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1
Reys, De Otiz Iclea. "Strut-and-tie modelling of reinforced concrete : short beams and beam-column joints." Thesis, University of Westminster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334612.
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Skibbe, Eric. "A comparison of design using strut-and-tie modeling and deep beam method for transfer girders in building structures." Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3907.
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Reshef, Aymeric. "Dual-rotation C-arm cone-beam tomographic acquisition and reconstruction frameworks for low-contrast detection in brain soft-tissue imaging." Electronic Thesis or Diss., Paris, ENST, 2018. http://www.theses.fr/2018ENST0044.
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L’arceau interventionnel est un système d’imagerie rayons X temps réel. Il dispose d’une option tomographique qui, grâce à une rotation de l’arceau autour du patient, permet d’acquérir des images en coupes dont la résolution en contraste est plus faible que celle des tomodensitomètres diagnostiques, rendant l’information clinique des tissus mous du cerveau inexploitable. Nous proposons un nouveau mode d’acquisition et de reconstruction tomographiques sur arceau interventionnel pour l’amélioration de la détection des faibles contrastes en imagerie interventionnelle des tissus mous de la tête. Afin d’émuler un filtre « bow-tie » (en nœud papillon), une double acquisition est envisagée. Les spécificités de la double acquisition imposent la conception d’un algorithme de reconstruction itérative dédié, incluant le filtre rampe dans l’énergie de minimisation. En bifurquant des approches par rétro-projection filtrée vers celles par filtration des rétro-projections, une méthode de reconstruction directe, alternative à la précédente, est proposée pour les acquisitions doubles. Pour une acquisition simple, la méthode est assurée de faire aussi bien que l’algorithme de rétro-projection filtrée quel que soit l’échantillonnage angulaire en géométrie planaire, et offre une approximation alternative à l’algorithme de Feldkamp-Davis-Kress en géométrie conique. Nous montrons qu’avec peu ou pas de modifications aux schémas précédents, les deux méthodes de reconstruction (itérative et directe) s’adaptent bien à la reconstruction de régions d’intérêt, à laquelle l’acquisition double reste étroitement liée à travers son acquisition tronquée<br>Interventional C-arm systems are real-time X-ray imaging systems, that can perform tomographic acquisitions by rotating the C-arm around the patient ; however, C-arm cone-beam computed tomography (CBCT) achieves a lower contrast resolution than diagnostic CT, which is necessary in order to benefit from the clinical information of soft tissues in the brain. We propose a new C-arm CBCT acquisition and reconstruction framework to increase low-contrast detection in brain soft-tissue imaging. In order to emulate a bow-tie filter, a dualrotation acquisition is proposed. To account for all the specificities of the dual-rotation acquisition, a dedicated iterative reconstruction algorithm is designed, that includes the ramp filter in the cost function. By switching from filtered backprojection (FBP) to backprojection-filtration (BPF) reconstruction methods, we propose an alternative, direct reconstruction method for dual-rotation acquisitions. For single-rotation acquisitions, the method ensures to perform as good as FBP with arbitrarily coarse angular sampling in planar geometries, and provides a different approximation from the Feldkamp-Davis-Kress (FDK) algorithm in the cone-beam geometry. Although we used it to emulate a virtual bow-tie, our dual-rotation acquisition framework is intrinsically related to region-of-interest (ROI) imaging through the truncated acquisition. With few or no modification of the proposed reconstruction methods, we successfully addressed the problem of ROI imaging in the context of dual-rotation acquisitions
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Santos, Daniel dos. "Análise de vigas de concreto armado utilizando modelos de bielas e tirantes." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-22062006-102606/.
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O modelo de bielas e tirantes apresenta como uma de suas vantagens a generalidade, ou seja, é capaz de representar, de modo aproximado, porém realista e sistemático, grande parte dos elementos de concreto estrutural da atualidade. Além disso, permite ao engenheiro fácil visualização físico-intuitiva do comportamento do concreto estrutural. Por outro lado, o modelo ainda tem um enorme potencial não aproveitado. Ainda não se tem um critério exato para determinação dos nós e das seções transversais das bielas de alguns elementos. Apesar de haver certas incertezas no caso de vigas-parede e principalmente de blocos de fundação, nas vigas esses elementos do modelo podem ser determinados sem grandes dificuldades. Possivelmente, a solução seria variar as dimensões das bielas e as posições dos nós, ambas hipotéticas, a fim de confrontar várias situações com resultados experimentais. Daí a grande importância da difusão do modelo de bielas e tirantes: um maior número de análises de modelagens e de resultados de ensaios levará a um maior domínio sobre o modelo. Este trabalho consiste na análise de vigas de concreto armado utilizando modelos de bielas e tirantes. São apresentados os conceitos que levaram à concepção do modelo, desde a Analogia Clássica da Treliça, chegando aos critérios para verificação dos elementos da treliça e às recomendações atuais de normas e pesquisadores. Com o auxílio do programa computacional CAST (2000), foram modeladas quatro vigas, sendo as três primeiras biapoiadas sem descontinuidades e a quarta com balanço e descontinuidade geométrica (abertura na alma). A primeira viga biapoiada teve algumas de suas características iniciais alteradas a fim de gerar o segundo e o terceiro modelos, procurando-se estabelecer limites de carregamentos e análises comparativas. Os resultados das modelagens permitiram comparações com os resultados das verificações realizadas segundo os critérios da NBR 6118:2003 e do MC CEB-FIP (1990) e, permitiram também, identificar os aspectos de maior dificuldade na concepção de um modelo de bielas e tirantes e os pontos críticos dos mesmos, nos quais há maior possibilidade de falha nas verificações<br>One of the main advantages presented by the strut-and-tie model is generality. This model is able to approximately represent, in a realistic and systematic way, the majority of todays reinforced concrete elements. Furthermore, it allows the physics-intuitive visualization of the behavior presented by structural concrete. On the other hand, its potentials are not fully explored yet. Up to date, there is no accurate criterion for the determination of nodes and transverse sections of some strut elements. Despite presenting some uncertainties related to the determination of wall-beams (and mainly of foundation blocks), the model can determine beams without major difficulties. Probably, the key is to vary the dimensions of the struts and the positions of the nodes, both hypothetical, in order to confront various situations with experimental data. Hence, it is very important to diffuse the strut-and-tie model: the bigger the number of modeling analysis and experimental data, the better the comprehension of the model. This work aims to analyze reinforced concrete beams employing the strut-and-tie model. Here are presented the concepts that led to the development of the model, ranging from the Truss Classic Analogy to the criteria employed to verify truss elements and the recommendations from researchers and established standards (rules or norms). Four examples of beams were modeled. Three of them were double-based and the fourth presented balance and no geometric discontinuity (with an opening). Some of the characteristics of the first double-based beam were altered in order to generate the second and the third model, thus establishing loading limits and comparative analysis. The modeling allowed comparisons between the verifications performed in accordance with the NBR 6118:2003 and MC CEB-FIP criteria. It also allowed the identification of major difficulties and critical aspects related to the development of struts and ties, the ones that are most prone to failure in the verification process
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Růžičková, Markéta. "Ocelová konstrukce hangáru." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226908.
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The purpose of this dissertation is to take into consideration the design and the steel structure assessment of the hangar for small propeller aircraft type Cessna. The platform dimensions are 40,0 by 60,0 metres. Headroom is around 10,0 metres. The object’s location is in Brno. The main structural material is steel S355J2. There are two initial geometric alternatives, in other words structural modifications of desired solution. These are spatial truss arc tie beam and garland tie beam. The two alternatives were tentatively designed according to their dimensions and the main supporting elements of both alternatives were also assessed and considered. The alternatives were finally evaluated and one option was selected for detailed processing. In turn of the chosen option, there had been drawing of detailed analysis of the main load bearing parts of the construction with joints and some other details included. Furthermore there is drawing documentation and supervisor’s technical report attached. The valid standards CSN EN were used in processing of this dissertation.
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Kudrna, Jiří. "Nosná železobetonová konstrukce víceúčelového objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265738.
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This work deals with the structural solution of reinforced concrete floor slab, deep beam and its support of multipurpose building. The structure is designed and assessed in according to valid standards. The continuous one-way slab is analyzed by Finite Element Method, deep beam is solved by Strut-and-Tie model.
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Tanno, Danieli Colombo dos Santos. "Blocos de concreto sobre estacas posicionados nas divisas de terrenos: estudo analítico e análise numérica linear." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03072012-101640/.
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Este trabalho estuda o comportamento estrutural de blocos sobre estacas em concreto armado situados em divisas de terrenos. Foi feita revisão bibliográfica abordando os assuntos de blocos de coroamento, vigas de equilíbrio, modelo de bielas e tirantes e um breve comentário sobre o programa computacional Diana (2010). O trabalho apresenta um roteiro para análise estrutural e dimensionamento de vigas de equilíbrio sobre estacas com pilar excêntrico ao apoio. É apresentado um exemplo feito por Andrade (1989), comparado com o método proposto por Burke (1979) e com análise numérica. Além deste, foram analisados casos de projetos reais utilizando o método Burke (1979) adaptado neste trabalho. Alguns desses exemplos foram modelados em regime elástico e linear no programa computacional Diana (2010). São apresentadas comparações de resultados obtidos com o método Burke (1979) e análise numérica, comprovando a eficácia desse método. Em todos os exemplos estudados o método proposto por Burke (1979) indicou bons resultados quando comparados com os encontrados em análise computacional. A dissertação apresenta soluções para projetos de bloco sobre estacas, situados em divisas de terrenos e associados a vigas de equilíbrio.<br>This research investigates the structural behavior of reinforced concrete blocks piles located on the limit of land. Literature review was done about blocks piles, balance beams, strut and tie model and a short comment about the Diana computer program (2010). The dissertation presents a roadmap for structural analysis and sizing of balance beams on stakes with eccentric support pillar. An example, which was studied by Andrade (1989), is compared with the same example done using the method proposed by Burke (1979) and with numerical analysis. In addition to this, are analyzed real cases of projects using the method of Burke (1979). Some of these examples were modeled in linear and elastic characteristics using Diana program computer (2010). Here, it is presented comparisons between the method proposed by Burke (1979) and numerical analysis. It is presented comparisons between the method Burke (1979) and numerical analysis, proving the effectiveness of this method. In all examples studied the method proposed by Burke (1979) provided with good accuracy the results for computer analysis. The conclusion presents suggestions for projects of block piles located in limit of land associated with balance beams.
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Roček, Tomáš. "Nosná železobetonová konstrukce bytového domu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371956.
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This work deals with the structural solution of selected parts of load bearing structure of apartment house - floor slabs of 1.PP and 2.NP, deep beam and its supporting column. The analysis is made by Finite Element Method, deep beam is solved by Strut-and-Tie model. The elements are designed and assessed according to valid standards.
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Torre-Casanova, Anaëlle. "Prise en compte de la liaison acier-béton pour le calcul de structures industrielles." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00777204.
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Les structures en béton armé sont amenées à répondre à différentes exigences pouvant dépasser la simple résistance mécanique. Pendant le processus de fissuration, les contraintes dans le béton armé sont progressivement redistribuées entre l'acier et le béton via l'interface entre ces deux matériaux. Cette redistribution de contraintes a un impact direct sur l'état de fissuration final et doit donc être prise en compte dans la modélisation. Il existe différents modèles numériques capables de représenter les effets de la liaison acier-béton. Cependant, leur usage est, pour l'instant, incompatible avec les applications concernant les structures de grandes dimensions (difficultés de maillage, coût de calcul...). Dans ce cadre d'application, l'hypothèse de liaison parfaite entre l'acier et le béton (déplacement identique) est donc toujours utilisée. On se propose ici de développer un nouveau modèle éléments finis de liaison acier-béton qui soit à la fois représentatif des phénomènes physiques se produisant à l'interface entre les deux matériaux et compatible avec les contraintes de modélisation des structures de grandes dimensions. Ce travail de thèse se découpe en trois grandes parties : - le développement d'un modèle élément fini de liaison acier-béton adapté aux contraintes de modélisation des structures de grandes dimensions. Ce modèle numérique permet ainsi de tenir compte des interactions mécaniques entre le béton et les armatures d'acier représentées à l'aide d'éléments barres. - la caractérisation du comportement de la liaison acier-béton. Un modèle de loi d'adhérence (évolution de la contrainte d'adhérence en fonction du glissement) basé sur des observations expérimentales (campagne expérimentale de pull-out menée au cours de la thèse et données bibliographiques) est proposé. Il permet en particulier de différencier le cas d'une rupture par arrachement, d'une rupture par éclatement en tenant compte des caractéristiques matériaux et géométriques de la structure. - l'application du modèle proposé à un élément structurel (poutre). Un essai de poutre en flexion quatre points visant à caractériser l'évolution de la fissuration (évolution de l'ouverture de fissure mesurée à l'aide de la technique de corrélation d'images notamment) a ainsi été proposé. Ces résultats ont ensuite été comparés à ceux de simulations numériques tenant compte de la liaison acier-béton d'une part ou de l'hypothèse de liaison parfaite d'autre part. Les deux modélisations donnent une bonne approximation du comportement extérieur de la structure (comportement global et ouvertures de fissure des surfaces extérieures de la poutre). Le modèle de liaison acier-béton apporte cependant une meilleure caractérisation de la phase de fissuration active (apparition des fissures) et modifie plus particulièrement le comportement local de la structure à proximité directe des armatures (limitant le développement de l'endommagement du béton le long des renforts).
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Barros, Rodrigo. "Análise de blocos de concreto armado sobre duas estacas com cálice totalmente embutido mediante presença de viga de travamento." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14072009-170225/.
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Esta pesquisa estuda o comportamento de blocos de concreto armado sobre duas estacas com cálice totalmente embutido, utilizado na ligação pilar-fundação de estruturas de concreto pré-moldado. Particularmente, foi avaliado o efeito que a viga de travamento provoca no bloco quando apoiada nas paredes laterais do cálice. Foi desenvolvida análise numérica tridimensional utilizando programa baseado no método dos elementos finitos (MEF), na qual foi considerada a não-linearidade física dos materiais. Para avaliação do programa adotado, realizou-se análise comparativa de resultados experimentais e numéricos obtidos por meio de outro programa. Nos blocos estudados variou-se a espessura e o tipo de conformação das paredes do cálice, o ângulo de inclinação da biela e a intensidade das ações na viga de travamento. Os resultados indicam que a presença da viga de travamento não altera de modo significativo o comportamento do bloco, e que a parede do cálice é capaz de transferir a força proveniente da viga em direção às estacas de modo eficaz. Por meio das tensões nas barras da armadura principal, foi possível obter a força no tirante e o ângulo de inclinação da biela antes da ruína dos modelos. Constatou-se que os ângulos apresentaram maior inclinação do que as utilizadas no dimensionamento, que por sua vez foi feito baseado nos modelos de bielas e tirantes.<br>The present research studies the behavior of two pile caps reinforced concrete with embedded socked used in connections of pre-cast concrete structures. It was particularly evaluated the effect provoked by the locking beam on the pile-caps when supported by the socket lateral walls. Three-dimensional numerical analyses using software based on finite element method (FEM) were developed considering the nonlinear physical behavior of the material. To evaluate the adopted software, a comparative analysis was made using numerical and experimental results obtained from other software. In the pile caps studied, it was noticed a variation in the wall thickness, socket interface, strut angle inclination and action on beam. The results show that the presence of beam does not change significantly the pile caps behavior and that the socket wall is able to transfer effectively the force from the beam to the pile caps. By the tensions on the bars of longitudinal reinforcement, it was possible to obtain the force on the tie and the strut angle inclination before the collapse of models. It was found that the angles present more inclinations than those used in the design, which was made based on strut and tie model.
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Ruček, Martin. "Nosná ocelová konstrukce administrativní budovy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227323.
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Main concern of the thesis is a structural design of main load bearing elements of steel, four-storey high administration building. Designed building has 36 m long and 24 m wide rectangular footprint. Roof is shaped into a hyperbolic paraboloid surface. Main load bearing structure is consisting of six main cross sections formed by truss columns, and generally curved roof truss beams, accompanied by storey supporting frames with composite slabs. Overall shape of the roof is defined by warped surface. Cladding of the building is consisting of aluminium facade system.
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MATSUDA, HYLTON. "Monitoracao do feixe externo do ciclotron cyclone 30 do IPEN-CNEN/SP." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10995.
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07535.pdf: 5658873 bytes, checksum: bfc9a035eb51ae184a489a4570c8c827 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Linfield, Edmund Harold. "The uses of ion beams with molecular beam epitaxial growth." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386165.
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Hulland, Meg. "Pultruded GFRP beams : an evaluation of the Expanded Web Beam concept." Thesis, Lancaster University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551628.
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This thesis presents the work completed on the evaluation of the expanded web beam concept. The research focussed on investigating methods for expanding the web of a standard pultruded GFRP I-beam to achieve improved mechanical performance whilst achieving an overall saving on mass. The 14 (102 x 102 x 6.4mm) beam was chosen as the standard beam from which the beams were constructed and the mechanical performance of the larger 18 (203 x 203 x 9.5mm) beam as the target for the modified beams. Three designs were proposed and two full-scale beams were built and tested. Of the three designs proposed, one used Quickstep manufactured sandwich panels and another metal connectors fabricated by a Selective Laser Melting facility. All the designs were analysed using theoretical closed form solutions and ANSYS FE software. A tension coupon testing programme was carried out in support of these analyses. The two full-scale beams were tested, together with an 18 beam, in three-point bending and lateral-torsional buckling. The slender nature of the expanded web beams meant that lateral bracing was required for the lateral buckling testing. Of the two modified beams the one that performed the best achieved, 85% of the deflection limit load and 71% of the lateral- torsional buckling load of the 18 beam for an overall mass saving of 38%.
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Ruggerini, Andrea Walter <1988>. "Geometrically nonlinear analysis of thin-walled beams based on the Generalized Beam Theory." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8497/7/Geometrically-nonlinear-GBT-beam-AndreaW-Ruggerini.pdf.
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The thesis addresses the geometrically nonlinear analysis of thin-walled beams by the Generalized Beam Theory ( GBT ). Starting from the recent literature, the linear theory is illustrated, along with some issues related to GBT finite element formulation. Potential benefits of using
the GBT in design are exemplified with reference to the design of roofing systems. To assess the deterioration of member capacity due to cross-section distortion phenomena, the formulation of a geometrically nonlinear GBT is then pursued. The generalization of the GBT to the nonlinear context is performed by using the Implicit Corotational Method ( ICM ), devising a strategy to effectively apply the ICM when considering higher order deformation modes. Once, obtained, the nonlinear model has been implemented using a state-of-the-art mixed-stress finite element. The nonlinear finite element is then implemented starting from the linear GBT one. Extensive numerical results show the performance of the proposed approach in buckling and path-following analyses.
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Gutierrez, Sanchez Alejandro Rafael <1985>. "Modelling and analysis of thin-walled beams in the context of the Generalized Beam Theory." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6629/1/Gutierrez_Alejandro_tesi.pdf.
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In this work, the Generalized Beam Theory (GBT) is used as the main tool to analyze the mechanics of thin-walled beams. After an introduction to the subject and a quick review of some of the most well-known approaches to describe the behaviour of thin-walled beams, a novel formulation of the GBT is presented. This formulation contains the classic shear-deformable GBT available in the literature and contributes an additional description of cross-section warping that is variable along the wall thickness besides along the wall midline. Shear deformation is introduced in such a way that the classical shear strain components of the Timoshenko beam theory are recovered exactly. According to the new kinematics proposed, a reviewed form of the cross-section analysis procedure is devised, based on a unique modal decomposition. Later, a procedure for a posteriori reconstruction of all the three-dimensional stress components in the finite element analysis of thin-walled beams using the GBT is presented. The reconstruction is simple and based on the use of three-dimensional equilibrium equations and of the RCP procedure. Finally, once the stress reconstruction procedure is presented, a study of several existing issues on the constitutive relations in the GBT is carried out. Specifically, a constitutive law based on mirroring the kinematic constraints of the GBT model into a specific stress field assumption is proposed. It is shown that this method is equally valid for isotropic and orthotropic beams and coincides with the conventional GBT approach available in the literature. Later on, an analogous procedure is presented for the case of laminated beams. Lastly, as a way to improve an inherently poor description of shear deformability in the GBT, the introduction of shear correction factors is proposed. Throughout this work, numerous examples are provided to determine the validity of all the proposed contributions to the field.
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Gutierrez, Sanchez Alejandro Rafael <1985>. "Modelling and analysis of thin-walled beams in the context of the Generalized Beam Theory." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6629/.
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In this work, the Generalized Beam Theory (GBT) is used as the main tool to analyze the mechanics of thin-walled beams. After an introduction to the subject and a quick review of some of the most well-known approaches to describe the behaviour of thin-walled beams, a novel formulation of the GBT is presented. This formulation contains the classic shear-deformable GBT available in the literature and contributes an additional description of cross-section warping that is variable along the wall thickness besides along the wall midline. Shear deformation is introduced in such a way that the classical shear strain components of the Timoshenko beam theory are recovered exactly. According to the new kinematics proposed, a reviewed form of the cross-section analysis procedure is devised, based on a unique modal decomposition. Later, a procedure for a posteriori reconstruction of all the three-dimensional stress components in the finite element analysis of thin-walled beams using the GBT is presented. The reconstruction is simple and based on the use of three-dimensional equilibrium equations and of the RCP procedure. Finally, once the stress reconstruction procedure is presented, a study of several existing issues on the constitutive relations in the GBT is carried out. Specifically, a constitutive law based on mirroring the kinematic constraints of the GBT model into a specific stress field assumption is proposed. It is shown that this method is equally valid for isotropic and orthotropic beams and coincides with the conventional GBT approach available in the literature. Later on, an analogous procedure is presented for the case of laminated beams. Lastly, as a way to improve an inherently poor description of shear deformability in the GBT, the introduction of shear correction factors is proposed. Throughout this work, numerous examples are provided to determine the validity of all the proposed contributions to the field.
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Kubášková, Barbora. "Horský hotel v Beskydech." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226642.
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This thesis solves design of timber structure of mountain hotel in Beskydy. The hotel is two-storey building with residential attic and no cellar. The ground plan of the building is about 15x26 m and height of the building is 14,76 m. The type of roof timbers was chosen from two options. There was used structural timber of the strength class C24, glued laminated timber of the strength class GL24 and steel S235. Program Scia Engineer was used for the static analysis of the structure. There was made only linear calculation.
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Dissanayake, Udaya Indrajith. "The influence of the composite beam-to-steel column joint on the behaviour of composite beams in frames." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389752.
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Silva, Hugo Bonetti Santos. "Análise numérica da influência da excentricidade na ligação placa-viga em pavimentos usuais de edifícios." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14012011-105857/.
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Na análise de estruturas é comum a consideração da concentricidade entre vigas e placas. Estudos numéricos em pavimentos de laje nervurada, onde os espaçamentos das vigas são pequenos, mostram que a consideração da excentricidade entre placa e a viga resultam em redução dos deslocamentos na estrutura, entretanto não existem estudos sobre a influência da excentricidade em pavimentos com poucas vigas. Este trabalho apresenta a análise numérica de pavimentos com dimensões usuais considerando ou não a excentricidade com o objetivo de verificar a influência da excentricidade no comportamento da estrutura. As análises mostraram diferenças de deslocamentos e tensões nas estruturas estudadas. O efeito de excentricidade pode ser incluído através da modificação da matriz de rigidez do elemento finito de viga. Todos os pavimentos foram analisados com o software ANSYS com elementos de placa e viga que representassem os modelos do trabalho.<br>It\'s usual practice on structural analysis of buildings slabs to assume the concentricity between plates and beams. Numerical studies in waffle-slabs, where the distance between beams is small, showed that the eccentricity of beam to plate results in reduction of stresses and displacements of the system, however there is not similar study about the influence of eccentricity in slabs with few beams. This work presents numerical analysis results of at slabs with usual dimensions considering or not plate-beam eccentricity, aiming at evaluating its influence in structural behavior. The analysis showed differences of displacements and stress in studied structures. The effects of eccentricity can be included by modifying the stiffness matrix of the beam finite element. All slabs were analyzed with ANSYS program with suitable beam and plate elements.
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FORTNEY, PATRICK JOSEPH. "THE NEXT GENERATION OF COUPLING BEAMS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115837131.
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Densham, Christopher John. "Design and development of a tantalum foil target for the production of high intensity radioactive beams." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365727.
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Crouch, Matthew. "Luminosity performance limitations due to the beam-beam interaction in the Large Hadron Collider." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/luminosity-performance-limitations-due-to-the-beambeam-interaction-in-the-large-hadron-collider(287b2265-a67d-406a-8c94-0fc193e2401b).html.
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In the Large Hadron Collider (LHC), particle physics events are created by colliding high energy proton beams at a number of interaction points around the ring. One of the main performance indicating parameters of the LHC is the luminosity. The luminosity is limited by, amongst other things, the strength of the beam-beam interaction. In this thesis, the effect of the beam-beam interaction on the luminosity performance of the LHC and the proposed High Luminosity Large Hadron Collider (HL-LHC) is investigated. Results from a number of dedicated, long-range beam-beam machine studies are presented and analysed. In these studies, the minimum beam-beam separation for two different beta star optics are identified. This separation defines the minimum operational crossing angle in the LHC. The data from these studies are then compared to simulation of the dynamic aperture and the results are discussed. In addition to studies of the LHC, an analytical approach is derived in order to describe the hourglass effect, which may become a contributing factor in limiting the luminosity performance of the HL-LHC.
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Parodi, Katia. "On the feasibility of dose quantification with in-beam PET data in radiotherapy with 12C and proton beams." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28788.
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This thesis has contributed to the achievement of in-beam PET as a promising clinical monitoring technique. In response to a pressing medical demand, this work has provided a tool for quantification of local dose deviations in case of observed discrepancies between the measured and expected PET images. The implemented interactive approach described in chapter 3 is in clinical use since 2001. It provides the radio-oncologist with a valuable feedback which may allow a prompt reaction in the strategy of the therapy prior to the delivery of the successive treatment fraction in case of significant deviations between planned and actually applied dose. ...
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Parodi, Katia. "On the feasibility of dose quantification with in-beam PET data in radiotherapy with 12C and proton beams." Rossendorf : Forschungszentrum, 2004. http://www.fz-rossendorf.de/publications/006865/6865.pdf.
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Ho, Jimmy Cheng-Chung. "Modeling spanwise nonuniformity in the cross-sectional analysis of composite beams." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29638.
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Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Hodges, Dewey; Committee Member: Bauchau, Olivier; Committee Member: Volovoi, Vitali; Committee Member: White, Donald; Committee Member: Yu, Wenbin. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Quintana, James R. A. "Frequency Responsive Beam Tracing." Oberlin College Honors Theses / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1462957979.
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Redgrave, Giles David. "Spin spectroscopy of YbF using molecular beam interferometry." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285125.
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Block, Robert E. (Robert Edward). "Electron beam dynamics for the ISIS bremsstrahlung beam generation system." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/76521.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 177-179).<br>An electron beam transport system was designed for use in the Bremsstrahlung Beam Generation System of the Integrated Stand-off Inspection System (ISIS). The purpose of this electron transport system was to provide for electron beam diagnostics and energy selection while also positioning the electron beam on a target down range. The transport system and its component magnets were designed using the TRANSPORT, Poisson, and Opera 3D codes, as well as several custom Python scripts. By implementing several methods in each part of the design process, it was possible to design the electron transport system to the exact specifications of the ISIS electron beam. This careful and iterative design process was documented in such a way to facilitate future beam transport design both at the MIT Plasma Science and Fusion center and elsewhere. This design process resulted in a beam transport system composed of three irondominated resistive-coil electromagnets. The system was designed for beam momentum up to 60 MeV/c and emittance of order 20 mm-mrad. Through magnetic field simulation and beam transport in 3D, a ID matrix code which tracks individual particles was developed. This code agreed with more detailed beam calculations and should allow for rapid beam simulation during system testing and operation.<br>by Robert E. Block.<br>S.M.
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Bellan, Luca. "Beam Dynamics Characterization of the IFMIF/EVEDA RFQ Input Beam." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3425290.
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The high intensity accelerators are one of the world-wide leading edge research in the beam dynamics studies. The upgrades of the existing accelerator LINAC4, FERMILAB, FAIR and the new applications on the neutron technologies such as ESS, IFMIF, MUNES, both for science research, medical treatment and material testing require an increase knowledge in the high intensity beams treatment. One of the most difficult part to be treated and which represent the first obstacle in increasing the beam intensity in the accelerators, is the injector part: the large number of charge particles at low energy forms a strongly interacting system, subjected to the Coulombian interaction. The situation further complicates due to the presence of different species which produces a plasma-like behavior of the beam. On the behalf of the INFN-LNL team, I participated to the commissioning of the high intensity injector (source and low energy transfer line) of the IFMIF/EVEDA project. Via experiments and simulation model developments I contributed to the study of the beam behavior in this specific framework. In particular I upgrade the emittance measurement routine in order to manage correctly the artifacts; I develop and benchmark with measurements self-consistent simulation models of the LEBT and extraction transfer line, which includes the secondary
electron from residual gas and from metal due to collisions; I design a modification of medium and high energy line in order to test the CW steady state of the longest radio frequency quadrupole in the world, an in-kind contribution of INFN. All the development routines and experience will give important contributions for the next high intensity facilities. The first
chapter presents the motivation of the IFMIF project and the main characteristics required by the accelerator. The main challenges of such accelerator are also listed. The second chapter introduces the main concepts of the beam dynamics of space-charge which will be used in
the thesis. The third chapter presents the IFMIF/EVEDA project, with a description of the main elements; particular focus is made onto the source, the low energy beam transfer line and on the radio frequency quadrupole. Scaling law derivation for the extracted beam with contaminants is shown. The commissioning phases are introduced, each with its specific
challenges. The fourth chapter presents the modification of the emittance analysis routine which can manage the ghost infested signal of the IFMIF/EVEDA emittancemeter. The fifth and the sixth chapters contains the simulation models developed to estimate the space-charge
beam behavior under neutralization regime: the model with constant neutralization and the one with the full secondary plasma evolution are presented and benchmarked with the measurements. In the fifth chapter the measurements refers to 60−55 mA proton beam at 50 keV, while for the sixth chapter the beam considered is composed of 140−135 mA deuteron beam at 100 keV. In these chapters, the variation of the radio frequency quadrupole beam input characteristics with respect to the electromagnetic plasma confinement of the low energy transfer line is studied. The original contribution in these simulations is given by the emitted secondary electron from metal, which as some effects on the space charge compensation process, on the emittance value. Deep study of the multispecies distributions and behavior was performed. The four chapter defines, for the experimental proton point considered, the
solenoid variations where searching the maximum radio frequency quadrupole transmission. The output beam behavior of this one is studied in commissioning perspective. In thesixth chapter, after testing the radio frequency quadrupole transmission with the secondary plasma model (also said dynamic neutralization model) with a realistic beam distribution, the
simulations of the extraction system are presented. The benchmark with the measurements are also performed. The seventh chapter presents the design of the modification of the medium and high energy transfer sections of the accelerator in order to allow the test of the CW of the radio frequency quadrupole, bypassing the superconductive cavities. Extensive
simulations of the system robustness to the errors are explored. The last chapter reports the conclusions.<br>Gli acceleratori ad alta intensità sono oggetto di ricerche all'avanguardia a livello mondiale nel campo degli studi di dinamica di fascio. Gli upgrade degli acceleratori esistenti LINAC4, FERMILAB, FAIR e le nuove applicazioni che utilizzano fasci di neutroni come ESS, IFMIF, MUNES, sia per la ricerca scientifica sia per cure mediche che per le prove sui materiali, richiedono un aumento delle conoscenze nella trattazione dei fasci ad alta intensità. Una delle parti più difficili da trattare è la parte dell'iniettore: le particelle dei fasci ad alta intensità a bassa energia sono sottoposte ad una forte interazione coulombiana. La situazione si complica ulteriormente a causa della possible presenza di diverse specie, le quali producono un comportamento plasma-like del fascio. Per conto del team INFN-LNL, ho partecipato al collaudo dell'iniettore (sorgente e linea di trasferimento a bassa energia) del progetto IFMIF / EVEDA. Tramite esperimenti e sviluppi del modello di simulazione, ho contribuito allo studio del comportamento del fascio in questo quadro specifico. In particolare, ho migliorato la routine di misura di emittenza al fine di gestire correttamente gli artefatti generati dai fasci ad alta intensità; ho sviluppato e confrontato con misure di fascio i modelli auto-consistenti di simulazione della linea di trasferimento e dell'estrazione, includendo gli elettroni secondari generati (a causa di interazioni con il fascio) sia dal gas residuo che dal metallo; ho studiato una modifica della line a media ed alta energia, in modo tale da testare il regime CW del quadrupolo a radio-frequenza (il più lungo al mondo), contributo al progetto dell'INFN. Tutti gli studi che ho effettuato e l'esperienza acquisita rappresentano un contributo importante per le prossime facility ad alta intensità. Il primo capitolo presenta la motivazione del progetto IFMIF e le principali caratteristiche richieste dall'acceleratore. Sono elencate anche le principali sfide di tale acceleratore. Il secondo capitolo introduce i concetti principali della dinamica di fascio in regime di space-charge. Il terzo capitolo presenta il progetto IFMIF/EVEDA, con una descrizione degli elementi principali dell'acceleratore; particolare attenzione è rivolta alla sorgente, la linea di trasferimento del fascio di bassa energia e del quadrupolo a radiofrequenza. La derivazione di una fromula teorica per scalare l'ottica del fascio estratto, in presenza di contaminati, viene presentata e succesivamente validata. Vengono introdotte le fasi del collaudo, ognuna con le sue specifiche sfide. Il quarto capitolo presenta la modifica ed implementazione della routine di analisi delle emittanze, la quale può gestire il segnale ottenuto con presenza di artefatti. Il quinto ed il sesto capitolo contengono i modelli di simulazione sviluppati per stimare la carica spaziale ed il comportamento del fascio in regime di neutralizzazione di space-charge: il modello con neutralizzazione costante e quello con l'evoluzione del plasma secondario vengono presentati e confrontati con le misure. Nel quinto capitolo, le misure di riferimento riguardano un fascio protonico di 60-55 mA a 50 keV, mentre nel sesto capitolo il fascio considerato è composto da deutoni di 140-135 mA a 100 keV. In questi capitoli è studiata la variazione del comportamento del fascio all'input dell'RFQ, rispetto al confinamento elettromagnetico del plasma nella linea di trasferimento a bassa energia di trasferimento. Il contributo originale in queste simulazioni è dato dall'inclusione dell'effetto degli elettroni secondari emessi dal metallo, il quale agisce direttamente sulla compensazione della carica spaziale. Viene inoltre presentato uno studio approfondito delle distribuzioni e dei comportamenti delle diverse specie presenti nella line durante il processo di neutralizzazione. Il capitolo quattro definisce, per il fascio protonico sperimentale considerato, le variazioni dei solenoidi per ottenere la massima trasmissione attraverso l'RFQ. Il comportamento del fascio in uscita dall'RFQ è stato anche esso studiato. Nel sesto capitolo, dopo aver testato la trasmissione dell'RFQ con la distribuzione di fascio ottenuta dal modello di neutralizzazione dinamica,
vengono presentate le simulazioni del sistema di estrazione. Il settimo capitolo presenta il design della modifica delle line di trasferimento a media e alta energia dell'acceleratore, in modo tale da consentire il test del regime CW RFQ. I risultati di estese simulazioni Montecarlo, ottenute per stimare la robustezza del design rispetto agli errori meccanici e magnetici, sono inoltre incluse. L'ultimo capitolo riporta le conclusioni.
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Ho, Qhinhon D. "An Assessment Of The Accuracy Of The Euler-Bernoulli Beam Theory For Calculating Strain and Deflection in Composite Sandwich Beams." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2084.
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This study focuses on assessing the accuracy of the Euler-Bernoulli beam theory as computational bases to calculate strain and deflection of composite sandwich beam subjected to three-point and four-point bending. Two groups of composite sandwich beams tests results will be used for comparison purposes. Mechanical properties for the laminated skin are provided by researchers from University of Mississippi (Ellen Lackey et al., 2000). Mechanical properties for the balsa wood core are provided by Alcan Baltek Corporation. Appropriate material properties and test geometries are then used in the Euler-Bernoulli-based algorithm in order to generate analytical data for comparison to experimental data provided by researchers from University of New Orleans (UNO, 2005). The resulting single material cross section is then analyzed in the traditional manner using the Euler-Bernoulli beam theory. In general, the Euler-Bernoulli beam theory provides an appropriate analytical approach in predicting flexural behavior of composite sandwich beams.
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MARSICANO, LUCA. "The Beam-Dump eXperiment." Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1001409.
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Hadronic matter makes about 14% of the known universe. The remaining 86% is Dark Matter (DM). Since it does not interact with the ordinary matter via electromagnetic force, DM is not visible and, to date, it escaped detection. The search for DM is one of the hottest topic in modern physics. Despite
the increasing number of astrophysical and cosmological observations proving the existence, so far no particle physics experiment has detected DM yet. In a popular class of models, DM is composed of particles with mass in the MeV-GeV range, interacting with the Standard Model via a new force, mediated by a massive vector boson, the Dark Photon or A'.
BDX (Beam Dump eXperiment) is an approved experiment searching for DM in the Dark Photon theoretical scenario. The experiment makes use of CEBAF (Continuous Electron Beam Accelerator Facility) 11 GeV electron beam impinging on the Jefferson Lab (Jlab) Hall-A beam-dump. The interaction of the energetic electrons in the beam-dump may lead to the production of Dark Photons through a bremsstrahlung-like radiative process. Subsequently, the A's decay to DM particle-antiparticle pairs, which travel almost unaltered through the length of the dump. A ~ 1 cubic meter detector made of CsI(Tl) (Thallium doped Cesium Iodide) crystals is located in the trajectory of the DM beam, 20 m downstream of the beam-dump. A fraction of the DM particles scatter off atomic electrons in the detector giving rise to a detectable electromagnetic shower of approximately 100 MeV. Thanks to the cosmic background suppression and the high intensity of the electron beam (up to 65 μA at 11 GeV), BDX will be able, with a 280 days run, to exceed by up to two orders of magnitude the sensitivity of current competitor experiments.
A primary concern for BDX is in the estimation of beam related backgrounds from penetrating particles such as muons and neutrinos produced in the electron beam dump. A hodoscope detector, called BDX-HODO was placed downstream of the dump to measure the rates of these beam related processes and validate the necessary Monte Carlo simulations.
Currently, the BDX collaboration is focused on the deployment and operation of a small detector, called BDX-MINI, built to perform a preliminary physics measurement searching for LDM at JLab. This test will pave the way to the realization of the full BDX experiment.
This thesis is focused on the following topics: the muon flux measurement behind Jlab Hall A beam-dump with BDX-HODO, the evaluation of the BDX experiment reach, including an optimization study for the detector, the construction, commissioning and sensitivity estimate of the BDX-mini detector and the evaluation of the secondary positrons contribution to the sensitivity of BDX and other electron-beam thick-target experiments searching for DM in the Dark Photon paradigm.
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Au, Eu Ving. "The Mechanics and Design of a Non-tearing Floor Connection using Slotted Reinforced Concrete Beams." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2010. http://hdl.handle.net/10092/4949.
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Ductile plastic hinge zones in beams of reinforced concrete frames are known to incur extensive damage and elongate. This ‘beam elongation’ can inflict serious damage to adjacent floor diaphragms, raising concerns of life safety. In light of this, the slotted reinforced concrete beam was investigated as a promising non-tearing floor substitute for conventional design. It consists of a conventional reinforced concrete beam, modified with a narrow vertical slot adjacent to the column face, running approximately three-quarters of the beam depth. Seismic rotations occur about the remaining concrete “top-hinge”, such that deformations are concentrated in the bottom bars of the beam, away from the floor slab, and beam elongation is minimised.
The inclusion of the slot raised several design issues which needed to be addressed. These were the shear transfer across the top-hinge, buckling of bottom longitudinal reinforcement, low cycle fatigue, bond anchorage of reinforcement in interior joints, interior joint design, detailing with floor units and beam torsion resulting from eccentric floor gravity loads. These issues were conceptually investigated in this project. It was found that most issues could be resolved by providing additional reinforcement and/or specifying alternative detailing.
As part of the experimental investigation, quasi-static cyclic tests were performed on in-plane beam-column joint subassemblies. Specimens tested included exterior and interior joint subassemblies with slotted-beams and a conventional exterior joint as a benchmark. This was followed by a test on a slotted-beam interior joint subassembly with precast floor units and imposed gravity load. Experimental tests revealed significant reductions in damage to both the beam and floor when compared to conventional beams. Issues of bar buckling, bond-slip and altered joint behaviour were also highlighted, but were resolved in the final test.
A simple analytical procedure to predict the moment-rotation response of slotted-beams was developed and verified with experimental results. This was used to perform sensitivity studies to determine appropriate limits for the concrete top-hinge depth, top-to-bottom reinforcement ratio and depth of diagonal shear reinforcement.
For the numerical investigation, a multi-spring model was developed to represent the flexural response of slotted-beams. This was verified with experimental tests and implemented into a five-storey, three-bay frame for earthquake time history analyses. To provide a benchmark, a conventional frame was also setup using the plastic hinge element developed by Peng (2009). Time history analyses showed that the slotted-beam frame response was very similar to the response of a conventional frame. Due to greater hysteretic damping, there was a slight reduction in the average interstorey drift and lateral displacement envelopes. The slotted-beam frame also exhibited 40% smaller residual drifts than the conventional frame.
The research carried out in this thesis showed slotted reinforced concrete beams to be an effective non-tearing floor solution, which could provide a simple and practical substitute for conventional reinforced concrete design.
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Davis, Richard Anthony. "The Effects of a Damage Arrestment Device on the Mechanical Behavior of Sandwich Composite Beams Under Four-Point Bending." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/506.
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The demand for an insert on composite sandwich structures to aid in the arrestment of face-core delamination is of great need. This research studies the use of a damage arrestment device (DAD) that connects the carbon fiber face sheets to the foam core to find whether an increase in the structural integrity of the sandwich beam results. Experimental analysis was employed to test the samples and was verified by a theoretical and finite element approach.
The mechanical properties of LTM45/CF1803 pre-impregnated carbon fiber and Last-A-foam FR 6710 polyvinylchloride foam were experimentally analyzed using ASTM D3039 and ASTM D1621 standards respectively to verify the manufacturer’s data for the given material. With all the mechanical data, the effects of adding DAD keys to a delaminated composite sandwich beam were studied under a four-point bending test using ASTM standard D6272 and compared with non-delaminated beams to see if an increase in ultimate strength could be achieved. The initial delamination in the beams under consideration was one inch in length and located in between the loaded span of the beam. Two control beams were utilized for comparison: one with no defects, and another with a one inch delamination introduced at the face-core interface. The DAD keys were added in two different configurations to potentially stop the delamination propagation and increase the ultimate strength. In the first configuration DAD keys were added 0.25 inches on either side of the initial delamination in the transverse direction and provided a significant increase in strength over the delaminated control beam. The second configuration had a DAD key running along the longitudinal axis of the sandwich beam and resulted in a significant increase in ultimate strength over the delaminated control beam. After testing ten successful samples for each of the six different configurations, it was concluded that the addition of DAD keys in both configurations significantly increased the structural integrity of both the delaminated and non-delaminated control beams.
With all the experimental data acquired, finite element models were created in COSMOS. The purpose of the finite element analysis was to validate the experimental results by comparing the deflections of the beam subjected to four-point bending during the experiment to the deflections found numerically. The deflections for the various DAD key configurations found in the experimental work were in agreement with the finite element results.
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Waldron, Christopher J. "Determination of the Design Parameters for the Route 601 Bridge: A Bridge Containing the Strongwell 36 inch Hybrid Composite Double Web Beam." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34414.
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The Route 601 Bridge spans 39 ft over Dickey Creek in Sugar Grove, VA and represents the first use of Strongwell's 36 in. double web beam (DWB) as the main load carrying members for a traffic bridge. The bridge was designed for AASHTO HS20-44 and AASHTO alternate military loading with a targeted deflection limit of L/800. For the preliminary design, conservative properties for the 36 in. DWB were assumed based on experience at Virginia Tech with Strongwell's 8 in. DWB used in the Tom's Creek Bridge. An elastic modulus (E) of 6,000 ksi and a shear stiffness (kGA) of 20,000 ksi-in2 were assumed and used with Timoshenko shear deformable beam theory to characterize the beams and determine the deflections.
This thesis details the experimental work conducted in conjunction with the design of the Route 601 Bridge, which had two goals. First, a deck-to-girder connection was tested to determine if a bolted connection could develop composite action between the girder and the deck. This connection was shown to provide a significant amount of composite action when used with the 8 in. DWB and a composite deck, but little or no composite action when used with the 36 in. DWB and a glue-laminated timber deck. Second, eleven 36 in. DWB's were tested to determine their stiffness properties (EI and kGA) to insure that these properties were above the values assumed in the preliminary design, and all the beams had stiffness properties that were close to or above the assumed values. The eleven beams were also proof tested to a moment equivalent to five times the service load moment to insure the safety of the Route 601 Bridge, and one beam was tested to failure to determine the failure mode and residual stiffness of the 36 in. DWB. Finally, based on these results eight beams were chosen for the Route 601 Bridge.<br>Master of Science
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RONG, RONG. "MICROMACHINED MAGNETIC DEVICES FOR ELECTRON BEAM CONTROL IN THE ELECTRON BEAM MICROCOLUMN." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1177358390.
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Benot, Morell Alfonso. "Beam position monitoring in the clic drive beam decelerator using stripline technology." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/64067.
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[EN] The Compact Linear Collider (CLIC) is an electron-positron collider conceived for the study of High-Energy Physics in the TeV center of mass energy region, is based on a two-beam operation principle: instead of using active elements (klystrons), the necessary RF power to accelerate the Main Beam (MB) is obtained from the deceleration of a high-current, moderate energy Drive Beam (DB) in the so-called Power Extraction and Transfer Structures (PETS). These structures emit an RF signal of about 130 MW power at 12 GHz. As this frequency is above the cut-o ff frequency of the fundamental mode for the specified beam pipe dimensions (7.6 GHz), the inference propagates from the PETS to the neighboring devices, including the Beam Position Monitors (BPM).
According to the CLIC Conceptual Design Report (CDR), an ef ficient beam position monitoring system for the CLIC DB decelerator needs to meet the following requirements:
- It should be as simple and economic as possible, as 41580 units are required, amounting to 75% of all CLIC BPMs.
- The signal processing scheme should not be a ffected by the PETS interference. This rules out processing the signals at the beam bunching frequency (12 GHz).
- The resulting position signal should detect changes in the beam position whose duration is 10 ns or longer.
- The required spatial resolution is 2 um for a 23 mm diameter vacuum pipe.
- Wide dynamic range: the electronic acquisition system must be able to process signals with extreme levels, induced by either very high (100 A) or very low (3 A) current beams.
This PhD thesis describes the electromagnetic and mechanical design of the first prototype BPM developed for the CLIC Drive Beam and its characterization tests in laboratory and with beam. The first two chapters introduce the CLIC project and review the state-of-the-art beam position monitoring techniques.
Chapter 3 presents the design of the BPM. The stripline technology has been selected, as it is the only one among the most commonly used BPM techniques to present a suitable frequency response to filter out the RF interference caused by the PETS. Choosing an appropriate length for the electrodes, it is possible to tune one the periodic notches in the stripline frequency response to 12 GHz. The influence of di erent electromagnetic and
geometrical aspects is also studied, such as beam coupling impedance or the ratio between longitudinal and transverse dimensions.
The design of the electronic acquisition system is presented in Chapter 4, considering the project requirements in terms of resolution (2 u m), accuracy (20 um) and time resolution (10 ns). Due to the high amount of units required, the number of electronics components has been minimized. As the designed signal processing scheme is based on charge integration, it can be adapted to di erent stripline pick-ups by simply modifying the attenuator settings according to the required output signal levels.
The laboratory characterization tests of the prototype stripline BPM, in the low and the high frequency ranges, performed with a thin wire and a coaxial waveguide, respectively, are described in Chapter 5. The measurement results are compared with the theoretical estimation and the electromagnetic field simulations. In addition, the high-frequency test reveals that the first prototype stripline BPM does not provide su cient suppression of the 12 GHz PETS RF interference. An additional study proposed several modifications and guidelines for a second prototype stripline BPM.
Finally, Chapter 6 presents the beam tests of the prototype stripline BPM at the CLIC Test Facility 3 (CTF3) in the Test Beam Line (TBL), a scaled version of the CLIC Drive Beam decelerator. Two types of tests were performed: linearity/sensivity and resolution. These results are compared to the ones in the laboratory characterization tests. An upper bound of the resolution is estimated performing a Singular Value Decomposition (SVD) analysis.<br>[ES] El Colisionador Lineal Compacto (Compact Linear Collider, CLIC), un colisionador de electrones y positrones concebido en el CERN para el estudio de la Física de Altas Energías en la región de los TeV, se basa en un principio de funcionamiento de doble haz: en lugar de emplear elementos activos (klystrons) para proporcionar la potencia RF requerida para acelerar el haz principal (Main Beam, MB), ésta se obtiene de la deceleración de un haz secundario (Drive Beam, DB), de alta corriente y energía moderada, en las llamadas estructuras de extracción y transferencia de potencia (Power Extraction and Transfer Structures, PETS). Estas estructuras emiten una señal interferente RF de más de 130 MW de potencia a 12 GHz, que, por estar localizada en una frecuencia superior a la de corte del modo fundamental en el tubo de vacío del haz (7.6 GHz), se propaga por éste hacia los dispositivos adyacentes, entre los cuales se encuentran los sistemas de monitorización de la posición (Beam Position Monitor, BPM).
De acuerdo con el informe conceptual de diseño de CLIC (Conceptual Design Report, CDR) , un sistema eficiente de monitorización de la posición del haz en el decelerador del haz secundario deberá cumplir los siguientes requisitos:
- Debe ser lo más sencillo y económico posible, ya que se precisan 41580 unidades: el 75% de todos los BPMs de CLIC.
- El procesado de señal en el sistema de adquisición deberá ser inmune a la interferencia generada en las PETS. Esto excluye la solución habitual de procesar las señales del BPM a la frecuencia de pulsado del haz (12 GHz).
- La señal de posición resultante del procesado debe ser capaz de detectar cambios en la posición del haz de duración igual o mayor a 10 ns (resolución temporal).
- La resolución espacial requerida es de 2 um para un tubo de vacío de 23 mm de diámetro, con una calibración precisa.
- Amplio rango dinámico: el sistema electrónico de adquisición del BPM debe poder resistir los altos valores de señal provocados por los casos de desviación extrema del haz nominal (se contempla una desviación máxima de la mitad del radio del tubo), así como detectar las señales inducidas por las configuraciones de haz con menor carga de todas las previstas, cuyos niveles serán muy débiles.<br>[CAT] El Col·lisionador Lineal Compacte (Compact Linear Collider, CLIC), un col·lisionador d'electrons i positrons concebut per l'estudi de la Física d'Altes Energies a la regió dels TeV (energía del centre de massa), es basa en un principi de funcionament de doble feix:en lloc de fer servir elements actius (klystrons) per proporcionar la potència RF requerida per accelerar el feix principal (Main Beam, MB), aquesta s'obtè de la desacceleració d'un feix secundari (Drive Beam, DB), d'alt corrent i energia moderada, a les anomenades estructures d'extracció i transferència de potència (Power Extraction and Transfer Structures, PETS). Aquestes estructures emeten una senyal interferent RF de més de 130 MW de potència a 12 GHz, que, pel fet d'estar localitzada a una freqüència superior a la de tall del mode fonamental al tub de buit del feix (7.6 GHz), es propaga a través d'aquest fins els dispositius adjacents, entre els quals trobem els sistemes de monitorització de la posició (Beam Position Monitor, BPM).
D'acord amb l'informe conceptual de disseny de CLIC (Conceptual Design Report, CDR), un sistema eficient de monitorització de la posició del feix al desaccelerador del feix secundari haurà de complir els següents requisits:
¿ - Ha de ser el més senzill i econòmic possible, ja que es necessiten 41580 unitats: el 75% de tots els BPMs de CLIC.
¿ - El processat de la senyal al sistema d'adquisició haurà de ser inmune a la interferència generada als PETS. Això exclou la solució habitual de processar les senyals del BPM a la freqüència de pulsacions del feix (12 GHz).
¿- La senyal de posició resultant del processat ha de ser capaç de detectar canvis a la posició del feix de durada igual o més gran que 10 ns (resolució temporal).
¿- La resolució espaial necessària és de 2 um per a un tub de buit de 23 mm de diàmetre.
¿- Ampli rang dinàmic: el sistema electrònic d'adquisició del BPM ha de poder processar senyals amb nivells extrems, induïdes per feixos de molt alt (100 A) i molt baix (3 A) corrent.<br>Benot Morell, A. (2016). Beam position monitoring in the clic drive beam decelerator using stripline technology [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64067<br>TESIS
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Allahverdiyev, Rovshan. "Effects of beam configuration on dynamic properties and seismic performances of multi-storey frame building models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
The present study aims at comparing the dynamic properties and seismic performances offered by reinforced concrete frame structures characterised by different beams distribution.
Multi-storey regular frame buildings are considered as reference structures. Different models are then developed according to various layout of the beams (x-direction is the longitudinal direction, whilst y-direction is the transversal one): (1) beams placed along the x-direction at the odd storeys and placed along the y-direction at the even storeys; (2) beams placed along the y-direction at the odd storeys and placed along the x-direction at the even storeys; (3) and (4) alternating beams every two storeys; (5) beams placed along the x-direction at all storeys; (6) beams placed along the y-direction at all storeys; (7) complete three-dimensional frame with beams placed along both the x- and the y-direction at all storeys. In all models, smaller perimeter beams are placed along the direction orthogonal to the one of the main beams.
Modal analysis has been conducted to evaluate the influence of beams distribution on the period of vibration. Response spectrum and time-history dynamic analyses have been carried out to assess the effects of beams distribution on the base shear and base bending moments, top-storey displacements, interstorey displacements and floor accelerations.
On the contrary of what could be expected, the results indicate that structures with beams alternating every storey do not behave unfavorably with respect to the complete three-dimensional frames. In more detail, two effects may be clearly recognized: one associated to the period and one associated to the static scheme. The former acting basically on the base shear; the latter acting mainly on the base bending moment. The understanding of the influence of beams distribution on frame structures is useful when dealing with seismic vulnerability assessment of existing buildings and design of new buildings.
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Felício, Vanessa Domiciano. "Análise experimental de vigas de aço e mistas de aço e concreto parcialmente revestidas em situação de incêndio." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-24012019-122558/.
Full textAbstract:
Sistemas mistos de aço e concreto são aqueles em que o elemento de aço trabalha estruturalmente em conjunto com o concreto. Essa associação dos materiais resulta numa melhor utilização de ambos os materiais tanto quanto à capacidade resistente, quanto em caráter construtivo, funcional e estético. O presente trabalho tem como finalidade a análise de vigas de aço e mistas de aço e concreto parcialmente revestidas em situação de incêndio. Esse estudo tem grande importância tendo em vista os incidentes com altas temperaturas em edificações ocorridos ao longo dos anos. O aumento de temperatura nas estruturas é um efeito nocivo, pois prejudica a rigidez e a resistência dos materiais, podendo levar estruturas ao colapso. As análises das vigas mistas aço e concreto parcialmente revestidas em situação de incêndio foram feitas através de análises experimentais que foram realizadas no forno horizontal à gás do Laboratório de Engenharia de Estruturas da EESC/USP. Foram realizados ensaios de flexão em pontos em altas temperaturas e a variável nos ensaios foi o fator de carga aplicado no meio do vão das vigas. Foi possível comparar o comportamento das vigas metálica e mistas, bem como as temperaturas em vários pontos ao longo do elemento por meio de termopares colocados em pontos estratégicos. Transdutores de deslocamento também foram usados para saber o valor de deslocamento nos apoios e no meio do vão das vigas. Uma análise térmica bidimensional através do ABAQUS também foi feita para comparação de resultados. Conclui-se que para uma mesma carga aplicada os deslocamentos foram mais expressivos nos ensaios das vigas em situação de incêndio se comparados aos valores obtidos nos ensaios à temperatura ambiente, observou-se o efeito benéfico do revestimento de concreto ao perfil metálico, responsável por um ganho expressivo de resistência ao fogo quando comparado aos elementos puramente metálicos e por fim obteve-se boa concordância entre as temperaturas encontradas por modelagem numérica através do ABAQUS e dos ensaios experimentais realizados.<br>Composite steel and concrete systems are those in which the steel element works structurally in conjunction with the concrete. This association of the materials results in a better use of both materials as much as the resistant capacity, as well as in a constructive, functional and aesthetic character. The present work has the purpose of analyzing steel beams and mixed steel and concrete partially coated in a fire situation. This study has great importance in view of the incidents with high temperatures in buildings that have occurred over the years. The increase in temperature in the structures is a harmful effect, as it impairs the rigidity and the resistance of the materials, which can lead to collapse structures. The analyzes of the composite steel and concrete composite beams in a fire situation were made through experimental analyzes that were carried out in the horizontal gas furnace of the Laboratory of Structural Engineering of EESC/USP. Bending tests were performed on points at high temperatures and the variable in the tests was the load factor applied in the middle of the span of the beams. It was possible to compare the behavior of the metallic and composite beams as well as the temperatures at various points along the element by means of thermocouples placed at strategic points. Displacement transducers were also used to know the displacement value in the supports and in the middle of the span of the beams. A two-dimensional thermal analysis through ABAQUS was also done for comparison of results. It was concluded that for the same applied load the displacements were more expressive in the tests of the beams in the fire situation compared to the values obtained in the tests at room temperature, the beneficial effect of the concrete coating was observed on the metallic profile, responsible for a an expressive gain of fire resistance when compared to the purely metallic elements and finally a good agreement was obtained between the temperatures found by numerical modeling through ABAQUS and the experimental tests performed.
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Staley, Alan Joseph. "A Finite Difference Approach to Modeling High Velocity/Variable Loads using the Timoshenko Beam Model." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76954.
Full textAbstract:
Electromagnetic launchers (railguns) are set to replace traditional large caliber ship mounted cannons in the near future. The success of the railgun depends heavily upon a comprehensive understanding of beam behavior during periods of heavy dynamic loading. It is hypothesized that the combination of velocity transition effects, electromagnetic loading, and other non-linear or design specific effects contribute to areas of high stresses/strains over the length of the rail/beam during launch.
This paper outlines the use of the Timoshenko beam model, a model which builds upon the traditional Bernoulli-Euler beam theory with the addition of shear deformation and rotary inertia effects, a necessity for high wave velocities. Real-world experimental setups are simplified and approximated by a series of linear springs and dampers for model prediction and validation.
The Timoshenko beam model is solved using finite difference (FD) methods for the approximation of spatial derivatives and MATLAB ordinary differential equation (ODE) solvers. The model shows good convergence and precision over a large range of system parameters including load velocities, foundation stiffness values, and beam dimensions. Comparison to experimental strain data has validated model accuracy to an acceptable level. Accuracy is further enhanced with the inclusion of damping and non-linear or piecewise effects used to mimic experimental observations. The MATLAB software package presents a valid preliminary analysis tool for railgun beam and foundation design while offering advantages in ease of use, computation time, and system requirements when compared to traditional FEA tools.<br>Master of Science
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Alsaeed, Kalel. "Determination of the Shape of a Flattening Filter Free (FFF) Radiation Beam When Modified by a Physical Wedge." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1514514772104065.
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Hannah, Mark Alexander. "Investigation of the design recommendations of reinforced concrete beam-column joints." Thesis, University of Canterbury. Civil Engineering, 2013. http://hdl.handle.net/10092/10981.
Full textAbstract:
A parametric analysis on 58 beam-column joint specimens has been conducted. The analysis considered 14 fundamental parameters in the design of each specimen and two performance indicators: the horizontal shear strength ratio between the maximum measured strength and the theoretical strength at beam yield, and the nominal curvature ductility of the adjacent beams. Each parameter was varied by a power function, while the linear correlation coefficient between each parameter and performance indicator was recorded. A combined multiple parameter analysis was then conducted to show the interaction of the design parameters and show the representative influences of each parameter based on the magnitude of the applied power functions.
Two design equations were constructed from the most influential design parameters, one for each performance indicator. The shear strength ratio was found to be governed by the horizontal joint shear stress, the column axial stress and the yield strength of the longitudinal beam reinforcement. The available curvature ductility of the adjacent beams was also found to be governed by the horizontal joint shear stress, the column axial stress and the yield strength of the longitudinal beam reinforcement, but also the quantity of the horizontal joint shear reinforcement.
The influence of the column axial stress on both performance indicators was found to be best represented by a quadratic function. This was because the column axial stress was found to be beneficial up to stress levels of , but axial stress levels exceeding were found to be detrimental to the performance of the beam-column joint, compared to a joint with no axial stress on the columns. The non-linear relationship of the column axial stress agreed with the design assumptions in NZS 3101 for low axial stress values, but at higher axial stress values NZS 3101 assumes a continued performance increase as a result of increasing axial stress, which has been found to be un-conservative. Additionally, an interaction between the column axial stress and the horizontal joint shear stress has been identified. As a result, beam-column joints with high column axial stress levels above 0.40 and horizontal joint shear stress levels in the order of have been shown to fail in a brittle crushing of the concrete in the joint core. Considering this behaviour, it is recommended that the column axial stress levels in earthquake designed beam-column joints should not exceed 0.35 .
The results of the parametric analysis were then compared against the current NZS 3101 design equations for conservatism. It was found that a reduction in the horizontal joint shear reinforcement may be possible for beam-column joints incorporating Grade 300 steel in the longitudinal reinforcement of the beams and axial stress levels below 0.25 , but when Grade 500 steel is used or the column axial stress is greater than 0.25 , an increase in the joint shear reinforcement is required compared to NZS 3101. The current NZS 3101 design requirement of at least 40% of the joint shear force, to be resisted by means of joint shear reinforcement, has been found to be appropriate.
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Cevro, Mirza. "A study of the deposition of oxide thin films by ion beam techniques." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262666.
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Filho, José Eurípedes Ferreira de Jesus. "Método beam search aplicado ao problema de escalonamento de tarefas flexível." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-07082013-145142/.
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O Job Shop Scheduling Problem é um problema NP-Difícil que chama a atenção de muitos pesquisadores devido seu desafio matemático e sua aplicabilidade em contextos reais. Geralmente, principalmente em cenários próximos aos de fábricas e indústrias, obter um escalonamento ótimo por meio de métodos computacionais exatos implica em um alto desprendimento de tempo. Em contrapartida, devido às exigências de um mercado cada vez mais competitivo, as decisões de onde, como, quando e com o que produzir devem ser tomadas rapidamente. O presente trabalho propõe o desenvolvimento de um método heurístico Beam Search para solucionar o Job Shop Scheduling Problem e o Flexible Job Shop Scheduling Problem. Para isso, inicialmente um algoritmo do tipo list scheduling é definido e então o método Beam Search é construído baseado neste algoritmo. Os métodos propostos foram avaliados em diferentes níveis de complexidade utilizando instâncias da literatura que retratam diferentes cenários de planejamento. Em linhas gerais, as soluções encontradas se mostraram bastante competitivas quando comparadas a outras soluções da literatura.<br>The Job Shop Scheduling Problem is a NP-Hard problem which draws the attention of researchers due to both its mathematical challenge and its applicability in real contexts. Usually, mainly in industry and factory environments, an optimal schedule got by the use of exact computational methods implies in a long spending time. On the other hand, due to a more and more competitive marketplace, the decisions on where, how, when and with which to produce must be taken quickly. The present work proposes the development of an heuristic Beam Search method to solve both the Job Shop Scheduling Problem and the Flexible Job Shop Scheduling Problem. To that end, at rst a list scheduling algorithm is dened and then the Beam Search method is built based on the list scheduling algorithm. The proposed methods were evaluated over dierent complexity levels using instances from the literature that report dierent planning environments. In general terms, the solutions implemented have been proved very competitive when compared against other solutions in the literature.
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Mauro, Rodrigo Antonio Pereira. "Dosimetria em tomografia computadorizada de feixe cônico odontológica." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-21112017-193930/.
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Os objetivos deste trabalho foram caracterizar os níveis de referência de radiodiagnóstico para a tomografia computadorizada de feixe cônico odontológica e as características de desempenho dos equipamentos como quilovoltaqgem de pico, rendimento, camada semirredutora, etc., com o intuito de conhecer os níveis dosimétricos em que os pacientes estão expostos, permitindo assim identificar protocolos de aquisição de imagem mais adequados, levando-se em consideração os princípios de radioproteção, e também testar a capacidade de tais equipamentos em alcançar uma imagem de qualidade. A Cone Beam Computed Tomography tem se tornado ferramenta extremamente útil na utilização em procedimentos radiológicos na área odontológica, pois, a riqueza de informações que a imagem 3D trás para o planejamento cirúrgico ou em qualquer procedimento, minimiza as possibilidades de erros, possibilita diagnósticos mais confiáveis e claros, tendo influência direta no resultado final esperado pelo paciente. Por se tratar de uma técnica de imagem que utiliza radiação ionizante, deve-se ter uma atenção criteriosa voltada para os níveis de radiação, além de implementar uma rotina de controle de qualidade. O parâmetro dosimétrico mais utilizado em tomografia computadorizada é o Computed Tomography Dose Index, porém, quando aplicado à tomografia odontológica, a geometria cônica do feixe e ainda a extensão do campo de visão tornam essa grandeza inviável e enganosa, assim, faz-se necessária a padronização de uma grandeza dosimétrica mais otimizada, para evitar a subestimação dos níveis de dose em feixes de ampla abrangência. O PKA tem sido utilizado como uma possível grandeza dosimétrica em tomografia odontológica, uma vez que em sua metodologia de medida, todo o feixe é englobado pelo medidor, não depende da distância fonte - detector, além de ser sensível aos parâmetros de exposição. Diante disso, propõe-se o PKA ser utilizado para estabelecimento dos níveis de dose de referência em diagnóstico odontológico. Os valores PKA obtidos para este estudo estão em uma faixa entre 34,6 mGy.cm^2 e 2901,6 mGy.cm^2, com valor médio de 980,7 mGy.cm^2. Os valores encontrados para os níveis de referência de radiodiagnóstico calculados a partir do 3º quartil estão divididos em três classes referentes ao tamanho do campo de visão, onde para campos pequenos, médios e grandes os valores são 1241 mGy.cm^2, 1521 mGy.cm^2 e 1408 mGy.cm^2 respectivamente, e 1446 mGy.cm^2 é o valor global independente do campo de visão. Os testes de controle de qualidade foram todos positivos, com uma atenção para o i-CAT FLX, que excedeu levemente o limite aceitável para a exatidão do kVp. Uma comparação entre CTDI100 e CTDI300, reportou que o CTDI300 é em média 49% maior em relação ao CTI100. Os níveis de referência de radiodiagnóstico são representativos dos níveis de dose otimizados, e servem como base para adequação e otimização dos parâmetros de exposição do equipamento. Os testes de controle de qualidade alertam para possíveis irregularidades no funcionamento do tomógrafo, e deve complementar obrigatoriamente a rotina dos procedimentos clínicos.<br>The objectives of this study are to characterize the radiodiagnostic reference levels for computed tomography of dental cones and as performance characteristics of equipment such as peak kyvoltage, yield, semi-reducing layer, etc., in order to know the levels of the values in that users are exposed, thus allowing to identify more adequate image acquisition protocols, taking in basic concepts of radioprotection, and also to test the capacity of such equipment in a quality image. The Cone Beam CT scan has become active, useful in medical, medical, dental, on the Internet, in any situation, minimizes as possibilities of errors, allows for more reliable and clear diagnoses, having a direct influence on the final result expected by the patient. Because it is an imaging technique that uses ionizing radiation, careful attention should be given to radiation levels, in addition to implementing a quality control routine. The dosimetric parameter most commonly used in computed tomography is the Computed tomography dose index, however, when applied to dental tomography, the conic geometry of the beam and still the extension of the field of view make this greatness unfeasible and deceptive, so it is done The. standardization of a more optimized dosimetric quantity, to avoid an underestimation of the dose levels in beams of wide range. The PKA has been used as a possible dosimetric magnitude in dental tomography, since in its measurement methodology, the whole beam is encompassed by the meter, it does not depend on the source - detector distance, besides being sensitive to the exposure parameters. Therefore, it is proposed that PKA be used for the establishment of reference dose levels in dental diagnosis. The PKA values obtained for this study ranged from 34.6 mGy.cm^2 to 2901.6 mGy.cm^2, with a mean value of 980.7 mGy.cm^2. The values found for the levels of radiodiagnostic reference values calculated from the 3rd quartile are divided into three classes referring to the size of the field of vision, where for small, medium and large fields are the values are 1241 mGy.cm^2, 1521 mGy.cm^2 and 1408 mGy.cm^2 respectively, and 1446 mGy.cm^2 is the global independent value of the field of view. The quality control tests were all positive, with an attention to the i-CAT FLX, which slightly exceeded the acceptable limit for kVp accuracy. A face between CTDI100 and CTDI300, reported that the CTDI300 is on average 49% higher than the CTI100. Radiodiagnostic reference levels are representative of optimized dose levels and serve as a basis for adequacy and optimization of the exposure parameters of the equipment. The quality control tests alert to possible irregularities in the operation of the tomograph, and develop properly from the clinical process.
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Ferrarotti, Alberto. "New approaches for linear and nonlinear analyses of thin-walled members in the framework of Generalized Beam Theory." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18631.
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The Generalized Beam Theory (GBT) is a reliable tool for the linear and nonlinear analysis of thin-walled members (TWMs). Based on expressing the displacement field as a linear combination of assumed deformation fields (i.e., trial functions) and unknown amplitude functions (i.e., linear coordinates), it relies on two steps: (a) selection of the deformation fields (i.e., cross-section analysis); and (b) solution of an equivalent 1D problem (i.e., member analysis). This thesis proposes new approaches for the GBT-based analysis of TWMs, in particular: (a) a novel approach for the cross-section analysis, (b) a GBT formulation for the partial interaction analysis of multi-component TWMs, (c) a displacement - based GBT for composite perforated TWMs, and (d) a nonlinear GBT for the analysis of arbitrary TWMs. The novel cross-section analysis is based on the so-called dynamic approach (GBT-D) and relies on the solution of a very limited number of constrained eigenvalue problems. It is much simpler to use than the classic static approach, in addition to provide even better results from the point of view of accuracy and symmetry of obtained displacement fields. The proposed cross-section analysis is suited for developing a GBT-based formulation for the study of the linear-elastic behavior of multi-component TWMs. The novelty of the approach consists on its ability to accurately model the partial interaction between the different components forming the cross-section in both longitudinal and transverse directions. The displacement-based GBT for the analysis of composite TWMs is based on a variable transform which allows to express the unknown linear coordinates in terms of cross-section nodal degrees-of-freedom (DOFs). The proposed approach leads to a beam-like finite element equivalent to an assembly of flat quadrilateral shell elements. Finally, the nonlinear GBT is developed according to the nonlinear Galerkin method, which calls for the evaluation of nonlinear (passive) trial functions, to be used in conjunction with linear (active) ones, in describing the displacement field. Within this framework, equilibrium paths can be determined by using few linear (and corresponding passive) trial functions, supplying good results when compared with burdensome finite-element solutions.
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LOPES, ELVIS DINATI CHANTRE. "NON-LINEAR DYNAMICAL ANALYSIS OF COMPOSITE FLOORS CONSIDERING THE EFFECTS OF PARTIAL INTERACTION AND BEAM TO COLUMN AND BEAM TO BEAM CONNECTIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=21173@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>O crescimento dos problemas de vibrações excessivas em edificações oriundos de atividades humanas rítmicas tem conduzido à necessidade de desenvolvimento de critérios específicos para projetos estruturais submetidos à ação dessas cargas dinâmicas. Esta foi uma das motivações para o desenvolvimento de uma metodologia de análise para investigação da resposta dinâmica de sistemas estruturais de pisos mistos (aço-concreto). Objetiva-se verificar a influência da interação aço-concreto (interação total e parcial) e, bem como, das ligações estruturais (ligações viga-coluna e viga-viga), sobre a resposta dinâmica não linear de pisos mistos (aço-concreto). Deste modo, são utilizados três modelos de carregamento dinâmico representativos das atividades humanas rítmicas referentes a saltos à vontade e ginástica aeróbica. As cargas dinâmicas são obtidas por meio de testes experimentais e, também, com base em normas e recomendações internacionais de projeto. Com referência a interação aço-concreto, vários tipos de conectores (tipo stud e perfobond) são considerados ao longo da investigação. Mesmo sabendo-se que a análise de vibrações de pisos induzidas por atividades humanas tem sido alvo de inúmeras investigações ao longo dos últimos dois séculos (1828-2012), os autores desconhecem na literatura técnica um trabalho de pesquisa tão abrangente, no que diz respeito à análise dinâmica não linear de pisos mistos (aço-concreto) submetidos à ação de atividades humanas rítmicas, com base na consideração dos efeitos dos conectores (interação aço-concreto) e das ligações (viga-coluna e viga-viga). Diante do exposto, o quadro global investigado neste trabalho de pesquisa demonstra, claramente, um indicativo de que os critérios de projeto devem levar em conta o caráter dinâmico da excitação e, especialmente, a influência da interação aço-concreto e das ligações estruturais, no que tange a verificação dos estados limites de utilização (conforto humano), associados ao comportamento estrutural de pisos mistos de edificações.<br>The increasing incidence of building vibration problems due to human activities led to a specific design criterion to be addressed in structural design. This was the main motivation for the development of a design methodology centred on the steel-concrete composite floors non-linear dynamic response submitted to loads due to human rhythmic activities. This way, the main objective of this work is to investigate the influence of steel-concrete interaction degree (from total to various levels of partial interaction) and the beam-to-column and beam-to-beam connections effect over the non-linear dynamic behaviour of composite floors. Thus, three dynamic loading models were utilized, in order to simulate human rhythmic activities such as jumping and aerobic gymnastics. The dynamic loads were obtained through experimental tests and based on international design codes and recommendations. Regarding the steel-concrete interaction degree, the stud and perfobond connectors are considered in this investigation. Even though this topic has been studied in the technical literature for nearly two centuries, the steel-concrete composite floors non-linear dynamic analysis submitted to human rhythmic activities has not yet been addressed so comprehensively, as far as the authors are concerned in this investigation, based on the consideration of the connectors (steel-concrete interaction degree) and connections (beam-to-column and beam-to-beam) effects. Considering all aspects mentioned before, the results have demonstrated that the design criteria should include the original nature of the dynamic excitation and, specially, the steel-concrete interaction degree and structural connections effects when the steel-concrete composite floors structural behaviour, related to the serviceability limit states (human comfort) are investigated.
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Nakamura, Hideo. "The effect of beam oscillation rate on Al evaporation behavior in the electron beam melting process." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27944.
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Electron beam hearth melting process is widely used in producing superalloys, Ti and its alloys because of its excellent metallurgical characteristics. However, one of the disadvantages of the process is that alloying elements with high vapor pressure evaporate under the highly reduced operating pressure. This makes it very difficult to carry out an accurate chemical composition control. In order to prevent the excess evaporative loss by reducing the superheating of the molten pool, the beam scanning technique is employed in normal operation. Although the effect of this technique is well known empirically, few fundamental studies' have been made to date. The purpose of this study is, therefore, to clarify the quantitative effect of the beam oscillation rate on the evaporation behavior.
Small amounts of Ti-6Al-4V alloy were melted in an EB melting furnace. The temperature on the melt surface was measured in situ by an optical pyrometer during the melting period. The evaporation loss of both Ti and Al was also investigated.
On the basis of the experimental results, a two dimensional unsteady heat and mass transfer model was developed. (A one dimensional model was developed in the case of a stationary beam.) The model was used to investigate the effect of the beam oscillation rate on the evaporation behavior and also to discuss the optimum beam scanning rate. It was clearly shown that the evaporative loss of both Ti and Al could be suppressed by the increase of the beam oscillation rate. With the beam oscillation rate at more than 1.0 Hz, however, this effect could not be observed clearly anymore. It was also found that the beam scanning technique is useful not only in controlling Al concentration, wt%Al, but also in suppressing the total evaporative loss of both Ti and Al.<br>Applied Science, Faculty of<br>Materials Engineering, Department of<br>Graduate
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Jahnke, Cristiane. "Sintonia dos parâmetros de operação do primeiro estágio de aceleração do Mícroton do IFUSP." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17042012-121908/.
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O Laboratório do Acelerador Linear (LAL) do Instituto de Física da Universidade de São Paulo está construindo um acelerador de elétrons do tipo Mícrotron. O acelerador possui dois estágios de aceleração: o Mícrotron booster e o Mícrotron Principal. Atualmente, o sistema injetor do acelerador, que é um acelerador linear, dispõe de um feixe de elétrons de 1,9 MeV. Este feixe será inserido no primeiro estágio de aceleração, o Mícrotron booster, que já está construído e será testado em breve. Sua função é elevar a energia do feixe para 5 MeV. O objetivo deste trabalho é o de otimizar os parâmetros de operação do Mícrotron booster por meio de simulação. Também tivemos como objetivo estudar a viabilidade da adaptação do projeto original, com feixe de entrada de 1,765 MeV, para um feixe de entrada de 1,9 MeV. Tendo como foco principal encontrar a admitância do acelerador, foram desenvolvidas algumas rotinas de simulação. A admitância do Mícrotron booster para um feixe de 1,765 MeV foi calculada em 3,08 pi mm.mrad, 0,58 pi mm.mrad e 0,38 pi keV.rad para os espaços de fase horizontal, vertical e longitudinal, respectivamente. Para o feixe de 1,9 MeV, uma condição de aceleração foi encontrada e os valores de admitância foram 3,65 pi mm.mrad, 0,62 pi mm.mrad e 0,77 pi keV.rad para os mesmos espaços de fase. Dados de caracterizações do feixe, realizados em trabalhos anteriores foram utilizados para determinar a configuração das lentes quadrupolares responsáveis pela inserção do feixe no acelerador. Tais simulações darão suporte ao início de operação do Mícrotron booster, auxiliando na determinação dos parâmetros iniciais de operação e otimização dos parâmetros finais.<br>The Laboratório do Acelerador Linear is building a racetrack microtron electron accelerator. It has two acceleration stages: the booster and the main microtron. The injection system has already been commissioned and is delivering a 1.9-MeV continuous wave beam. This beam will be injected in the booster stage, which is ready to be commissioned, and should increase the energy to 5 MeV. The aim of this work is to optimize the operation parameters of the booster stage by means of simulation tools. We also studied the feasibility of injecting the 1.9 MeV beam in the booster, which has been designed to operate with a 1.765 MeV beam. Some simulation routines had to be developed in order to determine the admittance of the booster stage. For the 1.765 MeV beam the admittances were determined to be 3.08 pi mm.mrad, 0.58 pi mm.mrad, and 0.38 pi keV.rad for the transverse horizontal, transverse vertical, and longitudinal phase spaces, respectively. For the 1.9 MeV injection beam we were able to find a viable acceleration condition, with slightly better admittances: 3.65 pi mm.mrad, 0.62 pi mm.mrad, and 0.77 pi keV.rad, for the same phase spaces cited above. The injection beam has been characterized previously, and the available data were used, in the simulation codes, to match the transverse beam emittances of the injector to the transverse beam admittances of the booster. The phase space manipulations were accomplished by tuning a quadrupole triplet placed before the booster entrance. These simulations are intended as a supporting tool for the commissioning of the booster stage, helping the experimental determination of the working parameters and their optimization.
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Hochanadel, Joris Erich. "Effect of Beam Characteristics and Process Parameters on the Penetration and Microstructure of Laser and Electron Beam Welds in Stainless Steel and Titanium." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu160503470688313.
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