Observational Constraints on the Generalized Chaplygin Gas

In this paper we study a quintessence cosmological model in which the dark energy component is considered to be the Generalized Chaplygin Gas and the curvature of the three-geometry is taken into account. Two parameters characterize this sort of fluid, the $\nu$ and the $\alpha$ parameters. We use different astronomical data for restricting these parameters. It is shown that the constraint $\nu \lesssim \alpha$ agrees enough well with the astronomical observations.Comment: Accepted by IJMPD; 18 pages; 10 Figure

Dark energy FRW cosmology - dynamical system reconstruction

We develop a simple method of dark energy reconstruction using a geometrical form of the luminosity-distance relation. In this method the FRW dynamical system with dark energy is reconstructed instead of the equation of state parameter. We give several examples which illustrate the usefulness of our method in fitting the redshift transition from the decelerating to accelerating phase as the value of the Hubble function at the transition.Comment: Talk presented at Spanish Relativity Meeting 2007, Puerto de la Cruz, Tenerife, Spain, 10-14 September 200

Canonical 1-forms on higher order adapted frame bundles

summary:Let $(M,\mathcal{F})$ be a foliated $m+n$-dimensional manifold $M$ with $n$-dimensional foliation $\mathcal{F}$. Let $V$ be a finite dimensional vector space over $\mathbf{R}$. We describe all canonical ({\mathcal{F}}\mbox {\it ol}_{m,n}-invariant) $V$-valued $1$-forms $\Theta \colon TP^r(M,{\mathcal{F}}) \rightarrow V$ on the $r$-th order adapted frame bundle $P^r(M,\mathcal{F})$ of $(M,\mathcal{F})$

The natural affinors on some fiber product preserving gauge bundle functors of vector bundles

summary:We classify all natural affinors on vertical fiber product preserving gauge bundle functors $F$ on vector bundles. We explain this result for some more known such $F$. We present some applications. We remark a similar classification of all natural affinors on the gauge bundle functor $F^*$ dual to $F$ as above. We study also a similar problem for some (not all) not vertical fiber product preserving gauge bundle functors on vector bundles

Determination of stress and strain concentrations in the elastic-plastic materials under bending and torsion

The analysis of stress and strain concentrations of constructional materials subjected to bending and torsion is presented. The known methods of stress determination for any elastic-plastic material assume the linear strain concentration under bending and torsion. Determination of stress and strain concentrations and their presentation as graphs were the main aims of this paper. Five materials were tested. They had different cyclic strain curves, and were loaded by the torsional and bending moments. The results proved a linear character of the strain distribution for any material in the all applied loading range.Визначено розклад напружень і деформацій в перетині проаналізованого елемента вальців та подано графічно за допомогою комп’ютерної моделі. Аналіз п’яти матеріалів та їх кривих циклічного деформування з різними характеристиками за умов кручення та згину показав лінійний характер розкладу деформацій для кожного з них за всіх прикладених навантажень.Определено распределение напряжений и деформаций в сечении проанализированного элемента валков и представлено графически с помощью компьютерной модели. Анализ пяти материалов и их кривых циклического деформирования с разными характеристиками при кручении и изгибе показал линейный характер распределения деформаций для каждого из них при всех приложенных нагрузках

Cosmic acceleration from modified gravity with Palatini formalism

We study new FRW type cosmological models of modified gravity treated on the background of Palatini approach. These models are generalization of Einstein gravity by the presence of a scalar field non-minimally coupled to the curvature. The models employ Starobinsky's term in the Lagrangian and dust matter. Therefore, as a by-product, an exhausted cosmological analysis of general relativity amended by quadratic term is presented. We investigate dynamics of our models, confront them with the currently available astrophysical data as well as against LCDM model. We have used the dynamical system methods in order to investigate dynamics of the models. It reveals the presence of a final sudden singularity. Fitting free parameters we have demonstrated by statistical analysis that this class of models is in a very good agreement with the data (including CMB measurements) as well as with the standard LCDM model predictions. One has to use statefinder diagnostic in order to discriminate among them. Therefore Bayesian methods of model selection have been employed in order to indicate preferred model. Only in the light of CMB data the concordance model remains invincible.Comment: 32 pages, jcappub style, 28 figures, final improved version, to be published in JCA

Dusty Universe viewed by AKARI far infrared detector

We present the results of the analysis of multiwavelength Spectral Energy Distributions (SEDs) of far-infrared galaxies detected in the AKARI Deep Field-South (ADF--S) Survey. The analysis uses a carefully selected sample of 186 sources detected at the 90 $\mu$m AKARI band, identified as galaxies with cross-identification in public catalogues. For sources without known spectroscopic redshifts, we estimate photometric redshifts after a test of two independent methods: one based on using mainly the optical -- mid infrared range, and one based on the whole range of ultraviolet -- far infrared data. We observe a vast improvement in the estimation of photometric redshifts when far infrared data are included, compared with an approach based mainly on the optical -- mid infrared range. We discuss the physical properties of our far-infrared-selected sample. We conclude that this sample consists mostly of rich in dust and young stars nearby galaxies, and, furthermore, that almost 25% of these sources are (Ultra)Luminous Infrared Galaxies. Average SEDs normalized at 90 $\mu$m for normal galaxies (138 sources), LIRGs (30 sources), and ULIRGs (18 galaxies) a the significant shift in the peak wavelength of the dust emission, and an increasing ratio between their bolometric and dust luminosities which varies from 0.39 to 0.73.Comment: 8 pages, 7 figures, published in Earth, Planets and Spac

Knowledge Transfer in Automatic Optimisation of Reconfigurable Designs

This paper presents a novel approach for automatic optimisation of reconfigurable design parameters based on knowledge transfer. The key idea is to make use of insights derived from optimising related designs to benefit future optimisations. We show how to use designs targeting one device to speed up optimisation of another device. The proposed approach is evaluated based on various applications including computational finance and seismic imaging. It is capable of achieving up to 35% reduction in optimisation time in producing designs with similar performance, compared to alternative optimisation methods

Fatigue cracking of aluminium alloy AlZn6Mg0.8Zr subjected to thermomechanical treatment

The paper presents the results of experimental test of the fatigue of aluminium alloy type AlZn6Mg0,8Zr exposed to various low temperature thermomechanical treatment. Basquin’s characteristics of fatigue have been determined in mechanical test on smooth specimens at a simple state of loading in conditions of alternating bending. The tests were carried out on a fatigue test stand constructed by the authors – MZGS 100. The development of fatigue cracking has been described based on metallographic and fractographic investigations of the fractured samples making use of a scanning electron microscope (SEM). The results of qualitative microfractography of the tested samples in the low-cycle temporal range of fatigue strength revealed fractures of the transcrystalline quasi-cleavage type. It has also been found that local effects of intercrystalline brittle cracking of this type do occur