Abstract Traditional surgical repair of ascending aortic pseudoaneurysm is complex, technically challenging, and associated with significant mortality. Although new minimally invasive procedures are ...rapidly arising thanks to the innovations in catheter-based technologies, the endovascular repair of the ascending aorta is still limited because of the related anatomical challenges. In this context, the integration of the clinical considerations with dedicated bioengineering analysis, combining the vascular features and the prosthesis design, might be helpful to plan the procedure and predict its outcome. Moving from such considerations, in the present study we describe the use of a custom-made stent-graft to perform a fully endovascular repair of an asymptomatic ascending aortic pseudoaneurysm in a patient, who was a poor candidate for open surgery. We also discuss the possible contribution of a dedicated medical images analysis and patient-specific simulation as support to procedure planning. In particular, we have compared the simulation prediction based on pre-operative images with post-operative outcomes. The agreement between the computer-based analysis and reality encourages the use of the proposed approach for a careful planning of the treatment strategy and for an appropriate patient selection, aimed at achieving successful outcomes for endovascular treatment of ascending aortic pseudoaneurysms as well as other aortic diseases.
The goal of the present work is to emphasize some intrinsic features of the three-dimensional beam model originally proposed by Simo Simo, J.C., 1985. A finite-strain beam formulation. The ...three-dimensional dynamic problem. Part I. Comput. Methods Appl. Mech. Eng. 49, 55–70 and to derive the model equations for the general finite-deformation case as well as for the finite-deformation small-strain case in a consistent but simpler way with respect to what it is generally done in the literature.
The influence of floc size and hydraulic detention time on the performance of a dissolved air flotation (DAF) pilot unit was investigated in the light of a known mathematical model. The following ...design and operational parameters were considered: the hydraulic detention time (tdcz) and hydraulic loading rate in the contact zone, the down-flow loading rate in the clarification zone, the particle size distribution (
d
F
), and the recirculation rate (
p
). As a reference for DAF performance analysis, the proposed
β.
td parameter from the above mentioned mathematical model was employed. The results indicated that tdcz is an important factor in DAF performance and that
d
F
and floc size are also determinants of DAF efficiency. Further,
β.
td was sensitive to both design and operational parameters, which were varied in the DAF pilot plant. The performance of the DAF unit decreases with increasing
β.
td values because a higher td (considering a fixed
β
) or a higher
β
(e.g., higher hydrophobicity of the flocs for a fixed td) would be necessary in the reaction zone to reach desired flotation efficiency.
In isogeometric analysis (IGA), the functions used to describe the CAD geometry (such as NURBS) are also employed, in an isoparametric fashion, for the approximation of the unknown fields, leading to ...an exact geometry representation. Since the introduction of IGA, it has been shown that the high regularity properties of the employed functions lead in many cases to superior accuracy per degree of freedom with respect to standard FEM. However, as in Lagrangian elements, NURBS-based formulations can be negatively affected by the appearance of non-physical phenomena that “lock” the solution when constrained problems are considered. In order to alleviate such locking behaviors, the Assumed Natural Strain (ANS) method proposed for Lagrangian formulations is extended to NURBS-based elements in the present work, within the context of solid-shell formulations. The performance of the proposed methodology is assessed by means of a set of numerical examples. The results allow to conclude that the employment of the ANS method to quadratic NURBS-based elements successfully alleviates non-physical phenomena such as shear and membrane locking, significantly improving the element performance.
A study on unfitted 1D finite element methods Auricchio, F.; Boffi, D.; Gastaldi, L. ...
Computers & mathematics with applications (1987),
December 2014, 2014-12-00, 20141201, Letnik:
68, Številka:
12
Journal Article
Recenzirano
Odprti dostop
In the present paper we consider a 1D Poisson model characterized by the presence of an interface, where a transmission condition arises due to jumps of the coefficients. We aim at studying finite ...element methods with meshes not fitting such an interface. It is well known that when the mesh does not fit the material discontinuities the resulting scheme provides in general lower order accurate solutions. We focus on so-called embedded approaches, frequently adopted to treat fluid–structure interaction problems, with the aim of recovering higher order of approximation also in presence of non fitting meshes; we implement several methods inspired by: the Immersed Boundary method, the Fictitious Domain method, and the Extended Finite Element method. In particular, we present four formulations in a comprehensive and unified format, proposing several numerical tests and discussing their performance. Moreover, we point out issues that may be encountered in the generalization to higher dimensions and we comment on possible solutions.
Abstract
During the planning computed tomography (CT) scan, patients experience the position and any immobilisation technique required for radiotherapy.
Patient’s stress and anxiety can cause muscle ...tension that can introduce systematic set-up errors if not recognised and corrected.
We discuss two clinical cases that highlight the importance of time dedicated to communication and revision of the first CT acquisition during a virtual simulation procedure.
In the last 20 years, a new approach has emerged to investigate the physiopathology of circulation. By merging medical images with validated numerical models, it is possible to support doctors’ ...decision-making process. The iCardioCloud project aims at establishing a computational framework to perform a complete patient-specific numerical analysis, specially oriented to aortic diseases (like dissections or aneurysms) and to deliver a compelling synthesis. The project can be considered a pioneering example of a Computer Aided Clinical Trial: i.e., a comprehensive analysis of patients where the level of knowledge extracted by traditional measures and statistics is enhanced through the massive use of numerical modeling. From a computer engineering point of view, iCardioCloud faces multiple challenges. First, the number of problems to solve for each patient is significantly huge – this is typical of computational fluid dynamics (CFD) – and it requires parallel methods. In addition, working in a clinical environment demands efficiency as the timeline requires rapid quantitative answers (as may happen in an emergency scenario). It is therefore mandatory to employ high-end parallel systems, such as large clusters or supercomputers.
Here we discuss a parallel implementation of an application within the iCardioCloud project, built with a black-box approach – i.e., by assembling and configuring existing packages and libraries and in particular LifeV, a finite element library developed to solve CFD problems. The goal of this paper is to describe the software architecture underlying LifeV and to assess its performance and the most appropriate parallel paradigm.
This paper is an extension of a previous work presented at the PBio 2015 Conference. This revision extends the description of the software architecture and discusses several new serial and parallel optimizations to the application. We discuss the introduction of hybrid parallelism in order to mitigate some performance problems previously experienced.
PDF
