180 research outputs found
Island Loss for Learning Discriminative Features in Facial Expression Recognition
Over the past few years, Convolutional Neural Networks (CNNs) have shown
promise on facial expression recognition. However, the performance degrades
dramatically under real-world settings due to variations introduced by subtle
facial appearance changes, head pose variations, illumination changes, and
occlusions.
In this paper, a novel island loss is proposed to enhance the discriminative
power of the deeply learned features. Specifically, the IL is designed to
reduce the intra-class variations while enlarging the inter-class differences
simultaneously. Experimental results on four benchmark expression databases
have demonstrated that the CNN with the proposed island loss (IL-CNN)
outperforms the baseline CNN models with either traditional softmax loss or the
center loss and achieves comparable or better performance compared with the
state-of-the-art methods for facial expression recognition.Comment: 8 pages, 3 figure
Optimizing Filter Size in Convolutional Neural Networks for Facial Action Unit Recognition
Recognizing facial action units (AUs) during spontaneous facial displays is a
challenging problem. Most recently, Convolutional Neural Networks (CNNs) have
shown promise for facial AU recognition, where predefined and fixed convolution
filter sizes are employed. In order to achieve the best performance, the
optimal filter size is often empirically found by conducting extensive
experimental validation. Such a training process suffers from expensive
training cost, especially as the network becomes deeper.
This paper proposes a novel Optimized Filter Size CNN (OFS-CNN), where the
filter sizes and weights of all convolutional layers are learned simultaneously
from the training data along with learning convolution filters. Specifically,
the filter size is defined as a continuous variable, which is optimized by
minimizing the training loss. Experimental results on two AU-coded spontaneous
databases have shown that the proposed OFS-CNN is capable of estimating optimal
filter size for varying image resolution and outperforms traditional CNNs with
the best filter size obtained by exhaustive search. The OFS-CNN also beats the
CNN using multiple filter sizes and more importantly, is much more efficient
during testing with the proposed forward-backward propagation algorithm
Multi-material topology optimization of adhesive backing layers via J-integral and strain energy minimizations
Strong adhesives rely on reduced stress concentrations, often obtained via
specific geometry or composition of materials. In many examples in nature and
engineering prototypes, the adhesive performance relies on structural rigidity
being placed in specific locations. A few design principles have been
formulated, based on parametric optimization, while a general design tool is
still missing. We propose to use topology optimization to achieve optimal
stiffness distribution in a multi-material adhesive backing layer, reducing
stress concentration at specified locations. The method involves the
minimization of a linear combination of J-integral and strain energy. While the
J-integral minimization is aimed at reducing stress concentration, we observe
that the combination of these two objectives ultimately provides the best
results. We analyze three cases in plane strain conditions, namely (i)
double-edged crack and (ii) center crack in tension and (iii) edge crack under
shear. Each case evidences a different optimal topology with (i) and (ii)
providing similar results. The optimal topology allocates stiffness in regions
that are far away from the crack tip, intuitively, but the allocation of softer
materials over stiffer ones can be non-trivial. To test our solutions, we plot
the contact stress distribution across the interface. In all observed cases, we
eliminate the stress singularity at the crack tip. Stress concentrations might
arise in locations far away from the crack tip, but the final results are
independent of crack size. Our method ultimately provides optimal, flaw
tolerant, adhesives where the crack location is known
Theoretical Puncture Mechanics of Soft Compressible Solids
Accurate prediction of the force required to puncture a soft material is
critical in many fields like medical technology, food processing, and
manufacturing. However, such a prediction strongly depends on our understanding
of the complex nonlinear behavior of the material subject to deep indentation
and complex failure mechanisms. Only recently we developed theories capable of
correlating puncture force with material properties and needle geometry.
However, such models are based on simplifications that seldom limit their
applicability to real cases. One common assumption is the incompressibility of
the cut material, albeit no material is truly incompressible. In this paper we
propose a simple model that accounts for linearly elastic compressibility, and
its interplay with toughness, stiffness, and elastic strain-stiffening.
Confirming previous theories and experiments, materials having high-toughness
and low-modulus exhibit the highest puncture resistance at a given needle
radius. Surprisingly, in these conditions, we observe that incompressible
materials exhibit the lowest puncture resistance, where volumetric
compressibility can create an additional (strain) energy barrier to puncture.
Our model provides a valuable tool to assess the puncture resistance of soft
compressible materials and suggests new design strategies for sharp needles and
puncture-resistant materials
A Vision to Smart Radio Environment: Surface Wave Communication Superhighways
Complementary to traditional approaches that focus on transceiver design for
bringing the best out of unstable, lossy fading channels, one radical
development in wireless communications that has recently emerged is to pursue a
smart radio environment by using software-defined materials or programmable
metasurfaces for establishing favourable propagation conditions. This article
portraits a vision of communication superhighways enabled by surface wave (SW)
propagation on "smart surfaces" for future smart radio environments. The
concept differs from the mainstream efforts of using passive elements on a
large surface for bouncing off radio waves intelligently towards intended user
terminals. In this vision, energy efficiency will be ultra-high, due to much
less pathloss compared to free space propagation, and the fact that SW is
inherently confined to the smart surface not only greatly simplifies the task
of interference management, but also makes possible exceptionally localized
high-speed interference-free data access. We shall outline the opportunities
and associated challenges arisen from the SW paradigm. We shall also attempt to
shed light on several key enabling technologies that make this realizable. One
important technology which will be discussed is a software-controlled fluidic
waveguiding architecture that permits dynamic creation of high-throughput data
highways.Comment: 7 pages, 6 figure
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