An innovative approach to simulate thrombosis with smoothed particle hydrodynamics

La trombosi è una patologia che porta alla formazione di coaguli, che possono provocare ostruzioni arteriose e, infine, migrano attraverso il sistema cardiocircolatorio causando infarto, ictus o embolia polmonare. Il processo è abbastanza complesso ed il suo meccanismo non è ancora chiaro, essendo il risultato dell’interazione tra diversi fattori, compresa l'attivazione e l'aggregazione piastrinica, le reazioni chimiche e l'emodinamica.È fondamentale considerare e ridurre al minimo la formazione di trombi nella progettazione e realizzazione di organi artificiali, come valvole cardiache artificiali o protesi. Lo studio dell'emodinamica può fornire un supporto efficace per identificare e prevenire il rischio di trombosi.A causa della mancanza di soluzioni analitiche adeguate e della complessità degli studi sperimentali, la ricerca evolve sempre più verso l’utilizzo delle simulazioni numeriche Questa tesi mira a modellare la formazione, la crescita e l'evoluzione del trombo mediante il metodo numerico accoppiato Smoothed Particle Hydrodynamics (SPH) usando un modello di interazione fluido-struttura (FSI). Il modello proposto descrive le principali fasi della cascata coagulativa attraverso l'equilibrio di quattro specie biochimiche e tre tipologie di piastrine. Le particelle SPH possono passare dalla fase fluida a quella solida se sono soddisfatte delle specifiche condizioni biochimiche e fisiche. L'accoppiamento fluido-solido è modellato introducendo legami elastici tra le particelle solide senza nessuna interfaccia. Per raggiungere questo obiettivo, in primo luogo il modello viene validato confrontando i risultati numerici con i dati sperimentali disponibili in letteratura, in secondo luogo, il nuovo codice numerico è applicato per descrivere la trombosi in appendice atriale in caso di fibrillazione o come trombosi indotta in aneurismi cerebrali.Thrombosis is a pathology leading to the formation of clots, that can result in arterial obstructions and, eventually, migrate through the cardiocirculatory system causing heart attack, stroke or pulmonary embolism. The process is complex and its mechanism is still unclear, being the result of the interaction between various factors, including platelet activation and aggregation, chemical reactions, and hemodynamics.It is crucial to consider and minimise thrombosis in the design and implementation of artificial organs, such as artificial heart valves, and vascular prostheses. The study of hemodynamics can provide effective support to identify and prevent the risk of thrombosis.Due to the lack of adequate analytical solutions and the complexity of experimental studies, research increasingly evolves towards the use of computational methods.This thesis aims at modelling the formation, growth and evolution of thrombus by means of a Smoothed Particle Hydrodynamics (SPH) numerical method coupled with a fluid-structure interaction (FSI) model. The proposed model describes the main phases of the coagulative cascade through the balance of four biochemical species and three types of platelets. SPH particles can switch from fluid to solid phase whenspecific biochemical and physical conditions are satisfied. Fluid-solid coupling is modelled by introducing elastic binds between solid particles, without requiring detention and management of the interface between the two media.In order to reach this goal, firstly the model is validated by comparing the numerical prediction with experimental data available in the literature, secondly, it is applied to describe thrombosis formation due to relevant pathologies such as atrial fibrillation and cerebral aneurysms where the insertion of flow diverter creates thrombogenic stasis zone

Design and Performance of a High Temperature Superconducting Axial Flux Generator

In this paper, a high temperature axial flux (HTSAF) generator is presented. In this generator the excitation of the generator is obtained by using some high temperature superconducting magnets. In order to reduce the negative effects of vibrations, the excitation is located on the stationary part of the generator. Starting, running and endurance tests of the machine are presented

Evaluation of the Potential Energy from Wave Motion on the Sicilian coast

The purpose of this articles is quantitatively evaluate the wave climate variations of the northern Sicilian coasts. In particular, the objective of the study is Castellammare del Golfo, a marine site between Trapani and Palermo. In particular in this research, the wave energy of the Sicily has been studied by an analysis of wave data carried out in a 10- year period, using the measurements of buoyant of RON. The north-western and southern coasts of Sicily have a lower potential with average wave power ranging between 2.5 and 6.5 kW/m

Modelling of thrombus formation using smoothed particle hydrodynamics method

In this paper a novel model, based on the smoothed particle hydrodynamics (SPH) method, is proposed to simulate thrombus formation. This describes the main phases of the coagulative cascade through the balance of four biochemical species and three type of platelets. SPH particles can switch from fluid to solid phase when specific biochemical and physical conditions are satisfied. The interaction between blood and the forming blood clot is easily handled by an innovative monolithic FSI approach. Fluid-solid coupling is modelled by introducing elastic binds between solid particles, without requiring detention and management of the interface between the two media. The proposed model is able to realistically reproduce the thromboembolic process, as confirmed by the comparison of numerical results with experimental data available in the literature

Hydrogen Production from Sea Wave for Alternative Energy Vehicles for Public Transport in Trapani (Italy)

The coupling of renewable energy and hydrogen technologies represents in the mid-term a very interesting way to match the tasks of increasing the reliable exploitation of wind and sea wave energy and introducing clean technologies in the transportation sector. This paper presents two different feasibility studies: the first proposes two plants based on wind and sea wave resource for the production, storage and distribution of hydrogen for public transportation facilities in theWest Sicily; the second applies the same approach to Pantelleria (a smaller island), including also some indications about solar resource. In both cases, all buses will be equipped with fuel-cells. A first economic analysis is presented together with the assessment of the avoidable greenhouse gas emissions during the operation phase. The scenarios addressed permit to correlate the demand of urban transport to renewable resources present in the territories and to the modern technologies available for the production of hydrogen from renewable energies. The study focuses on the possibility of tapping the renewable energy potential (wind and sea wave) for the hydrogen production by electrolysis. The use of hydrogen would significantly reduce emissions of particulate matter and greenhouse gases in urban districts under analysis. The procedures applied in the present article, as well as the main equations used, are the result of previous applications made in different technical fields that show a good replicability

The Desalination Process Driven by Wave Energy: A Challenge for the Future

The correlation between water and energy is currently the focus of several investigations. In particular, desalination is a technological process characterized by high energy consumptionnevertheless, desalination represents the only practicable solution in several areas, where the availability of fresh water is limited but brackish water or seawater are present. These natural resources (energy and water) are essential for each otherenergy system conversion needs water, and electrical energy is necessary for water treatment or transport. Several interesting aspects include the study of saline desalination as an answer to freshwater needs and the application of renewable energy (RE) devices to satisfy electrical energy requirement for the desalination process. A merge between renewable energy and desalination is beneficial in that it is a sustainable and challenging option for the future. This work investigates the possibility of using renewable energy sources to supply the desalination process. In particular, as a case study, we analyze the application of wave energy sources in the Sicilian context.Univ Palermo UNIPA, Dept Energy Informat Engn & Math Models, I-90128 Palermo, ItalyUniv Fed Sao Paulo UNIFESP, Dept Ciencias Exatas & Terra, BR-09910720 Sao Paulo, BrazilDepartament of Ciências Exatas e da Terra, Universidade Federal de São Paulo (UNIFESP), Sao Paulo 09910-720, BrazilWeb of Scienc

Dynamic Preisach hystersis model for magnetostrictive materials for energy application

Recently Magnetostrictive materials have been proposed as active materials to be used in several energy harvesting technology [1]. In this kind of application, the working condition of the material is highly dynamic and non linear. As a result static models of magnetostrictive materials are usually not very accurate and can be not reliable to develop a sufficiently accurate designof the energy harvesting devices. The presence of hysteresis requires accurate mathematical modeling in order to correctly foresee the behavior of real materials (ferromagnetic or magnetostrictive) used in control systems or in electrical machines and thus simplifying the design of such controllers or predicting with acceptable accuracy electromagnetic fields in such devices[2]. In order to overcome this problem, this paper addresses the development of Dynamic Preisach hysteresis model (DPM) for magnetostrictive materials for energy application operating in hysteretic and time varying nonlinear regimes. DPM is a development of classical Preisach Model which is able to include dynamical features in the mathematical model of hysteresis. In this paper the magnetostrictive material considered is Terfenol-D. Its hysteresis is modeled by applying the DPM whose identification procedure is performed by using a neural network procedure previously publised [3]. The neural network used is a multiplayer perceptron trained with the Levenberg-Marquadt training algorithm. This allows to obtain both Everett integrals and the Preisach distribution function, without any special conditioning of the measured data, owing to the filtering capabilities of the neural network interpolators. The model is able to reconstruct both the magnetization relation and the Field-strain relation. The model is validated through comparison and prediction of data collected from a typical Terfenol-D transducer

A procedure to evaluate the indoor global quality by a sub objective-objective procedure

This paper proposes two complementary procedures for assessing the indoor global comfort: the first one, prevalently objective, is based on the acquisition of microclimate measured data and computed subjective values; the second one, that is purely subjective, uses a questionnaire drawn from the ISO/DP 10551 Recommendation. An application to some lecture-halls is here showe