333 research outputs found
Epitaxial ferroelectric hafnia stabilized by symmetry constraints
Ferroelectric memories experienced a revival in the last decade due to the
discovery of ferroelectricity in HfO-based nanometer-thick thin films.
These films exhibit exceptional silicon compatibility, overcoming the scaling
and integration obstacles that impeded perovskite ferroelectrics' use in
high-density integrated circuits. The exact phase responsible for
ferroelectricity in hafnia films remains debated with no single factor
identified that could stabilize the ferroelectric phase thermodynamically.
Here, supported by density functional theory (DFT) high-throughput (HT)
calculations that screen a broad range of epitaxial conditions, we demonstrate
conclusively that specific epitaxial conditions achievable with common
substrates such as yttria-stabilized zirconia (YSZ) and SrTiO can favor the
polar Pca2 phase thermodynamically over other polar phases such as R3m and
Pmn2 and nonpolar P2/c phase. The substrate's symmetry
constraint-induced shear strain is crucial for the preference of Pca2. The
strain-stability phase diagrams resolve experiment-theory discrepancies and can
guide the improvement of ferroelectric properties of epitaxial hafnia thin
films
A Non-topological Extension of Bending-immune Valley Topological Edge States
Breaking parity (P) symmetry in C symmetric crystals is a common routine
to implement a valley-topological phase. At an interface between two crystals
of opposite valley phases, the so-called valley topological edge states emerge,
and they have been proven useful for wave transport with robustness against
120 bending and a certain level of disorder. However, whether these
attractive transport features are bound with the valley topology or due to
topological-irrelevant mechanisms remains unclear. In this letter, we discuss
this question by examining transport properties of photonic edge states with
varied degrees of the P-breaking that tune the valley topology, and reveal that
the edge states preserve their transport robustness insensitive to the topology
even when the P-symmetry is recovered. Instead, a unique modal character of the
edge states -- with localized momentum hotspots around high-symmetric
() points -- is recognized to play the key role, which only concerns the
existence of the valleys in the bulk band structures, and has no special
requirement on the topology. The "non-topological" notion of valley edge states
is introduced to conceptualize this modal character, leading to a coherent
understanding of bending immunity in a range of edge modes implemented in C
symmetric crystals -- such as valley topological edge states, topological edge
states of 2D Zak phase, topological-trivial edge states and so on, and to new
designs in general rhombic lattices -- with exemplified bending angle as large
as 150
Benchmarking the Robustness of Quantized Models
Quantization has emerged as an essential technique for deploying deep neural
networks (DNNs) on devices with limited resources. However, quantized models
exhibit vulnerabilities when exposed to various noises in real-world
applications. Despite the importance of evaluating the impact of quantization
on robustness, existing research on this topic is limited and often disregards
established principles of robustness evaluation, resulting in incomplete and
inconclusive findings. To address this gap, we thoroughly evaluated the
robustness of quantized models against various noises (adversarial attacks,
natural corruptions, and systematic noises) on ImageNet. Extensive experiments
demonstrate that lower-bit quantization is more resilient to adversarial
attacks but is more susceptible to natural corruptions and systematic noises.
Notably, our investigation reveals that impulse noise (in natural corruptions)
and the nearest neighbor interpolation (in systematic noises) have the most
significant impact on quantized models. Our research contributes to advancing
the robust quantization of models and their deployment in real-world scenarios.Comment: Workshop at IEEE Conference on Computer Vision and Pattern
Recognition 202
Resilient Data Collection in Smart Grid
Sensors and measurement devices are widely deployed in Smart Grid (SG) to monitor the health of the system. However, these devices are subject to damage and attack so that they cannot deliver sensing data to the control center. In tree-based data collection schemes, a relay failure can further lead to unresponsiveness of all the devices in its sub-tree. In this paper, we study the resiliency issue in collecting data from SG measurement devices. We first design a protocol that guarantees successful data collection from all non-faulty devices in a backup-enabled tree structure. Then, we formulate the tree construction problem to optimize data collection time. Since the formulated problem is NP-hard, we propose a heuristic algorithm to solve it. We evaluate our algorithm using a real utility network topology. The experiment results show that our algorithm performs well in large scale networks.CREDCOpe
RobustMQ: Benchmarking Robustness of Quantized Models
Quantization has emerged as an essential technique for deploying deep neural
networks (DNNs) on devices with limited resources. However, quantized models
exhibit vulnerabilities when exposed to various noises in real-world
applications. Despite the importance of evaluating the impact of quantization
on robustness, existing research on this topic is limited and often disregards
established principles of robustness evaluation, resulting in incomplete and
inconclusive findings. To address this gap, we thoroughly evaluated the
robustness of quantized models against various noises (adversarial attacks,
natural corruptions, and systematic noises) on ImageNet. The comprehensive
evaluation results empirically provide valuable insights into the robustness of
quantized models in various scenarios, for example: (1) quantized models
exhibit higher adversarial robustness than their floating-point counterparts,
but are more vulnerable to natural corruptions and systematic noises; (2) in
general, increasing the quantization bit-width results in a decrease in
adversarial robustness, an increase in natural robustness, and an increase in
systematic robustness; (3) among corruption methods, \textit{impulse noise} and
\textit{glass blur} are the most harmful to quantized models, while
\textit{brightness} has the least impact; (4) among systematic noises, the
\textit{nearest neighbor interpolation} has the highest impact, while bilinear
interpolation, cubic interpolation, and area interpolation are the three least
harmful. Our research contributes to advancing the robust quantization of
models and their deployment in real-world scenarios.Comment: 15 pages, 7 figure
Rotating Objects via In-Hand Pivoting using Vision, Force and Touch
We propose a robotic manipulation system that can pivot objects on a surface
using vision, wrist force and tactile sensing. We aim to control the rotation
of an object around the grip point of a parallel gripper by allowing rotational
slip, while maintaining a desired wrist force profile. Our approach runs an
end-effector position controller and a gripper width controller concurrently in
a closed loop. The position controller maintains a desired force using vision
and wrist force. The gripper controller uses tactile sensing to keep the grip
firm enough to prevent translational slip, but loose enough to induce
rotational slip. Our sensor-based control approach relies on matching a desired
force profile derived from object dimensions and weight and vision-based
monitoring of the object pose. The gripper controller uses tactile sensors to
detect and prevent translational slip by tightening the grip when needed.
Experimental results where the robot was tasked with rotating cuboid objects 90
degrees show that the multi-modal pivoting approach was able to rotate the
objects without causing lift or slip, and was more energy-efficient compared to
using a single sensor modality and to pick-and-place. While our work
demonstrated the benefit of multi-modal sensing for the pivoting task, further
work is needed to generalize our approach to any given object.Comment: 8 pages, 8 figures, 2 table
Intrinsic ferroelectric switching in two-dimension -InSe
Two-dimensional (2D) ferroelectric semiconductors present opportunities for
integrating ferroelectrics into high-density ultrathin nanoelectronics. Among
the few synthesized 2D ferroelectrics, -InSe, known for its
electrically addressable vertical polarization has attracted significant
interest. However, the understanding of many fundamental characteristics of
this material, such as the existence of spontaneous in-plane polarization and
switching mechanisms, remains controversial, marked by conflicting experimental
and theoretical results. Here, our combined experimental characterizations with
piezoresponse force microscope and symmetry analysis conclusively dismiss
previous claims of in-plane ferroelectricity in -InSe. The
processes of vertical polarization switching in monolayer -InSe
are explored with deep-learning-assisted large-scale molecular dynamics
simulations, revealing atomistic mechanisms fundamentally different from those
of bulk ferroelectrics. Despite lacking in-plane effective polarization, 1D
domain walls can be moved by both out-of-plane and in-plane fields, exhibiting
unusual avalanche dynamics characterized by abrupt, intermittent moving
patterns. The propagating velocity at various temperatures, field orientations,
and strengths can be statistically described with a universal creep equation,
featuring a dynamical exponent of 2 that is distinct from all known values for
elastic interfaces moving in disordered media. This work rectifies a long-held
misunderstanding regarding the in-plane ferroelectricity of
-InSe, and the quantitative characterizations of domain wall
velocity will hold broad implications for both the fundamental understanding
and technological applications of 2D ferroelectrics.Comment: 30 pages, 6 figure
Genetic insights into the gut microbiota, herpes zoster, and postherpetic neuralgia: a bidirectional two-sample Mendelian randomization study
BackgroundAn increasing amount of evidence suggests that gastrointestinal diseases are risk factors for herpes zoster (HZ) and postherpetic neuralgia (PHN). Among them, the gut microbiota may play a crucial role in this process. Therefore, this study aims to explore the potential causal association between the gut microbiota and HZ and PHN.MethodsBidirectional two-sample Mendelian randomization (MR) analysis was used to detect the causal effect between HZ and PHN and the gut microbiota. Gut microbiota data were derived from the MiBioGen consortium, while HZ and PHN data were obtained from the FinnGen database. We selected single-nucleotide polymorphisms (SNPs) as instrumental variables with a threshold of p < 1 × 10⁻⁵ for the association with the gut microbiota in forward MR analysis and p < 5 × 10⁻8 for the association with HZ or PHN in reverse MR analysis and then removed SNPs in linkage disequilibrium (r2 < 0.001) within a distance of 10,000 kb for both the gut microbiota and HZ and PHN. These SNPs were utilized to assess the causal effect between exposures and outcomes using inverse-variance weighting (IVW), MR–Egger, weighted mean, and weighted median tests.ResultsThe class Deltaproteobacteria, order Desulfovibrionales, family Desulfovibrionaceae, and genus Coprococcus 2 were found to reduce the risk of HZ, while the phylum Cyanobacteria, genus Eubacterium rectale group appeared to increase it. The class Coriobacteriia, order Coriobacteriales, family Coriobacteriaceae, genus Lachnospiraceae NK4A136 and genus Ruminococcaceae UCG011 were found to reduce the risk of PHN, while the genus Candidatus Soleaferrea, genus Eubacterium rectale group, and genus Methanobrevibacter appeared to increase it. Moreover, the onset of HZ was found to increase the level of the genus Eubacterium rectale group. These findings remained robust and unaffected by heterogeneity or horizontal pleiotropy among SNPs in both forward and reverse MR analysis.ConclusionThis MR study provided evidence supporting a potential causal relationship between the gut microbiota and HZ and PHN. Moreover, we found that the causal effect between the gut microbiota and HZ is bidirectional. Further studies are required to clarify the biological mechanisms linking the gut microbiota and these conditions
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