1,467 research outputs found
Generation of finite wave trains in excitable media
Spatiotemporal control of excitable media is of paramount importance in the
development of new applications, ranging from biology to physics. To this end
we identify and describe a qualitative property of excitable media that enables
us to generate a sequence of traveling pulses of any desired length, using a
one-time initial stimulus. The wave trains are produced by a transient
pacemaker generated by a one-time suitably tailored spatially localized finite
amplitude stimulus, and belong to a family of fast pulse trains. A second
family, of slow pulse trains, is also present. The latter are created through a
clumping instability of a traveling wave state (in an excitable regime) and are
inaccessible to single localized stimuli of the type we use. The results
indicate that the presence of a large multiplicity of stable, accessible,
multi-pulse states is a general property of simple models of excitable media.Comment: 6 pages, 6 figure
Grown organic matter as a fuel raw material resource
An extensive search was made on biomass production from the standpoint of climatic zones, water, nutrients, costs and energy requirements for many species. No exotic species were uncovered that gave hope for a bonanza of biomass production under culture, location, and management markedly different from those of existing agricultural concepts. A simulation analysis of biomass production was carried out for six species using conventional production methods, including their production costs and energy requirements. These estimates were compared with data on food, fiber, and feed production. The alternative possibility of using residues from food, feed, or lumber was evaluated. It was concluded that great doubt must be cast on the feasibility of producing grown organic matter for fuel, in competition with food, feed, or fiber. The feasibility of collecting residues may be nearer, but the competition for the residues for return to the soil or cellulosic production is formidable
Direction Detector on an Excitable Field: Field Computation with Coincidence Detection
Living organisms process information without any central control unit and
without any ruling clock. We have been studying a novel computational strategy
that uses a geometrically arranged excitable field, i.e., "field computation."
As an extension of this research, in the present article we report the
construction of a "direction detector" on an excitable field. Using a numerical
simulation, we show that the direction of a input source signal can be detected
by applying the characteristic as a "coincidence detector" embedded on an
excitable field. In addition, we show that this direction detection actually
works in an experiment using an excitable chemical system. These results are
discussed in relation to the future development of "field computation."Comment: 6 pages, 3 figure
SciRecSys: A Recommendation System for Scientific Publication by Discovering Keyword Relationships
In this work, we propose a new approach for discovering various relationships
among keywords over the scientific publications based on a Markov Chain model.
It is an important problem since keywords are the basic elements for
representing abstract objects such as documents, user profiles, topics and many
things else. Our model is very effective since it combines four important
factors in scientific publications: content, publicity, impact and randomness.
Particularly, a recommendation system (called SciRecSys) has been presented to
support users to efficiently find out relevant articles
How the asymmetry of internal potential influences the shape of I-V characteristic of nanochannels
Ion transport in biological and synthetic nanochannels is characterized by
such phenomena as ion current fluctuations, rectification, and pumping.
Recently, it has been shown that the nanofabricated synthetic pores could be
considered as analogous to biological channels with respect to their transport
characteristics \cite{Apel, Siwy}. The ion current rectification is analyzed.
Ion transport through cylindrical nanopores is described by the Smoluchowski
equation. The model is considering the symmetric nanopore with asymmetric
charge distribution. In this model, the current rectification in asymmetrically
charged nanochannels shows a diode-like shape of characteristic. It is
shown that this feature may be induced by the coupling between the degree of
asymmetry and the depth of internal electric potential well. The role of
concentration gradient is discussed
Avalanche of Bifurcations and Hysteresis in a Model of Cellular Differentiation
Cellular differentiation in a developping organism is studied via a discrete
bistable reaction-diffusion model. A system of undifferentiated cells is
allowed to receive an inductive signal emenating from its environment.
Depending on the form of the nonlinear reaction kinetics, this signal can
trigger a series of bifurcations in the system. Differentiation starts at the
surface where the signal is received, and cells change type up to a given
distance, or under other conditions, the differentiation process propagates
through the whole domain. When the signal diminishes hysteresis is observed
On the Accuracy of A.C. Flux Leakage, Eddy Current, EMAT and Ultrasonic Methods of Measuring Surface Connecting Flaws in Seamless Steel Tubing
The objective of this study was to perform a comparative experimental evaluation to determine the detection sensitivity, classification (fJaw type) and depth sizing accuracy of A.C. flux leakage, single-frequency eddy current, electromagnetic acoustic transducer (EMAT) generated surface waves, and broadband ultrasonic methods for the measurement of complex surface connecting flaws in hot rolled, seamless, ferritic tubing. Since it was of interest to invest NDE techniques over a wide range of capabilities, tubing having flaw depths far exceeding industry standards was tested and evaluated. Results of the study will be used to provide a benchmark assessment of these NDE methods, from which decisions concerning production test systems can be made
Use of soil moisture information in yield models
There are no author-identified significant results in this report
Unfolding a Codimension-Two, Discontinuous, Andronov-Hopf Bifurcation
We present an unfolding of the codimension-two scenario of the simultaneous
occurrence of a discontinuous bifurcation and an Andronov-Hopf bifurcation in a
piecewise-smooth, continuous system of autonomous ordinary differential
equations in the plane. We find the Hopf cycle undergoes a grazing bifurcation
that may be very shortly followed by a saddle-node bifurcation of the orbit. We
derive scaling laws for the bifurcation curves that emanate from the
codimension-two bifurcation.Comment: 19 pages, 4 figure
Noise-induced inhibitory suppression of malfunction neural oscillators
Motivated by the aim to find new medical strategies to suppress undesirable
neural synchronization we study the control of oscillations in a system of
inhibitory coupled noisy oscillators. Using dynamical properties of inhibition,
we find regimes when the malfunction oscillations can be suppressed but the
information signal of a certain frequency can be transmitted through the
system. The mechanism of this phenomenon is a resonant interplay of noise and
the transmission signal provided by certain value of inhibitory coupling.
Analyzing a system of three or four oscillators representing neural clusters,
we show that this suppression can be effectively controlled by coupling and
noise amplitudes.Comment: 10 pages, 14 figure
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