32,817 research outputs found
Liquid oxygen dicting cleaned by falling film method
Principle of a vertical falling film is used to clean contaminated large diameter and length liquid oxygen /LOX/ cylindrical ducting. The cleaning cycle is performed by flowing trichloroethylene in a falling film down a vertically mounted duct for approximately one hour
Lie point symmetries and the geodesic approximation for the Schr\"odinger-Newton equations
We consider two problems arising in the study of the Schr\"odinger-Newton
equations. The first is to find their Lie point symmetries. The second, as an
application of the first, is to investigate an approximate solution
corresponding to widely separated lumps of probability. The lumps are found to
move like point particles under a mutual inverse-square law of attraction
Scattering of non-uniform incident fields by long cylinders
Copyright University of BremenWe investigate experimentally far-field scattering from cylinders with illumination non-uniform along the axis of the cylinder. Scattered intensity as a function of angle in two orthogonal directions is examined. Variation along the scattering angle is found to be little affected by the illumination profile. However, variation in the transverse direction follows closely the Fourier transform of the illumination pattern and reproduces the angular distribution of the incident wave. These finding apply to circular as well as hexagonal cross-section cylinders
Quantifying Spatiotemporal Chaos in Rayleigh-B\'enard Convection
Using large-scale parallel numerical simulations we explore spatiotemporal
chaos in Rayleigh-B\'enard convection in a cylindrical domain with
experimentally relevant boundary conditions. We use the variation of the
spectrum of Lyapunov exponents and the leading order Lyapunov vector with
system parameters to quantify states of high-dimensional chaos in fluid
convection. We explore the relationship between the time dynamics of the
spectrum of Lyapunov exponents and the pattern dynamics. For chaotic dynamics
we find that all of the Lyapunov exponents are positively correlated with the
leading order Lyapunov exponent and we quantify the details of their response
to the dynamics of defects. The leading order Lyapunov vector is used to
identify topological features of the fluid patterns that contribute
significantly to the chaotic dynamics. Our results show a transition from
boundary dominated dynamics to bulk dominated dynamics as the system size is
increased. The spectrum of Lyapunov exponents is used to compute the variation
of the fractal dimension with system parameters to quantify how the underlying
high-dimensional strange attractor accommodates a range of different chaotic
dynamics
Ferromagnetism or slow paramagnetic relaxation in Fe-doped LiN?
We report on isothermal magnetization, M\"ossbauer spectroscopy, and
magnetostriction as well as temperature-dependent alternating-current (ac)
susceptibility, specific heat, and thermal expansion of single crystalline and
polycrstalline Li(LiFe)N with and .
Magnetic hysteresis emerges at temperatures below K with
coercivity fields of up to T at K and magnetic
anisotropy energies of K (meV). The ac susceptibility is strongly
frequency dependent (--Hz) and reveals an effective energy
barrier for spin reversal of K. The relaxation times
follow Arrhenius behavior for K. For K, however, the
relaxation times of s are only weakly
temperature-dependent indicating the relevance of a quantum tunneling process
instead of thermal excitations. The magnetic entropy amounts to more than
J molK which significantly exceeds ln2, the
value expected for the entropy of a ground state doublet. Thermal expansion and
magnetostriction indicate a weak magneto-elastic coupling in accordance with
slow relaxation of the magnetization. The classification of
Li(LiFe)N as ferromagnet is stressed and contrasted with highly
anisotropic and slowly relaxing paramagnetic behavior.Comment: 12 pages, 10 figure
Magnetic and superconducting phase diagrams in ErNi2B2C
We present measurements of the superconducting upper critical field Hc2(T)
and the magnetic phase diagram of the superconductor ErNi2B2C made with a
scanning tunneling microscope (STM). The magnetic field was applied in the
basal plane of the tetragonal crystal structure. We have found large gapless
regions in the superconducting phase diagram of ErNi2B2C, extending between
different magnetic transitions. A close correlation between magnetic
transitions and Hc2(T) is found, showing that superconductivity is strongly
linked to magnetism.Comment: 5 pages, 4 figure
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