13,791 research outputs found
Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers
We briefly review the recent advances in the rheology of entangled polymers
and identify emerging research trends and outstanding challenges, especially
with respect to branched polymers. Emphasis is placed on the role of
well-characterized model systems, as well as the synergy of
synthesis-characterization, rheometry and modeling/simulations. The theoretical
framework for understanding the observed linear and nonlinear rheological
phenomena is the tube model which is critically assessed in view of its
successes and shortcomings, whereas alternative approaches are briefly
discussed. Finally, intriguing experimental findings and controversial issues
that merit consistent explanation, such as shear banding instabilities,
multiple stress overshoots in transient simple shear and enhanced steady-state
elongational viscosity in polymer solutions, are discussed, whereas future
directions such as branch point dynamics and anisotropic monomeric friction are
outlined.Comment: 25 pages, accepted for publication in Journal of Physics Condensed
Matter (August 2015
Micro Coriolis mass flow censor with extended range for a monopropellant micro propulsion system
We have designed and realised a micromachined micro Coriolis flow sensor for the measurement of hydrazine (N2H4, High Purity Grade) propellant flow in micro chemical propulsion systems. The sensor should be able to measure mass flow up to 6 mg/s for a single thruster or up to 24 mg/s for four thrusters. The sensor will first be used for measurement and characterisation of the micro thruster system in a simulated space vacuum environment. Integration of the sensor chip within the micro thruster flight hardware will be considered at a later stage. The new chip has an increased flow range because of an integrated on-chip bypass channel. First measurement results have demonstrated an increase in flow range which corresponds well to the designed bypass ratio
Genetic algorithm design of neural network and fuzzy logic controllers
Genetic algorithm design of neural network and fuzzy logic controller
Random ultrametric trees and applications
Ultrametric trees are trees whose leaves lie at the same distance from the
root. They are used to model the genealogy of a population of particles
co-existing at the same point in time. We show how the boundary of an
ultrametric tree, like any compact ultrametric space, can be represented in a
simple way via the so-called comb metric. We display a variety of examples of
random combs and explain how they can be used in applications. In particular,
we review some old and recent results regarding the genetic structure of the
population when throwing neutral mutations on the skeleton of the tree.Comment: 20 pages, 7 figures, proceedings of MAS 2016, Grenoble, France
(Stochastic modeling and Statistics Conference, French Society for Applied
and Industrial Math, SMAI
Theoretical framework for quantum networks
We present a framework to treat quantum networks and all possible
transformations thereof, including as special cases all possible manipulations
of quantum states, measurements, and channels, such as, e.g., cloning,
discrimination, estimation, and tomography. Our framework is based on the
concepts of quantum comb-which describes all transformations achievable by a
given quantum network-and link product-the operation of connecting two quantum
networks. Quantum networks are treated both from a constructive point of
view-based on connections of elementary circuits-and from an axiomatic
one-based on a hierarchy of admissible quantum maps. In the axiomatic context a
fundamental property is shown, which we call universality of quantum memory
channels: any admissible transformation of quantum networks can be realized by
a suitable sequence of memory channels. The open problem whether this property
fails for some nonquantum theory, e.g., for no-signaling boxes, is posed.Comment: 23 pages, revtex
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