Density-based Clustering by Means of Bridge Point Identification

Density-based clustering focuses on defining clusters consisting of contiguous regions characterized by similar densities of points. Traditional approaches identify core points first, whereas more recent ones initially identify the cluster borders and then propagate cluster labels within the delimited regions. Both strategies encounter issues in presence of multi-density regions or when clusters are characterized by noisy borders. To overcome the above issues, we present a new clustering algorithm that relies on the concept of bridge point. A bridge point is a point whose neighborhood includes points of different clusters. The key idea is to use bridge points, rather than border points, to partition points into clusters. We have proved that a correct bridge point identification yields a cluster separation consistent with the expectation. To correctly identify bridge points in absence of a priori cluster information we leverage an established unsupervised outlier detection algorithm. Specifically, we empirically show that, in most cases, the detected outliers are actually a superset of the bridge point set. Therefore, to define clusters we spread cluster labels like a wildfire until an outlier, acting as a candidate bridge point, is reached. The proposed algorithm performs statistically better than state-of-the-art methods on a large set of benchmark datasets and is particularly robust to the presence of intra-cluster multiple densities and noisy borders

A Data-Driven Based Dynamic Rebalancing Methodology for Bike Sharing Systems

Mobility in cities is a fundamental asset and opens several problems in decision making and the creation of new services for citizens. In the last years, transportation sharing systems have been continuously growing. Among these, bike sharing systems became commonly adopted. There exist two different categories of bike sharing systems: station-based systems and free-floating services. In this paper, we concentrate our analyses on station-based systems. Such systems require periodic rebalancing operations to guarantee good quality of service and system usability by moving bicycles from full stations to empty stations. In particular, in this paper, we propose a dynamic bicycle rebalancing methodology based on frequent pattern mining and its implementation. The extracted patterns represent frequent unbalanced situations among nearby stations. They are used to predict upcoming critical statuses and plan the most effective rebalancing operations using an entirely data-driven approach. Experiments performed on real data of the Barcelona bike sharing system show the effectiveness of the proposed approach

Double-Step U-Net: A Deep Learning-Based Approach for the Estimation of Wildfire Damage Severity through Sentinel-2 Satellite Data

Wildfire damage severity census is a crucial activity for estimating monetary losses and for planning a prompt restoration of the affected areas. It consists in assigning, after a wildfire, a numerical damage/severity level, between 0 and 4, to each sub-area of the hit area. While burned area identification has been automatized by means of machine learning algorithms, the wildfire damage severity census operation is usually still performed manually and requires a significant effort of domain experts through the analysis of imagery and, sometimes, on-site missions. In this paper, we propose a novel supervised learning approach for the automatic estimation of the damage/severity level of the hit areas after the wildfire extinction. Specifically, the proposed approach, leveraging on the combination of a classification algorithm and a regression one, predicts the damage/severity level of the sub-areas of the area under analysis by processing a single post-fire satellite acquisition. Our approach has been validated in five different European countries and on 21 wildfires. It has proved to be robust for the application in several geographical contexts presenting similar geological aspects

CaBuAr: California burned areas dataset for delineation [Software and Data Sets]

Forest wildfires represent one of the catastrophic events that, over the last decades, have caused huge environmental and humanitarian damage. In addition to a significant amount of carbon dioxide emission, they are a source of risk to society in both short-term (e.g., temporary city evacuation due to fire) and long-term (e.g., higher risks of landslides) cases. Consequently, the availability of tools to support local authorities in automatically identifying burned areas plays an important role in the continuous monitoring requirement to alleviate the aftereffects of such catastrophic events. The great availability of satellite acquisitions coupled with computer vision techniques represents an important step in developing such tools

Improving Wildfire Severity Classification of Deep Learning U-Nets from Satellite Images

Uncontrolled wildfires are dangerous events capable of harming people safety. To contrast their increasing impact in recent years, a key task is an accurate detection of the affected areas and their damage assessment from satellite images. Current state-of-the-art solutions address such problem through a double convolutional neural network able to automatically detect wildfires in satellite acquisitions and associate a damage index from a defined scale. However, such deep-learning model performance is strongly dependent on many factors. In this work, we specifically focus on a key parameter, i.e., the loss function, exploited in the underlying neural networks. Besides the state-of-the-art solutions based on the Dice-MSE, among the many loss functions proposed in literature, we focus on the Binary Cross-Entropy (BCE) and the Intersection over Union (IoU), as two representatives of the distribution-based and region-based categories, respectively. Experiments show that the BCE loss function coupled with a double-step U-Net architecture provides better results than current state-of-the-art solutions on a public labeled dataset of European wildfires

Supervised Burned Areas delineation by means of Sentinel-2 imagery and Convolutional Neural Networks

Wildfire events are increasingly threatening our lands, cities, and lives. To contrast this phenomenon and to limit its damages, governments around the globe are trying to find proper counter-measures, identifying prevention and monitoring as two key factors to reduce wildfires impact worldwide. In this work, we propose two deep convolutional neural networks to automatically detect and delineate burned areas from satellite acquisitions, assessing their performances at scale using validated maps of burned areas of historical wildfires. We demonstrate that the proposed networks substantially improve the burned area delineation accuracy over conventional methods

Double-Step deep learning framework to improve wildfire severity classification

Wildfires are dangerous events which cause huge losses under natural, humanitarian and economical perspectives. To contrast their impact, a fast and accurate restoration can be improved through the automatic census of the event in terms of (i) delin- eation of the affected areas and (ii) estimation of damage severity, using satellite images. This work proposes to extend the state- of-the-art approach, named Double-Step U-Net (DS-UNet), able to automatically detect wildfires in satellite acquisitions and to associate a damage index from a defined scale. As a deep learning network, the DS-UNet model performance is strongly dependent on many factors. We propose to focus on alternatives in its main architecture by designing a configurable Double-Step Framework, which allows inspecting the prediction quality with different loss-functions and convolutional neural networks used as backbones. Experimental results show that the proposed framework yields better performance with up to 6.1% lower RMSE than current state of the art

Hospitalizations for tuberculosis in Sicily over the years 2009–2021: Clinical features, comorbidities, and predictors of mortality

Background: Very few data are available in the literature regarding tuberculosis (TB) hospitalization, and few studies have reported the clinical characteristics and comorbidities of admitted patients and burden and cost of hospitalization. In our study, we described the occurrence of TB hospital admissions in the southern Italian region of Sicily over 13 years (2009–2021), explored the characteristics of patients with TB, and determined the comorbidities associated with mortality. Method: Data on the hospital discharge of all patients with TB hospitalized in all Sicilian hospitals were retrospectively collected from hospital standard discharge forms. Age, sex, nationality, length of hospital stay, comorbidities, and TB localization were evaluated using univariate analysis according to in-hospital mortality. The factors associated with mortality were included in the logistic regression model. Results: In Sicily, 3745 people were hospitalized for TB, with 5239 admissions and 166 deaths from 2009 to 2021. Most hospitalizations involved Italian-born people (46.3%), followed by African-born people (32.8%) and Eastern European-born people (14.1%). The average hospitalization cost was EUR 5259 ± 2592, with a median length of stay of 16 days (interquartile range, 8–30) days. Multivariate analysis showed that the development of acute kidney failure (adjusted odds ratio [aOR]=7.2, p < 0.001), alcohol consumption (aOR=8.9, p = 0.001), malignant tumors (aOR=2.1, p = 0.022), human immunodeficiency virus infection (aOR=3.4, p < 0.001), sepsis (aOR=15.2, p < 0.001), central nervous system involvement (aOR=9.9, p < 0.001), and miliary TB (aOR=2.5, p = 0.004) were independent predictors of mortality. Conclusion: TB in Sicily remains an important cause of hospitalization. HIV infection and comorbidities may complicate patient management and worsen patient outcomes

Attention to Fires: Multi-Channel Deep Learning Models for Wildfire Severity Prediction

Wildfires are one of the natural hazards that the European Union is actively monitoring through the Copernicus EMS Earth observation program which continuously releases public information related to such catastrophic events. Such occurrences are the cause of both short- and long-term damages. Thus, to limit their impact and plan the restoration process, a rapid intervention by authorities is needed, which can be enhanced by the use of satellite imagery and automatic burned area delineation methodologies, accelerating the response and the decision-making processes. In this context, we analyze the burned area severity estimation problem by exploiting a state-of-the-art deep learning framework. Experimental results compare different model architectures and loss functions on a very large real-world Sentinel2 satellite dataset. Furthermore, a novel multi-channel attention-based analysis is presented to uncover the prediction behaviour and provide model interpretability. A perturbation mechanism is applied to an attention-based DS-UNet to evaluate the contribution of different domain-driven groups of channels to the severity estimation problem