The IMACS Series in Computational and Applied Mathematics collects refereed papers on research results presented in scientific events held under the auspices of the International Association for Mathematics and Computers in Simulation (IMACS). The MASCOT2018 Proceedings Book refers to the 15th IMACS/ISGG International Workshop of the MASCOT series of meetings which is yearly organised since 2001. The latest MASCOT 2018, 15th Meeting on Applied Scientific Computing and Tools, Grid Generation, Approximation and Visualization, dealt with mathematical modelling, methodologies and advanced applications, which are the themes of the contributions here collected.

MASCOT2018 is the 15th edition of the IMACS/ISGG workshop focused on methods and tools for the complete cycle of numerical modelling and simulation, from the development of theoretically well based models and methods to the deep investigation of crucial applications, from geometry and model construction to its implementation, from data analysis and powerful design of computational tools, with advanced capabilities. Aim of the workshop is the presentation and discussion of innovative technologies dealing with all aspects of computational processes. We recall, but without limiting to them, methodologies for effective grid generation, advanced approximation methods, identification and application of efficient PDE numerical solution algorithms, the development of powerful tools for image processing and scientific visualization. The workshop would bring together developers and users of computational methods and software tools to go deeper into advantages of new methodologies, discuss applications and results, illustrate educational approaches, identify new needs and innovative development directions in a growing variety of problems in applied mathematics

Prefazione al numero speciale della rivista dedicato agli articoli selezionati successivi al workshop MASCOT2015

volume speciale dedicato ad articoli selezionati e risultanti dal workshop MASCOT2015

Book of proceedings of the workshop MASCOT 2015, 14th Meeting on Applied Scientific Computing and Tools, held in Rome on June 9 - 12, 2015, at IAC (CNR). The program of the meeting, in each presentations, and the contents of this volume, in each paper, show advanced expertise matured in several countries, both in west and east Europe and overseas, all speakers and authors coming from high qualified universities and research centers. The large spectrum of topics approached by the applied scientific computing works deals with numer- ical methods and computational tools (i.e. approximation theory, grid genera- tion, unstructured grids, ...) for modelling a variety of fundamental problems, approximate and simulate important applicative problems in: fluid dynamics, granular materials and materials with memory, chemotaxis, crowd dynamics, environmental problems, urban heat islands, grinding wheels, imaging, image segmentation and data analysis. Raccolta degli atti del workshop internazionale MASCOT 2015, 14th Meeting on Applied Scientific Computing and Tools, tenutosi a Roma nel periodo 9 - 12 giugno 2015 presso l'IAC (CNR).

This is the web-site of the workshop 'Mathematical Approach to Climate Change Impacts" held in Rome at INDAM on March 13 - 17, 2017, organized by Piermarco Cannarsa (uni. Tor Vergata), Daniela Mansutti (IAC - CNR) and Antonello Provenzale (IGG - CNR). Beside the program and other practical aspects related to the conference days, it exhibits the book of abstracts and, thanks to the generosity of the lecturers, the slides of each presentation (plenary, contributing and tutorial), which make it very rich of scientific information.

The workshop Mathematical Approach to Climate Change Impacts (MAC2I) has been styled to drive the attention within Italian academy and public research institutions towards applied mathematics research in environmental problems related to climate change. A number of renowned specialists delivered plenary lectures to introduce the hottest issues, contributed talks were selected in order to exemplify recent successful mathematical developments in this applicative field and two tutorials introduced the mathematical modelling tools to approach clue subjects. The program has been structured into four thematic sessions, respectively glaciology, hydrology, ecosystem science and environmental monitoring. Panel discussions and brain-storming were included as an opportunity for the emergence of new ideas in the right atmosphere to foster scientific international collaborations. The workshop, appropriate also within a PhD course program, was conceived in the context of the excellence project of applied mathematics MATH-TECH, funded by the Italian Ministry of Education, University and Research (MIUR) awarded to the Institute for Applied Mathematics (IAC) "M. Picone" of the National Research Council (CNR) and to the Istituto Nazionale di Alta Matematica (INDAM) (2015-2017).

The melting of glaciers coming with climate change threatens the heritage of the last glaciation of Europe likely contained in subglacial lakes in Greenland and Svalbard, which look fated to disappear. This aspect urges specialists to focus their studies (theoretical, numerical and on-field) on such fascinating objects. Along this line we have approached the validation of the conjecture of the existence of a subglacial lake beneath the Amundsenisen Plateau at South-Spitzbergen, Svalbard, where Ground Penetrating Radar measurements have revealed several flat signal spots, sign of the presence of a body of water. The whole investigation aspects and tools, mathematical modeling and numerical simulation procedure, the computational algorithm and the numerical results obtained on the real study case, have been sketched at workshop time, and the decision has been discussed to undertake drilling operations above the presumed ice/water front, where subglacial lake water bio-chemicals might be traceable. This investigation is a follow-up of the multi and interdisciplinary research activities based at the Arctic Station ''Dirigibile Italia'', coordinated by the ''Dipartimento Scienze del Sistema Terra e Tecnologie per l'Ambiente'' of CNR (I) and of the transnational project 'SvalGlac - Sensitivity of Svalbard Glaciers to Climate Change' funded by ESF-ERANET PolarClimate Consortium (PNRA for Italy).

The likelihood of a subglacial lake beneath Amundsenisen Plateau at Southern Spitzbergen, Svalbard, pointed out by the flat signal within the Ground Penetrating Radar (GPR) remote survey of the area, is justified, here, via numerical simulation.This investigation has been developed under the assumption that the icefield thickness does not change on average, as it is confirmed by recently published physical measurements taken over the past 40 years. As a consequence, we have considered admissible to assume the temperature and density in-depth profiles, snow and firn layers included, to be stationary. The upper icefield surface and the rocky bed surface are known in detail.The mathematical numerical model is based on an unsteady Stokes formulation of the ice flow and on a Large Eddy Simulation formulation of the lake water flow. Following the numerical sensitivity results that we presented on a recent issue of this journal, we have, here, upgraded the model by improving the description of critical aspects of icefield thermo-mechanics, such as the local water release within temperate ice as a strain heating effect and ice sliding on the bedrock. The first issue impacts on ice texture, i.e. its constitutive equation, while the second one drives icefield surging. Actually, we have obtained 13% enhancement of the numerical value of the ice top surface velocity versus measured one, and physically consistent numerical ice sliding velocity values at the rocky bottom.Adopting a new physically sound initial subglacial lake water temperature and velocity fields, we present the numerical simulation of the whole system, icefield and conjectured subglacial lake, within a time slot of 20,000. d (physical time), when its evolution trend was clearly captured. By then, although the maximum value of water temperature keeps rather low, metastability appears to be overcome on more than half of the conjectured basin, with a progressive trend in time in support to the subglacial lake existence. We stress that the numerical subglacial lake surface converges to the GPR flat signal spot with tolerance equal to the GPR measuring error.Finally, we observe that the numerical simulation results meet quantitatively and qualitatively the fundamental aspects of the conjecture, so that further on-site investigations on the subglacial lake (e.g. drilling operations) appear fully justified.

Nell'ambito del workshop d'inaugurazione dell'anno accademico dell'Associazione Matematica & Realta', la presentazione intende offrire alla platea degli insegnanti di matematica delle scuole superiori di secondo grado un esempio realmente implementato di attivita' di studio e ricerca di matematica applicata. Vi si trovano ben delineati i passi fondamentali che conducono dal problema reale alla soluzione numerica proposta, manifestando la necessita' di conoscenze interdisciplinari per giungere all' uso critico ed efficace dello strumento matematico. Il problema specifico considerato e' la validazione dell'ipotesi dell'esistenza di un lago subglaciale a Spitzbergen, isola dell'arcipelago delle Svalbard.

The segmentation of speckled images, as the synthetic aperture radar (SAR) images, is usually recognized as a very complex problem, because of the speckle, multiplicative noise, which produces granular images. In segmentation problems, based on level set method, the evolution of the curve is determined by a speed function, which is fundamental to achieve a good segmentation. In this paper we propose a study of the new speed function obtained by the linear combination of image average intensity and image gradient speed functions. Thus the aim is tuning the combined speed in the segmentation process. We segmented synthetic images by tuning parameters of the new speed function and we evaluated the best computed results. Then we applied this experimental setup to real SAR images, which are PRecision Images, acquired during European Remote Sensing mission, and a Cosmo-SkyMed image. In particular, we are interested in monitoring complex areas with low light covered by clouds, as coastlines and polar regions may be. In Earth Observation, the acquisition of SAR data becomes fundamental, since the SAR sensor can work in the night/day and in all weather conditions.

The melting of glaciers coming with climate change threatens the heritage of the last glaciation of Europe likely contained in subglacial lakes in Greenland and Svalbard. This aspect urges specialists to focus their studies (theoretical, numerical, and on-field) on such fascinating objects. Along this line, we have approached the validation of the conjecture of the existence of a subglacial lake beneath the Amundsenisen Plateau at South-Spitzbergen, Svalbard, where ground penetrating radar measurements have revealed several flat signal spots, the sign of the presence of a body of water. The whole investigation aspects, mathematical modeling and numerical simulation procedure, and the numerical results are presented through a trilogy of papers of which the present one is the last. The time-dependent mathematical model in the background of the numerical algorithm includes the description of dynamics and thermodynamics of the icefield and of the subglacial lake, with heat exchange and liquid/solid phase-change mechanisms at the interface. Critical modeling choices and confidence in the algorithm are granted by the numerical results of the sensitivity analysis versus the contribution of ice water content, of firn and snow layers at top of the icefield and versus the approximation of ice sliding on bedrock. The two previous papers deal with these issues, show successful comparison with local measured quantities, and demonstrate numerically the likelihood of the subglacial lake. In this work, we aim at providing the studied case and the numerical algorithm with a possible paradigmatic value. At this aim, we introduce on-field measurement data related to the physical characteristics of the Amundsenisen Plateau that justify the adoption of significant modeling simplifications, here, focussed from physical viewpoint. Furthermore, we present the numerical algorithm and discuss several representative results from the numerical test to point out the type of results coming from the procedure. Such results might, eventually, provide a support to the decision to undertake drilling operations for tracing the subglacial water bio-chemicals generally present within the accreted ice above the presumed ice/water front.

The likelihood of a subglacial lake beneath Amundsenisen Plateau at Southern Spitzbergen, Svalbard, pointed out by the flat signal within the Ground Penetrating Radar (GPR) remote survey of the area, is justified, here, via numerical simulation. This investigation has been developed under the assumption that the icefield thickness does not change on average, as it is confirmed by recently published physical measurements taken over the past forty years. As consequence, we have considered admissible to assume the temperature and density in-depth profiles, snow and firn layers included, to be stationary. The upper icefield surface and the rocky bed surface are known in detail. By adopting a mathematical numerical model, presented on a recent issue of this journal, based on an unsteady Stokes formulation of the ice flow and a Large Eddy Simulation formulation of the lake water flow, first, we compare two different descriptions of ice water content, in the form of a steady depth dependent function and as solution to the mass transport equation, accounting for local strain heating effect. The last approach, finally selected, leads to 13% improvement of the numerical value of the ice top surface velocity vs. measured one. Furthermore a reduced form of the basal shear stress and normal stress, by making easier the convergence of the iterative solution procedure, allows to obtain physically consistent numerical ice sliding velocity values at the rocky bottom, quite improved in comparison to previous numerical results. After 20000 d (physical time), although the maximum value of water temperature keeps rather low, the numerical simulation shows that metastability is overcome on more than half of the conjectured basin, with a progressive trend in time in support to the subglacial lake existence. By that time, the numerical subglacial lake surface converges to the GPR flat signal spot with tolerance equal to the GPR measuring error. Then numerical simulation results meet quantitatively and qualitatively the fundamental aspects of the conjecture, so that further on-site investigations on the subglacial lake (e.g. drilling operations) appear fully justified.

The melting of glaciers coming with climate change threatens the heritage of the last glaciation of Europe likely contained in subglacial lakes in Greenland and Svalbard. This aspect urges specialists to focus their studies (theoretical, numerical and on-field) on such fascinating objects. Along this line we have built up a numerical procedure for validating the conjecture of the existence of a subglacial lake beneath the Amundsenisen Plateau at South-Spitzbergen, Svalbard. In this work we describe the algorithm and significant representative results of the related numerical test. The conjecture followed the Ground Penetrating Radar measurements of that area exhibiting several flat signal spots, sign of the presence of a body of water. Actually, numerical simulation results appear in support to the decision of drilling operations above the presumed ice/water front where subglacial lake water bio-chemicals might be traceable. The time dependent mathematical model, structuring the numerical algorithm, includes the description of dynamics and thermodynamics of the icefield and of the subglacial lake, with heat exchange and liquid/solid phase change mechanisms at the interface. Critical modeling choices and confidence in the algorithm are granted by the numerical results of the sensitivity analysis versus the contribution of ice water content, of firn and snow layers at top of the icefield and versus the approximation of ice sliding on bedrock, that have been issued in previous recent works also including successful comparison with measured quantities.

Beside geographical and physical characteristics of the environment, mostly temperature changes drive glacier dynamical evolution with subglacial and supraglacial water release or approaching a metastable state. The appearance of subglacial lakes filling bedrock depressions, glacier sliding, crevasses formation and calving are linked climate change sensitive macro-phenomena, where interactions between the interfacing phases are crucial. We shall discuss the mathematical modelling and the numerical simulation of one of the above glacier problems with moving boundary. References A. Di Mascio, R. Broglia and R. Muscari, "On the application of the single- phase level set method to naval hydrodynamic flows", Computers & Fluids, Vol.36, 2007, pp. 868-863. D. Mansutti, E. Bucchignani, J. Otero and P. Glowacki, "Modelling and numerical sensitivity study on the conjecture of a subglacial lake at Amundsenisen, Svalbard", Applied Mathematical Modelling, http://dx.doi.org/10.1016/j.apm.2014.12.043 (in press), 2014.

Il 14 dicembre del 1955, presso la sede Centrale del CNR, il Presidente della Repubblica, Giovanni Gronchi, inaugurava il calcolatore elettronico Ferranti Mark1* dell'Istituto Nazionale per le Applicazioni del Calcolo, alla presenza del fondatore e direttore dell'Istituto, il matematico Mauro Picone. Dal nome del costruttore e dalla sigla dell'istituto, la macchina venne denominata FINAC. Si trattava del secondo calcolatore elettronico installato in Italia, preceduto di pochi mesi dal CRC-102A del Politecnico di Milano. L'acquisto era avvenuto grazie agli sforzi di Picone per dotare il suo istituto di una delle 'potenti macchine calcolatrici elettroniche', all'epoca solo anglo-americane. Negli anni precedenti Picone era giunto più volte ad un passo dal realizzare il suo intento di costruire quello che, sarebbe stato il primo calcolatore italiano. Aveva maturato questo proposito viaggiando negli USA, dove l'analisi numerica progrediva enormemente con lo sviluppo di progetti su 'macchine calcolatrici a cifre ad alta velocità'. Poiché una serie di impedimenti, internazionali e interni, rischiavano di prolungare eccessivamente i tempi, Picone scelse di acquistare un'apparecchiatura già in commercio, che sarebbe poi stata la FINAC, che per alcuni anni rimase il più potente computer italiano. Con esso vennero sviluppate molte ricerche sui temi più svariati, dal modello econometrico della Banca d'Italia ai calcoli per la progettazione di ponti e dighe. Un lavoro, particolarmente significativo per lo sviluppo dell'informatica italiana, fu la realizzazione di un simulatore della CEP, futura Calcolatrice Elettronica Pisana. Con questo anniversario si vuole celebrare, tra le altre cose, l'intuizione di Mauro Picone, la sua capacità innovativa e la scelta di investire generosamente nel futuro, conferendo grande impulso alla soluzione di problemi reali attraverso la modellizzazione matematica, creando anche in Italia i presupposti per lo sviluppo della moderna matematica applicata e dell'informatica

Lo studio dell'idrologia polare e' legato alla glaciologia ma anche alla paleobio- logia e alla bioastronomia, alla planetologia. Per quest'ultima vale la similitudine fra la crosta ghiacciata dei satelliti del pianeta Giove - Europa ed Encelado - e la calotta ghiacciata Antartica, sotto cui scorre, nell'ordine, un oceano d'acqua (da accertare) e una complessa rete idrografica di 379 laghi subglaciali con torrenti col- legati al mare. Lo studio dell'idrologia polare ha un riscontro diretto e propone estrapolazioni sui pianeti. La paleobiologia e' invece interessata ai laghi subglaciali isolati, custodi di segreti della vita primordiale: microrganismi antichi, nell'oscurita', con bassissimi scambi energetici, senza contatti con altre forme di vita. Siamo al confine con la bioastronomia che ricerca sui pianeti tracce di acqua e di vita. La modellistica matematica e la simulazione numerica giungono a supporto di opera- zioni di carotaggio o, al contrario, per evitarle al fine di non contaminare queste banchedati naturali, oppure per proiezioni diagnostiche o prognostiche. Discutero' il problema dell'accertamento del primo lago subglaciale alle isole Svalbard, di cui e' traccia (da interpretare) nei rilevamenti Ground Penetrating Radar. Il modello matematico adottato contiene la descrizione della dinamica e termodinamica del si- stema ghiacciaio/lago corredato di dati da spedizione polare. Il sistema differenziale viene risolto con il metodo ai volumi finiti e uno schema implicito di secondo ordine; la tecnica di front-tracking viene adottata per la frontiera di fase evolutiva (dettagli in [1]). La procedura di validazione della congettura da noi proposta, totalmente nuova ai glaciologi, ha portato a risultati numerici con ottimo riscontro con i dati di misura e conferma la possibilita' di esistenza del lago subglaciale (conclusioni in [2]). Bibliografia [1] Mansutti, D., E. Bucchignani, J. Otero and P. Glowacki, 'Modelling and numerical sensitivity study on the conjecture of a subglacial la- ke at Amundsenisen, Svalbard', (in stampa) Appl. Math. Modelling, http://dx.doi.org/10.1016/j.apm.2014.12.043, 2015. [2] Mansutti, D., E. Bucchignani, J. Otero and P. Glowacki, 'Numerical validation of the conjecture of a subglacial lake at Amundsenisen, Svalbard', (sottomesso) Appl. Math. Modelling, 2015.