125,382 research outputs found
Yielding dynamics of a Herschel-Bulkley fluid: a critical-like fluidization behaviour
The shear-induced fluidization of a carbopol microgel is investigated during
long start-up experiments using combined rheology and velocimetry in Couette
cells of varying gap widths and boundary conditions. As already described in
[Divoux et al., {\it Phys. Rev. Lett.}, 2010, {\bf 104}, 208301], we show that
the fluidization process of this simple yield stress fluid involves a transient
shear-banding regime whose duration decreases as a power law of the
applied shear rate \gp. Here we go one step further by an exhaustive
investigation of the influence of the shearing geometry through the gap width
and the boundary conditions. While slip conditions at the walls seem to
have a negligible influence on the fluidization time , different
fluidization processes are observed depending on \gp and : the shear band
remains almost stationary for several hours at low shear rates or small gap
widths before strong fluctuations lead to a homogeneous flow, whereas at larger
values of \gp or , the transient shear band is seen to invade the whole
gap in a much smoother way. Still, the power-law behaviour appears as very
robust and hints to critical-like dynamics. To further discuss these results,
we propose (i) a qualitative scenario to explain the induction-like period that
precedes full fluidization and (ii) an analogy with critical phenomena that
naturally leads to the observed power laws if one assumes that the yield point
is the critical point of an underlying out-of-equilibrium phase transition.Comment: 16 pages, 14+2 figures, published in Soft Matte
Mechano-electric heterogeneity of the myocardium as a paradigm of its function
Myocardial heterogeneity is well appreciated and widely documented, from sub-cellular to organ levels. This paper reviews significant achievements of the group, led by Professor Vladimir S. Markhasin, Russia, who was one of the pioneers in studying and interpreting the relevance of cardiac functional heterogeneity
A Robust Zero-Calibration RF-based Localization System for Realistic Environments
Due to the noisy indoor radio propagation channel, Radio Frequency (RF)-based
location determination systems usually require a tedious calibration phase to
construct an RF fingerprint of the area of interest. This fingerprint varies
with the used mobile device, changes of the transmit power of smart access
points (APs), and dynamic changes in the environment; requiring re-calibration
of the area of interest; which reduces the technology ease of use. In this
paper, we present IncVoronoi: a novel system that can provide zero-calibration
accurate RF-based indoor localization that works in realistic environments. The
basic idea is that the relative relation between the received signal strength
from two APs at a certain location reflects the relative distance from this
location to the respective APs. Building on this, IncVoronoi incrementally
reduces the user ambiguity region based on refining the Voronoi tessellation of
the area of interest. IncVoronoi also includes a number of modules to
efficiently run in realtime as well as to handle practical deployment issues
including the noisy wireless environment, obstacles in the environment,
heterogeneous devices hardware, and smart APs. We have deployed IncVoronoi on
different Android phones using the iBeacons technology in a university campus.
Evaluation of IncVoronoi with a side-by-side comparison with traditional
fingerprinting techniques shows that it can achieve a consistent median
accuracy of 2.8m under different scenarios with a low beacon density of one
beacon every 44m2. Compared to fingerprinting techniques, whose accuracy
degrades by at least 156%, this accuracy comes with no training overhead and is
robust to the different user devices, different transmit powers, and over
temporal changes in the environment. This highlights the promise of IncVoronoi
as a next generation indoor localization system.Comment: 9 pages, 13 figures, published in SECON 201
Economic Cooperation in ASEAN and the Rise of China
Over the past decade, the Association of Southeast Asian
Nations (ASEAN) has shifted from its original focus on
regional peace and stability toward embracing a progressively
economics-dominated agenda. A multitude of initiatives
concerning cooperation in the areas of trade and finance have
been launched. At the 2003 ASEAN Summit in Bali, ASEAN
leaders even declared the goal of establishing an ASEAN
Economic Community by 2020. This paper discusses two
factors that have contributed to ASEAN's increasing focus on
economic cooperation: (1) the Asian financial crisis, and (2)
the emergence of China as a major international and economic
power. It is argued that these determinants have paved the way
for closer economic cooperation within the region despite the
great heterogeneity and conflicting interests of the ASEAN
member countries
Metastability at the Yield-Stress Transition in Soft Glasses
We study the solid-to-liquid transition in a two-dimensional fully periodic
soft-glassy model with an imposed spatially heterogeneous stress. The model we
consider consists of droplets of a dispersed phase jammed together in a
continuous phase. When the peak value of the stress gets close to the yield
stress of the material, we find that the whole system intermittently tunnels to
a metastable "fluidized" state, which relaxes back to a metastable "solid"
state by means of an elastic-wave dissipation. This macroscopic scenario is
studied through the microscopic displacement field of the droplets, whose time
statistics displays a remarkable bimodality. Metastability is rooted in the
existence, in a given stress range, of two distinct stable rheological branches
as well as long-range correlations (e.g., large dynamic heterogeneity)
developed in the system. Finally, we show that a similar behavior holds for a
pressure-driven flow, thus suggesting possible experimental tests.Comment: 13 pages, 11 figure
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