4,888 research outputs found
Three dimensional, axisymmetric cusps without chaos
We construct three dimensional axisymmetric, cuspy density distributions,
whose potentials are of St\"ackel form in parabolic coordinates. As in Sridhar
and Touma (1997), a black hole of arbitrary mass may be added at the centre,
without destroying the St\"ackel form of the potentials. The construction uses
a classic method, originally due to Kuzmin (1956), which is here extended to
parabolic coordinates. The models are highly oblate, and the cusps are "weak",
with the density, , where .Comment: 5 pages, 2 figures, submitted to MNRA
Stellar Dynamics around Black Holes in Galactic Nuclei
We classify orbits of stars that are bound to central black holes in galactic
nuclei. The stars move under the combined gravitational influences of the black
hole and the central star cluster. Within the sphere of influence of the black
hole, the orbital periods of the stars are much shorter than the periods of
precession. We average over the orbital motion and end up with a simpler
problem and an extra integral of motion: the product of the black hole mass and
the semimajor axis of the orbit. Thus the black hole enforces some degree of
regularity in its neighborhood. Well within the sphere of influence, (i)
planar, as well as three dimensional, axisymmetric configurations-both of which
could be lopsided-are integrable, (ii) fully three dimensional clusters with no
spatial symmetry whatsover must have semi-regular dynamics with two integrals
of motion. Similar considerations apply to stellar orbits when the black hole
grows adiabatically. We introduce a family of planar, non-axisymmetric
potential perturbations, and study the orbital structure for the harmonic case
in some detail. In the centered potentials there are essentially two main
families of orbits: the familiar loops and lenses, which were discussed in
Sridhar and Touma (1997, MNRAS, 287, L1-L4). We study the effect of
lopsidedness, and identify a family of loop orbits, whose orientation
reinforces the lopsidedness, an encouraging sign for the construction of
self-consistent models of eccentric, discs around black holes, such as in M31
and NGC 4486B.Comment: to appear in MNRAS, 10 pages, latex, 20 POstScript figure
Response to sub-threshold stimulus is enhanced by spatially heterogeneous activity
Sub-threshold stimuli cannot initiate excitations in active media, but
surprisingly as we show in this paper, they can alter the time-evolution of
spatially heterogeneous activity by modifying the recovery dynamics. This
results in significant reduction of waveback velocity which may lead to spatial
coherence, terminating all activity in the medium including spatiotemporal
chaos. We analytically derive model-independent conditions for which such
behavior can be observed.Comment: 5 pages, 5 figure
WEST-3 wind turbine simulator development
The software developed for WEST-3, a new, all digital, and fully programmable wind turbine simulator is given. The process of wind turbine simulation on WEST-3 is described in detail. The major steps are, the processing of the mathematical models, the preparation of the constant data, and the use of system software generated executable code for running on WEST-3. The mechanics of reformulation, normalization, and scaling of the mathematical models is discussed in detail, in particulr, the significance of reformulation which leads to accurate simulations. Descriptions for the preprocessor computer programs which are used to prepare the constant data needed in the simulation are given. These programs, in addition to scaling and normalizing all the constants, relieve the user from having to generate a large number of constants used in the simulation. Also given are brief descriptions of the components of the WEST-3 system software: Translator, Assembler, Linker, and Loader. Also included are: details of the aeroelastic rotor analysis, which is the center of a wind turbine simulation model, analysis of the gimbal subsystem; and listings of the variables, constants, and equations used in the simulation
An Asynchronous Parallel Randomized Kaczmarz Algorithm
We describe an asynchronous parallel variant of the randomized Kaczmarz (RK)
algorithm for solving the linear system . The analysis shows linear
convergence and indicates that nearly linear speedup can be expected if the
number of processors is bounded by a multiple of the number of rows in
MARGIN: Uncovering Deep Neural Networks using Graph Signal Analysis
Interpretability has emerged as a crucial aspect of machine learning, aimed
at providing insights into the working of complex neural networks. However,
existing solutions vary vastly based on the nature of the interpretability
task, with each use case requiring substantial time and effort. This paper
introduces MARGIN, a simple yet general approach to address a large set of
interpretability tasks ranging from identifying prototypes to explaining image
predictions. MARGIN exploits ideas rooted in graph signal analysis to determine
influential nodes in a graph, which are defined as those nodes that maximally
describe a function defined on the graph. By carefully defining task-specific
graphs and functions, we demonstrate that MARGIN outperforms existing
approaches in a number of disparate interpretability challenges.Comment: Technical Repor
Trypsin activity as a function of variation in shrimp Penaeus indicus(Crustacea/Arthropoda)
The effect of varying ration size on trypsin activity was evaluated in postlarvae, juvenile and adult
P. indicus maintained on a commercial pelleted feed. Total trypsin activity reported as 11m p-nitroanilide
produced/minute/g tissue was lower (4.23-6.68 11m) in postlarvae in comparison to juvenile (7.24-8.92 11m)
and adult (10.23-12.24 1lJII) animals. Highest activity was detccted at 12%,8-12% and 4-6% in postlarvae,
Juveniles and adult P. indicus respectively which were the optimum ration sizes. while lowest activity was
obtained in the starved animals. Specific activity however exhibIted no significant variation with regard to
ration size and starvation (P > O.1J5)
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