1,185 research outputs found
Gas flows through shallow T-junctions and parallel microchannel networks
We apply a recent extension of the Hele-Shaw scheme to analyze steady compressible viscous flows
through micro T-junctions. The linearity of the problem in terms of an appropriately defined
quadratic form of the pressure facilitates the definition of the viscous resistance of the configuration,
relating the gas mass-flow rate to entrance and exit conditions. Furthermore, under rather mild
restrictions, the performance of complex microchannel networks may be estimated through
superposition of the contributions of multiple basic junction elements. This procedure is applied to
an optimization model problem of a parallel microchannel network. The analysis and results are
readily adaptable to incompressible flows
Elasto-capillary coalescence of multiple parallel sheets
We analyse two-dimensional clamped parallel elastic sheets which are partially immersed in liquid as a model for elasto-capillary coalescence. In the existing literature this problem is studied via minimal energy analysis of capillary and elastic energies of the post-coalescence state, yielding the maximal stable post-coalescence bundle size. Utilizing modal stability analysis and asymptotic analysis, we studied the stability of the configuration before the coalescence occurred. Our analysis revealed previously unreported relations between viscous forces, body forces, and the instability yielding the coalescence, thus undermining a common assumption that coalescence will occur as long as it will not create a bundle larger than the maximal stable post-coalesced size. A mathematical description of the process creating the hierarchical coalescence structure was obtained and yielded that the mean number of sheets per coalesced region is limited to the subset 2^N where N is the set of natural numbers. Our theoretical results were illustrated by experiments and good agreement with the theoretical predictions was observed
A comparison between pulsed and CW laser annealing for solar cell applications
The application of laser processing in solar cell fabrication is considered. Specific emphasis is placed on a process developed for the fabrication of a 16.6% silicon solar cell using pulsed laser processing. Results are presented which compare pulsed laser annealing with CW laser annealing in solar cell fabrication
MORPH: A Reference Architecture for Configuration and Behaviour Self-Adaptation
An architectural approach to self-adaptive systems involves runtime change of
system configuration (i.e., the system's components, their bindings and
operational parameters) and behaviour update (i.e., component orchestration).
Thus, dynamic reconfiguration and discrete event control theory are at the
heart of architectural adaptation. Although controlling configuration and
behaviour at runtime has been discussed and applied to architectural
adaptation, architectures for self-adaptive systems often compound these two
aspects reducing the potential for adaptability. In this paper we propose a
reference architecture that allows for coordinated yet transparent and
independent adaptation of system configuration and behaviour
GRB afterglow blast wave encountering sudden circumburst density change produces no flares
Afterglows of gamma-ray bursts are observed to produce light curveswith the flux following power law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days.One proposed explanation for these flares is the interaction of a relativisticblast wave with a circumburst density transition. In this paper, we modelthis type of interaction computationally in one and two dimensions, usinga relativistic hydrodynamics code with adaptive mesh refinement calledram, and analytically in one dimension. We simulate a blast wave travelingin a stellar wind environment that encounters a sudden change indensity, followed by a homogeneous medium, and compute the observedradiation using a synchrotron model. We show that flares are not observablefor an encounter with a sudden density increase, such as a windtermination shock, nor for an encounter with a sudden density decrease.Furthermore, by extending our analysis to two dimensions, we are able toresolve the spreading, collimation, and edge effects of the blast wave as itencounters the change in circumburst medium. In all cases considered inthis paper, we find that a flare will not be observed for any of the densitychanges studied
A frictionless microswimmer
We investigate the self-locomotion of an elongated microswimmer by virtue of
the unidirectional tangential surface treadmilling. We show that the propulsion
could be almost frictionless, as the microswimmer is propelled forward with the
speed of the backward surface motion, i.e. it moves throughout an almost
quiescent fluid. We investigate this swimming technique using the special
spheroidal coordinates and also find an explicit closed-form optimal solution
for a two-dimensional treadmiler via complex-variable techniques.Comment: 6 pages, 4 figure
Quantum versus classical phase-locking transition in a driven-chirped oscillator
Classical and quantum-mechanical phase locking transition in a nonlinear
oscillator driven by a chirped frequency perturbation is discussed. Different
limits are analyzed in terms of the dimensionless parameters and
( and being the driving amplitude,
the frequency chirp rate, the nonlinearity parameter and the linear frequency
of the oscillator). It is shown that for , the passage
through the linear resonance for above a threshold yields classical
autoresonance (AR) in the system, even when starting in a quantum ground state.
In contrast, for , the transition involves
quantum-mechanical energy ladder climbing (LC). The threshold for the
phase-locking transition and its width in in both AR and LC limits are
calculated. The theoretical results are tested by solving the Schrodinger
equation in the energy basis and illustrated via the Wigner function in phase
space
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