Search results for "Axia"
showing 10 items of 638 documents
Rounding of Phase Transitions in Cylindrical Pores
2010
Phase transitions of systems confined in long cylindrical pores (capillary condensation, wetting, crystallization, etc.) are intrinsically not sharply defined but rounded. The finite size of the cross section causes destruction of long range order along the pore axis by spontaneous nucleation of domain walls. This rounding is analyzed for two models (Ising/lattice gas and Asakura-Oosawa model for colloid-polymer mixtures) by Monte Carlo simulations and interpreted by a phenomenological theory. We show that characteristic differences between the behavior of pores of finite length and infinitely long pores occur. In pores of finite length a rounded transition occurs first, from phase coexiste…
Dynamic Analysis for Axially Moving Viscoelastic Poynting–Thomson Beams
2015
This paper is concerned with dynamic characteristics of axially moving beams with the standard linear solid type material viscoelasticity. We consider the Poynting–Thomson version of the standard linear solid model and present the dynamic equations for the axially moving viscoelastic beam assuming that out-of-plane displacements are small. Characteristic behaviour of the beam is investigated by a classical dynamic analysis, i.e., we find the eigenvalues with respect to the beam velocity. With the help of this analysis, we determine the type of instability and detect how the behaviour of the beam changes from stable to unstable.
Plenary talk - non coaxial force and inductance calculations for bitter coils and coils with uniform radial current distributions
2011
Recently the Bessel function approach to calculating the magnetic fields of coils has been used to calculate the mutual inductance and the force between two non coaxial thick cylindrical coils with parallel axes and uniform radial current distributions. This method can also be applied to calculate the force and inductance between an ordinary coil and a Bitter coil, or between two bitter coils, not necessarily coaxial. Bitter coils give a simpler case of the method, and it is possible to solve analytically for the magnetic field of a bitter disk.
Exact solutions for the mutual inductance of circular coils and elliptic coils
2012
An exact solution is presented for the mutual inductance between general noncoaxial thin circular and elliptic coils with parallel axes. The thin coil solution is given as an angular integral of an elliptic integral expression. In addition, for the coaxial case, an exact solution is given for the mutual inductance of a thick circular coil and a thick elliptic coil. The elliptic coil is such that the coil thickness is the same along both elliptic semi-axes. The thick coil solution is given as an integral of an expression involving Bessel and Struve functions. Extensive numerical results for sample geometries are given for both solutions, which are cross checked against each other in the limi…
Non coaxial force and inductance calculations for bitter coils and coils with uniform radial current distributions
2011
Recently the Bessel function approach to calculating the magnetic fields of coils has been used to calculate the mutual inductance and the force between two non coaxial thick cylindrical coils with parallel axes and uniform radial current distributions. This method can also be applied to calculate the force and inductance between an ordinary coil and a Bitter coil, or between two bitter coils, not necessarily coaxial. Bitter coils give a simpler case of the method, and it is possible to solve analytically for the magnetic field of a bitter disk.
Neutrino induced weak pion production off the nucleon and coherent pion production in nuclei at low energies
2009
We present a microscopic model for neutrino induced one-pion production off the nucleon and its implementation for the purpose of calculating coherent pion production in nuclei. We further criticize the use of the Rein--Sehgal model for coherent pion production by low energy neutrinos. In particular, we show how the approximations in that model give rise to a much flatter differential cross section in the $\eta=E_\pi(1-\cos\theta_\pi)$ variable. We discuss the limitations intrinsic to any approach based on the partial conservation of the axial current hypothesis and the inability of such models to properly determine the angular distribution of the outgoing pion with respect to the direction…
On the Azimuthal Stability of Shock Waves around Black Holes
1998
Analytical studies and numerical simulations of time dependent axially symmetric flows onto black holes have shown that it is possible to produce stationary shock waves with a stable position both for ideal inviscid and for moderately viscous accretion disks. We perform several two dimensional numerical simulations of accretion flows in the equatorial plane to study shock stability against non-axisymmetric azimuthal perturbations. We find a peculiar new result. A very small perturbation seems to produce an instability as it crosses the shock, but after some small oscillations, the shock wave suddenly transforms into an asymmetric closed pattern, and it stabilizes with a finite radial extent…
Mathematical background of the Riga dynamo experiment
2013
The Riga dynamo experiment is a laboratory model of the natural process that is responsible for all environmental magnetic-fields which are generated without human interference. This applies to the field of the Earth, the Sun, stars, and even galaxies which are produced by intense motions of large volumes of good electro-conducting fluids. For our experiment, we use molten sodium – the best liquid electro-conductor available in the laboratory. Approximately 2 m3 of molten sodium are filled into a prolonged cylinder, at the top of which rotates a propeller powered by 200 kW from two motors. The cylinder is divided by thin coaxial inner walls into three parts: in the inner tube the propeller …
Measurements with a hybrid detector prototype composed of a MOS CCD and a CZT spectrometer
2008
The scientific objectives of the future X-ray astronomy instruments require new type of focusing telescopes able to extend the observational range starting from 0.1 keV at least up to 100 keV to solve crucial question concerning the nature of the high energy emission. A challenging technology to extend the classical grazing incidence range to higher energy is today offered by the development of multilayer optics that are effective as X-ray concentrators between few keV up to 100 keV. A useful arrangement for this type of mission concept can foresee the soft (e.g. 0.1-10 keV) X-ray optics nested and coaxial with the hard-X mirrors. The focal plane of the telescope shall operate on a very wid…
Geometric efficiency for a parallel-surface source and detector system with at least one axisymmetric surface
2007
Abstract An exact and numerically friendly method is given to calculate the geometric efficiency G of a planar radiation source and cosine detector system. Either the source or the detector, but not necessarily both, must have axial symmetry. For two non-coaxial disks the results are in exact agreement with a recent generalization of Ruby's formula for G. Detailed formulas and sample numerical results are given for a disk combined with rectangles and triangles. A disk and a general polygon can be solved by dividing the polygon into triangles. The method can also be applied to electrical inductance calculations and a solution recently given for the inductance of circular and elliptic loops c…