13,555 research outputs found
How to mesh up Ewald sums (I): A theoretical and numerical comparison of various particle mesh routines
Standard Ewald sums, which calculate e.g. the electrostatic energy or the
force in periodically closed systems of charged particles, can be efficiently
speeded up by the use of the Fast Fourier Transformation (FFT). In this article
we investigate three algorithms for the FFT-accelerated Ewald sum, which
attracted a widespread attention, namely, the so-called
particle-particle-particle-mesh (P3M), particle mesh Ewald (PME) and smooth PME
method. We present a unified view of the underlying techniques and the various
ingredients which comprise those routines. Additionally, we offer detailed
accuracy measurements, which shed some light on the influence of several tuning
parameters and also show that the existing methods -- although similar in
spirit -- exhibit remarkable differences in accuracy. We propose combinations
of the individual components, mostly relying on the P3M approach, which we
regard as most flexible.Comment: 18 pages, 8 figures included, revtex styl
How Close to Two Dimensions Does a Lennard-Jones System Need to Be to Produce a Hexatic Phase?
We report on a computer simulation study of a Lennard-Jones liquid confined
in a narrow slit pore with tunable attractive walls. In order to investigate
how freezing in this system occurs, we perform an analysis using different
order parameters. Although some of the parameters indicate that the system goes
through a hexatic phase, other parameters do not. This shows that to be certain
whether a system has a hexatic phase, one needs to study not only a large
system, but also several order parameters to check all necessary properties. We
find that the Binder cumulant is the most reliable one to prove the existence
of a hexatic phase. We observe an intermediate hexatic phase only in a
monolayer of particles confined such that the fluctuations in the positions
perpendicular to the walls are less then 0.15 particle diameters, i. e. if the
system is practically perfectly 2d
The free rigid body dynamics: generalized versus classic
In this paper we analyze the normal forms of a general quadratic Hamiltonian
system defined on the dual of the Lie algebra of real -
skew - symmetric matrices, where is an arbitrary real symmetric
matrix. A consequence of the main results is that any first-order autonomous
three-dimensional differential equation possessing two independent quadratic
constants of motion which admits a positive/negative definite linear
combination, is affinely equivalent to the classical "relaxed" free rigid body
dynamics with linear controls.Comment: 12 page
Taking the Journal to the Digital Age
Editor\u27s introduction and comments to Spring 2016, volume 53, issue 1 of Speaker & Gavel
A Note from the Editor
A note from the editor of Speaker & Gavel, Todd Holm for volume 58, issue 1, 2022
The Teaching of Creativity: Process, Product, Environment, and Assessment
Teaching creativity is an issue gaining more attention. Businesses and universities alike are looking for ways to promote creative and innovative thinking. As universities look for ways to teach and assess creativity, interscholastic speech and debate competition should be held up as a model for such efforts. Through a combination of iterative performances, the mastering of domain knowledge, an environment that encourages/rewards creativity, and feedback based on the Consensual Assessment Technique, forensics offers an ideal environment for students to learn the process of developing creative products
- …