PD tools in investigation and engineering ofd insulation systems were demonstrated.
Construction of Exotic Smooth Structures
In this article, we construct infinitley many simply connected, nonsymplectic
and pairwise nondiffeomorphic 4-manifolds starting from E(n) and applying the
sequence of knot surgery, ordinary blowups and rational blowdown. We also
compute the Seiberg-Witten invariants of these manifolds.Comment: 10 page
Recent results from NA61/SHINE and NA49
Preliminary results on particle spectra and fluctuations in inelastic p+p
interactions measured by NA61/SHINE at the CERN SPS are presented and its
future ion program is discussed. We also show results on the excitation
functions of event-by-event particle ratio fluctuations in central Pb+Pb
collisions from NA49 using a novel approach. We found a dependence of the
results on phase space coverage which appears to explain the reported
difference between measurements of NA49 and those of STAR in central Au+Au
collisions
Singularity links with exotic Stein fillings
In a recent paper of Akhmedov, Etnyre, Mark and Smith, it was shown that
there exist infinitely many contact Seifert fibered 3-manifolds each of which
admits infinitely many exotic (homeomorphic but pairwise non-diffeomorphic)
simply-connected Stein fillings. Here we extend this result to a larger set of
contact Seifert fibered 3-manifolds with many singular fibers and observe that
these 3-manifolds are singularity links. In addition, we prove that the contact
structures induced by the Stein fillings are the canonical contact structures
on these singularity links. As a consequence, we verify a prediction of Andras
Nemethi by providing examples of isolated complex surface singularities whose
links with their canonical contact structures admitting infinitely many exotic
simply-connected Stein fillings. Moreover, for infinitely many of these contact
singularity links and for each positive integer n, we also construct an
infinite family of exotic Stein fillings with fixed fundamental group
.Comment: 14 pages, 4 figures, Journal of Singularities, to appea
Deformation of Singular Fibers of Genus Fibrations and Small Exotic Symplectic -Manifolds
We introduce the -nodal spherical deformation of certain singular fibers
of genus fibrations, and use such deformations to construct various
examples of simply connected minimal symplectic -manifolds with small
topology. More specifically, we construct new exotic minimal symplectic
-manifolds homeomorphic but not diffeomorphic to
,
, and
for
using combinations of such deformations, symplectic blowups, and (generalized)
rational blowdown surgery. We also discuss generalizing our constructions to
higher genus fibrations using -nodal spherical deformations of certain
singular fibers of genus fibrations.Comment: 38 pages, 14 figures. arXiv admin note: text overlap with
arXiv:math/0507006 by other author
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