Random Forests and Networks Analysis

D. Wilson~\cite{[Wi]} in the 1990's described a simple and efficient algorithm based on loop-erased random walks to sample uniform spanning trees and more generally weighted trees or forests spanning a given graph. This algorithm provides a powerful tool in analyzing structures on networks and along this line of thinking, in recent works~\cite{AG1,AG2,ACGM1,ACGM2} we focused on applications of spanning rooted forests on finite graphs. The resulting main conclusions are reviewed in this paper by collecting related theorems, algorithms, heuristics and numerical experiments. A first foundational part on determinantal structures and efficient sampling procedures is followed by four main applications: 1) a random-walk-based notion of well-distributed points in a graph 2) how to describe metastable dynamics in finite settings by means of Markov intertwining dualities 3) coarse graining schemes for networks and associated processes 4) wavelets-like pyramidal algorithms for graph signals.Comment: Survey pape

HYBRID GIS-BIM APPROACH FOR THE TORINO DIGITAL-TWIN: THE IMPLEMENTATION OF A FLOOR-LEVEL 3D CITY GEODATABASE

Abstract. The research tries to present a preliminary work into geo-spatial management of public administration assets thanks to interoperability of BIM-GIS models, related to urban scale scenarios. The strategy proposed tries to deepen the management, conversion and integration of databases related to public assets and particularly schools building, and related them into city-related geo-databases. The methodology, based on the real scenario of Torino Municipality and their needs addressed in recent studies in collaboration with FULL – Future Urban Legacy Lab from Politecnico di Torino, take advantage from the availability of two test dataset at different scale, with different potential and bottlenecks. The idea of developing a 3D digital twin of Torino actually stop long before the 3D city modelling only, but rather we have to deal with the integration and harmonization of existing databases. These data collections are often coming from different updating and based on non-homogeneous languages and data models. The data are often in table format and managed by different offices and as many management systems. Moreover, recently public administrations as the one of Torino, have increase availability of BIM models, especially for public assets, which need to be known, archived, and localized in a geographic dimension in order to benefit from the real strategic potential of a spatial-enabled facility management platform as Digital Twin. Combining the use of parametric modeler software (Revit) and visual programming language (Dynamo), the proposed methodology tries to elaborate rules on a set of shared language parameters (characterizing the buildings as attributes in both datasets: ID; address; construction; floors; rooms dimensions, use, floor; height; glass surfaces). This is tested as conversion workflow between the Municipality DB and the BIM model. This solution firstly allows the interaction and query between models, and then it proposes open issues once the enriched BIM model is imported into the geographical dimension of the Torino 3D city model Digital Twin (ArcGIS Pro platform), according to LOD standards, and enriched with semantic components from municipality DB

Food addiction and psychosocial adversity: Biological embedding, contextual factors, and public health implications

The role of stress, trauma, and adversity particularly early in life has been identified as a contributing factor in both drug and food addictions. While links between traumatic stress and substance use disorders are well documented, the pathways to food addiction and obesity are less established. This review focuses on psychosocial and neurobiological factors that may increase risk for addiction-like behaviors and ultimately increase BMI over the lifespan. Early childhood and adolescent adversity can induce long-lasting alterations in the glucocorticoid and dopamine systems that lead to increased addiction vulnerability later in life. Allostatic load, the hypothalamic-pituitary-adrenal axis, and emerging data on epigenetics in the context of biological embedding are highlighted. A conceptual model for food addiction is proposed, which integrates data on the biological embedding of adversity as well as upstream psychological, social, and environmental factors. Dietary restraint as a feature of disordered eating is discussed as an important contextual factor related to food addiction. Discussion of various public health and policy considerations are based on the concept that improved knowledge of biopsychosocial mechanisms contributing to food addiction may decrease stigma associated with obesity and disordered eating behavior

Quantifying the network connectivity of landscape mosaics: a graph-theoretical approach

Connectivity determines a large number of ecological functions of the landscape, including seed and animal dispersal, gene flow and disturbance propagation, and is therefore a key to understanding fluxes of matter and energy within land mosaics. Several approaches to quantifying landscape connectivity are possible. Among these, graph theory may be used to represent a landscape as a series of interconnected patches, where flows occur as a result of structural and/or functional patch connectivity. Within this context, we propose the use of a graph-theoretic index (i.e., the Harary index) as a measure of landscape connectivity. Results derived from the analysis of the vegetation map of Palmarola (central Italy) show that, from a statistical and ecological viewpoint, the Harary index may be a better measure of landscape connectivity than more traditional indices derived from transportation geography

HBIM MODELLING FOR AN HISTORICAL URBAN CENTRE

Abstract. The research in the geospatial data structuring and formats interoperability direction is the crucial task for creating a 3D Geodatabase at the urban scale. Both geometric and semantic data structuring should be considered, mainly regarding the interoperability of objects and formats generated outside the geographical space. Current reflections on 3D database generation, based on geospatial data, are mostly related to visualisation issues and context-related application. The purposes and scale of representation according to LoDs require some reflections, particularly for the transmission of semantic information.This contribution adopts and develops the integration of some tools to derive object-oriented modelling in the HBIM environment, both at the urban and architectural scale, from point clouds obtained by UAV (Unmanned Aerial Vehicle) photogrammetry.One of the paper's objectives is retracing the analysis phases of the point clouds acquired by UAV photogrammetry technique and their suitability for multiscale modelling. Starting from UAV clouds, through the optimisation and segmentation, the proposed workflow tries to trigger the modelling of the objects according to the LODs, comparing the one coming from CityGML and the one in use in the BIM community. The experimentation proposed is focused on the case study of the city of Norcia, which like many other historic centres spread over the territory of central Italy, was deeply damaged by the 2016-17 earthquake

A semi-automated approach to model architectural elements in Scan-to-BIM processes

In the last years, the AEC (Architecture, Engineering and Construction) domain has exponentially increased the use of BIM and HBIM models for several applications, such as planning renovation and restoration, building maintenance, cost managing, or structural/energetic retrofit design. However, obtaining detailed as-built BIM models is a demanding and time-consuming process. Especially in historical contexts, many different and complex architectural elements need to be carefully and manually modelled. Meshes or surfaces and NURBS or polylines, derived from 3D reality-based data, are recently used as a reference for the HBIM accurate modelling. This work proposes a comprehensive and novel semi-automated approach to reconstruct architectural elements through the Visual Programming Language (VPL) Dynamo software and a Boundary-Representation method (B-rep), starting from 3D surveying data and point clouds classification. A wide package of scripts provides solutions for modelling complex shapes and transferring the obtained 3D models into BIM Authoring tools for a complete reconstruction phase. The presented procedure, useful for different BIM or HBIM applications, proved to reduce the modelling time significantly

Salty sensors, fresh ideas: The use of molecular and imaging sensors in understanding plankton dynamics across marine and freshwater ecosystems

Understanding plankton dynamics in marine ecosystems has been advanced using in situ molecular and imaging instrumentation. A range of research objectives have been addressed through high‐resolution autonomous sampling, from food web characterization to harmful algal bloom dynamics. When used together, molecular and imaging sensors can cover the full‐size range, genetic identity, and life stages of plankton. Here, we briefly review a selection of in situ instrumentation developed for the collection of molecular and imaging information on plankton communities in marine ecosystems. In addition, we interviewed a selection of instrumentation developers to determine if the transfer of sensor technology from marine to freshwater ecosystems is feasible and to describe the process of creating in situ sensors. Finally, we discuss the status of in situ molecular and imaging sensors in freshwater ecosystems and how some of the reviewed sensors could be used to address basic and applied research questions

Automatic Mapping of Atrial Fiber Orientations for Patient-Specific Modeling of Cardiac Electromechanics using Image-Registration

Knowledge of appropriate local fiber architecture is necessary to simulate patient-specific electromechanics in the human heart. However, it is not yet possible to reliably measure in-vivo fiber directions, especially in human atria. Thus, we present a method which defines the fiber architecture in arbitrarily shaped atria using image registration and reorientation methods based on atlas atria with fibers predefined from detailed histological observations. Thereby, it is possible to generate detailed fiber families in every new patient-specific geometry in an automated, time-efficient process. We demonstrate the good performance of the image registration and fiber definition on ten differently shaped human atria. Additionally, we show that characteristics of the electrophysiological activation pattern which appear in the atlas atria also appear in the patients' atria. We arrive at analogous conclusions for coupled electro-mechano-hemodynamical computations

Continuity and anomalous fluctuations in random walks in dynamic random environments: numerics, phase diagrams and conjectures

We perform simulations for one dimensional continuous-time random walks in two dynamic random environments with fast (independent spin-flips) and slow (simple symmetric exclusion) decay of space-time correlations, respectively. We focus on the asymptotic speeds and the scaling limits of such random walks. We observe different behaviors depending on the dynamics of the underlying random environment and the ratio between the jump rate of the random walk and the one of the environment. We compare our data with well known results for static random environment. We observe that the non-diffusive regime known so far only for the static case can occur in the dynamic setup too. Such anomalous fluctuations give rise to a new phase diagram. Further we discuss possible consequences for more general static and dynamic random environments.Comment: 33 pages, 23 figure