260 research outputs found
An iterative data-driven turbulence modeling framework based on Reynolds stress representation
Data-driven turbulence modeling studies have reached such a stage that the
fundamental framework is basically settled, but several essential issues remain
that strongly affect the performance, including accuracy, smoothness, and
generalization capacity. Two problems are studied in the current research: (1)
the processing of the Reynolds stress tensor and (2) the coupling method
between the machine learning turbulence model and CFD solver. The first
determines the form of predicting targets and the resulting physical
completeness and interpretability. The second determines the training process
and intrinsic relevance between the mean flow features and Reynolds stress. For
the Reynolds stress processing issue, we perform the theoretical derivation to
extend the relevant tensor arguments of Reynolds stress in addition to the
strain rate and rotation rate. Then, the tensor representation theorem is
employed to give the complete irreducible invariants and integrity basis. In
addition, an adaptive regularization term is employed to enhance the
representation performance. For the CFD coupling issue, an iterative coupling
data-driven turbulence modeling framework with consistent convergence is
proposed. The training data preparation, predicting target selection, and
computation platform are illustrated. The framework is then applied to a
canonical separated flow for verification. The mean flow results obtained by
coupling computation of the trained machine learning model and CFD solver have
high consistency with the DNS true values, which proves the validity of the
current approach
Understanding Deep Architectures with Reasoning Layer
Recently, there has been a surge of interest in combining deep learning
models with reasoning in order to handle more sophisticated learning tasks. In
many cases, a reasoning task can be solved by an iterative algorithm. This
algorithm is often unrolled, and used as a specialized layer in the deep
architecture, which can be trained end-to-end with other neural components.
Although such hybrid deep architectures have led to many empirical successes,
the theoretical foundation of such architectures, especially the interplay
between algorithm layers and other neural layers, remains largely unexplored.
In this paper, we take an initial step towards an understanding of such hybrid
deep architectures by showing that properties of the algorithm layers, such as
convergence, stability, and sensitivity, are intimately related to the
approximation and generalization abilities of the end-to-end model.
Furthermore, our analysis matches closely our experimental observations under
various conditions, suggesting that our theory can provide useful guidelines
for designing deep architectures with reasoning layers.Comment: 34th Conference on Neural Information Processing Systems (NeurIPS
2020
Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene
ACKNOWLEDGMENTS This work was financially supported by National Natural Science Foundation of China (21908002) and the Fundamental Research Funds for the Central Universities (buctrc201921, JD2108).Peer reviewedPostprin
Affordance Diffusion: Synthesizing Hand-Object Interactions
Recent successes in image synthesis are powered by large-scale diffusion
models. However, most methods are currently limited to either text- or
image-conditioned generation for synthesizing an entire image, texture transfer
or inserting objects into a user-specified region. In contrast, in this work we
focus on synthesizing complex interactions (ie, an articulated hand) with a
given object. Given an RGB image of an object, we aim to hallucinate plausible
images of a human hand interacting with it. We propose a two-step generative
approach: a LayoutNet that samples an articulation-agnostic
hand-object-interaction layout, and a ContentNet that synthesizes images of a
hand grasping the object given the predicted layout. Both are built on top of a
large-scale pretrained diffusion model to make use of its latent
representation. Compared to baselines, the proposed method is shown to
generalize better to novel objects and perform surprisingly well on
out-of-distribution in-the-wild scenes of portable-sized objects. The resulting
system allows us to predict descriptive affordance information, such as hand
articulation and approaching orientation. Project page:
https://judyye.github.io/affordiffusion-ww
Metal-Organic Framework-Derived Ni-S/C Catalysts for Selective Alkyne Hydrogenation
Acknowledgments This work was financially supported by the National Natural Science Foundation of China (22278017), the Fundamental Research Funds for the Central Universities (buctrc202303, JD2325), and the Young Elite Scientists Sponsorship Program by BAST (No. BYESS2023087).Peer reviewedPostprin
Understanding the Role of Coordinatively Unsaturated Al3+ Sites on Nanoshaped Al2O3 for Creating Uniform Ni–Cu Alloys for Selective Hydrogenation of Acetylene
Acknowledgments This work was financially supported by the National Key R&D Program of China (2021YFB3801600), the National Natural Science Foundation of China (22218017), and the Fundamental Research Funds for the Central Universities (buctrc201921, JD2223). We acknowledge the Beijing Synchrotron Radiation Facility (BSRF) for providing the experimental resources for XAS experiments.Peer reviewedPostprin
Chiral charge density wave and backscattering-immune orbital texture in monolayer 1T-TiTe2
Non-trivial electronic states are attracting intense attention in
low-dimensional physics. Though chirality has been identified in charge states
with a scalar order parameter, its intertwining with charge density waves
(CDW), film thickness and the impact on the electronic behaviors remain less
well understood. Here, using scanning tunneling microscopy, we report a 2 x 2
chiral CDW as well as a strong suppression of the Te-5p hole-band
backscattering in monolayer 1T-TiTe2. These exotic characters vanish in bilayer
TiTe2 with a non-CDW state. Theoretical calculations approve that chirality
comes from a helical stacking of the triple-q CDW components and therefore can
persist at the two-dimensional limit. Furthermore, the chirality renders the
Te-5p bands an unconventional orbital texture that prohibits electron
backscattering. Our study establishes TiTe2 as a promising playground for
manipulating the chiral ground states at the monolayer limit and provides a
novel path to engineer electronic properties from an orbital degree.Comment: 21 pages, 5 figure
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