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In this paper, we present a framework for performing automatic analysis of Land Use Zones based on Location-Based Social Networks (LBSNs). We model city areas using a hierarchical structure of POIs extracted from foursquare. We encode such structures in kernel machines, e.g., Support Vector Machines, using a new Tree Kernel, i.e., the Hierarchical POI Kernel (HPK), which can take the importance of the individual POIs into account during the substructure matching. This way, HPK projects structures in the space of all their possible substructures such that each dimension corresponds to a semantic structural feature, weighted according to the discriminative power of POIs. We generated four different datasets for the following cities: Barcelona, Lisbon, Amsterdam and Milan, where we trained and tested our models. The results show that our approach largely outperforms previous work and standard baseline built on simple features, such as counts of different POIs. Finally, we apply a mining algorithm to extract the most relevant features (tree fragments) from the implicit TK space according to the weights the kernel machine assigned to them. Our approach can produce an explicit set of representative features that can be used to classify and characterize urban areas. [ABSTRACT FROM AUTHOR]

A simple yet effective time diversity model, referred to as Time Diversity Stratiform Convective EXCELL (TD-SCEX), is presented. The model, conceived to support the design of EHF Earth–space communication systems implementing Fade Mitigation Techniques, takes advantage of the Stratiform Convective EXponential CELL (SC EXCELL) model to predict the joint rain attenuation statistics and, hence, the time diversity gain, starting from the geometrical and electrical characteristics of the link, as well as from the joint rain rate statistics. The model performance is evaluated against the data collected in Milan, Madrid, and Spino d’Adda at Ka-, $Q$ -, and $V$ -bands in the framework of different long-term propagation campaigns. Results indicate that TD-SCEX is a useful tool to predict the effectiveness of time diversity in improving the performance of EHF Earth–space communication systems. [ABSTRACT FROM AUTHOR]