A stigmergy-based analysis of city hotspots to discover trends and anomalies in urban transportation usage

A key aspect of a sustainable urban transportation system is the effectiveness of transportation policies. To be effective, a policy has to consider a broad range of elements, such as pollution emission, traffic flow, and human mobility. Due to the complexity and variability of these elements in the urban area, to produce effective policies remains a very challenging task. With the introduction of the smart city paradigm, a widely available amount of data can be generated in the urban spaces. Such data can be a fundamental source of knowledge to improve policies because they can reflect the sustainability issues underlying the city. In this context, we propose an approach to exploit urban positioning data based on stigmergy, a bio-inspired mechanism providing scalar and temporal aggregation of samples. By employing stigmergy, samples in proximity with each other are aggregated into a functional structure called trail. The trail summarizes relevant dynamics in data and allows matching them, providing a measure of their similarity. Moreover, this mechanism can be specialized to unfold specific dynamics. Specifically, we identify high-density urban areas (i.e hotspots), analyze their activity over time, and unfold anomalies. Moreover, by matching activity patterns, a continuous measure of the dissimilarity with respect to the typical activity pattern is provided. This measure can be used by policy makers to evaluate the effect of policies and change them dynamically. As a case study, we analyze taxi trip data gathered in Manhattan from 2013 to 2015.Comment: Preprin

Space efficient merging of de Bruijn graphs and Wheeler graphs

The merging of succinct data structures is a well established technique for the space efficient construction of large succinct indexes. In the first part of the paper we propose a new algorithm for merging succinct representations of de Bruijn graphs. Our algorithm has the same asymptotic cost of the state of the art algorithm for the same problem but it uses less than half of its working space. A novel important feature of our algorithm, not found in any of the existing tools, is that it can compute the Variable Order succinct representation of the union graph within the same asymptotic time/space bounds. In the second part of the paper we consider the more general problem of merging succinct representations of Wheeler graphs, a recently introduced graph family which includes as special cases de Bruijn graphs and many other known succinct indexes based on the BWT or one of its variants. We show that Wheeler graphs merging is in general a much more difficult problem, and we provide a space efficient algorithm for the slightly simplified problem of determining whether the union graph has an ordering that satisfies the Wheeler conditions.Comment: 24 pages, 10 figures. arXiv admin note: text overlap with arXiv:1902.0288

Stigmergy-based modeling to discover urban activity patterns from positioning data

Positioning data offer a remarkable source of information to analyze crowds urban dynamics. However, discovering urban activity patterns from the emergent behavior of crowds involves complex system modeling. An alternative approach is to adopt computational techniques belonging to the emergent paradigm, which enables self-organization of data and allows adaptive analysis. Specifically, our approach is based on stigmergy. By using stigmergy each sample position is associated with a digital pheromone deposit, which progressively evaporates and aggregates with other deposits according to their spatiotemporal proximity. Based on this principle, we exploit positioning data to identify high density areas (hotspots) and characterize their activity over time. This characterization allows the comparison of dynamics occurring in different days, providing a similarity measure exploitable by clustering techniques. Thus, we cluster days according to their activity behavior, discovering unexpected urban activity patterns. As a case study, we analyze taxi traces in New York City during 2015

Image acquisition system for the Italian panoramic monochromator of the THEMIS telescope

We describe the image acquisition system of the italian panoramic monochromator which will be in operation at the focus F2 of the THEMIS solar telescope to acquire images of the Sun in the visible spectrum (between 420 and 700 nm) with a spectral resolving power of about 300 000. The system consists of two CCD cameras (using either 512-512 or 1024- 1024 square-pixel sensors) controlled and readout by dedicated electronics and a personal computer. The data transmission between the sensors and the computer is performed by means of an optical link

IBIS (Interferometric BIdimensional spectrometer)

IBIS is a new instrument for solar bidimensional spectroscopy, now under construction at the Arcetri Astrophysical Observatory. It essentially consists of two Fabry-Perot interferometers, piezo-scanned and capacity servo-controlled, which are used in classic mount and in axial-mode, in series with a narrow-band interference filter. This instrument will operate on a large field of view (80����) and on a large wavelength range (5800–8600 ˚A), with high spectral (λ/Δλ � 250000), spatial (�0.2) and temporal (� 5 frames s−1) resolution. When completed in 2002, it will be one of the leading instruments for solar research, well suited for a new generation telescopes such as THEMIS

An efficient and robust procedure to calculate absorption spectra of aqueous charged species applied to NO2−

Accurate calculation of absorption spectra of aqueous NO2−requires rigorously sampling the quantum potential energy surfaces for microsolvation of NO2−with at least five explicit water molecules and embedding the resulting clusters in a continuum solvent accounting for the statistical weighted contributions of individual isomers. This method, which we address as ASCEC + PCM, introduces several desired features when compared against MD simulations derived QM/MM spectra: comparatively fewer explicit solvent molecules to be treated with expensive QM methods, the identification of equilibrium structures in the quantum PES to be used in further vibrational spectroscopy, and the unequivocal identification of cluster orbitals undergoing electronic transitions and charge transfer that originate the spectral bands

External memory BWT and LCP computation for sequence collections with applications

We propose an external memory algorithm for the computation of the BWT and LCP array for a collection of sequences. Our algorithm takes the amount of available memory as an input parameter, and tries to make the best use of it by splitting the input collection into subcollections sufficiently small that it can compute their BWT in RAM using an optimal linear time algorithm. Next, it merges the partial BWTs in external memory and in the process it also computes the LCP values. We show that our algorithm performs O(n maxlcp) sequential I/Os, where n is the total length of the collection and maxlcp is the maximum LCP value. The experimental results show that our algorithm outperforms the current best algorithm for collections of sequences with different lengths and when the average LCP of the collection is relatively small compared to the length of the sequences. In the second part of the paper, we show that our algorithm can be modified to output two additional arrays that, combined with the BWT and LCP arrays, provide simple, scan based, external memory algorithms for three well known problems in bioinformatics: the computation of the all pairs suffix-prefix overlaps, the computation of maximal repeats, and the construction of succinct de Bruijn graphs

Industrial sprawl and residential housing. Exploring the interplay between local development and land-use change in the Valencian Community, Spain

Urbanization in Mediterranean Europe has occurred in recent decades with expansion of residential, commercial and industrial settlements into rural landscapes outside the traditional metropolitan boundaries. Industrial expansion in peri-urban contexts was particularly intense in Southern Europe. Based on these premises, this work investigates residential and industrial settlement dynamics in the Valencian Community, Spain, between 2005 and 2015, with the aim to clarify the role of industrial expansion in total urban growth in a paradigmatic Mediterranean region. Since the early 1990s, the Valencian industrial sector developed in correspondence with already established industrial nodes, altering the surrounding rural landscape. Six variables (urban hierarchy, discontinuous settlements, pristine land under urban expansion, isolated industrial settlements, within- and out-of-plan industrial areas) were considered with the aim at exploring land-use change. Empirical results indicate a role of industrial development in pushing urban sprawl in coastal Valencia. A reflection on the distinctive evolution of residential and industrial settlements is essential for designing new planning measures for sustainable land management and containment of urban sprawl in Southern Europe. A comparative analysis of different alternatives of urban development based on quantitative assessment of land-use change provides guidelines for local development and ecological sustainability

Risultati del trattamento chirurgico del varicocele nella infertilità maschile

To evaluate the results of surgical treatment of varicocele on infertile men, especially regarding sperm count, 245 patients, surgically treated from 1993 to 2003, were evaluated. Patients underwent to ligature and section of the pampiniform plexus, throught the subinguinal approach and local anaesthesia. At the follow-up (3-6-12 months) an improvement of sperm count was relieved in 79.5% of patients and the incidence of complications and relapses was of 3.7% and 1.2%, respectively. The Authors stress the efficacy of surgical treatment of varicocele in male infertility and hold the subinguinal approach as an effective treatment, minimally invasive and low cost