Designing manufacturable viscoelastic devices using a topology optimization approach within a truly-mixed fem framework

A new approach to topology optimization is presented that is based on the minimization of the input/output transfer function H∞norm. Additionally, by properly selecting input and output vector, the approach is recognized to minimize an entirely new definition of frequency-based dynamic compliance. The method is applied to viscoelastic systems in plane strain conditions that are investigated by using the Arnold-Winther finite-element resorting to a generalized solid phenomenological model. Preliminary indications on how to address the actual manufacturability of the optimal specimen are eventually outlined

Mixed variational formulations for micro-cracked continua in the multifield framework

Within the framework of multifield continua, we move from the model of elastic microcracked body introduced in (Mariano, P.M. and Stazi, F.L., Strain localization in elastic microcracked bodies, Comp. Methods Appl. Mech. Engrg. 2001, 190, 5657–5677) and propose a few novel variational formulations of mixed type along with relevant mixed FEM discretizations. To this goal, suitably extended Hellinger-Reissner principles of primal and dual type are derived. A few numerical studies are presented that include an investigation on the interaction between a single cohesive macrocrack and diffuse microcracks (Mariano, P.M. and Stazi, F.L., Strain localization due to crack–microcrack interactions: X–FEM for a multifield approach, Comp. Methods Appl. Mech. Engrg. 2004, 193, 5035–5062)

Parola parlata: convenzioni e tecniche di resa nella narrativa araba classica

Numero monografico: L’oralità nella scrittura. Modalità di rappresentazione della parola orale nel testo scritto”, a cura di Maria Teresa Biaso

Static and dynamic topology optimization: an innovative unifying approach

This paper presents a topology optimization approach that is innovative with respect to two distinct matters. First of all the proposed formulation is capable to handle static and dynamic topology optimization with virtually no modifications. Secondly, the approach is inherently a multi-input multi-output one, i.e., multiple objectives can be pursued in the presence of multiple loads. The input-to-output transfer matrix, say G, is the key ingredient that governs the algebraic mapping between applied loads and structural response. In statics G depends on the design variables only, whereas it depends on the frequency variable as well in the dynamic case. The Singular Value Decomposition (SVD) of G represents then the core of the proposed approach. Singular values are shown to be the gains of the input/output mapping and are used to compute proper norms of G that represent the goal functions to be minimized. Singular vectors provide at no extra cost the plant directions, i.e., the load combination factors that stress the structure the most. Numerical examples are discussed in much detail and open issues object of ongoing investigations are highlighted. A full Matlab code handling the static topology optimization problem is provided as an online Appendix to the manuscript. Its extension to the dynamic case may be gathered following the formulation proposed in Sect. 5

Mixed methods for viscoelastodynamics and topology optimization

A truly-mixed approach for the analysis of viscoelastic structures and continua is presented. An additive decomposition of the stress state into a viscoelastic part and a purely elastic one is introduced along with an Hellinger-Reissner variational principle wherein the stress represents the main variable of the formulation whereas the kinematic descriptor (that in the case at hand is the velocity field) acts as Lagrange multiplier. The resulting problem is a Differential Algebraic Equation (DAE) because of the need to introduce static Lagrange multipliers to comply with the Cauchy boundary condition on the stress. The associated eigenvalue problem is known in the literature as constrained eigenvalue problem and poses several difficulties for its solution that are addressed in the paper. The second part of the paper proposes a topology optimization approach for the rationale design of viscoelastic structures and continua. Details concerning density interpolation, compliance problems and eigenvalue-based objectives are given. Worked numerical examples are presented concerning both the dynamic analysis of viscoelastic structures and their topology optimization

¿Quin tipus de preguntes fem als nostres alumnes?

Utilitzant un tipus de preguntes variat, sempre d’acord amb els objectius instructius proposats, ajudarem els nostres alumnes a pensar, més que a recordar. Hi ha molts escolars que no estan acostumats a reflexionar, menys encara a expressar al professor els seus pensaments. Variar la categoria de les preguntes que fem a la classe ens permetrà obtenir una informació més completa sobre l’evolució del procés d’aprenentatge i millorar la qualitat de l’ensenyança

Carthago. Il porto antico e il nuovo museo archeologico

LAUREA MAGISTRALESulla costa settentrionale dell’Africa, alla periferia di Tunisi, giacciono le rovine dell’antica Cartagine. Fondata dai Fenici, Cartagine è un sito archeologico esteso, situato su una collina che domina il golfo di Tunisi. Metropoli della colonizzazione Punica in Africa e capitale della provincia dell’Africa ai tempi degli antichi romani, Cartagine ha avuto un ruolo centrale nell’antichità quale grande impero commerciale. Luogo eccezionale di diverse culture che si sono susseguite nei secoli, attualmente parco archeologico di Cartagine, valorizza monumenti eretti nel corso di oltre 3000 anni. L’area di intervento dove si andrà a sviluppare il progetto è compresa nell’area dei porti della Cartagine punica,attualmente rintracciabili come ingombro generale. Nel porto circolare sono ancora oggi in evidenza le fondamenta dei moli, della cinta muraria e le tracce di una serie di darsene di carenaggio. Il progetto mira a riconnettere il parco archeologico con l’area dei porti punici,inglobata all’interno dell’urbanizzazione e spesso dimenticata, stabilendo una nuova identità grazie a degli elementi attrattori che si traducono nella realizzazione di un nuovo porto sulle tracce storiche attraverso un ridisegno dei confini e nella realizzazione del nuovo museo archeologico di cartagine. L’introduzione di nuove architetture nel sistema del Parco Archeologico, mira a garantire la fruizione e l’interesse da parte del pubblico. Il progetto intende quindi dare un nuovo valore all’archeologia tunisina, nel contesto del parco archeologico, diventando punto focale in questo luogo che sin dal passato, ha avuto ruolo focale nel mediterraneo

Modal identification of storage racks for cheese wheels

During the Emilia-Romagna earthquake (2012), a great number of steel racks used to store cheese wheels collapsed, causing a non-negligible damage to the Italian economy. Therefore, for similar structures that survived and are in service, a deep investigation towards the assessment of their effective safety is required. In the seismic analysis of these frames, the mechanical constraint acting onto the racks due to the reinforced concrete sidewalls, possible nonlinearities exhibited by the base-plate joints and the in-plane restraint provided by wooden boards that connects adjacent columns should be carefully modelled to ensure realistic design results. In the paper, an experimental activity, based on suitable modal identification techniques, is presented to capture the dynamic behaviour of these peculiar structures. The scope is to collect data useful to calibrate numerical finite element models in order to accurately define the aforementioned unknown parameters. Furthermore, a few numerical models based on ideal restraints are herein discussed stressing out non-negligible differences in terms of expected seismic and static response

Agilität im Mathematikunterricht der Primarstufe. Entwicklung und Evaluation eines agilen Unterrichtsinstruments

Aktuell verschliesst sich kaum eine grössere Unternehmung der Agilität und auch öffentliche Organisationen bemühen sich zunehmend um agilere Prozesse. So verwundert es nicht, dass seit wenigen Jahren Agilität auch im Bildungsbereich Fuss zu fassen scheint. Darüber hinaus wurde bereits vereinzelt versucht, Agilität ins Klassenzimmer zu tragen und den Unterricht agil zu gestalten. Es fällt jedoch auf, dass eine einheitliche Definition zu fehlen scheint. Zwar verspricht man sich positive Effekte bezüglich Effektivität, Dynamik, Selbststeuerung, Motivation, Eigenverantwortung, Fehlerkultur usw., doch was mit dieser «Agilität» genau gemeint ist, die all dies erreichen will, bleibt oft unbeantwortet. Durch eine vertiefte Literaturrecherche wurde in einem ersten Schritt zusammengetragen, was unter Agilität verstanden wird. Auch hier bleibt die Suche nach einem einheitlichen Verständnis erfolglos. Je nachdem, ob von Personalführung oder von Produktionsprozessen gesprochen wird, finden sich unterschiedliche Konzepte. Dennoch war es möglich, zentrale Prinzipien zu formulieren, welche in vielen Auffassungen eine bedeutende Rolle spielen. In einem zweiten Schritt wurde diese Synthese in fünf Punkten auf den Kontext Schule und Unterricht übersetzt. Während manche Autoren bei dieser Übersetzungsleistung beinahe hemmungslos den Terminus «Chef» durch «Lehrperson» und «Kunde» durch «Schüler» ersetzen, wurde hier sorgfältig begründet, weshalb die Anwendung der Prinzipien aus pädagogischer Perspektive im Unterricht sinnvoll scheinen. Dies wurde anschliessend mittels einer entwickelten Lektionsreihe an Schweizer Primarschulen erprobt. (Autorin