478 research outputs found
Modeling the Probabilistic Distribution of Unlabeled Data forOne-shot Medical Image Segmentation
Existing image segmentation networks mainly leverage large-scale labeled
datasets to attain high accuracy. However, labeling medical images is very
expensive since it requires sophisticated expert knowledge. Thus, it is more
desirable to employ only a few labeled data in pursuing high segmentation
performance. In this paper, we develop a data augmentation method for one-shot
brain magnetic resonance imaging (MRI) image segmentation which exploits only
one labeled MRI image (named atlas) and a few unlabeled images. In particular,
we propose to learn the probability distributions of deformations (including
shapes and intensities) of different unlabeled MRI images with respect to the
atlas via 3D variational autoencoders (VAEs). In this manner, our method is
able to exploit the learned distributions of image deformations to generate new
authentic brain MRI images, and the number of generated samples will be
sufficient to train a deep segmentation network. Furthermore, we introduce a
new standard segmentation benchmark to evaluate the generalization performance
of a segmentation network through a cross-dataset setting (collected from
different sources). Extensive experiments demonstrate that our method
outperforms the state-of-the-art one-shot medical segmentation methods. Our
code has been released at
https://github.com/dyh127/Modeling-the-Probabilistic-Distribution-of-Unlabeled-Data.Comment: AAAI 202
Wise-IoU: Bounding Box Regression Loss with Dynamic Focusing Mechanism
The loss function for bounding box regression (BBR) is essential to object
detection. Its good definition will bring significant performance improvement
to the model. Most existing works assume that the examples in the training data
are high-quality and focus on strengthening the fitting ability of BBR loss. If
we blindly strengthen BBR on low-quality examples, it will jeopardize
localization performance. Focal-EIoU v1 was proposed to solve this problem, but
due to its static focusing mechanism (FM), the potential of non-monotonic FM
was not fully exploited. Based on this idea, we propose an IoU-based loss with
a dynamic non-monotonic FM named Wise-IoU (WIoU). The dynamic non-monotonic FM
uses the outlier degree instead of IoU to evaluate the quality of anchor boxes
and provides a wise gradient gain allocation strategy. This strategy reduces
the competitiveness of high-quality anchor boxes while also reducing the
harmful gradient generated by low-quality examples. This allows WIoU to focus
on ordinary-quality anchor boxes and improve the detector's overall
performance. When WIoU is applied to the state-of-the-art real-time detector
YOLOv7, the AP-75 on the MS-COCO dataset is improved from 53.03% to 54.50%.
Code is available at https://github.com/Instinct323/wiou
Missing one-loop contributions in secondary gravitational waves
We find several missing one-loop-order contributions in previous
considerations about secondary gravitational waves induced at nonlinear order
in cosmological perturbations. We consider a consistent perturbative expansion
to third-order in cosmological perturbations, including higher-order
interactions and iterative solutions ignored in the previous literature. Tensor
fluctuations induced by the source with two scalar and one tensor perturbations
are correlated with the first-order tensor fluctuation and thus give a
one-loop-order correction to the tensor power spectrum. The missing loop
correction is \textit{scale-invariant} and \textit{negative} in the superhorion
region, which secondarily reduces the initial primordial tensor power spectrum
prior to the horizon re-entry. Such an IR behavior is very different from the
auto-spectrum of second-order induced tensor modes discussed in the previous
literature and can be important for the actual gravitational wave measurements.
For a sharp peak of scalar fluctuations with at
motivated by the LIGO/Virgo events, we show that the
tensor power spectrum at the cosmic microwave background scale reduces by at
most 35%. Hence, the polarization B-mode might not be seen because of the
reduction of the original tensor spectrum due to the secondary effect of
primordial black hole formation.Comment: 13 pages, 6 figure
Assessing Prompt Injection Risks in 200+ Custom GPTs
In the rapidly evolving landscape of artificial intelligence, ChatGPT has
been widely used in various applications. The new feature: customization of
ChatGPT models by users to cater to specific needs has opened new frontiers in
AI utility. However, this study reveals a significant security vulnerability
inherent in these user-customized GPTs: prompt injection attacks. Through
comprehensive testing of over 200 user-designed GPT models via adversarial
prompts, we demonstrate that these systems are susceptible to prompt
injections. Through prompt injection, an adversary can not only extract the
customized system prompts but also access the uploaded files. This paper
provides a first-hand analysis of the prompt injection, alongside the
evaluation of the possible mitigation of such attacks. Our findings underscore
the urgent need for robust security frameworks in the design and deployment of
customizable GPT models. The intent of this paper is to raise awareness and
prompt action in the AI community, ensuring that the benefits of GPT
customization do not come at the cost of compromised security and privacy
Policy Regularization with Dataset Constraint for Offline Reinforcement Learning
We consider the problem of learning the best possible policy from a fixed
dataset, known as offline Reinforcement Learning (RL). A common taxonomy of
existing offline RL works is policy regularization, which typically constrains
the learned policy by distribution or support of the behavior policy. However,
distribution and support constraints are overly conservative since they both
force the policy to choose similar actions as the behavior policy when
considering particular states. It will limit the learned policy's performance,
especially when the behavior policy is sub-optimal. In this paper, we find that
regularizing the policy towards the nearest state-action pair can be more
effective and thus propose Policy Regularization with Dataset Constraint
(PRDC). When updating the policy in a given state, PRDC searches the entire
dataset for the nearest state-action sample and then restricts the policy with
the action of this sample. Unlike previous works, PRDC can guide the policy
with proper behaviors from the dataset, allowing it to choose actions that do
not appear in the dataset along with the given state. It is a softer constraint
but still keeps enough conservatism from out-of-distribution actions. Empirical
evidence and theoretical analysis show that PRDC can alleviate offline RL's
fundamentally challenging value overestimation issue with a bounded performance
gap. Moreover, on a set of locomotion and navigation tasks, PRDC achieves
state-of-the-art performance compared with existing methods. Code is available
at https://github.com/LAMDA-RL/PRDCComment: Accepted to ICML 202
KPNet: Towards Minimal Face Detector
The small receptive field and capacity of minimal neural networks limit their
performance when using them to be the backbone of detectors. In this work, we
find that the appearance feature of a generic face is discriminative enough for
a tiny and shallow neural network to verify from the background. And the
essential barriers behind us are 1) the vague definition of the face bounding
box and 2) tricky design of anchor-boxes or receptive field. Unlike most
top-down methods for joint face detection and alignment, the proposed KPNet
detects small facial keypoints instead of the whole face by in a bottom-up
manner. It first predicts the facial landmarks from a low-resolution image via
the well-designed fine-grained scale approximation and scale adaptive
soft-argmax operator. Finally, the precise face bounding boxes, no matter how
we define it, can be inferred from the keypoints. Without any complex head
architecture or meticulous network designing, the KPNet achieves
state-of-the-art accuracy on generic face detection and alignment benchmarks
with only parameters, which runs at 1000fps on GPU and is easy to
perform real-time on most modern front-end chips.Comment: AAAI 202
Energy barrier at the N719-dye/CsSnI3 interface for photogenerated holes in dye-sensitized solar cells
This report is to address the question if black γ-polymorph of cesium tin tri-iodide (B-γ-CsSnI3) can be used as a solid-state hole-transport material in the conventional DSSCs with the N719 dye to replace the liquid electrolyte as reported by I. Chung et al. on Nature 485, 486, (2012). Here we demonstrate rigorously that B-γ-CsSnI3 is not energetically possible to collect photogenerated holes because of the large energy barrier at the interface of N719/B-γ-CsSnI3. Therefore, it cannot serve as a hole-transporter for the conventional DSSCs although it is a good hole-conducting material. A solution-based method was employed to synthesize the B-γ-CsSnI3 polycrystalline thin-films used for this work. These thin-films were then characterized by X-ray diffraction, Hall measurements, optical reflection, and photoluminescence (PL). Particularly, spatially resolved PL intensity images were taken after B-γ-CsSnI3 was incorporated in the DSSC structure to insure the material integrity. The means of ultraviolet photoemission spectroscopy (UPS) was used to reveal why B-γ-CsSnI3 could not act as the substitute of liquid electrolyte in the conventional DSSCs. For the completeness, other two related compounds, one is the yellow polymorph of CsSnI3 and other is Cs2SnI6 with tetravalent tin instead of double-valent tin in CsSnI3 were also investigated by UPS
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