30 research outputs found
Faster Sampling without Isoperimetry via Diffusion-based Monte Carlo
To sample from a general target distribution beyond the
isoperimetric condition, Huang et al. (2023) proposed to perform sampling
through reverse diffusion, giving rise to Diffusion-based Monte Carlo (DMC).
Specifically, DMC follows the reverse SDE of a diffusion process that
transforms the target distribution to the standard Gaussian, utilizing a
non-parametric score estimation. However, the original DMC algorithm
encountered high gradient complexity, resulting in an exponential dependency on
the error tolerance of the obtained samples. In this paper, we
demonstrate that the high complexity of DMC originates from its redundant
design of score estimation, and proposed a more efficient algorithm, called
RS-DMC, based on a novel recursive score estimation method. In particular, we
first divide the entire diffusion process into multiple segments and then
formulate the score estimation step (at any time step) as a series of
interconnected mean estimation and sampling subproblems accordingly, which are
correlated in a recursive manner. Importantly, we show that with a proper
design of the segment decomposition, all sampling subproblems will only need to
tackle a strongly log-concave distribution, which can be very efficient to
solve using the Langevin-based samplers with a provably rapid convergence rate.
As a result, we prove that the gradient complexity of RS-DMC only has a
quasi-polynomial dependency on , which significantly improves
exponential gradient complexity in Huang et al. (2023). Furthermore, under
commonly used dissipative conditions, our algorithm is provably much faster
than the popular Langevin-based algorithms. Our algorithm design and
theoretical framework illuminate a novel direction for addressing sampling
problems, which could be of broader applicability in the community.Comment: 54 page
Mixup-Augmented Meta-Learning for Sample-Efficient Fine-Tuning of Protein Simulators
Molecular dynamics simulations have emerged as a fundamental instrument for
studying biomolecules. At the same time, it is desirable to perform simulations
of a collection of particles under various conditions in which the molecules
can fluctuate. In this paper, we explore and adapt the soft prompt-based
learning method to molecular dynamics tasks. Our model can remarkably
generalize to unseen and out-of-distribution scenarios with limited training
data. While our work focuses on temperature as a test case, the versatility of
our approach allows for efficient simulation through any continuous dynamic
conditions, such as pressure and volumes. Our framework has two stages: 1)
Pre-trains with data mixing technique, augments molecular structure data and
temperature prompts, then applies a curriculum learning method by increasing
the ratio of them smoothly. 2) Meta-learning-based fine-tuning framework
improves sample-efficiency of fine-tuning process and gives the soft
prompt-tuning better initialization points. Comprehensive experiments reveal
that our framework excels in accuracy for in-domain data and demonstrates
strong generalization capabilities for unseen and out-of-distribution samples
Articulated Object Manipulation with Coarse-to-fine Affordance for Mitigating the Effect of Point Cloud Noise
3D articulated objects are inherently challenging for manipulation due to the
varied geometries and intricate functionalities associated with articulated
objects.Point-level affordance, which predicts the per-point actionable score
and thus proposes the best point to interact with, has demonstrated excellent
performance and generalization capabilities in articulated object manipulation.
However, a significant challenge remains: while previous works use perfect
point cloud generated in simulation, the models cannot directly apply to the
noisy point cloud in the real-world. To tackle this challenge, we leverage the
property of real-world scanned point cloud that, the point cloud becomes less
noisy when the camera is closer to the object. Therefore, we propose a novel
coarse-to-fine affordance learning pipeline to mitigate the effect of point
cloud noise in two stages. In the first stage, we learn the affordance on the
noisy far point cloud which includes the whole object to propose the
approximated place to manipulate. Then, we move the camera in front of the
approximated place, scan a less noisy point cloud containing precise local
geometries for manipulation, and learn affordance on such point cloud to
propose fine-grained final actions. The proposed method is thoroughly evaluated
both using large-scale simulated noisy point clouds mimicking real-world scans,
and in the real world scenarios, with superiority over existing methods,
demonstrating the effectiveness in tackling the noisy real-world point cloud
problem.Comment: ICRA 202
Electrochemical Oxidation of Cysteine at a Film Gold Modified Carbon Fiber Microelectrode Its Application in a Flow—Through Voltammetric Sensor
A flow-electrolytical cell containing a strand of micro Au modified carbon fiber electrodes (CFE) has been designedand characterized for use in a voltammatric detector for detecting cysteine using high-performance liquid chromatography. Cysteine is more efficiently electrochemical oxidized on a Au /CFE than a bare gold and carbon fiber electrode. The possible reaction mechanism of the oxidation process is described from the relations to scan rate, peak potentials and currents. For the pulse mode, and measurements with suitable experimental parameters, a linear concentration from 0.5 to 5.0 mg·L−1 was found. The limit of quantification for cysteine was below 60 ng·mL−1
Overview of predictive maintenance based on digital twin technology
The upgrade and development of manufacturing industry makes predictive maintenance more and more important, but the traditional predictive maintenance can not meet the development needs in many cases. In recent years, predictive maintenance based on digital twin has become a research hotspot in the manufacturing industry field. Firstly, this paper introduces the general methods of digital twin technology and predictive maintenance technology, analyzes the gap between them, and points out the importance of using digital twin technology to realize predictive maintenance. Secondly, this paper introduces the predictive maintenance method based on digital twin (PdMDT), introduces its characteristics, and gives its differences from traditional predictive maintenance. Thirdly, this paper introduces the application of this method in intelligent manufacturing, power industry, construction industry, aerospace industry, shipbuilding industry, and summarizes the latest development in these fields. Finally, the PdMDT puts forwards a reference framework in manufacturing industry, the framework describes the specific implementation process of equipment maintenance, and gives an example of industrial robot using the framework, and discusses the limitations, challenges and opportunities of the PdMDT
Attention-Assisted Feature Comparison and Feature Enhancement for Class-Agnostic Counting
In this study, we address the class-agnostic counting (CAC) challenge, aiming to count instances in a query image, using just a few exemplars. Recent research has shifted towards few-shot counting (FSC), which involves counting previously unseen object classes. We present ACECount, an FSC framework that combines attention mechanisms and convolutional neural networks (CNNs). ACECount identifies query image–exemplar similarities, using cross-attention mechanisms, enhances feature representations with a feature attention module, and employs a multi-scale regression head, to handle scale variations in CAC. ACECount’s experiments on theFSC-147 dataset exhibited the expected performance. ACECount achieved a reduction of 0.3 in the mean absolute error (MAE) on the validation set and a reduction of 0.26 on the test set of FSC-147, compared to previous methods. Notably, ACECount also demonstrated convincing performance in class-specific counting (CSC) tasks. Evaluation on crowd and vehicle counting datasets revealed that ACECount surpasses FSC algorithms like GMN, FamNet, SAFECount, LOCA, and SPDCN, in terms of performance. These results highlight the robust dataset generalization capabilities of our proposed algorithm
Sigma-1 receptors amplify dopamine D1 receptor signaling at presynaptic sites in the prelimbic cortex
AbstractSigma-1 receptors are highly expressed in the brain. The downstream signaling mechanisms associated with the sigma-1 receptor activation have been shown to involve the activation of protein kinase C (PKC), the control of Ca2 homoeostasis and the regulation of voltage- and ligand-gated ion channels. But few studies examined the regulatory effect of sigma-1 receptors on metabotropic receptor signaling. The present paper studied the regulatory effect of sigma-1 receptors on the signaling of dopamine D1 receptors, one of metabotropic receptors, by examining the effect of sigma-1 receptor agonists on the D1 receptor agonist-induced cAMP-dependent protein kinase (PKA) activation at presynaptic sites using the synaptosomes from the prelimbic cortex. The results showed that sigma-1 receptor agonists alone had no effects on the PKA activity, but could amplify the D1 receptor agonist-induced PKA activation. The sigma-1 receptor agonist also amplified the membrane-permeable analog of cAMP- and the adenylyl cyclase (AC) activator-induced PKA activation, but did not on the D1 receptor agonist-induced AC activation. The conventional PKC (cPKC), especially the PKCβI, and the extracellular Ca2+ influx through L-type Ca2+ channels might play key roles in the amplifying effect of the sigma-1 receptor agonists. The activation of PKC by sigma-1 receptor agonists was the upstream event of the increase in the intrasynaptosomal Ca2+ concentration. These results suggest that sigma-1 receptors may amplify the D1 receptor agonist-induced PKA activation by sigma-1 receptors - cPKC (especially the PKCβI) - L-type Ca2+ channels - Ca2+ - AC and/or cAMP signaling pathway