Dissertations / Theses on the topic 'L-beams'
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Shetty, Suhas Gururaj. "Failure Modeling of Curved Composite Beams : Numerical Modeling of Failure Onset and Propagation in L-Profile Beams." Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244415.
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The high strength/stiffness-to-weight ratio that composite materials exhibit has led to the utilization of composites as alternative to traditional materials in weight-critical applications. However, the highly anisotropic nature of composites renders the strength prediction under complex loading challenging. To efficiently predict the failure of composite structures especially in cases where out-of-plane stresses are dominant, the modeling of damage onset and propagation plays an essential role in accurate strength predictions.Firstly, in this Thesis work the analysis of a composite L-profile, which is loaded such that significant out-of-plane stresses are generated in the curved region, is conducted. However, the inherent heterogeneity at the micro/meso scale is not modeled for the stress analysis.Secondly, in this project the target was to accurately predict the initiation of failure at the ply level, modal based Puck’s matrix failure criteria have been implemented to the failure analysis. Maximum stress failure criteria were however retained to check the possible fiber-based failure which is not directly captured with in Puck’s failure criterion.Thirdly, Cohesive Zone Material Model has also been employed to model the growth of interlaminar damage (delamination). The delamination study is based on the Inter Fibre Fracture crack initiation and doesn’t include other causes like edge effects, voids, manufacturing defects etc.Finally, the attempt to validate the analysis results with the available test results was made. Further development of the existing model and several tests are required to be carried out for material characterization and complete validation of the developed damage model for composite structure.
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Pastore, Marcus Vinícius Filiagi. "Contribuição ao projeto de vigas delgadas de seção \"L\" de concreto pré-moldado." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03092015-085641/.
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Esta dissertação tem por objetivo contribuir para o projeto estrutural de vigas delgadas de seção \"L\" de concreto pré-moldado, também conhecidas no Brasil como vigas suporte-peitoril. O projeto deste tipo de viga apresenta uma maior complexidade que o de vigas usuais pela seção transversal assimétrica, carregamento excêntrico e as várias possibilidades de ligações viga-pilar e viga-laje. Em função de sua ligação com a laje, o comportamento deste tipo de viga pode apresentar diferentes modelos: a) com torção de equilíbrio; b) sem torção de equilíbrio; e c) com restrição parcial da rotação da laje. É mostrado que para relações altura da viga/largura da mesa inferior maiores que 2,5, a variação da orientação dos eixos principais de inércia com relação aos eixos vertical e horizontal pode ser desprezada. Além disso, o centro de cisalhamento pode ser considerado situado na linha de centro da alma para grandes relações altura da viga/altura da aba. Também são discutidas as ações e efeitos a serem considerados no projeto de vigas de seção \"L\". Em relação ao estado limite último, é mostrado que os procedimentos de dimensionamento de momento fletor e força cortante não diferem dos outros tipos de vigas de concreto, entretanto, o momento de torção pode ser tratado como flexão de placa por um método recomendado na última revisão do ACI-318. O comportamento da ligação alma/aba é considerado como dente de concreto e os seguintes aspectos de seu dimensionamento são apresentados: cálculo do tirante, cálculo da suspensão, cálculo da armadura longitudinal e verificação da biela crítica. Além disso, é levada em conta a resistência à punção da aba para efeito de forças concentradas. Também são discutidas as considerações para a flexão do peitoril que pode ocorrer pela ação lateral do vento e do impacto de veículos. Em relação ao estado limite de serviço, são apresentadas duas situações exclusivas para vigas de seção \"L\" com peitoril alto e delgado: formação de fissuras na extremidade e deformação lateral excessiva. Por fim, um exemplo de aplicação é desenvolvido para ilustrar particularidades no dimensionamento de vigas delgadas de seção \"L\" de concreto pré-moldado.This thesis aims to contribute to the structural design of precast concrete slender L-shaped beams, also known as facade beams, spandrel beams, L-shaped edge beams and others. The design of these beams shows a greater complexity than usual concrete beams due to the asymmetric cross section, eccentric loads and the various possibilities for beam-column and beam-slab connections. According to their connection with the slab, the beam behavior can be divided into different models: a) with equilibrium torsion; b) without equilibrium torsion; c) with partial restriction of the slab rotation. It is shown that for height-to-total width ratios larger than 2.5, the variation of the orientation of the principal axes with respect to the vertical and horizontal axes can be neglected. Furthermore, the shear center can be considered located at the web center line for high values of the beam height-to-ledge height ratio. It is also discussed the actions and effects to be considered in the design of L-shaped beams. Regarding the ultimate limit state, it is shown that the bending moment and shear force procedures do not differ from other types of concrete beams, however, the torsion can be treated as plate bending by a recent method recommended in the latest ACI-318 revision. The ledge is considered as dapped end beams and the following aspects of its design are presented: transverse bending; hanger requirements; longitudinal bending and shear strength, including punching shear. It is also discussed the considerations for web flexure that may occur by wind action and lateral vehicle impact. Regarding the serviceability limit state, it is presented two unique situations for precast concrete slender L-shaped beams: crack formation at end regions and excessive lateral deflection. Lastly, an example is developed to illustrate particularities of the precast concrete slender L-shaped beam design.
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Scott, Jonathan Paul. "First direct measurement of Fâ†L using ISR events in deep inelastic scattering at HERA." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326678.
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Ferri, Lorenzo. "Il metodo del beam-forming acustico." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8735/.
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Nel corso di questa tesi si svilupperà il metodo del Beam-forming acustico, uno dei più semplici algoritmi di elaborazione segnale che permette di isolare spazialmente un suono proveniente da una precisa direzione decisa da noi, creando quindi un microfono super-direzionale orientabile a partire da un array microfonico di caratteristiche note.
Inoltre si implementerà in modo pratico l'algoritmo per descrivere il livello sonoro emesso da ogni punto di una sorgente sonora estesa in modo da mappare l'intensità di quest'ultima in un'immagine 2D da sovrapporre all'immagine stessa dell'oggetto.
Volendo schematizzare in breve questa tesi, essa è composta da una prima parte teorica contenente gli argomenti che ci servono per descrivere lo spazio acustico e le onde acustiche, una seconda parte riguardante i microfoni e i suoi vari parametri, una terza parte riguardante la teoria sull'elaborazione segnale nel dominio del tempo e delle frequenze e in particolare cenni sulla trasformata di Fourier.
Nella parte successiva verranno descritti i due principali metodi di Beam-forming acustico trattando sia gli apparati di misura sia i due algoritmi, facendo sempre riferimento alle parti di teoria necessarie alla spiegazione del metodo.
Infine nell'ultima parte della tesi verrà discusso in primo luogo la creazione del microfono virtuale, in particolare parleremo della sua sensibilità in funzione della direzione avvalendoci di uno schema che in letteratura viene denominato Beam-pattern, in secondo luogo parleremo di come creare la mappa 2D dove effettivamente possiamo vedere l'intensità sonora dell'onda proveniente da ogni punto dell'oggetto preso in considerazione.
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Hashtroodi, Seyedowjan. "Crack Propagation Analysis of a Pre-stressed L-shaped Spandrel Parking Garage Beam." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1420753991.
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Moreno, Tinjaca Maria Alexandra. "Effect of electron beam irradiation on quality and shelf-life of Tommy Atkins mango (Mangifera indica l.) and blueberry (Vaccinium corymbsum l.)." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4726.
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The main goal of this research was to determine the feasibility of using electron
beam irradiation as an alternative disinfestation technology while preserving the overall
quality of mangoes, and to verify its suitability for the preservation shelf life of
blueberries.
Physicochemical and sensory characteristics of the fruits were evaluated.
Mangoes were irradiated at 1.0, 1.5 and 3.1 kGy using a 10MeV (10 kW) linear
accelerator (LINAC) with double beam fixture. Samples were stored at 12úC and 62.7%
RH for 21 days. Blueberries packed in plastic clamshell containers were irradiated at 1.1,
1.6 and 3.2 kGy doses using the same linear accelerator with a single beam. The shelf
life of the berries stored at 5úC and 70.4% RH was evaluated for 14 days. The firmness
of mangoes irradiated at 1.5 and 3.1 kGy significantly (p > 0.05) decreased during
storage. There was a reduction of total sugars (8.1% and 14.1%) in samples irradiated at
1.0 kGy and 1.5 kGy, respectively. All irradiated mangoes had significantly lower (50- 70 %) ascorbic acid content throughout storage. The phenolic compounds increased in
samples irradiated at 1.5 kGy (27.4%) and 3.1 kGy) (18.3%). Sensory evaluation of the
fruits irradiated with 3.1 kGy showed significantly less acceptability for overall quality,
color, texture and aroma. Irradiation of blueberries at 1.1 kGy had no significant (p >
0.05) effect on the fruits' physicochemical characteristics with the exception of ascorbic
acid which decreased by 17% after 14 days. A significant decrease in texture (firmness)
of irradiated berries was observed during storage time. Total sugars decreased in all
irradiated fruits while total phenolics and tannins increased (10 -20%). Sensory attributes
of samples irradiated with 1.1 kGy and 1.6 kGy were found acceptable by the panelists.
The high dose-treated fruits were considered unacceptable.
The results from this research suggest that a 1.5 kGy is the best treatment to
maintain the quality attributes of mangoes and increase the shelf life by three days. The
electron beam irradiation of packed blueberries at doses of 1.1 and 1.6 kGy ensures and
enhances the quality and the shelf life of blueberries up to 14 days.
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Capoani, Federico. "Adiabatic extraction models for beam dynamics." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12056/.
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Il presente lavoro prende le mosse da un problema di dinamica
dei fasci relativo a un metodo di separazione di un fascio di particelle recentemente messo in funzione nell’sincrotrone PS al CERN. In questo sistema, variando adiabaticamente i parametri di un campo magnetico, nello spazio delle fasi si creano diverse isole di stabilità (risonanze) in cui le particelle vengono catturate.
Dopo una parte introduttiva in cui si ricava, a partire dalle equazioni di Maxwell, l’hamiltoniana di una particella sottoposta ai campi magnetici che si usano negli acceleratori, e una presentazione generale della teoria dell’invarianza adiabatica, si procede analizzando la dinamica di tali sistemi.
Inizialmente si prende in considerazione l’hamiltoniana mediata
sulle variabili veloci, considerando perturbazioni (kick) dei termini dipolare e quadrupolare. In ognuno dei due casi, si arriva a determinare la probabilità che una particella sia catturata nella risonanza.
Successivamente, attraverso un approccio perturbativo, utilizzando le variabili di azione ed angolo, si calcola la forza della risonanza 4:1 per un kick quadrupolare.
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Pause, Marion. "Soil moisture retrieval using high spatial resolution Polarimetric L-Band Multi-beam Radiometer (PLMR) data at the field scale." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-132176.
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Chang, Patrick. "An improved size, matching, and scaling synthesis method for the design of meso-scale truss structures." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41138.
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The recent improvement of additive manufacturing has allowed designers to achieve a level of complexity and customizability that is difficult or impossible to accomplish using traditional manufacturing processes. As a result, much research has been conducted on developing new methods to utilize the larger design space brought by additive manufacturing. One such research area is in the design of mesoscale lattice structures. Mesoscale lattice structures are a type of cellular structure with support element sizes on the order of magnitude of centimeters. These types of structures are engineered for high performance and have applications in industries where both low weight and high strength are desired. However, due to the small size of their struts, these structures can easily have hundreds to thousands of individual struts. As a result, design poses a unique challenge. Current methods approach design of mesoscale lattice structures as a topological optimization problem, treating each strut diameter in the structure as a design variable. For structures with a fewer number struts, these optimization methods can converge, but will generally be very time-consuming. For structures with a large number of struts, the optimization problem becomes too large for current algorithms to solve.
In previous research, a new, highly efficient design method for mesoscale lattice structures was presented that eliminates the need for global size or topological optimization. This method, termed the Size, Matching and Scaling method, used a unique combination of a solid-body finite element analysis and a library of pre-defined lattice configurations, termed the "unit-cell library," to generate lattice topologies. The results from this method were highly promising: design time was significantly reduced when compared to optimization methods. Furthermore, lattices designed using the SMS method had performance results that were either comparable or better than their optimized counterparts. However, the method developed was highly conceptual, lacking a true systematic methodology for generating topologies and suffering from some gaps in implementation.
In this research, we present a modified Size Matching and Scaling (SMS) design method. Firstly, we introduce and outline the modified methodology. This methodology particularly includes an optimization step for determining strut diameters that replaces the manual search used in the original method. Secondly, we expand and explore the unit-cell library in an attempt to improve the performance of lattices generated using the SMS method. In particular, we optimize several unit-cell configurations and compare their performance in the context of the SMS method. Finally, we test the updated SMS methodology and unit-cell library using various design examples.
Results from the various example problems indicate that optimization is not only a viable systematic method for determining diameter values, but is actually preferred to the manual, iterative process used in the original method. Furthermore, various optimization algorithms and approaches yield different results. Between the two optimization algorithms utilized in this method: constrained optimization and least-squares minimization, constrained minimization converges faster, but least-squares minimization yields slightly improved performance results. In addition to these algorithms, a one-variable approach using an untested, simplifying assumption, dubbed the "28% approach," was tested. Results indicate that this assumption was incorrect and cannot be utilized. Finally, results from the expanded unit-cell library indicate that the best unit-cell configuration is still the same original unit-cell configuration utilized in the first SMS method. The addition of more unit-cell does not improve the performance of structures generated using the SMS method. In fact, both performance and design time worsen when additional configurations are utilized.
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Carlini, Gianluca. "Artefatti di ricostruzione nella tomografia computerizzata con raggi X." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16933/.
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Gli artefatti da ricostruzione sono problemi comuni nella tomografia computerizzata con raggi X. Essi possono degradare la qualità di una immagine al punto da renderla inutilizzabile. Scopo dell’elaborato è l’analisi di diversi tipi di artefatti, a partire dai fenomeni che li causano, fino ad arrivare ai metodi impiegati per eliminarli o quantomeno ridurli. A tal fine si è proceduto ad una approfondita ricerca bibliografica e allo studio dei testi scientifici fondamentali riguardo all’argomento. Particolare attenzione è stata rivolta al fenomeno fisico del Beam Hardening, che è tra le maggiori cause di artefatti grafici, e di cui si sono viste diverse metodologie di correzione. Sono stati poi trattati gli artefatti dovuti all’apparato di misura e gli artefatti dovuti al paziente. Per quanto riguarda le tecniche di correzione, oltre ai procedimenti di più vecchia concezione e ormai consolidati, si è dato largo spazio alle metodologie innovative, di recente applicazione e ancora oggetto di studio e ricerca, come la Dual-Energy CT e la ricostruzione iterativa. Si è visto come la ricostruzione iterativa garantisca risultati di gran lunga superiori in merito alla qualità dell’immagine ricostruita, rispetto alla canonica Filtered Back-Projection, in particolare per quanto riguarda la Low-dose CT, di grande interesse in campo medico.
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Francini, Letizia. "Principi di funzionamento della Tomografia Computerizzata a Fascio Conico e settori di utilizzo." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4053/.
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Palazzi, Emanuele. "Analisi sperimentale e progettazione di cinematismi atti alla movimentazione di devices protesici all’interno di una camera di deposizione pvd." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11563/.
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analisi sperimentale e progettazione di cinematismi atti alla movimentazione di devices protesici all’interno di una camera di deposizione pvd.
descrizione delle tecniche di deposizione PVD attualmente esistenti.
deduzione e progetto ex novo, con l'ausilio di Autodesk Inventor (CAD 3D), di movimentazioni per particolari devices medici dalla geometria complessa all'interno di una speciale camera di deposizione.
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Fusillo, Elena. "Un sistema tomografico trasportabile per indagini in situ di opere d’arte." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15417/.
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Questo lavoro di tesi si inquadra nel progetto dell’Istituto Superiore per la Conservazione ed il Restauro (I.S.C.R.) di Roma denominato "MATEGIAPPI", per il quale il museo romano L. Pigorini ha messo a disposizione la propria collezione di tredici maschere teatrali giapponesi al fine di utilizzare tecniche non distruttive e microdistruttive per l’individuazione dei materiali e delle tecniche di esecuzione e costruzione, per la valutazione del degrado e per definire e misurare le dimensioni dei manufatti.
In questo senso é stato fondamentale ricorrere all’uso della tomografia computerizzata, tecnica assolutamente non invasiva ed efficace nell’indagare la struttura interna degli oggetti esaminati. Per l’esecuzione delle analisi si é adoperato un apparato tomografico trasportabile con sorgente a raggi X sviluppato ad hoc dal Dipartimento di Fisica e Astronomia dell’Universitá di Bologna per misurazioni ed analisi nell’ambito dei Beni Culturali.
Il sistema, potenziato nel corso degli anni, consiste in un tubo a raggi X, un rivelatore flat-panel montato su due assi motorizzati e una tavola rotativa. In particolare, in questo lavoro si é apportata un’innovazione mediante l’aggiunta di un ulteriore asse motorizzato capace di movimentare la sorgente lungo l’asse verticale.
Si presentano qui le ricostruzioni tomografiche di due delle tredici maschere, le quali sono state svolte prestando particolare attenzione all’eliminazione di eventuali artefatti, che peggiorerebbero la qualitá dei volumi prodotti dal rendering 3D.
Va inoltre sottolineato che un altro importante scopo del progetto é quello di poter valorizzare la collezione mediante presentazione al pubblico di immagini, video e modelli tridimensionali.
É intenzione congiunta del gruppo bolognese di imaging a raggi X e dei restauratori delle opere allestire una mostra dedicata alla collezione che possa affiancare alle maschere le indagini scientifiche svolte.
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Pause, Marion [Verfasser], and Karsten [Akademischer Betreuer] Schulz. "Soil moisture retrieval using high spatial resolution Polarimetric L-Band Multi-beam Radiometer (PLMR) data at the field scale / Marion Pause. Betreuer: Karsten Schulz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1015083978/34.
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Paladino, Mattia. "Test su un prototipo di rivelatore per la misura di sezione d’urto del neutrino elettronico." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16826/.
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Il neutrino è una particella fondamentale del Modello Standard, è stata scoperta nel 1956 e col passare degli anni si venne a conoscenza del fatto che questi sono caratterizzati da una rispettiva antiparticella e da tre tipi di sapore. La fisica dei neutrini è tuttavia ancora ricca di incomprensioni: molte delle proprietà che descrivono queste particelle risultano ancora sconosciute.
Il progetto ENUBET propone un’iniziativa con lo scopo di far luce su alcuni dei misteri che circondano le nostre conoscenze sui neutrini e sarà il protagonista di questo elaborato.
Nel primo capitolo si farà un’introduzione sulla scoperta dei neutrini e sulle proprietà che li descrivono.
Nel secondo capitolo, si introdurranno gli scopi del progetto ENUBET e verrà descritto il modo in cui questo progetto ha intenzione di approcciarsi alle problematiche legate alle incertezze sul flusso ed alla misura della sezione d’urto; inoltre si discuterà delle tecniche adottate dal progetto per raggiungere i propri obiettivi.
Nel terzo capitolo verrà descritta l’attività di laboratorio da me svolta presso la sede dell’INFN di Bologna, nella quale ho assistito alla costruzione di un prototipo di calorimetro destinato ad essere sottoposto ad un test beam presso il CERN di Ginevra.
Successivamente verrà discussa l’analisi dei dati prodotti dal suddetto test ed elaborati attraverso l’utilizzo del software ROOT.
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Lombardi, Paolo. "Sviluppo e implementazione di una legge di guida per veicoli terrestri." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5205/.
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Plassard, Fabien. "Optics optimization of longer L* Beam Delivery System designs for CLIC and tuning of the ATF2 final focus system at ultra-low β* using octupoles." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS122/document.
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Un défi important pour les futurs collisionneurs linéaires électron-positron est de pouvoir focaliser le faisceau à des tailles transverses de l’ordre du nanomètre au point d’interaction (IP), permettant d’atteindre la luminosité de conception. Le système délivrant les faisceaux d’e- et de e + de la sortie du Linac principal vers le point d’interaction, le Beam Delivery System (BDS), réalise les fonctions critiques requises pour atteindre l’objectif de luminosité, tel que la collimation et la focalisation du faisceau. Le faisceau est focalisé par le système de focalisation finale (FFS) tout en corrigeant les aberrations d’ordre supérieur propagées le long du système. Les effets chromatiques contribuant à l’élargissement de la taille du faisceau, sont amplifiés par la force de focalisation des deux derniers quadripôles QF1 et QD0, ou doublet final (FD), et par la longueur de la distance focale finale L* entre QD0 et l’IP. L’approche de correction de la chromaticité retenue pour les deux grands projets actuels de collisionneurs linéaires, CLIC et ILC, est fondée sur la correction locale de la chromaticité générée par le doublet final. Ce schéma est actuellement testé à l’ATF2 au KEK (Japon). Ce travail de thèse se concentre sur les problématiques liées au système de focalisation finale du projet CLIC re-optimisé avec un plus long L*, dans le cadre de la simplification de l’interface machine-détecteur (MDI), ainsi que sur le travail expérimental conduit à l’ATF2 pour l’optimisation et l’étude des optiques du système de focalisation finale à ultra-bas β* incluant les tout premiers est in situ des octupôles à l’ATF2The future machines considered to carry out high precision physics in the TeV energy regime are electron-positron (e+e−) linear colliders. Future linear colliders feature nanometer beam spot sizes at the Interaction Point. The Beam Delivery System (BDS) transports the e + and e− beams from the exit of the linacs to the IP by performing the critical functions required to meet the CLIC luminosity goal such as beam collimation and focusing. The beam is focused through the Final Focus System while correcting higher order transport aberrations in order to deliver the design IP beam sizes. The chromatic contributions are amplified by the focusing strength of the two last quadrupoles named QD0 and QF1, reffered to as the Final Doublet (FD), and by the length of the final focal distance L* between QD0 and the IP. The chromaticity correction approach chosen for the CLIC FFS is based on the Local chromaticity correction scheme which uses interleaved pairs of sextupole magnets in the FD region in order to locally and simultaneously correct horizontal and vertical chromaticity. The current linear collider projects, the Compact Linear Collider (CLIC) and the International Linear Collider (ILC) have FFS lattices based on the Local Chromaticity correction scheme. This scheme is being tested in the Accelerator Test Facility 2 (ATF2) at KEK (Japan). This thesis concentrates on problems related to the optimization of BDS lattices for the simplification of the CLIC Machine Detector Interface (MDI) and on the experimental work for the implementation and study of a CLIClike FFS optics for the ATF2, referred to as ultra-low β* optics
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Ostendi, Chiara. "Sviluppo di un metodo di correzione del beam-hardening senza calibrazione preliminare per la tomografia a raggi X di tipo cone-beam applicata ai beni culturali." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24277/.
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L’obbiettivo di questa tesi è lo sviluppo di un algoritmo, applicabile all’ambito dei Beni Culturali, per la correzione dell’artefatto del beam hardening, il quale genera un deterioramento della qualità delle immagini ottenute tramite la tomografia computerizzata a raggi X.
Dopo una breve spiegazione dei principi fisici alla base di questa tecnica viene illustrato l’algoritmo di correzione sviluppato presso l’X-Ray Imaging Group del Dipartimento di Fisica e Astronomia “Augusto Righi” dell’Università di Bologna. Questo è basato sul calcolo dei percorsi di attenuazione dei raggi X attraverso la retroproiezione di una sezione dell’oggetto reale e sulla successiva linearizzazione dei dati ottenuti. L’algoritmo non comprende una fase di calibrazione preliminare, caratteristica molto utile nell’ambito dei beni culturali in cui spesso questa operazione non è effettuabile. Sono mostrati successivamente i risultati ottenuti in seguito all’applicazione a due oggetti di test.
Sono infine riportate l’implementazione dell’algoritmo all’interno del software di ricostruzione PARREC e i risultati della successiva applicazione a casi studio reali, in particolare a una statuetta moderna in bronzo e a olle in terracotta di epoca villanoviana.
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Bagnari, Alessandro. "Triggers per attività di test su fascio di particelle. Realizzazione di un progetto in VHDL e sintetizzazione su FPGA." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/591/.
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Progettazione e realizzazione di un dispositivo elettronico con lo scopo di coordinare e sincronizzare la presa dati del beam test del LUCID (CERN, luglio 2009) e tener traccia di tali eventi. Il circuito è stato progettato in linguaggio VHDL, simulato con il programma ModelSim, sintetizzato con il programma Quartus e implementato su un FPGA Cyclone residente su scheda di tipo VME 6U della CAEN. Infine la scheda è stata testata in laboratorio (verificandone il corretto funzionamento) assieme all'intero sistema di presa dati, e confermata per il beam test del LUCID.
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Petersen, Renata C?rdova. "Avalia??o em tomografia cone beam da regi?o de caninos inferiores e primeiros molares superiores em pacientes com e sem fissura labiopalatina." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2017. http://tede2.pucrs.br/tede2/handle/tede/7551.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Cleft lip and palate are common birth defects. Cleft patient undergone many surgical procedures in the midface, in early ages, that may affect the facial growth. This can result in midface deficiency and class III malocclusion that requires protraction of the maxila or surgical treatment. The maxillary advancement is the main procedure performed to treat patients with midface retrusion. One of the treatment alternatives, consists of using skeletal anchorage and elastics. However, these patients with cleft lip and palate usually present a nutritional deficiency in the early childhood, leading us to question about a possible compromise of their bone quality. The aim of this research was to evaluate the bone condition in the lower Canine regions (distal and mesial) and upper permanent first molars (mesial) using Cone Beam CT in individuals with and without cleft lip and palate, with and without growth potential. No statistical significant differences were found in the measures evaluated among the three groups. The values of cortical thickness and Gray Scale were similar in patients with and without cleft lip and palate, and with growth potential, when compared to adults. Therefore, patients with growth potential and cleft lip and palate have the same bone conditions for receiving mini implants as the adult patients without cleft lip and palate.
Fissuras labiopalatinas sa?o defeitos conge?nitos que atingem a face do ser humano, sendo estabelecidas precocemente na vida intrauterina. Esses pacientes, ap?s a repara??o da fissura labial, acabam tendo o seu crescimento maxilar limitado o que frequentemente os deixa com a maxila atr?sica e um perfil c?ncavo, com necessidade de um tratamento que promova o avan?o maxilar e o recuo mandibular. Uma das alternativas de tratamento atuais, consiste na coloca??o de ancoragem esquel?tica na regi?o superior posterior e inferior anterior para uso de el?sticos intermaxilares. No entando, esses pacientes portadores de fissuras labiopalatinas, costumam apresentar uma defici?ncia nutricional na primeira inf?ncia levando-nos a questionar sobre um poss?vel comprometimento da sua qualidade ?ssea. Sendo assim, foram avaliadas, atrav?s da Tomografia Cone Beam, as regi?es distal e mesial dos caninos permanentes inferiores e mesial dos primeiros molares permanentes superiores, em indiv?duos com e sem fissura l?bio palatal, com e sem potencial de crescimento. Nesse estudo n?o foram encontradas diferen?as estatisticamente significativas nas medidas avaliadas entre os tr?s grupos. A espessura da cortical e a qualidade ?ssea, avaliada pela Escala de Cinza, nas regi?es avaliadas foram semelhantes em pacientes com e sem fissura labiopalatina e tamb?m ao grupo composto por pacientes adultos. Logo, pacientes em crescimento e com fissura labiopalatina, apresentaram as mesmas condi??es ?sseas para o recebimento de mini implantes do que os pacientes adultos e sem fissura labiopalatina.
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Magnani, Marco. "Modellazione solida e beam per strutture lattice." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
Presentazione di un metodo semplificativo per l’analisi di un campione lattice a celle ottaedriche, partendo dalla ricerca di un modo per accorciare i tempi di simulazione necessari a condurre analisi FEM su strutture cellulari.
Viene effettuata una modellazione beam delle micro travi e le strutture vengono sottoposte a simulazioni già condotte con campioni aventi la stessa geometria, ma una modellazione solida. I risultati delle due analisi vengono confrontati e, quando possibile, paragonati a risultati sperimentali. Si conclude che la modellazione proposta permette di accorciare i tempi di simulazione e di modellazione CAD, oltre a rendere possibile condurre analisi ai grandi spostamenti ottenendo risultati molto più simili a quelli ricavati in laboratorio, grazie alla riduzione della potenza di calcolo richiesta.
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Poluzzi, Giacomo. "Modellazione e simulazione dell’interazione suolo-carrello per velivoli ad ala fissa." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22336/.
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L'obiettivo della presente tesi è illustrare lo sviluppo di un modello numerico che permetta di descrivere il comportamento di un carrello triciclo ad utilizzo aeronautico.
Per descrivere il comportamento del velivolo durante le manovre di rullaggio, è stato studiato un sistema di sterzo ed un modello di attrito tra pneumatico e suolo. Il sistema di sterzo è stato automatizzato tramite un controllore PD, utilizzando un sistema di guida di tipo "Beam rider".
La validazione è stata effettuata tramite il software Matlab-Simulink. Sono stati simulati due drop test con condizioni iniziali differenti ed è stata simulata una manovra di rullaggio. Sono stati ottenuti risultati soddisfacenti, ottenendo grandezze e comportamenti del velivolo plausibili.
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Bashtova, Kateryna. "Modélisation et identification de paramètres pour les empreintes des faisceaux de haute énergie." Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4112/document.
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Le progrès technologique nécessite des techniques de plus en plus sophistiquées et précises de traitement de matériaux. Nous étudions le traitement de matériaux par faisceaux de haute énergie : un jet d’eau abrasif, une sonde ionique focalisée, un laser. L’évolution de la surface du matériau sous l’action du faisceau de haute énergie est modélisée par une EDP. Cette équation contient l’ensemble des coefficients inconnus - les paramètres de calibration de mo- dèle. Les paramètres inconnus peuvent être calibrés par minimisation de la fonction coût, c’est-à-dire, la fonction qui décrit la différence entre le résultat de la modélisation et les données expérimentales. Comme la surface modélisée est une solution du problème d’EDP, cela rentre dans le cadre de l’optimisation sous contrainte d’EDP. L’identification a été rendue bien posée par la régularisation du type Tikhonov. Le gradient de la fonction coût a été obtenu en utilisant les deux méthodes : l’approche adjointe et la différen- ciation automatique. Une fois la fonction coût et son gradient obtenus, nous avons utilisé un minimiseur L-BFGS pour réaliser la minimisation.Le problème de la non-unicité de la solution a été résolu pour le problème de traitement par le jet d’eau abrasif. Des effets secondaires ne sont pas inclus dans le modèle. Leur impact sur le procédé de calibration a été évité. Ensuite, le procédé de calibration a été validé pour les données synthétiques et expérimentales. Enfin, nous avons proposé un critère pour distinguer facilement entre le régime thermique et non- thermique d’ablation par laserThe technological progress demands more and more sophisticated and precise techniques of the treatment of materials. We study the machining of the material with the high energy beams: the abrasive waterjet, the focused ion beam and the laser. Although the physics governing the energy beam interaction with material is very different for different application, we can use the same approach to the mathematical modeling of these processes.The evolution of the material surface under the energy beam impact is modeled by PDE equation. This equation contains a set of unknown parameters - the calibration parameters of the model. The unknown parameters can be identified by minimization of the cost function, i.e., function that describes the differ- ence between the result of modeling and the corresponding experimental data. As the modeled surface is a solution of the PDE problem, this minimization is an example of PDE-constrained optimization problem. The identification problem was regularized using Tikhonov regularization. The gradient of the cost function was obtained both by using the variational approach and by means of the automatic differentiation. Once the cost function and its gradient calculated, the minimization was performed using L-BFGS minimizer.For the abrasive waterjet application the problem of non-uniqueness of numerical solution is solved. The impact of the secondary effects non included into the model is avoided as well. The calibration procedure is validated on both synthetic and experimental data.For the laser application, we presented a simple criterion that allows to distinguish between the thermal and non-thermal laser ablation regimes
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Lepourry, Clémence. "Mise au point et caractérisation d’un système innovant de poutre hybride béton-acier : étude des comportements locaux et globaux." Thesis, Rennes, INSA, 2019. http://www.theses.fr/2019ISAR0016.
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L’objectif principal de cette thèse de doctorat est le développement et la caractérisation d’un procédé de poutres de grandes portées adapté aux entreprises de gros œuvre. En effet, les technologies industrielles existantes pour répondre à des franchissements importants ne sont pas en accords avec le savoir-faire des équipes chantiers. Dès lors, le groupe Legendre, par sa filiale Ingénova, a souhaité mettre au point une solution, simple de par sa mise en œuvre sur chantier, et qui vise un niveau d’exigence structurelle similaire aux technologies actuelles. Composée d’une poutre béton armé renforcée par une peau métallique extérieure, la poutre hybride béton-acier est la solution étudiée au sein de ce mémoire pour répondre à cette problématique. Pour assurer l’équilibre des efforts entre les deux matériaux, un système de connexion inédit a été développé. La caractérisation expérimentale n’ayant validé que deux dimensions de connecteurs, le modèle numérique a permis d’étendre l’étude et ainsi, déterminer une formule de dimensionnement généralisée. Le comportement local de la poutre connu, les investigations expérimentales se sont orientées sur la réponse de la poutre soumise à une flexion positive. L’impact de la connexion partielle en comparaison de la connexion complète a été quantifié à la fois sur la résistance de la poutre et sur ses déformations. Le modèle numérique, calibré sur les résultats des essais, a permis de valider l’utilisation de modèles analytiques issus de la littérature, adaptés au cas de la poutre hybride. Enfin le dernier volet de cette thèse concerne l’assemblage de la poutre hybride béton-acier avec un poteau mixte acier-béton tubulaire. Après une série d’essais pour caractériser la résistance et la rigidité de ce joint innovant, un modèle numérique de cette configuration a mis en évidence les transferts d’efforts nécessaires entre les deux matériaux. Ces derniers complètent le mode de fonctionnement classique de l’assemblage qui superpose à la fois un comportement béton armé et un comportement métallique. Un modèle analytique, développée au sein de cette thèse, a confirmé le dimensionnement de l’assemblage.Les résultats présentés dans ce mémoire ont été suffisants pour tester le procédé de poutre hybride béton-acier sur un chantier pilote. Le gain de la solution en comparaison aux technologies existantes a été confirmé par les équipes chantiersThe main goal of this Ph.D thesis is the development and the characterization of a solution for long-span beams in concrete buildings. Pre-stressed or composite beams are the possible technologies for beams up to twenty metres, but they are not adapted for concrete constructors. The main objective of Ingenova, the research and development affiliate of Legendre is to find a solution, which can be set up easily by concrete workers with good structural performance. The proposed solution is the concrete-steel hybrid beam, made of U-shape steel profile used as permanent formwork to encase a concrete beam. The association of the two beams also gives a convenient solution adapted to concrete builders. In this thesis, a series of experimental and numerical tests have been performed in order to assess the global and the local behaviour of the beam and its connections.Firstly, the connexion between concrete and steel is achieved by L-shaped angles welded on the upper flanges of the steel beam. Their behaviour has been studied by performing asymmetric push-out tests, which were used to validate a detailed finite element model. Based on the results obtained from a numerical parametric study of the validated a finite element model, an analytical expression of the shear resistance was then proposed.The global behaviour in sagging of the concrete-steel hybrid beam was also investigated by experimental and numerical tests. The impact of the partial interaction under deflection and bending moment resistance have been studied. The results show a ductile behaviour of the concrete-steel hybrid beam both in partial and in full interaction. Finally, an analytical method has been adapted to determine the ultimate flexural capacity of this innovative beam considering the degree of connection. The last part of this work concerns the joint between the concrete-steel hybrid beam and a concrete-filled steel tubular column. The behaviour of this hybrid joint was verified by full-scale experimental tests. A finite element model has also been developed in order to investigate more deeply into the load transferring mechanism within the joint. This FE model is validated by comparing its results against experimental data. An analytical model for the design of the joint is then proposed.This new technology has already been used in actual projects during the thesis. The design procedure of the members and of the joints has been approved by the CSTB, the French certification organism of construction. First feedback for the on-site erection were good, and workers enjoyed the quick assembly and the increase of security on site
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Conti, Alfredo. "Tecniche della manifattura additiva - applicazioni in ambito aeronautico e aerospaziale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13306/.
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Il potenziale delle nuove tecnologie digitali applicate al settore industriale ha consentito di ridurre enormemente la durata dei cicli produttivi grazie alla rapida gestione di quantità di dati sempre più considerevoli attraverso l’introduzione delle Macchine a Controllo Numerico (Computer Numerical Control – CNC).
Nel corso delle ultime tre decadi, l’industria manifatturiera ha subito notevoli e sostanziali cambiamenti grazie ad una sempre più forte connessione con il mondo dell’informatica.
La più grande rivoluzione in tale ambito è stata segnata dall’avvento della Manifattura Additiva (Additive Manufacturing - AM), conosciuta sotto diversi nomi, tra i quali Prototipazione Rapida (Rapid Prototyping), Manifattura Rapida (Rapid Manufacturing) o Libera Fabbricazione di Forme (Free Form Fabrication).
Materia di ricerca e sviluppo sin dalla fine degli anni ’80, la Manifattura Additiva consente la creazione di elementi fisici tridimensionali partendo da modelli CAD attraverso la sovrapposizione successiva di materiale strato per strato (layer by layer), offrendo i benefici di una elevata flessibilità geometrica degli elaborati, altrimenti irraggiungibile attraverso le tradizionali tecniche di Manifattura Sottrattiva operanti per asportazione di materiale. In seguito ad intensive ricerche, progressi significativi sono stati fatti nello sviluppo e nella commercializzazione di nuovi ed innovativi processi AM.
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Walter, Catrina Ann. "Behavior of slender, precast L-shaped spandrel beams." 2008. http://www.lib.ncsu.edu/theses/available/etd-06092008-100425/unrestricted/etd.pdf.
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Wu, Zong-Hong, and 吳宗泓. "A Study on Springback Compensations of Forming Die for Composite L-Shape Beams." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9s65xq.
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碩士大葉大學
工業工程與管理學系
107
In this study, the heat-curing forming process parameters were simulated by L-Shape Beams curved thin-shell parts of carbon fiber composites and the die compensation research was carried out. The finite element analysis commercial software ANSYS was used for analysis and discussed separately. Thermal Springback, thermal warpage and heat shrinkage caused by temperature effects. According to the analysis results, the thermal curing of carbon fiber composites is deformed by the influence of material parameters and temperature parameters, and the cross-comparison of analytical data and experimenttal data is verified to show the mechanical properties, lamination angle, and bending of the material. The radius and temperature parameters will have a signifycant impact. The trend analysis of the research results can be applied to the design of the forming die, and can effectively reduce the number of experiments and research and development costs.
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Krishna, A. Vamsi. "Strengthening of Shear Deficient Reinforced Concrete L-Beams Using Glass Fibre Reinforced Polymer Composites." Thesis, 2016. http://ethesis.nitrkl.ac.in/9165/1/2016_MT_AVKrishna.pdf.
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Many of the existing reinforced concrete structures throughout the world undergoes deterioration due to many factors like corrosion, lack of detailing, increase in service loads which leads to cracking, loss of strength and stiffness due to ageing, excess deflections and improvement in design guidelines etc., necessitates the urgent need of rehabilitation. The rehabilitation which can be in the form of strengthening, repair or retrofitting. Reconstruction of the structures which requires more amount of cost, labour and takes more time, so rehabilitation is the better way of improving the structurally deficient existing RC structures. Fibre reinforced polymer composites are considered as smart and auspicious material for rehabilitation of existing reinforced concrete structures. Reinforced concrete L-beams which are found in buildings and bridges may fail either in flexure, shear, torsion or combination of any of them. Shear failure of RC L-beam is the most catastrophic failure as it does not give any prior warning before failure. Shear Strengthening of existing reinforced concrete L-beams using externally bonded fibre reinforced polymers has become a popular structural strengthening technique due to familiar benefits of FRP composites such as high strength to weight ratio and excellent corrosion and fatigue resistance and excellent durability.
The present research work assimilates the experimental and numerical investigation of structurally deficient reinforced concrete L-beams strengthened with Glass fibre reinforced polymer composites.
In the experimental study, a total of thirteen beams were tested under symmetrical four point static loading system. All the beams were tested in two series by varying shear span to effective depth ratio. In each series one beam was considered as control beam while other beams were strengthened with GFRP sheets/strips in different configurations and orientations. The various parameters were investigated such as amount and distribution of GFRP sheets, bonded surface number of layers of GFRP sheets/strips, fibre orientation and end anchorage. The experimental results shown that control beam failed in shear whereas failure of strengthened beams were initiated by debonding failure of GFRP sheets/strips followed by brittle shear failure. However, there was a better enhancement in the shear capacity of strengthened beams over control beams. An innovative method of new mechanical anchorage scheme comprised of steel plates with nut & bolt system was used for the prevention of debonding failure of GFRP sheets, as a result full strength of GFRP sheets gets utilized. A numerical investigation has also been carried out in ANSYS to validate the experimental findings.
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Grimsrud, Lars E. "Low-loss L-band fixed beam circular array." Thesis, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1467127.
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Chen, Jiabao. "Test Of Cracked Prestressed Concrete T-Beam Retrofitted For Shear Using CFRP L-Shaped Plates." Thesis, 2004. http://hdl.handle.net/10125/10414.
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Chimbombi, Ezekiel M. "Targeted Inactivation of Salmonella enterica Serovar Typhimurium in Fresh Cantaloupe Flesh (Cucumis melo L.) Using Electron Beam Irradiation." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7656.
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Food irradiation is costly in terms of the energy utilized and the time spent, therefore, it is imperative to optimize it in order to avoid sub lethal dose or an overdose both of which have detrimental effects on the quality of fresh produce such as cantaloupe. The bacterial load in fresh cut cantaloupe flesh was quantified on the basis of growth and mobility over time, and used as the basis for targeted irradiation simulation. The bacterial growth was predicted using the Gompertz model, while a power law function was used for predicting the bacterial mobility. The microbiological structure of cantaloupe flesh was assessed using Transmission Electron, Scanning Electron, and Light Microscopy as a basis for understanding the mobility of the bacteria into the internal mesocarp tissues. A plate assay was also undertaken to determine the possibility of S. typhimurium producing cell wall degrading enzymes such as polygalacturonase to gain access into intact fresh cantaloupe tissues.
S. typhimurium in fresh cut cantaloupe flesh has a lag phase duration of 7.76 hours and can reach a maximum population of 7.98 logs CFU/g in 30 hours. Cantaloupe flesh has a vast network of intracellular spaces through which the bacteria can move into the internal mesocarp tissues, particularly because S. typhimurium (LT2) does not produce any enzymes such as polygalacturonase which could be breaking down the cell wall binding structures as a mechanism for internalization into intact internal tissues. A theoretical bacterial inactivation dose estimate based on the experimentally determined D10-value and the bacterial population was used to simulate irradiation treatment of the cantaloupe flesh samples using a 10MeV electron beam irradiator (LINAC) to establish the best treatment. The optimal 10 MeV electron beam irradiation treatment for S. typhimurium internalized in fresh cut cantaloupe samples for 30 hours was determined to be a double beam with 0.5 cm attenuation of Lucite (Trademark) at the top and 3.3 cm at the bottom.
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CHANG, CHIIH-CHIANG, and 張志強. "A Double-L Beam Test for evaluatingthe Mixed Mode Fracture Toughnessof the Interface between FRP and Concrete─Experiment." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/3s8zr8.
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碩士逢甲大學
土木及水利工程所
91
In the analysis of the concrete structure which is strength by F.R.P. ,we usually assume that the F.R.P. is bonded well to the surface of concrete. In this condition, the F.R.P. acts very well. But, on the effect of environment and working quality, the F.R.P. did not bonded well enough to the surface of concrete, which leads the analysis does not precisely. Thus, the bonded strength of the interface between F.R.P. and concrete is not neglectable. In this study, we want to measure the Energy Release Rate (G) by the analysis of bond strength of the interface between F.R.P. and concrete, and the result of Peel test. Moreover, we can have the ratio of 、 by the peel angle and we can also have and . We use the Double L-beam test and the mixed mode test of John D. Barger to measure the critical peel force in order to prove the result of Peel test. Compare the Energy Release Rate (G) and 、 of Double L-beam test and Peel test, which are analysis by F.E.M..
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Liao, Yi-Sheng, and 廖益盛. "A Double-L Beam Test for evaluating the Mixed Mode Fracture Toughness of FRP and Concrete Interface－Numerical Analysis." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/36k694.
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碩士逢甲大學
土木及水利工程所
91
Abstract Peel test is an effective method to measure the bonding strength between different objects. The aim of this study is to make peel test be applied to Double-L beam test and find the relationship between the two tests. In Basic, the interfacial fracture energy of peel test is equal to the interfacial fracture energy of Double-L beam test with the same interface, therefore it is also hoped to predict the critical peel force of Double-L beam test while the specimens are peeled. In this study, peel test and Double-L beam test are analyzed by means of finite element method. The different factors considered in this study include the length of specimen and crack, the peel angle and the different load. Besides, this study also analyze literature【22】by means of T25. Numerical results analyzed by finite element method indicate that the change in interfacial fracture energy is not obvious under different specimen length condition. But the change in interfacial fracture energy is more obvious under other conditions. And about literature【22】, it can be obviously find that the analytical results calculated from T25 are more similar to the results from ABAQUS. But the results calculated from theoretical formula are much different with the results from ABAQUS.
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Wong, Peter Yan Yung. "The effects of electron beam irradiation and infusion of L-ascorbic acid on the preservation of quality of fresh ground beef patties." Thesis, 2001. http://hdl.handle.net/2429/11469.
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The objectives of this thesis were to assess the effectiveness of electron beam irradiation
(e ⁻ beam) at 5, 10 and 20 kGy in reducing bacterial count in fresh ground beef patties of 4, 17
and 30% fat and to evaluate the effects of infusing L-ascorbic acid (LAA) into beef carcasses on
the quality of irradiated fresh ground beef patties of 4, 17 and 30% fat.
Aqueous and emulsion model systems, exposed to ultraviolet and electron beam
irradiation, were first used to determine the catalytic activity of hemoglobin, the depletion of
LAA and the effects of LAA and e" beam on the degree of lipid oxidation. Hemoglobin
generated 50% less hydroxyl radicals than ferrous chloride in the Fenton reaction, indicating
minor catalytic activity. An increase in irradiation dosage and storage time drastically decreased
the concentration of lOmM L-ascorbic acid. Both ultraviolet and e" beam irradiation induced
lipid oxidation in a dose-dependent manner, which was further enhanced by the prooxidant
activity of 10 mM LAA. The 500 mM LAA exhibited the opposite effect.
The effectiveness of electron beam irradiation in controlling microbial growth was then
evaluated in ground beef patties made from LAA infused beef carcasses. Viable bacteria were
not detected in ground beef patties receiving irradiation at dosages of 5, 10 and 20 kGy. The
addition of tallow to increase total crude fat content in the beef patties led to an increase in
bacterial counts. An increase in pH of patties was could have been attributed to the metabolic
by-product generated by microorganisms.
Finally, the physicochemical characteristics of the infused ground beef patties were
evaluated. An increase in irradiation dosages resulted in an increase in lipid oxidation in the beef
patties. LAA also increased lipid oxidation, as well as, deoxymyoglobin oxidation in the beef
patties. Higher fat content resulted in higher lipid oxidation and pigment oxidation in the beef
patties. Hardness attribute of the ground beef patty was significantly increased by the addition of
fat. In general, the application of low dosage of e ⁻ beam to lean ground beef patties without the
addition of LAA is optimum in preserving quality.