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Publications (81)
In the last years several experimental campaigns have been carried out to assess the performance of High Temperature Superconducting (HTS) cables for nuclear fusion applications. In such experiments it has been often observed that cable performance in terms of critical current
$( I_{c})$
degrade, mainly after quenches. The nature of the degradati...
The association of machine learning (ML) tools with the synthesis of nanoparticles has the potential to streamline the development of more efficient and effective nanomedicines. The continuous-flow synthesis of nanoparticles via microfluidics represents an ideal playground for ML tools, where multiple engineering parameters – flow rates and mixing...
The association of machine learning (ML) tools with the synthesis of nanoparticles has the potential to streamline the development of more efficient and effective nanomedicines. The continuous-flow synthesis of nanoparticles via microfluidics represents an ideal playground for ML tools, where multiple engineering parameters – flow rates and mixing...
The Roadmap to Fusion Electricity draws on innovative experiments pivotal for the accomplishment of the European DEMO, i.e., the demonstration fusion power plant by the EUROfusion Consortium. At the end of the pre-conceptual design phase, the machine comprises three main magnetic systems: 6 poloidal field (PF) coils, 16 toroidal field (TF) coils an...
The DEMO magnet system embodies a set of mechanical structures to join together the different Toroidal Field coils and to provide a suitable support to thermal, magnetic and gravitational loads. Over the years, different baselines have been produced which have required revisions and updates of the studies of the magnetic system and its supporting s...
The roadmap to fusion electricity of the European scientific program aims at the realization of the future DEMOnstration (DEMO) fusion power plant. In 2020, the pre-concept design phase of DEMO was completed, defining the concept and characteristics of the main magnets and structures of the machine. Sixteen toroidal D-shaped magnets, six poloidal a...
NeoChord-DS1000-System (NC) and The Harpoon-Mitral-Repair-System (H-MRS) are two trans-apical chordal implantation devices developed for the treatment of degenerative mitral valve (MV) regurgitation (DMR) either if as Fibroelastic-Deficiency (FED), Forma-Frusta (FF), or Barlow (B) presentation. The aim of this study is to evaluate some of the advan...
The performance of High Temperature Superconducting (HTS) tapes is strongly affected by the mechanical loadings they ex-perience during manufacturing, cooldown and operation. Therefore, the development of HTS-based applications requires thorough investigations on the impact of these loadings on the critical current. In this work, a measurement proc...
We present the pre-concept design of the European DEMO Magnet System, which has successfully passed the DEMO plant-level gate review in 2020. The main design input parameters originate from the so-called DEMO 2018 baseline, which was produced using the PROCESS systems code. It defines a major and minor radius of 9.1 m and 2.9 m, respectively, an on...
The design of the superconducting magnet system of the EU-DEMO tokamak reached the end of the pre-conceptual design phase, and a careful investigation of the parasitic heat load from the room-temperature environment is needed. A possible route for the parasitic heat to enter the toroidal field (TF) coils is by conduction through their Gravity Suppo...
(1) Background: The realization of appropriate aortic replicas for in vitro experiments requires a suitable choice of both the material and geometry. The matching between the grade of details of the geometry and the mechanical response of the materials is an open issue that deserves attention. (2) Methods: To explore this issue, we performed a seri...
The present paper deals with a multiphysics study of the DEMO Toroidal Field (TF) coils with Winding Pack (WP) layout proposed by the Italian agency ENEA. The latest WP configuration, so far designed adopting the Wind&React technique, is composed of 202 Nb3Sn rectangular conductors, with steel jacket thickness progressively increased from the plasm...
The highly infiltrating nature of glioma cells is the major cause for the poor prognosis of brain malignancies. Motility, proliferation, and gene expression of cells in natural and synthetic gels have been analyzed by several authors, yet quantitative studies elucidating the role of matrix porosity and rigidity in the development of whole malignant...
The use of glass for pharmaceutical new applications such as high-technology drugs, requires the strictest container inertness. A common theme of paramount importance in glass container integrity preservation is the detailed mechanism driving the sudden failure due the crack propagation. Using a combination of discrete element method (DEM) and fini...
The use of glass for pharmaceutical new applications such as high-technology drugs, requires the strictest container inertness. A common theme of paramount importance in glass container integrity preservation is the detailed mechanism driving the sudden failure due the crack propagation. Using a combination of Discrete Element Method (DEM) and Fini...
We address the problem of determining from laboratory experiments the data necessary for a proper modeling of drug delivery and efficacy in anticancer therapy. There is an inherent difficulty in extracting the necessary parameters, because the experiments often yield an insufficient quantity of information. To overcome this difficulty, we propose t...
Osteochondral defects are focal areas of damage involving articular cartilage and sub-chondral bone. Tissue engineering scaffolds are used to improve the organism regeneration ability for this kind of injury, serving as biocompatible structures for cell viability and differentiation. Since biomechanical cues such as substrate stiffness, loading con...
The European DEMO, i.e. the demonstration fusion power plant designed in the framework of the Roadmap to Fusion Electricity by the EUROfusion Consortium, is approaching the end of the pre-conceptual design phase, to be accomplished with a Gate Review in 2020, in which all DEMO subsystems will be reviewed by panels of independent experts. The latest...
This work extends to second generation Rare-Earth Barium-Copper-Oxide ((Re)BCO) tapes an experimental procedure previously developed to analyze the impact of double bending at room temperature on the performance of Bismuth-Strontium-Calcium-Copper-Oxide (BSCCO) tapes. The modified procedure is applied to measure the critical current of a commercial...
Transapical off-pump mitral valve repair with neochord implantation is an established technique for minimally-invasive intervention on mitral valve prolapse/flail. The procedure involves the positioning of artificial chords, whose length/tension is adjusted intraoperatively, adopting different methods based on the experience of the surgeon. This un...
In the paper, we discuss details of the formulation of the inverse problem for the determination of mechanical properties of vacuum glazing using feed-forward artificial neural networks.
Mechanical factors play a major role in tumor development and response to treatment. This is more evident for tumors grown in vivo, where cancer cells interact with the different components of the host tissue. Mathematical models are able to characterize the mechanical response of the tumor and can provide a better understanding of these interactio...
Tumor spheroids constitute an effective in vitro tool to investigate the avascular stage of tumor growth. These three-dimensional cell aggregates reproduce the nutrient and proliferation gradients found in the early stages of cancer and can be grown with a strict control of their environmental conditions. In the last years, new experimental techniq...
Mechanical factors play a major role in tumor development and response to treatment. This is more evident for tumors grown in vivo, where cancer cells interact with the different components in the host tissue. Mathematical models are able to characterize the mechanical response of the tumor and can provide a deeper understanding of these interactio...
Computational models for tumor growth provide an effective in silico tool to investigate the different stages of cancer growth. Recently, a series of computational models based on porous media theory has been proposed to predict tumor evolution and its interactions with the host tissue. In addition, a specialization of the original models, adapted...
Recently a new computational model, based on the thermodynamically constrained averaging theory, has been proposed to predict tumor initiation and proliferation and afterwards to study plantar tissue mechanics. The foot tissue is modeled as an elastic porous medium, in large strain regime and completely filled by a fluid phase. By considering the i...
Mathematical investigation of tumor growth is becoming increasingly popular in scientific literature. New experiments and novel test techniques provide extensive sets of data that can be analyzed
by mathematical models and allow for their validation. Here we extend multiphase porous media
mechanics to model tumor evolution, enforcing governing equa...
Mathematical investigation of tumor growth is becoming increasingly popular in scientific literature [1], [2]. New experiments and novel test techniques provide extensive sets of data that can be analyzed by mathematical models and allow for their validation. Here we extend multiphase porous media mechanics to model tumor evolution, enforcing gover...
A new computational model, based on the thermodynamically constrained averaging theory, has been recently proposed to predict tumor initiation and proliferation. A similar mathematical approach is proposed here as an aid in diabetic ulcer prevention. The common aspects at the continuum level are the macroscopic balance equations governing the flow...
In the paper, we propose to use the minimal kinematic boundary conditions (MKBC) procedure of homogenisation for the estimation of thermo-mechanical properties of superconducting, hierarchically structured strand.
The ability to compute accurately the strain field in Nb3Sn filaments is a crucial point in cable design, due to the significant strain sensitivity of niobium–tin wires. Due to its heterogeneity, a straightforward numerical simulation of a cable, taking into account all the details of the microstructure, would result in an enormous number of unknow...
In the presented approach, the Finite Element Method (FEM) and Artificial Neural Network (ANN) are jointly applied to describe dependence of effective parameters of FGM on physical characteristics of micro components and macro variables.
For a steady state convection problem, assuming given concentration field values in a few measurement points and hydraulic head values in the same piezometers, the source of the concentration, and its intensity are deduced using Artificial Neural Networks (ANNs). ANNs are trained with data extracted from Finite Difference (FD) solution of a classic...
In this paper, we consider structures characterized by a definite geometrical hierarchy, such as multilayer wire ropes. We investigate the mechanical behavior, namely, the influence of the hierarchical helix geometry on the stiffness of the cable. It is shown how the stiffness matrix of these structures is different from the usual stiffness matrix...
After a short introduction and main issues associated with inverse problem, three examples are chosen to illustrate the application of Artificial Neural Networks in the inverse problems solution. For a steady state convection problem, assuming given concentration field values in a few measurement points and values of hydraulic head in the same piez...
In this paper we present a combined finite element (FE) - artificial neural network (ANN) approach for the analysis of the behavior of non linear composites and hierarchical structures. Different aspects of ANN use in multiscale numerical homogenization are shown. First, the possibility to model via ANNs the effective material starting from a relat...
This paper deals with homogenization of heterogeneous, fibre-reinforced material. One of the main points of the work consists in taking into account the breakage of the fibres, to compute the effective behaviour of the damaged composite. Furthermore, the possible yielding of the matrix material is considered. The problem is solved for the coupled t...
Root mean squared error of the learning set of data for ANN2321.
Root mean squared error of the learning set of data for ANN231.
Nanoparticles with different sizes, shapes, and surface properties are being developed for the early diagnosis, imaging, and treatment of a range of diseases. Identifying the optimal configuration that maximizes nanoparticle accumulation at the diseased site is of vital importance. In this work, using a parallel plate flow chamber apparatus, it is...
We discuss the role of thermodynamic consistency in multiphysics and multiscale models, and how it can be preserved among scales. The quest for consistency and adoption of thermodynamic non equilibrium models has led to remarkable results in the field of fluid-solid interaction problems such as an improved model for drying shrinkage in concrete or...
n this paper we discuss two multi-scale procedures, both of mathematical nature as opposed to purely numerical ones. Examples are shown for the two cases. Attention is also devoted to thermodynamical aspects such as thermodynamic consistency and non- equilibrium thermodynamics. Advances for the first aspect are obtained by adopting the thermodynami...
Usually in the framework of the self consistent scheme, the homogenised material behaviour is obtained with a symbolic approach. This paper presents a different, fully numerical procedure. We solve a coupled thermo-mechanical problem for non-linear composites with brittle long fibres and properties depending on temperature, by using our development...
Superconducting coils are one of the key technical solutions used for generation of high magnetic field in modern tokamaks. Nb3Sn superconductivity depends not only on temperature and magnetic field as e.g. NbTi, but also on the strain state of the strands inside the conductor. It is hence very important to be able to predict the mechanical deforma...
In this paper we study numerically the mechanical behaviour of wire ropes, particularly the influence of the geometrical configuration on the overall stiffness of the cables. Modelling the behaviour of a cable is a difficult problem, given the complexity of the geometrical layout, contact phenomena occurring among wires and possible yielding of the...
In Nb3Sn CIC conductors, the superconducting compound is distributed into fine filaments and embedded in a resistive matrix for electrical and thermal stability. Nb3Sn formation requires a solid state diffusion reaction at high temperature, which causes an Sn gradient inside the filaments. It is well known that the critical parameters vary with com...
We briefly review the most common methods to obtain equivalent properties and then consider full multiscale modelling. Both linear and nonlinear material behaviours are considered. The case of composites with periodic microstructure is dealt with in detail and an example shows the capability of the method. Particular importance is also given to non...
In this paper, we show some different concepts for the use of Artificial Neural Networks in modelling of composites and hierarchical structures. Starting from a relatively small set of suitable numerical experiments performed on a unit cell, a proper set of corresponding input–output data is created to train the network to identify the effective pr...
This paper presents a development of the usual generalized self-consistent method for homogenization of composite materials. The classical self-consistent scheme is appropriate for phases that are “disordered”, i.e. what is called “random texture”. In the case of both linear and non linear components, the self-consistent homogenization can be used...
Various multiscale methods are reviewed in the context of modelling mechanical and thermomechanical responses of composites.
They are developed both at the material level and at the structural analysis level, considering sequential or integrated kinds
of approaches. More specifically, such schemes like periodic homogenization or mean field approach...
This paper deals with homogenization of non linear fibre-reinforced composites in the coupled thermo-mechanical field. For this kind of structures, i.e. inclusions randomly dispersed in a matrix, the self consistent methods are particularly suitable to describe the problem. Usually, in the framework of the self consistent scheme the homogenized mat...
The modeling of the effects of bending on single strand DC performance (I<sub>C</sub>, n index) is presented for a bronze-route strand subjected to the same loading conditions as in an experiment performed at JAEA Naka, Japan [Y. Nunoya, , IEEE TAS 14 (2004) 1468-1472]. The strand is discretized in strand elements (SE) representing groups of twiste...
Recent experimental tests on the model coils have shown that the behavior of Nb<sub>3</sub>Sn based cables is not as good as expected on the basis of the characteristics evaluated for the uncabled strands. This degradation of the cable performance seems to be due to various factors, among which the strain state of the filaments due to bending and c...
In the paper we present the analysis of multi-scale composite “from bottom to top of the hierarchy”. At each step of the analysis
we update the values of material properties of homogeneous components and compute new effective material parameters. Two different
numerical techniques of homogenization in non-linear range, basing on numerical experimen...
Recent experimental results on the International Thermonuclear Experimental Reactor (ITER) Central Solenoid Model Coil and Insert Coil have shown that the critical characteristics measured on a single strand are significantly different from those of a cabled conductor. This performance degradation seems to be due mostly to the bending effects on th...
An accurate estimation of the strain state of a strand inside a coil is a crucial point in the prediction of Nb3Sn conductor performance, since Nb3Sn based strands show a strain-dependence of their critical parameters. To perform a numerical analysis of a superconducting coil it would be impossible to operate a spatial discretization fine enough to...
The THELMA (Thermal-Hydraulic-ELectro-MAg-netic) code has been developed with the aim of simulating the main aspects of superconductors to be used in the coils of the International Thermonuclear Experimental Reactor (ITER). An application of the code is presented here, where THELMA is used to simulate a single strand by considering, as cable elemen...
This paper is a further step towards the full analysis of the complex behaviour of contacting beams in the coupled thermo-electro-mechanical
field. Now we add to our previous work the coupling with the thermal field. The coupling between electric, mechanical and
thermal fields is manifested in: dependence of material parameters on the temperature,...
In this paper a 3D beam-to-beam contact element is presented, to deal with contact problems in the coupled electric - mechanical
fields. The beams are supposed to get in contact in a pointwise manner, the detection of the contact points and the computation
of all contributions are carried out using a fully symmetric treatment of the two beams. Conc...
In this paper the formulation of an electric–mechanical beam-to-beam contact element is presented. Beams with circular cross-sections are assumed to get in contact in a point-wise manner and with clean metallic surfaces. The voltage distribution is influenced by the contact mechanics, since the current flow is constricted to small contacting spots....
This paper refers to an element of a long-lasting research effort to tackle the electro-mechanical analysis of superconducting coils for ITER
The progress in advanced technology fields requires more and more sophisticated formulations to consider contact problems properly. This paper is devoted to the development of a new constitutive model for electrostatic-mechanical contacts, based on a micro–macro approach to describe the contact behaviour.
The electric-mechanical contact constitutiv...
A theoretical model of a beam of unidirectional composites—based on the homogenisation theory and a refined kinematical hypothesis—is used for the analysis of the influence of the helicoidal geometry of a superconducting strand triplet on its strain state. The triplet is the first cabling stage of the superconducting cables used to wind the coils o...
In the present concept of ITER fusion reactor the toroidal field and the central solenoid coils are made of Nb3Sn based strands with the cable-in-conduit-conductor (CICC) technology. It is well known that the critical parameters of the Nb3Sn strand material are strain sensitive; experimental investigations on short samples of basic strands and subs...
In this paper Artificial Neural Network with hidden layers is applied to define a constitutive relation sigma-epsilon in an incremental form. Then ANN is used to describe dependence of effective material parameters of a composite on physical and geometrical characteristics of micro components at the micro-structural level. Using classical tools of...
In this paper a model to deal with electric-mechanical contact problems in the framework of the FEM is presented. On the basis of some micro-mechanical studies, a new approach is developed to define the non-linear constitutive law that governs the normal force-displacement behaviour and the electric resistance of the contacting surfaces.
The objective of this article is to capture the macroscopic behavior of an assembly of elastic and inelastic disks in contact by means of a numerical homogenized constitutive relation. An important feature of this work is that the evolving yield surfaces at the macroscopic level are defined through a quasi-static frictional contact analysis of the...
The paper presents a procedure for the numerical computation of the global interstrand resistances measured between strands of superconducting multistrand cables. The procedure is based on a geometrical reconstruction of the cable strands geometries, which are used to generate an electrical equivalent DC lumped network. In this network, the strands...
In this paper a formulation to deal with the Finite Element modelling of coupled electric-mechanical contact resistance is presented. The electrical contact resistance is based on a micro-macro approach, i.e. the contacting surfaces are not considered as perfectly smooth, but are characterised at the microscopic level by the presence of valleys and...
In this paper a simple way to describe the effects of microscopic damage on the global behaviour of periodic composite materials is shown. The microscopic damage is interpreted as a local reduction in material stiffness as presented in Zohdi et al. [1]. Choosing the damage parameters in an opportune manner a great variety of different damage consti...
An analysis of a superconducting coil used in fusion devices reveals that a wide spec- trum of coupled physical problems should be taken into account during its design. This is also a good example of a general analysis of a hierarchical structure. Due to the large number of repetitive superconducting strands, the single cable can be considered as a...
: This paper presents the most recent research activity performed by the authors in the field of contact problems in superconducting coils. The research is related to the development of the coils for the experimental nuclear fusion machine "ITER". The results here summarized are related to the inter-strand electromechanical behavior and its depende...
In this paper the formulation of an electric-mechanical beam-to-beam contact element is presented. Beams with circular cross-sections are assu