460 research outputs found
A simple and efficient BEM implementation of quasistatic linear visco-elasticity
A simple, yet efficient procedure to solve quasistatic problems of special
linear visco-elastic solids at small strains with equal rheological response in
all tensorial components, utilizing boundary element method (BEM), is
introduced. This procedure is based on the implicit discretisation in time (the
so-called Rothe method) combined with a simple "algebraic" transformation of
variables, leading to a numerically stable procedure (proved explicitly by
discrete energy estimates), which can be easily implemented in a BEM code to
solve initial-boundary value visco-elastic problems by using the Kelvin
elastostatic fundamental solution only. It is worth mentioning that no inverse
Laplace transform is required here. The formulation is straightforward for both
2D and 3D problems involving unilateral frictionless contact. Although the
focus is to the simplest Kelvin-Voigt rheology, a generalization to Maxwell,
Boltzmann, Jeffreys, and Burgers rheologies is proposed, discussed, and
implemented in the BEM code too. A few 2D and 3D initial-boundary value
problems, one of them with unilateral frictionless contact, are solved
numerically
Carrier field shock formation of long wavelength femtosecond pulses in dispersive media
We numerically demonstrate the formation of carrier field shocks in various
dispersive media for a wide variety of input conditions using two different
electric field propagation models. In addition, an investigation of the impact
of numerous physical effects on carrier wave shock is performed. It is shown
that in many cases a field shock is essentially unavoidable and therefore
extremely important in the propagation of intense long wavelength pulses in
weakly dispersive nonlinear media such as noble gases, air, and single-crystal
diamond. The results presented here are expected to have a significant impact
in the field of ultrashort nonlinear optics, attosecond pulse generation, and
wavepacket synthesis where the use of mid-IR wavelengths is becoming
increasingly more important.Comment: 14 pages, 17 figure
Thermodynamics of Electrolytes on Anisotropic Lattices
The phase behavior of ionic fluids on simple cubic and tetragonal
(anisotropic) lattices has been studied by grand canonical Monte Carlo
simulations. Systems with both the true lattice Coulombic potential and
continuous-space electrostatic interactions have been investigated. At
all degrees of anisotropy, only coexistence between a disordered low-density
phase and an ordered high-density phase with the structure similar to ionic
crystal was found, in contrast to recent theoretical predictions. Tricritical
parameters were determined to be monotonously increasing functions of
anisotropy parameters which is consistent with theoretical calculations based
on the Debye-H\"uckel approach. At large anisotropies a two-dimensional-like
behavior is observed, from which we estimated the dimensionless tricritical
temperature and density for the two-dimensional square lattice electrolyte to
be and .Comment: submitted to PR
Influence of randomly distributed magnetic nanoparticles on surface superconductivity in Nb films
We report on combined resistance and magnetic measurements in a hybrid
structure (HS) of randomly distributed anisotropic CoPt magnetic nanoparticles
(MN) embedded in a 160 nm Nb thick film. Our resistance measurements exhibited
a sharp increase at the magnetically determined bulk upper-critical fields
Hc2(T). Above these points the resistance curves are rounded, attaining the
normal state value at much higher fields identified as the surface
superconductivity fields Hc3(T). When plotted in reduced temperature units, the
characteristic field lines Hc3(T) of the HS and of a pure Nb film, prepared at
exactly the same conditions, coincide for H10 kOe
they strongly segregate. Interestingly, the characteristic value H=10 kOe is
equal to the saturation field of the MN. The behavior mentioned above is
observed only for the case where the field is normal to the HS, while is absent
when the field is parallel to the film. Our experimental results suggest that
the observed enhancement of surface superconductivity field Hc3(T) is possibly
due to the not uniform local reduction of the external magnetic field by the
dipolar fields of the MN.Comment: to be published in Phys. Rev.
THE OLVIOS, RETHIS AND INACHOS DRAINAGE SYSTEM EVOLUTION AND HUMAN ACTIVITIES INFLUNCE OF THEIR FUTURE EVOLUTION
Olvios, Rethis and Inachos Rivers are multistory drainage systems that occur in Northern Peloponnesus, and at the present day they have and a reversed, North to South, flow element. Dervenios, Skoupeikos and Fonissa Rivers are the misfit streams of Olvios and revealed as juvenile streams and discharge to the Corinth gulf. Agiorgitikos River is the misfit stream of Rethis River and Seliandros River is the juvenile stream. Asopos, Nemeas and Rachiani Rives are the misfit streams of Inachos River and they also discharge to the Corinth gulf. Asopos River characterized as re-established stream. Physical factors such as tectonic regime (active and inactive faults), lithology, erosion and distance from the source influenced the three drainage systems evolution and could be influence them also in the future. The increase of human activities both in their southern parts and in the distal parts close to the coast could be change the physical evolution of the studied drainages, producing a new wind gap in the coastal area and a lake or a lagoon backwards of the coastal area, destroying villages and towns
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