133 research outputs found
Transient behavior of the thermocapillary migration of drops under the influence of deformation
The transient thermocapillary migration of drops with nontrivial deformation
is studied. The finite difference method is employed to solve the
incompressible Navier-Stokes equations coupled with the energy equation; the
front-tracking method is adopted to track the moving deformable drop interface.
In the hot region, deformations of drops increase with the decrease of
interfacial tensions. In order to indicate the temperature impact on the
interfacial tension, a local capillary number () is introduced. It is
found that, when the drop density is smaller/larger than that of the bulk
fluid, the drop velocity decreases/increases with the increase of the drop
deformation.Comment: 18 pages, 14 figures. The Chinese version of this paper has been
accepted by "Scientia Sinica: Physica, Mechanica & Astronomica
Bifurcation analysis of a free boundary model of vascular tumor growth with a necrotic core and chemotaxis
A considerable number of research works has been devoted to the study of
tumor models. Several biophysical factors, such as cell proliferation,
apoptosis, chemotaxis, angiogenesis and necrosis, have been discovered to have
an impact on the complicated biological system of tumors. An indicator of the
aggressiveness of tumor development is the instability of the shape of the
tumor boundary. Complex patterns of tumor morphology have been explored by Lu,
Min-Jhe et al. [Nonlinear simulation of vascular tumor growth with chemotaxis
and the control of necrosis, Journal of Computational Physics 459 (2022):
111153]. In this paper, we continue to carry out a bifurcation analysis on such
a vascular tumor model with a controlled necrotic core and chemotaxis. This
bifurcation analysis, to the parameter of cell proliferation, is built on the
explicit formulas of radially symmetric steady-state solutions. By perturbing
the tumor free boundary and establishing rigorous estimates of the free
boundary system, %applying the Hanzawa transformation, we prove the existence
of the bifurcation branches with Crandall-Rabinowitz theorem. The parameter of
chemotaxis is found to influence the monotonicity of the bifurcation point as
the mode increases both theoretically and numerically.Comment: 26 pages, 4 figure
Undermining User Privacy on Mobile Devices Using AI
Over the past years, literature has shown that attacks exploiting the
microarchitecture of modern processors pose a serious threat to the privacy of
mobile phone users. This is because applications leave distinct footprints in
the processor, which can be used by malware to infer user activities. In this
work, we show that these inference attacks are considerably more practical when
combined with advanced AI techniques. In particular, we focus on profiling the
activity in the last-level cache (LLC) of ARM processors. We employ a simple
Prime+Probe based monitoring technique to obtain cache traces, which we
classify with Deep Learning methods including Convolutional Neural Networks. We
demonstrate our approach on an off-the-shelf Android phone by launching a
successful attack from an unprivileged, zeropermission App in well under a
minute. The App thereby detects running applications with an accuracy of 98%
and reveals opened websites and streaming videos by monitoring the LLC for at
most 6 seconds. This is possible, since Deep Learning compensates measurement
disturbances stemming from the inherently noisy LLC monitoring and unfavorable
cache characteristics such as random line replacement policies. In summary, our
results show that thanks to advanced AI techniques, inference attacks are
becoming alarmingly easy to implement and execute in practice. This once more
calls for countermeasures that confine microarchitectural leakage and protect
mobile phone applications, especially those valuing the privacy of their users
Manipulating Multiple Order Parameters via Oxygen Vacancies: The case of Eu0.5Ba0.5TiO3-{\delta}
Controlling functionalities, such as magnetism or ferroelectricity, by means
of oxygen vacancies (VO) is a key issue for the future development of
transition metal oxides. Progress in this field is currently addressed through
VO variations and their impact on mainly one order parameter. Here we reveal a
new mechanism for tuning both magnetism and ferroelectricity simultaneously by
using VO. Combined experimental and density-functional theory studies of
Eu0.5Ba0.5TiO3-{\delta}, we demonstrate that oxygen vacancies create Ti3+ 3d1
defect states, mediating the ferromagnetic coupling between the localized Eu
4f7 spins, and increase an off-center displacement of Ti ions, enhancing the
ferroelectric Curie temperature. The dual function of Ti sites also promises a
magnetoelectric coupling in the Eu0.5Ba0.5TiO3-{\delta}.Comment: Accepted by Physical Review B, 201
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