10,063 research outputs found
Recent Results of Multimagnetical Simulations of the Ising Model
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the and Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact results. In
the physically more interesting case we estimate the amplitude of
the critical interfacial tension.Comment: talk presented at the workshop "Dynamics of First Order Phase
Transitions", Juelich June 1-3; FSU-SCRI-92C-87 preprint; 7 pages; sorry no
figures; needs vanilla.st
Vertically inserted geotextile used for strengthening levees against internal erosion
The effectiveness of a vertical inserted geotextile against internal erosion, in particular backward erosion, has been investigated. Some small- and medium-scale tests were performed as well as a field-scale test and compared with test series without any erosion mitigating measure. All tests demonstrated that the geotextile shield was very effective to prevent backward erosion. Numerical analysis showed that it was more effective than an impermeable sheet pile of the same length. The paper describes the technique in more detail as well as the results of numerical calculations. Furthermore, the test facilities are describe
Structure of the Energy Landscape of Short Peptides
We have simulated, as a showcase, the pentapeptide Met-enkephalin
(Tyr-Gly-Gly-Phe-Met) to visualize the energy landscape and investigate the
conformational coverage by the multicanonical method. We have obtained a
three-dimensional topographic picture of the whole energy landscape by plotting
the histogram with respect to energy(temperature) and the order parameter,
which gives the degree of resemblance of any created conformation with the
global energy minimum (GEM).Comment: 17 pages, 4 figure
A Multicanonical Algorithm and the Surface Free Energy in SU(3) Pure Gauge Theory
We present a multicanonical algorithm for the SU(3) pure gauge theory at the
deconfinement phase transition. We measure the tunneling times for lattices of
size L^3x2 for L=8,10, and 12. In contrast to the canonical algorithm the
tunneling time increases only moderately with L. Finally, we determine the
interfacial free energy applying the multicanonical algorithm.Comment: 6 pages, HLRZ-92-3
Financial Markets Analysis by Probabilistic Fuzzy Modelling
For successful trading in financial markets, it is important to develop financial models where one can identify different states of the market for modifying one???s actions. In this paper, we propose to use probabilistic fuzzy systems for this purpose. We concentrate on Takagi???Sugeno (TS) probabilistic fuzzy systems that combine interpretability of fuzzy systems with the statistical properties of probabilistic systems. We start by recapitulating the general architecture of TS probabilistic fuzzy rule-based systems and summarize the corresponding reasoning schemes. We mention how probabilities can be estimated from a given data set and how a probability distribution can be approximated by a fuzzy histogram. We apply our methodology for financial time series analysis and demonstrate how a probabilistic TS fuzzy system can be identified, assuming that a linguistic term set is given. We illustrate the interpretability of such a system by inspecting the rule bases of our models.time series analysis;data-driven design;fuzzy reasoning;fuzzy rule base;probabilistic fuzzy systems
Eliciting Expert Knowledge for Fuzzy Evaluation of Agricultural Production Systems
Public concern nowadays is an important frame of reference for thedevelopment of agricultural production systems. The development ofsuch systems, therefore, involves both society level and productionsystem level. Following Zadeh's principle of incompatibility,information obtained at production system level is interpreted atsociety level in linguistic terms. Fuzzy models promise to be avaluable tool as they link measurable information to linguisticinterpretation using membership functions. The objective of this paperis to outline a procedure which deals with criticism regarding theinherent subjectivity in the construction of membership functions whenusing expert knowledge. The procedure guarantees the selection ofappropriate expert knowledge, and provides a guideline supporting theselection of methods to elicit expert knowledge and constructmembership functions. Also on the basis of the results in anillustrative example, it is concluded that the procedure outlined inthis paper suitably deals with criticism regarding membershipfunctions and, therefore, enables a practical implementation of fuzzyevaluation of agricultural production systems. Current researchimplements the procedure to build a fuzzy model which evaluates eggproduction systems in relation to public concern about the welfare oflaying hens.evaluation;subjectivity;expert knowledge;fuzzy models;knowledge elicitation
Multicanonical Study of the 3D Ising Spin Glass
We simulated the Edwards-Anderson Ising spin glass model in three dimensions
via the recently proposed multicanonical ensemble. Physical quantities such as
energy density, specific heat and entropy are evaluated at all temperatures. We
studied their finite size scaling, as well as the zero temperature limit to
explore the ground state properties.Comment: FSU-SCRI-92-121; 7 pages; sorry, no figures include
Exchange Monte Carlo Method and Application to Spin Glass Simulations
We propose an efficient Monte Carlo algorithm for simulating a
``hardly-relaxing" system, in which many replicas with different temperatures
are simultaneously simulated and a virtual process exchanging configurations of
these replica is introduced. This exchange process is expected to let the
system at low temperatures escape from a local minimum. By using this algorithm
the three-dimensional Ising spin glass model is studied. The ergodicity
time in this method is found much smaller than that of the multi-canonical
method. In particular the time correlation function almost follows an
exponential decay whose relaxation time is comparable to the ergodicity time at
low temperatures. It suggests that the system relaxes very rapidly through the
exchange process even in the low temperature phase.Comment: 10 pages + uuencoded 5 Postscript figures, REVTe
Efficiency of initiating cell adhesion in hydrodynamic flow
We theoretically investigate the efficiency of initial binding between a
receptor-coated sphere and a ligand-coated wall in linear shear flow. The mean
first passage time for binding decreases monotonically with increasing shear
rate. Above a saturation threshold of the order of a few 100 receptor patches,
the binding efficiency is enhanced only weakly by increasing their number and
size, but strongly by increasing their height. This explains why white blood
cells in the blood flow adhere through receptor patches localized to the tips
of microvilli, and why malaria-infected red blood cells form elevated receptor
patches (knobs).Comment: 4 pages, Revtex, 4 Postscript figures included, to appear in PR
Generalized-ensemble Monte carlo method for systems with rough energy landscape
We present a novel Monte Carlo algorithm which enhances equilibrization of
low-temperature simulations and allows sampling of configurations over a large
range of energies. The method is based on a non-Boltzmann probability weight
factor and is another version of the so-called generalized-ensemble techniques.
The effectiveness of the new approach is demonstrated for the system of a small
peptide, an example of the frustrated system with a rugged energy landscape.Comment: Latex; ps-files include
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