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Azim Ahmadzadeh - IEEE Xplore Author Profile

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Quantifying similarities between time series in a meaningful way remains a challenge in time series analysis, despite many advances in the field. Most real-world solutions still rely on a few popular measures, such as Euclidean Distance (EuD), Longest Common Subsequence (LCSS), and Dynamic Time Warping (DTW). The strengths and weaknesses of these measures have been studied extensively, and increme...Show More
In Machine Learning, a supervised model’s performance is measured using the evaluation metrics. In this study, we first present our motivation by revisiting the major limitations of these metrics, namely one-dimensionality, lack of context, lack of intuitiveness, uncomparability, binary restriction, and uncustomizability of metrics. In response, we propose Contingency Space, a bounded semimetric s...Show More
The class-imbalance issue is intrinsic to many real-world machine learning tasks, particularly to the rare-event classification problems. Although the impact and treatment of imbalanced data is widely known, the magnitude of a metric’s sensitivity to class imbalance has attracted little attention. As a result, often the sensitive metrics are dismissed while their sensitivity may only be marginal. ...Show More
The Space-Weather ANalytics for Solar Flares (SWAN-SF) is a multivariate time series benchmark dataset recently created to serve the heliophysics community as a testbed for solar flare forecasting models. SWAN-SF contains 54 unique features, with 24 quantitative features computed from the photospheric magnetic field maps of active regions, describing their precedent flare activity. In this study, ...Show More
General-purpose object-detection algorithms often dismiss the fine structure of detected objects. This can be traced back to how their proposed regions are evaluated. Our goal is to renegotiate the trade-off between the generality of these algorithms and their coarse detections. In this work, we present a new metric that is a marriage of a popular evaluation metric, namely Intersection over Union ...Show More
Forecasting the occurrence of solar flares is a typical 21st century rare-event classification task. Over the past two decades, many studies have implemented various techniques and approaches for classification of strong and weak solar flares. The release of the recent flare forecasting benchmark dataset, named SWAN-SF, has opened the door for taking advantage of multivariate time series (MVTS) of...Show More
Image super-resolution is a branch of image processing that is concerned with enhancing the spatial resolution and quality of images by learning the intrinsic details and relations between the lower resolution input and the higher resolution output images. It is widely accepted as an ill-posed problem, which has seen tremendous advancements with deep learning-based models. In this work, we present...Show More
Image super-resolution is a branch of image processing that is concerned with enhancing the spatial resolution and quality of images by learning the intrinsic details and relations between the lower resolution input and the higher resolution output images. It is widely accepted as an ill-posed problem, which has seen tremendous advancements with deep learning based models. In this work, we present...Show More
Space weather encapsulates the impact of variable solar activity on the vicinity of Earth and elsewhere in the solar system. A major agent of space weather, with significant effort already devoted to its prediction, is solar flares. Most existing analysis in this direction focus on the instantaneous (point-in-time) magnitude of various pre-flare parameters in flare host locations, solar active reg...Show More
We use a well-known deep neural network framework, called Mask R-CNN, for identification of solar filaments in full-disk H-$\alpha$ images from Big Bear Solar Observatory (BBSO). The image data, collected from BBSO's archive, are integrated with the spatiotemporal metadata of filaments retrieved from the Heliophysics Events Knowledgebase (HEK) system. This integrated data is then treated as the gr...Show More
Machine learning-based space weather analytics has attracted much attention due to the potential damages that can be caused by the extreme space weather events. Using a recently released data benchmark, named SWAN-SF, designed for solar flare forecasting based on the pre-flare time series of solar magnetic field parameters, we conduct a case study on the impacts of statistical features derived fro...Show More
In analyses of rare-events, regardless of the domain of application, class-imbalance issue is intrinsic. Although the challenges are known to data experts, their explicit impact on the analytic and the decisions made based on the findings are often overlooked. This is in particular prevalent in interdisciplinary research where the theoretical aspects are sometimes overshadowed by the challenges of...Show More
We present a case study for time series prediction models in extreme class-imbalance problems. We have extracted multiple properties from the Space Weather ANalytics for Solar Flares (SWAN-SF) benchmark dataset which comprises of magnetic features from over 4075 active regions over a period of 9 years to create the forecasting dataset used in this study. In the extracted dataset, the class-imbalan...Show More
Since its introduction to the computer science community, the Dynamic Time Warping (DTW) algorithm has demonstrated good performance with time series data. While this elastic measure is known for its effectiveness with time series sequence comparisons, the possibility of pathological warping paths weakens the algorithms potential considerably. Techniques centering on pruning off impossible mapping...Show More
Directionality as a textural parameter is a great tool in many image-based tasks including the automated analysis of medical, geographical, or astronomical images. Tamura directionality is a popular parameters that measures the degree of texture directionality of images. In this study, we review the original idea and also address some ambiguities present in the original definition that play an imp...Show More