Search results for "Graph theory"
showing 10 items of 784 documents
Graph Comparison and Artificial Models for Simulating Real Criminal Networks
2021
Network Science is an active research field, with numerous applications in areas like computer science, economics, or sociology. Criminal networks, in particular, possess specific topologies which allow them to exhibit strong resilience to disruption. Starting from a dataset related to meetings between members of a Mafia organization which operated in Sicily during 2000s, we here aim to create artificial models with similar properties. To this end, we use specific tools of Social Network Analysis, including network models (Barabási-Albert identified to be the most promising) and metrics which allow us to quantify the similarity between two networks. To the best of our knowledge, the DeltaCo…
Graph-based minimal path tracking in the skeleton of the retinal vascular network
2012
This paper presents a semi-automatic framework for minimal path tracking in the skeleton of the retinal vascular network. The method is based on the graph structure of the vessel network. The vascular network is represented based on the skeleton of the available segmented vessels and using an undirected graph. Significant points on the skeleton are considered nodes of the graph, while the edge of the graph is represented by the vessel segment linking two neighboring nodes. The graph is represented then in the form of a connectivity matrix, using a novel method for defining vertex connectivity. Dijkstra and Floyd-Warshall algorithms are applied for detection of minimal paths within the graph…
Analysis of Load Match in Nearly Zero Energy Buildings
2018
The concept of load matching refers to the degree of agreement or disagreement of the on-site generation with the building load profiles: it can be increased and optimised with modifications on both the energy demand and generation. In this context, the paper presents the load match analysis of a case study: a modular housing construction (it has an area of 45 m 2 and S/V ratio equal to 2.75 m −1 ) built in Messina (Italy). Moreover, in order to optimize the design of the next test module to be built, a parametric analysis was performed considering different scenarios on the generation side, to explore the effectiveness of the solutions sets used in current design and plan different solutio…
The quest for bandwidth estimation techniques for large-scale distributed systems
2010
In recent years the research community has developed many techniques to estimate the end-to-end available bandwidth of an Internet path. This important metric can be potentially exploited to optimize the performance of several distributed systems and, even, to improve the effectiveness of the congestion control mechanism of TCP. Thus, it has been suggested that some existing estimation techniques could be used for this purpose. However, existing tools were not designed for large-scale deployments and were mostly validated in controlled settings, considering only one measurement running at a time. In this paper, we argue that current tools, while offering good estimates when used alone, migh…
An Intelligent Car Driver for safe Navigation with Fuzzy Obstacle Avoidance.
2009
In order to respond effectively to the environment uncertainties, autonomous vehicles are generally equipped with sensors. The proposed car guidance system is equipped with an intelligent controller, based on fuzzy logic, which calculates the speed and wheels orientation in order to follow a path while it is avoiding unknown obstacles. Better fluidity of driving are obtained using future-path, car dimension and car position prevision. Vehicle symmetries also speed-up and simplify the guidance system reducing the inputs and the rules numbers.
Using Temporal Texture for Content-Based Video Retrieval
2000
Textures evolving over time are called temporal textures and are very common in everyday life. Examples are the smoke flowing or the wavy water of a river. The idea explored in this paper is that image features based on temporal texture could allow a better performance of current content-based video retrieval systems that are mainly based on static characteristics of representative frames, like color and texture. To this aim we analyze the spatio-temporal nature of texture and its application in content-based access to video databases. In particular, we represent temporal texture using the spatio-temporal autoregressive (STAR) model and a variation of self-organizing maps (SOM) where each n…
Path Modeling and Retrieval in Distributed Video Surveillance Databases
2012
We propose a framework for querying a distributed database of video surveillance data in order to retrieve a set of likely paths of a person moving in the area under surveillance. In our framework, each camera of the surveillance system locally pro- cesses the data and stores video sequences in a storage unit and the metadata for each detected person in the distributed database. A pedestrian’s path is formulated as a dynamic Bayesian network (DBN) to model the dependencies between subsequent observa- tions of the person as he makes his way through the camera net- work. We propose a tool by which the analyst can pose queries about where a certain person appeared while moving in the site duri…
An Original Convolution Model to analyze Graph Network Distribution Features
2022
Modern Graph Theory is a newly emerging field that involves all of those approaches that study graphs differently from Classic Graph Theory. The main difference between Classic and Modern Graph Theory regards the analysis and the use of graph's structures (micro/macro). The former aims to solve tasks hosted on graph nodes, most of the time with no insight into the global graph structure, the latter aims to analyze and discover the most salient features characterizing a whole network of each graph, like degree distributions, hubs, clustering coefficient and network motifs. The activities carried out during the PhD period concerned, after a careful preliminary study on the applications of the…
Which regions produce the most innovation policy research?
2022
[EN] This article uses the data indexed in the Web of Science Core Collection and Scopus databases up to and including the year 2020 to map leading regions and trending topics in academic innovation policy research. The country analysis highlights four leading regions in this research field: Western Europe (led by the UK, the Netherlands, Germany, and Spain), North America (led by the USA), Scandinavia (led by Sweden and Denmark), and Asia-Pacific (led by China and Australia). The most common keywords are used to develop a conceptual framework. Applying the Tree of Science approach, we classify the most influential studies into three categories: foundational studies (the roots), structural …
Random Feature Approximation for Online Nonlinear Graph Topology Identification
2021
Online topology estimation of graph-connected time series is challenging, especially since the causal dependencies in many real-world networks are nonlinear. In this paper, we propose a kernel-based algorithm for graph topology estimation. The algorithm uses a Fourier-based Random feature approximation to tackle the curse of dimensionality associated with the kernel representations. Exploiting the fact that the real-world networks often exhibit sparse topologies, we propose a group lasso based optimization framework, which is solve using an iterative composite objective mirror descent method, yielding an online algorithm with fixed computational complexity per iteration. The experiments con…