1,855 research outputs found
A Florentine family in crisis: the Strozzi in the fifteenth century.
No full textPhDIn 1434 the Strozzi lineage had held a leading position in
Florentine society and government for at least one hundred and fifty
years, and was one of the largest and wealthiest of the city's
patrician lineages. The records of the catasto of 1427 and of the
scrutiny of 1433 are used to give a profile of the dominant social,
economic and political position of the Strozzi before the advent of
Medicean dominance. Their record of electoral success, and the
political and cultural leadership of influential and respected men
such as Palla di Nofri and Matteo di Simone, with other factors, put
the Strozzi amongst the greatest enemies of the victorious Medicean
regime of late 1434. The effects of political opposition and exile
on the lineage are examined both directly, through records of office-holding,
and indirectly through such indicators as marriage alliances
and household wealth. The two most prominent lines of the Strozzi
were exiled after 1434. Palla di Nofri's life and preoccupations in
his Paduan exile are examined, together with the lives of his sons;
none of these Strozzi ever returned to Florence, pursued as they were
by the enmity of the Medicean regime. The very different careers of
Filippo di Matteo and his brother Lorenzo are also examined: how they
succeeded in founding a lucrative bank in Naples, and in returning to
Florence to 'rebuild' (rifare) the position of the Strozzi lineage
there. The final decades of the century saw the Strozzi in an
economically more secure position, due substantially to the efforts
of Filippo. Except for a very small number of its members admitted
into the regime, most of the lineage is here shown to have remained
excluded from significant political office until after the fall of
the Medici regime in 1494
Applicability and Limitations of Ru’s Formulation for Vibration Modelling of Double-Walled Carbon Nanotubes
No full textIn this paper, a comparison is conducted between two different formulations of the van der Waals interaction coefficient between layers, as applied to the vibrations of double-walled carbon nanotubes (DWCNTs); specifically, the evaluation of the natural frequencies is achieved through Ru’s and He’s formulations. The actual discrete DWCNT is modelled by means of a couple of concentric equivalent continuous thin cylindrical shells, where Donnell shell theory is adopted to obtain strain-displacement relationships. In order to take into account the chirality effect of DWCNT, an anisotropic elastic shell model is considered. Simply supported boundary conditions are imposed and the Rayleigh–Ritz method is used to obtain approximate natural frequencies and mode shapes. A parametric analysis considering different values of diameters and numbers of waves along longitudinal and circumferential directions is performed by adopting Ru’s and He’s formulations. From the comparisons, it is evident that Ru’s formulation provides unsatisfactory results for relatively low values of diameters and relatively high numbers of circumferential waves with respect to the more accurate He’s formulation. This behaviour is observed for every number of longitudinal half-waves. Therefore, Ru’s formulation cannot be used for the vibration modelling of DWCNTs in a large range of diameters and wavenumbers
Linear vibrations of triple-walled carbon nanotubes
No full textIn this paper, the linear vibrations of triple-walled carbon nanotubes (TWNTs) are investigated. A multiple elastic thin shell model is applied. The TWNT dynamics is studied in the framework of the Sanders–Koiter shell theory. The van der Waals interaction between any two layers of the TWNT is modelled by a radius-dependent function. The shell deformation is described in terms of longitudinal, tangential and radial displacements. Simply supported, clamped and free boundary conditions are applied. The three displacement fields are expanded by means of a double mixed series based on Chebyshev polynomials for the longitudinal variable and harmonic functions for the tangential variable. The Rayleigh–Ritz method is applied to obtain approximate natural frequencies and mode shapes. The present model is validated in the linear field by means of comparisons with data from the literature. This study is focused on determining the effect of geometry and boundary conditions on the natural frequencies of TWNTs
Nonlinear vibrations of functionally graded circular cylindrical shells subjected to harmonic external load
No full textThe nonlinear vibrations of functionally graded (FGM) circular cylindrical shells are analysed. The Sanders-Koiter theory is applied in order to model the nonlinear dynamics of the system. The shell deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported boundary conditions are considered. The displacement fields are expanded by means of a double mixed series based on Chebyshev polynomials for the longitudinal variable and harmonic functions for the circumferential variable. Both driven and companion modes are considered. Numerical analyses are carried out in order to characterize the nonlinear response when the shell is subjected to a harmonic external load. A convergence analysis is carried out to obtain the correct number of axisymmetric and asymmetric modes describing the actual nonlinear behaviour. The influence of the material distribution on the nonlinear response is analysed considering different configurations and volume fractions of the constituent materials. The effect of the companion mode participation on the nonlinear response of the shell is analysed
Nonlinear vibration of functionally graded cylindrical shells: effect of constituent volume fractions and configurations
No full textIn this paper, the nonlinear vibration of functionally graded (FGM) cylindrical shells under different constituent volume fractions and configurations is analyzed. The Sanders-Koiter theory is applied to model nonlinear dynamics of the system in the case of finite amplitude of vibration. The shell deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported boundary conditions are considered. Displacement fields are expanded by means of a double mixed series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. Both driven and companion modes are also considered, allowing for the travelling-wave response of the shell. The functionally graded material considered is made of stainless steel and nickel, properties are graded in the thickness direction according to a real volume fraction power-law distribution. In the nonlinear model, shells are subjected to an external radial excitation. Nonlinear vibrations due to large amplitude of excitation are considered. Specific modes are selected in the modal expansions; a dynamical nonlinear system is then obtained. Lagrange equations are used to reduce nonlinear partial differential equations to a set of ordinary differential equations, from the potential and kinetic energies, and the virtual work of the external forces. Different geometries are analyzed; amplitude-frequency curves are obtained. Convergence tests are carried out considering a different number of asymmetric and axisymmetric modes. The present model is validated in linear field (natural frequencies) by means of data present in the literature
Nonlinear vibrations of functionally graded cylindrical shells
No full textIn this paper, the nonlinear vibrations of functionally graded (FGM) circular cylindrical shells are analysed. The Sanders–Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The shell deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported, clamped and free boundary condi- tions are considered. The displacement fields are expanded by means of a double mixed series based on Chebyshev orthogonal polynomials for the longitudinal variable and harmonic functions for the circumferential variable. Both driven and companion modes are considered; this allows the travelling- wave response of the shell to be modelled. The model is validated in the linear field by means of data retrieved from the pertinent literature. Numerical analyses are carried out in order to characterise the nonlinear response when the shell is subjected to a harmonic external load; a convergence analysis is carried out by considering a variety of axisymmetric and asymmetric modes. The present study is focused on determining the nonlinear character of the shell dynamics as the geometry (thickness, radius, length) and material properties (constituent volume fractions and configurations of the constituent materials) vary
Damping Oriented Design of Thin-Walled Mechanical Components by Means of Multi-Layer Coating Technology
No full textThe damping behaviour of multi-layer composite mechanical components, shown by recent research and application papers, is analyzed. A local dissipation mechanism, acting at the interface between any two different layers of the composite component, is taken into account, and a beam model, to be used for validating the known experimental results, is proposed. Multi-layer prismatic beams, consisting of a metal substrate and of some thin coated layers exhibiting variable stiffness and adherence properties, are considered in order to make it possible to study and validate this assumption. A dynamical model, based on a simple beam geometry but taking into account the previously introduced local dissipation mechanism and distributed visco-elastic constraints, is proposed. Some different application examples of specific multi-layer beams are considered, and some numerical examples concerning the beam free and forced response are described. The influence of the multilayer system parameters on the damping behaviour of the free and forced response of the composite beam is investigated by means of the definition of some damping estimators. Some effective multi-coating configurations, giving a relevant increase of the damping estimators of the coated structure with respect to the same uncoated structure, are obtained from the model simulation, and the results are critically discussed.</jats:p
Manuale per la lean excellence. Guida alla trasformazione aziendale ed all'applicazione pratica del pensiero snello
No full textWhen I wrote the original Toyota Way in 2003 I was trying to correct a major
misunderstanding. Most books about lean were describing a litany of tools. Do 5S, set
up cells, design a kanban system, install an Andon system to stop the line for quality problems, and more. Every new idea became a tool. Hoshin Kanri automatically
meant fill out an X-matrix. Standardized work meant find the proper form and fill in
the steps and times. Even an organizational design change like work groups were
something to install. In fact many companies still judge the “leanness” of an operation by auditing relative to a checklist of lean tools. The message was do these things
and you will be lean. And the goal was to do them as quickly as possible as broadly as
possible. “Lean conversions” meant that you had installed all this lean stuff and got a
good grade on the checklist.
In the meantime I had been studying Toyota for almost twenty years and the
message they gave was the exact opposite. The Toyota Production System is not
about implementing tools, but about developing people to strive for excellence, by
experimenting and learning. One-piece flow is an ideal to strive for-perfect, uninterrupted flow to the customer without waste. People must learn to set high, even seemingly unachievable goals in that direction and be persistent in working to achieve
them. Along the way various tools will be useful but the specific ones, their timing,
and their sequence will vary depending on the situation. You do not send a carpenter
out to first do a bunch of hammering, and then go through and screw in a bunch of
things in for a while, and hope the result is a house. Similarly the TPS house cannot be
build by poorly trained people whose main skill is they learned how the tool works
from a book or short course. They need a level of mastery of the art of lean to achieve
the critical goals of the organization, whatever those are
Quantitative methods for quality management
No full textThis book is intended to offer a theoretical support and a practical guide to understand and use a wide set of quantitative tools for Quality Management. The most common tools and methods are first explained and then applied in industrial examples: Basic Statistics, Graphical Approach, Pareto, Hypothesis Testing, ANOVA, DoE, Control Chart, Acceptance Sampling are some of the covered topics. The goal of this book is to provide the readers both with theory recall and examples of application to understand the approach and master the application. Thus the book is projected to be a useful resource for both students and practitioners in manufacturing and service operations. Students will find the ideal support and guidance for getting confident with the subject, while practitioners will be provided with theoretical and practical insights to deeply understand the ground on which most of commonly used quality tools are built on. The book will explain the topics starting from the easiest-to-understand, gradually increasing the level of complexity in the tools and in the numerical examples. This third edition of the book has widened the theory support and re-organized the topics. This new organization will both support a deeper understanding of the statistical basics and facilitate the mastering of the more complex quality tools
Manuale Six Sigma per le Green Belt
No full textLa gestione della qualità passa per il miglioramento dei processi aziendali. Il Six Sigma si è dimostrato essere uno dei sistemi più efficaci per raggiungere l’eccellenza operativa, grazie ai risultati raggiunti sia dalle grandi multinazionali, sia dalle aziende più piccole pronte al cambiamento. Grazie alla rivoluzionaria combinazione di organizzazione, metodo, gestione dei progetti, strumenti qualitativi e strumenti quantitativi, il Six Sigma ha definito un organismo vincente innovazioni dei processi e la gestione del miglioramento. Questo manuale offre una panoramica completa sul Six Sigma, una guida pratica utilizzo del metodo email e degli strumenti per la risoluzione dei problemi e innovazione dei processi ed una serie di casi aziendali esemplari per toccare con mano i risultati ottenuti in diversi settori. Per la vastità e la completezza dei temi trattati il manuale è un valido supporto per contenimento della certificazione Green Belt
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