11,537 research outputs found
Dilatancy, Jamming, and the Physics of Granulation
Granulation is a process whereby a dense colloidal suspension is converted
into pasty granules (surrounded by air) by application of shear. Central to the
stability of the granules is the capillary force arising from the interfacial
tension between solvent and air. This force appears capable of maintaining a
solvent granule in a jammed solid state, under conditions where the same amount
of solvent and colloid could also exist as a flowable droplet. We argue that in
the early stages of granulation the physics of dilatancy, which requires that a
powder expand on shearing, is converted by capillary forces into the physics of
arrest. Using a schematic model of colloidal arrest under stress, we speculate
upon various jamming and granulation scenarios. Some preliminary experimental
results on aspects of granulation in hard-sphere colloidal suspensions are also
reported.Comment: Original article intended for J Phys Cond Mat special issue on
Granular Materials (M Nicodemi, Ed.
Validity and User Experience in an Augmented Reality Virtual Tooth Identification Test
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153623/1/jddjde019139.pd
Exploring the needs, concerns and knowledge of women diagnosed with gestational diabetes: A qualitative study
Parabolic resonances and instabilities in near-integrable two degrees of freedom Hamiltonian flows
When an integrable two-degrees-of-freedom Hamiltonian system possessing a
circle of parabolic fixed points is perturbed, a parabolic resonance occurs. It
is proved that its occurrence is generic for one parameter families
(co-dimension one phenomenon) of near-integrable, t.d.o. systems. Numerical
experiments indicate that the motion near a parabolic resonance exhibits new
type of chaotic behavior which includes instabilities in some directions and
long trapping times in others. Moreover, in a degenerate case, near a {\it flat
parabolic resonance}, large scale instabilities appear. A model arising from an
atmospherical study is shown to exhibit flat parabolic resonance. This supplies
a simple mechanism for the transport of particles with {\it small} (i.e.
atmospherically relevant) initial velocities from the vicinity of the equator
to high latitudes. A modification of the model which allows the development of
atmospherical jets unfolds the degeneracy, yet traces of the flat instabilities
are clearly observed
Proper orthogonal decomposition of solar photospheric motions
The spatio-temporal dynamics of the solar photosphere is studied by
performing a Proper Orthogonal Decomposition (POD) of line of sight velocity
fields computed from high resolution data coming from the MDI/SOHO instrument.
Using this technique, we are able to identify and characterize the different
dynamical regimes acting in the system. Low frequency oscillations, with
frequencies in the range 20-130 microHz, dominate the most energetic POD modes
(excluding solar rotation), and are characterized by spatial patterns with
typical scales of about 3 Mm. Patterns with larger typical scales of 10 Mm, are
associated to p-modes oscillations at frequencies of about 3000 microHz.Comment: 8 figures in jpg in press on PR
Quantum Dynamics of Three Coupled Atomic Bose-Einstein Condensates
The simplest model of three coupled Bose-Einstein Condensates (BEC) is
investigated using a group theoretical method. The stationary solutions are
determined using the SU(3) group under the mean field approximation. This
semiclassical analysis using the system symmetries shows a transition in the
dynamics of the system from self trapping to delocalization at a critical value
for the coupling between the condensates. The global dynamics are investigated
by examination of the stable points and our analysis shows the structure of the
stable points depends on the ratio of the condensate coupling to the
particle-particle interaction, undergoes bifurcations as this ratio is varied.
This semiclassical model is compared to a full quantum treatment, which also
displays the dynamical transition. The quantum case has collapse and revival
sequences superposed on the semiclassical dynamics reflecting the underlying
discreteness of the spectrum. Non-zero circular current states are also
demonstrated as one of the higher dimensional effects displayed in this system.Comment: Accepted to PR
Attitude towards condom use and HIV/AIDS knowledge as potential determinants of condom use self-efficacy among hispanic youths
Banking from Leeds, not London: regional strategy and structure at the Yorkshire Bank, 1859–1952
Industrial philanthropist Edward Akroyd created the Yorkshire Penny Savings Bank in 1859. Despite competition from the Post Office Savings Bank after 1861 and a serious reserve problem in 1911, it sustained his overall strategy to become a successful regional bank. Using archival and contemporary sources to build on recent scholarship illustrating how savings banks were integrated into local economies and the complementary roles of philanthropy and paternalism, we analyse an English regional bank's strategy, including an assessment of strategic innovation, ownership changes and management structure. This will demonstrate that the founder's vision continued, even though the 1911 crisis radically altered both strategy and structure
Model Order Reduction for Rotating Electrical Machines
The simulation of electric rotating machines is both computationally
expensive and memory intensive. To overcome these costs, model order reduction
techniques can be applied. The focus of this contribution is especially on
machines that contain non-symmetric components. These are usually introduced
during the mass production process and are modeled by small perturbations in
the geometry (e.g., eccentricity) or the material parameters. While model order
reduction for symmetric machines is clear and does not need special treatment,
the non-symmetric setting adds additional challenges. An adaptive strategy
based on proper orthogonal decomposition is developed to overcome these
difficulties. Equipped with an a posteriori error estimator the obtained
solution is certified. Numerical examples are presented to demonstrate the
effectiveness of the proposed method
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