269 research outputs found
Hartree-Fock-Bogoliubov Theory of Dipolar Fermi Gases
We construct a fully self-consistent Hartree-Fock-Bogoliubov theory that
describes a spinless Fermi gas with long-range interaction. We apply this
theory to a system of uniform dipolar fermionic polar molecules, which has
attracted much attention recently, due to rapid experimental progress in
achieving such systems. By calculating the anisotropic superfluid order
parameter, and the critical temperature , we show that, "hign "
superfluid can be achieved with a quite modest value of interaction strength
for polar molecules. In addition, we also show that the presence of the Fock
exchange interaction enhances superfluid pairing.Comment: 4.1 pages, 4 figure
Perspective: Ferromagnetic Liquids
Mechanical jamming of nanoparticles at liquid–liquid interfaces has evolved into a versatile approach to structure liquids with solid-state properties. Ferromagnetic liquids obtain their physical and magnetic properties, including a remanent magnetization that distinguishes them from ferrofluids, from the jamming of magnetic nanoparticles assembled at the interface between two distinct liquids to minimize surface tension. This perspective provides an overview of recent progress and discusses future directions, challenges and potential applications of jamming magnetic nanoparticles with regard to 3D nano-magnetism. We address the formation and characterization of curved magnetic geometries, and spin frustration between dipole-coupled nanostructures, and advance our understanding of particle jamming at liquid–liquid interfaces
Ab initio uncertainty quantification in scattering analysis of microscopy
Estimating parameters from data is a fundamental problem in physics,
customarily done by minimizing a loss function between a model and observed
statistics. In scattering-based analysis, researchers often employ their domain
expertise to select a specific range of wavevectors for analysis, a choice that
can vary depending on the specific case. We introduce another paradigm that
defines a probabilistic generative model from the beginning of data processing
and propagates the uncertainty for parameter estimation, termed ab initio
uncertainty quantification (AIUQ). As an illustrative example, we demonstrate
this approach with differential dynamic microscopy (DDM) that extracts
dynamical information through Fourier analysis at a selected range of
wavevectors. We first show that DDM is equivalent to fitting a temporal
variogram in the reciprocal space using a latent factor model as the generative
model. Then we derive the maximum marginal likelihood estimator, which
optimally weighs information at all wavevectors, therefore eliminating the need
to select the range of wavevectors. Furthermore, we substantially reduce the
computational cost by utilizing the generalized Schur algorithm for Toeplitz
covariances without approximation. Simulated studies validate that AIUQ
significantly improves estimation accuracy and enables model selection with
automated analysis. The utility of AIUQ is also demonstrated by three distinct
sets of experiments: first in an isotropic Newtonian fluid, pushing limits of
optically dense systems compared to multiple particle tracking; next in a
system undergoing a sol-gel transition, automating the determination of gelling
points and critical exponent; and lastly, in discerning anisotropic diffusive
behavior of colloids in a liquid crystal. These outcomes collectively
underscore AIUQ's versatility to capture system dynamics in an efficient and
automated manner
Ontology-aware Learning and Evaluation for Audio Tagging
This study defines a new evaluation metric for audio tagging tasks to
overcome the limitation of the conventional mean average precision (mAP)
metric, which treats different kinds of sound as independent classes without
considering their relations. Also, due to the ambiguities in sound labeling,
the labels in the training and evaluation set are not guaranteed to be accurate
and exhaustive, which poses challenges for robust evaluation with mAP. The
proposed metric, ontology-aware mean average precision (OmAP) addresses the
weaknesses of mAP by utilizing the AudioSet ontology information during the
evaluation. Specifically, we reweight the false positive events in the model
prediction based on the ontology graph distance to the target classes. The OmAP
measure also provides more insights into model performance by evaluations with
different coarse-grained levels in the ontology graph. We conduct human
evaluations and demonstrate that OmAP is more consistent with human perception
than mAP. To further verify the importance of utilizing the ontology
information, we also propose a novel loss function (OBCE) that reweights binary
cross entropy (BCE) loss based on the ontology distance. Our experiment shows
that OBCE can improve both mAP and OmAP metrics on the AudioSet tagging task.Comment: Submitted to ICASSP 2023. The code is open-sourced at
https://github.com/haoheliu/ontology-aware-audio-taggin
Perspective: Ferromagnetic liquids
Mechanical jamming of nanoparticles at liquid-liquid interfaces has evolved into a versatile approach to structure liquids with solid-state properties. Ferromagnetic liquids obtain their physical and magnetic properties, including a remanent magnetization that distinguishes them from ferrofluids, from the jamming of magnetic nanoparticles assembled at the interface between two distinct liquids to minimize surface tension. This perspective provides an overview of recent progress and discusses future directions, challenges and potential applications of jamming magnetic nanoparticles with regard to 3D nano-magnetism. We address the formation and characterization of curved magnetic geometries, and spin frustration between dipole-coupled nanostructures, and advance our understanding of particle jamming at liquid-liquid interfaces
Leveraging Pre-trained AudioLDM for Text to Sound Generation: A Benchmark Study
Deep neural networks have recently achieved breakthroughs in sound generation
with text prompts. Despite their promising performance, current text-to-sound
generation models face issues on small-scale datasets (e.g., overfitting),
significantly limiting their performance. In this paper, we investigate the use
of pre-trained AudioLDM, the state-of-the-art model for text-to-audio
generation, as the backbone for sound generation. Our study demonstrates the
advantages of using pre-trained models for text-to-sound generation, especially
in data-scarcity scenarios. In addition, experiments show that different
training strategies (e.g., training conditions) may affect the performance of
AudioLDM on datasets of different scales. To facilitate future studies, we also
evaluate various text-to-sound generation systems on several frequently used
datasets under the same evaluation protocols, which allow fair comparisons and
benchmarking of these methods on the common ground.Comment: EUSIPCO 202
Segment-level Metric Learning for Few-shot Bioacoustic Event Detection
Few-shot bioacoustic event detection is a task that detects the occurrence
time of a novel sound given a few examples. Previous methods employ metric
learning to build a latent space with the labeled part of different sound
classes, also known as positive events. In this study, we propose a
segment-level few-shot learning framework that utilizes both the positive and
negative events during model optimization. Training with negative events, which
are larger in volume than positive events, can increase the generalization
ability of the model. In addition, we use transductive inference on the
validation set during training for better adaptation to novel classes. We
conduct ablation studies on our proposed method with different setups on input
features, training data, and hyper-parameters. Our final system achieves an
F-measure of 62.73 on the DCASE 2022 challenge task 5 (DCASE2022-T5) validation
set, outperforming the performance of the baseline prototypical network 34.02
by a large margin. Using the proposed method, our submitted system ranks 2nd in
DCASE2022-T5. The code of this paper is fully open-sourced at
https://github.com/haoheliu/DCASE_2022_Task_5.Comment: 2nd place in the DCASE 2022 Challenge Task 5. Submitted to the DCASE
2022 worksho
Origin and tuning of the magnetocaloric effect for the magnetic refrigerant MnFe(P1-xGex)
Neutron diffraction and magnetization measurements of the magneto refrigerant
Mn1+yFe1-yP1-xGex reveal that the ferromagnetic and paramagnetic phases
correspond to two very distinct crystal structures, with the magnetic entropy
change as a function of magnetic field or temperature being directly controlled
by the phase fraction of this first-order transition. By tuning the physical
properties of this system we have achieved a maximum magnetic entropy change
exceeding 74 J/Kg K for both increasing and decreasing field, more than twice
the value of the previous record.Comment: 6 Figures. One tabl
Text-Driven Foley Sound Generation With Latent Diffusion Model
Foley sound generation aims to synthesise the background sound for multimedia
content. Previous models usually employ a large development set with labels as
input (e.g., single numbers or one-hot vector). In this work, we propose a
diffusion model based system for Foley sound generation with text conditions.
To alleviate the data scarcity issue, our model is initially pre-trained with
large-scale datasets and fine-tuned to this task via transfer learning using
the contrastive language-audio pertaining (CLAP) technique. We have observed
that the feature embedding extracted by the text encoder can significantly
affect the performance of the generation model. Hence, we introduce a trainable
layer after the encoder to improve the text embedding produced by the encoder.
In addition, we further refine the generated waveform by generating multiple
candidate audio clips simultaneously and selecting the best one, which is
determined in terms of the similarity score between the embedding of the
candidate clips and the embedding of the target text label. Using the proposed
method, our system ranks among the systems submitted to DCASE
Challenge 2023 Task 7. The results of the ablation studies illustrate that the
proposed techniques significantly improve sound generation performance. The
codes for implementing the proposed system are available online.Comment: Submit to DCASE-workshop 2023. arXiv admin note: text overlap with
arXiv:2305.1590
Adapting Language-Audio Models as Few-Shot Audio Learners
We presented the Treff adapter, a training-efficient adapter for CLAP, to
boost zero-shot classification performance by making use of a small set of
labelled data. Specifically, we designed CALM to retrieve the probability
distribution of text-audio clips over classes using a set of audio-label pairs
and combined it with CLAP's zero-shot classification results. Furthermore, we
designed a training-free version of the Treff adapter by using CALM as a cosine
similarity measure. Experiments showed that the proposed Treff adapter is
comparable and even better than fully-supervised methods and adaptation methods
in low-shot and data-abundant scenarios. While the Treff adapter shows that
combining large-scale pretraining and rapid learning of domain-specific
knowledge is non-trivial for obtaining generic representations for few-shot
learning, it is still limited to audio classification tasks. In the future, we
will explore how to use audio-language models in diverse audio domains
- …