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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Production and excitation of cold Ps for anti-H formation by charge exchange: towards a gravitational measurement on antimatter

Guatieri, Francesco January 2018 (has links)
The AEgIS experiment pursues the ambitious goal of measuring for the first time the gravitational pull on neutral antimatter. The envisioned method consists in producing a beam of cold anti-hydrogen and measuring the deflection of its free fall by means of a Moiré deflectometer. To do so the pulsed production of abundant cold anti-hydrogen is paramount, therefore the charge exchange production mechanism has been elected as the most promising candidate production method. Performing the charge exchange anti-hydrogen production requires access to an abundant source of cold positronium which can be achieved by the employment of oxide-coated nanochanneled silica plates (NCPs). We spend chapter 1 formulating a classical model of positronium production and thermalisation in NCPs and validating it by testing it against the available experimental data. In chapter 2 we describe the measurement of the energy spectrum of positronium produced by nanochanneled plates using the beam produced by the SURF machine. We then compare the measured energy spectra with the model proposed in chapter 1 showing, in the comparison, the indication of a transition during thermalisation process to a regime where quantum phenomena become significant. We describe in detail in chapter 3 several positronium spectroscopy measurements that we performed during the course of the last three years by employing the positron beam line of the experiment AEgIS. We will the proceed to illustrate an improved version of the detrending technique commonly employed in signal analysis which, applied to the analysis of SSPALS spectra, improves the achievable precision on the experimental results. In chapter 4 we describe an innovative approach that we are currently pursuing to employ the detector FACT, part of the AEgIS apparatus, to confirm the successful production of anti-hydrogen.
62

Selected Topics in Analysis in Metric Measure Spaces

Capolli, Marco 02 February 2021 (has links)
The thesis is composed by three sections, each devoted to the study of a specific problem in the setting of PI spaces. The problem analyzed are: a C^m Lusin approximation result for horizontal curves in the Heisenberg group, a limit result in the spirit of Burgain-Brezis-Mironescu for Orlicz-Sobolev spaces in Carnot groups and the differentiability of Lipschitz functions in Laakso spaces.
63

Numerical Modelling of Braiding Processes in Gravel-Bed Rivers

Baral, Bishnu Raj January 2018 (has links)
Gravel-bed braided rivers are distinctive natural environments that provid a wide range of key environmental, economic and recreational services. There is, however,a growing concern that over the twentieth century, an increasing number of braided rivers have metamorphosed into wandering or single thread channels, representing a loss of key habitats, geodiversity and amenity. While in some situations, shifts in channel pattern may be unambiguously linked to abrupt changes in flow or sediment supply, the lack of a theoretical basis underpinning the development and maintenance of braiding makes identification of the cause and effect of channel metamorphosis hazardous. A growing body of research has suggested that the transition between channelpatterns may depend on the poorly understood interaction between the flow regime,sediment supply and vegetation colonisation. Such interactions are governed by critical thresholds, due to changes in flow resistance and bank strength associated with the distribution, form and intensity of vegetation colonisation. Subtle changes in flow or sediment supply that promote vegetation growth or indeed remove itthrough inundation or attrition. This can lead to complex non-linear shifts in the balance of forces that govern sediment transport and bedform morphodynamics, ultimately resulting in one-way changes in channel morphology. There is, therefore, a critical need to develop a quantitative understanding of these feedbacks in orderto design sustainable river management programmes that seek to optimize the ecological and socio-economic benefits these rivers offer. In summary, this thesis aims to advance our understanding of the morphodynamics of braided rivers and the role numerical models may have in helping to interrogate their behavior and governing controls.
64

Development of an efficient fluid-structure interaction model for floating objects

Brutto, Cristian 18 June 2024 (has links)
This thesis gives an overview of the process that led to the development of a novel semi-implicit fluid-structure interaction model. The thesis is dedicated to the creation of a new numerical model that allows to study ship generated waves and ship manoeuvers in waterways for various vessel characteristics and speeds in different external current situations. A model like this requires a coupling between the fluid and the solid to generate the waves and the hydrodynamic forces on the hull. Since the horizontal dimensions are significantly larger than the vertical dimension, we started by employing the shallow water equations, which are based on the assumption of hydrostatic pressure. The discretization was carried out taking only the nonlinear advective terms explicitly while the pressure terms are discretized implicitly, which makes the CFL condition milder. The price to pay for this semi-implicit discretization is an increase in the algorithm complexity compared to a fully-explicit method, but it is still much simpler than a fully-implicit discretization of the governing equations. Indeed, the mass and momentum equations couple, and finding the unknowns involves solving a system of equations with dimensions equal to the number of cells. The grid supporting the discretization is staggered, overlapping and Cartesian. Since the aimed application domain is inland waterways, it is paramount to allow wetting and drying of the cells. This was achieved by acting on the depth function, the relationship between the free-surface elevation and the water depth in the cell. The main novelty of this research project is the two-way coupling of the PDE system for the water flow with the ODE system for the rigid body motion of the ship. The hull defines the ship region, and its shape can range from a simple box to an STL file of a real 3D ship geometry. Where the hull is in contact with the water, the cells are pressurized. This pressurized group of cells generates waves as it moves, and its motion is influenced by incoming external waves. This result is obtained by imposing an upper bound to the depth function, so that the water depth does not increase when it reaches the hull elevation, while the pressure is allowed to increase. This upper bound increases the nonlinearity of the system, which may have dry cells, wet free-surface cells and pressurized cells. The solution of this system is found by a single nested-Newton iterative solver of Casulli and Zanolli [36], in which with two separate linearizations the system is written in a sparse, symmetric, positive semi-definite form. This particular form allows us to employ a matrix-free conjugate gradient method, and efficiently get the unknown pressure. The integral of the pressure over the hull is applied for the hydrodynamic force and torque acting on the ship. After adding the skin friction and other external forces from the propeller or the rudder, the total force is inserted in the equation of motion of the rigid body. The ODE system is discretized with a second-order Taylor method, and it is solved for the six degrees of freedom (3 coordinates for the position vector of the barycenter and 3 rotation angles), providing the next position and orientation of the ship. The vertical translation of the rigid body is governed by the gravitational force and the restoring force from Archimedes' principle. As the ship oscillates up and down, the gravitational potential energy is partially transferred to the radiated free-surface water waves, damping and eventually stopping the motion. Also, the ship pushes and pulls the water around it, inducing the added mass force. All these elements constitute the ODE that was used for the verification of the vertical degree of freedom. The numerical simulation gave the expected results for the vertical motion. The horizontal translation, important for the manoeuvers, presented a numerical instability unseen in our previous test cases, which is connected to the relative motion between the ship and the grid. In each time step in which the ship enters a new cell, the pressure sharply increases and decreases at the ship bow. An oscillation can build up in time and create an unphysical void below the vessel. We implemented a few ideas to attenuate the oscillations. At the heart of all the following techniques is the reduction of the time derivative of the water depth, especially for those cells transitioning to a pressurized state. All these modifications were effective at controlling the oscillations, each with a different intensity, and simulations with a horizontal motion are much more stable than without these techniques. With the collaboration of the BAW research institute, we worked on the model validation. We used data from two separate experiments to compare the measurements with the numerical results. Specifically, we focused on the ship-generated wave height and the hydrodynamic forces on the hull. The comparison is satisfactory for the wave height. The force and torque prediction is plausible but underestimated compared to the measurements. The model seems to displace the water volume correctly during the ship passage, while the force and torque response might need additional work to be trusted in applications. Even though the hydrostatic assumption is mostly correct in our range of applications, the presence and the motion of a ship could generate strong vertical accelerations of the flow, which may not be negligible. For this reason, we implemented an algorithm that corrects the velocity field, introducing also dispersive effects due to a non-hydrostatic pressure. The correction consists of a higher-order Bousinnesq-type term in the momentum equation and the solution of the resulting system. The non-hydrostatic update has a small influence on the wave generation, while it alters significantly the reaction forces. The subgrid method implementation allowed to benefit from high-resolution bottom descriptions while keeping the grid size coarse. The same subgrid can also be used for a refined definition of the hull, which makes the volume computations more accurate. Furthermore, the subgrid introduces new possible states for the cells, as they can be partially dry or partially pressurized. These intermediate states translate into smoother transitions from one state to the other when the free-surface is close to the bathymetry or to the hull. Concerning the software implementation of the developed scheme, in order to improve the execution performance of the prototype script formulated initially in Matlab, the numerical method was rewritten as a Fortran program. Also, thanks to the domain decomposition technique and the MPI standard, each simulation can run in parallel on multiple CPUs, leveraging the computational power of supercomputers. The coupling of the PDE and ODE system, together with an appropriate redefinition of the depth function, proved to be a valuable method for studying fluid-structure interaction problems. The combination of efficient numerical techniques led to the development of a tool with a potential to be applied in the practice for the simulation of floating objects in wide domains.
65

Backward error accurate methods for computing the matrix exponential and its action

Zivcovich, Franco 24 January 2020 (has links)
The theory of partial differential equations constitutes today one of the most important topics of scientific understanding. A standard approach for solving a time-dependent partial differential equation consists in discretizing the spatial variables by finite differences or finite elements. This results in a huge system of (stiff) ordinary differential equations that has to be integrated in time. Exponential integrators constitute an interesting class of numerical methods for the time integration of stiff systems of differential equations. Their efficient implementation heavily relies on the fast computation of the action of certain matrix functions; among those, the matrix exponential is the most prominent one. In this manuscript, we go through the steps that led to the development of backward error accurate routines for computing the action of the matrix exponential.
66

IL CAMBIAMENTO DEGLI ATTEGGIAMENTI DEGLI EUROPEI VERSO I RUOLI FEMMINILI NELLA SFERA PUBBLICA. ANALISI MULTILIVELLO E VALUTAZIONE CRITICA DEGLI STRUMENTI DI RILEVAZIONE / The change of the Europeans' attitudes toward female public roles. A multilevel analysis and a critical evaluation of the measurement instruments

LOMAZZI, VERA 20 February 2015 (has links)
La tesi propone una lettura multilivello e situata delle dinamiche di genere e ha l’obiettivo di studiare, attraverso un approccio comparativo, il cambiamento degli atteggiamenti degli europei nei confronti dei ruoli femminili nella sfera pubblica, intesi come indicatori dei valori di parità. Lo studio utilizza dati di indagini transnazionali come l’European Values Study e l’Eurobarometro. Gli strumenti di rilevazione degli atteggiamenti inclusi in tali indagini sono stati valutati criticamente, testandone l’adeguatezza per l’analisi comparativa. L’analisi multilivello, condotta in 22 paesi europei, evidenzia il diverso apporto esplicativo dei fattori individuali e contestuali. Il cambiamento degli atteggiamenti dal 1988 al 2008, in 7 contesti culturali (tra cui le “Tre Italie”), si è concentrato sull’analisi dei trend, osservando le differenze di genere e generazione, sui meccanismi del cambiamento e i suoi predittori. I risultati confermano la rilevanza del contesto nello sviluppo di valori di parità e, per promuovere una cultura paritaria, invitano a fare leva sull’istruzione e sulla partecipazione al mercato del lavoro delle donne. Per poter ottenere questo, le società necessitano di riorganizzarsi soprattutto in termini di servizi e benefit a favore delle famiglie, in modo che il modello di relazione tra i generi basato sulla reciprocità sia effettivamente possibile. / The thesis studies the gender dynamics as a multilevel and situated concept. It aims to investigate, by a comparative perspective, the change of attitudes toward female roles in the public sphere, here assumed as indicators of egalitarian values. The study uses data from cross-national surveys as the European Values Study and the Eurobarometer. The scales included in these surveys are critically evaluated in order to test their adequacy for comparative analysis. The multilevel analysis, performed in 22 European countries, shows the different contributes of individual and contextual factors. The attitudinal change from 1988 to 2008, in 7 cultural contexts (included the “Three Italies”) focused on the trend analysis, observing gender and generations differences, mechanism of change and its predictors. The results confirm that the context is relevant in the development of egalitarian values and, to promote an egalitarian culture, they invite societies to increase the educational level and the female economic participation. To get this, societies need to re-organize themselves in terms of services and benefits for families, in order to get the model of relationship based on the reciprocity between gender really possible.
67

ANALISI DEL CONTENUTO E PEOPLE CENTRED APPROACH NELLE POLITICHE SANITARIE: UNA PROPOSTA METODOLOGICA / Content Analysis and People Centred Health policies: proposal for a methodology

SAONARA, IRENE 16 April 2018 (has links)
La ricerca svolta si propone di esplorare la possibilità di utilizzare le metodologie quantitative di analisi del contenuto per determinare, tramite l’analisi dei testi già disponibili (dati testuali secondari, non raccolti ad hoc) le affinità tra una politica sanitaria regionale ed il Framework on integrated, people-centred health services (IPCHS, WHO, 2016).. La scelta di utilizzare come fonti di dati i testi è dovuta principalmente alle tempistiche di elaborazione del lavoro. Il Framework IPCHS è stato diffuso nella sua versione ufficiale nell’aprile 2016 e al momento della consegna di questo lavoro (settembre 2017) non è stata ancora adottata nessuna strategia ufficiale per il monitoraggio dell’implementazione delle politiche people centred. Anche il caso di studio scelto, ovvero la Riforma sociosanitaria lombarda, cominciata nel 2015, è ancora in fase di implementazione.La natura metodologico-sperimentale della tesi e la metodologia scelta hanno determinato l’adozione di un approccio basato sul paradigma dei Mixed methods. Il lavoro è strutturato nel seguente modo. Nel primo capitolo sono ripresi gli elementi metodologici essenziali della Analisi del contenuto applicata alla analisi delle politiche pubbliche. Vengono inoltre illustrati i risultati di un approfondimento condotto sul concetto di parola chiave. Nel secondo capitolo viene descritto il Framework IPCHS e viene illustrato il processo di composizione delle liste di parole chiave (dizionario PCA) nella loro duplice versione in inglese e in italiano attraverso una analisi tematica. Nel capitolo III è descritta una prima applicazione del dizionario PCA ad un corpus composto da 13 note relative ad interviste svolte durante il progetto Stop TB partnership. Il fine della analisi svolta nel terzo capitolo è testare la capacità di ricognizione delle liste rispetto ai contenuti attinenti al People Centred Approach. Per questa ragione i risultati ottenuti sono stati sottoposti a validazione qualitativa. Nel capitolo IV invece, il dizionario PCA (versione italiana) è stato utilizzato per analizzare un corpus relativo alla Riforma Sociosanitaria lombarda (l.r. 23/2015 ed alcune delibere attuative). Anche in questo caso i risultati ottenuti sono stati sottoposti a validazione, secondo un approccio mixed methods, anche per individuare l’impatto della traduzione in italiano sulla efficacia delle liste di parole chiave. / The aim of this research is to investigate the possibility to develop a secondary textual-data based protocol in order to use textual material such as interviews, national strategic plans and other official documents to classify a health policy as “integrated and people centred”. According to WHO resolution A69/39 “An integrated people-centred approach is crucial to the development of health systems that can respond to emerging and varied health challenges, including urbanization, the global tendency towards unhealthy lifestyles, ageing populations, the dual disease burden of communicable and non communicable diseases, multi-morbidities, rising health care costs, disease outbreaks and other health-care crises.” But how can we determine if a health policy is integrated and people centred? In this study, I try to develop a mixed methods based protocol to analyse textual material and evaluate his relevance with WHO Framework on integrated, people-centred health services. In the first chapter, there is a literature review about content analysis methodologies applied to policy analysis. Then I examine two different health policies, one implemented at international level by WHO (Stop TB Partnership Program) and one implemented at the regional level by Regione Lombardia (Health System Reform). While the first analysis aim is to text the dictionary created by a thematic analysis of the Framework on integrated people-centred health services (described in chapter 2), the second analysis is to apply the dictionary to an Italian case, characterized by textual materials written in Italian.
68

Analysis of 3D scanning data for optimal custom footwear manufacture

Ture Savadkoohi, Bita January 2011 (has links)
Very few standards exist for tting products to people. Footwear fit is a noteworthy example for consumer consideration when purchasing shoes. As a result, footwear manufacturing industry for achieving commercial success encountered the problem of developing right footwear which is fulfills consumer's requirement better than it's competeries. Mass customization starts with understanding individual customer's requirement and it finishes with fulllment process of satisfying the target customer with near mass production efficiency. Unlike any other consumer product, personalized footwear or the matching of footwear to feet is not easy if delivery of discomfort is predominantly caused by pressure induced by a shoe that has a design unsuitable for that particular shape of foot. Footwear fitter have been using manual measurement for a long time, but the combination of 3D scanning systems with mathematical technique makes possible the development of systems, which can help in the selection of good footwear for a given customer. This thesis, provides new approach for addressing the computerize footwear fit customization in industry problem. The design of new shoes starts with the design of the new shoe last. A shoe last is a wooden or metal model of human foot on which shoes are shaped. Despite the steady increase in accuracy, most available scanning techniques cause some deficiencies in the point cloud and a set of holes in the triangle meshes. Moreover, data resulting from 3D scanning are given in an arbitrary position and orientation in a 3D space. To apply sophisticated modeling operations on these data sets, substantial post-processing is usually required. We described a robust algorithm for filling holes in triangle mesh. First, the advance front mesh technique is used to generate a new triangular mesh to cover the hole. Next, the triangles in initial patch mesh is modified by estimating desirable normals instead of relocating them directly. Finally, the Poisson equation is applied to optimize the new mesh. After obtaining complete 3D model, the result data must be generated and aligned before taking this models for shape analysis such as measuring similarity between foot and shoe last data base for evaluating footwear it. Principle Component Analysis (PCA), aligns a model by considering its center of mass as the coordinate system origin, and its principle axes as the coordinate axes. The purpose of the PCA applied to a 3D model is to make the resulting shape independent to translation and rotation asmuch as possible. In analysis, we applied "weighted" PCA instead of applying the PCA in a classical way (sets of 3D point-clouds) for alignment of 3D models. This approach is based on establishing weights associated to center of gravity of triangles. When all of the models are aligned, an efficient algorithm to cut the model to several sections toward the heel and toe for extracting counters is used. Then the area of each contour is calculated and compared with equal sections in shoe last data base for finding best footwear fit within the shoe last data base.
69

CRESCITA UMANA E BENESSERE ORGANIZZATIVO NUOVE PROSPETTIVE DI PEDAGOGIA DEL LAVORO

ZINI, PAOLA 05 March 2012 (has links)
La ricerca si propone di delineare alcune proposte pedagogico-educative per il benessere organizzativo. Per raggiungere tale obiettivo è stato necessario rilevare i cambiamenti in atto nel mondo del lavoro, rintracciando le trasformazioni che accomunano tra loro i diversi paesi europei. Inoltre, al fine di ricuperare uno sguardo pedagogico sul lavoro, è stata effettuata una riflessione, movendo dai classici della pedagogia per mettere in luce alcune categorie che risultano essere ancora attuali per leggere il lavoro. La ricerca si avvale dei risultati emersi da tre analisi di caso svolte con imprese eccellenti ubicate nella provincia di Brescia e fortemente impegnate a sempre più migliorare la relazione con i loro stakeholder interni ed esterni. / The research’s aim is to give some educational proposals in order to improve the well being at work. In order to achieve this aim, it has been detected how the world of work is changing. However, to be able to look the work from a pedagogical point of view, I have made a reflection studying the education’s classical authors, in order to find some categories, that are useful to understand the work. For this research I have made 3 case studies in excellent companies in Brescia, engaged to improve the relations with their internal and external stakeholders.
70

Diseño en estructuras urbanas informales

Fernández Reyna, Miguel 09 May 2008 (has links)
El diseño en estructuras urbanas informales se plantea desde la dicotomía que presentan las ciudades del tercer mundo. La ciudad convencional que se enmarca dentro de los mecanismos normativos y legales, se ha visto superada por el crecimiento de una ciudad paralela que se desarrolla de manera espontánea al margen de los planes metropolitanos establecidos. La dicotomía se presenta con una realidad urbana preconcebida y otra improvisada. Una sujeta a grandes proyectos urbanos y a la industria de la construcción, y la otra atiende a las necesidades básicas respondiendo palmariamente al hecho constructivo. El diseño en estructuras urbanas informales aborda esa brecha que existe ente la ciudad formal y la ciudad informal.La total incorporación urbana pretendida en los procesos de Habilitación Física de Asentamientos Informales, comienza por asumir los requerimientos infraestructurales en términos numéricos y estadísticos, es decir; cantidad de unidades de viviendas de sustitución, longitud de acueductos, cloacas y alumbrado, área destinada a la nueva vialidad, número de centros comunitarios, asistenciales, deportivos, y demás especificaciones que componen el programa de un proyecto. Sin embargo, hay otra exigencia de igual importancia aunque menos mecánica o explícita, que demanda un tipo de cuidado sensible con el contexto y atento a la oportunidad. Una exigencia que consiste en aprovechar las potencialidades que ofrece la situación urbana tal y como se presenta en la realidad, y en buscar reconocer los valores propios de contexto informal, dejarles espacio y potenciarlos.La tesis toma como caso de estudio a los asentamientos informales en Caracas Venezuela que fueron objeto de diversos proyectos de Habilitación Física promovidos por diversos organismos internacionales y nacionales, bajo la metodología propuesta por el Banco Mundial. Tres figuras conceptuales recorren las diferentes escalas contempladas en los niveles de actuación de diseño urbano y arquitectónico.El concepto del límite atiende a la escala metropolitana y se asumen que el objeto principal de los proyectos de Habilitación Física de Asentamientos Informales persigue a la total incorporación infraestructural de un sector informal desprovisto de servicios básicos en el contexto urbano de la ciudad formal. Se sostiene que toda voluntad que pretenda una total incorporación urbana debe atender a los niveles de integración espacial determinados por los análisis sintácticos. Mientras los niveles de segregación espacial demuestren la desproporción revelada en los análisis espaciales, los niveles socio económicos supondrán una consecuente desproporción. La optimización de los proyectos infraestructurales comienza por elevar sustancialmente los niveles de integración espacial, y se sugiere que los límites físicos que dividen y excluyen a la ciudad informal de la ciudad formal contienen un importante potencial como factor de integración.A partir del análisis de un proyecto de Habilitación física se aborda la mediana escala del diseño urbano en el espacio público. Se sostiene que el proyecto integral en todos sus niveles de actuación puede responder al desafío de cualificar el diseño infraestructural en los procesos de Habilitación Física. Un desafío arquitectónico que plantea proporcionar nueva infraestructura y preservar las cualidades socio-físicas contenidas en la propia naturaleza orgánica del espacio informal. Se trata pues de construir un verdadero espacio urbano informal dotado de infraestructura y cargado de su propia porosidad genética que entremezcla formas y funciones en un espacio público.Por último el concepto de cromatismo atiende al diseño arquitectónico requerido en el ámbito de la pequeña escala del objeto arquitectónico. Una conclusión general del cromatismo contenido en esta pequeña escala no puede considerarse sino a partir del diseño como proceso. En primer lugar hay que recordar la importante participación comunitaria requerida en estos procesos. Y en segundo lugar se debe resaltar la importancia de lo que significa hacer visible el proceso de diseño y el proceso constructivo en el objeto edificado. La arquitectura que utilice los propios recursos informales se tiene que dedicar a conservar y a plasmar e proceso de diseño arquitectónico en un resultado final que en definitiva será solo un fragmento de otro proceso más grande.Este tesis ha perseguido la esencia de un fenómeno informa muchas veces despreciado como poco culto o poco interesante para la arquitectura, y ha determinado valores inherentes que pueden servir como herramientas para cualificar los proyectos de intervención física sobre el contexto urbano informal.

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