4,201 research outputs found
Bidirectional transport on a dynamic lattice
Bidirectional variants of stochastic many particle models for transport by
molecular motors show a strong tendency to form macroscopic clusters on static
lattices. Inspired by the fact that the microscopic tracks for molecular motors
are dynamical, we study the influence of different types of lattice dynamics on
stochastic bidirectional transport. We observe a transition toward efficient
transport (corresponding to the dissolution of large clusters) controlled by
the lattice dynamics.Comment: 5 pages, 5 figure
A Requirement-centric Approach to Web Service Modeling, Discovery, and Selection
Service-Oriented Computing (SOC) has gained considerable popularity for implementing Service-Based Applications (SBAs) in a flexible\ud
and effective manner. The basic idea of SOC is to understand users'\ud
requirements for SBAs first, and then discover and select relevant\ud
services (i.e., that fit closely functional requirements) and offer\ud
a high Quality of Service (QoS). Understanding users requirements\ud
is already achieved by existing requirement engineering approaches\ud
(e.g., TROPOS, KAOS, and MAP) which model SBAs in a requirement-driven\ud
manner. However, discovering and selecting relevant and high QoS\ud
services are still challenging tasks that require time and effort\ud
due to the increasing number of available Web services. In this paper,\ud
we propose a requirement-centric approach which allows: (i) modeling\ud
users requirements for SBAs with the MAP formalism and specifying\ud
required services using an Intentional Service Model (ISM); (ii)\ud
discovering services by querying the Web service search engine Service-Finder\ud
and using keywords extracted from the specifications provided by\ud
the ISM; and(iii) selecting automatically relevant and high QoS services\ud
by applying Formal Concept Analysis (FCA). We validate our approach\ud
by performing experiments on an e-books application. The experimental\ud
results show that our approach allows the selection of relevant and\ud
high QoS services with a high accuracy (the average precision is\ud
89.41%) and efficiency (the average recall is 95.43%)
Entangled single-wire NiTi material: a porous metal with tunable superelastic and shape memory properties
NiTi porous materials with unprecedented superelasticity and shape memory
were manufactured by self-entangling, compacting and heat treating NiTi wires.
The versatile processing route used here allows to produce entanglements of
either superelastic or ferroelastic wires with tunable mesostructures. Three
dimensional (3D) X-ray microtomography shows that the entanglement
mesostructure is homogeneous and isotropic. The thermomechanical compressive
behavior of the entanglements was studied using optical measurements of the
local strain field. At all relative densities investigated here ( 25 -
40), entanglements with superelastic wires exhibit remarkable macroscale
superelasticity, even after compressions up to 25, large damping capacity,
discrete memory effect and weak strain-rate and temperature dependencies.
Entanglements with ferroelastic wires resemble standard elastoplastic fibrous
systems with pronounced residual strain after unloading. However, a full
recovery is obtained by heating the samples, demonstrating a large shape memory
effect at least up to 16% strain.Comment: 31 pages, 10 figures, submitted to Acta Materiali
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Numerical simulations of the convective dilution process in helium-rich white dwarfs
The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018DB and DBA white dwarfs are generally believed to
be the result of a process by which a thin radiative hydrogen
atmosphere floating in diffusive equilibrium
on top of a helium envelope is eventually completely
diluted in the underlying more massive helium convection
zone that develops with cooling. However,
the observed hydrogen abundances in these objects
exceed by several orders of magnitude the predictions
obtained from such a scenario invoking diffusive
equilibrium, thus currently leaving the very existence
of DB and DBA white dwarfs unaccounted
for in any satisfactory way. We present here the results
of new numerical simulations aimed at improving
the modeling of this convective dilution process.
In particular, we show how DA white dwarfs can be
transformed into DB stars below 20,000 K, and more
importantly, we propose a model that predicts the
correct amount of hydrogen observed in DBA stars
without invoking any accretion mechanism, an alternative
model that has been proposed over the years
to account qualitatively for the presence of hydrogen
in the atmospheres of DBA stars.Astronom
Optical versus video see-through mead-mounted displays in medical visualization
We compare two technological approaches to augmented reality for 3-D medical visualization: optical and video see-through devices. We provide a context to discuss the technology by reviewing several medical applications of augmented-reality research efforts driven by real needs in the medical field, both in the United States and in Europe. We then discuss the issues for each approach, optical versus video, from both a technology and human-factor point of view. Finally, we point to potentially promising future developments of such devices including eye tracking and multifocus planes capabilities, as well as hybrid optical/video technology
Particle interactions and lattice dynamics: Scenarios for efficient bidirectional stochastic transport?
Intracellular transport processes driven by molecular motors can be described
by stochastic lattice models of self-driven particles. Here we focus on
bidirectional transport models excluding the exchange of particles on the same
track. We explore the possibility to have efficient transport in these systems.
One possibility would be to have appropriate interactions between the various
motors' species, so as to form lanes. However, we show that the lane formation
mechanism based on modified attachment/detachment rates as it was proposed
previously is not necessarily connected to an efficient transport state and is
suppressed when the diffusivity of unbound particles is finite. We propose
another interaction mechanism based on obstacle avoidance that allows to have
lane formation for limited diffusion. Besides, we had shown in a separate paper
that the dynamics of the lattice itself could be a key ingredient for the
efficiency of bidirectional transport. Here we show that lattice dynamics and
interactions can both contribute in a cooperative way to the efficiency of
transport. In particular, lattice dynamics can decrease the interaction
threshold beyond which lanes form. Lattice dynamics may also enhance the
transport capacity of the system even when lane formation is suppressed.Comment: 25 pages, 17 figures, 2 table
Aquatic animal health professional certification schemes: Some options for the Asian fish health community
Many governments are under increasing pressure from international trading partners to provide better information on the health status of exported aquatic animal commodities, particularly live animals. A central factor in this situation involves the training and certification of various links in the Competent Authority chain-of-command, including aquatic health service providers, aquatic pathogen detection laboratories, aquatic species pathologists, veterinarians and personnel who facilitate the endorsement of aquatic animal certificates of inspection. Standardized methods to ensure the competence of those people charged with providing and interpreting information on the health status of aquatic animals and/or their products for export is imperative to maintain the confidence of international trading partners. A thorough and logical certification protocol for aquatic animal health personnel would lend additional credibility and assuredness/peace of mind to the importer/consumer in the quality of the product and the production of health certificates of instantly recognizable meaning. Existing professional certification programs for aquatic animal health providers will be reviewed. These programs could provide guidance as a Professional Standards establishing mechanism for veterinarians and non-veterinary personnel in Asia who currently provide aquatic animal health services. This paper proposes a professional standards mechanism, developed through NACA and the Asian Fisheries Society-Fish Health Section (AFS-FHS), to promote and authorize a certification protocol for aquatic animal health providers in Asia as highly useful in improving this situation
Antibunched photons emitted by a dc-biased Josephson junction
We show experimentally that a dc biased Josephson junction in series with a high-enough-impedance microwave resonator emits antibunched photons. Our resonator is made of a simple microfabricated spiral coil that resonates at 4.4 GHz and reaches a 1.97kΩ characteristic impedance. The second order correlation function of the power leaking out of the resonator drops down to 0.3 at zero delay, which demonstrates the antibunching of the photons emitted by the circuit at a rate of 6×10^7 photons per second. Results are found in quantitative agreement with our theoretical predictions. This simple scheme could offer an efficient and bright single-photon source in the microwave domain
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