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Differential Privacy in Distributed Mobility Analytics
No full textMovement data are sensitive, because people’s whereabouts may allow re- identification of individuals in a de-identified database and thus can potentially reveal intimate personal traits, such as religious or sexual preferences. In this paper, we focus on a distributed setting in which movement data from individ- ual vehicles are collected and aggregated by a centralized station. We propose a novel approach to privacy-preserving analytical processing within such a dis- tributed setting, and tackle the problem of obtaining aggregated traffic information while preventing privacy leakage from data collection and aggregation. We study and analyze three different solutions based on the differential privacy model and on sketching techniques for efficient data compression. Each solution achieves different trade-off between privacy protection and utility of the transformed data. Using real-life data, we demonstrate the effectiveness of our approaches in terms of data utility preserved by the data transformation, thus bringing empirical evi- dence to the fact that the “privacy-by-design” paradigm in big data analytics has the potential of delivering high data protection combined with high quality even in massively distributed techno-social systems
A Tutorial on Train Timetabling and Train Platforming Problems
No full textIn this tutorial, we give an overview of two fundamental problems arising in the optimization of a railway system: the Train Timetabling
Problem (TTP) and the Train Platforming Problem (TPP). These problems correspond to two main phases that are usually optimized in close
sequence. First, in the TTP phase, a schedule of the trains in a railway network is determined. A schedule consists of the arrival and departure times of each train at each (visited) station. Second, in the TPP phase, one needs to determine a topping platform and a routing for each train inside each (visited) station, according to the schedule found in the TTP phase.
Due to the complexity of the two problems, an integrated approach is generally hopeless for real-world instances. Hence, the two
phases are considered separately and optimized in sequence. Although there exist several versions for both problems, depending on the infrastructure manager and train operators requirements, we do not aim at presenting all of them, but rather at introducing the reader to the topic using small examples. We present models and solution approaches for the two problems in a didactic way and always refer the reader to the corresponding articles for technical details
Distributed monitoring of cluster quality for car insurance customer segmentation
No full textCustomer segmentation is one of the most traditional and valued tasks in customer relationship management (CRM). In this paper, we explore the problem in the context of the car insurance industry, where the mobility behavior of customers plays a key role: different mobility needs, driving habits and skills imply also different requirements (level of coverage provided by the insurance) and risks (of accidents). In the present work, we describe a methodology to extract several indicators describing the driving profile of customers, and provide a clustering-oriented instantiation of the segmentation problem, based on such indicators. Then, we consider the availability of a continuous flow of fresh mobility data sent by the circulating vehicles, aiming at keeping our segments constantly up-to-date. We tackle a major scalability issue that emerges in this con- text when the number of customers is large, namely the communication bottleneck, by proposing and implementing a sophisticated distributed monitoring solution, which reduces the communications between vehicles and company servers to the essential. Finally, we validate the framework on a large database of real mobility data, coming from GPS devices of private cars
An iterative procedure for the Paretian ranking of competing projects
No full textIn this Technical Report we present an iterative procedure for the evaluation, from a set of decsion makers, of a set of projects according to a given set of criteria. The proposed procedure uses Pareto principles and a Borda classical voting method and aimsat attaining fair allocations whenever this is possible
The fractional Laplacian operator on bounded domains as a special case of the nonlocal diffusion operator
No full textWe analyze a nonlocal diffusion operator having as special cases the
fractional Laplacian and fractional differential operators that arise in
several applications. In our analysis, a nonlocal vector calculus is exploited
to define a weak formulation of the nonlocal problem. We demonstrate that, when
sufficient conditions on certain kernel functions hold, the solution of the
nonlocal equation converges to the solution of the fractional Laplacian
equation on bounded domains as the nonlocal interactions become infinite. We
also introduce a continuous Galerkin finite element discretization of the
nonlocal weak formulation and we derive a priori error estimates. Through
several numerical examples we illustrate the theoretical results and we show
that by solving the nonlocal problem it is possible to obtain accurate
approximations of the solutions of fractional differential equations
circumventing the problem of treating infinite-volume constraints
On the phase diagram of the 4D U(1) model at finite temperature
No full textWe explore the phase diagram of the 4D compact U(1) gauge theory at finite
temperature as a function of the gauge coupling and of the compactified
Euclidean time dimension L_t. We show that the strong-to-weak coupling
transition, which is first order at T=0 (L_t=\infty), becomes second order for
high temperatures, i.e. for small values of L_t, with a tricritical temporal
size \bar{L_t} located between 5 and 6. The critical behavior around the
tricritical point explains and reconciles previous contradictory evidences
found in the literature
New Confinement Phases from Singular SCFT
No full textNew types of confining phase emerge when some singular SCFT's appearing as
infrared fixed points of N=2 supersymmetric QCD (SQCD) are deformed by an N=1
adjoint mass term. We make further checks on the Gaiotto-Seiberg-Tachikawa
(GST) description of these vacua against the symmetry and vacuum counting
argument, and show that the GST variables correctly describe these systems,
brought into confinement phase by the N=1 perturbation. Several examples of
such vacua, USp(2N) and SU(N) theories with four flavors and SO(N) theories
with one or two flavors, are discussed
The Cohomologies of the Iwasawa Manifold and of Its Small Deformations
No full textWe prove that, for some classes of complex nilmanifolds, the Bott–Chern cohomology is completely determined by the Lie algebra associated with the nilmanifold with the induced complex structure. We use these tools to compute the Bott–Chern and Aeppli cohomologies of the Iwasawa manifold and of its small deformations, completing the computations by M. Schweitzer (arXiv:0709.3528v1 [math.AG])
Bott–Chern cohomology and q-complete domains
No full textIn studying the Bott–Chern and Aeppli cohomologies for q-complete manifolds, we introduce the class of cohomologically Bott–Chern q-complete manifolds
Java SAM Typed Closures: A Sound and Complete Type Inference System for Nominal Types (Extended Version)
No full textThe last proposal for Java closures, as emerged in JSR 000335, is mainly innovative in: (1)Use of nominal types, SAM types, for closures; (2) Introduction of target types and compatibility for a contextual typing of closures; (3) Need for a type inference that reconstructs the omitted type annotations of closures and closure arguments. The paper provides a sound and complete type system, with nominal types, for such a type inference and discusses role and formalization of targeting and of compatibility in the designed inference process