9 research outputs found
PIAT: Physics Informed Adversarial Training for Solving Partial Differential Equations
In this paper, we propose the physics informed adversarial training (PIAT) of
neural networks for solving nonlinear differential equations (NDE). It is
well-known that the standard training of neural networks results in non-smooth
functions. Adversarial training (AT) is an established defense mechanism
against adversarial attacks, which could also help in making the solution
smooth. AT include augmenting the training mini-batch with a perturbation that
makes the network output mismatch the desired output adversarially. Unlike
formal AT, which relies only on the training data, here we encode the governing
physical laws in the form of nonlinear differential equations using automatic
differentiation in the adversarial network architecture. We compare PIAT with
PINN to indicate the effectiveness of our method in solving NDEs for up to 10
dimensions. Moreover, we propose weight decay and Gaussian smoothing to
demonstrate the PIAT advantages. The code repository is available at
https://github.com/rohban-lab/PIAT
Unmasking the Chameleons: A Benchmark for Out-of-Distribution Detection in Medical Tabular Data
Despite their success, Machine Learning (ML) models do not generalize
effectively to data not originating from the training distribution. To reliably
employ ML models in real-world healthcare systems and avoid inaccurate
predictions on out-of-distribution (OOD) data, it is crucial to detect OOD
samples. Numerous OOD detection approaches have been suggested in other fields
- especially in computer vision - but it remains unclear whether the challenge
is resolved when dealing with medical tabular data. To answer this pressing
need, we propose an extensive reproducible benchmark to compare different
methods across a suite of tests including both near and far OODs. Our benchmark
leverages the latest versions of eICU and MIMIC-IV, two public datasets
encompassing tens of thousands of ICU patients in several hospitals. We
consider a wide array of density-based methods and SOTA post-hoc detectors
across diverse predictive architectures, including MLP, ResNet, and
Transformer. Our findings show that i) the problem appears to be solved for
far-OODs, but remains open for near-OODs; ii) post-hoc methods alone perform
poorly, but improve substantially when coupled with distance-based mechanisms;
iii) the transformer architecture is far less overconfident compared to MLP and
ResNet
The impact of guided inquiry methods of teaching on the critical thinking of high school students
The objective pursued by the present study is to investigate the impact of guided inquiry and traditional methods of teaching on the critical thinking skills among second grade high school students. Given the purpose, a total of 190 second grade high school students were chosen through random, multi-step and cluster sampling methods in the form of 8 classes and placed into 8 experimental and control groups. A pre-test post-test design was administered to the control group. The demographic information was collected by a researcher –made questionnaire and the thinking skills information was determined by Watson - Glaser test. Two- factor covariance method was used for data analysis. Results showed that the guided inquiry method of teaching had significant impact (lower than 0.05) on the critical thinking skills of students in inference and conclusion subscales. The impact of gender factor on the students’ critical thinking was significant, in terms of conclusion and interpretation subscales as well. The impact of interaction between gender and teaching method was also significant in inference and interpretation subscales. Keywords: critical thinking, guided inquiry teaching method, traditional teaching method
Your Out-of-Distribution Detection Method is Not Robust!
Out-of-distribution (OOD) detection has recently gained substantial attention
due to the importance of identifying out-of-domain samples in reliability and
safety. Although OOD detection methods have advanced by a great deal, they are
still susceptible to adversarial examples, which is a violation of their
purpose. To mitigate this issue, several defenses have recently been proposed.
Nevertheless, these efforts remained ineffective, as their evaluations are
based on either small perturbation sizes, or weak attacks. In this work, we
re-examine these defenses against an end-to-end PGD attack on in/out data with
larger perturbation sizes, e.g. up to commonly used for the
CIFAR-10 dataset. Surprisingly, almost all of these defenses perform worse than
a random detection under the adversarial setting. Next, we aim to provide a
robust OOD detection method. In an ideal defense, the training should expose
the model to almost all possible adversarial perturbations, which can be
achieved through adversarial training. That is, such training perturbations
should based on both in- and out-of-distribution samples. Therefore, unlike OOD
detection in the standard setting, access to OOD, as well as in-distribution,
samples sounds necessary in the adversarial training setup. These tips lead us
to adopt generative OOD detection methods, such as OpenGAN, as a baseline. We
subsequently propose the Adversarially Trained Discriminator (ATD), which
utilizes a pre-trained robust model to extract robust features, and a generator
model to create OOD samples. Using ATD with CIFAR-10 and CIFAR-100 as the
in-distribution data, we could significantly outperform all previous methods in
the robust AUROC while maintaining high standard AUROC and classification
accuracy. The code repository is available at https://github.com/rohban-lab/ATD .Comment: Accepted to NeurIPS 202
Blacksmith: Fast Adversarial Training of Vision Transformers via a Mixture of Single-step and Multi-step Methods
Despite the remarkable success achieved by deep learning algorithms in
various domains, such as computer vision, they remain vulnerable to adversarial
perturbations. Adversarial Training (AT) stands out as one of the most
effective solutions to address this issue; however, single-step AT can lead to
Catastrophic Overfitting (CO). This scenario occurs when the adversarially
trained network suddenly loses robustness against multi-step attacks like
Projected Gradient Descent (PGD). Although several approaches have been
proposed to address this problem in Convolutional Neural Networks (CNNs), we
found out that they do not perform well when applied to Vision Transformers
(ViTs). In this paper, we propose Blacksmith, a novel training strategy to
overcome the CO problem, specifically in ViTs. Our approach utilizes either of
PGD-2 or Fast Gradient Sign Method (FGSM) randomly in a mini-batch during the
adversarial training of the neural network. This will increase the diversity of
our training attacks, which could potentially mitigate the CO issue. To manage
the increased training time resulting from this combination, we craft the PGD-2
attack based on only the first half of the layers, while FGSM is applied
end-to-end. Through our experiments, we demonstrate that our novel method
effectively prevents CO, achieves PGD-2 level performance, and outperforms
other existing techniques including N-FGSM, which is the state-of-the-art
method in fast training for CNNs
The development of critical thinking skills in physics and sociology curricula
The present study aims to compare the impact of guided inquiry and traditional teaching methods on critical thinking skills of second-grade high school students in physics and sociology courses. Given the purpose, a total of 190 second grade high school students were chosen through random, multi-step and cluster sampling methods in the form of 8 classes and placed into 8 experimental and control groups in physics and sociology courses. A pre-test post-test design was administered to the control group. In order to collect information about participants, two tools were employed. The demographic information was collected by a researcher-made questionnaire and the thinking skills information was determined by Watson - Glaser test. Two- factor covariance method was utilized for data analysis. Results showed that the impact of guided inquiry teaching method on the critical thinking skills of students in inference and conclusion subscales, and the effect of subject in conclusion and interpretation subscales was significan
Dynamic wetting properties of PDMS pseudo-brushes: Four-phase contact point dynamics case
We investigate the wetting properties of PDMS (Polydimethylsiloxane) pseudo-brush anchored on glass substrates. These PDMS pseudo-brushes exhibit a significantly lower contact angle hysteresis compared to hydrophobic silanized substrates. The effect of different molar masses of the used PDMS on the wetting properties seems negligible. The surface roughness and thickness of the PDMS pseudo-brush are measured by atomic force microscopy and x-ray reflectivity. The outcome shows that these surfaces are extremely smooth (topologically and chemically), which explains the reduction in contact angle hysteresis. These special features make this kind of surfaces very useful for wetting experiments. Here, the dynamics of the four-phase contact point are studied on these surfaces. The four-phase contact point dynamics on PDMS pseudo-brushes deviate substantially from its dynamics on other substrates. These changes depend only a little on the molar mass of the used PDMS. In general, PDMS pseudo-brushes increase the traveling speed of four-phase contact point on the surface and change the associated power law of position vs time
Dynamic wetting properties of PDMS pseudo-brushes: Four-phase contact point dynamics case
We investigate the wetting properties of PDMS (Polydimethylsiloxane) pseudo-brush anchored on glass substrates. These PDMS pseudobrushes exhibit a significantly lower contact angle hysteresis compared to hydrophobic silanized substrates. The effect of different molar masses of the used PDMS on the wetting properties seems negligible. The surface roughness and thickness of the PDMS pseudo-brush are measured by atomic force microscopy and x-ray reflectivity. The outcome shows that these surfaces are extremely smooth (topologically and chemically), which explains the reduction in contact angle hysteresis. These special features make this kind of surfaces very useful for wetting experiments. Here, the dynamics of the four-phase contact point are studied on these surfaces. The four-phase contact point dynamics on PDMS pseudo-brushes deviate substantially from its dynamics on other substrates. These changes depend only a little on the molar mass of the used PDMS. In general, PDMS pseudo-brushes increase the traveling speed of four-phase contact point on the surface and change the associated power law of position vs time