3,728 research outputs found
Existence theorems in the geometrically non-linear 6-parametric theory of elastic plates
In this paper we show the existence of global minimizers for the
geometrically exact, non-linear equations of elastic plates, in the framework
of the general 6-parametric shell theory. A characteristic feature of this
model for shells is the appearance of two independent kinematic fields: the
translation vector field and the rotation tensor field (representing in total 6
independent scalar kinematic variables). For isotropic plates, we prove the
existence theorem by applying the direct methods of the calculus of variations.
Then, we generalize our existence result to the case of anisotropic plates. We
also present a detailed comparison with a previously established Cosserat plate
model.Comment: 19 pages, 1 figur
Raman spectroscopy, a non-destructive solution to the study of glass and its alteration
This paper presents the potential of Raman spectroscopy, a non-destructive technique which can be applied in-situ, for the analyses of glass and their alteration. Recent analytical developments are summarised for different glass composition and practical examples are given. The paper describes how to extract compositional information from the glass, first based on the spectra profile to distinguish rapidly alkali silicate from alkaline-earth alkali silicate and lead alkali silicate glass, then using the spectral decomposition and correlations to extract quantitative data. For alkali silicate glasses, that are most prone to alteration, the spectral characteristics are described to interpret the alteration process (selective leaching or dissolution of the glass) from the Raman spectra of the altered glass. These developments have greatly widened the potential of the technique and supplement well its ability to measure the thickness of the altered layer and identify the crystalline deposits
The Multi-Colored Hot Interstellar Medium of "The Antennae" Galaxies (NGC 4038/39)
We report the results of the analysis of the extended soft emission
discovered in the Chandra ACIS pointing at the merging system NGC 4038/39 (the
Antennae). We present a `multi-color' X-ray image that suggests both extensive
absorption by the dust in this system, peaking in the contact region, as well
as variations in the temperature of different emitting regions of the hot
interstellar medium (ISM). Spectral fits to multi-component thermal emission
models confirm this picture and give a first evaluation of the parameters of
the hot plasma. We compare the diffuse X-ray emission with radio continuum
(6cm), HI, CO, and H images to take a first look at the multi-phase ISM
of the Antennae galaxies. We find that the hot (X-ray) and cold (CO) gas have
comparable thermal pressures in the two nuclear regions. We also conclude that
the displacement between the peak of the diffuse X-ray emission in the north of
the galaxy system, towards the inner regions of the northern spiral arm (as
defined by H, radio continuum and HI), could result from ram pressure
of infalling HI clouds.Comment: Accepted by Ap
Study of led lamp power supply
В данной статье исследуется источник питания светодиодного светильника с высокимкоэффициентом мощности. Использована микросхема корректора коэффициента мощности компании STMicroelectronics L6561 в обратноходовой топологии. С помощью этой микросхемы упрощается построение источника питания, учитывая стандарты энергосбережения и требования к уровню вносимых в питающую сеть искажений.In this article, we investigate the LED lamp power supply with a high power factor. To implement this, the power factor corrector of STMicroelectronics L6561 is used in the fly-back topology. With the help of this IC simplifies the construction of the power supply, considering energy-efficiency standards and requirements for the level introduced into the mains distortion.Fir filter design using frequency sampling method
Pair decay width of the Hoyle state and carbon production in stars
Electron scattering off the first excited 0+ state in 12C (the Hoyle state)
has been performed at low momentum transfers at the S-DALINAC. The new data
together with a novel model-independent analysis of the world data set covering
a wide momentum transfer range result in a highly improved transition charge
density from which a pair decay width Gamma_pi = (62.3 +- 2.0) micro-eV of the
Hoyle state was extracted reducing the uncertainty of the literature values by
more than a factor of three. A precise knowledge of Gamma_pi is mandatory for
quantitative studies of some key issues in the modeling of supernovae and of
asymptotic giant branch stars, the most likely site of the slow-neutron
nucleosynthesis process.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
The Luminous Starburst Ring in NGC 7771: Sequential Star Formation?
Only two of the twenty highly luminous starburst galaxies analyzed by Smith
et al. exhibit circumnuclear rings of star formation. These galaxies provide a
link between 10^11 L_sun systems and classical, less-luminous ringed systems.
We report the discovery of a near-infrared counterpart to the nuclear ring of
radio emission in NGC 7771. A displacement between the ~10 radio bright clumps
and the ~10 near-infrared bright clumps indicates the presence of multiple
generations of star formation. The estimated thermal emission from each radio
source is equivalent to that of ~35000 O6 stars. Each near-infrared bright knot
contains ~5000 red supergiants, on average. The stellar mass of each knot is
estimated to be ~10^7 M_sun. The implied time-averaged star formation rate is
\~40 M_sun per yr. Several similarities are found between the properties of
this system and other ringed and non-ringed starbursts. Morphological
differences between NGC 7771 and the starburst + Seyfert 1 galaxy NGC 7469
suggest that NGC 7771 may not be old enough to fuel an AGN, or may not be
capable of fueling an AGN. Alternatively, the differences may be unrelated to
the presence or absence of an AGN and may simply reflect the possibility that
star formation in rings is episodic.Comment: accepted for publication in The Astrophysical Journal (10 January
1999); 48 pages including 13 figures; AAS LaTe
Quasi-Homogeneous Thermodynamics and Black Holes
We propose a generalized thermodynamics in which quasi-homogeneity of the
thermodynamic potentials plays a fundamental role. This thermodynamic formalism
arises from a generalization of the approach presented in paper [1], and it is
based on the requirement that quasi-homogeneity is a non-trivial symmetry for
the Pfaffian form . It is shown that quasi-homogeneous
thermodynamics fits the thermodynamic features of at least some
self-gravitating systems. We analyze how quasi-homogeneous thermodynamics is
suggested by black hole thermodynamics. Then, some existing results involving
self-gravitating systems are also shortly discussed in the light of this
thermodynamic framework. The consequences of the lack of extensivity are also
recalled. We show that generalized Gibbs-Duhem equations arise as a consequence
of quasi-homogeneity of the thermodynamic potentials. An heuristic link between
this generalized thermodynamic formalism and the thermodynamic limit is also
discussed.Comment: 39 pages, uses RevteX. Published version (minor changes w.r.t. the
original one
Political brand identity: an examination of the complexities of Conservative brand and internal market engagement during the 2010 UK General Election campaign
This paper seeks to build an understanding of the importance of internal communications when building a strong political brand. Using Kapferer’s brand prism as a conceptual framework, the paper explores UK Conservative Party members’ attitudes towards the development of the Conservative brand as personified by David Cameron. There are clear implications for political strategists as the findings suggest that it is crucial to engage the internal market in the co-creation of the marketing communications strategy for as brand evangelists they interpret the brand promise at the local level
Instanton dominance of topological charge fluctuations in QCD?
We consider the local chirality of near-zero eigenvectors from Wilson-Dirac
and clover improved Wilson-Dirac lattice operators as proposed recently by
Horv\'ath et al. We studied finer lattices and repaired for the loss of
orthogonality due to the non-normality of the Wilson-Dirac matrix. As a result
we do see a clear double peak structure on lattices with resolutions higher
than 0.1 fm. We found that the lattice artifacts can be considerably reduced by
exploiting the biorthogonal system of left and right eigenvectors. We conclude
that the dominance of instantons on topological charge fluctuations is not
ruled out by local chirality measurements.Comment: 10 pages, 6 figure
Maternal Attachment and Children’s Quality of Life: The Mediating Role of Self-compassion and Parenting Stress
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