185,559 research outputs found
Interface Simulation Distances
The classical (boolean) notion of refinement for behavioral interfaces of
system components is the alternating refinement preorder. In this paper, we
define a distance for interfaces, called interface simulation distance. It
makes the alternating refinement preorder quantitative by, intuitively,
tolerating errors (while counting them) in the alternating simulation game. We
show that the interface simulation distance satisfies the triangle inequality,
that the distance between two interfaces does not increase under parallel
composition with a third interface, and that the distance between two
interfaces can be bounded from above and below by distances between
abstractions of the two interfaces. We illustrate the framework, and the
properties of the distances under composition of interfaces, with two case
studies.Comment: In Proceedings GandALF 2012, arXiv:1210.202
Solvent-mediated interactions between nanoparticles at fluid interfaces
We investigate the solvent mediated interactions between nanoparticles
adsorbed at a liquid-vapor interface in comparison to the solvent mediated
interactions in the bulk liquid and vapor phases of a Lennard-Jones solvent.
Molecular dynamics simulation data for the latter are in good agreement with
results from integral equations in the reference functional approximation and a
simple geometric approximation. Simulation results for the solvent mediated
interactions at the interface differ markedly from the interactions of the
particles in the corresponding bulk phases. We find that at short interparticle
distances the interactions are considerably more repulsive than those in either
bulk phase. At long interparticle distances we find evidence for a long-ranged
attraction. We discuss these observations in terms of interfacial interactions,
namely, the three-phase line tension that would operate at short distances, and
capillary wave interactions for longer interparticle distances.Comment: 22 pages, 6 figure
The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like
With molecular simulation for water and a tunable hydrophobic substrate, we
apply the instantaneous interface construction [A. P. Willard and D. Chandler,
J. Phys. Chem. B, 114, 1954 (2010)] to examine the similarity between a
water-vapor interface and a water-hydrophobic surface interface. The intrinsic
interface refers to molecular structure in terms of distances from the
instantaneous interface. We show that attractive interactions between a
hydrophobic surface and water affect capillary wave fluctuations of the
instantaneous liquid interface, but these attractive interactions have
essentially no effect on the intrinsic interface. Further, the intrinsic
interface of liquid water and a hydrophobic substrate differs little from that
of water and its vapor.The same is not true, we show, for an interface between
water and a hydrophilic substrate. In that case, strong directional
substrate-water interactions disrupt the liquid-vapor-like interfacial hydrogen
bonding network.Comment: 6 pages, 5 figure
Risk analysis of LPG tanks at the wildland-urban interface
In areas of wildland-urban interface (WUI), especially residential developments, it is very
common to see liquefied petroleum gas (LPG) tanks, particularly with a higher ratio of
propane, in surface installations serving homes. The most common tanks are between 1 and 5
m3 of capacity, but smaller ones of less than 1 m3 are more frequent. In case of accident,
installations may be subject to fires and explosions, especially in those circumstances where
legal and normative requirements allow very close exposure to flames from vegetable fuel
near LPG tanks.
In this project, it is intended to do a comprehensive diagnosis of the problem, addressing
the compilation of information on real risk scenarios in historical fires. First, a preliminary
presentation of the properties and characteristics of liquefied petroleum gas will be exposed.
Its physical and chemical properties, production methodology, pressure and temperature
diagrams and important considerations will be defined when using this type of substances in a
storage tank of a certain volume.
Next, a review of the situation of the existence of LPG tanks in the urban forest interfaces
will be exposed. In this case, the main accidents caused by problems with the storage of LPG
will be analyzed taking into account the relevance of BLEVE events in this type of incidents. To
do this, the main scenarios that could take place in the event of a fire will be presented.
Next, the existing legislation on the storage of LPG in these environments in some
Mediterranean countries will be studied. In order to develop a comprehensive analysis, the
main safety measures and distances will be considered, as well as the awareness of the
possibility of vegetation material in the vicinity of LPG storage tanks, which is the main
problem that will arise in a possible BLEVE scenario in case of fire. To finalize and facilitate
understanding, a comparative table will be included with the aim of visualizing the main
advantages and legislative deficiencies between the different countries.
Following, the state of the art in terms of modelling LPG accidents at the WUI will be
reviewed. Trying to simulate and predict this type of scenarios, it will see the models normally
chosen to obtain the tolerable values selected and the answers obtained in each case.
Finally, several fire scenarios will be simulated by means of a CFD tool (FDS, Fire Dynamics
Simulator). In these simulations, the wind velocity and the distance of the combustible vegetal
mass to the tank will be controlled in a WUI fire in which there is a tank of fixed dimensions.
The temperature and the heat flow in each of the scenarios will be obtained, and the
differences among the location of the sensors and the characteristics of the scenario will be
analyzed.
As a conclusion, it has been observed that there is a great amount of variables that are
not contemplated by the regulatory organisms and that the existing legislation does not
guarantee the safety of the population in this type of environment. From the simulations
results, variables as temperature should be studied for further characterizations
Subwavelength internal imaging by means of the wire medium
Evanescent wave amplification is observed, for the first time to our
knowledge, inside a half-wavelength-thick wire medium slab used for
subwavelength imaging. The wire medium is analyzed using both a spatially
dispersive finite-difference time-domain (FDTD) method and a full-wave
commercial electromagnetic simulator CST Microwave Studio. In this work we
demonstrate that subwavelength details of a source placed at a distance of
one-tenth of a wavelength from a wire medium slab can be detected inside the
slab with a resolution of approximately one-tenth of a wavelength in spite of
the fact that they cannot be resolved at the front interface of the device, due
to the rapid decay of evanescent spatial harmonics in free space
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