Overview
Forecast combinations: an over 50-year review
Wang, Xiaoqian, Hyndman, Rob J, Li, Feng, Kang, Yanfei
Forecast combinations have flourished remarkably in the forecasting community and, in recent years, have become part of the mainstream of forecasting research and activities. Combining multiple forecasts produced from single (target) series is now widely used to improve accuracy through the integration of information gleaned from different sources, thereby mitigating the risk of identifying a single "best" forecast. Combination schemes have evolved from simple combination methods without estimation, to sophisticated methods involving time-varying weights, nonlinear combinations, correlations among components, and cross-learning. They include combining point forecasts and combining probabilistic forecasts. This paper provides an up-to-date review of the extensive literature on forecast combinations, together with reference to available open-source software implementations. We discuss the potential and limitations of various methods and highlight how these ideas have developed over time. Some important issues concerning the utility of forecast combinations are also surveyed. Finally, we conclude with current research gaps and potential insights for future research.
Autoencoder Based Iterative Modeling and Multivariate Time-Series Subsequence Clustering Algorithm
Köhne, Jonas, Henning, Lars, Gühmann, Clemens
This paper introduces an algorithm for the detection of change-points and the identification of the corresponding subsequences in transient multivariate time-series data (MTSD). The analysis of such data has become more and more important due to the increase of availability in many industrial fields. Labeling, sorting or filtering highly transient measurement data for training condition based maintenance (CbM) models is cumbersome and error-prone. For some applications it can be sufficient to filter measurements by simple thresholds or finding change-points based on changes in mean value and variation. But a robust diagnosis of a component within a component group for example, which has a complex non-linear correlation between multiple sensor values, a simple approach would not be feasible. No meaningful and coherent measurement data which could be used for training a CbM model would emerge. Therefore, we introduce an algorithm which uses a recurrent neural network (RNN) based Autoencoder (AE) which is iteratively trained on incoming data. The scoring function uses the reconstruction error and latent space information. A model of the identified subsequence is saved and used for recognition of repeating subsequences as well as fast offline clustering. For evaluation, we propose a new similarity measure based on the curvature for a more intuitive time-series subsequence clustering metric. A comparison with seven other state-of-the-art algorithms and eight datasets shows the capability and the increased performance of our algorithm to cluster MTSD online and offline in conjunction with mechatronic systems.
Toward Smart Doors: A Position Paper
Capogrosso, Luigi, Skenderi, Geri, Girella, Federico, Fummi, Franco, Cristani, Marco
Conventional automatic doors cannot distinguish between people wishing to pass through the door and people passing by the door, so they often open unnecessarily. This leads to the need to adopt new systems in both commercial and non-commercial environments: smart doors. In particular, a smart door system predicts the intention of people near the door based on the social context of the surrounding environment and then makes rational decisions about whether or not to open the door. This work proposes the first position paper related to smart doors, without bells and whistles. We first point out that the problem not only concerns reliability, climate control, safety, and mode of operation. Indeed, a system to predict the intention of people near the door also involves a deeper understanding of the social context of the scene through a complex combined analysis of proxemics and scene reasoning. Furthermore, we conduct an exhaustive literature review about automatic doors, providing a novel system formulation. Also, we present an analysis of the possible future application of smart doors, a description of the ethical shortcomings, and legislative issues.
From Weakly Supervised Learning to Active Learning
Applied mathematics and machine computations have raised a lot of hope since the recent success of supervised learning. Many practitioners in industries have been trying to switch from their old paradigms to machine learning. Interestingly, those data scientists spend more time scrapping, annotating and cleaning data than fine-tuning models. This thesis is motivated by the following question: can we derive a more generic framework than the one of supervised learning in order to learn from clutter data? This question is approached through the lens of weakly supervised learning, assuming that the bottleneck of data collection lies in annotation. We model weak supervision as giving, rather than a unique target, a set of target candidates. We argue that one should look for an ``optimistic'' function that matches most of the observations. This allows us to derive a principle to disambiguate partial labels. We also discuss the advantage to incorporate unsupervised learning techniques into our framework, in particular manifold regularization approached through diffusion techniques, for which we derived a new algorithm that scales better with input dimension then the baseline method. Finally, we switch from passive to active weakly supervised learning, introducing the ``active labeling'' framework, in which a practitioner can query weak information about chosen data. Among others, we leverage the fact that one does not need full information to access stochastic gradients and perform stochastic gradient descent.
Smart Active Sampling to enhance Quality Assurance Efficiency
Heistracher, Clemens, Stricker, Stefan, Casas, Pedro, Schall, Daniel, Kemnitz, Jana
Therefore, quality control plays an important role. However, quality control is also a cost factor that can not be neglected [1]. This is especially true for those industries requiring inspections outside the production line, such as disruptive or non-disruptive testing [2]. Traditional sampling strategies are random sampling, where a fixed number of samples is taken randomly in a fixed interval or periodic sampling, where samples are taken at a fixed interval. However, both sampling strategies entail some disadvantages. A small sampling interval increases the chance of detecting defective parts but also increases sampling costs, especially using destructive testing.
A singular Riemannian geometry approach to Deep Neural Networks I. Theoretical foundations
Benfenati, Alessandro, Marta, Alessio
Deep Neural Networks are widely used for solving complex problems in several scientific areas, such as speech recognition, machine translation, image analysis. The strategies employed to investigate their theoretical properties mainly rely on Euclidean geometry, but in the last years new approaches based on Riemannian geometry have been developed. Motivated by some open problems, we study a particular sequence of maps between manifolds, with the last manifold of the sequence equipped with a Riemannian metric. We investigate the structures induced trough pullbacks on the other manifolds of the sequence and on some related quotients. In particular, we show that the pullbacks of the final Riemannian metric to any manifolds of the sequence is a degenerate Riemannian metric inducing a structure of pseudometric space, we show that the Kolmogorov quotient of this pseudometric space yields a smooth manifold, which is the base space of a particular vertical bundle. We investigate the theoretical properties of the maps of such sequence, eventually we focus on the case of maps between manifolds implementing neural networks of practical interest and we present some applications of the geometric framework we introduced in the first part of the paper.
KeypartX: Graph-based Perception (Text) Representation
The availability of big data has opened up big opportunities for individuals, businesses and academics to view big into what is happening in their world. Previous works of text representation mostly focused on informativeness from massive words' frequency or cooccurrence. However, big data is a double-edged sword which is big in volume but unstructured in format. The unstructured edge requires specific techniques to transform 'big' into meaningful instead of informative alone. This study presents KeypartX, a graph-based approach to represent perception (text in general) by key parts of speech. Different from bag-of-words/vector-based machine learning, this technique is human-like learning that could extracts meanings from linguistic (semantic, syntactic and pragmatic) information. Moreover, KeypartX is big-data capable but not hungry, which is even applicable to the minimum unit of text:sentence.
Emerging Trends in AI, Ultrasound and OB/GYN Care
From entertainment to commerce, artificial intelligence (AI) is making a difference in many aspects of life and has the power to advance diagnostics. Next-generation healthcare technology has begun implementing many AI-powered tools to improve efficacy and patient safety, and enhance the clinician experience.1 There are several image acquisition and analysis capabilities that can be enhanced by an AI application for each task.2 Nearly every woman requires an ultrasound at some point during their care. There is huge potential for AI to assist in repetitive tasks and provide promising workload-changing advances with the use of ultrasound in obstetrics and gynecologic (OB/GYN) care.2
Traffic Classification in an Increasingly Encrypted Web
Traffic classification is essential in network management for a wide range of operations. Recently, it has become increasingly challenging with the widespread adoption of encryption in the Internet, for example, as a de facto in HTTP/2 and QUIC protocols. In the current state of encrypted traffic classification using deep learning (DL), we identify fundamental issues in the way it is typically approached. For instance, although complex DL models with millions of parameters are being used, these models implement a relatively simple logic based on certain header fields of the TLS handshake, limiting model robustness to future versions of encrypted protocols. Furthermore, encrypted traffic is often treated as any other raw input for DL, while crucial domain-specific considerations are commonly ignored. In this paper, we design a novel feature engineering approach used for encrypted Web protocols, and develop a neural network architecture based on stacked long short-term memory layers and convolutional neural networks. We evaluate our approach on a real-world Web traffic dataset from a major Internet service provider and mobile network operator. We achieve an accuracy of 95% in service classification with less raw traffic and a smaller number of parameters, outperforming a state-of-the-art method by nearly 50% fewer false classifications. We show that our DL model generalizes for different classification objectives and encrypted Web protocols. We also evaluate our approach on a public QUIC dataset with finer application-level granularity in labeling, achieving an overall accuracy of 99%. Traffic classification is quintessential for network operators to perform a wide range of network operation and management activities. This includes capacity planning, security and intrusion detection, quality of service (QoS) assurance, performance monitoring, volumetry, and resource provisioning, to name a few. For example, an enterprise network administrator or Internet service provider (ISP) may want to prioritize traffic for business critical services, identify unknown traffic for anomaly detection, or perform workload characterization for designing efficient resource management schemes to satisfy performance and resource requirements of diverse applications. Depending on the context, misclassification on a large scale may result in failure to deliver QoS guarantees, high operational expenses, security breaches, or even disruption in services.
State of the art in the RoboCup Humanoid League
RoboCup is an initiative to promote research in robotics through standardized competition and cooperation. The RoboCup Humanoid League focuses on legged robots between 0.4–1 metres tall in the KidSize and 1–2 metres tall in AdultSize. This year the Hamburg Bit-Bots performed a survey of all KidSize teams participating in the RoboCup 2022 in Bangkok, Thailand. We aimed to capture the state of the art in the league. This article gives a summary of the results.