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6002. Densely continuous forms, pointwise topology and cardinal functions
- Creator:
- Holý, Dušan and Vadovič, Peter
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- locally bounded densely continuous form, topology of pointwise convergence, cardinal function, weight, density, netweight, and cellularity
- Language:
- English
- Description:
- We consider the space $D(X,Y)$ of densely continuous forms introduced by Hammer and McCoy and investigated also by Holá. We show some additional properties of $D(X,Y)$ and investigate the subspace $D^*(X)$ of locally bounded real-valued densely continuous forms equipped with the topology of pointwise convergence $\tau _p$. The largest part of the paper is devoted to the study of various cardinal functions for $(D^*(X),\tau _p)$, in particular: character, pseudocharacter, weight, density, cellularity, diagonal degree, $\pi $-weight, $\pi $-character, netweight etc.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6003. Density of solutions to quadratic congruences
- Creator:
- Prabhu, Neha
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- matematika, mathematics, squarefree number, Dirichlet's theorem, asymptotic density, primes in arithmetic progression, 13, and 51
- Language:
- English
- Description:
- A classical result in number theory is Dirichlet’s theorem on the density of primes in an arithmetic progression. We prove a similar result for numbers with exactly k prime factors for k>1. Building upon a proof by E.M.Wright in 1954, we compute the natural density of such numbers where each prime satisfies a congruence condition. As an application, we obtain the density of squarefree n 6 x with k prime factors such that a fixed quadratic equation has exactly 2k solutions modulo n., Neha Prabhu., and Seznam literatury
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6004. Density profiles of star clusters in the magellanic clouds
- Creator:
- Kontizas, M., Metaxa, M., Chrysovergis, M., and Kontizas, E.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- astrophysics, star clusters, and magellanic clouds
- Language:
- Czech
- Description:
- The observed dynamical parameters of the Magellanic Clouds (MCs) clusters are derived by means of star counts. There are many rich globular, young disk clusters in the MCs with no counterparts in our galaxy. The old clusters were found statistically less extended with systematically smaller total masses than those of the galactic globulars. So it is worth emphasizing that clusters of all ages (from stellar evolution point of view) are detected in the MCs with very large total number of stars and structural parameters characterising the old halo galactic globulars. The radial density profiles of these stellar systems were used for deriving information on their dynamical stage. Some of the clusters indicate mass segregation of post core collapse profiles, giving evidence for a two body relaxation mechanism. Nevertheless some very young clusters show well relaxed profiles with evolutionary ages too short for a two body relaxation mechanism, so that the shape of their profiles is due to their initial relaxation. A number of clusters were found with an unexpected distortion in the outer areas of their density profiles at systematically constant distances to their centres. It is probable that an halo is formed around these clusters giving evidence that the morphology of the MCs may favorite the occurence of such effects.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6005. Density scale height determined from the motion of Dash 2 satellite
- Creator:
- Helali, Y. E. and Tawadraus, M. Y.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- scientific research and density scale height H
- Language:
- Czech
- Description:
- The density scale height H is determined at low as well as high altitude using the equation of change rate of the orbital period of Dash 2 satellite. The computed values of H are compared with these statistical values obtained by Jacchia-Jacchia´s values of H are given up to altitude 2500 km. We extend Jacchia´s values of H up to altitude 3110.7 km since our values of H are computed from altitude 316.7 km to altitude 3110.7 km. Finally a comparison between our values and Jacciha´s values of H at diffenent altitudes and different MJD are given. For higher altitudes, out values of H are much greater than Jadchia´s values while at smaller altitudes, our values are approximately the same as Jacchia´s values.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6006. Density-dependent incompressible fluids with non-Newtonian viscosity
- Creator:
- Guillén-González, F.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- variable density, shear-dependent viscosity, power law, Carreau’s laws, weak solution, strong solution, and periodic boundary conditions
- Language:
- English
- Description:
- We study the system of PDEs describing unsteady flows of incompressible fluids with variable density and non-constant viscosity. Indeed, one considers a stress tensor being a nonlinear function of the symmetric velocity gradient, verifying the properties of $p$-coercivity and $(p-1)$-growth, for a given parameter $p > 1$. The existence of Dirichlet weak solutions was obtained in [2], in the cases $p \ge 12/5$ if $d = 3$ or $p \ge 2$ if $d = 2$, $d$ being the dimension of the domain. In this paper, with help of some new estimates (which lead to point-wise convergence of the velocity gradient), we obtain the existence of space-periodic weak solutions for all $p \ge 2$. In addition, we obtain regularity properties of weak solutions whenever $p \ge 20/9$ (if $d = 3$) or $p \ge 2$ (if $d = 2$). Further, some extensions of these results to more general stress tensors or to Dirichlet boundary conditions (with a Newtonian tensor large enough) are obtained.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6007. Dependence of drag reduction effectiveness on age of the surfactant solution
- Creator:
- Myška, Jiří, Chára, Zdeněk, and Mík, Václav
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- surfactant, drag reduction, surfaktanty, and snižování tření
- Language:
- Slovak
- Description:
- The age of the surfactant solution influences substantially effectiveness of drag reduction in a turbulent flow in tubes. In this paper are shown effects of both the surfactant concentration and the ratio of the surfactant to the compound containing counter ion, and their role in degradation rate at aging. and Stárnutí roztoku surfaktantu (povrchově aktivní látka) má velký vliv na účinnost snížení tření při turbulentním proudění vody v trubce. Byl zkoumán význam jak koncentrace surfaktantu, tak jeho poměru ke složce obsahující protiiont právě s ohledem na stárnutí roztoku.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6008. Dependence of hidden attractors on non-linearity and Hamilton energy in a class of chaotic system
- Creator:
- Zhang, Ge, Wang, Chunni, Alsaedi, Ahmed, Ma, Jun, and Ren, Guodong
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Helmholtz theorem, chaos, hidden attractor, bifurcation, and Hamilton energy
- Language:
- English
- Description:
- Non-linearity is essential for occurrence of chaos in dynamical system. The size of phase space and formation of attractors are much dependent on the setting of nonlinear function and parameters. In this paper, a three-variable dynamical system is controlled by different nonlinear function thus a class of chaotic system is presented, the Hamilton function is calculated to find the statistical dynamical property of the improved dynamical systems composed of hidden attractors. The standard dynamical analysis is confirmed in numerical studies, and the dependence of attractors and Hamilton energy on non-linearity selection is discussed. It is found that lower average Hamilton energy can be detected when intensity of nonlinear function is enhanced. It indicates that non-linearity can decrease the energy cost triggering for dynamical behaviors.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6009. Dependence of the vulnerability index on the heart cycle length
- Creator:
- Juraj Martinka and Katarína Kozlíková
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, srdeční rytmus, heart rate, body surface potential, ventricular gradient, isointegral map, vulnerability index, RR interval, 14, and 612
- Language:
- English
- Description:
- Index of vulnerability is a parameter based on ventricular gradient evaluating the risk of arrhythmia development. The index is derived from isointegral maps of the QT interval. Individual characteristics of isointegral maps are influenced by different factors, which contribute to the relatively high variability among measured parameters of maps in measured subjects. While several electrocardiographic indexes have been introduced, there are only few studies of their dependence on heart rate. In this study we set out to establish the dependence of vulnerability index on the RR interval or heart rate in healthy population. A positive linear correlation between RR intervals and mean and minimum values of vulnerability indexes was found., J. Martinka, K. Kozlíková., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6010. Deposits of Funnel Beaker culture vessels in wells. New materials - new perspectives
- Creator:
- Żurkiewicz, Danuta
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- wells, bog deposits, Funnel Beaker culture, Kuyavia, Neolithic, pottery, studny, bažinná depozita, kultura nálevkovitých pohárů, Kujavy, neolit, and keramika
- Language:
- Czech
- Description:
- This article presents the extraordinary discoveries of ceramic vessel deposits in wells of the Funnel Beaker culture (FBC). Such a custom is observed in all groups of this community but is of particular importance in the Eastern group of the FBC. In central Poland (Kuyavia) specifically, there are many objects of this type compared to older materials of the Linear Pottery culture. The analysis of the local contexts of these finds allows for the hypothesis that the two communities are closely related to be proposed. and Článek pojednává o mimořádných nálezech keramických nádob ve studnách z období kultury nálevkovitých pohárů (KNP). Zvyk ukládání nádob do studní se vyskytuje u všech skupin této kultury, ale zvláště významný je u východní skupiny KNP. Zejména početné nálezy ze středního Polska (Kujavy) dovolují srovnání s podobnými nálezy z doby kultury s lineární keramikou. Analýza lokálních souvislostí těchto nálezů umožňuje navrhnout hypotézu o příbuznosti obou komunit.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public