168 research outputs found
Planar carbon nanotube-graphene hybrid films for high-performance broadband photodetectors
Graphene has emerged as a promising material for photonic applications
fuelled by its superior electronic and optical properties. However, the
photoresponsivity is limited by the low absorption cross section and ultrafast
recombination rates of photoexcited carriers. Here we demonstrate a
photoconductive gain of 10 electrons per photon in a carbon
nanotube-graphene one dimensional-two dimensional hybrid due to efficient
photocarriers generation and transport within the nanostructure. A broadband
photodetector (covering 400 nm to 1550 nm) based on such hybrid films is
fabricated with a high photoresponsivity of more than 100 AW and a fast
response time of approximately 100 {\mu}s. The combination of ultra-broad
bandwidth, high responsivities and fast operating speeds affords new
opportunities for facile and scalable fabrication of all-carbon optoelectronic
devices.Comment: 21 pages, 3 figure
PhantomSound: Black-Box, Query-Efficient Audio Adversarial Attack via Split-Second Phoneme Injection
In this paper, we propose PhantomSound, a query-efficient black-box attack
toward voice assistants. Existing black-box adversarial attacks on voice
assistants either apply substitution models or leverage the intermediate model
output to estimate the gradients for crafting adversarial audio samples.
However, these attack approaches require a significant amount of queries with a
lengthy training stage. PhantomSound leverages the decision-based attack to
produce effective adversarial audios, and reduces the number of queries by
optimizing the gradient estimation. In the experiments, we perform our attack
against 4 different speech-to-text APIs under 3 real-world scenarios to
demonstrate the real-time attack impact. The results show that PhantomSound is
practical and robust in attacking 5 popular commercial voice controllable
devices over the air, and is able to bypass 3 liveness detection mechanisms
with >95% success rate. The benchmark result shows that PhantomSound can
generate adversarial examples and launch the attack in a few minutes. We
significantly enhance the query efficiency and reduce the cost of a successful
untargeted and targeted adversarial attack by 93.1% and 65.5% compared with the
state-of-the-art black-box attacks, using merely ~300 queries (~5 minutes) and
~1,500 queries (~25 minutes), respectively.Comment: RAID 202
Beyond Boundaries: A Comprehensive Survey of Transferable Attacks on AI Systems
Artificial Intelligence (AI) systems such as autonomous vehicles, facial
recognition, and speech recognition systems are increasingly integrated into
our daily lives. However, despite their utility, these AI systems are
vulnerable to a wide range of attacks such as adversarial, backdoor, data
poisoning, membership inference, model inversion, and model stealing attacks.
In particular, numerous attacks are designed to target a particular model or
system, yet their effects can spread to additional targets, referred to as
transferable attacks. Although considerable efforts have been directed toward
developing transferable attacks, a holistic understanding of the advancements
in transferable attacks remains elusive. In this paper, we comprehensively
explore learning-based attacks from the perspective of transferability,
particularly within the context of cyber-physical security. We delve into
different domains -- the image, text, graph, audio, and video domains -- to
highlight the ubiquitous and pervasive nature of transferable attacks. This
paper categorizes and reviews the architecture of existing attacks from various
viewpoints: data, process, model, and system. We further examine the
implications of transferable attacks in practical scenarios such as autonomous
driving, speech recognition, and large language models (LLMs). Additionally, we
outline the potential research directions to encourage efforts in exploring the
landscape of transferable attacks. This survey offers a holistic understanding
of the prevailing transferable attacks and their impacts across different
domains
High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit
Graphene and other two-dimensional (2D) materials have emerged as promising
materials for broadband and ultrafast photodetection and optical modulation.
These optoelectronic capabilities can augment complementary
metal-oxide-semiconductor (CMOS) devices for high-speed and low-power optical
interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on
a two-dimensional heterostructure consisting of high-quality graphene
encapsulated in hexagonal boron nitride. Coupled to the optical mode of a
silicon waveguide, this 2D heterostructure-based photodetector exhibits a
maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cut-off
at 42 GHz. From photocurrent measurements as a function of the top-gate and
source-drain voltages, we conclude that the photoresponse is consistent with
hot electron mediated effects. At moderate peak powers above 50 mW, we observe
a saturating photocurrent consistent with the mechanisms of electron-phonon
supercollision cooling. This nonlinear photoresponse enables optical on-chip
autocorrelation measurements with picosecond-scale timing resolution and
exceptionally low peak powers
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Deformation induced structural evolution in bulk metallic glasses
The structural behavior of binary Cu50Zr50 and ternary Cu50Zr45Ti5 bulk metallic glasses (BMGs) under applied stress was investigated by means of in-situ high energy X-ray synchrotron diffraction. The components of the strain tensors were determined from the shifts of the maxima of the atomic pair correlation functions (PDF) in real space. The anisotropic atomic reorientation in the first-nearest-neighbor shell versus stress suggests structural rearrangements in short-range order. Within the plastic deformation range the overall strain of the metallic glass is equal to the yield strain. After unloading, the atomic structure returns to the stress-free state, and the short-range order is identical to that of the undeformed state. Plastic deformation, however, leads to localized shear bands whose contribution to the volume averaged diffraction pattern is too weak to be detected. A concordant region evidenced by the anisotropic component is activated to counterbalance the stress change due to the atomic bond reorientation in the first-nearest-neighbor shell. The size of the concordant region is an important factor dominating the yield strength and the plastic strain ability of the BMGs
Deformation induced structural evolution in bulk metallic glasses
The structural behavior of binary Cu50Zr50 and ternary Cu50Zr45Ti5 bulk metallic glasses (BMGs) under applied stress was investigated by means of in-situ high energy X-ray synchrotron diffraction. The components of the strain tensors were determined from the shifts of the maxima of the atomic pair correlation functions (PDF) in real space. The anisotropic atomic reorientation in the first-nearest-neighbor shell versus stress suggests structural rearrangements in short-range order. Within the plastic deformation range the overall strain of the metallic glass is equal to the yield strain. After unloading, the atomic structure returns to the stress-free state, and the short-range order is identical to that of the undeformed state. Plastic deformation, however, leads to localized shear bands whose contribution to the volume averaged diffraction pattern is too weak to be detected. A concordant region evidenced by the anisotropic component is activated to counterbalance the stress change due to the atomic bond reorientation in the first-nearest-neighbor shell. The size of the concordant region is an important factor dominating the yield strength and the plastic strain ability of the BMGs
Advancements in 3D Lane Detection Using LiDAR Point Clouds: From Data Collection to Model Development
Advanced Driver-Assistance Systems (ADAS) have successfully integrated
learning-based techniques into vehicle perception and decision-making. However,
their application in 3D lane detection for effective driving environment
perception is hindered by the lack of comprehensive LiDAR datasets. The sparse
nature of LiDAR point cloud data prevents an efficient manual annotation
process. To solve this problem, we present LiSV-3DLane, a large-scale 3D lane
dataset that comprises 20k frames of surround-view LiDAR point clouds with
enriched semantic annotation. Unlike existing datasets confined to a frontal
perspective, LiSV-3DLane provides a full 360-degree spatial panorama around the
ego vehicle, capturing complex lane patterns in both urban and highway
environments. We leverage the geometric traits of lane lines and the intrinsic
spatial attributes of LiDAR data to design a simple yet effective automatic
annotation pipeline for generating finer lane labels. To propel future
research, we propose a novel LiDAR-based 3D lane detection model, LiLaDet,
incorporating the spatial geometry learning of the LiDAR point cloud into
Bird's Eye View (BEV) based lane identification. Experimental results indicate
that LiLaDet outperforms existing camera- and LiDAR-based approaches in the 3D
lane detection task on the K-Lane dataset and our LiSV-3DLane.Comment: 7 pages, 6 figure
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