Notes on static cylindrical shells

Static cylindrical shells made of various types of matter are studied as sources of the vacuum Levi-Civita metrics. Their internal physical properties are related to the two essential parameters of the metrics outside. The total mass per unit length of the cylinders is always less than 1/4. The results are illustrated by a number of figures.Comment: 14 pages, 8 figure

An Application of Kerr Blackhole Fly-Wheel Model to Statistical Properties of QSOs/AGNs

The aim of this work is to demonstrate the properties of the magnetospheric model around Kerr blackholes (BHs), so-called the fly-wheel (rotation driven) model. The fly-wheel engine of the BH-accretion disk system is applied to the statistics of QSOs/AGNs. In the model, the central BH is assumed to be formed at $z \sim 10^2$ and obtains nearly maximum but finite rotation energy ($\sim$ extreme Kerr BH) at the formation stage. The inherently obtained rotation energy of the Kerr BH is released through an magnetohydrodynamic process. This model naturally leads finite lifetime of AGN activity. Nitta et al. (1991) clarified individual evolution of Kerr BH fly-wheel engine which is parametrized by BH mass, initial Kerr parameter, magnetic field near the horizon and a dimension-less small parameter. We impose a statistical model for the initial mass function (IMF) of ensemble of BHs by the Press-Schechter formalism. By the help of additional assumptions, we can discuss the evolution of the luminosity function and the spatial number density of QSOs/AGNs.Comment: 12 pages, 7 figures Fig.7 has been replace

Excavations and the afterlife of a professional football stadium, Peel Park, Accrington, Lancashire: towards an archaeology of football

Association football is now a multi-billion dollar global industry whose emergence spans the post-medieval to the modern world. With its professional roots in late 19th-century industrial Lancashire, stadiums built for the professionalization of football first appear in frequency in the North of England. While many historians of sport focus on consumerism and ‘topophilia’ (attachment to place) regarding these local football grounds, archaeological research that has been conducted on the spectator experience suggests status differentiation within them. Our excavations at Peel Park confirm this impression while also showing a significant afterlife to this stadium, particularly through children’s play

Risk factors of migraine-related brain white matter hyperintensities: an investigation of 186 patients

Brain white matter hyperintensities are more prevalent in migraine patients than in the general population, but the pathogenesis and the risk factors of these hyperintensities are not fully elucidated. The authors analyzed the routine clinical data of 186 migraine patients who were referred to the Outpatient Headache Department of the Department of Neurology, Medical School, University of Pécs, Hungary between 2007 and 2009: 58 patients with white matter hyperintensities and 128 patients without white matter hyperintensities on 3 T MRI. Significant associations between the presence of white matter hyperintensities and longer disease duration (14.4 vs. 19.9 years, p = 0.004), higher headache frequency (4.1 vs. 5.5 attacks/month, p = 0.017), hyperhomocysteinemia (incidence of hyperintensity is 9/9 = 100%, p = 0.009) and thyroid gland dysfunction (incidence of hyperintensity is 8/14 = 57.1%, p = 0.038) were found. These data support the theory that both the disease duration and the attack frequency have a key role in the formation of migraine-related brain white matter hyperintensities, but the effects of comorbid diseases may also contribute to the development of the hyperintensities

Learning from AI: New Trends in Database Technology

With the steadily increasing demand for user-oriented systems, new trends in database technology have evolved outside of the scope of the traditional data models. The authors are concentrated in this article on two closely related efforts: The incorporation of more semantic modelling capabilities into database models, and the development of better user environment, which include user friendly interfaces and support different user views of the content and organization of the dat

Méthode pratique de calcul de la densité spectrale de puissance de signaux codés

La connaissance de la répartition en fréquence de la puissance des signaux numériques codés est un facteur important de la conception des codages binaire à signal. Les impératifs peuvent être, par exemple, de s'affranchir de composante continue et de concentrer le maximum de puissance dans une certaine bande. L'article expose un moyen pratique, facile à mettre en oeuvre sur calculateur numérique, de calcul de la densité spectrale de puissance de signaux codés. La description de la procédure de codage binaire à signal par un graphe facilite le calcul; certaines propriétés des chaînes de Markov permettent alors d'obtenir fonction d'autocorrélation et densité spectrale de puissance. En fin d'article, on rappelle comment étendre ces résultats à une porteuse modulée en phase par un signal numérique

Méthode de prévision de la qualité d'une liaison hertzienne numérique : version 02

On présente une méthode de prévision de la qualité d'une liaison hertzienne numérique, dans laquelle la sélectivité en fréquence du canal atmosphérique est prise en compte par l'emploi d'un modèle statistique de propagation. Comme la variation des coefficients d'un tel modèle statistique avec les caractéristiques du bond considéré n'est pas connue à l'heure actuelle, on a complété les quelques mesures disponibles par des hypothèses découlant dans la mesure du possible de considérations physiques. On traite successivement du canal simple et du canal en diversité. La méthode proposée reste en grande partie spéculative et sera affinée au fur et à mesure que de nouveaux résultats de mesure deviendront disponibles. La méthode décrite dans cette note a fait l'objet d'une communication au groupe "faisceaux hertziens" de la CEPT . C'est pourquoi on donne également, en appendice, la version anglaise du texte

Distributed power flow loss minimization control for future grid

In this paper, a novel decentralized algorithm is proposed to minimize power flow loss in a large-scale future grid connecting with many real-time-distributed generation systems by which power flows bi-directionally. The DC-power loss at each link is defined as the product of resistance and the square of current that can be considered as a quadratic flow cost. We employ the notion of tie-sets that reduces the complexity of the power flow loss problem by dividing a power network into a set of loops that forms a linear vector space on which the power loss problem can be formulated as a convex optimization problem. As finding a solution in each tie-set enables global optimization, we realize parallel computing within a system of independent tie-sets by integrating autonomous agents. Simulation results demonstrate the minimization of the power loss on every link by iteratively optimized power flows and show the superiority against the traditional centralized optimization scheme