70 research outputs found
FMT: Removing Backdoor Feature Maps via Feature Map Testing in Deep Neural Networks
Deep neural networks have been widely used in many critical applications,
such as autonomous vehicles and medical diagnosis. However, their security is
threatened by backdoor attack, which is achieved by adding artificial patterns
to specific training data. Existing defense strategies primarily focus on using
reverse engineering to reproduce the backdoor trigger generated by attackers
and subsequently repair the DNN model by adding the trigger into inputs and
fine-tuning the model with ground-truth labels. However, once the trigger
generated by the attackers is complex and invisible, the defender can not
successfully reproduce the trigger. Consequently, the DNN model will not be
repaired since the trigger is not effectively removed.
In this work, we propose Feature Map Testing~(FMT). Different from existing
defense strategies, which focus on reproducing backdoor triggers, FMT tries to
detect the backdoor feature maps, which are trained to extract backdoor
information from the inputs. After detecting these backdoor feature maps, FMT
will erase them and then fine-tune the model with a secure subset of training
data. Our experiments demonstrate that, compared to existing defense
strategies, FMT can effectively reduce the Attack Success Rate (ASR) even
against the most complex and invisible attack triggers. Second, unlike
conventional defense methods that tend to exhibit low Robust Accuracy (i.e.,
the model's accuracy on the poisoned data), FMT achieves higher RA, indicating
its superiority in maintaining model performance while mitigating the effects
of backdoor attacks~(e.g., FMT obtains 87.40\% RA in CIFAR10). Third, compared
to existing feature map pruning techniques, FMT can cover more backdoor feature
maps~(e.g., FMT removes 83.33\% of backdoor feature maps from the model in the
CIFAR10 \& BadNet scenario).Comment: 12 pages, 4 figure
Feature Map Testing for Deep Neural Networks
Due to the widespread application of deep neural networks~(DNNs) in
safety-critical tasks, deep learning testing has drawn increasing attention.
During the testing process, test cases that have been fuzzed or selected using
test metrics are fed into the model to find fault-inducing test units (e.g.,
neurons and feature maps, activating which will almost certainly result in a
model error) and report them to the DNN developer, who subsequently repair
them~(e.g., retraining the model with test cases). Current test metrics,
however, are primarily concerned with the neurons, which means that test cases
that are discovered either by guided fuzzing or selection with these metrics
focus on detecting fault-inducing neurons while failing to detect
fault-inducing feature maps.
In this work, we propose DeepFeature, which tests DNNs from the feature map
level. When testing is conducted, DeepFeature will scrutinize every internal
feature map in the model and identify vulnerabilities that can be enhanced
through repairing to increase the model's overall performance. Exhaustive
experiments are conducted to demonstrate that (1) DeepFeature is a strong tool
for detecting the model's vulnerable feature maps; (2) DeepFeature's test case
selection has a high fault detection rate and can detect more types of
faults~(comparing DeepFeature to coverage-guided selection techniques, the
fault detection rate is increased by 49.32\%). (3) DeepFeature's fuzzer also
outperforms current fuzzing techniques and generates valuable test cases more
efficiently.Comment: 12 pages, 5 figures. arXiv admin note: text overlap with
arXiv:2307.1101
Neuron Sensitivity Guided Test Case Selection for Deep Learning Testing
Deep Neural Networks~(DNNs) have been widely deployed in software to address
various tasks~(e.g., autonomous driving, medical diagnosis). However, they
could also produce incorrect behaviors that result in financial losses and even
threaten human safety. To reveal the incorrect behaviors in DNN and repair
them, DNN developers often collect rich unlabeled datasets from the natural
world and label them to test the DNN models. However, properly labeling a large
number of unlabeled datasets is a highly expensive and time-consuming task.
To address the above-mentioned problem, we propose NSS, Neuron Sensitivity
guided test case Selection, which can reduce the labeling time by selecting
valuable test cases from unlabeled datasets. NSS leverages the internal
neuron's information induced by test cases to select valuable test cases, which
have high confidence in causing the model to behave incorrectly. We evaluate
NSS with four widely used datasets and four well-designed DNN models compared
to SOTA baseline methods. The results show that NSS performs well in assessing
the test cases' probability of fault triggering and model improvement
capabilities. Specifically, compared with baseline approaches, NSS obtains a
higher fault detection rate~(e.g., when selecting 5\% test case from the
unlabeled dataset in MNIST \& LeNet1 experiment, NSS can obtain 81.8\% fault
detection rate, 20\% higher than baselines)
Correlations in Horizontal Branch Oscillations and Break Components in XTE J1701-462 and GX 17+2
We studied the horizontal branch oscillations (HBO) and the band-limited
components observed in the power spectra of the transient neutron star low-mass
X-ray binary XTE J1701-462 and the persistent "Sco-like" Z source GX 17+2.
These two components were studied based on the state-resolved spectra. We found
that the frequencies of XTE J1701-462 lie on the known correlations (WK and
PBK), showing consistency with other types of X-ray binaries (black holes,
atoll sources and millisecond X-ray pulsars). However, GX 17+2 is shifted from
the WK correlation like other typical Z sources. We suggest that the WK/PBK
main track forms a boundary which separates persistent sources from transient
sources. The characteristic frequencies of break and HBO are independent of
accretion rate in both sources, although it depends on spectral models. We also
report the energy dependence of the HBO and break frequencies in XTE J1701-462
and how the temporal properties change with spectral state in XTE J1701-462 and
GX 17+2. We studied the correlation between rms at the break and the HBO
frequency. We suggest that HBO and break components for both sources probably
arise from a similar physical mechanism: Comptonization emission from the
corona. These two components could be caused by same kind of oscillation in a
corona who with uneven density, and they could be generated from different
areas of corona. We further suggest that different proportions of the
Comptonization component in the total flux cause the different distribution
between GX 17+2 and XTE J1701-462 in the -
diagram.Comment: 36 pages, 7 figures, accpeted by Ap
Hilbert-Huang Transform analysis of quasi-periodic oscillations in MAXI J1820+070
We present time-frequency analysis, based on the Hilbert-Huang transform
(HHT), of the evolution on the low-frequency quasi-periodic oscillations
(LFQPOs) observed in the black hole X-ray binary MAXI J1820+070. Through the
empirical mode decomposition (EMD) method, we decompose the light curve of the
QPO component and measure its intrinsic phase lag between photons from
different energy bands. We find that the QPO phase lag is negative (low energy
photons lag behind high energy photons), meanwhile the absolute value of the
lag increases with energy. By applying the Hilbert transform to the light curve
of the QPO, we further extract the instantaneous frequency and amplitude of the
QPO. Compared these results with those from the Fourier analysis, we find that
the broadening of the QPO peak is mainly caused by the frequency modulation.
Through further analysis, we find that these modulations could share a common
physical origin with the broad-band noise, and can be well explained by the
internal shock model of the jet
An Updated Search of Steady TeV Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array
Using the data taken from Tibet II High Density (HD) Array (1997
February-1999 September) and Tibet-III array (1999 November-2005 November), our
previous northern sky survey for TeV ray point sources has now been
updated by a factor of 2.8 improved statistics. From to
in declination (Dec) range, no new TeV ray point
sources with sufficiently high significance were identified while the
well-known Crab Nebula and Mrk421 remain to be the brightest TeV ray
sources within the field of view of the Tibet air shower array. Based on the
currently available data and at the 90% confidence level (C.L.), the flux upper
limits for different power law index assumption are re-derived, which are
approximately improved by 1.7 times as compared with our previous reported
limits.Comment: This paper has been accepted by hepn
Proton-Boron Fusion Yield Increased by Orders of Magnitude with Foam Targets
A novel intense beam-driven scheme for high yield of the tri-alpha reaction
11B(p,{\alpha})2{\alpha} was investigated. We used a foam target made of
cellulose triacetate (TAC, C_9H_{16}O_8) doped with boron. It was then heated
volumetrically by soft X-ray radiation from a laser heated hohlraum and turned
into a homogenous, and long living plasma. We employed a picosecond laser pulse
to generate a high-intensity energetic proton beam via the well-known Target
Normal Sheath Acceleration (TNSA) mechanism. We observed up to 10^{10}/sr
{\alpha} particles per laser shot. This constitutes presently the highest yield
value normalized to the laser energy on target. The measured fusion yield per
proton exceeds the classical expectation of beam-target reactions by up to four
orders of magnitude under high proton intensities. This enhancement is
attributed to the strong electric fields and nonequilibrium thermonuclear
fusion reactions as a result of the new method. Our approach shows
opportunities to pursue ignition of aneutronic fusion
The accretion flow geometry of MAXI J1820+070 through broadband noise research with Insight-HXMT
Here we present a detailed study of the broadband noise in the power density
spectra of the black hole X-ray binary MAXI J1820+070 during the hard state of
its 2018 outburst, using the Hard X-ray Modulation Telescope (Insight-HXMT)
observations. The broadband noise shows two main humps, which might separately
correspond to variability from a variable disk and two Comptonization regions.
We fitted the two humps with multiple Lorentzian functions and studied the
energy-dependent properties of each component up to 100--150 keV and their
evolution with spectral changes. The lowest frequency component is considered
as the sub-harmonic of QPO component and shows different energy dependence
compared with other broadband noise components. We found that although the
fractional rms of all the broadband noise components mainly decrease with
energy, their rms spectra are different in shape. Above 20--30 keV, the
characteristic frequencies of these components increase sharply with energy,
meaning that the high-energy component is more variable on short timescales.
Our results suggest that the hot inner flow in MAXI J1820+070 is likely to be
inhomogeneous. We propose a geometry with a truncated accretion disk, two
Comptonization regions
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