3,673 research outputs found
Role of electrostatic forces in cluster formation in a dry ionomer
This simulation study investigates the dependence of the structure of dry
Nafion-like ionomers on the electrostatic interactions
between the components of the molecules. In order to speed equilibration, a
procedure was adopted which involved detaching the side chains from the
backbone and cutting the backbone into segments, and then reassembling the
macromolecule by means of a strong imposed attractive force between the cut
ends of the backbone, and between the non-ionic ends of the side chains and the
midpoints of the backbone segments. Parameters varied in this study include the
dielectric constant, the free volume, side-chain length, and strength of
head-group interactions. A series of coarse-grained mesoscale simulations shows
the morphlogy to depend sensitively on the ratio of the strength of the
dipole-dipole interactions between the side-chain acidic end groups to the
strength of the other electrostatic components of the Hamiltonian. Examples of
the two differing morphologies proposed by Gierke and by Gebel emerge from our
simulations.Comment: 39 pages, 18 figures, accepted for publicatio
Exact Numerical Solution of the BCS Pairing Problem
We propose a new simulation computational method to solve the reduced BCS
Hamiltonian based on spin analogy and submatrix diagonalization. Then we
further apply this method to solve superconducting energy gap and the results
are well consistent with those obtained by Bogoliubov transformation method.
The exponential problem of 2^{N}-dimension matrix is reduced to the polynomial
problem of N-dimension matrix. It is essential to validate this method on a
real quantumComment: 7 pages, 3 figure
radR: an open-source platform for acquiring and analysing data on biological targets observed by surveillance radar
<p>Abstract</p> <p>Background</p> <p>Radar has been used for decades to study movement of insects, birds and bats. In spite of this, there are few readily available software tools for the acquisition, storage and processing of such data. Program radR was developed to solve this problem.</p> <p>Results</p> <p>Program radR is an open source software tool for the acquisition, storage and analysis of data from marine radars operating in surveillance mode. radR takes time series data with a two-dimensional spatial component as input from some source (typically a radar digitizing card) and extracts and retains information of biological relevance (i.e. moving targets). Low-level data processing is implemented in "C" code, but user-defined functions written in the "R" statistical programming language can be called at pre-defined steps in the calculations. Output data formats are designed to allow for future inclusion of additional data items without requiring change to C code. Two brands of radar digitizing card are currently supported as data sources. We also provide an overview of the basic considerations of setting up and running a biological radar study.</p> <p>Conclusions</p> <p>Program radR provides a convenient, open source platform for the acquisition and analysis of radar data of biological targets.</p
- …