Mixing Snapshots and Fast Time Integration of PDEs

A local proper orthogonal decomposition (POD) plus Galerkin projection method was recently developed to accelerate time dependent numerical solvers of PDEs. This method is based on the combined use of a numerical code (NC) and a Galerkin sys- tem (GS) in a sequence of interspersed time intervals, INC and IGS, respectively. POD is performed on some sets of snapshots calculated by the numerical solver in the INC inter- vals. The governing equations are Galerkin projected onto the most energetic POD modes and the resulting GS is time integrated in the next IGS interval. The major computa- tional e®ort is associated with the snapshots calculation in the ¯rst INC interval, where the POD manifold needs to be completely constructed (it is only updated in subsequent INC intervals, which can thus be quite small). As the POD manifold depends only weakly on the particular values of the parameters of the problem, a suitable library can be con- structed adapting the snapshots calculated in other runs to drastically reduce the size of the ¯rst INC interval and thus the involved computational cost. The strategy is success- fully tested in (i) the one-dimensional complex Ginzburg-Landau equation, including the case in which it exhibits transient chaos, and (ii) the two-dimensional unsteady lid-driven cavity proble

Perceptions of the Host Country’s food culture among female immigrants from Africa and Asia: Aspects relevant for culture sensitivity in nutrition communication

Objective: To explore how female immigrants from Africa and Asia perceive the host country’s food culture, to identify aspects of their original food culture they considered important to preserve, and to describe how they go about preserving them. Design: Qualitative in-depth interviews. Setting: Oslo, Norway. Participants: Twenty one female immigrants from 11 African and Asian countries, residing in areas of Oslo with a population having a low-to-middle socioeconomic status and a high proportion of immigrants. Participants varied in years of residence, employment status, and marital status. Analysis: Analysis of the interviews was guided by a phenomenological approach. Results: Participants emphasized the importance of preserving aspects of their original food cultures and related these aspects to taste, preparation effort and method, and adherence to religious dietary rules. They often perceived the food of the host country as ‘‘tasteless and boring.’’ The authors observed strict, flexible, or limited continuity with the original food culture. Some elements that possibly influenced participants’ degree of continuity are indicated. Conclusions and Implications: Immigrants may strive to preserve aspects of their original food culture after immigration. Nutrition communication becomes more culturally sensitive when it takes such aspects into accoun

Systematic mapping review of the factors influencing dietary behaviour in ethnic minority groups living in Europe: A DEDIPAC study

.Background: Europe has a growing population of ethnic minority groups whose dietary behaviours are potentially of public health concern. To promote healthier diets, the factors driving dietary behaviours need to be understood. This review mapped the broad range of factors influencing dietary behaviour among ethnic minority groups living in Europe, in order to identify research gaps in the literature to guide future research. Methods: A systematic mapping review was conducted (protocol registered with PROSPERO 2014: CRD42014013549). Nine databases were searched for quantitative and qualitative primary research published between 1999 and 2014. Ethnic minority groups were defined as immigrants/populations of immigrant background from low and middle income countries, population groups from former Eastern Bloc countries and minority indigenous populations. In synthesizing the findings, all factors were sorted and structured into emerging clusters according to how they were seen to relate to each other. Results: Thirty-seven of 2965 studies met the inclusion criteria (n = 18 quantitative; n = 19 qualitative). Most studies were conducted in Northern Europe and were limited to specific European countries, and focused on a selected number of ethnic minority groups, predominantly among populations of South Asian origin. The 63 factors influencing dietary behaviour that emerged were sorted into seven clusters: social and cultural environment (16 factors), food beliefs and perceptions (11 factors), psychosocial (9 factors), social and material resources (5 factors), accessibility of food (10 factors), migration context (7 factors), and the body (5 factors). Conclusion: This review identified a broad range of factors and clusters influencing dietary behaviour among ethnic minority groups. Gaps in the literature identified a need for researchers to explore the underlying mechanisms that shape dietary behaviours, which can be gleaned from more holistic, systems-based studies exploring relationships between factors and clusters. The dominance of studies exploring 'differences' between ethnic minority groups and the majority population in terms of the socio-cultural environment and food beliefs suggests a need for research exploring 'similarities'. The evidence from this review will feed into developing a framework for the study of factors influencing dietary behaviours in ethnic minority groups in Europe

Reduced order modeling of some fluid flows of industrial interest

Some basic ideas are presented for the construction of robust, computationally efficient reduced order models amenable to be used in industrial environments, combined with somewhat rough computational fluid dynamics solvers. These ideas result from a critical review of the basic principles of proper orthogonal decomposition-based reduced order modeling of both steady and unsteady fluid flows. In particular, the extent to which some artifacts of the computational fluid dynamics solvers can be ignored is addressed, which opens up the possibility of obtaining quite flexible reduced order models. The methods are illustrated with the steady aerodynamic flow around a horizontal tail plane of a commercial aircraft in transonic conditions, and the unsteady lid-driven cavity problem. In both cases, the approximations are fairly good, thus reducing the computational cost by a significant factor

A preliminary experimental and numerical analysis of hybrid CFRP aluminum tubes under dynamic axial loading

LAUREA MAGISTRALEIl seguente lavoro tratta l’analisi del comportamento a crash di tubi ibridi metello-composito, nello specifico il comportamento di assorbimento di energia durante un impatto assiale. È stato ispezionato il comportamento di un tubo in alluminio rinforzato tramite laminazione di pre-impregnati in fibra di carbonio. Lo studio si è diviso in test sperimentali utilizzando il sistema “torre di caduta”, in differenti configurazioni di laminazione, e la correlazione del comportamento tramite simulazioni numeriche. Tutte le configurazioni sono state simulate tramite il codice ad elementi finiti LS-Dyna.The following study addresses the problem of analysing the behaviour of a hybrid composite-metal component, especially in the axial crush absorbing energy field. An aluminium circular tube coupled with Carbon Resin Fibre Plastic (CFRP) lamination was investigated. The study is divided in two, an experimental campaign of different tube configurations using a drop tower testing system and numerical simulations in order to capture and correlate the dynamic of the crushing process. Each configuration has been reproduced and simulated in the finite element code LS-Dyna

Poroelastic computational modeling of biological tissues. Application to the mechanics of the eye

LAUREA MAGISTRALEQuesta tesi si occupa dell'applicazione della teoria della poroelasticità a tessuti biologici costituiti da un mezzo poroso elastico e da un fluido che occupa lo spazio lasciato dai pori. Per la risoluzione numerica di problemi poroelastici, viene proposto un algoritmo iterativo dotato di rilassamento e interpretabile come metodo di punto fisso. Tale algoritmo, basato sul metodo degli elementi finiti relativamente alla discretizzazione in spazio e sul metodo di Eulero implicito relativamente alla discretizzazione in tempo, è implementato in MATLAB nei casi 1D e 2D ed è analizzato per determinarne le proprietà di convergenza. Diverse simulazioni numeriche sono eseguite con l'obiettivo di validare il codice. Viene presentata un'applicazione alla biomeccanica e all'emodinamica dell'occhio umano, corrispondente a un modello poroelastico per la lamina cribrosa, una struttura di collagene situata nella testa del nervo ottico di grande interesse per lo studio di diverse patologie, come il glaucoma. I risultati numerici mostrano come valori elevati di pressione intraoculare, che costituiscono il principale fattore di rischio per il glaucoma, implichino significativi sforzi e deformazioni e una diminuzione di porosità nelle regioni di bordo della lamina cribrosa, dove è noto che ha inizio il danno associato al glaucoma.This thesis deals with the application of the theory of poroelasticity to biological tissues formed by an elastic porous medium and a fluid saturating the porous space. A relaxed fixed point iteration algorithm is proposed for the numerical solution of poroelastic problems. This algorithm, based on the finite element method for space discretization and the backward Euler method for time discretization, is implemented in MATLAB in both 1D and 2D cases and is analysed to investigate its convergence properties. Several numerical simulations are run in order to validate the code. An application to ocular biomechanics and hemodynamics is presented, describing a poroelastic model for the lamina cribrosa, a collagen structure in the optic nerve head which is of great interest for the study of several ocular diseases, such as glaucoma. Numerical results reveal that high values of intraocular pressure, which are the main risk factor for glaucoma, lead to high stresses and strains and to a decrease of porosity in the boundary regions of the lamina cribrosa, where the glaucomatous damage is known to start