3,556 research outputs found
Radiation data definitions and compilation for equipment qualification data bank
Dose definitions, physical properties, mechanical properties, electrical properties, and particle definitions are listed for insulators and dielectrics, elastomeric seals and gaskets, lubricants, adhesives, and coatings
Low-Cost Experiments with Everyday Objects for Homework Assignments
We describe four classical undergraduate physics experiments that were done
with everyday objects and low-cost sensors: mechanical oscillations,
transmittance of light through a slab of matter, beam deformation under load,
and thermal relaxation due to heat loss. We used these experiments to train
students for experimental homework projects but they could be used and expanded
in a variety of contexts: lecture demonstrations, low cost students' labs,
science projects, distance learning courses...Comment: details on students where added : a section dedicated to the student
difficulties and general feedback on this teaching unit. Minor typos were
fixed. Published in Physics Educatio
Vortex-glass transition in superconducting Nb/Cu superlattices
Nb/Cu superconducting superlattices have been fabricated by dc magnetron
sputtering. This system shows a vortex glass transition with critical exponents
similar to high temperatures superconductors exponents. The transition
dymensionality is governed by the superconducting coupling regime. The vortex
glass transition shows a pure two dimensional behavior in decoupled
superlattices and a quasi-two dimensional behavior in the superlattice coupling
regime.Comment: 9 pages, 3 figure
Anisotropic properties of MgB2 by torque magnetometry
Anisotropic properties of superconducting MgB2 obtained by torque
magnetometry are compared to theoretical predictions, concentrating on two
issues. Firstly, the angular dependence of Hc2 is shown to deviate close to Tc
from the dependence assumed by anisotropic Ginzburg-Landau theory. Secondly,
from the evaluation of torque vs angle curves it is concluded that the
anisotropy of the penetration depth gamma_lambda has to be substantially higher
at low temperature than theoretical estimates, at least in fields higher than
0.2 T.Comment: 2 p.,2 Fig., submitted to Physica C (M2S-Rio proceedings); v2: 1 ref
adde
Le Wilinwiga des Mossi (Guiera senegalensis, Lam.), ses usages thérapeutiques indigènes et son application au traitement des diarrhées cholériformes
Non-stationary Rayleigh-Taylor instability in supernovae ejecta
The Rayleigh-Taylor instability plays an important role in the dynamics of
several astronomical objects, in particular, in supernovae (SN) evolution. In
this paper we develop an analytical approach to study the stability analysis of
spherical expansion of the SN ejecta by using a special transformation in the
co-moving coordinate frame. We first study a non-stationary spherical expansion
of a gas shell under the pressure of a central source. Then we analyze its
stability with respect to a no radial, non spherically symmetric perturbation
of the of the shell. We consider the case where the polytropic constant of the
SN shell is and we examine the evolution of a arbitrary shell
perturbation. The dispersion relation is derived. The growth rate of the
perturbation is found and its temporal and spatial evolution is discussed. The
stability domain depends on the ejecta shell thickness, its acceleration, and
the perturbation wavelength.Comment: 16 page
- …