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Uncertainty Quantification in Scientific Machine Learning: Methods, Metrics, and Comparisons

arXiv.org Artificial Intelligence

Neural networks (NNs) are currently changing the computational paradigm on how to combine data with mathematical laws in physics and engineering in a profound way, tackling challenging inverse and ill-posed problems not solvable with traditional methods. However, quantifying errors and uncertainties in NN-based inference is more complicated than in traditional methods. This is because in addition to aleatoric uncertainty associated with noisy data, there is also uncertainty due to limited data, but also due to NN hyperparameters, overparametrization, optimization and sampling errors as well as model misspecification. Although there are some recent works on uncertainty quantification (UQ) in NNs, there is no systematic investigation of suitable methods towards quantifying the total uncertainty effectively and efficiently even for function approximation, and there is even less work on solving partial differential equations and learning operator mappings between infinite-dimensional function spaces using NNs. In this work, we present a comprehensive framework that includes uncertainty modeling, new and existing solution methods, as well as evaluation metrics and post-hoc improvement approaches. To demonstrate the applicability and reliability of our framework, we present an extensive comparative study in which various methods are tested on prototype problems, including problems with mixed input-output data, and stochastic problems in high dimensions. In the Appendix, we include a comprehensive description of all the UQ methods employed, which we will make available as open-source library of all codes included in this framework.


Machine-Learning enabled analysis of ELM filament dynamics in KSTAR

arXiv.org Artificial Intelligence

The emergence and dynamics of filamentary structures associated with edge-localized modes (ELMs) inside tokamak plasmas during high-confinement mode is regularly studied using Electron Cyclotron Emission Imaging (ECEI) diagnostic systems. Such diagnostics allow us to infer electron temperature variations, often across a poloidal cross-section. Previously, detailed analysis of these filamentary dynamics and classification of the precursors to edge-localized crashes has been done manually. We present a machine-learning-based model, capable of automatically identifying the position, spatial extend, and amplitude of ELM filaments. The model is a deep convolutional neural network that has been trained and optimized on an extensive set of manually labeled ECEI data from the KSTAR tokamak. Once trained, the model achieves a $93.7\%$ precision and allows us to robustly identify plasma filaments in unseen ECEI data. The trained model is used to characterize ELM filament dynamics in a single H-mode plasma discharge. We identify quasi-periodic oscillations of the filaments size, total heat content, and radial velocity. The detailed dynamics of these quantities appear strongly correlated with each other and appear qualitatively different during the pre-crash and ELM crash phases.


Data vs. Disaster: 5 Ways Analytics Is Helping Tackle Climate Change - DATAVERSITY

#artificialintelligence

With the recent Intergovernmental Panel on Climate Change (IPPC) report painting a worrying picture of our battle against climate change, we will explore five ways analytics can help turn the tide. The UN Secretary-General, Antonio Guterres, called the report "a code red for humanity," adding that "the alarm bells are deafening and evidence irrefutable." U.S. President Joe Biden said about it, "The cost of inaction is mounting." In summary, without immediate action, the damage we've done may be irreversible. For this to change, we're going to have to rely on the latest tools and technologies, including big data, advanced analytics, modeling, and simulation techniques.


Houthi drone attacks expose UAE vulnerabilities, say analysts

Al Jazeera

A deadly drone attack by Yemen's Houthis on the United Arab Emirates (UAE) has exposed the country's vulnerability while jeopardising its reputation as a tourism and business hub and pushing it towards rapprochement with neighbouring Tehran, say analysts. The Iran-backed Houthi rebel group targeted a key oil facility in Abu Dhabi, killing three people. The suspected drone attack also caused a fire at Abu Dhabi's international airport, attracting condemnation and a pledge for retaliation from the UAE. Hailing the attack as "a successful military operation", the Houthi military spokesman Yahya Saree warned they could target more facilities in the UAE, which has been part of the Saudi-led war on Yemen that has killed tens of thousands of people and pushed the country towards humanitarian catastrophe. On Tuesday, Saudi Arabia launched air raids in the Yemeni capital Sanaa, killing more than a dozen people.


Deadly drone strikes on UAE raise Gulf tensions and roil oil market

The Japan Times

Iran-backed Yemeni fighters launched drone strikes on the United Arab Emirates that caused explosions and a deadly fire outside the capital, Abu Dhabi, ratcheting up security risks in the major oil-exporting region at a critical time. One of the biggest attacks to date on UAE soil ignited a fire at Abu Dhabi's main international airport on Monday and set fuel tanker trucks ablaze in a nearby industrial area. It took place days after Yemen's Houthi fighters warned Abu Dhabi against intensifying its air campaign against them. Crude extended gains to the highest level in seven years on Tuesday after the assaults in the UAE, OPEC's third biggest oil producer. Iran's longtime support of the Houthis means the incidents could roil regional diplomatic efforts to ease frictions and separate talks to restore Tehran's 2015 nuclear deal with world powers.


Knock Detection in Combustion Engine Time Series Using a Theory-Guided 1D Convolutional Neural Network Approach

arXiv.org Artificial Intelligence

This paper introduces a method for the detection of knock occurrences in an internal combustion engine (ICE) using a 1D convolutional neural network trained on in-cylinder pressure data. The model architecture was based on considerations regarding the expected frequency characteristics of knocking combustion. To aid the feature extraction, all cycles were reduced to 60{\deg} CA long windows, with no further processing applied to the pressure traces. The neural networks were trained exclusively on in-cylinder pressure traces from multiple conditions and labels provided by human experts. The best-performing model architecture achieves an accuracy of above 92% on all test sets in a tenfold cross-validation when distinguishing between knocking and non-knocking cycles. In a multi-class problem where each cycle was labeled by the number of experts who rated it as knocking, 78% of cycles were labeled perfectly, while 90% of cycles were classified at most one class from ground truth. They thus considerably outperform the broadly applied MAPO (Maximum Amplitude of Pressure Oscillation) detection method, as well as other references reconstructed from previous works. Our analysis indicates that the neural network learned physically meaningful features connected to engine-characteristic resonance frequencies, thus verifying the intended theory-guided data science approach. Deeper performance investigation further shows remarkable generalization ability to unseen operating points. In addition, the model proved to classify knocking cycles in unseen engines with increased accuracy of 89% after adapting to their features via training on a small number of exclusively non-knocking cycles. The algorithm takes below 1 ms (on CPU) to classify individual cycles, effectively making it suitable for real-time engine control.


AI for Closed-Loop Control Systems -- New Opportunities for Modeling, Designing, and Tuning Control Systems

arXiv.org Artificial Intelligence

Control Systems, particularly closed-loop control systems (CLCS), are frequently used in production machines, vehicles, and robots nowadays. CLCS are needed to actively align actual values of a process to a given reference or set values in real-time with a very high precession. Yet, artificial intelligence (AI) is not used to model, design, optimize, and tune CLCS. This paper will highlight potential AI-empowered and -based control system designs and designing procedures, gathering new opportunities and research direction in the field of control system engineering. Therefore, this paper illustrates which building blocks within the standard block diagram of CLCS can be replaced by AI, i.e., artificial neuronal networks (ANN). Having processes with real-time contains and functional safety in mind, it is discussed if AI-based controller blocks can cope with these demands. By concluding the paper, the pros and cons of AI-empowered as well as -based CLCS designs are discussed, and possible research directions for introducing AI in the domain of control system engineering are given.


WATCH: Wasserstein Change Point Detection for High-Dimensional Time Series Data

arXiv.org Artificial Intelligence

Detecting relevant changes in dynamic time series data in a timely manner is crucially important for many data analysis tasks in real-world settings. Change point detection methods have the ability to discover changes in an unsupervised fashion, which represents a desirable property in the analysis of unbounded and unlabeled data streams. However, one limitation of most of the existing approaches is represented by their limited ability to handle multivariate and high-dimensional data, which is frequently observed in modern applications such as traffic flow prediction, human activity recognition, and smart grids monitoring. In this paper, we attempt to fill this gap by proposing WATCH, a novel Wasserstein distance-based change point detection approach that models an initial distribution and monitors its behavior while processing new data points, providing accurate and robust detection of change points in dynamic high-dimensional data. An extensive experimental evaluation involving a large number of benchmark datasets shows that WATCH is capable of accurately identifying change points and outperforming state-of-the-art methods.


Frequent Itemset-driven Search for Finding Minimum Node Separators in Complex Networks

arXiv.org Artificial Intelligence

Finding an optimal set of critical nodes in a complex network has been a long-standing problem in the fields of both artificial intelligence and operations research. Potential applications include epidemic control, network security, carbon emission monitoring, emergence response, drug design, and vulnerability assessment. In this work, we consider the problem of finding a minimal node separator whose removal separates a graph into multiple different connected components with fewer than a limited number of vertices in each component. To solve it, we propose a frequent itemset-driven search approach, which integrates the concept of frequent itemset mining in data mining into the well-known memetic search framework. Starting from a high-quality population built by the solution construction and population repair procedures, it iteratively employs the frequent itemset recombination operator (to generate promising offspring solution based on itemsets that frequently occur in high-quality solutions), tabu search-based simulated annealing (to find high-quality local optima), population repair procedure (to modify the population), and rank-based population management strategy (to guarantee a healthy population). Extensive evaluations on 50 widely used benchmark instances show that it significantly outperforms state-of-the-art algorithms. In particular, it discovers 29 new upper bounds and matches 18 previous best-known bounds. Finally, experimental analyses are performed to confirm the effectiveness of key algorithmic modules of the proposed method.


Why AI software companies are betting on small data to spot manufacturing defects

#artificialintelligence

To the uninitiated, a tiny stain on several yards of car seat upholstery or a minuscule gas bubble on the surface of an industrial oil pipe might seem like an insignificant imperfection. But factory inspectors are always on the lookout for these sorts of defects, because they can create serious slowdowns in time-sensitive manufacturing production schedules. Cameras and computer vision software have been used to spot product flaws in manufacturing facilities for decades, but today companies including Landing AI and Mariner are helping take defect detection to the next level with AI software. Rather than offering off-the-shelf AI, these companies are betting that manufacturers want highly customized algorithmic models to monitor for product defects. And they have another selling point that flies in the face of what we know about most big data-hungry AI systems: Their models work using very small datasets.