@article {irs17-12, title = {Analysis of a multi-ring technique for 3D pattern recognition}, number = {17-12}, year = {2017}, month = {June}, pages = {20 p.}, publisher = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

Pattern characterization of geometric features is of great interest in the cultural heritage domain, as the style of the some parts such beards, hairs, helms or cuirass decorations would support and enhance the classification and/or cataloguing of the archaeological artefacts and fragments. In this context, a pattern is a geometric or colour feature which is repeated over a surface, either on its entirety or on a part (for instance, engravings and chisellings, ornamental decorations, etc.). In the literature, methods that face this problem either project the surface into an image and then adopt a image pattern recognition techniques or try to extend in 3D an existing image technique to surfaces. In this paper, we analyse the performance of the technique called mesh Local Binary Pattern (meshLBP) that works on triangulation meshes, considering implementation defined in [WTBdB15, WBdB15] and freely available. Tests are performed on meshes of the repository at STARC - The Cyprus Institute [STA] that correspond to laser scans of earthenware fragments retrieved from the Salamina Island. Fragments are represented with triangulations, not necessarily uniformly sampled. In this paper we analyse two kind of patterns represented by geometric and colorimetric variations on the surface of the fragment. In addition, we discuss a sub-sample strategy to keep the effectiveness of the meshLBP descriptor and the dependence of the operator on parameters such as the surface representation and the number of rings used for its multi-scale evaluation. Finally, the main limitations of the method are discussed and possible improvements and future developments are outlined.

}, keywords = {3D pattern analysis, 3D pattern classification, mesh}, url = {http://irs.imati.cnr.it/reports/irs17-12}, author = {E. Moscoso Thompson and S. Biasotti} } @article {irs17-01, title = {BPX preconditioners for isogeometric analysis using analysis-suitable T-splines}, number = {17-01}, year = {2017}, month = {January}, pages = {32 p.}, publisher = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

We propose and analyze optimal additive multilevel solvers for isogeometric discretizations of scalar elliptic problems for locally refined T-meshes. Applying the refinement strategy in Morgenstern and Peterseim, Comput. Aided Geom. Design, 34 (2015), we can guarantee that the obtained T-meshes are p-admissible, which implies that the associated T-splines are analysis suitable. Taking advantage of the multilevel structure of p-admissible T-meshes, we develop a BPX preconditioner on the basis of local smoothing only for the functions affected by a newly added edge by bisection, and prove that our method has optimal complexity. Several numerical experiments confirm our theoretical result and also show the practical performance of the proposed preconditioner.

}, keywords = {T-splines}, doi = {https://doi.org/10.1093/imanum/dry032}, url = {http://irs.imati.cnr.it/reports/irs17-01}, author = {D. Cho and R. V{\'a}zquez} } @article {ipa|Initial-boundary value problems for nearly incompressible vector fields, and applications to the Keyfitz and Kranzer system|2017, title = {Initial-boundary value problems for nearly incompressible vector fields, and applications to the Keyfitz and Kranzer system}, year = {2017}, month = {January}, pages = {19 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

We establish existence and uniqueness results for initial boundary value problems with nearly incompressible vector fields. We then apply our results to establish well-posedness of the initial-boundary value problem for the Keyfitz and Kranzer system of conservation laws in several space dimensions.

}, keywords = {Systems of conservation laws}, url = {http://irs.imati.cnr.it/reports/irs17-02}, author = {A.P. Choudhury and G. Crippa and L.V. Spinolo} } @article {irs17-04, title = {Optimality of integrability estimates for advection-diffusion equations}, number = {17-04}, year = {2017}, month = {February}, pages = {19}, publisher = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

We discuss integrability estimates for the solution of an advection-diffusion equation. We first summarize some classical results proving such estimates for certain ranges of the space and time summability of the velocity field. Afterwards we prove the optimality of such ranges by means of new original examples.

}, keywords = {Advection-diffusion equation, Duhamel formula, integrability estimates and their optimality, parabolic equations, self-similar solutions}, url = {http://irs.imati.cnr.it/reports/irs17-04}, author = {S. Bianchini and M. Colombo and G. Crippa and L.V. Spinolo} } @article {ipa|Quantitative estimates on localised finite differences for the fractional Poisson problem, and applications to regularity and spectral stability|2017, title = {Quantitative estimates on localised finite differences for the fractional Poisson problem, and applications to regularity and spectral stability}, year = {2017}, month = {January}, pages = {38 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

We establish new quantitative estimates for localized finite differences of solutions to the Poisson problem for the fractional Laplace operator with homogeneous Dirichlet conditions of solid type settled in bounded domains satisfying the Lipschitz cone regularity condition. We then apply these estimates to obtain (i) regularity results for solutions of fractional Poisson problems in Besov spaces; (ii) quantitative stability estimates for solutions of fractional Poisson problems with respect to domain perturbations; (iii) quantitative stability estimates for eigenvalues and eigenfunctions of fractional Laplace operators with respect to domain perturbations.

}, keywords = {Spectral stability}, url = {http://irs.imati.cnr.it/reports/irs17-03}, author = {G. Akagi and G. Schimperna and A. Segatti and L.V. Spinolo} } @article {irs17-07, title = {VVS medical workflows: Definition of a static workflow for part-based annotation of wrist bones and web service oriented architecture for executable workflows}, number = {17-07}, year = {2017}, month = {March}, pages = {41 p.}, publisher = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

The report describes the extension of the Digital Shape Workbench version 5 (DSW5) for the inclusion of workflows for the analysis and processing of 3D models obtained from medical imaging data. The VVS Workflow Repository (WR) manages the creation, visualization and execution of shape processing workflows. The considered workflows are of two main categories: static and executable. The first category refers a kind of tutorial workflow/pipeline and is used for sharing expert knowledge e.g. for explaining the steps needed when dealing with a specific process. The second one represents chain of executable web services performing specific pipelines of geometric processing functions. The document describes the adopted architecture and structure for their specification and execution.

}, keywords = {On-line repositories, Semantic web, Shape processing}, url = {http://archives.imati.cnr.it/reports/irs17-07}, author = {F. Giannini and M. Pitikakis} } @article {ipa|Algorithms for the implementation of adaptive isogeometric methods using hierarchical splines|2016, title = {Algorithms for the implementation of adaptive isogeometric methods using hierarchical splines}, year = {2016}, month = {July}, pages = {37 p.}, institution = {CNR-IMATI}, type = {Working paper}, chapter = {1}, address = {Pavia}, abstract = {

In this article we introduce all the ingredients to develop adaptive isogeometric methods based on hierarchical splines. In particular, we give precise definitions of local refinement and coarsening that, unlike previously existing methods, can be understood as the inverse of each other. We also define simple and intuitive data structures for the implementation of hierarchical splines, and algorithms for refinement and coarsening that take advantage of local information. We complete the paper with some simple numerical tests to show the performance of the data structures and algorithms, that have been implemented in the opensource Octave/Matlab code GeoPDEs.

}, keywords = {Local refinement}, url = {http://irs.imati.cnr.it/reports/algorithms-implementation-adaptive-isogeometric-methods-using-hierarchical-splines}, author = {E.M. Garau and R. V{\'a}zquez} } @article {ipa|An appointment scheduling framework to balance the production of blood bags from donation|2016, title = {An appointment scheduling framework to balance the production of blood bags from donation}, year = {2016}, month = {June}, pages = {37 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Milano}, abstract = {

Blood is fundamental in several care treatments and surgeries, and plays a crucial role in the health care system. It is a limited resource, as it can be produced only by donors and its shelf life is short; thus, the blood donation (BD) system aims at providing adequate supply of blood bags to transfusion centers and hospitals. An effective collection of blood bags from donors is fundamental for adequately feeding the entire BD system and optimizing blood usage. However, despite its relevance, donation scheduling is only marginally addressed in the literature. In this paper we consider the Blood Donation Appointment Scheduling (BDAS) problem, aiming at balancing the production of the different blood types among days in order to provide a quite constant feeding of blood bags to the BD system. We propose a framework for the appointment reservation that accounts for both booked donors and donors arriving without a reservation. It consists of an offline Mixed Integer Linear Programming (MILP) model for preallocating time slots to blood types, and of an online prioritization policy to assign a preallocated slot when the donor calls to make the reservation.

}, keywords = {Production balancing}, url = {http://irs.imati.cnr.it/reports/irs16-06}, author = {S. Ba{\c s} and G. Carello and E. Lanzarone and S. Yal{\c c}inda{\u g}} } @article {ipa|Calcolo di descrittori ibridi geometria-colore per l{\textquoteright}analisi di similarit{\`a} di forme 3D|2016, title = {Calcolo di descrittori ibridi geometria-colore per l{\textquoteright}analisi di similarit{\`a} di forme 3D}, year = {2016}, month = {June}, pages = {24 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

Il riconoscimento e la classificazione di forme geometriche hanno molteplici applicazioni in grafica computazionale, spaziando dallo sviluppo di search engine all{\textquoteright}identificazione di anomalie in modelli medicali orientati al paziente, al design di nuovi farmaci e alla sperimentazione in silico. In tutti questi contesti, il confronto tra forme viene tradotto nel confronto tra descrizioni dell{\textquoteright}oggetto. {\`E} quindi di fondamentale importanza che una buona descrizione dell{\textquoteright}oggetto sia quanto pi{\`u} possibile completa, per risultare univoca, e allo stesso tempo concisa, per poter essere facilmente computabile e confrontabile con altre descrizioni. Inoltre, la descrizione geometrica di un oggetto 3D pu{\`o} essere corredata da informazioni colorimetriche, eventuali annotazioni e/o dati derivanti dalla sua acquisizione/provenienza. Nell{\textquoteright}ambito generale del confronto di forme 3D, in questo lavoro si analizza un metodo che utilizza propriet{\`a} geometriche e colorimetriche. Rispetto alla implementazione presente nella letteratura, si studia una ottimizzazione del metodo volta a diminuirne la complessit{\`a} computazionale e di memoria, e si discutono possibili strategie per un futuro miglioramento.

}, keywords = {Hybrid geometry-colour shape description}, url = {http://irs.imati.cnr.it/reports/irs16-05}, author = {S. Biasotti and A. Raffo} } @article {ipa|Comparing methods for the approximation of rainfall fields in environmental applications|2016, title = {Comparing methods for the approximation of rainfall fields in environmental applications}, year = {2016}, month = {February}, pages = {26 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

Digital environmental data are becoming commonplace and the amount of information they provide is huge, yet complex to process, due to the size, variety, and dynamic nature of the data captured by sensing devices. The paper discusses an evaluation framework for comparing methods to approximate observed rain data, in real conditions of sparsity of the observations. The novelty brought by this experimental study stands in the geographical area and heterogeneity of the data used for evaluation, aspects which challenge all approximation methods. The Liguria region, located in the north-west of Italy, is a complex area for the orography and the closeness to the sea, which cause complex hydro-meteorological events. The observed rain data are highly heterogeneous: two data sets come from measured rain gathered from two different rain gauge networks, with different characteristics and spatial distribution over the Liguria region; the third data set come from weather radar, with a more regular coverage of the same region but a different veracity. Finally, another novelty of the paper is brought by the proposal of an application-oriented perspective on the comparison. The approximation models the rain field, whose maxima and their evolution is essential for an effective monitoring of meteorological events. Therefore, we adapt a storm tracking technique to the analysis of the displacement of maxima computed by the different methods.

}, keywords = {Surface approximation}, url = {http://irs.imati.cnr.it/reports/irs16-10}, author = {G. Patan{\'e} and A. Cerri and V. Skytt and S. Pittaluga and S. Biasotti and D. Sobrero and T. Dokken and M. Spagnuolo} } @article {ipa|Conceptual design of shapes in Virtual Environments through the re-use of heterogeneous data|2016, title = {Conceptual design of shapes in Virtual Environments through the re-use of heterogeneous data}, year = {2016}, month = {November}, pages = {23 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

Today, digital data such as 2D images, 3D meshes and 3D point clouds are widely used to design Virtual Environments (VE). Most of the time, only one type of those multimodal data is used to describe and specify the shapes of the objects. However, a single object can be seen as a combination of components linked with constraints specifying the relationships and the rigid transformations defining their arrangement. Thus, the definition of news methods able to combine any kind of multimodal data in an easy way would allow nonexperts of VE to rapidly mock-up objects and scenes. In this paper, we propose a new shape description model together with its associated constraints toolbox enabling the description of complex shapes from multimodal data. Not only rigid transformations are considered but also scale modifications according to the specified context of the constraint setting. The heterogeneous virtual objects (i.e. composed by scalable multimodal components) then result from the resolution of a constraint satisfaction problem through an optimization approach. The proposed approach is illustrated with examples obtained with our prototype software.

}, keywords = {Virtual Reality}, url = {http://irs.imati.cnr.it/reports/irs16-17}, author = {J-P. Pernot and B. Falcidieno and F. Giannini and Z. Li and P. V{\'e}ron} } @article {ipa|Defect detection in nanostructures|2016, title = {Defect detection in nanostructures}, year = {2016}, month = {April}, pages = {18 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Milano}, abstract = {

Nanoproducts represent a potential growing sector and nano brous materials are widely requested in industrial, medical and environmental applications. Unfortunately, the production processes at the nanoscale are difficult to control, and produced artifacts often exhibit local defects that prevent their functional properties. We present a fully-automated solution to detect defects in nano brous materials during their production, yielding smart-manufacturing systems that reduce quality-inspection times and wastes. We analyze SEM images of nano brous materials and learn, during an initial training phase, a model yielding sparse representations of the structures that characterize correctly produced nano bers. Defects are then detected by analyzing patches in test images and assessing the goodness-of- t of each patch to the learned model. The proposed solution has been successfully validated over 45 images acquired from samples produced by a prototype electrospinning machine. The low computational times indicate that the proposed solution can be adopted for real-time monitoring in an industrial-production scenario.

}, keywords = {Sparse representations}, url = {http://irs.imati.cnr.it/reports/irs16-03}, author = {F. Manganini and D. Carrera and G. Boracchi and E. Lanzarone} } @article {ipa|Feature curve identification in archaeological fragments using an extension of the Hough transform|2016, title = {Feature curve identification in archaeological fragments using an extension of the Hough transform}, year = {2016}, month = {July}, pages = {19 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

The use of computer graphics techniques in cultural heritage (CH) has led to impressive improvements in technologies related to digital acquisition and rendering of 3D CH data. Digitized artefacts are becoming widely available for access and reuse, thus increasing the need of tools able to support comparative shape analysis. As 3D artefacts are often worn, eroded and broken, these tools cannot take advantage of existing methods based on exact matching but they rather require new approaches able to identify partial features in portions of models thus leading to a double partiality of the matching problem, in terms of both features and models In this context, we propose a method based on a novel generalization of the Hough transform technique able to identify and localize semantic features like anatomical features, ornaments, or decorations on digital artefacts or fragments, even if the features are partially damaged or incomplete. The major advantages of using a method based on the Hough transform technique are the relative robustness to noise and the recognition power also in the case of partial features. Our experiments on digital models of real artefacts are encouraging and show the potential of the method, which can work on both 3D meshes and point clouds.

}, keywords = {Hough transform}, url = {http://irs.imati.cnr.it/reports/irs16-09}, author = {ML. Torrente and S. Biasotti and B. Falcidieno} } @article {ipa|From lesson learned to the refactoring of the DRIHM science gateway for hydro-meteorological research|2016, title = {From lesson learned to the refactoring of the DRIHM science gateway for hydro-meteorological research}, year = {2016}, month = {March}, pages = {24 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

A full hydro-meteorological (HM) simulation, from rainfall to impact on urban areas, is a multidisciplinary activity which consists in the execution of a workflow composed by complex and heterogeneous model engines. Moreover an extensive set of configuration parameters have to be selected consistently among the models, otherwise the simulation can fail or produce unreliable results. The DRIHM portal is a Web-based science gateway aiming to support HM researchers in designing, executing and managing HM simulations. The first version of the portal was developed during the DRIHM project using the gUSE science gateway toolkit. The lesson we learned is guiding a refactoring process that, together with a review of the most relevant technologies for the development of a science gateway, represent the focus of this paper. Beside the technological aspects, the need of a strong interplay between ICT and other domain-specific communities clearly emerged, together with coherent policies in the management of data, computational resources and software components that represent the ecosystem of a science gateways.

}, keywords = {Science gateways}, url = {http://irs.imati.cnr.it/reports/irs16-07}, author = {D. D{\textquoteright}Agostino and G. Zereik and E. Danovaro and L. Roverelli and A. Clematis and A. Galizia} } @article {ipa|Identification of patterns of repeated parts in solid objects|2016, title = {Identification of patterns of repeated parts in solid objects}, year = {2016}, month = {November}, pages = {128 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

The feature-based modeling approach for designing a mechanical component has been widely adopted by most CAD modelers to maintain the design intent on models. A set of higher level information is requested to enrich the usual geometrical and topological data, in terms of feature information. A well known example of semantically significant data of this type is represented by the knowledge of the existence of symmetrical arrangements of repeated subparts in CAD models. Because of the information transferring, repeated modifications of the models and different tolerances used by the various CAD systems, these specific data can be lost. In this report, after having provided the necessary mathematical background and the state of art of the existing symmetry detection methods, we propose an approach for retrieving symmetries involving a set of user-selected sub-parts in a given BRep part model. The approach is based on a preliminary analysis of the position of points (centroids), each of them representing one repeated feature; a further examination on the faces of the sub-parts is performed to confirm the existence of symmetric arrangements. We have provided the description for the detection of linear translational, reflectional, and circular translational patterns of repeated sub-parts.

}, keywords = {shape analysis}, url = {http://irs.imati.cnr.it/reports/irs16-14}, author = {L. Chiang and F. Giannini and M. Monti} } @article {ipa|Identification of patterns of repeated parts in solid objects - Part II|2016, title = {Identification of patterns of repeated parts in solid objects - Part II}, year = {2016}, month = {November}, pages = {54 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

The work described in this report extends the methods described in the report "Identification of Patterns of Repeated Parts in Solid Objects" ([2]) to deal with CAD assemblies and to the detection of additional types of patterns. Specifically rotational and compound patterns of repeated elements are treated. Therefore, references of all notations, definitions and terms of the objects cited in this report can be found in [2]. The Chapter 1 describes the proposed approach to detect rotational patterns of repeated entities in part model, extending the set of types of patterns considered in [1], [2]. Chapter 2 contains the method proposed for assembly models for the detection of symmetric arrangements on components, considering as repeated elements of the patterns the instances of a part or assembly file. Chapter 3 is dedicated to the introduction of the concept of compound pattern, intended as an improvement of the quality of the symmetry information of a model, obtained by combining the information referred to the patterns of repeated elements. The approach has been described and provided either for part and assembly models.

}, keywords = {shape analysis}, url = {http://irs.imati.cnr.it/reports/irs16-15}, author = {L. Chiang and F. Giannini and M. Monti} } @article {ipa|Mapping aesthetic properties to 3D free form shapes through the use of a machine learning based framework|2016, title = {Mapping aesthetic properties to 3D free form shapes through the use of a machine learning based framework}, year = {2016}, month = {November}, pages = {27 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

Current production is moving from the mass production concept to the product customization and personalization. Customers are not anymore only buyers. Not only they are becoming actors within the Product Development Process (PDP) but, thanks to new production technologies like 3D printers, they can be both designers and producers. In this scenario, the development of user-friendly design tools is crucial. Declarative approaches are suitable and can address such requirements. They exploit generally understood and shared concepts closer to the way people perceive shapes than to the way shapes are modeled with complex geometric models. To this aim, this paper presents a generic framework for understanding the shape characteristics associated to perceptual/aesthetic properties of 3D free form shapes. This framework is used to investigate whether there is a common judgment to characterize the flatness of surfaces and which are the surface shape characteristics affecting the flatness perception? From the experiments, it results that the size and transition of the surrounding influence the perception of the flatness of a given surface strengthening the classification consistency.

}, keywords = {Machine Learning Application}, url = {http://irs.imati.cnr.it/reports/irs16-16}, author = {A. Petrov and J-P. Pernot and F. Giannini and B. Falcidieno} } @article {ipa|A new design for the implementation of isogeometric analysis in Octave and Matlab: GeoPDEs 3.0|2016, title = {A new design for the implementation of isogeometric analysis in Octave and Matlab: GeoPDEs 3.0}, year = {2016}, month = {April}, pages = {44 p.}, institution = {IMATI-CNR}, type = {Working paper}, address = {Pavia}, abstract = {

GeoPDEs (http://rafavzqz.github.io/geopdes)\  is an Octave/Matlab package for the solution of partial differential equations with isogeometric analysis, first released in 2010. In this work we present in detail the new design of the package, based on the use of Octave and Matlab classes. Compared to previous versions the new design is much clearer, and it is also more efficient in terms of memory consumption and computational time.

}, keywords = {Structure-preserving discretizations}, url = {http://irs.imati.cnr.it/reports/irs16-02}, author = {R. V{\'a}zquez} } @article {irs16-01, title = {Optimal strategies for a time-dependent harvesting problem}, number = {16-01}, year = {2016}, month = {February}, pages = {44 p.}, publisher = {IMATI-CNR}, type = {Working paper}, address = {Pavia}, abstract = {

We focus on an optimal control problem, introduced by Bressan and Shen in [5] as a model for fish harvesting. We consider the time-dependent case and we establish existence and uniqueness of an optimal strategy, and sufficient conditions for optimality. We also consider a related differential game that models the situation where there are several competin fish companies and we prove existence of Nash equilibria. From the technical viewpoint, the most relevant point is establishing the uniqueness result. This amounts to prove precise a-priori estimates for solutions of suitable parabolic equations with measure-valued coefficients. All the analysis is developed in the case when the fishing domain is one-dimensional.

}, keywords = {Optimal control}, url = {http://irs.imati.cnr.it/reports/irs16-01}, author = {G.M. Coclite and M. Garavello and L.V. Spinolo} } @article {ipa|Optimal-order isogeometric collocation at Galerkin superconvergent points|2016, title = {Optimal-order isogeometric collocation at Galerkin superconvergent points}, year = {2016}, month = {September}, pages = {22 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

In this paper we investigate numerically the order of convergence of an isogeometric collocation method that builds upon the least-squares collocation method presented in [1] and the variational collocation method presented in [14]. The focus here is on smoothest B-splines/NURBS approximations, i.e, having global C p-1 continuity for polynomial degree p. In particular, we show that using as collocation points a suitable subset of those considered in [1] (which are related to the Galerkin superconvergence theory) it is possible to achieve optimal L2-convergence for odd degree B-splines/NURBS approximations with a pure collocation scheme, i.e., considering as many collocation points as degrees-of-freedom. The method in [1], instead, is based on a leastsquares formulation due to the fact that the set of collocation points outnumbers the degrees-of-freedom to be computed. We especially highlight that we obtain fourth-order convergence for the L2 and L$\infty$ norm of the error when considering cubic basis functions. Further careful analysis is however needed, since the robustness of the method and its mathematical foundations are still unclear.

}, keywords = {Superconvergent points}, url = {http://irs.imati.cnr.it/reports/irs16-13}, author = {M. Montardini and G. Sangall and L. Tamellini} } @article {ipa|Persistence-based tracking of rainfall field maxima|2016, title = {Persistence-based tracking of rainfall field maxima}, year = {2016}, month = {July}, pages = {16 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

In this paper we propose a novel methodology for tracking the maxima of rainfall precipitation fields, whose changes in time may give interesting insights on the evolution of storms. Our approach is based on a topological analysis of rainfall data allowing for the extraction of the most prominent, and hence meaningful, rainfall field maxima. Then, an ad-hoc bottleneck matching is used to track the evolution of maxima along multiple time instances. The potential of our method is exhibited through a set of experiments carried out on a collection of observed punctual rainfall data and radar measurements provided by Genova municipality and Regione Liguria.

}, keywords = {Storm tracking}, url = {http://irs.imati.cnr.it/reports/irs16-11}, author = {D. Sobrero and A. Cerri and S. Biasotti and S. Pittaluga and M. Spagnuolo} } @article {ipa|Studio e sviluppo di componenti semantiche riusabili per la progettazione di serious game. Applicazioni all{\textquoteright}area edutainment|2016, title = {Studio e sviluppo di componenti semantiche riusabili per la progettazione di serious game. Applicazioni all{\textquoteright}area edutainment}, year = {2016}, month = {July}, pages = {12 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

I serious game sono videogiochi che hanno una finalit{\`a} primaria diversa da quella del puro divertimento, ad esempio quella di trasmettere dei contenuti educativi, oppure di sensibilizzare il pubblico rispetto a determinate tematiche Con particolare riferimento all{\textquoteright}area edutainment, questi giochi contengono al loro interno una grande quantit{\`a} di conoscenze relative al dominio applicativo. Perch{\'e} il gioco sia realistico dal punto di vista delle interazioni, tali conoscenze vanno tradotte anche nei comportamenti veri e propri dei personaggi del gioco. In questo lavoro {\`e} stata sviluppata una metodologia e opportuni strumenti software che consentono di tradurre tali conoscenze formalizzate usando OWL e RDF in comportamenti veri e propri all{\textquoteright}interno del motore di gioco. Il lavoro svolto rappresenta un primo passo nella creazione di componenti riusabili, in cui gli oggetti di gioco sono arricchiti con la conoscenza del dominio e possono essere riutilizzati in contesti differenti, con un notevole abbattimento dei costi per gli attori coinvolti nella realizzazione del gioco stesso (esperti del dominio e sviluppatori di giochi.

}, keywords = {Semantics}, url = {http://irs.imati.cnr.it/reports/irs16-12}, author = {A. Repetto and C.E. Catalano} } @article {ipa|A study of the state of the art of process planning for additive manufacturing|2016, title = {A study of the state of the art of process planning for additive manufacturing}, year = {2016}, month = {May}, pages = {16 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

In the manufacturing industry the term Process Planning (PP) is concerned with determining the sequence of individual manufacturing operations needed to produce a given part or product with a certain machine. In this technical report we propose a preliminary analysis of scientic literature on the topic of process planning for Additive Manufacturing (AM) technologies (i.e. 3D printing). We observe that the process planning for additive manufacturing processes consists of a small set of standard operations (repairing, orientation, supports, slicing and toolpath generation). We analyze each of them in order to emphasize the most critical aspects of the current pipeline as well as highlight the future challenges for this emerging manufacturing technology.

}, keywords = {Process planning}, url = {http://irs.imati.cnr.it/reports/irs16-04}, author = {M. Livesu and M. Attene and M. Spagnuolo and B. Falcidieno} } @article {ipa|Adaptive isogeometric methods with hierarchical splines: error estimator and convergence|2015, title = {Adaptive isogeometric methods with hierarchical splines: error estimator and convergence}, year = {2015}, month = {January}, pages = {30 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

The problem of developing an adaptive isogeometric method (AIGM) for solving elliptic second-order partial differential equations with truncated hierarchical B-splines of arbitrary degree and different order of continuity is addressed. The adaptivity analysis holds in any space dimensions. We consider a simple residual-type error estimator for which we provide a posteriori upper and lower bound in terms of local error indicators, taking also into account the critical role of oscillations as in a standard adaptive finite element setting. The error estimates are properly combined with a simple marking strategy to define a sequence of admissible locally rened meshes and corresponding approximate solutions. The design of a refine module that preserves the admissibility of the hierarchical mesh configuration between two consectutive steps of the adaptive loop is presented. The contraction property of the quasi-error, given by the sum of the energy error and the scaled error estimator, leads to the convergence proof of the AIGM.

}, keywords = {Numerical schemes}, url = {http://irs.imati.cnr.it/reports/irs15-01}, author = {A. Buffa and C. Giannelli} } @article {ipa|On quasi-interpolation operators in spline spaces|2015, title = {On quasi-interpolation operators in spline spaces}, year = {2015}, month = {December}, pages = {16 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Pavia}, abstract = {

We propose the construction of a class of L2 stable quasi-interpolation operators onto the space of splines on tensor-product meshes, in any space dimension. The estimate we propose is robust with respect to knot repetition and to knot "vicinity" (up to p+1 knots), so it applies to the most general scenario in which the B-spline functions are known to be well defined.

}, keywords = {Quasi-interpolation}, url = {http://irs.imati.cnr.it/reports/irs15-03}, author = {A. Buffa and E.M. Garau and C. Giannelli and G. Sangalli} } @article {irs15-02, title = {Schaeffer{\textquoteright}s regularity theorem for scalar conservation laws does not extend to systems}, number = {15-02}, year = {2015}, month = {4th May 2015}, pages = {47}, publisher = {CNR-IMATI}, type = {Working paper}, edition = {Imati Report Series}, address = {Pavia}, abstract = {

Schaeffer{\textquoteright}s regularity theorem for scalar conservation laws can be loosely speaking formulated as follows. Assume that the flux is uniformly convex, then for a generic smooth initial datum the admissible solution is smooth outside a locally finite number of curves in the (t, x) plane. Here the term "generic{\textquotedblright} is to be interpreted in a suitable sense, related to the Baire Category Theorem. Whereas other regularity results valid for scalar conservation laws with convex fluxes have been extended to systems of conservation laws with genuinely nonlinear characteristic fields, in this work we exhibit an explicit counterexample which rules out the possibility of extending Schaeffer{\textquoteright}s Theorem. The analysis relies on careful interaction estimates and uses fine properties of the wave front-tracking approximation.

}, keywords = {Conservation laws, Regularity, Schaeffer theorem, Shock formation}, url = {http://irs.imati.cnr.it/reports/irs15-02}, author = {L.V. Spinolo and L. Caravenna} } @article {PSR1-15, title = {A variational principle for gradient flows of nonconvex energies}, number = {1PV15/0/0}, year = {2015}, month = {12 april 2015}, pages = {23}, publisher = {CNR-IMATI}, type = {Working paper}, chapter = {Serie Rossa}, address = {Pavia}, abstract = {

We present a variational approach to gradient ows of energies of the form \ E = {\o}1 {\textendash} {\o}2 \ where\ {\o}1 {\textendash} {\o}2 \ are convex functionals on a Hilbert space. A global parameter-dependent functional over trajectories is proved to admit minimizers.These minimizers converge up to subsequences to gradient-flow trajectories as the parameter tends to zero. These results apply in particular to the case of non λ-convex energies E. The application of the abstract theory to classes of nonlinear parabolic equations with nonmonotone nonlinearities is presented.

}, keywords = {Evolution equations, Gradient flow, Nonconvex energy, Variational formulation}, issn = {1722-8964}, url = {http://archives.imati.cnr.it/publ-r/1PV15}, author = {G. Akagi and U. Stefanelli} } @article {psr11PV14, title = {Consanguinity and late fertility: spatial analysis reveals positive association patterns}, number = {11PV14/0/0}, year = {2014}, month = {4 December 2014}, pages = {21}, publisher = {CNR-IMATI}, type = {Preprint}, chapter = {Serie Rossa}, address = {Pavia}, abstract = {

The role of consanguinity on human complex traits is an important and controversial issue. In this work we focused on Sardinian population and examined the effect of consanguineous unions on late female fertility. During the last century the island has been characterized by high incidence of marriages between relatives, favoured by socio economic conditions and geographical isolation, and by high fertility despite a widespread tendency to delay reproduction. Through spatial analysis techniques, we explored the geographical heterogeneity of consanguinity and late fertility, and identified in Central-Eastern Sardinia a common excess area where the traits are positively associated. We found that their association did not significantly affect woman{\textquoteright}s fertility in the area, despite the expected negative role of both traits. Intriguingly, such critical zone includes the genetically homogeneous Ogliastra region, and well matches areas reported by previous studies as peculiar for high frequency of centenarians and for lower risk in pregnancy outcome. The spatial analysis approach we adopted is quite general and can be exploited to single out critical areas where population screenings, carried out at molecular level, could help disentangle determinants of complex biological traits and investigate their association.

}, keywords = {Consanguinity, Kernel smoothing, Late reproduction, Spatial analysis, Woman fertility}, issn = {1722-8964}, doi = {https://doi.org/10.1111/ahg.12092}, url = {http://archives.imati.cnr.it/publ-r/11PV14}, author = {A. Lisa and P. Astolfi and G. Zei and S. Tentoni} } @article {psr2PV13/2/0, title = {Assigning probabilities to qualitative dynamics of gene regulatory networks}, number = {2PV13/2/0}, year = {2013}, month = {02/2013}, pages = {26}, publisher = {IMATI}, type = {Preprint}, chapter = {Serie rossa}, address = {Pavia}, abstract = {

Mathematical and computational modeling frameworks play the leading role in the analysis and prediction of the dynamics of gene regulatory networks. The literature abounds in various approaches, all of which characterized by strengths and weaknesses. Among the others, Ordinary Differential Equations (ODE) models give a more general and detailed description of the network structure. But, analytical computations might be prohibitive as soon as the network dimension increases, and numerical simulation could be nontrivial, time-consuming and very often impracticable as precise and quantitative information on model parameters are frequently unknown and hard to estimate from experimental data. Last but not least, they do not account for the intrinsic stochasticity of regulation. In the present paper we consider a class of ODE models with stochastic parameters. The proposed method separates the deterministic aspects from the stochastic ones. Under specific assumptions and conditions, all possible trajectories of an ODE model, where incomplete knowledge of parameter values is symbolically and qualitatively expressed by initial inequalities only, are simulated in a single run from an initial state. Then, the occurrence probability of each trajectory, characterized by a sequence of parameter inequalities, is computed by associating probability density functions with network parameters. As demonstrated by its application to the gene repressilator system, the method seems particularly promising in the design of synthetic networks.

}, keywords = {Gene regulatory networks, nonlinear ODE models, qualitative simulation, stochastic parameters}, issn = {1722-8964}, doi = {https://doi.org/10.1007/s00285-014-0765-z}, url = {http://archives.imati.cnr.it/publ-r/2PV13/2/0}, author = {L. Ironi and E. Lanzarone} }