Tesi sul tema "Studio Velocity"
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1
Ming, Jin Martin. "High velocity impact studies on hybrid composite structures". Thesis, University of Portsmouth, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500334.
Testo completoAbstract (sommario):
Composite structural elements are now used in a variety of components for automotive, aerospace, marine, and architectural structures. The impact resistance of the materials is an important area of research. Fibre reinforced polymer (FRP) structures typically respond poorly to transverse impact events. In addition, uncertainties about the mechanics of damage make it difficult to ascertain the effect of an impact event on the performance of a FRP structure. Compounding these considerations is the fact that, in some cases, the damage will not be visible which could lead to components with considerable damage being allowed to continue in service: a hidden menace. In these series of studies, tests were conducted with an instrumented drop weight impact, an air gun system was developed and a numerical transient analysis conducted on composite plate to understand the loading distribution as a result of impact.
2
David-West, Opukuro Sunday. "Low velocity impact studies on CFRP composite structures". Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428854.
Testo completo
3
James, Philip Andrew. "Observation studies of the galaxy peculiar velocity field". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47488.
Testo completo
4
Cantoni, Francesco. "Studio e ottimizzazione di un generatore eolico a velocità autolimitante". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7932/.
Testo completoAbstract (sommario):
Studio e ottimizzazione di un rotore monopala a resistenza aerodinamica che, tramite deformazioni strutturali causate dal carico del vento, limiti autonomamente la propria velocità in caso di vento troppo forte.
5
Martin, J. S. "Radial velocity studies of the secondary in cataclysmic variables". Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306034.
Testo completo
6
Dakos, Thomas. "Fundamental heat transfer studies in grid generated homogeneous turbulence". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47835.
Testo completo
7
Mantega, Claudio <1976>. "Metodi numerici per lo studio di centri di lavoro ad alta velocità". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/957/1/Tesi_Mantega_Claudio.pdf.
Testo completoAbstract (sommario):
A Machining Centre is nowadays a complex mechanical, electronic, electrical system
that needs integrated design capabilities which very often require a high time-consuming effort.
Numerical techniques for designing and dimensioning the machine structure and components
usually requires different knowledge according to the system that have to be designed. This Ph. D
Thesis is related about the efforts of the Authors to develop a system that allows to perform the
complete project of a new machine optimized in its dynamic behaviour. An integration of the
different systems developed, each of which respond to specific necessities of designer, is here
presented. In particular a dynamic analysis system, based on a lumped mass approach, that rapidly
allows to setup the drives of the machine and an Integrated Dynamic Simulation System, based on a
FEM approach, that permit a dynamic optimization, are shown. A multilevel Data Base, and an
operator interface module provide to complete the designing platform. The proposed approach
represents a significant step toward the virtual machining for the prediction of the quality of the
worked surface.
8
Mantega, Claudio <1976>. "Metodi numerici per lo studio di centri di lavoro ad alta velocità". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/957/.
Testo completoAbstract (sommario):
A Machining Centre is nowadays a complex mechanical, electronic, electrical system
that needs integrated design capabilities which very often require a high time-consuming effort.
Numerical techniques for designing and dimensioning the machine structure and components
usually requires different knowledge according to the system that have to be designed. This Ph. D
Thesis is related about the efforts of the Authors to develop a system that allows to perform the
complete project of a new machine optimized in its dynamic behaviour. An integration of the
different systems developed, each of which respond to specific necessities of designer, is here
presented. In particular a dynamic analysis system, based on a lumped mass approach, that rapidly
allows to setup the drives of the machine and an Integrated Dynamic Simulation System, based on a
FEM approach, that permit a dynamic optimization, are shown. A multilevel Data Base, and an
operator interface module provide to complete the designing platform. The proposed approach
represents a significant step toward the virtual machining for the prediction of the quality of the
worked surface.
9
Shaw, Carl Robert. "Optical and radio H I studies of the fine-scale structure of the interstellar gas". Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388191.
Testo completo
10
Anderson, Kimberly Rose. "Quantifying Uncertainty in Low Velocity Human Aspiration Studies: Effect of Secondary Aspiration and Thin-walled Reference Sampling in Low Velocity Conditions". Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4812.
Testo completoAbstract (sommario):
In order to evaluate a biologically relevant measure of exposure, inhalable samplers are designed to match the aspiration efficiency of the human head. Human inhalability is evaluated in wind tunnel studies using mannequins as human surrogates or using numerical and computational methods. There has been differences between human aspiration efficiency estimates using wind tunnel studies and computational fluid dynamics (CFD) modeling, particularly for larger particle sizes (>68 µm). The objective of this dissertation was to evaluate biases in low velocity inhalability studies in an effort to explain the discrepancies in results between experimental and computational inhalability studies. This research addressed the phenomena of secondary aspiration on human facial skin, evaluated the appropriateness of mannequin surfaces as surrogates for humans, and evaluated the performance of the thin-walled reference sampler in low velocities to quantify potential biases in low velocity inhalability studies.
The first study determined a realistic coefficient of restitution (CoR) for human facial skin over a range of ages under nine environmental conditions. This study found human facial skin is non-uniform across the face and identified significant interaction between age and sampling location, indicating that how CoR varies with age is dependent on the location sampled.
The second study applied the average CoR values for forehead, cheeks and nose in CFD simulations to evaluate the effect of secondary aspiration on human aspiration efficiency estimates and determine how refined the CoR value needed to be to accurately model human aspiration efficiency. This study identified significant increases in aspiration when allowing for particle bounce, but no significant differences between uniform CoRs of 0.5, 0.8 and 1.0, indicating differences between different mannequin surfaces and particle interactions would have minimal effect on aspiration efficiency estimates.
The third study evaluated the performance of a horizontally-aligned reference sampler in low wind speeds (0.1 to 0.4 m s-1). While significant differences from unity were identified, differences ranged from -1 to 6% and would have a negligible effect on sampler efficiency estimates. The use of a horizontally-aligned isokinetic reference sampler was found to be appropriate in freestream velocities ranging from 0.1 to 0.4 m s-1.
11
Pourbagheri, Mahabadi Haniyeh. "Optical studies of surface recombination velocity in 4H-SiC epitaxial layer". Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37225.
Testo completoAbstract (sommario):
In this work optical studies of the effect of surface passivation for surface recombination velocity at the interface between 4H-SiC epitaxial layer and various passivation layers are presented. Four samples have been used consisting of three main parts: thin film oxide layer, 4H-SiC epitaxial layer and 4H-SiC substrate. The substrates for all samples are the same, highly doped n-type. The doping and thickness of the epitaxial layers are different; three samples have n-type epilayer, doping around 3-5×1015cm-3and one sample, the thinnest one, has a p-type doping of 1×1017cm-3.Two types of oxide are used as passivation layer: Al2O3on the n-type and p-type with 80 nm thickness, which is prepared by the ALD method, and SiO2– grown layer with 50 nm thickness, which is produced by thermal growth technique at 1250 ºC in N2O ambient for 8 hours. The forth epilayer was bombarded with 30 keV energy argon ion implanted with different doses through a native oxide. Free carrier absorption (FCA) technique was used to extract effective lifetime of excess carriers. The excess carriers are created by a high energy laser (355 nm) pulse, exiting electrons to the conduction band. The decay of these carriers is then studied by a second laser at 861nm. The carriers in the substrate recombine quickly, but in the thin epilayer the lifetime is long enough to be influenced by surface recombination at the epi-passivation layer interface. By fitting the experimental results, the surface recombination velocity (SRV) at the interfaces of epi/oxide can be extracted. The SRV of substrate/epi is assumed constant at 1×106cm/s value. The highest SRV, 5.7×104cm/s, is found in the n-type epitaxial layer with 50 nm SiO2and the slowest value, 1.07 ×103cm/s, is found in the p-type epitaxial layer with 80 nm Al2O3. For the argon implanted sample, we did not find the anticipation results. Although the highest dose gives the most defects, the SRV, 1.41×103 cm/s, was not very different for other doses.
12
Pandit, Shubhrangshu. "Velocity map imaging studies of competing dynamics in the gas phase". Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715743.
Testo completo
13
Sage, Alan Graham. "Velocity mapped ion imaging studies of substituted aromatic and heteroaromatic molecules". Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529835.
Testo completo
14
Zaouris, Dimitrious K. "Velocity map imaging and other spectrometric studies of molecules and clusters". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627942.
Testo completoAbstract (sommario):
The growing interest in the study of gas phase photodissociation dynamics has led to the development of experimental techniques to aid in the understanding of these processes in small (diatomic or triatomic molecules) and in larger systems. In addition, deposition of molecules on large clusters provides information of the clustering dynamics, which can shed light on the processes taking place in the condensed phase. The experiments described in this thesis use nanosecond and femtosecond velocity map imaging to explore the photo dissociation dynamics of a variety of systems on different timescales, and mass spectrometry to investigate the pick-up dynamics of several molecules on clusters. The experiments described in Chapter 3 concern iodine atom loss following the UV dissociation of iodocyclohexane. The bimodal kinetic energy distributions observed are attributed to the dissociation of axial and equatorial conformers of this molecule. The experimental results were complemented by ab initio calculations and two impulsive models. The results were also compared to the dissociation of CH3I, which is generally considered a benchmark system in the field of photodissociation dynamics. In Chapter 4 a time-resolved investigation of the photophysics of electronically excited chlorophenols is presented. The results emphasise the effect of intramolecular hydrogen bonding. To validate these results, the excited state decay of phenol has also been studied and used as a benchmark, since its dynamics have been studied in more detail. Furthermore, there is an introduction to on going high accuracy ab initio calculations, which aim to investigate the various conical intersections by which the electronically excited molecules can transfer to lower electronic states. Chapter 5 presents the experimentally determined pick-up cross-sections of several molecules (NO, HC1, etc) on ice nanoparticles. Particular emphasis is devoted to the pick-up of water molecules by large water clusters. For this process MD simulations have also been carried out. The experimental and theoretical results have been compared to the geometrical cross-sections, which are widely used in atmospheric models. The differences are discussed and the conclusions suggest that the (larger) experimentally determined cross-sections should be used in atmospheric models. Finally, Chapter 6 is dedicated to the recent upgrades of the Bristol VMI spectrometer. The spectrometer was fitted with new ion optics, for which the design details, the simulations and the results from experimental testing are presented. In general the new ion optics design performs better than the one used till now, giving better velocity resolution. However, the final resolution achieved thus far is limited 'by factors other than the configuration of the assembly. These factors are investigated and an effort is made to quantify their effect on the achievable resolution.
15
Nasr, Ahmed. "Computational and experimental studies of flow through a plate valve". Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243954.
Testo completo
16
Ungureanu, Stanislav. "Studio del campo di velocità per fluidi in moto laminare all'interno di condotti". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Cerca il testo completoAbstract (sommario):
Lo scopo di questa tesi è quello di ottenere una rappresentazione grafica del profilo di velocità di un fluido all’interno di un condotto. In particolare si studieranno le equazioni di bilancio facendo alcune ipotesi semplificative riguardo il moto del fluido. Si considererà un moto laminare in condizione di completo sviluppo dinamico e convezione forzata. Grazie a queste ipotesi si riuscirà ad ottenere un’equazione semplificata di Navier-Stokes, che permetterà di calcolare l’andamento della velocità all’interno di condotti con qualsiasi forma della sezione. In questo caso si confronterà il profilo di velocità di un condotto a sezione circolare con uno a sezione circolare forata come in uno scambiatore di calore a tubi concentrici.
Per risolvere l’equazione di Navier-Stokes e stampare l’andamento delle velocità all’interno della sezione del condotto si è utilizzato il software “Mathematica”, che è stato appreso durante l’attività di tirocinio curriculare. Questo software offre un supporto notevole allo studio matematico di qualsiasi problema. Permette inoltre di avere un riscontro grafico dei risultati ottenuti, direttamente nell’interfaccia utilizzata per la stesura del codice. Per rappresentare il profilo di velocità sarà inoltre utilizzato il metodo degli elementi finiti all’interno di Mathematica, che permetterà di ottenere una soluzione più uniforme e vicina alla realtà.
Il metodo degli elementi finiti (FEM) permette di semplificare lo studio del moto di un fluido, in quanto ci dà la possibilità di avere un sistema di equazioni algebriche che ne descrivono il moto, invece di equazioni differenziali e le sue relative condizioni al contorno.
Sarà quindi brevemente descritto questo metodo che è stato di grande aiuto tramite l’implementazione della “mesh” su Mathematica.
17
Cecchini, Giuseppe. "Studio preliminare di flusso attorno ad un pantografo per treno ad alta velocità". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7069/.
Testo completoAbstract (sommario):
In questo elaborato di tesi viene presentata la comparazione tra due codici CFD, rispettivamente Fluent e OpenFOAM, mediante simulazioni che sono alla base di uno studio numerico di flusso attorno ad un pantografo per treno ad alta velocità. Si è apprezzato quindi la facilità d’uso di un software venduto tramite licenza e la difficoltà di un software open source come OpenFOAM, il quale però ha vantaggi in termini di adattamento ai casi più specifici. Sono stati quindi studiati due casi, scambio termico in regime laminare attorno ad un cilindro bidimensionale e flusso turbolento completamente sviluppato in un canale. Tutte le simulazioni numeriche hanno raggiunto convergenza e sono state validate positivamente mediante confronto con dati sperimentali. Il primo caso prevede un cilindro investito da un flusso a temperatura minore rispetto alla temperatura della superficie del cilindro; per avere più riscontri, sono state condotte diverse prove a valori differenti del numero di Prandtl, e per ogni simulazione è stato ricavato il corrispettivo numero di Nusselt, successivamente comparato con i dati sperimentali per la validazione delle prove. A partire dalla creazione della griglia di calcolo, è stato effettuato uno studio del fenomeno in questione, creando così una griglia di calcolo sviluppata a valle del cilindro avente maggior densità di celle a ridosso della parte del cilindro. In aggiunta, svolgendo le prove con schemi numerici sia del primo che del secondo ordine, si è constatata la miglior sensibilità degli schemi numerici del secondo ordine rispetto a quelli del primo ordine. La seconda tipologia di simulazioni consiste in un flusso turbolento completamente sviluppato all’interno di un canale; sono state svolte simulazioni senza e con l’uso delle wall functions, e quindi usate griglie di calcolo differenti per i due tipi di simulazioni, già disponibili per entrambi i software. I dati ottenuti mostrano uno sforzo computazionale maggiore per le simulazioni che non prevedono l’uso delle wall functions, e quindi una maggiore praticità per le simulazioni con le wall functions. Inoltre, le simulazioni di questo secondo caso sono state svolte con diversi modelli di turbolenza; in Fluent sono stati utilizzati i modelli k-ε e RSM mentre in OpenFOAM è stato utilizzato solo il modello k-ε in quanto il modello RSM non è presente. La validazione dei risultati è affidata alla comparazione con i dati sperimentali ricavati da Moser et all mediante simulazioni DNS, mettendo in risalto la minor accuratezza delle equazioni RANS.
18
Price, Roosevelt Jerome. "Photodissociation studies with vacuum ultraviolet lasers by means of ion velocity imaging /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
Testo completo
19
Fenati, Francesco. "Studio e controllo della velocità di fasciatura di balle cilindriche in avvolgitori per agricoltura". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/9892/.
Testo completoAbstract (sommario):
Studio e analisi della velocità di fasciatura di balle cilindriche con il film plastico negli avvolgitori utilizzati in agricoltura. In particolare è stato studiato un meccanismo che potesse garantire il corretto funzionamento ad elevate velocità di avvolgitura evitando che il film plastico subisca eccessivi tensionamenti o che giunga a rottura. Il lavoro ha previsto numerosi test e rilevamenti di velocità che hanno prodotto risultati positivi e utili ai fini di uno studio futuro più dettagliato.
20
Cihan, Abdullah. "The Rise Velocity Of An Air Bubble In Coarse Porous Media: Theoretical Studies". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604709/index.pdf.
Testo completoAbstract (sommario):
The rise velocity of injected air phase from the injection point toward the
vadose zone is a critical factor in in-situ air sparging operations. It has been
reported in the literature that air injected into saturated gravel rises as discrete air
bubbles in bubbly flow of air phase. The objective of this study is to develop a
quantitative technique to estimate the rise velocity of an air bubble in coarse
porous media. The model is based on the macroscopic balance equation for forces
acting on a bubble rising in a porous medium. The governing equation
incorporates inertial force, added mass force, buoyant force, surface tension and
drag force that results from the momentum transfer between the phases. The
momentum transfer terms take into account the viscous as well as the kinetic
energy losses at high velocities. Analytical solutions are obtained for steady,
quasi-steady, and accelerated bubble rise velocities. Results show that air bubbles
moving up through a porous medium equilibrate after a short travel time and very
iv
short distances of rise. It is determined that the terminal rise velocity of a single
air bubble in an otherwise water saturated porous medium cannot exceed 18.5
cm/sec. The theoretical model results compared favorably with the experimental
data reported in the literature. A dimensional analysis conducted to study the
effect of individual forces indicates that the buoyant force is largely balanced by
the drag force for bubbles with an equivalent radius of 0.2-0.5 cm. With
increasing bubble radius, the dimensionless number representing the effect of the
surface tension force decreases rapidly. Since the total inertial force is quite small,
the accelerated bubble rise velocity can be approximated by the terminal velocity.
21
Moscioni, Arianna. "Studio della composizione chimica di un campione di stelle retrograde nei dintorni solari". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25348/.
Testo completoAbstract (sommario):
In base allo scenario di merging gerarchico delle galassie, l'alone stellare della nostra Galassia si è formato da eventi di merging con galassie più piccole. Queste strutture, oggi dissolte, sono individuabili come raggruppamenti nello spazio definito dagli Integrali del Moto. L'alone stellare della Via Lattea è caratterizzato da una componente stellare prevalentemente retrograda. Da ciò è subito emerso uno scenario ampiamente accettato che prevede che la maggior parte dell'alone retrogrado è ciò che resta di un antico merger con la Via Lattea di una galassia nana chiamata Gaia-Enceladus. Successivamente sono state individuate altre sottostrutture meno prominenti, come Sequoia e Thamnos. La rilevazione delle stelle associate a queste sottostrutture è però legata alla disponibilità delle velocità radiali, che completano lo spazio delle fasi. In questo lavoro di tesi si presenta l'analisi di 26 spettri ottenuti con PEPSI di stelle retrograde nei dintorni solari selezionate sulla base del valore della loro velocità trasversale. La misura delle velocità radiali degli spettri ha permesso di attribuire ogni target ad un possibile progenitore. L'analisi chimica ha mostrato come si tratti di stelle con metallicità tra -1 e -3 dex. Una delle stelle di dubbia attribuzione è risultata la più metal-poor del campione, il che la rende più compatibile con Sequoia, in quanto questa sottostruttura è caratterizzata da valori di metallicità inferiori rispetto a quelli di Gaia-Enceladus. Sono stati evidenziati due targets con valori di [Na/Fe] discrepanti dal resto del campione. Infatti, due stelle risultano Na-rich, mostrando una similarità con le abbondanze tipiche prodotte negli ambienti degli ammassi globulari; una stella risulta Na-poor, che potrebbe ricalcare la bassa abbondanza di Na delle galassie nane. Alcune stelle di Sequoia e Thamnos mostrano abbondanze chimiche anomale per quanto riguarda alcuni elementi che sono rivelatrici di una differente evoluzione chimica.
22
Maljugin, Anton. "Emergence of dynamic capabilities in low velocity industries : a case study of European shipbuilding industry". Thesis, Kingston University, 2013. http://eprints.kingston.ac.uk/27010/.
Testo completoAbstract (sommario):
During last two decades the uncertainty in and complexity of the external environment has become a common challenge for most companies worldwide. To gain a more sustainable competitive advantage in their rapidly changing competitive milieux companies should be able successfully to integrate innovative elements and develop their dynamic capabilities. The value of dynamic capabilities lies in the resource configurations that they create or enhance in rapidly and radically changing environments, which in turn enable the firm to pursue opportunities in new, unpredictable markets (Ambrosini & Bowman, 2009). Firms which operate in high-velocity industries continuously develop their dynamic capabilities as the only means to survive. Companies in low-velocity industries are usually unprepared for radical and rapid changes and thus they are less competitive than companies which develop their dynamic capabilities in less stable environments. This study examines how dynamic capabilities have evolved in an industry which is moving from a relatively low velocity into moderately high velocity. A deductive, interpretive approach is chosen for the current study, mainly because it offers a better opportunity to explain, describe, illustrate, and explore specific aspects of the emergence of dynamic capabilities in relatively low velocity environments. The study has studied three ship building companies in Europe. The study has two main phases of data collection. The first data collection phase begins with three in-depth interviews with chief executives from the companies selected for the case study. The chief executives of these companies are chosen for their known, recent experience with dynamic capabilities and because they represent the shipbuilding industry in Europe. The second data collection phase consists of nineteen semistructured interviews. The collected research data is analyzed by case studies methods. This work has found that dynamic capabilities developed in stable environments lead to superior performance under conditions of environmental volatility; entrepreneurial behaviour on every managerial level is necessary in order to develop dynamic capacity; low-cost experimentations are one of the most effective methods to trigger dynamic capabilities; and learning through internationalization is an effective tool to develop dynamic capabilities. It has also found that new business development units and spin-offs might trigger development of dynamic capabilities but cooperation between small and medium-sized firms and large enterprises does not increase the development of dynamic capabilities and might be even counterproductive.
23
Domeniconi, Stefano. "Studio e ottimizzazione di una trasmissione a infiniti rapporti per un motore automobilistico". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7871/.
Testo completo
24
SAVIOLI, GABRIELE. "Studio della meccanica ventricolare sinistra nella diagnosi differenziale della cardiopatia ipertrofiche mediante lo studio della deformazio e e della velocità di deformazione parietale". Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1203332.
Testo completo
25
Rice, Reginald H. "Atomic force microscopy studies of thermal, mechanical and velocity dependent wear of thin polymer films". Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14955.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Physics
Robert Szoszkiewicz
Nanoscale modifications of polymer surfaces by scratching them with sharp tips with curvature radii of tens of nanometers and at variable temperatures are expected to provide wealth of information characterizing wear response of these polymers. Such studies are important in the light of understanding the nanoscale behavior of matter for future applications in advanced polymer coatings. This thesis describes how Atomic Force Microscopy (AFM) and hot-tip AFM (HT-AFM) methods were used to characterize thermal and mechanical properties of a 30 nm thick film of poly(styrene-block-ethylene oxide), PS-b-PEO, and modify its lamellar surface patterns. Additionally, it is revealed how contact AFM and HT-AFM methods can efficiently characterize the wear response of two popular polymer surfaces, poly(methyl methacrylate), PMMA, and polystyrene, PS. The AFM and HT-AFM studies on PS-b-PEO copolymer were aimed at producing spatial alignment of respective PS and PEO parts. Instead, however, surface ripples were obtained. These measurements are explained using mode I crack propagation model and stick-and-slip behavior of an AFM tip. In addition, HT-AFM studies allowed extraction of several thermo-physical properties of a PS-b-PEO film at local volumes containing about 30 attograms of a polymer. These thermo-physical quantities are: PEO melting enthalpy of, 111 ± 88 J g[superscript]-1, PS-b-PEO local specific heat of 3.6 ± 2.7 J g[superscript]-1K[superscript]-1, and molecular free energy of Helmholtz of 10[superscript]-20 J nm[superscript]-2 for the PEO within PS-b-PEO. Utilizing a spiral scan pattern at constant angular speed and at various temperatures at the AFM tip-polymer interfaces, the wear response of PS and PMMA polymers was characterized. Cross-sections along the obtained spiral wear patterns provided plots of polymer corrugation as a function of scanning speed. From these studies it was found that the corrugation of the modified polymer surface decays exponentially with linear velocity of the scanning tip.
26
Badioli, Lucrezia. "Studio sperimentale della compressibilità delle argille sensitive finlandesi". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
Lo studio proposto in questa tesi si prefigge di raccogliere ed interpretare un esteso ed affidabile database di prove di laboratorio su argille sensitive o “quick clays”, al fine di determinarne le proprietà di compressibilità. La letteratura scientifica riguardante il comportamento meccanico di questi materiali non è molto estesa. Ciò è dovuto essenzialmente alle difficoltà che si riscontrano durante le fasi di prelievo di campioni indisturbati, dal momento che i terreni in oggetto sono molto sensibili al rilascio tensionale e al rimaneggiamento. Negli ultimi anni, diversi gruppi di ricerca hanno cercato di colmare le lacune di conoscenze attualmente esistenti sulla complessa risposta meccanica di questi terreni. In particolare, il gruppo geotecnico della Tampere University (Finlandia) ha condotto numerose ricerche in diversi siti di prova, analizzando la risposta delle argille ivi rinvenute sia in termini di caratteristiche di resistenza, sia di compressibilità. La ricerca presentata in questa tesi si è avvalsa della collaborazione dei ricercatori dell’Università di Tampere, ed è stata in particolare coordinata dal Prof. Länsivaara. In particolare, l’obiettivo della ricerca proposta è stato quello di analizzare la risposta dei terreni in prove di compressione ad espansione lateriale impedita, in funzione della velocità di deformazione applicata. I test di riferimento per la ricerca oggetto di tesi sono stati il CRS test (constant strain rate test), che prevede l'applicazione di una velocità di deformazione costante, e il VRS test (variable strain rate test), che viene eseguito modificando nel corso della prova la velocità di deformazione del provino. I dati sperimentali sono stati analizzati alla luce di un approccio innovativo per la determinazione della pressione di preconsolidazione, del modulo confinato e delle caratteristiche di creep dei terreni studiati.
27
Edris, Hossein. "Studies on high velocity oxy-fuel sprayed coatings of iconel 625 and Ni-Crâ†3Câ†2". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362891.
Testo completo
28
BUIAT, Martina. "COMPARISON CALIBRATION OF LOW-COST PROTOTYPES OF ACOUSTIC PRESSURE-VELOCITY PROBES AND SOME APPLICATION CASE-STUDIES". Doctoral thesis, Università degli studi di Ferrara, 2015. http://hdl.handle.net/11392/2389092.
Testo completoAbstract (sommario):
The main topic of this work is the acoustical characterisation and the comparison calibration
of a new low cost prototype of a pressure-velocity probe based on MEMS and CMOS
technologies. The development during the last years of micro sensors using the double
hot-wire anemometric transduction principle, has permitted to directly measure the velocity
of the air particle, thus giving a fundamental contribution to the intensimetric measurements.
This in turn required a more deep study of the calibration techniques as at least two acoustical
signals (pressure and axial velocity) have to be processed simultaneously in order to obtain
precise and affordable measurements of energetic properties of sound. In particular this
work is devoted to the analysis and experimental validation of the "comparison calibration"
methodology when applied to pressure-velocity probes still in their early stage of prototypes.
After an introduction on the Acoustical Energetics, in which the main quantities are
described and simulated for a monochromatic field, the next chapters are dedicated to the
probe realised within the SIHT (Sogliano Industrial High Technology) project, which is
based on the collaboration between the Institute of Acoustics and Sensors Corbino-CNR,
of the CNR-IEIIT and of the Deltatech industry in Sogliano al Rubicone (FC, Italy). We
describe the different prototypes that have been realised and their relative characterization,
that have been useful to design new and improved prototypes. The particular geometry of the
prototypes has also required a new procedure of comparison calibration, in which the probe
under test is calibrated using a reference one, in a generic field.
The possible applications of the new probe are various, and go from audiometric field to
condition monitoring, and are investigated in the last chapter.
29
Österberg, Klas. "Vascular wall responses to bypass grafting : studies in mice /". Göteborg : Dept. of Molecular and Clinical Medicine, Vascular Surgery, Institute of Medicine, Sahlgrenska Academy at Göteborg University, 2008. http://hdl.handle.net/2077/9437.
Testo completo
30
De, Lucia Chiara. "Studio di un rivelatore per neutroni di alta energia". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9530/.
Testo completoAbstract (sommario):
Guidata dall'interesse per lo studio della fissione nucleare, per molto tempo la ricerca nel campo dei neutroni si è concentrata su energie medio-basse (E<20 MeV) mentre per la regione a più alte energie le informazioni risultavano scarse o mancanti. Recentemente, invece, si è sviluppato un nuovo interesse per i Neutroni di Alta Energia, utilizzabili nelle terapie mediche per la cura di tumori, e di grande importanza per la radioprotezione e la trasmutazione delle scorie radioattive derivanti da produzione di energia nucleare. Queste applicazioni richiedono precisi fasci di neutroni quasi-monoenergetici, con energie dai 20 a qualche centinaia di MeV, servono perciò misurazioni intese a determinare le caratteristiche del fascio e atte a ottenere valori precisi della sezione d'urto relativa ai processi innescati da neutroni veloci.
La sezione d'urto di un certo processo nucleare si deduce dalla misura del numero di eventi acquisiti per unità di tempo da un rivelatore, conoscendo l'efficienza di questo, l'intensità del fascio che incide nel bersaglio e le caratteristiche del target. Diventa, quindi, determinante la conoscenza dell'intensità del fascio dei neutroni, anche nel caso di un intervallo energetico ampio, come quello prodotto al CERN dalla facility n_TOF, che possiede energie che vanno dal meV al GeV.
Sulla base di queste motivazioni, in questo lavoro di tesi, si vuole proporre un prototipo semplice di rivelatore per Neutroni di Alta Energia e si presenta uno studio preliminare del primo test sotto fascio, focalizzando l'attenzione sulla massima energia misurabile.
31
Iskra, Andreas. "Photofragmentation studies of metal ion-molecule complexes and metal oxides". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:d3663b37-7954-47a3-83e3-4a9ad7b9e3e7.
Testo completoAbstract (sommario):
Gas phase metal-containing complexes provide suitable systems in which to study fundamental binding motifs between a metal ion and molecules in the absence of any solvent, support or competing charge effects. In this thesis, metal-containing species are explored experimentally using infrared resonance enhanced photodissociation (IR-REPD) spectroscopy and velocity map imaging (VMI). The experimental results are further interpreted with the aid of spectral simulations based on density functional theory (DFT). These are the first studies reported using a newly built IR-REPD spectrometer equipped with a purpose-built laser ablation source to allow for the study of single metal ion-molecule complexes. The laser ablation source is shown to efficiently produce various complexes including Rh+(CO2)n, VO2+(N2O)n and Au+(CH4)n and the IR-REPD spectrometer has been characterised against a well-studied system of V+(CO2)n complexes. In order to record the IR-REPD spectra for small metal ion-molecule complexes, an argon atom is employed as the inert messenger. A combined IR-REPD spectroscopy and DFT investigation of M+(CO2)n complexes (where M = Co+, Rh+ and Ir+) reveals a common [M+(CO2)2] core structure for all three considered metal ions. Additional ligands, which are not directly bound to the central metal ion, experience lower perturbation as evident in the reduced blue-shift for the ligand in the outer coordination shells. A further IR-REPD/DFT study involving CO2 complexation around NbO2+ and TaO2+ ions reveals a strongly-bound core of four CO2 ligands around the MO2+ ion (M = Nb, Ta). A significant increase in the intermolecular bond distances for the second coordination sphere ligands coincides with a decrease in the calculated binding energies. Velocity map imaging is employed to explore the rich photodissociation dynamics of VO in the vicinity of C4Σ- - X4Σ-(v',0) vibronic transitions in VO. The final quantum state distribution was observed to be strongly dependent on the intermediate vibronic state of VO via which the dissociation threshold is reached. This work provides a refined value for the VO dissociation energy of D0(VO) = 53190 ± 261 cm-1 in excellent agreement with available literature.
32
Angelini, Virginia. "Studio e modellizzazione delle accelerazioni non gravitazionali di Cassini causate dai getti dei geyser di Encelado". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14262/.
Testo completoAbstract (sommario):
Encelado, satellite naturale di Saturno, presenta una intensa attività criovulcanica nella regione del polo sud: vengono eruttati da alcune fratture chiamate “tiger stripes” getti di vapore e grani di ghiaccio che raggiungono chilometri di altezza. Quando la sonda Cassini transita in questa zona durante un flyby, è sottoposta ad una resistenza aerodinamica che ne modifica la velocità.
Questo elaborato si occupa dello studio delle variazioni di velocità (delta-V) a cui è sottoposta la sonda Cassini durante i flyby E9 ed E19. Per prima cosa è stata calcolata la densità del materiale eruttato con due diversi modelli e questo valore è stato utilizzato per calcolare la resistenza aerodinamica. E’ stata poi valutata l’incertezza dei modelli mediante un'analisi di sensitività dei parametri empirici utilizzati, necessaria per eseguire quindi l’analisi Monte Carlo. In seguito sono stati calcolati i delta-V e le probabilità di compatibilità con valori di riferimento disponibili in letteratura ottenuti tramite fit orbitale dei dati doppler dal team di L.Iess (2014). I risultati mostrano per E9 una buona compatibilità per entrambi i modelli utilizzati, mentre per E19 una scarsa compatibilità del primo modello e una buona per il secondo.
33
Summers, Louisa. "The contribution of body segments to ball velocity in the overarm throw of skilled male and female athletes". Scholarly Commons, 1995. https://scholarlycommons.pacific.edu/uop_etds/2291.
Testo completoAbstract (sommario):
The purpose of this study was to determine the better predictors of ball velocity and identify differences in the overarm throw of male and female athletes. A three dimensional videographic analysis was performed to analyze the angular and linear velocities of various body segments, the time between maximum velocity of the body segment and ball release, stride length, height of release, and angle of trajectory. Eight male baseball players and six female softball players volunteered to be videotaped. A one way ANOV A with ball velocity as the dependent variable revealed a significant difference between genders (f (1, 11) = 5.3, ll < .0413). A forward stepwise multiple regression analysis allowed selection from all of the angular velocity variables and the kinematic variables regressed on the dependent variable of ball velocity. This identified the main contributors to ball velocity. For the male athletes three variables were selected into the multiple regression equation, (a) the angular velocity of the forearm at ball release, (b) the time between maximum angular velocity of the pelvis and ball release,and (c) the angular velocity of the pelvis at ball release. For the female athletes the multiple regression equation yielded one variable, the angular velocity of the forearm at ball release to predict ball velocity. Gender differences existed in the sequential timing of the pelvis, trunk, and upper extremity. The female athletes reached maximum pelvic velocity earlier with peak trunk velocity occurring later than the males. The sequential timing differences may have played a role in the explanation of why the female throwers lacked transfer of momentum from the lower extremity to the upper. The results of an unpaired two-tailed t-test on the two best throwers in each group revealed differences in ball velocity, maximum linear velocity of the hip, and maximum linear velocity of the trunk.
34
Giegerich, Jens [Verfasser], e Ingo [Gutachter] Fischer. "Velocity-Map-Imaging Studien an reaktiven Intermediaten: Fulvenallen, C3H2 Isomere und Alkylradikale / Jens Giegerich. Gutachter: Ingo Fischer". Würzburg : Universität Würzburg, 2015. http://d-nb.info/1108782043/34.
Testo completo
35
Pachner, Kai [Verfasser], e Ingo [Gutachter] Fischer. "Photodissoziationsreaktionen der Xylyl-Radikale, C8H9, und des Benzyl-Radikals, C7H7: Eine Velocity-Map-Imaging-Studie / Kai Pachner ; Gutachter: Ingo Fischer". Würzburg : Universität Würzburg, 2018. http://d-nb.info/1170583393/34.
Testo completo
36
Pearce, Dominic Robert. "The characterisation of rock masses from laboratory and field studies of the velocity and attenuation of seismic waves". Thesis, University of Leeds, 1996. http://etheses.whiterose.ac.uk/2431/.
Testo completoAbstract (sommario):
This thesis addresses the concept of non-destructive rock mass characterisation using in-situ measurements of the velocity and attenuation of seismic waves. The thesis is divided in to two sections, the first of which considers a comprehensive laboratory study of the phenomena of stress-induced velocity and attenuation anisotropy, whilst the second documents a number of field case studies. In the first section, a review is given of the current experimental evidence and theoretical explanations of the factors that affect the propagation of seismic waves. A description is given of the spectral ratio technique for the laboratory determination of P-wave attenuation in rock core samples. The section concludes with the presentation of the results of an investigation of stress-induced velocity and attenuation anisotropy in intact samples, samples induced to failure, and fractured samples. Experimental results show that in-situ measurements of the change in velocity and attenuation could be used to predict stress change in a homogenous rock mass which contains infrequent, isolated fractures. The prediction would be based on laboratory measurements of stress-induced attenuation anisotropy in intact samples. In the second section, a new variant of seismic tomography called Combined Transmission and Reflection Tomography (CTRT) is fully described. In the chapters following this, a number of field cases are documented to show how the technique can be used to identify geological structure such as general stratigraphy, faults, orebody volumes, and man-made features such as old workings and blast induced fracture zones. The technique is shown to be ideal for surveying inaccessible areas and improving tomograms above those that can be produced by the popular transmission tomography algorithms. A final case study considers the use of seismic measurements in the prediction of rock mass behaviour in the footwall of a mine stope. The simple technique described successfully identified fault zones in two stopes before mining commenced, one of which resulted in the subsequent loss of a stope half way through mineral extraction. In conclusion this thesis comprehensively describes how seismic measurements can be used to characterise a rock mass and lays the foundations for using the same measurements for monitoring and predicting rock mass behaviour in active environments.
37
Venturini, Giacomo. "Anemometria a filo caldo: studio di un sistema di calibrazione per sonde a due fili con applicazione al "long pipe" in CICLoPE". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9680/.
Testo completoAbstract (sommario):
L’anemometro a filo caldo (in inglese hot wire) é lo strumento maggiormente usato per studiare sperimentalmente la turbolenza. A seconda di quante componenti della velocitá interessa studiare, esistono anemometri a uno, due o tre fili. Questo elaborato di tesi si concentra su sonde a due fili.
Per prima cosa, ogni volta che si utilizza questo strumento bisogna effettuare una calibrazione, fase molto importante perché permette di relazionare le tensioni che ogni filo acquisisce con la velocitá reale del flusso.
Sono presentati tre differenti metodi utilizzati per sonde a due fili e, dopo averli analizzati, sono stati applicati a dati acquisiti prima al CAT (Coaxial Aerodinamic Tunnel), struttura presente a Forlí, nell’hangar dell’Universitá di Bologna e poi al CICLoPE (Center for International Cooperation in Long Pipe Experiments), Long-Pipe costruito a Predappio, utilizzato per lo studio della turbolenza.
La calibrazione per sonde a due fili si puó dividere in due parti, quella di velocitá e quella per gli angoli. Mentre al CAT é possibile effettuarle entrambi, al CICLoPE non é attualmente possibile eseguire la calibrazione angolare perché non esiste alcuno strumento utilizzabile per regolare la sonda all’angolo desiderato.
Lo scopo di questo elaborato di tesi è trovare un metodo di calibrazione per sonde a due fili applicabile al CICLoPE eseguendo sul posto solamente una calibrazione di velocitá e adattando quella angolare effettuata precedentemente al CAT. Questo puó provocare dei problemi perché la calibrazione risulta fortemente dipendente da condizioni interne dei fili, come la resistenza, ma anche da condizioni al contorno, come la temperatura e la pressione dell’ambiente esterno.
Dopo aver eseguito due campagne sperimentali di test, una al CAT e una al CICLoPE, i dati acquisiti sono stati elaborati per valutare l’efficacia dei vari metodi.
38
Barsotti, Giulia. "Studio della variazione di velocita delle onde di taglio in una colata di terra nella sua fase di post-attivazione". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18637/.
Testo completoAbstract (sommario):
In letteratura c'è intenso dibattito tra chi sostiene che la morfologia 'flow like' tipica delle colate di terra sia attribuibile a sviluppo di piani di taglio interni alla massa di frana e chi invece crede sia determinata da una vera e propria fluidificazione della massa (Bertello e al, 2018).
Oggetto di questo studio è un movimento composito scorrimento di terra-colata il cui terreno è stato caratterizzato mediante analisi granulometrica e limiti di Attemberg.
Questo lavoro di tesi mediante lo studio della variazione di velocità delle onde di taglio della colata di terra nella sua fase di post-attivazione si prefigge di capire se questa è soggetta o meno a un processo di consolidazione.
La velocità delle onde di taglio nei fluidi teoricamente è pari a zero (Reynolds, 1997), dunque con un processo di consolidazione si dovrebbe osservare un aumento della velocità di propagazione delle onde di taglio all'interno della frana. Questo è ciò che si osserva nel corpo di frana in esame dove, nell'arco di otto mesi, sono state eseguite indagini geofisiche di onde di superficie (MASW, ReMi, H/V).
Dalle misure è emerso che al di fuori alla frana le velocità rimangono costanti nel tempo mentre all'interno mostrano un notevole incremento.
A partire dai valori di velocità sono stati ricavati il modulo di taglio, l'indice dei vuoti e il contenuto gravimetrico di acqua del terreno.
Quest'ultimo valore è stato rapportato al limite liquido e plastico e confrontato con il contenuto volumetrico di acqua registrato da un sensore di umidità installato in sito.
Entrambi i valori di umidità sembrano indicare consolidazione del corpo di frana.
39
TOCCO, FILIPPO. "Aggiustamenti metabolici durante il recupero nell'Interval Training: studio in laboratorio e sul campo in atleti di mezzofondo e velocità prolungata". Doctoral thesis, Università degli Studi di Cagliari, 2011. http://hdl.handle.net/11584/266299.
Testo completoAbstract (sommario):
Lo scopo di questo studio è stato quello di quantificare l'affidabilità della frequenza cardiaca (HR), come parametro utile per valutare le condizioni di recupero di mezzofondisti e velocisti, durante un Interval Training (IT). Sono stati studiati ventidue atleti sottoposti a due diverse sessioni di
IT: al 80% e 120% della soglia anaerobica (SA). Durante entrambe le sessioni abbiamo misurato
HR, consumo di ossigeno (VO₂), produzione di anidride carbonica (VCO₂), ventilazione polmonare
(Ve), mediante un analizzatore portatile di gas. Inoltre, è stato calcolato l'eccesso di produzione di anidride carbonica (CO₂excess) per verificare l'ipotesi che la deriva cardiaca, che si è verificata durante il recupero tra le ripetizioni di IT, fosse collegata ad uno stato di acidosi lattica. La deriva cardiaca è avvenuta in entrambi i gruppi ad entrambe le intensità lavorative, mentre CO₂excess, VO₂ e Ve non si sono modificati. Sulla base della nostra ricerca, l'utilizzo della HR come parametro di valutazione del recupero metabolico appare impreciso e fuorviante ed in definitiva non idoneo per la gestione del recupero nell’allenamento.
----------------------------------------------------------------------------------------------------------------------------The aim of this study was to quantify the reliability of heart rate (HR) monitoring to assess
recovery status, after moderate and high-intensity exercise, in prolonged sprint and middle
distance running specialties of athletics. Twenty-two runners underwent two different sessions of
interval training: at 80% and 120% of anaerobic threshold (AT). Throughout both sessions we
measured HR, oxygen uptake (VO₂), carbon dioxide production (VCO₂), pulmonary ventilation
(Ve), by means a portable gas analyzer. The excess in carbon dioxide production (CO₂excess) was
also measured to test the hypothesis that a cardiac drift, that occurred during recovery between
repetitions of interval training, was related to lactic acidosis. The heart rate charts in both groups
of athletes and with respect to the two workloads showed a progressive increase of the same
during recovery periods, while CO2excess as well as VO₂ and Ve were not modified. On the basis
of our research, the use of HR as a parameter of evaluation of the established recovery is
inaccurate and unfit for training.
40
Longo, Alessandra. "Studio sperimentale e numerico del comportamento esplosivo di polveri metalliche". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
L’utilizzo sempre crescente di sistemi complessi contenenti particelle infiammabili di piccola dimensione, in svariati ambiti industriali ha incentivato e fortemente promosso lo sviluppo di modelli capaci di stimare i principali parametri di sicurezza e ottimizzare la progettazione degli impianti stessi. Ad oggi, tuttavia, l’approccio utilizzato al fine di effettuare tale caratterizzazione nel campo delle esplosioni da polveri è basato su procedure standard sviluppate a partire da valutazioni di natura empirica. Nella fattispecie, i test sono finalizzati alla valutazione della pressione massima di esplosione o dell’indice di deflagrazione (KST). Tali parametri non rappresentano in sé dei parametri universali e intrinsecamente caratteristici delle miscele analizzate, in quanto fortemente influenzati dal sistema sperimentale adoperato. Per tali motivi, il presente lavoro di tesi è finalizzato allo sviluppo di uno strumento in grado di analizzare una fiamma di polveri da un punto di vista fondamentale e termocinetico. Tale strumentazione, per come concepita, sarà utilizzabile per la caratterizzazione di miscele ibride (ossia dove polveri e gas infiammabili coesistono) e miscele pure (dove sono presenti solo polveri e ossidante) e potrà essere adoperata per lo sviluppo di modelli cinetici di dettaglio utilizzabili per tali miscele.
Si tratterà l’elaborazione del progetto prima tramite il programma di disegno tecnico AutoCad e poi ne verrà fatta una simulazione computazionale tramite Fluent, al fine di validare lo strumento tramite la combustione di una corrente gassosa di metano e aria. Nella seconda parte, sarà trattata la caratterizzazione di uno dei suddetti parametri di esplosività dal punto di vista sperimentale. Sono state effettuate, infatti, delle prove di esplosività per la determinazione dell’indice di deflagrazione (KST) di una polvere microparticellare di Ferro nel laboratorio del Dipartimento di Scienza Applicata e Tecnologia del Politecnico di Torino.
41
Harrinauth, Reshma K. "Sedimentation of Organic - Inorganic Composites by Optical Turbidity". Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/281.
Testo completoAbstract (sommario):
Sedimentation is one of many characterization tools used to test materials in nanotechnology. Characterization of settling behavior is complex as there are many variables which can affect sedimentation. In our research, we focused on sedimentation in colloidal systems with the aid of an optical turbidometer. Nanoparticles of CeO2 (Ceria Oxide) and TiO2 (Titanium Dioxide) are embedded onto a polymeric matrix of a thermally responsive microgel of poly(N-isopropylacrylamide) (PNIPAM) and interpenetrating chains of poly(acrylic acid) to create novel composites. The composites are loaded with the inorganic oxide nanoparticles at different weight percent from a low value of 10 weight % to 75 weight %. The loading of the colloidal particles affects the sedimentation rate. In this thesis a turbidomenter is used to characterize the settling rate, which is an important characteristic for application of these new composites.
TiO2 is a key constituent in many industrial products; cosmetics, paints, ceramics and used in waste water remediation. It is a potent photocatalyst which breaks down almost any organic compound when exposed to ultraviolet light. By combining nanoparticles of TiO2 with microgels of a polymer, the composites can facilitate use and recovery of the catalyst. Gravity settling of these loaded composites provides an easy separation of TiO2 nanoparticles. In this context, characterization of settling plays an important role. CeO2 composites are used to polish oxide coatings in the semiconductor industry and sedimentation of the composite particles is important as it can affect the efficiency of the planarization process. Therefore, measuring sedimentation of these composites is necessary.
In this study, the settling behavior is measured optically for a variety of conditions that differ in loading of inorganic nanoparticles within the microgels, temperature of the solution, and concentration of particles in solution. The overall goal is to understand the sedimentation behavior of these novel composites and facilitate their use in industrial processes.
42
Dahl, Jan. "Short term water heat storage : studies of velocity and temperature fields and their importance for sizing of the storage". Doctoral thesis, Luleå tekniska universitet, Energivetenskap, 1993. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26541.
Testo completoAbstract (sommario):
Short term water heat storage's have been introduced in many district heating systems. The main reason for this is the possibilities opened by the storage for optimization of the generation of heat and electricity in combined heat and power plants. The basic task for the storage is then to bridge the timevise gap between the heat demand and supply of heat from a cogeneration plant. Water heat storage's can also be useful in district heating systems supplied with industrial waste heat. The water volume in the storage must be stratified to avoid degradation of the quality of the heat that has been charged. Experimental studies of phenomena that influence the stratification and cause a degradation of the quality has been made in model storage's of different sizes The studies include extensive temperature measurements and velocity measurements with different techniques. Laser Doppler Anemometry was used to measure the vertical velocities in the boundary layer at the outer walls. The gradient zone was found to have a strong impact on the velocity field. The maximum velocity in the boundary layer was increasing due to available height up to a certain level where it remained constant. Particle Image Velocimetry Technique were used for measuring the two dimensional velocity field in seeded water in a plane illuminated by a laser. These measurements showed that large scaled convection cells appeared both above and below the gradient zone. The exchange of water between the boundary layer and the core was also shown in these experiments. A video based PIV-technique was developed where a complete charging experiment could be recorded on a video tape. The pictures were analysed in an image processing program which made it possible to evaluate the whole velocity field. On basis of simulations for a case study representing the district heating system in Piteå it was found that heat quality degradation is not essential for the optimization of the storage volume. The different phenomena that influence the quality degradation are important however for optimizing the shape of a storage of a given size. The results from the measurements in the model heat storage's are useful mainly for validation of computer models for numerical prediction of velocity and temperature fields and as a basis for planning of experiments in larger storage's of commercial size. It was therefore decided to include in the study an evaluation of the importance of heat quality degradation for sizing of short term water heat storage's.Godkänd; 1993; 20070313 (ysko)
43
Bergström, Jonas. "Flow Field and Fibre Fractionation Studies in Hydrocyclones". Doctoral thesis, KTH, Fiber- och polymerteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4175.
Testo completoAbstract (sommario):
Hydrocyclones can be used to fractionate fibres according to their papermaking potential. The obtained fractions typically differ in fibre wall thickness and/or degree of fibre treatment. Despite a multitude of potential application scenarios, the process has so far had little commercial success. This is largely explained by the low fractionation efficiency and unfavourable operating characteristics of the process. The fractionation efficiency of a hydrocyclone is closely related to its flow field. The influence of pulp concentration on the tangential velocity field was therefore studied, by using a self-cleaning pitometer. It was found that the pulp concentration had a strong influence on the tangential velocity. At a feed pulp concentration above 7.5 g/l, the suspension rotated almost as a solid body. As a consequence, the magnitude of radial acceleration and shear stresses decreased dramatically. It is suggested that this is detrimental to the fractionation efficiency. The radial velocity field was measured using an Ultrasonic Velocity Profiler. The measurements showed that the rotational centre of the flow field did not correspond with the geometrical centre of the hydrocyclone. This displacement caused the tangential velocity component of the vortex to contribute substantially to the measurement result of the radial velocity component. Based on the findings in respect to the flow field studies, a novel design for a fibre fractionation hydrocyclone was proposed. The flow field inside this hydrocyclone was compared to that in a conventional hydrocyclone. It was found, that high radial acceleration and shear stresses could be maintained in the novel design even at high fibre concentration. The fractionation efficiency of the novel hydrocyclone was characterised in terms of surface roughness difference between fine and coarse fraction. When operated with refined bleached softwood kraft pulp, the novel hydrocyclone could produce fractions with a substantial surface roughness difference without deteriorating the dewatering characteristics of the fine fraction. A low thickening of the reject is proposed to be the explanation for that. When fractionating TMP, the best efficiency occurred at a concentration of 10 g/l.QC 20100804
44
Nucci, Riccardo. "Modelli cinematici per lo studio della deformazione intersismica osservata da misure GPS attraverso le Alpi sud-orientali". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21935/.
Testo completoAbstract (sommario):
La regione delle Alpi sud-orientali è la più sismicamente attiva dell’Italia settentrionale e in passato è stata soggetta a terremoti di magnitudo superiore a 6. In questa tesi si sviluppa, con un nuovo dataset ampliato di misure GPS, uno studio già effettuato al fine di comprendere le principali strutture sismogenetiche dell’area, confrontando diversi modelli cinematici a blocchi atti a rappresentare le velocità osservate in superficie. Questi considerano un numero di blocchi crescente, da quattro a sei, e sono stati costruiti a partire dai cataloghi sismici e di faglie attive noti. Il modello più affidabile è stato scelto sulla base di considerazioni di natura statistica, quali valutazione dei valori di RMSE per le velocità e per mezzo di F test tra i modelli considerati. Da questo, sui sistemi di faglie che bordano i blocchi, si ottengono valori di scorrimento a lungo termine che superano i 2 millimetri per anno sul fronte del blocco delle Alpi orientali e inferiori al millimetro per anno sull’area delle Alpi centrali. Si indaga anche il grado di accoppiamento intersismico nella zona orientale sviluppando un modello a slip distribuito tramite una superficie curvilinea costruita con una mesh a elementi triangolari, i cui risultati sono messi a confronto con quelli ritrovati in passato. Dal confronto emerge un buon accordo complessivo con l’eccezione di un paio di zone centrali che riguardano: un’area a nord dove la copertura dei dati è molto lasca e quindi il risultato non viene considerato attendibile, e la regione del Montello dove la distribuzione di accoppiamento presenta delle differenze spaziali. Quest’ultimo risultato però è vincolato da una migliore copertura dei dati e da una migliore riproduzione degli stessi da parte del modello presentato in questa tesi, suggerendo dei nuovi indizi sul grado di pericolosità sismica della struttura di faglia indagata.
45
Söderholm, Sofia. "Studie av koldioxidgradienter i havets ytskikt". Thesis, Uppsala University, LUVAL, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-106142.
Testo completoAbstract (sommario):
Studie av koldioxidgradienter i havets ytskikt Sofia Söderholm
Denna studie bygger på ett nyligen utvecklat instrument som har mätt koldioxidkoncentrationer på tre olika djup i vattnet samt en nivå i luften. Då detta instrument var oprövat i vatten har en utvärdering av mätmetodens lämplighet för vattenmätningar utförts. Syftet med mätningarna var att undersöka ytvattnets vertikala koldioxidgradient för att med hjälp av denna kunna beskriva flödet av koldioxid mellan hav och atmosfär bättre. Detta flöde är en viktig del av den globala kolcykeln och en djupare förståelse för koldioxidflödets beteende kan i framtiden bidra till mer noggranna klimatprognoser. Hur de beräknade flödena från profilinstrumentet påverkas av temperaturgradienterna i vattnets ytskikt har även det studerats. Mätningarna utfördes i vattnet utanför mätstationen på Östergarnsholm, öster om Gotland. En del av studien fokuserar på de horisontella koldioxidgradienterna i ytvattnet som erhållits genom fartygsdata.
Instrumentet som har använts vid mätningarna bygger på hydrofoba, luftgenomträngliga membran och förefaller fungera mycket väl i vatten. Vid vindhastigheter som inte är högre än 3 - 4 m/s kan tydliga koldioxidgradienter i vattnets ytskikt ses, men detta samband behöver verifieras med en större mängd mätdata. Temperaturgradienten i vattnets ytskikt har ingen större påverkan på vare sig koldioxidgradienten eller flödet av koldioxid och dess effekt kan försummas i detta fall. De horisontella koldioxidgradienterna påverkas huvudsakligen av temperaturen, den biologiska aktiviteten samt transport av vattenmassor. På en större skala kan tydliga effekter av temperaturen på koldioxidhalterna ses och på en mindre skala samt nära kuster och under våren är den biologiska aktiviteten dominerande.
Nyckelord: Koldioxidgradient, koldioxidflöde, temperaturgradient, hydrofoba luftgenomträngliga membran, transferhastighet, vindhastighet, biologisk aktivitet.
A study regarding the carbon dioxide gradients in the surface water. Sofia Söderholm
This study is based on a recently developed instrument that measures the concentration of carbon dioxide at three different depths in the water and one level in the air. Since this instrument has not previously been used for measurements in water, an evaluation regarding the usefulness of the instruments for measurements in water was made. The purpose of the measurements was to study the vertical gradient of carbon dioxide in the surface water and to describe the vertical flux of carbon dioxide between the ocean and the atmosphere in an improved way. This flux is an important part of the global carbon cycle and a deeper understanding of the behavior of the air-sea exchange of carbon dioxide could contribute to more accurate forecasts of the future climate. The impact on the calculated carbon dioxide flux by the temperature gradients in the surface waters was also analyzed. The measurements were performed in the waters outside of the island of Östergarnsholm, east of Gotland. Part of the study focuses on the horizontal carbon dioxide in the surface water, which was obtained by ship data.
The instrument used when performing the measurements is based on hydrophobic, air-permeable membranes and appears to function very well in water. During wind speeds below 3 - 4 m/s distinct carbon dioxide gradients can be seen for the investigated data, but more data is needed to quantify this gradient for different situations. The temperature gradient in the surface water doesn't have a significant effect on the carbon dioxide gradient or the flow of carbon dioxide, and the effect of the temperature gradient can in this particular case be neglected. The horizontal gradients of carbon dioxide are mainly affected by temperature, biological activity and transportation of water mass. On a larger scale the effects of temperature on the concentrations of carbon dioxide are visible and on a smaller scale along with the coastal areas and during springtime, the biological activity is the dominating influence.
Keywords: Carbon dioxide gradient, carbon dioxide flux, temperature gradient, hydrophobic airpermeable membranes , transfer velocity, wind speeds, biological activity.
46
Bianchi, Irene <1981>. "Velocity structure and seismic anisotropy in the crust and upper mantle from Receiver Function analysis: three case studies in Italy". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2614/1/bianchi_irene_tesi.pdf.
Testo completoAbstract (sommario):
The research for this PhD project consisted in the application of the RFs analysis technique to different data-sets of teleseismic events recorded at temporary and permanent stations located in three distinct study regions: Colli Albani area, Northern Apennines and Southern Apennines. We found some velocity models to interpret the structures in these regions, which possess very different geologic and tectonics characteristics and therefore offer interesting case study to face.
In the Colli Albani some of the features evidenced in the RFs are shared by all the analyzed stations: the Moho is almost flat and is located at about 23 km depth, and the presence of a relatively shallow limestone layer is a stable feature; contrariwise there are features which vary from station to station, indicating local complexities. Three seismic stations, close to the central part of the former volcanic edifice, display relevant anisotropic signatures with symmetry axes consistent with the emplacement of the magmatic chamber. Two further anisotropic layers are present at greater depth, in the lower crust and the upper mantle, respectively, with symmetry axes directions related to the evolution of the volcano complex.
In Northern Apennines we defined the isotropic structure of the area, finding the depth of the Tyrrhenian (almost 25 km and flat) and Adriatic (40 km and dipping underneath the Apennines crests) Mohos. We determined a zone in which the two Mohos overlap, and identified an anisotropic body in between, involved in the subduction and going down with the Adiratic Moho. We interpreted the downgoing anisotropic layer as generated by post-subduction delamination of the top-slab layer, probably made of metamorphosed crustal rocks caught in the subduction channel and buoyantly rising toward the surface.
In the Southern Apennines, we found the Moho depth for 16 seismic stations, and highlighted the presence of an anisotropic layer underneath each station, at about 15-20 km below the whole study area. The moho displays a dome-like geometry, as it is shallow (29 km) in the central part of the study area, whereas it deepens peripherally (down to 45 km); the symmetry axes of anisotropic layer, interpreted as a layer separating the upper and the lower crust, show a moho-related pattern, indicated by the foliation of the layer which is parallel to the Moho trend.
Moreover, due to the exceptional seismic event occurred on April 6th next to L’Aquila town, we determined the Vs model for two station located next to the epicenter. An extremely high velocity body is found underneath AQU station at 4-10 km depth, reaching Vs of about 4 km/s, while this body is lacking underneath FAGN station. We compared the presence of this body with other recent works and found an anti-correlation between the high Vs body, the max slip patches and earthquakes distribution. The nature of this body is speculative since such high velocities are consistent with deep crust or upper mantle, but can be interpreted as a as high strength barrier of which the high Vs is a typical connotation.
47
Bianchi, Irene <1981>. "Velocity structure and seismic anisotropy in the crust and upper mantle from Receiver Function analysis: three case studies in Italy". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2614/.
Testo completoAbstract (sommario):
The research for this PhD project consisted in the application of the RFs analysis technique to different data-sets of teleseismic events recorded at temporary and permanent stations located in three distinct study regions: Colli Albani area, Northern Apennines and Southern Apennines. We found some velocity models to interpret the structures in these regions, which possess very different geologic and tectonics characteristics and therefore offer interesting case study to face.
In the Colli Albani some of the features evidenced in the RFs are shared by all the analyzed stations: the Moho is almost flat and is located at about 23 km depth, and the presence of a relatively shallow limestone layer is a stable feature; contrariwise there are features which vary from station to station, indicating local complexities. Three seismic stations, close to the central part of the former volcanic edifice, display relevant anisotropic signatures with symmetry axes consistent with the emplacement of the magmatic chamber. Two further anisotropic layers are present at greater depth, in the lower crust and the upper mantle, respectively, with symmetry axes directions related to the evolution of the volcano complex.
In Northern Apennines we defined the isotropic structure of the area, finding the depth of the Tyrrhenian (almost 25 km and flat) and Adriatic (40 km and dipping underneath the Apennines crests) Mohos. We determined a zone in which the two Mohos overlap, and identified an anisotropic body in between, involved in the subduction and going down with the Adiratic Moho. We interpreted the downgoing anisotropic layer as generated by post-subduction delamination of the top-slab layer, probably made of metamorphosed crustal rocks caught in the subduction channel and buoyantly rising toward the surface.
In the Southern Apennines, we found the Moho depth for 16 seismic stations, and highlighted the presence of an anisotropic layer underneath each station, at about 15-20 km below the whole study area. The moho displays a dome-like geometry, as it is shallow (29 km) in the central part of the study area, whereas it deepens peripherally (down to 45 km); the symmetry axes of anisotropic layer, interpreted as a layer separating the upper and the lower crust, show a moho-related pattern, indicated by the foliation of the layer which is parallel to the Moho trend.
Moreover, due to the exceptional seismic event occurred on April 6th next to L’Aquila town, we determined the Vs model for two station located next to the epicenter. An extremely high velocity body is found underneath AQU station at 4-10 km depth, reaching Vs of about 4 km/s, while this body is lacking underneath FAGN station. We compared the presence of this body with other recent works and found an anti-correlation between the high Vs body, the max slip patches and earthquakes distribution. The nature of this body is speculative since such high velocities are consistent with deep crust or upper mantle, but can be interpreted as a as high strength barrier of which the high Vs is a typical connotation.
48
Zuccarini, Alessandro. "Studio della relazione tra velocità delle onde di taglio, moduli di elasticità e indice dei vuoti di un terreno argilloso in frana". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14410/.
Testo completoAbstract (sommario):
La riattivazione di frane in mezzi geologici deboli ed eterogenei è un fenomeno largamente diffuso e che rappresenta un importante fattore di rischio idrogeologico nell’Appennino emiliano – romagnolo. Nonostante la frequenza di questi fenomeni, risulta poco chiaro e ancora poco conosciuto l’aspetto meccanico delle colate in terra. L’obiettivo di questo elaborato è studiare un campione proveniente dall’area di dissesto di Montevecchio, confrontare i dati di laboratorio con quelli ottenuti attraverso indagini in sito e infine, dalle relazioni ottenute, riuscire a stabilire quale possa essere, in questo specifico caso, il meccanismo che sta alla base del particolare comportamento meccanico del movimento franoso.
49
Kanaki, Kalliopi. "Electric Field and Drift Characteristics Studies for the Multiwire Chambers of the Third Plane of HADES". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29306.
Testo completoAbstract (sommario):
Aim of this report is the investigation of suitable operational conditions for the drif{}t chambers MDC III installed in the HADES setup. The simulations performed showed that operating the drif{}t chambers in a mode with nearly constant electron drif{}t velocity in a predominant part of the cell allows a more precise and fast tracking. This is particularly important for electrons and positrons; here the invariant dilepton mass must be reconstructed with high precision to get a resolution of $\Delta M/M\approx 1\%$ for the $\omega$ and $\phi$ mass peaks and thus a chance to verify also small in-medium mass shif{}ts. This helps to realize the physics program at HADES which focuses on the search for such mass shif{}ts to get insight into the in-medium behaviour of hadrons in dense strongly interacting matter.
50
Kanaki, Kalliopi. "Electric Field and Drift Characteristics Studies for the Multiwire Chambers of the Third Plane of HADES". Forschungszentrum Rossendorf, 2003. https://hzdr.qucosa.de/id/qucosa%3A21758.
Testo completoAbstract (sommario):
Aim of this report is the investigation of suitable operational conditions for the drif{}t chambers MDC III installed in the HADES setup. The simulations performed showed that operating the drif{}t chambers in a mode with nearly constant electron drif{}t velocity in a predominant part of the cell allows a more precise and fast tracking. This is particularly important for electrons and positrons; here the invariant dilepton mass must be reconstructed with high precision to get a resolution of $\Delta M/M\approx 1\%$ for the $\omega$ and $\phi$ mass peaks and thus a chance to verify also small in-medium mass shif{}ts. This helps to realize the physics program at HADES which focuses on the search for such mass shif{}ts to get insight into the in-medium behaviour of hadrons in dense strongly interacting matter.