195 research outputs found
Sequential Subset Matching for Dataset Distillation
Dataset distillation is a newly emerging task that synthesizes a small-size
dataset used in training deep neural networks (DNNs) for reducing data storage
and model training costs. The synthetic datasets are expected to capture the
essence of the knowledge contained in real-world datasets such that the former
yields a similar performance as the latter. Recent advancements in distillation
methods have produced notable improvements in generating synthetic datasets.
However, current state-of-the-art methods treat the entire synthetic dataset as
a unified entity and optimize each synthetic instance equally. This static
optimization approach may lead to performance degradation in dataset
distillation. Specifically, we argue that static optimization can give rise to
a coupling issue within the synthetic data, particularly when a larger amount
of synthetic data is being optimized. This coupling issue, in turn, leads to
the failure of the distilled dataset to extract the high-level features learned
by the deep neural network (DNN) in the latter epochs.
In this study, we propose a new dataset distillation strategy called
Sequential Subset Matching (SeqMatch), which tackles this problem by adaptively
optimizing the synthetic data to encourage sequential acquisition of knowledge
during dataset distillation. Our analysis indicates that SeqMatch effectively
addresses the coupling issue by sequentially generating the synthetic
instances, thereby enhancing its performance significantly. Our proposed
SeqMatch outperforms state-of-the-art methods in various datasets, including
SVNH, CIFAR-10, CIFAR-100, and Tiny ImageNet. Our code is available at
https://github.com/shqii1j/seqmatch
Magnetic control of the valley degree of freedom of massive Dirac fermions with application to transition metal dichalcogenides
We study the valley-dependent magnetic and transport properties of massive
Dirac fermions in multivalley systems such as the transition metal
dichalcogenides. The asymmetry of the zeroth Landau level between valleys and
the enhanced magnetic susceptibility can be attributed to the different orbital
magnetic moment tied with each valley. This allows the valley polarization to
be controlled by tuning the external magnetic field and the doping level. As a
result of this magnetic field induced valley polarization, there exists an
extra contribution to the ordinary Hall effect. All these effects can be
captured by a low energy effective theory with a valley-orbit coupling term.Comment: 9 pages, 6 figure
FreeCOS: Self-Supervised Learning from Fractals and Unlabeled Images for Curvilinear Object Segmentation
Curvilinear object segmentation is critical for many applications. However,
manually annotating curvilinear objects is very time-consuming and error-prone,
yielding insufficiently available annotated datasets for existing supervised
methods and domain adaptation methods. This paper proposes a self-supervised
curvilinear object segmentation method that learns robust and distinctive
features from fractals and unlabeled images (FreeCOS). The key contributions
include a novel Fractal-FDA synthesis (FFS) module and a geometric information
alignment (GIA) approach. FFS generates curvilinear structures based on the
parametric Fractal L-system and integrates the generated structures into
unlabeled images to obtain synthetic training images via Fourier Domain
Adaptation. GIA reduces the intensity differences between the synthetic and
unlabeled images by comparing the intensity order of a given pixel to the
values of its nearby neighbors. Such image alignment can explicitly remove the
dependency on absolute intensity values and enhance the inherent geometric
characteristics which are common in both synthetic and real images. In
addition, GIA aligns features of synthetic and real images via the prediction
space adaptation loss (PSAL) and the curvilinear mask contrastive loss (CMCL).
Extensive experimental results on four public datasets, i.e., XCAD, DRIVE,
STARE and CrackTree demonstrate that our method outperforms the
state-of-the-art unsupervised methods, self-supervised methods and traditional
methods by a large margin. The source code of this work is available at
https://github.com/TY-Shi/FreeCOS.Comment: Accepted by ICCV 202
Learning Green's functions associated with time-dependent partial differential equations
Neural operators are a popular technique in scientific machine learning to
learn a mathematical model of the behavior of unknown physical systems from
data. Neural operators are especially useful to learn solution operators
associated with partial differential equations (PDEs) from pairs of forcing
functions and solutions when numerical solvers are not available or the
underlying physics is poorly understood. In this work, we attempt to provide
theoretical foundations to understand the amount of training data needed to
learn time-dependent PDEs. Given input-output pairs from a parabolic PDE in any
spatial dimension , we derive the first theoretically rigorous scheme
for learning the associated solution operator, which takes the form of a
convolution with a Green's function . Until now, rigorously learning Green's
functions associated with time-dependent PDEs has been a major challenge in the
field of scientific machine learning because may not be square-integrable
when , and time-dependent PDEs have transient dynamics. By combining the
hierarchical low-rank structure of together with randomized numerical
linear algebra, we construct an approximant to that achieves a relative
error of in the
-norm with high probability by using at most
input-output
training pairs, where is a measure of the quality of the
training dataset for learning , and is sufficiently small.Comment: 34 pages, 3 figure
Continual Task Allocation in Meta-Policy Network via Sparse Prompting
How to train a generalizable meta-policy by continually learning a sequence
of tasks? It is a natural human skill yet challenging to achieve by current
reinforcement learning: the agent is expected to quickly adapt to new tasks
(plasticity) meanwhile retaining the common knowledge from previous tasks
(stability). We address it by "Continual Task Allocation via Sparse Prompting
(CoTASP)", which learns over-complete dictionaries to produce sparse masks as
prompts extracting a sub-network for each task from a meta-policy network. By
optimizing the sub-network and prompts alternatively, CoTASP updates the
meta-policy via training a task-specific policy. The dictionary is then updated
to align the optimized prompts with tasks' embedding, thereby capturing their
semantic correlations. Hence, relevant tasks share more neurons in the
meta-policy network via similar prompts while cross-task interference causing
forgetting is effectively restrained. Given a trained meta-policy with updated
dictionaries, new task adaptation reduces to highly efficient sparse prompting
and sub-network finetuning. In experiments, CoTASP achieves a promising
plasticity-stability trade-off without storing or replaying any past tasks'
experiences and outperforms existing continual and multi-task RL methods on all
seen tasks, forgetting reduction, and generalization to unseen tasks.Comment: Accepted by ICML 202
Magnetoelectric Coupling and Electric Control of Magnetization in Ferromagnet-Ferroelectric-Metal Superlattices
Ferromagnet-ferroelectric-metal superlattices are proposed to realize the
large room-temperature magnetoelectric effect. Spin dependent electron
screening is the fundamental mechanism at the microscopic level. We also
predict an electric control of magnetization in this structure. The naturally
broken inversion symmetry in our tri-component structure introduces a
magnetoelectric coupling energy of . Such a magnetoelectric coupling
effect is general in ferromagnet-ferroelectric heterostructures, independent of
particular chemical or physical bonding, and will play an important role in the
field of multiferroics.Comment: 5 pages including 3 figures and 1 tabl
Performance of an omnidirectional piezoelectric wind energy harvester
This paper presents a vortex-induced vibration (VIV)-based piezoelectric energy harvester that performs well for all wind directions, a so-called omnidirectional wind energy harvester. The kinetic energy of this harvester stems from wind-induced vibrations of a circular cylinder mounted on an orthogonal bibeam system, rather than a traditional single beam. Wind tunnel testing results show that compared to the traditional single-beam energy harvester, the proposed harvester substantially enhances the effectiveness, in most cases that the beam is skew to the incoming flow. The reasons for the enhancement are explained in detail by examining the wind-induced displacement response components of the cylinder identified by the image processing technique. For all wind directions, both the maximal output energy and the range of effectively working wind speed of the proposed bibeam wind energy harvester are significantly improved with respect to the single-beam system, indicating excellent performance of the proposed omnidirectional harvester in a natural wind environment
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