1,194,274 research outputs found
Evolution of Human-like Social Grooming Strategies regarding Richness and Group Size
Human beings tend to cooperate with close friends, therefore they have to
construct strong social relationships to recieve cooperation from others.
Therefore they should have acquired their strategies of social relationship
construction through an evolutionary process. The behavior of social
relationship construction is know as "social grooming." In this paper, we show
that there are four classes including a human-like strategy in evolutionary
dynamics of social grooming strategies based on an evolutionary game
simulation. Social relationship strengths (as measured by frequency of social
grooming) often show a much skewed distribution (a power law distribution). It
may be due to time costs constraints on social grooming, because the costs are
too large to ignore for having many strong social relationships. Evolution of
humans' strategies of construction of social relationships may explain the
origin of human intelligence based on a social brain hypothesis. We constructed
an individual-based model to explore the evolutionary dynamics of social
grooming strategies. The model is based on behavior to win over others by
strengthening social relationships with cooperators. The results of
evolutionary simulations show the four classes of evolutionary dynamics. The
results depend on total resources and the ratio of each cooperator's resource
to the number of cooperators. One of the four classes is similar to a human
strategy, i.e. the strategies based on the Yule--Simon process of power law.Comment: 21 pages, 10 figure
Lax pair formulation in the simultaneous presence of boundaries and defects
Inspired by recent results on the effect of integrable boundary conditions on
the bulk behavior of an integrable system, and in particular on the behavior of
an existing defect we systematically formulate the Lax pairs in the
simultaneous presence of integrable boundaries and defects. The respective
sewing conditions as well as the relevant equations of motion on the defect
point are accordingly extracted. We consider a specific prototype i.e. the
vector non-linear Schr\"{o}dinger (NLS) model to exemplify our construction.
This model displays a highly non-trivial behavior and allows the existence of
two distinct types of boundary conditions based on the reflection algebra or
the twisted Yangian.Comment: 19 pages, Latex. A few comments and clarifications added. Version to
appear in J. Phys.
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Printing High Viscosity Fluids using Ultrasonic Droplet Generation
A new printing technology based on ultrasonic actuation (~1 MHz) is presented that has the
potential to print high viscosity fluids. In this paper, we describe the print-head’s operating
principles and construction. Acoustic focusing in the nozzles produces high pressure gradients
that help eject the fluid which, under the proper conditions, forms droplets. Two types of models
are presented to attempt to predict print-head behavior over a range of conditions. The first
model borrows from simple fully developed, laminar flows to estimate printing conditions based
on fluid properties, as well as printing pressures. The second model captures the dynamic
behavior of the print-head to estimate cavity resonances that lead to acoustic focusing and
potentially droplet generation. We report on experiments with several types of fluids that
demonstrate the technology’s potential.Mechanical Engineerin
Oscillations and traveling waves of calcium: a simplified model
We construct a heuristic model of calcium oscillations in pancreatic acinar cells. The model is
based on the two-state model of Sneyd et al. (Sneyd, J., A. LeBeau and D. Yule, 2000, Traveling
waves of calcium in pancreatic acinar cells: model construction and bifurcation analysis, Physica D,
in press) and is similar in spirit to the FitzHugh reduction of the Hodgkin-Huxley equations. The
simpli¯ed model successfully reproduces the oscillatory behavior and wave behaviour of the more
complex model. In particular, the simpli¯ed model provides an example of a simple, physiologically
relevant model that has a T-point and an associated spiral branch of homoclinic orbits
General-relativistic Model of Magnetically Driven Jet
The general scheme for the construction of the general-relativistic model of
the magnetically driven jet is suggested. The method is based on the usage of
the 3+1 MHD formalism. It is shown that the critical points of the flow and the
explicit radial behavior of the physical variables may be derived through the
jet ``profile function."Comment: 12 pages, LaTex, no figure
A recursive-faulting model of distributed damage in confined brittle materials
We develop a model of distributed damage in brittle materials deforming in triaxial compression based on the explicit construction of special microstructures obtained by recursive faulting. The model aims to predict the effective or macroscopic behavior of the material from its elastic and fracture properties; and to predict the microstructures underlying the microscopic behavior. The model accounts for the elasticity of the matrix, fault nucleation and the cohesive and frictional behavior of the faults. We analyze the resulting quasistatic boundary value problem and determine the relaxation of the potential energy, which describes the macroscopic material behavior averaged over all possible fine-scale structures. Finally, we present numerical calculations of the dynamic multi-axial compression experiments on sintered aluminum nitride of Chen and Ravichandran [1994. Dynamic compressive behavior of ceramics under lateral confinement. J. Phys. IV 4, 177–182; 1996a. Static and dynamic compressive behavior of aluminum nitride under moderate confinement. J. Am. Soc. Ceramics 79(3), 579–584; 1996b. An experimental technique for imposing dynamic multiaxial compression with mechanical confinement. Exp. Mech. 36(2), 155–158; 2000. Failure mode transition in ceramics under dynamic multiaxial compression. Int. J. Fracture 101, 141–159]. The model correctly predicts the general trends regarding the observed damage patterns; and the brittle-to-ductile transition resulting under increasing confinement
Ground Energy of the Magnetic Laplacian in Polyhedral Bodies
The asymptotic behavior of the first eigenvalues of magnetic Laplacian
operators with large magnetic fields and Neumann realization in polyhedral
domains is characterized by a hierarchy of model problems. We investigate
properties of the model problems (continuity, semi-continuity, existence of
generalized eigenfunctions). We prove estimates for the remainders of our
asymptotic formula. Lower bounds are obtained with the help of a classical IMS
partition based on adequate coverings of the polyhedral domain, whereas upper
bounds are established by a novel construction of quasimodes, qualified as
sitting or sliding according to spectral properties of local model problems.Comment: 59 page
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