174 research outputs found
Analysis of weak faults of planetary gears based on frequency domain information exchange method
This paper focuses on solving a series of problems, in particular, the extraction of planetary gear fault characteristics for cracked and broken teeth, using the frequency domain information exchange method. First, we discuss deficiencies in classical stochastic resonance fault feature extraction method. A number of issues are associated with adaptive stochastic resonance based on the re-scaling frequency method used during the small parameter issues, such as sampling frequency ratio constraints and easily induced aliasing of the target frequency band. Second, to overcome the above-mentioned problems, this paper proposes a frequency domain information exchange optimization method. Simulations were carried out used the proposed method and results were compared to those obtained using previously presented adaptive stochastic resonance based on the re-scaling frequency method. Finally, tests were performed on an experimental planetary gearbox failure platform to further verify the frequency domain information exchange method for effectively extracting planetary gear crack and missing tooth fault features
Distinct fingerprints of charge density waves and electronic standing waves in ZrTe
Experimental signatures of charge density waves (CDW) in high-temperature
superconductors have evoked much recent interest, yet an alternative
interpretation has been theoretically raised based on electronic standing waves
resulting from quasiparticles scattering off impurities or defects, also known
as Friedel oscillations (FO). Indeed the two phenomena are similar and related,
posing a challenge to their experimental differentiation. Here we report a
resonant X-ray diffraction study of ZrTe, a model CDW material. Near the
CDW transition, we observe two independent diffraction signatures that arise
concomitantly, only to become clearly separated in momentum while developing
very different correlation lengths in the well-ordered state. Anomalously slow
dynamics of mesoscopic ordered nanoregions are further found near the
transition temperature, in spite of the expected strong thermal fluctuations.
These observations reveal that a spatially-modulated CDW phase emerges out of a
uniform electronic fluid via a process that is promoted by self-amplifying FO,
and identify a viable experimental route to distinguish CDW and FO.Comment: 6 pages, 4 figures; supplementary information available upon reques
Correlative Channel-Aware Fusion for Multi-View Time Series Classification
Multi-view time series classification (MVTSC) aims to improve the performance
by fusing the distinctive temporal information from multiple views. Existing
methods mainly focus on fusing multi-view information at an early stage, e.g.,
by learning a common feature subspace among multiple views. However, these
early fusion methods may not fully exploit the unique temporal patterns of each
view in complicated time series. Moreover, the label correlations of multiple
views, which are critical to boost-ing, are usually under-explored for the
MVTSC problem. To address the aforementioned issues, we propose a Correlative
Channel-Aware Fusion (C2AF) network. First, C2AF extracts comprehensive and
robust temporal patterns by a two-stream structured encoder for each view, and
captures the intra-view and inter-view label correlations with a graph-based
correlation matrix. Second, a channel-aware learnable fusion mechanism is
implemented through convolutional neural networks to further explore the global
correlative patterns. These two steps are trained end-to-end in the proposed
C2AF network. Extensive experimental results on three real-world datasets
demonstrate the superiority of our approach over the state-of-the-art methods.
A detailed ablation study is also provided to show the effectiveness of each
model component
OCCL: a Deadlock-free Library for GPU Collective Communication
Various distributed deep neural network (DNN) training technologies lead to
increasingly complicated use of collective communications on GPU. The
deadlock-prone collectives on GPU force researchers to guarantee that
collectives are enqueued in a consistent order on each GPU to prevent
deadlocks. In complex distributed DNN training scenarios, manual hardcoding is
the only practical way for deadlock prevention, which poses significant
challenges to the development of artificial intelligence. This paper presents
OCCL, which is, to the best of our knowledge, the first deadlock-free
collective communication library for GPU supporting dynamic decentralized
preemption and gang-scheduling for collectives. Leveraging the preemption
opportunity of collectives on GPU, OCCL dynamically preempts collectives in a
decentralized way via the deadlock-free collective execution framework and
allows dynamic decentralized gang-scheduling via the stickiness adjustment
scheme. With the help of OCCL, researchers no longer have to struggle to get
all GPUs to launch collectives in a consistent order to prevent deadlocks. We
implement OCCL with several optimizations and integrate OCCL with a distributed
deep learning framework OneFlow. Experimental results demonstrate that OCCL
achieves comparable or better latency and bandwidth for collectives compared to
NCCL, the state-of-the-art. When used in distributed DNN training, OCCL can
improve the peak training throughput by up to 78% compared to statically
sequenced NCCL, while introducing overheads of less than 6.5% across various
distributed DNN training approaches
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