512 research outputs found
Predicting Remaining Useful Life using Time Series Embeddings based on Recurrent Neural Networks
We consider the problem of estimating the remaining useful life (RUL) of a
system or a machine from sensor data. Many approaches for RUL estimation based
on sensor data make assumptions about how machines degrade. Additionally,
sensor data from machines is noisy and often suffers from missing values in
many practical settings. We propose Embed-RUL: a novel approach for RUL
estimation from sensor data that does not rely on any degradation-trend
assumptions, is robust to noise, and handles missing values. Embed-RUL utilizes
a sequence-to-sequence model based on Recurrent Neural Networks (RNNs) to
generate embeddings for multivariate time series subsequences. The embeddings
for normal and degraded machines tend to be different, and are therefore found
to be useful for RUL estimation. We show that the embeddings capture the
overall pattern in the time series while filtering out the noise, so that the
embeddings of two machines with similar operational behavior are close to each
other, even when their sensor readings have significant and varying levels of
noise content. We perform experiments on publicly available turbofan engine
dataset and a proprietary real-world dataset, and demonstrate that Embed-RUL
outperforms the previously reported state-of-the-art on several metrics.Comment: Presented at 2nd ML for PHM Workshop at SIGKDD 2017, Halifax, Canad
Deep learning for time series classification: a review
Time Series Classification (TSC) is an important and challenging problem in
data mining. With the increase of time series data availability, hundreds of
TSC algorithms have been proposed. Among these methods, only a few have
considered Deep Neural Networks (DNNs) to perform this task. This is surprising
as deep learning has seen very successful applications in the last years. DNNs
have indeed revolutionized the field of computer vision especially with the
advent of novel deeper architectures such as Residual and Convolutional Neural
Networks. Apart from images, sequential data such as text and audio can also be
processed with DNNs to reach state-of-the-art performance for document
classification and speech recognition. In this article, we study the current
state-of-the-art performance of deep learning algorithms for TSC by presenting
an empirical study of the most recent DNN architectures for TSC. We give an
overview of the most successful deep learning applications in various time
series domains under a unified taxonomy of DNNs for TSC. We also provide an
open source deep learning framework to the TSC community where we implemented
each of the compared approaches and evaluated them on a univariate TSC
benchmark (the UCR/UEA archive) and 12 multivariate time series datasets. By
training 8,730 deep learning models on 97 time series datasets, we propose the
most exhaustive study of DNNs for TSC to date.Comment: Accepted at Data Mining and Knowledge Discover
MultiWave: Multiresolution Deep Architectures through Wavelet Decomposition for Multivariate Time Series Prediction
The analysis of multivariate time series data is challenging due to the
various frequencies of signal changes that can occur over both short and long
terms. Furthermore, standard deep learning models are often unsuitable for such
datasets, as signals are typically sampled at different rates. To address these
issues, we introduce MultiWave, a novel framework that enhances deep learning
time series models by incorporating components that operate at the intrinsic
frequencies of signals. MultiWave uses wavelets to decompose each signal into
subsignals of varying frequencies and groups them into frequency bands. Each
frequency band is handled by a different component of our model. A gating
mechanism combines the output of the components to produce sparse models that
use only specific signals at specific frequencies. Our experiments demonstrate
that MultiWave accurately identifies informative frequency bands and improves
the performance of various deep learning models, including LSTM, Transformer,
and CNN-based models, for a wide range of applications. It attains top
performance in stress and affect detection from wearables. It also increases
the AUC of the best-performing model by 5% for in-hospital COVID-19 mortality
prediction from patient blood samples and for human activity recognition from
accelerometer and gyroscope data. We show that MultiWave consistently
identifies critical features and their frequency components, thus providing
valuable insights into the applications studied.Comment: Published in the Conference on Health, Inference, and Learning (CHIL
2023
Methods for cleaning the BOLD fMRI signal
Available online 9 December 2016
http://www.sciencedirect.com/science/article/pii/S1053811916307418?via%3Dihubhttp://www.sciencedirect.com/science/article/pii/S1053811916307418?via%3DihubBlood oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) has rapidly become a popular technique for the investigation of brain function in healthy individuals, patients as well as in animal studies. However, the BOLD signal arises from a complex mixture of neuronal, metabolic and vascular processes, being therefore an indirect measure of neuronal activity, which is further severely corrupted by multiple non-neuronal fluctuations of instrumental, physiological or subject-specific origin. This review aims to provide a comprehensive summary of existing methods for cleaning the BOLD fMRI signal. The description is given from a methodological point of view, focusing on the operation of the different techniques in addition to pointing out the advantages and limitations in their application. Since motion-related and physiological noise fluctuations are two of the main noise components of the signal, techniques targeting their removal are primarily addressed, including both data-driven approaches and using external recordings. Data-driven approaches, which are less specific in the assumed model and can simultaneously reduce multiple noise fluctuations, are mainly based on data decomposition techniques such as principal and independent component analysis. Importantly, the usefulness of strategies that benefit from the information available in the phase component of the signal, or in multiple signal echoes is also highlighted. The use of global signal regression for denoising is also addressed. Finally, practical recommendations regarding the optimization of the preprocessing pipeline for the purpose of denoising and future venues of research are indicated. Through the review, we summarize the importance of signal denoising as an essential step in the analysis pipeline of task-based and resting state fMRI studies.This work was supported by the Spanish Ministry of Economy and
Competitiveness [Grant PSI 2013–42343 Neuroimagen Multimodal],
the Severo Ochoa Programme for Centres/Units of Excellence in R & D
[SEV-2015-490], and the research and writing of the paper were
supported by the NIMH and NINDS Intramural Research Programs
(ZICMH002888) of the NIH/HHS
Wind power prediction based on WT-BiGRU-attention-TCN model
Accurate wind power prediction is crucial for the safe and stable operation of the power grid. However, wind power generation has large random volatility and intermittency, which increases the difficulty of prediction. In order to construct an effective prediction model based on wind power generation power and achieve stable grid dispatch after wind power is connected to the grid, a wind power generation prediction model based on WT-BiGRU-Attention-TCN is proposed. First, wavelet transform (WT) is used to reduce noises of the sample data. Then, the temporal attention mechanism is incorporated into the bi-directional gated recurrent unit (BiGRU) model to highlight the impact of key time steps on the prediction results while fully extracting the temporal features of the context. Finally, the model performance is enhanced by further extracting more high-level temporal features through a temporal convolutional neural network (TCN). The results show that our proposed model outperforms other baseline models, achieving a root mean square error of 0.066 MW, a mean absolute percentage error of 18.876%, and the coefficient of determination (R2) reaches 0.976. It indicates that the noise-reduction WT technique can significantly improve the model performance, and also shows that using the temporal attention mechanism and TCN can further improve the prediction accuracy
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