24,334 research outputs found
Exploiting the Design Freedom of RM
This paper details how Rapid Manufacturing (RM) can overcome the restrictions imposed by the
inherent process limitations of conventional manufacturing techniques and become the enabling
technology in fabricating optimal products. A new design methodology capable of exploiting
RM’s increased design freedom is therefore needed. Inspired by natural world structures of trees
and bones, a multi-objective, genetic algorithm based topology optimisation approach is
presented. This combines multiple unit cell structures and varying volume fractions to create a
heterogeneous part structure which exhibits a uniform stress distribution.Mechanical Engineerin
Characters of the W3 algebra
Traces of powers of the zero mode in the W3 Algebra have recently been found
to be of interest, for example in relation to Black Hole thermodynamics, and
arise as the terms in an expansion of the full characters of the algebra. We
calculate the first few such powers in two cases. Firstly, we find the traces
in the 3-state Potts model by using null vectors to derive modular differential
equations for the traces. Secondly, we calculate the exact results for Verma
module representations. We compare our two methods with each other and the
result of brute-force diagonalisation for low levels and find complete
agreement.Comment: v2: Numerous small changes, version to appear in JHEP, 22 pages. v3:
Typos corrected, matches published version, 22 page
Identity and Search in Social Networks
Social networks have the surprising property of being "searchable": Ordinary
people are capable of directing messages through their network of acquaintances
to reach a specific but distant target person in only a few steps. We present a
model that offers an explanation of social network searchability in terms of
recognizable personal identities: sets of characteristics measured along a
number of social dimensions. Our model defines a class of searchable networks
and a method for searching them that may be applicable to many network search
problems, including the location of data files in peer-to-peer networks, pages
on the World Wide Web, and information in distributed databases.Comment: 4 page, 3 figures, revte
A preliminary report on energetic space radiation and dose rate analysis
Energetic space radiation and dose rate analysi
Epidemics and percolation in small-world networks
We study some simple models of disease transmission on small-world networks,
in which either the probability of infection by a disease or the probability of
its transmission is varied, or both. The resulting models display epidemic
behavior when the infection or transmission probability rises above the
threshold for site or bond percolation on the network, and we give exact
solutions for the position of this threshold in a variety of cases. We confirm
our analytic results by numerical simulation.Comment: 6 pages, including 3 postscript figure
Charged particle radiation environment for the LST
Preliminary charged particle dose rates are presented for the LST orbit. The trapped proton component appears to dominate the total dose for the expected shielding available. Typical dose rates should range from 400 to 800 millirads/day
Mean-field solution of the small-world network model
The small-world network model is a simple model of the structure of social
networks, which simultaneously possesses characteristics of both regular
lattices and random graphs. The model consists of a one-dimensional lattice
with a low density of shortcuts added between randomly selected pairs of
points. These shortcuts greatly reduce the typical path length between any two
points on the lattice. We present a mean-field solution for the average path
length and for the distribution of path lengths in the model. This solution is
exact in the limit of large system size and either large or small number of
shortcuts.Comment: 14 pages, 2 postscript figure
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Digital measurement of lightning impulse parameters using curving fitting algorithms
This paper describes the application of curve fitting algorithms to aid the evaluation of lightning impulse parameters. A number of popular curve fitting algorithms have been evaluated and compared. Investigations using the genetic algorithm and other optimisation methods for the purpose of curve fitting have also been carried out and will be described
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