1,174 research outputs found
Histogram analysis as a method for determining the line tension by Monte-Carlo simulations
A method is proposed for determining the line tension, which is the main
physical characteristic of a three-phase contact region, by Monte-Carlo (MC)
simulations. The key idea of the proposed method is that if a three-phase
equilibrium involves a three-phase contact region, the probability distribution
of states of a system as a function of two order parameters depends not only on
the surface tension, but also on the line tension. This probability
distribution can be obtained as a normalized histogram by appropriate MC
simulations, so one can use the combination of histogram analysis and
finite-size scaling to study the properties of a three phase contact region.
Every histogram and results extracted therefrom will depend on the size of the
simulated system. Carrying out MC simulations for a series of system sizes and
extrapolating the results, obtained from the corresponding series of
histograms, to infinite size, one can determine the line tension of the three
phase contact region and the interfacial tensions of all three interfaces (and
hence the contact angles) in an infinite system. To illustrate the proposed
method, it is applied to the three-dimensional ternary fluid mixture, in which
molecular pairs of like species do not interact whereas those of unlike species
interact as hard spheres. The simulated results are in agreement with
expectations
Multilayer approximation for a confined fluid in a slit pore
A simple Lennard-Jones fluid confined in a slit nanopore with hard walls is
studied on the basis of a multilayer structured model. Each layer is
homogeneous and parallel to the walls of the pore. The Helmholtz energy of this
system is constructed following van der Waals-like approximations, with the
advantage that the model geometry permits to obtain analytical expressions for
the integrals involved. Being the multilayer system in thermodynamic
equilibrium, a system of non-linear equations is obtained for the densities and
widths of the layers. A numerical solution of the equations gives the density
profile and the longitudinal pressures. The results are compared with Monte
Carlo simulations and with experimental data for Nitrogen, showing very good
agreement.Comment: 6 pages, 5 figures
Status of the EDELWEISS-II experiment
EDELWEISS is a direct dark matter search experiment situated in the low
radioactivity environment of the Modane Underground Laboratory. The experiment
uses Ge detectors at very low temperature in order to identify eventual rare
nuclear recoils induced by elastic scattering of WIMPs from our Galactic halo.
We present results of the commissioning of the second phase of the experiment,
involving more than 7 kg of Ge, that has been completed in 2007. We describe
two new types of detectors with active rejection of events due to surface
contamination. This active rejection is required in order to achieve the
physics goals of 10-8 pb cross-section measurement for the current phase
Correlation between electric-field-induced phase transition and piezoelectricity in lead zirconate titanate films
We observed that electric field induces phase transition from tetragonal to
rhombohedral in polycrystalline morphotropic lead zirconate titanate (PZT)
films, as reported in 2011 for bulk PZT. Moreover, we evidenced that this
field-induced phase transition is strongly correlated with PZT film
piezoelectric properties, that is to say the larger the phase transition, the
larger the longitudinal piezoelectric coefficient d 33,eff . Although d 33,eff
is already comprised between as 150 to 170 pm/V, our observation suggests that
one could obtain larger d 33,eff values, namely 250 pm/V, by optimizing the
field-induced phase transition thanks to composition fine tuning
A General Theory of Non-equilibrium Dynamics of Lipid-protein Fluid Membranes
We present a general and systematic theory of non-equilibrium dynamics of
multi-component fluid membranes, in general, and membranes containing
transmembrane proteins, in particular. Developed based on a minimal number of
principles of statistical physics and designed to be a meso/macroscopic-scale
effective description, the theory is formulated in terms of a set of equations
of hydrodynamics and linear constitutive relations. As a particular emphasis of
the theory, the equations and the constitutive relations address both the
thermodynamic and the hydrodynamic consequences of the unconventional material
characteristics of lipid-protein membranes and contain proposals as well as
predictions which have not yet been made in already existed work on membrane
hydrodynamics and which may have experimental relevance. The framework
structure of the theory makes possible its applications to a range of
non-equilibrium phenomena in a range of membrane systems, as discussions in the
paper of a few limit cases demonstrate.Comment: 22 pages, 2 figures, minor changes and addition
Cantilever-based electret energy harvesters
Integration of structures and functions allowed reducing electric
consumptions of sensors, actuators and electronic devices. Therefore, it is now
possible to imagine low-consumption devices able to harvest their energy in
their surrounding environment. One way to proceed is to develop converters able
to turn mechanical energy, such as vibrations, into electricity: this paper
focuses on electrostatic converters using electrets. We develop an accurate
analytical model of a simple but efficient cantilever-based electret energy
harvester. Therefore, we prove that with vibrations of 0.1g (~1m/s^{2}), it is
theoretically possible to harvest up to 30\muW per gram of mobile mass. This
power corresponds to the maximum output power of a resonant energy harvester
according to the model of William and Yates. Simulations results are validated
by experimental measurements but the issues of parasitic capacitances get a
large impact. Therefore, we 'only' managed to harvest 10\muW per gram of mobile
mass, but according to our factor of merit, this puts us in the best results of
the state of the art. http://iopscience.iop.org/0964-1726/20/10/105013Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Smart Materials and Structures. IOP Publishing
Ltd is not responsible for any errors or omissions in this version of the
manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
doi:10.1088/0964-1726/20/10/105013;
http://iopscience.iop.org/0964-1726/20/10/10501
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