11,551 research outputs found
On the Integrability, B\"Acklund Transformation and Symmetry Aspects of a Generalized Fisher Type Nonlinear Reaction-Diffusion Equation
The dynamics of nonlinear reaction-diffusion systems is dominated by the
onset of patterns and Fisher equation is considered to be a prototype of such
diffusive equations. Here we investigate the integrability properties of a
generalized Fisher equation in both (1+1) and (2+1) dimensions. A Painlev\'e
singularity structure analysis singles out a special case () as
integrable. More interestingly, a B\"acklund transformation is shown to give
rise to a linearizing transformation for the integrable case. A Lie symmetry
analysis again separates out the same case as the integrable one and
hence we report several physically interesting solutions via similarity
reductions. Thus we give a group theoretical interpretation for the system
under study. Explicit and numerical solutions for specific cases of
nonintegrable systems are also given. In particular, the system is found to
exhibit different types of travelling wave solutions and patterns, static
structures and localized structures. Besides the Lie symmetry analysis,
nonclassical and generalized conditional symmetry analysis are also carried
out.Comment: 30 pages, 10 figures, to appear in Int. J. Bifur. Chaos (2004
An advanced fuzzy Bayesian-based FMEA approach for assessing maritime supply chain risks
This paper aims to develop a novel model to assess the risk factors of maritime supply chains by incorporating a fuzzy belief rule approach with Bayesian networks. The new model, compared to traditional risk analysis methods, has the capability of improving result accuracy under a high uncertainty in risk data. A real case of a world leading container shipping company is investigated, and the research results reveal that among the most significant risk factors are transportation of dangerous goods, fluctuation of fuel price, fierce competition, unattractive markets, and change of exchange rates in sequence. Such findings will provide useful insights for accident prevention
Dynamics of conduction blocks in a model of paced cardiac tissue
We study numerically the dynamics of conduction blocks using a detailed
electrophysiological model. We find that this dynamics depends critically on
the size of the paced region. Small pacing regions lead to stationary
conduction blocks while larger pacing regions can lead to conduction blocks
that travel periodically towards the pacing region. We show that this
size-dependence dynamics can lead to a novel arrhythmogenic mechanism.
Furthermore, we show that the essential phenomena can be captured in a much
simpler coupled-map model.Comment: 8 pages 6 figure
Use of evidential reasoning for eliciting bayesian subjective probabilities in human reliability analysis: A maritime case
Modelling the interdependencies among the factors influencing human error (e.g. the common performance conditions (CPCs) in Cognitive Reliability Error Analysis Method (CREAM)) stimulates the use of Bayesian Networks (BNs) in Human Reliability Analysis (HRA). However, subjective probability elicitation for a BN is often a daunting and complex task. To create conditional probability values for each given variable in a BN requires a high degree of knowledge and engineering effort, often from a group of domain experts. This paper presents a novel hybrid approach for incorporating the evidential reasoning (ER) approach with BNs to facilitate HRA under incomplete data. The kernel of this approach is to develop the best and the worst possible conditional subjective probabilities of the nodes representing the factors influencing HRA when using BNs in human error probability (HEP). The proposed hybrid approach is demonstrated by using CREAM to estimate HEP in the maritime area. The findings from the hybrid ER-BN model can effectively facilitate HEP analysis in specific and decision-making under uncertainty in general
A refined invariant subspace method and applications to evolution equations
The invariant subspace method is refined to present more unity and more
diversity of exact solutions to evolution equations. The key idea is to take
subspaces of solutions to linear ordinary differential equations as invariant
subspaces that evolution equations admit. A two-component nonlinear system of
dissipative equations was analyzed to shed light on the resulting theory, and
two concrete examples are given to find invariant subspaces associated with
2nd-order and 3rd-order linear ordinary differential equations and their
corresponding exact solutions with generalized separated variables.Comment: 16 page
Mass movement susceptibility mapping using satellite optical imagery compared with InSAR monitoring: Zigui County, Three Gorges region, China
Mass movements on steep slopes are a major hazard to
communities and infrastructure in the Three Gorges
region, China. Developing susceptibility maps of mass
movements is therefore very important in both current
and future land use planning. This study employed
satellite optical imagery and an ASTER GDEM (15 m)
to derive various parameters (namely geology; slope
gradient; proximity to drainage networks and proximity
to lineaments) in order to create a GIS-based map of
mass movement susceptibility. This map was then
evaluated using highly accurate deformation signals
processed using the Persistent Scatterer (PS) InSAR
technique. Areas of high susceptibility correspond well
to points of high subsidence, which provides a strong
support of our susceptibility map
Anomalous thermoelectric effects of ZrTe in and beyond the quantum limit
Thermoelectric effects are more sensitive and promising probes to topological
properties of emergent materials, but much less addressed compared to other
physical properties. Zirconium pentatelluride (ZrTe) has inspired active
investigations recently because of its multiple topological nature. We study
the thermoelectric effects of ZrTe in a magnetic field and find several
anomalous behaviors. The Nernst response has a steplike profile near zero field
when the charge carriers are electrons only, suggesting the anomalous Nernst
effect arising from a nontrivial profile of Berry curvature. Both the
thermopower and Nernst signal exhibit exotic peaks in the strong-field quantum
limit. At higher magnetic fields, the Nernst signal has a sign reversal at a
critical field where the thermopower approaches to zero. We propose that these
anomalous behaviors can be attributed to the Landau index inversion, which is
resulted from the competition of the dependence of the Dirac-type
Landau bands and linear- dependence of the Zeeman energy ( is the
magnetic field). Our understanding to the anomalous thermoelectric properties
in ZrTe opens a new avenue for exploring Dirac physics in topological
materials.Comment: 6 pages, 4 figure
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