11,929 research outputs found
Modeling material failure with a vectorized routine
The computational aspects of modelling material failure in structural wood members are presented with particular reference to vector processing aspects. Wood members are considered to be highly orthotropic, inhomogeneous, and discontinuous due to the complex microstructure of wood material and the presence of natural growth characteristics such as knots, cracks and cross grain in wood members. The simulation of strength behavior of wood members is accomplished through the use of a special purpose finite element/fracture mechanics routine, program STARW (Strength Analysis Routine for Wood). Program STARW employs quadratic finite elements combined with singular crack tip elements in a finite element mesh. Vector processing techniques are employed in mesh generation, stiffness matrix formation, simultaneous equation solution, and material failure calculations. The paper addresses these techniques along with the time and effort requirements needed to convert existing finite element code to a vectorized version. Comparisons in execution time between vectorized and nonvectorized routines are provided
A quantum central limit theorem for non-equilibrium systems: Exact local relaxation of correlated states
We prove that quantum many-body systems on a one-dimensional lattice locally
relax to Gaussian states under non-equilibrium dynamics generated by a bosonic
quadratic Hamiltonian. This is true for a large class of initial states - pure
or mixed - which have to satisfy merely weak conditions concerning the decay of
correlations. The considered setting is a proven instance of a situation where
dynamically evolving closed quantum systems locally appear as if they had truly
relaxed, to maximum entropy states for fixed second moments. This furthers the
understanding of relaxation in suddenly quenched quantum many-body systems. The
proof features a non-commutative central limit theorem for non-i.i.d. random
variables, showing convergence to Gaussian characteristic functions, giving
rise to trace-norm closeness. We briefly relate our findings to ideas of
typicality and concentration of measure.Comment: 27 pages, final versio
Handbook for estimating toxic fuel hazards
Computer program predicts, from readily available meteorological data, concentration and dosage fields downwind from ground-level and elevated sources of toxic fuel emissions. Mathematical model is applicable to hot plume rise from industrial stacks and should also be of interest to air pollution meteorologists
Ubic: Bridging the gap between digital cryptography and the physical world
Advances in computing technology increasingly blur the boundary between the
digital domain and the physical world. Although the research community has
developed a large number of cryptographic primitives and has demonstrated their
usability in all-digital communication, many of them have not yet made their
way into the real world due to usability aspects. We aim to make another step
towards a tighter integration of digital cryptography into real world
interactions. We describe Ubic, a framework that allows users to bridge the gap
between digital cryptography and the physical world. Ubic relies on
head-mounted displays, like Google Glass, resource-friendly computer vision
techniques as well as mathematically sound cryptographic primitives to provide
users with better security and privacy guarantees. The framework covers key
cryptographic primitives, such as secure identification, document verification
using a novel secure physical document format, as well as content hiding. To
make a contribution of practical value, we focused on making Ubic as simple,
easily deployable, and user friendly as possible.Comment: In ESORICS 2014, volume 8712 of Lecture Notes in Computer Science,
pp. 56-75, Wroclaw, Poland, September 7-11, 2014. Springer, Berlin, German
Parametric instabilities in magnetized multicomponent plasmas
This paper investigates the excitation of various natural modes in a
magnetized bi-ion or dusty plasma. The excitation is provided by parametrically
pumping the magnetic field. Here two ion-like species are allowed to be fully
mobile. This generalizes our previous work where the second heavy species was
taken to be stationary. Their collection of charge from the background neutral
plasma modifies the dispersion properties of the pump and excited waves. The
introduction of an extra mobile species adds extra modes to both these types of
waves. We firstly investigate the pump wave in detail, in the case where the
background magnetic field is perpendicular to the direction of propagation of
the pump wave. Then we derive the dispersion equation relating the pump to the
excited wave for modes propagating parallel to the background magnetic field.
It is found that there are a total of twelve resonant interactions allowed,
whose various growth rates are calculated and discussed.Comment: Published in May 2004; this is a late submission to the archive. 14
pages, 8 figure
Model for Stress Analysis and Strength Prediction of Lumber
A mathematical model has been developed that can predict the elastic and strength behavior of a section of a structural lumber member containing a knot and cross grain. The model, embodied in the computer program KMESHI, accounts for the presence of a knot, the associated grain deviations, and global cross grain, and can define localized stresses and displacements anywhere within the member. These capabilities are illustrated here through an examination of maximum stress concentrations for varying knot locations. The results point out the severe stress concentration that can be caused by an edge knot as opposed to a similar size center knot.An "effective section technique" is presented as a strength prediction procedure that uses Program KMESHI and a maximum stress failure theory. Unlike other strength prediction methods, this procedure recognizes that a progressive failure sequence leads to the ultimate member load. Through calculation of stresses and strains, and a predicted progressive failure sequence, the effective section technique was shown to be quite accurate in predicting the strength for two example pieces of lumber
Structure of glassy lithium sulfate films sputtered in nitrogen (LISON): Insight from Raman spectroscopy and ab initio calculations
Raman spectra of thin solid electrolyte films obtained by sputtering a
lithium sulfate target in nitrogen plasma are measured and compared to ab
initio electronic structure calculations for clusters composed of 28 atoms.
Agreement between measured and calculated spectra is obtained when oxygen atoms
are replaced by nitrogen atoms and when the nitrogen atoms form bonds with each
other. This suggests that the incorporation of nitrogen during the sputtering
process leads to structures in the film, which prevent crystallization of these
thin film salt glasses.Comment: 5 pages, 4 figure
Quantum protocols for anonymous voting and surveying
We describe quantum protocols for voting and surveying. A key feature of our
schemes is the use of entangled states to ensure that the votes are anonymous
and to allow the votes to be tallied. The entanglement is distributed over
separated sites; the physical inaccessibility of any one site is sufficient to
guarantee the anonymity of the votes. The security of these protocols with
respect to various kinds of attack is discussed. We also discuss classical
schemes and show that our quantum voting protocol represents a N-fold reduction
in computational complexity, where N is the number of voters.Comment: 8 pages. V2 includes the modifications made for the published versio
- …