5,900 research outputs found
From zonal flow to convection rolls in Rayleigh-B\'enard convection with free-slip plates
Rayleigh-B\'enard (RB) convection with free-slip plates and horizontally
periodic boundary conditions is investigated using direct numerical
simulations. Two configurations are considered, one is two-dimension (2D) RB
convection and the other one three-dimension (3D) RB convection with a rotating
axis parallel to the plate. We explore the parameter range of Rayleigh numbers
Ra from 10^9Pr1100. We show
that zonal flow, which was observed, for example, by Goluskin \emph{et al}.
\emph{J. Fluid. Mech.} 759, 360-385 (2014) for \Gamma=2\GammaRaPr\Gamma\GammaRa=10^7Pr=0.71\Gamma=8\Gamma = 16\Gamma\Gamma=2\pi by von
Hardenberg \emph{et al}. \emph{Phys. Rev. Lett.} 15, 134501 (2015), completely
disappears for \Gamma=16\Gamma\Gamma =
8$, the convection roll state and the zonal flow state are both statistically
stable. What state is taken depends on the initial conditions, similarly as we
found for the 2D case.Comment: 26 pages, 12 figure
Detection of Gravitational Wave - An Application of Relativistic Quantum Information Theory
We show that a passing gravitational wave may influence the spin entropy and
spin negativity of a system of massive spin-1/2 particles, in a way that is
characteristic of the radiation. We establish the specific conditions under
which this effect may be nonzero. The change in spin entropy and negativity,
however, is extremely small. Here, we propose and show that this effect may be
amplified through entanglement swapping. Relativistic quantum information
theory may have a contribution towards the detection of gravitational wave.Comment: 9 page
Reactive Web policing based on self-organizing maps
Electronic Commerce and Internet Computing Lab, Department of ComputingRefereed conference paper2001-2002 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe
Exploiting the Synergy Between Gossiping and Structured Overlays
In this position paper we argue for exploiting the synergy between gossip-based algorithms and structured overlay networks (SON). These two strands of research have both aimed at building fault-tolerant, dynamic, self-managing, and large-scale distributed systems. Despite the common goals, the two areas have, however, been relatively isolated. We focus on three problem domains where there is an untapped potential of using gossiping combined with SONs. We argue for applying gossip-based membership for ring-based SONs---such as Chord and Bamboo---to make them handle partition mergers and loopy networks. We argue that small world SONs---such as Accordion and Mercury---are specifically well-suited for gossip-based membership management. The benefits would be better graph-theoretic properties. Finally, we argue that gossip-based algorithms could use the overlay constructed by SONs. For example, many unreliable broadcast algorithms for SONs could be augmented with anti-entropy protocols. Similarly, gossip-based aggregation could be used in SONs for network size estimation and load-balancing purposes
A millimeter-wave antireflection coating for cryogenic silicon lenses
We have developed and tested an antireflection (AR) coating method for
silicon lenses at cryogenic temperatures and millimeter wavelengths. Our
particular application is a measurement of the cosmic microwave background. The
coating consists of machined pieces of Cirlex glued to the silicon. The
measured reflection from an AR coated flat piece is less than 1.5% at the
design wavelength. The coating has been applied to flats and lenses and has
survived multiple thermal cycles from 300 to 4 K. We present the manufacturing
method, the material properties, the tests performed, and estimates of the loss
that can be achieved in practical lenses
Getting published: group support for academic librarians
Purpose - The purpose of this paper is to offer an effective model for increasing professionals' competence, enthusiasm and success in writing and publishing. Design/methodology/approach - Recent articles on writing groups in the field of library and information science are reviewed and a case study of a group at RMIT University Library is presented. The authors were the facilitator and group members who were librarians, most with relative inexperience in research, writing, presenting, and getting published. A self-rating confidence survey was created to establish developmental priorities which were then addressed through input from experts, practical application and reflection, and constructive advice and support from group members. Group effectiveness and outcomes were evaluated at mid- and end-point review meetings, through a post-intervention confidence survey and by tracking publication output. Findings - The group became a cohesive, task-focused and productive team. A post-intervention confidence survey evidenced improvements on all survey items at a team level. Each member affirmed that they had gained substantial knowledge of writing, presentation and research techniques and understanding of the publication process. Publication output increased over the benchmark year of 2010, and in 2011 and 2012 exceeded initial targets. Practical implications - The model presented offers a practical and effective approach to increasing competence and output in writing, presenting, research, and getting published and can be easily adopted by others. Originality/value - Most literature reviews on library professional writing groups relate to professionals required to publish. The Get Published Group comprised Australian librarians writing voluntarily
From Rayleigh-B\'enard convection to porous-media convection: how porosity affects heat transfer and flow structure
We perform a numerical study of the heat transfer and flow structure of
Rayleigh-B\'enard (RB) convection in (in most cases regular) porous media,
which are comprised of circular, solid obstacles located on a square lattice.
This study is focused on the role of porosity in the flow properties
during the transition process from the traditional RB convection with
(so no obstacles included) to Darcy-type porous-media convection with
approaching 0. Simulations are carried out in a cell with unity aspect ratio,
for the Rayleigh number from to and varying porosities
, at a fixed Prandtl number , and we restrict ourselves to the
two dimensional case. For fixed , the Nusselt number is found to vary
non-monotonously as a function of ; namely, with decreasing , it
first increases, before it decreases for approaching 0. The
non-monotonous behaviour of originates from two competing effects of
the porous structure on the heat transfer. On the one hand, the flow coherence
is enhanced in the porous media, which is beneficial for the heat transfer. On
the other hand, the convection is slowed down by the enhanced resistance due to
the porous structure, leading to heat transfer reduction. For fixed ,
depending on , two different heat transfer regimes are identified, with
different effective power-law behaviours of vs , namely, a steep one
for low when viscosity dominates, and the standard classical one for large
. The scaling crossover occurs when the thermal boundary layer thickness
and the pore scale are comparable. The influences of the porous structure on
the temperature and velocity fluctuations, convective heat flux, and energy
dissipation rates are analysed, further demonstrating the competing effects of
the porous structure to enhance or reduce the heat transfer
The timed barium swallow and its relationship to symptoms in achalasia: Analysis of surface area and emptying rate
BACKGROUND: Timed barium swallow (TBS) is used to objectively measure response following achalasia therapy; however, findings can be discordant with symptoms. We hypothesized that measurement of surface area of the residual barium column would improve its utility in measuring outcome. METHODS: In a single-center cohort, achalasia patients undergoing therapy between September 2015-2016 who had TBS were included. Four metrics of emptying were studied: Post-therapy residual barium (a) absolute height and (b) surface area and percentage reduction in (c) residual height (%H) and (d) surface area (%SA) compared to pretherapy. Metrics were evaluated against symptom response (Eckardt score). KEY RESULTS: Twenty-four achalasics (median age 43 year; 13 males) were included; 14 received pneumatic dilatation, and 10 had peroral endoscopic myotomy. Treatment resulted in significant reduction in median Eckardt score (7 to 1; P = .03), mean residual barium column height (14.7 ± 8.7 to 7.9 ± 6.0 cm; P = .01) and surface area (52.7 ± 43.5 to 24.5 ± 23.6 cm2 ; P = .02). There were 4 (17%) initial non-responders (Eckardt > 3). % SA was best at discriminating between responders and non-responders (area under curve 0.85 ± 0.08; sensitivity 100%, specificity 80%). Concordance with symptomatic response following therapy was 83% when using 45% as the cutoff for surface area reduction compared to pretherapy. Eight patients whose static barium height was discordant with symptoms became concordant when % SA was used as a measure of response. CONCLUSIONS & INFERENCES: Change in barium surface area is a superior measure of esophageal emptying and better correlates with treatment response than the conventional 5-minute barium height in defining objective response to achalasia therapy
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