Search results for "liquid"
showing 10 items of 4351 documents
Twist angle determination in liquid crystal displays by location of local adiabatic points
1998
In this work we present a method for the determination of the twist angle of an arbitrary twisted nematic liquid crystal spatial light modulator. The method is based on the location of local adiabatic points, i.e., situations in which the liquid crystal SLM acts only as a rotation device. For these cases, the rotation induced on the polarization of the incident beam is equal to the twist angle. Consequently, the twist angle can be determined with high precision. We show that local adiabatic regime may be achieved in two ways, either by changing the incident beam wavelength, or by applying a voltage to the electrodes of the display. However, the simple model that describes the SLM in the off…
Unsuspended mass of solid particles in stirred tanks
1998
On propose une technique originale pour la determination de la fraction de particules solides non suspendues a des vitesses d'agitation inferieures a N js . La technique repose sur le concept des systemes jumeles et est completee par une technique de tracage et de detection pour la phase solide. Les resultats obtenus avec un reservoir chicane agite par une turbine Rushton, montrent que la fraction de solides ne quittant jamais le fond du reservoir peut etre simplement correlee au rapport entre la vitesse d'agitation et la vitesse de suspension complete de Zwietering. On montre qu'a des vitesses de l'agitateur d'environ 80% de la vitesse de suspension complete de Zwietering, pratiquement tou…
Reconfigurable Shack-Hartmann sensor without moving elements.
2010
We demonstrate wavefront sensing with variable measurement sensitivity and dynamic range by means of a programmable microlens array implemented onto an off-the-shelf twisted nematic liquid crystal display operating as a phase-only spatial light modulator. Electronic control of the optical power of a liquid lens inserted at the aperture stop of a telecentric relay system allows sensing reconfigurability without moving components. Results of laboratory experiments show the ability of the setup to detect both smooth and highly aberrated wavefronts with adequate sensitivity.
Many-body quantum dynamics by adiabatic path-integral molecular dynamics: Disordered Frenkel Kontorova models
2005
The spectral density of quantum mechanical Frenkel Kontorova chains moving in disordered, external potentials is investigated by means of path-integral molecular dynamics. If the second moment of the embedding potential is well defined (roughness exponent ), there is one regime in which the chain is pinned (large masses of chain particles) and one in which it is unpinned (small ). If the embedding potential can be classified as a random walk on large length scales ( ), then the chain is always pinned irrespective of the value of . For , two phonon-like branches appear in the spectra.
The next generation nuclear instruments: AGATA and NEDA, and nuclear structure studies near N=Z line
2017
The first part of this thesis is devoted to the development of a large array of neutron detectors NEDA (NEutron Detector Array) and their conceptual design using Monte-Carlo simulations. Prior to the development of NEDA, the neutron detection with liquid scintillators is discussed in Chapter 2. In Chapter 3, the design criteria and simulations of NEDA are discussed. NEDA aims to build a neutron detector array with high efficiency, based on liquid scintillators. NEDA will be coupled to the high-purity γ-ray detector arrays, like AGATA, EXOGAM, to be used as a trigger or complementary detector in the contemporary nuclear physics experiments, which aim to investigate the structure of the exoti…
Vortex density waves and high-frequency second sound in superfluid turbulence hydrodynamics
2010
In this paper we show that a recent hydrodynamical model of superfluid turbulence describes vortex density waves and their effects on the speed of high-frequency second sound. In this frequency regime, the vortex dynamics is not purely diffusive, as for low frequencies, but exhibits ondulatory features, whose influence on the second sound is here explored.
A Fractional Approach to Non-Newtonian Blood Rheology in Capillary Vessels
2019
In small arterial vessels, fluid mechanics involving linear viscous fluid does not reproduce experimental results that correspond to non-parabolic profiles of velocity across the vessel diameter. In this paper, an alternative approach is pursued introducing long-range interactions that describe the interactions of non-adjacent fluid volume elements due to the presence of red blood cells and other dispersed cells in plasma. These non-local forces are defined as linearly dependent on the product of the volumes of the considered elements and on their relative velocity. Moreover, as the distance between two volume elements increases, the non-local forces decay with a material distance-decaying …
Wellentypen in Helium II-Schichten
1968
In liquid helium two wave modes are possible. Their properties may be analysed by solving the thermohydrodynamical equations under the condition that the tangential component of the normal fluid velocity is vanishing on the walls. In the present paper, these two types of wave propagation are determined for a plane-parallel capillary with the heat conduction and the thermal expansion being neglected and with the width of the capillary being much smaller than the penetration depth of a viscous wave. In particular, the dispersion relations of both, the so called fourth sound and an overdamped mode are calculated. (This overdamped mode may be called fifth wave mode.) The velocity fields can be …
Spin instabilities of infinite nuclear matter and effective tensor interactions
2013
We study the effects of the tensor force, present in modern effective nucleon-nucleon interactions, in the spin instability of nuclear and neutron matter. Stability conditions of the system against certain very low energy excitation modes are expressed in terms of Landau parameters. It is shown that in the spin case, the stability conditions are equivalent to the condition derived from the spin susceptibility, which is obtained as the zero-frequency and long-wavelength limit of the spin response function calculated in the random phase approximation. Zero-range forces of the Skyrme type and finite-range forces of M3Y and Gogny type are analyzed. It is shown that for the Skyrme forces conside…
Neutron Fermi liquids under the presence of a strong magnetic field with effective nuclear forces
2009
Landau's Fermi liquid parameters are calculated for non-superfluid pure neutron matter in the presence of a strong magnetic field at zero temperature. The particle-hole interactions in the system, where a net magnetization may be present, are characterized by these parameters in the framework of a multipolar formalism. We use either zero- or finite-range effective nuclear forces to describe the nuclear interaction. Using the obtained Fermi liquid parameters, the contribution of a strong magnetic field on some bulk magnitudes such as isothermal compressibility and spin susceptibility is also investigated.