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1
Matalgah, Ziyad. "Second Order Rotational Effect On Nonradial Oscillations In Delta-scuti Stars." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604741/index.pdf.
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In this work the effect of rotation on oscillation frequencies have been inves-
tigated . Rotation has been treated as a perturbation and detailed calculations
were done on the infuence of second order rotation . We used an evolutionary
model of DELTA-Scuti star V1162 Ori with a mass of 1:8 solar mass. The eigenfrequencies
were calculated in two cases , the slow rotation case with vsini = 46km/s and
the fast rotation case with vsini = 61.9km/s. Calculation were carried out by
a modifed oscillation program and results were compared to observations .
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Matalgah, Zıyad. "Second order rotational effect on nonradial oscillations in ℓ-scuti stars." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604741/index.pdf.
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Dogan, Gulnur. "The Effect Of Rotation, Up To Second Order, On The Oscillation Frequencies Of Some Delta-scuti Stars." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608873/index.pdf.
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In this work, the effect of rotation on the oscillation frequencies of some radially and nonradially oscillating Delta-Scuti stars have been explored. Rotation has been considered as a perturbation and treated up to the second order. Series of evolutionary models have been calculated for the oscillating stars in question and compared with the observational parameters. Three stars are considered: V350 Peg with no rotation, CC And with a rotational velocity Vsini=20 km/s, and BS Tuc with Vsini=130 km/s.
We find that splitting in the oscillation frequencies are conspicuous especially in fast rotating stars, with a considerable contribution from the related terms due to
second order effect.
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McCord, John J. "Investigating the topological order of an ansatz for the fractional quantum Hall effect in the half-filled second Landau level." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10240257.
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The Moore-Read Pfaffian and anti-Pfaffian states have been under scrupulous review as candidates which describe the fractional quantum Hall effect at filling factor 5/2. Quantum states in the universality class of the Moore-Read Pfaffian/anti-Pfaffian have non-trivial intrinsic topological order and support low-energy non-Abelian excitations that have applications in fault-tolerant topological quantum computing schemes. Both states are exact ground states of three-body Hamiltonians that explicitly break particle-hole symmetry. We study the topological order of a competing ansatz state &PSgr;2 that is the exact ground state of a two-body Hamiltonian that preserves particle-hole symmetry. In particular, we calculate the bipartite entanglement entropy and spectra in the lowest Landau level in the spherical geometry for &PSgr; 2. We perform such calculations for a finite number of electrons up to 14. We then extrapolate to the thermodynamic limit the topological entanglement entropy γ as a measure of the topological order of the ansatz and compare to the known value of the Moore-Read Pfaffian/anti-Pfaffian state. We also study the orbital entanglement spectra for &PSgr;2 and compare with the Moore-Read Pfaffian and two-body Coulomb ground states. We show that our extrapolation of γ lies within the uncertainty of the known value of γ for the Moore-Read Pfaffian state, and that the orbital entanglement spectra of &PSgr;2 assumes a similar structure to that of the two-body Coulomb interaction.
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Manigault, Patrick Alexander. "Second order luminescent saturation effects in phosphors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/30700.
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Zhang, Yanyang. "Second-order effects on uncertainty analysis calculations." Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-10292002-122359.
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Hellström, Jonas. "Nanosecond optical parametric oscillators and amplifiers based on periodically poled KTiOPO4." Doctoral thesis, KTH, Physics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3269.
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Optical parametric oscillators (OPOs) and optical parametricamplifiers (OPAs) constitute a class of optical frequencyconverting devices that have many possible applications, e.g.in range finding, molecular spectroscopy and medicine. They canconvert the frequency of the incident pump field with highefficiency, and generate two waves at new frequencies that willbe continuously tuneable over a wide spectral range. Virtuallyany wavelengths within the transparency region of the nonlinearmaterial can be generated if the material can bequasi-phasematched (QPM). In addition, QPM gives thepossibility to utilise the largest nonlinear tensor element ofthe material and allows walk-off free interaction between thewaves.
The aims of this thesis have been to investigate thepossibility to use QPM KTiOPO4crystals as nonlinear material in nanosecond OPOsand OPAs operating at room-temperature, and to explore theadvantages and shortcomings of these devices. The technique ofelectric field poling has been employed to implement the QPMstructure in flux grown KTiOPO4(KTP).
The main conclusion is that periodically poled KTP (PPKTP)is a suitable material to use in nanosecond OPOs and OPAs. Thematerial properties that foremost make KTP into an attractivenonlinear material are: The large value of the nonlinearcoefficient d33, the high resistance to optically inducedbreakdown, the low susceptibility to grey-track formation, theinsensitivity to the photorefractive effect, the widetransparency and the low coercive field.
The thesis shows that it is possible to pole large volumesof KTP with a high quality of the QPM structure. Highlyefficient nanosecond OPOs have been constructed during thisproject. Maximum conversion efficiencies have reached 45 % inthe case of a singly resonant OPO (SRO) built around a 3 mmthick PPKTP crystal. Total pulse energies for both the signal(1.72 µm) and the idler (2.8 µm) of up to 18 mJ wasreached and an average output power of 2 W was obtained forthis sample. However, up to 24 W was produced in a doublyresonant OPO operating close to degeneracy. The efficiencyreached 48 % for that case. Truly continuous and very widespectral tuning has also been demonstrated, as well as a narrowbandwidth OPO operating on one single longitudinal mode.
Keywords:optical parametric oscillators, opticalparametric amplifiers, quasi-phasematching, KTiOPO4, nonlinear optics, frequency conversion, periodicelectric field poling, ferroelectrics, high-order secondharmonic generation, electro-optic effect.
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Mayer, Charlotte. "Nouveaux matériaux magnétocaloriques à base de terres rares pour la réfrigération magnétique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00649399.
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Les travaux présentés dans ce manuscrit portent sur la synthèse et la caractérisation de nouveaux matériaux magnétocaloriques à basse de terres rares pour la réfrigération magnétique. Le premier chapitre constitue une introduction aux notions d'effet magnétocalorique et de réfrigération magnétique et dresse un état de l'art des matériaux magnétocaloriques existants. Dans le but d'obtenir des matériaux à forte capacité de réfrigération (RC) et d'identifier des stratégies d'amélioration de ce critère de performance, deux voies de recherche ont été explorées : l'élargissement de la transition magnétique et l'effet de l'élément de transition M et de l'élément p (X) dans les verres métalliques Gd60M30X10 (M = Mn, Fe, Co, Ni, Cu et X = Al, Ga, In) d'une part, et la synthèse de nouveaux siliciures ternaires dans les systèmes R-M-Si (R = Nd, Gd, Tb et M = Co, Ni) à fort potentiel magnétocalorique, d'autre part. Le second chapitre de cette thèse présente les propriétés magnétiques des rubans amorphes à base de gadolinium synthétisés par la technique de melt-spinning, dans lesquels le désordre structural induit un très fort élargissement de la transition magnétique (vis-à-vis de celle du gadolinium par exemple). Il montre dans un premier temps, la faible influence de l'élément p (X) sur les propriétés magnétiques des rubans Gd60Mn30X10 (X = Al, Ga, In). Une seconde partie présente la très forte influence de l'élément de transition M, tant sur la nature de la transition magnétique que sur les propriétés magnétocaloriques des verres métalliques Gd60M30In10 (M = Mn, Fe, Co, Ni, Cu), avec en particulier une température de Curie variant entre 86 (M = Ni) et 220 K (M = Fe) et l'existence d'un phénomène de type cluster-glass en dessous de 35 K lorsque M = Mn. Le chapitre trois de cette thèse se décline en trois parties. La première décrit les conditions de synthèse parfois délicates, notamment dans le choix des températures de recuit, des siliciures R5MSi2, Gd5Si3 et du composé à domaine d'existence Gd3Co2,5 ± xSi1,5 ± y. L'utilisation de la méthode Rietveld pour l'affinement des diffractogrammes de rayons X sur poudre et monocristaux et neutrons a permis de montrer que les composés R5MSi2 adoptent une structure de type Cr5B3 avec la particularité de l'occupation mixte du site 8h par Co et Si à 50 %/50 % et que Gd3Co2,5 ± xSi1,5 ± y adopte une structure de type Er3Ge4 avec des sites mixtes Co/Si en positions 4a et 4c. La seconde partie présente les propriétés magnétiques et magnétocaloriques du siliciure Gd5CoSi2. Ce composé subit une transition ferromagnétique à la température de Curie de 169 K qui s'accompagne d'une variation d'entropie magnétique calculée par l'application de la relation de Maxwell, de -4,7 et 8,7 J kg-1 K-1 pour des variations de champ magnétique respectives de 2 et 5 T. Le troisième volet de ce chapitre décrit les propriétés magnétiques de Nd5CoSi2 et Nd5NiSi2 qui présentent une transition ferromagnétique respectivement à 55 et 44 K. Il décrit également l'affinement de la structure ferromagnétique cantée de Nd5CoSi2 obtenue par des mesures de diffraction neutronique. Il ressort de ces travaux que l'évaluation des matériaux magnétocaloriques par le seul critère de capacité de réfrigération ne mène pas vers les matériaux les plus adaptés à l'application. Il faudrait cibler plus spécifiquement, pour chaque type de cycle de réfrigération envisagé, des critères pragmatiques tels qu'une fenêtre de température d'utilisation autour de la température de Curie ou une valeur de chaleur spécifique optimale afin de mieux guider la recherche de nouveaux matériaux magnétocaloriques.
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Gomes, Adriano de Araújo. "Algoritmo das projeções sucessivas para seleção de variáveis em calibração de segunda ordem." Universidade Federal da Paraíba, 2015. http://tede.biblioteca.ufpb.br:8080/handle/tede/8196.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this work it was developed a new strategy for intervals selection using the successive projections algorithm (SPA) coupled to N-PLS and U-PLS models, both with residual bilinearização (RBL) as a post-calibration step. The new algorithm coupled to N-PLS/RBL models was evaluated in two cases of studies. The first was simulated data for quantitation of two analytes (A and B) in the presence of a single interfering. On the second study was conducted a quantitation of ofloxacin in water in the presence of interferents (ciprofloxacin and danofloxacin) by means of liquid chromatography with diode array detection (LC-DAD) data modeling. The results were compared to the N-PLS/RBL model and the variables selection with the genetic algorithm (GA-N-PLS/RBL). In the first case of study (simulated data) were observed RMSEP values (x 10-3 in arbitrary units) for the analytes A and B in the order of 6.7 to 47.6; 10.6 to 11.4; and 6.0 to 14.0 for the N-PLS/RBL, Ga-N-PLS/RBL and the proposed method, respectively. On the second case of study (HPLC-DAD data) RMSEP value (mg/L) of 0.72 (N-PLS/RBL); 0.70 (GA-N-PLS/RBL) and 0.64 (iSPA N-PLS/RBL) were obtained. When combined with the U-PLS/RBL, the new algorithm was evaluated in the EEM modeling in the presence of inner filter effect. Simulated data and quantitation of phenylephrine in the presence of acetaminophen in water sample and interferences (ibuprofen and acetylsalicylic acid) were used as a case of studies. The results were compared to the U-PLS/RBL and e twell established method PARAFAC. For simulated data was observed the following RMSEP values (in arbitrary units) 1.584; 0.077 and 0.066 for PARAFAC; U-PLS/RBL and the proposed method, respectively. In the quantitation of phenylephrine the found RMSEP (in μg/L) were of 0.164 (PARAFAC); 0.089 (U-PLS/RBL) and 0.069 (ISPA-U-PLS/RBL). In all cases it was shown that variables selection is a useful tool capable of improving accuracy when compared with the respective global models (model without variables selection) leading to more parsimonious models. It was observed in all cases, that the sensitivity loss promoted by variables selection is compensated by using more selective channels, justifying the obtained RMSEP smaller values. Finally, it was also observed that the models based on variables selection such as the proposed method were free from significant bias at 95% confidence.
Neste trabalho foi desenvolvida uma nova estratégia para seleção de intervalos empregando o algoritmo das projeções sucessivas (SPA) acoplado a modelos N-PLS e U-PLS, ambos com etapa pós-calibração de bilinearização residual (RBL). O novo algoritmo acoplado a modelos N-PLS/RBL, foi avaliado em dois estudos de casos. O primeiro envolvendo dados simulados para quantificação de dois analitos (A e B) na presença de um único interferente. No segundo foi conduzida a quantificação de ofloxacina em água na presença de interferentes (ciprofloxacina e danofloxacina) por meio da modelagem de dados cromatografia liquida com detecção por arranjo de diodos (LC-DAD). Os resultados obtidos foram comparados ao modelo N-PLS/RBL e a seleção de variáveis com o algoritmo genético (GA-N-PLS/RBL). No primeiro estudo de caso (dados simulados) foram observados valores de RMSEP (x 10-3 em unidades arbitrárias) para os analitos A e B da ordem de 6,7 e 47,6; 10,6 e 11,4; 6,0 e 14,0 para o N-PLS/RBL, GA-N-PLS/RBL e o método proposto, respectivamente. No segundo estudo de caso (dados HPLC-DAD) valores de RMSEP (em mg/L) de 0,72 (N-PLS/RBL); 0,70 (GA-N-PLS/RBL) e 0,64 (iSPA-N-PLS/RBL) foram obtidos. Quando combinado com o U-PLS/RBL o novo algoritmo foi avaliado na modelagem de EEM em presença efeito de filtro interno. Dados simulados e a quantificação de fenilefrina na presença de paracetamol em amostras de água e interferentes (Ibuprofeno e ácido acetil salicílico) foram usados como estudos de caso. Os resultados obtidos foram comparados ao modelo U-PLS/RBL e ao bem estabelecido método PARAFAC. Para dados simulados foram observado os seguintes valores de RMSEP (em unidades arbitrarias) 1,584; 0,077 e 0,066 para o PARAFAC; U-PLS/RBL e método proposto, respectivamente. Na quantificação de fenilefrina os RMSEP (em μg/L) encontrados foram de 0,164 (PARAFAC); 0,089 (U-PLS/RBL) e 0,069 (iSPA-U-PLS/RBL). Em todos os casos foi demostrado que seleção de variáveis é uma ferramenta útil capaz de melhorar a acurácia quando comparados aos respectivos modelos globais (modelo sem seleção de variáveis) e tornar os modelos mais parcimoniosos. Foi observado ainda para todos os casos, que a perda de sensibilidade promovida pela seleção de variáveis é compensada pelo uso de canais mais seletivos, justificando os menores valores de RMSEP obtidos. E por fim, foi também observado que os modelos baseados em seleção de variáveis como o método proposto foram isentos de bias significativos a 95% de confiança.
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Wanklyn, Kevin Michael. "Experiments involving second order effects in high-intensity, high-frequency acoustic fields." Diss., Kansas State University, 2008. http://hdl.handle.net/2097/12200.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Sameer I. Madanshetty
Cavitation is a long studied phenomenon, fascinating and varied. Observed cavitation thresholds vary, typically ranging from the vapor pressure of the liquid to several atmospheres. Recent studies in cavitation involving very clean liquids give rise to thresholds that surpass 100 atmospheres. Calibrating such high intensity, high frequency, focused acoustic fields presents a significant challenge. The present investigation describes how it is possible to exploit the second order acoustic effect of radiation pressure to seek reliable calibration of the high intensity acoustic fields. Experiments describe how to account for the attendant second order effect of acoustic streaming in the evaluation of the radiation force to accomplish meaningful calibration. Beyond the measurement of the second order quantities associated with cavitation, the work also presents a first investigation of a direct estimation of implosion energies of collapsing bubbles near well-characterized surfaces.
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Ksianzou, Viachaslau. "Second-order nonlinear optical interactions and cascading effects in thinorganic films." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4918/.
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The presented work describes new concepts of fast switching elements based on principles of photonics. The waveguides working in visible and infra-red ranges are put in a basis of these elements. And as materials for manufacturing of waveguides the transparent polymers, dopped by molecules of the dyes possessing second order nonlinear-optical properties are proposed.
The work shows how nonlinear-optical processes in such structures can be implemented by electro-optical and opto-optical control circuit signals.
In this paper we consider the complete cycle of fabrication of several types of integral photonic elements. The theoretical analysis of high-intensity beam propagation in media with second-order optical nonlinearity is performed. Quantitative estimations of necessary conditions of occurrence of the nonlinear-optical phenomena of the second order taking into account properties of used materials are made.
The paper describes the various stages of manufacture of the basic structure of the integrated photonics: a planar waveguide. Using the finite element method the structure of the electromagnetic field inside the waveguide in different modes was analysed.
A separate part of the work deals with the creation of composite organic materials with high optical nonlinearity. Using the methods of quantum chemistry, the dependence of nonlinear properties of dye molecules from its structure were investigated in details. In addition, the paper discusses various methods of inducing of an optical nonlinearity in dye-doping of polymer films. In the work, for the first time is proposed the use of spatial modulation of nonlinear properties of waveguide according Fibonacci law. This allows involving several different nonlinear optical processes simultaneously.
The final part of the work describes various designs of integrated optical modulators and switches constructed of organic nonlinear optical waveguides. A practical design of the optical modulator based on Mach-Zehnder interferometer made by a photolithography on polymer film is presented.Die vorliegende Arbeit beschreibt neue Konzepte für schnelle photonische Schaltelemente. Diese Elemente basieren auf optischer Wellenleitung im sichtbaren und nahen infraroten Spektralbereich. Die Arbeit ist auf organische Wellenleiter aus transparenten, farbstoffdotierten Polymeren fokussiert, welche Chromophore mit besonders großen optischen Nichtlinearitäten zweiter Ordnung enthalten. Insbesondere wird dargestellt, wie nichtlineare optische Prozesse in derartigen Bauelementen genutzt werden können, wenn man elektrische oder optische Steuersignale einsetzt. Es wird der gesamte Her-stellungszyklus verschiedener integrierter photonischer Bauelemente betrachtet. Die Arbeit umfasst weiterhin eine detaillierte theoretische Analyse der Wellenausbreitung in Medien mit großer nichtlinearer optischer Suszeptibilität zweiter Ordnung bei hoher Lichtintensität. Unter Annahme optischer Materialkonstanten, welche den experimentell ermittelten Werten entsprechen, erfolgte eine quantitative Abschätzung für das Auftreten von Szenarien, bei denen messbare Abwei-chungen der Strahlausbreitung vom linearen Regime auftreten, z:B. das Auftreten von zeitlichen, räumlichen und spektralen Satteliten zu den im Material propagierenden Laserpulsen. Es gelang, we-sentliche Aspekte der Strahlpropagationsprozesse durch Anwendung von Jacobi-Integralfunktionen in geschlossener mathematischer Form darzustellen. Darüber hinausgehende theoretische Untersuchungen nutzten die Finite-Elemente-Methode, um die Verteilung des elektromagnetischen Feldes im Inneren optischer Wellenleiter für verschiedene Pro-pagationsmoden zu analysieren. Ein weiterer Teil der Arbeit beschäftigt sich mit organischen Kompositmaterialen, welche große opti-sche Nichtlinearitäten aufweisen. Mittels quantenchemischer Verfahren erfolgte eine detaillierte Un-tersuchung der Zusammenhänge zwischen der molekularen Struktur und den linearen sowie den nichtlinearen optischen Eigenschaften der untersuchten Farbstoffmoleküle und Polymere. In Bezug auf die Probenpräparation sind unterschiedliche Verfahren zur Schichtbildung und zur molekularen Orientierung miteinander verglichen und bewertet worden, da letztere eine Voraussetzung für das Auftreten nichtlinearer optischer Prozesse zweiter Ordnung bildet. Die Untersuchungen erstreckten sich auf Vakuumaufdampfschichten aus niedermolekularen Chromophoren und auf Polymerschich-ten, welche durch Vakuumabscheidung sowie durch Spincoating oder andere Flüssigphasenabschei-dungsverfahren hergestellt worden sind. Auf orientierenden Substraten (z.B. geriebene Schichten aus Polytetrafluoräthylen) konnte eine spontane Orientierung der deponierten Chromophore nachgewie-sen werden. Die Chromophore in Polymerschichten wurden durch Coronapolung orientiert. In der Arbeit ist zum ersten Mal vorgeschlagen worden, eine räumliche Modulation der nichtlinearen optischen Eigenschaften durch gezielte lokale Coronapolung oder andere Orientierungstechniken derart zu generieren, dass die Abfolge gepolter Domänen dem Bildungsgesetz einer modifizierten Fibonacci-Reihe mit gebrochen rationalen Zahlen gehorcht. Der Vorteil von optischen Wellenleitern mit dieser Struktur darin, dass diese mehrere unterschiedli-che nichtlineare optische Prozesse gleichzeitig unterstützen und somit eine Vielzahl neuartiger Phä-nomene auftreten kann, welche man in neuartigen photonischen Bauelementen, z.B. für die optische Informations- und Kommunikationstechnik nutzen kann. Der letzte Teil der Arbeit beschreibt den Aufbau verschiedener integrierter optischer Modulatoren und Schalter, die sich mit Hilfe das neu entwickelten Verfahrens herstellen lassen. Zukünftige Entwicklungen in der Photonik, insbesondere der optischen Informations- und Kommuni-kationstechnik werden im abschließenden Teil der Arbeit diskutiert.
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Yildirim, Ufuk. "Assessment Of Second-order Analysis Methods Presented In Design Codes." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610498/index.pdf.
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The main objective of the thesis is evaluating and comparing Second-Order Elastic Analysis
Methods defined in two different specifications, AISC 2005 and TS648 (1980). There are
many theoretical approaches that can provide exact solution for the problem. However,
approximate methods are still needed for design purposes. Simple formulations for code
applications were developed, and they are valid as acceptable results can be obtained within
admissible error limits. Within the content of the thesis, firstly background information
related to second-order effects will be presented. The emphasis will be on the definition of
geometric non-linearity, also called as P-δ
and P-&
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effects. In addition, the approximate methods defined in AISC 2005 (B1 &ndash
B2 Method), and TS648 (1980) will be discussed in detail. Then, example problems will be solved for the demonstration of theoretical formulations for members with and without end translation cases. Also, the results obtained from the structural analysis software, SAP2000, will be compared with the results acquired from the exact and the approximate methods. Finally, conclusions related to the study will be stated.
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Tikka, Timo K. "Examination of second-order effects in structural concrete columns and braced frames." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62673.pdf.
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Kurtz, Michael J. "Of Course a Handgun Can Take Down A Helicopter: Cultivation Effects of Military-Style Video Games." Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1336590515.
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Sorensen, Taylor J. "Reducing Thermal Bridging and Understanding Second-Order Effects in Concrete Sandwich Wall Panels." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7642.
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Structural engineers have traditionally detailed structures with structural and fabrication efficiency in mind, but often based on a limited understanding of thermal efficiency. Some connection designs can create significant thermal bridging, leading to unnecessary heat transfer and even premature degradation through condensation. Thermal bridging occurs when heat transfer is given a path through a more conductive material like concrete or steel rather than insulation. Concrete sandwich wall panels (SWP) tend to be highly efficient at preventing heat transfer in the middle of panels, with greatest heat transfer occurring at connections. This project identified thermally efficient details for future SWP construction to reduce heat transfer, lessen environmental impact, and increase sustainability of SWP structures. It can be particularly difficult to avoid thermal bridging at corbel connections, so 12 corbel specimens were created and tested to provide alternative corbel design options for engineers. Nine details were successfully created and are presented. Corbel specimens were modeled using the Beam-Spring Method with good agreement. After validating the Beam-Spring Model, a parametric study investigated effectiveness of the PCI Second Order Analysis and the effect of length, panel stiffness, and wythe configuration on SWP behavior under axial and flexural loads.
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Taylor, Mark Hedin. "The effects of industry specialization on auditors' inherent risk assessments and second-order uncertainty." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186854.
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A significant literature has developed which examines the relationship between auditors' expertise and their work experience. Much of the expertise paradigm literature centers on (1) whether a link between experience and task performance exists, and (2) describing the nature of the cognitive changes associated with the link. A significant, but largely unresearched component of this link is the impact of auditors' industry specialization on audit judgment. Industry specialization is currently receiving considerable attention from practitioners and academics alike. This paper examines the effects of industry specialization on auditors' inherent risk (IR) assessments, and on auditors' uncertainty in specifying such assessments. For several constructed audit cases, two groups of auditors (banking specialists and nonbanking specialists, both with approximately the same amount of CPA firm auditing tenure) from a "big-six" accounting firm were requested to provide planning-stage IR assessments and related second-order uncertainty (SOU) assessments. The results support several conclusions. First, consistent with the notion that industry experience facilitates the development of an industry-distinct knowledge base pertinent to IR assessment and that auditors who lack such experience lack such knowledge, nonspecialists experienced significantly more uncertainty about their IR assessments, relative to specialists. This result was observed for IR assessments pertinent not only to the loans account, but also to the premises and equipment (P&E) account, although the effect was not as pronounced for the P&E account which has a more similar analog in most other types of clients. Second, and also consistent with the notion that specialized experience leads to the development of specific knowledge pertinent to the risk assessment task, nonspecialists' IR assessments were generally significantly higher for a financial statement account unique to the industry--than industry specialists' IR assessments, indicating a conservative bias when industry knowledge is lacking. This result has potentially important implications regarding audit testing; given that IR assessments determine, at least in part, the extent of audit testing, it implies-holding all else constant--that the nonbanking group would be significantly more inefficient relative to the banking group in terms of audit effort expended in audit sampling. An example illustrates that the nonbanking group's risk assessments resulted in hypothetical samples sizes for the completeness assertion for the loans account (using the participating firm's sample size algorithm) that were on average J.2 percent larger than the banking group's, holding all else constant (t = 9.02, P < .01). Clearly this result has implications for audit policy; it indicates that specialization may provide some economy in the audit. This result helps to explain the trend toward industry specialization in general. Third, consistent with the notion that common experience standardizes knowledge bases pertinent to IR assessments, specialists exhibited significantly more consensus in their IR assessments for an account unique to banking clients. Nonspecialists and specialists exhibited similar levels of IR assessment consensus for an account common to most audits. Relatedly, the variance in uncertainty about IR assessments was significantly smaller for industry specialists. This result supports the assertion that common experience standardizes knowledge bases pertinent to IR assessments and reduces individual differences in perceptions about the adequacy of knowledge bases which support IR assessments. Given the results of the study, further investigation is warranted regarding questions about the effects of specialization on audit judgment. The findings presented have not been documented previously, and add to the literature on expertise in auditing. Several other avenues of research are advocated including additional questions about the effects of industry specialization on audit judgment. Addressing these issues may lead to further refinements in models of auditor expertise and serve to advance the literature and practice policy regarding industry specialization.
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Du, Chenguang. "How Well Can Two-Wave Models Recover the Three-Wave Second Order Latent Model Parameters?" Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103856.
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Although previous studies on structural equation modeling (SEM) have indicated that the
second-order latent growth model (SOLGM) is a more appropriate approach to
longitudinal intervention effects, its application still requires researchers to collect at least
three-wave data (e.g. randomized pretest, posttest, and follow-up design). However, in
some circumstances, researchers can only collect two-wave data for resource limitations.
With only two-wave data, the SOLGM can not be identified and researchers often choose
alternative SEM models to fit two-wave data. Recent studies show that the two-wave
longitudinal common factor model (2W-LCFM) and latent change score model
(2W-LCSM) can perform well for comparing latent change between groups. However, there
still lacks empirical evidence about how accurately these two-wave models can estimate the
group effects of latent change obtained by three-wave SOLGM (3W-SOLGM). The main
purpose of this dissertation, therefore, is trying to examine to what extent the fixed effects
of the tree-wave SOLGM can be recovered from the parameter estimates of the two-wave
LCFM and LCSM given different simulation conditions.
Fundamentally, the supplementary study (study 2) using three-wave LCFM was
established to help justify the logistics of different model comparisons in our main study
(study 1). The data generating model in both studies is 3W-SOLGM and there are in total
5 simulation factors (sample size, group differences in intercept and slope, the covariance
between the slope and intercept, size of time-specific residual, change the pattern of
time-specific residual). Three main types of evaluation indices were used to assess the
quality of estimation (bias/relative bias, standard error, and power/type I error rate). The
results in the supplementary study show that the performance of 3W-LCFM and
3W-LCSM are equivalent, which further justifies the different models' comparison in the
main study. The point estimates for the fixed effect parameters obtained from the two-wave
models are unbiased or identical to the ones from the three-wave model. However, using
two-wave models could reduce the estimation precision and statistical power when the
time-specific residual variance is large and changing pattern is heteroscedastic
(non-constant). Finally, two real datasets were used to illustrate the simulation resultsDoctor of Philosophy
To collect and analyze the longitudinal data is a very important approach to understand the phenomenon of development in the real world. Ideally, researchers who are interested in using a longitudinal framework would prefer collecting data at more than two points in time because it can provide a deeper understanding of the developmental processes. However, in real scenarios, data may only be collected at two-time points. With only two-wave data, the second-order latent growth model (SOLGM) could not be used. The current dissertation compared the performance of two-wave models (longitudinal common factor model and latent change score model) with the three-wave SOLGM in order to better understand how the estimation quality of two-wave models could be comparable to the tree-wave model. The results show that on average, the estimation from two-wave models is identical to the ones from the three-wave model. So in real data analysis with only one sample, the point estimate by two-wave models should be very closed to that of the three-wave model. But this estimation may not be as accurate as it is obtained by the three-wave model when the latent variable has large variability in the first or last time point. This latent variable is more likely to exist as a statelike construct in the real world. Therefore, the current study could provide a reference framework for substantial researchers who could only have access to two-wave data but are still interested in estimating the growth effect that supposed to obtain by three-wave SOLGM.
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Bullock, Christopher. "Second-order schedules of token reinforcement combined effects of token-production and exchange-schedule manipulations /." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000654.
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Petkoglou, Alexandros. "Stability of building structures using NLFEA including second order effects : Applications with the software ATENA-GiD." Thesis, KTH, Betongbyggnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302435.
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In Sweden, prefabrication in the construction industry is a very common system. In prefabricated structures, there are various kinds of connections and generally many hinged connections. Therefore, it is of high interest to study the behavior of the prefabricated buildings in relation to the connections. Two main theories that can be used to evaluate our structures are the non-linear finite element analysis (NLFEA) and the second order effects. These two theories help to study the real behavior of the structures. Software that can apply these two theories is the ATENA-GiD. Therefore, it was very interesting to explore this software and find out how it can be used for prefabricated buildings. For this reason, a simplified ten-storey building was studied which had been also used in Lindwall’s and Wester’s (2016) master thesis. Various cases were chosen for this building. The building was studied either with monolithic walls or with vertical slip connection between the prefabricated walls. Also, the hollow core (HC) slabs were modelled in two ways and the supports of the columns were modelled in three ways. Even when each slab was modelled with two materials (solid concrete for the upper and lower layer with smeared reinforcement for the lower layer and modified concrete in order to compensate for the voids), the increase in the time for analysis was not important. Also, the cracking was not extensive thanks to the relatively low wind load. The slip joint between the walls didn’t lead to the different displacement between the walls. It was found that the hinged support in the columns was modelled by using the upwind line of the base. In non-linear analysis cases, the model of the structure gave 20% larger displacements than in linear analysis cases which means that the cracking had an important influence on the second order effects despite that the cracking was not extensive. The reduction of the stiffness of the walls to 40% accounting for cracked sections in additional linear analyses to according to the Eurocode 2 was a conservative choice for this building. The most remarkable result was that when the supports of the columns were modelled with hinges there was smaller displacement than when the supports were fixed. The reason for this was the negative displacements due to the buckling of the columns of the first storey. Moreover, for the linear cases, there was a much smaller displacement (5mm) than Lindwall and Wester (2016) (17mm) and this was possibly due to the way that the hinges were modelled in my building. It is interesting to investigate other ways to model the hinges in ATENA-GiD as well as other ways to model the connections between the HC slabs and the perimetric beams. Also, the effect of creep through the modulus of elasticity could be analyzed. Finally, it would be interesting to include foundations in the model to study the possible need for anchorages.
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Wang, Xiaorui. "Decomposing the Growth of US Wine Exports to China into Scale, Competitive, and Second-order Effects." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1598.
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The study aims at investigating the reason for the growth of US wine exports to China through utilizing CMS (Constant Market Share Analysis) model decomposed into three effects: scale, competitive and second-order effect. The result shows that the increasing demand of Chinese market is the key factor for the growth of US wine exports to China; at the same time, it also indicates that the product competitiveness of US wine is declining, while market distribution channels are lacking. The phenomenon of the increase of Chinese market for importing American wine can be attributed to the growing Chinese wine market, the growth of economy in China and the increasing income of Chinese people, as well as the trade policy after China joining in WTO.
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BAREIRO, WALTER GABRIEL. "STUDY AND MODELING OF TRUSSES STRUCTURES USED IN INDUSTRIAL BUILDINGS CONSIDERING INITIAL IMPERFECTIONS AND SECOND ORDER EFFECTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26671@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Os galpões industriais constituem um dos segmentos da construção em aço mais comuns no mercado brasileiro. As características na construção são rapidez de execução, menor volume de material e a esbeltez dos elementos. Nesta dissertação avalia-se o desempenho e a necessidade da consideração das imperfeições iniciais e dos efeitos de segunda ordem nas estruturas treliçadas usuais nos galpões. Através da modelagem de um conjunto de pórticos treliçados realiza-se um estudo paramétrico das diferentes tipologias e busca-se oferecer uma solução prática de pré-dimensionamento. Realiza-se a comparação entre as metodologias de análises de segunda ordem: o método simplificado MAES da ABNT NBR 8800:2008 e a análise avançada efetuada no programa Autodesk Robot Structural Analysis Professional. Os resultados obtidos mostraram a consistência entre as metodologias de análises de segunda ordem. A partir estudo comparativo entre a análise de primeira ordem e a análise de segunda ordem conclui-se sobre a pequena influência dos efeitos de segunda ordem neste tipo de sistemas treliçados. Comprova-se a pouca sensibilidade à incorporação das imperfeições geométricas iniciais. Obtêm-se os gráficos de consumo aproximado de aço e de deslocamentos máximos. Para as diferentes soluções estruturais observa-se a incidência das tipologias das treliças no desempenho estrutural em relação aos deslocamentos máximos. Apresenta-se um procedimento simplificado de pré-dimensionamento mediante tabelas e ábacos produzidos para as diversas treliças.
The industrials buildings are one of the segments of construction in most common steel in Brazil. The features in construction are rapidity of execution, a smaller volume of material and slenderness of de elements. In this dissertation evaluates the performance and the need consideration of initial imperfections and second order effects in the usual trusses structures in the sheds. Through modeling a set of trusses frames is carried out a parametric study of various types and seeks to provide a practical solution of pre-design. It carried out a comparison between the methodologies of second-order analysis: The simplified method MAES of the ABNT NBR 8800:2008 and the advanced analysis made in Autodesk Robot Structural Analysis Professional program. The result showed consistency between the methodologies of and order analysis. From a comparative study of the analysis of 1st order and 2nd order analysis is concluded on the small influence of 2nd order effects in this type of trusses systems. Proves to little sensitivity to the incorporation of initial geometric imperfections. They obtain the graphs of estimated consumption of steel and maximum displacements. For different structural solutions observes the incidence of types of trusses in the structural performance of maximum displacement. It presents a simplified procedure for preliminary design through tables and abacuses produced for different trusses.
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Fritsch, Gerd. "An analytical and numerical study of the second-order effects of unsteadiness on the performance of turbomachines." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/42703.
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Alamry, Ali. "Grammatical Gender Processing in Standard Arabic as a First and a Second Language." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39965.
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The present dissertation investigates grammatical gender representation and processing in Modern Standard Arabic (MSA) as a first (L1) and a second (L2) language. It mainly examines whether L2 can process gender agreement in a native-like manner, and the extent to which L2 processing is influenced by the properties of the L2 speakers’ L1. Additionally, it examines whether L2 gender agreement processing is influenced by noun animacy (animate and inanimate) and word order (verb-subject and subject-verb). A series of experiments using both online and offline techniques were conducted to address these questions. In all of the experiments, gender agreement between verb and nouns was examined. The first series of experiments examined native speakers of MSA (n=49) using a self-paced reading task (SPR), an event-related potential (ERP) experiment, and a grammaticality judgment (GJ) task. Results of these experiments revealed that native speakers were sensitive to grammatical violations. Native speakers showed longer reaction times (RT) in the SPR task, and a P600 effect in the ERP, in responses to sentences with mismatched gender agreement as compared to sentences with matched gender agreement. They also performed at ceiling in the GJ task. The second series of experiments examined L2 speakers of MSA (n=74) using an SPR task, and a GJ task. Both experiments included adult L2 speakers whom were divided into two subgroups, -Gender and +Gender, based on whether or not their L1s has a grammatical gender system. The results of both experiments revealed that both groups were sensitive to gender agreement violations. The L2 speakers showed longer RTs, in the SPR task, in responses to sentences with mismatched gender agreement as compared to sentences with matched gender agreement. No difference was found between the L2 groups in this task. The L2 speakers also performed well in the GJ task, as they were able to correctly identify the grammatical and ungrammatical sentences. Interestingly in this task, the -Gender group outperformed +Gender group, which could be due to proficiency in the L2 as the former group obtained a better score on the proficiency task, or it could be that +Gender group showed negative transfer from their L1s. Based on the results of these two experiments, this dissertation argues that late L2 speakers are not restricted to their L1 grammar, and thus, they are able to acquire gender agreement system of their L2 even if this feature is not instantiated in their L1. The results provide converging evidence for the FTFA rather than FFFH model, as it appears that the -Gender group was able to reset their L1 gender parameter according to the L2 gender values. Although the L2 speakers were advanced, they showed slower RTs than the native speakers in the SPR task, and lower accuracy in the GJT. However, it is possible that they are still in the process of acquiring gender agreement of MSA and have not reached their final stage of acquisition. This is supported by the fact that some L2 speakers from both -Gender and +Gender groups performed as well as native speakers in both SPR and GJ tasks. Regarding the effect of animacy, the L2 speakers had slower RT and lower accuracy on sentences with inanimate nouns than on those with animate ones, which is in line with previous L2 studies (Anton-Medez, 1999; Alarcón, 2009; Gelin, & Bugaiska, 2014). The native speakers, on the other hand, showed no effect of animacy in both SPR task and GJT. Further, no N400 effect was observed as a result of semantic gender agreement violations in the ERP experiment. Finally, the results revealed a potential effect of word order. Both the native and L2 speakers showed longer RTs on VS word order than SV word order in the SPR task. Further the native speakers showed earlier and greater P600 effect on VS word order than SV word order in the ERP. This result suggests that processing gender agreement violation is more complex in the VS word order than in the SV word order due to the inherent asymmetry in the subject-verb agreement system in the two-word orders in MSA.
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Street, Michael William. "Quantum well intermixing for the control of second order non-linear effects in GaAs/AlGaAs asymmetric quantum well waveguides." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/4326/.
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QW-intermixing was accomplished for several different multiple AQW structures using impurity-free vacancy disordering (IFVD). Unphase-matched second harmonic generation (SHG) experiments were subsequently performed with waveguides fabricated from as-grown and intermixed AQW material. No conclusive evidence was found for the existence of any AQW tensor components. This is consistent with recent calculations which predict, that for the particular AQW structures studied, the AQW non-linearities are negligible. Unphase-matched SHG was, however, observed which was attributable to the large bulk GaAs/AlGaAs d14 coefficient. Furthermore, d14 was reduced by 17% on intermixing. Since the quasi-phase-matching conversion efficiency is proportional to both the square of the magnitude of the non-linearity and the square of the modulation depth, a small but significant reduction in the large d14 coefficient such as this, could lead to useful conversion efficiencies. Selective-area IFVD was achieved using hydrogen plasma processing to inhibit intermixing. Only partial suppression of the IFVD process was, however, achieved. The spatial resolution of the selective-area process was measured for two different MQW structures under different annealing conditions, and was found to be better than 2.2 m. The resolution of the IFVD process is therefore sufficiently good for the control of second order non-linear interactions in GaAs/AlGaAs MQW waveguides. Periodically-intermixed waveguides were fabricated for quasi-phase-matching. These waveguides had measured losses ranging between 3.7 dB/cm and 18 dB/cm depending on the intermixing period. Phase-matching was not, however, observed in these devices. This may have been a consequence of one of several factors including, non-ideal laser tuning characteristics, the use of inaccurate intermixing periods, and a negligible modulation depth in d14. Further work is therefore necessary to establish why phase-matching was not achieved, and to improve the selective-area intermixing process. If these difficulties can be overcome and, in addition, an AQW structure can be designed with associated significant non-linearities, then SHG conversion efficiencies of several hundred %/Wcm2 may be possible.
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Nguyen, Thuy Thi My. "Development of a second-order inelastic analysis method accounted for construction stage effects on the behaviour of prestressed steel structures." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/117967/8/Thi_Nguyen_Thesis.pdf.
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This research developed a new method to investigate the construction stage effects on the behavior of pre-stressed steel structures. Any changes of structural geometry and/or material properties are properly accounted and evaluated stage-by-stage during the whole construction. Therefore, the structural responses are properly predicted. Any instability and excessive deflection of structural members or the possibility of structural collapse during construction can be avoided.
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Carmo, Regina Maria dos Santos. "Efeitos de segunda ordem em edifícios usuais de concreto armado." Universidade de São Paulo, 1995. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-24042018-120327/.
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Neste trabalho são estudados os parâmetros de verificação do estado limite de deformações excessivas (a relação flecha-altura-a/H) e da estabilidade global (o parâmetro α e o coeficiente γz) das estruturas de edifícios. Através da utilização de exemplos de estruturas de trinta (30) edifícios usuais de concreto armado, estabelece-se uma relação entre esses parâmetros, objetivando propiciar ao projetista de estruturas condições de avaliar a eficiência e o grau de confiabilidade de cada um deles. São também discutidos e comparados alguns dos procedimentos usuais para realizar uma análise global de segunda ordem das estruturas. Nesta análise deve-se levar em conta tanto a não-linearidade física (NLF) quanto a geométrica (NLG) e, para tanto, são adotados métodos rigorosos e aproximados. Quer-se com isso, principalmente, analisar o processo simplificado como suficiente para se obter os esforços finais de segunda ordem, uma vez que se pretende incluir tal procedimento na norma brasileira NB-1, atualmente em fase de revisão.In this work, a servicebility pararneter (displacement-height ratio - a/H) is studied, as well as the global stability parameters of building structures (α and γz stability coefficients). By analyzing thirty (30) actual reinforced concrete building structures, a relationship among these parameters (α, γz and a/H) is achieved aiming to demonstrate to the building structure designers their level of efficiency and reliability for practical purposes. Some standard procedures for global second order structure analysis are also discussed with comparison among them. In this analysis, the material and the geometric non-linearities have to be considered and for that one can adopt approximated and accureted methods. Mainly, the interest is to verify the possibility of using the simplified method as a proper tool to compute the final second order efforts of buildings, once this procedure could be included into the Brazilian Code, NB-1, which is being revised.
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Quillin, Michael J. "Are We Going In There? The Role of Brief Narratives (TV ADs and PSAs) in Narrative Transportation and Second-Order Cultivation Effects." Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1418637369.
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Long, Kelsey B., Kelsey C. Rookstool, Lauren P. Driggers-Jones, and Wallace Jr Dixon. "Effects of Birth Order on Temperament and Language." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/210.
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Previous research has shown temperament to be stable throughout development and this effect remains when controlling for infant birth order. However, to our knowledge, there have been no investigations examining the direct relationship between temperament characteristics and birth order within the family. Because infant temperament has been shown to be related to maternal stress during pregnancy it stands to reason that mothers caring for multiple children while pregnant will experience more stress, and thus affect the temperament of their gestating offspring. Therefore, the first aim of the present investigation was to evaluate whether birth order was associated with infant temperament. Additionally, research has shown relationships between birth order and language; with second born children showing a significant advancement of language skills compared to first born children. However, no studies have investigated the relationship between birth order and gestural abilities. Because gestural abilities significantly predict language development, it stands to reason that birth order should also affect the gestural abilities of infants. Thus, the second aim of the current project was to evaluate the relationship between birth order and gestural abilities. Eighty-three children visited the lab at M = 15.45 months. Caregivers completed the Infant Behavioral Questionnaire-Revised (IBQ-R), the MacArthur-Bates Communicative Development Inventory:Words and Gestures (MCDI-WG), and a demographic questionnaire concerning family size and birth order. In line with our first aim, we evaluated correlations between infant temperament and birth order. These analyses revealed a significant relationship between the temperamental superdimension of negative affectivity; specifically, the subdimension of sadness was the main factor driving the relationship between birth order and temperament. Next, to investigate whether birth order was related to gestural abilities, we analyzed correlations between birth order and the MCDI-WG categories of performing actions with objects, as well as imitation. This analysis revealed significant associations between birth order and both gestural categories. While these results were in line with our expectations, they remain to be supported by replication. However, should these results withstand tests of replication, they suggest interesting findings for both temperament and language research. First, these results suggest that later born children are at risk for a difficult temperament; however, the specific cause of this relationship is unknown, but could include prenatal stress, or stress during infancy such as less time spent with caregivers. Secondly, these results suggest that later born children are at a particular advantage. This advantage may be due to the fact that later born children, by virtue of their larger families, have a greater number of exemplars from which to learn gestures through observation.
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Ningre, Corado. "Modélisation du comportement élastoplastique cyclique multiaxial par une approche multisurface dans l'espace des déformations." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI053.
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Ce travail concerne l’étude théorique, numérique et expérimentale du comportement mécanique élastoplastique en chargements cycliques complexes multiaxiaux de matériaux métalliques. Le comportement élastoplastique est décrit par modèle multisurface, avec une prise en compte des grandes transformations. Ce modèle est écrit dans l’espace multidimensionnel d’Ilyushin des déformations, de dimension 5. La modélisation qui en résulte permet de décrire le comportement multiaxial des matériaux métalliques, en chargements cycliques complexes, notamment non proportionnels, avec une prise en compte des déformations finies, de l’irréversibilité indépendante du temps, des effets secondaires cumulés (effet Poynting-Swift) et des effets d’écrouissage cyclique. Le modèle ainsi développé a été implémenté dans un code commercial de calcul par éléments finis, afin de produire un outil opérationnel de calcul des structures telles que les équipements mécaniques et les composants internes des centrales hydroélectriques (turbines, alternateur…). Le modèle proposé a été validé par confrontation à des résultats d’essais biaxiaux de traction-torsion combinées, réalisés sur un acier inoxydable. Ce modèle a été complété par une analyse énergétique et thermodynamique qui permet la mise en place, à terme, d’une approche énergétique pertinente pour le suivi de l’endommagement par fatigue. Dans le cadre de ce travail, cette approche a été illustrée par la proposition d’un critère de fatigue, validé par la comparaison de ses prédictions à celles d’autres critères de fatigue classiques, proposés dans la littératureThis work deals with the theoretical, numerical and experimental study of the elastoplastic mechanical behavior of metallic materials in complex multiaxial cyclic loadings. The elastoplastic behavior is described by a multisurface model, within the finite strain theory. This model is written in the five-dimensional Ilyushin strain space. The resulting model is capable of describing the multiaxial behavior of metallic materials, in complex cyclic loadings, in particular non-proportional, taking into account finite strain, time-independent irreversibility, cumulative second order effects (Poynting-Swift effect) and cyclic hardening. The model has been implemented in a commercial finite element calculation code, in order to produce an operational tool for calculating structures such as mechanical equipment and internal components of hydroelectric power plants (turbines, alternators, etc.). The proposed model was validated by comparison with combined tensile-torsion biaxial test results obtained on stainless steel. This model has been completed by an energy and thermodynamic analysis that allows the implementation of a relevant energy approach for the monitoring of fatigue damage. As part of this work, this approach was illustrated by the proposal of a fatigue criterion, validated by the comparison of its predictions with those of other classical fatigue criteria proposed in the literature
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Mercier, Charlotte. "Développement d’un modèle de stabilité des barres à section tubulaire comprimées fléchies sensibles aux effets du second ordre." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0113/document.
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Cette thèse s’inscrit dans une démarche d’amélioration des connaissances des instabilités des éléments comprimés et fléchis sensibles aux effets du second ordre. Il s’agit de traiter la prise en compte des imperfections initiales dans l’analyse de la structure et d’adapter les critères actuels de vérification pour les structures tubulaires de type échafaudage. Les formulations existantes, proposées dans la littérature et les codes de calculs, sont souvent issues d’hypothèses, et conduisent à des incohérences entre les critères de vérification en section, et les critères de vérification en instabilité. L’approche développée traite l’interaction entre la résistance en section et les phénomènes d’instabilités, et inclut l’influence des imperfections initiales. Ces effets seront, dans la mesure du possible, découplés. À ce titre, une méthode a été conçue pour permettre la définition des imperfections initiales d’une structure, de manière à être la plus précise possible. Cette méthode, basée sur la définition d’une imperfection unique, d’allure identique à la déformée critique du mode de flambement prépondérant, est une méthode précise, entièrement définie permettant de tenir compte des caractéristiques géométriques, des caractéristiques mécaniques intrinsèques, des conditions aux limites et de la forme du chargement, dans la définition de l’imperfection initiale unique d’une structure. Une campagne d’essai a été réalisée en collaboration avec le SFECE, visant à analyser le comportement expérimental au flambement de sections tubulaires formées à froid. Des essais de flambement sur des échelles d’échafaudage, provenant de divers fournisseurs européens, ont été effectués. Une étude statistique des résultats expérimentaux a permis de mettre en évidence que le facteur d’imperfection actuellement défini pour les sections tubulaires formées à froid est bien trop pénalisant à l’égard des sections usitées dans le domaine des échafaudages. Afin de répondre à la problématique, de nouveaux critères de vérification en instabilité ont également été établis en utilisant une approche similaire à celle d’Ayrton-Perry. Ces nouveaux critères permettent de s’affranchir de la modélisation des imperfections initiales tout en offrant une estimation sûre et précise du facteur de sollicitation d’une structure. Des études comparatives ont été menées de manière à s’assurer de la sécurité des formulations proposées par rapport aux critères de vérification en section de la norme actuelleThis thesis is part of an effort to improve knowledge of the instabilities of beam-columns sensitive to second-order effects. The works deal with the means to take into account the initial imperfections in the structural analysis and to adapt the current verification criteria for tubular section structures, such as scaffold structures. The existing formulations, proposed in the literature and calculation codes, are often based on hypotheses, and thus lead to inconsistencies between, on the one hand, the verification criteria in section, and on the other hand, the verification criteria in instability. The developed approach takes into account the interaction between section resistance and instability phenomena, and includes the influence of initial imperfections (initial defect of aplomb, lack of straightness, residual stresses). As far as possible, these effects will be decoupled. As such, a method has been developed to allow the definition of initial imperfections of a structure, to be as accurate as possible. This method, based on the definition of a single imperfection, identical in appearance to the shape of the predominant critical buckling mode, is a precise, fully defined method to take into account the geometric characteristics, intrinsic mechanical characteristics, limits and the form of loading, in the definition of the initial imperfections of a structure. A test campaign was carried out in collaboration with the French Syndicate of Scaffolding, Formwork and Shoring (SFECE), aiming to analyze the experimental behavior of buckling of cold-formed tubular sections. Nine buckling tests on scaffold ladders, from various European suppliers, have been carried out. A statistical study of the experimental results has made it possible to highlight that the imperfection factor currently defined for the cold-formed tubular sections is far too penalizing for the sections used in the field of scaffolds. In order to respond to the problem, new instability criteria have also been established using a similar approach to that of Ayrton-Perry. These new criteria make it possible to free ourselves from the modeling of initial imperfections while offering a safe and accurate estimate of the stress factor of a structure. A comparative study was conducted in order to ensure the safety of the proposed formulations as regards the section verification criteria of the NF EN 1993-1-1 current standard
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Nassiri, Esmail. "Modelling nonlinear behaviour of two-dimensional steel structures subjected to cyclic loading." Thesis, Queensland University of Technology, 1998.
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Börjesson, Rivera Miriam. "Practice makes perfect? : Sustainable practices with ICT and daily travel." Licentiate thesis, KTH, Miljöstrategisk analys (fms), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175753.
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The thesis shows how practice theory can be applied in different ways when exploring how daily life can be supported to become more environmentally sustainable. Ultimately the thesis aims to contribute to new knowledge on how to design policies and interventions that aim at facilitating environmentally sustainable practices. This thesis argues that practice theory is useful in the field of sustainability research since it offers as point of departure a perspective on human everyday life which decentres focus from individual behaviour and instead looks at how social practices are constructed by integrating and combining material, bodily and mental elements. The thesis discusses the following questions: i) How can the role of ICT in everyday life be conceptualized from a practice perspective?, ii) How can practice theory be used in order to describe and assess second order environmental effects? and iii) What are the key considerations from a practice perspective when designing social/physical interventions for sustainable mobility? The papers in this thesis all use practice theory as point of departure but with different outcomes. Practice theory is thus used conceptually, methodologically and analytically. The main conclusions of the thesis are: Changes in practices due to ICT usage will inevitably have environmental impacts, both negative and positive, and for policy-makers it is imperative to take this into consideration when planning for the future and actively support and facilitate sustainable social practices. Looking at changes in practices due to new ICT usage can be one way to include second order effects in environmental assessments, in this way contributing to a discussion of potential environmental impacts from implementing a new product, application or service. Interventions, such as a cargo bike pool or restrictive work travel policies, have the potential to change existing practices. However, the potential of these changes, depend on a variety of different factors which are more or less difficult to influence for the individual practitioner such as work location, time schedules, availability of transportation means and modes. Further, it is difficult to foresee exactly how such changes will look and if they sustain in the long run. Finally, it is not necessarily so that an intervention will have the desired outcome that was intended, the outcome might be something else, consequently this means that interventions need to be analysed and assessed from other perspectives, one being a practice perspective.Denna avhandling visar hur praktikteori (practice theory) kan tillämpas på olika sätt när man ska utforska hur det dagliga livet kan bli mer miljömässigt hållbart. Ytterst syftar avhandlingen till att bidra till ny kunskap om hur man kan utforma strategier och åtgärder som syftar till att stödja miljömässigt hållbara praktiker. Denna avhandling hävdar att praktikteori är användbart inom hållbarhetsforskning eftersom den utgår från de vardagliga praktikerna. Detta ger ett perspektiv på människors vardagsliv som lyfter fokus upp från individens beteende och istället undersöker hur praktiker skapas och omskapas genom de element (material, färdigheter och symbolisk innebörd) som utgör en social praktik. Avhandlingen behandlar följande frågor: i) Hur kan IKT: s roll i det dagliga livet begreppsliggöras?, ii) Hur kan praktikteori användas för att beskriva och andra ordningens miljöeffekter i miljöbedömningar? och iii) Vilka är de viktigaste överväganden utifrån ett praktikteoriperspektiv vid utformningen av sociala och/eller fysiska åtgärder för hållbar mobilitet? Artiklarna i denna avhandling utgår från praktikteori, men det teoretiska ramverket används på ett konceptuellt, metodologiskt eller analytiskt vis i de olika artiklarna. De viktigaste slutsatserna i avhandlingen är: Förändringar i till följd av IKT-användning kommer oundvikligen ha miljöpåverkan som kan vara både negativ och positiv. För beslutsfattare är det viktigt att ta hänsyn till detta när man planerar för framtiden och aktivt stödja och underlätta för hållbara sociala praktiker. Miljöbedömningar behöver kunna hantera och inkludera så kallade effekter av andra ordningen för att kunna bedöma potentiell miljöpåverkan som en ny produkt, program eller en tjänst kan ha. Ett sätt att inkludera andra ordningens effekter i miljöbedömningar kan vara att titta på förändringar i vardagliga praktiker som uppstår vid användning av IKT. Interventioner och andra typer av åtgärder har potential att förändra befintliga mobilitetspraktiker. Men dessa potentiella förändringar, beror på en rad olika faktorer som är mer eller mindre svårt att påverka för den enskilde utövaren så som arbetsplatsens lokalisering, scheman, tillgång till transportmedel och transportsätt. Vidare är det svårt att förutse exakt hur sådana förändringar kommer att se ut och om de håller i sig i det långa loppet. Slutligen är det inte nödvändigtvis så att en intervention eller annan åtgärd kommer att ha det önskade resultatet som avsågs, utan resultatet kan snarare vara något annat. Detta innebär att insatser och åtgärder måste analyseras och bedömas ur andra perspektiv, till exempel ett praktikteoretiskt perspektiv.
QC 20151023
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Lima, Juliana Soares. "Verificações da punção e da estabilidade global em edifícios de concreto: desenvolvimento e aplicação de recomendações normativas." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-12082016-121356/.
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Neste trabalho, são estudas as verificações da punção global segundo a revisão da NBR 6118. A partir da análise dos fenômenos físicos e com base nos estudos teóricos realizados, são feitas sugestões para serem contornadas algumas omissões da Norma. Também são propostas complementação que facilitem o entendimento das novas recomendações e, ainda, modificações que melhorem seus resultados. Sugerem-se métodos simplificados relacionados à punção excêntrica, e propõem-se algumas alterações quanto ao uso do γz como coeficiente majorador na avaliação da estabilidade global. Observa-se que as verificações, apesar de mais trabalhosas, apresentam melhorias significativas em relação à NBR 6118 (1978), mostrando-se mais detalhadas e eficientes. Ainda assim, considera-se importante a introdução de algumas complementações, como aquelas sugeridas neste trabalho.This work presents an overview of the requirements for punching shear and global stability of buildings in the draft Brazilian Code for concrete structures. Suggestions are made for fulfilling some omissions of the Code, based on theoretical studies and physical phenomena analysis. Some complements and changes are also proposed to facilitate the understanding of the new recommendations and to improve their results. Simplified methods related to the eccentric punching and modifications in the use of γz as a first order effects magnifier are suggested. It is concluded that the new provisions are more detailed and efficient, presenting significant improvements on both topics, especially when compared to NBR 6118 (1978). Nevertheless, it is considered important the introduction of some complements, as those suggested in this work.
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Muduli, Pranaba Kishor. "Ferromagnetic thin films of Fe and Fe 3 Si on low-symmetric GaAs(113)A substrates." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15473.
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In dieser Arbeit werden das Wachstum mittels Molekularstrahlepitaxie und die Eigenschaften der Ferromagneten Fe und Fe_3Si auf niedrig-symmetirschen GaAs(113)A-Substraten studiert. Drei wichtige Aspekte werden untersucht: (i) Wachstum und strukturelle Charakterisierung, (ii) magnetische Eigenschaften und (iii) Magnetotransporteigenschaften der Fe und Fe_3Si Schichten auf GaAs(113)A-Substraten. Das Wachstum der Fe- und Fe_3Si-Schichten wurde bei einer Wachstumstemperatur von = bzw. 250 °C optimiert. Bei diesen Wachstumstemperaturen zeigen die Schichten eine hohe Kristallperfektion und glatte Grenz- und Oberflächen analog zu [001]-orientierten Schichten. Weiterhin wurde die Stabilität der Fe_(3+x)Si_(1-x) Phase über einen weiten Kompositionsbereich innerhalb der Fe_3Si-Stoichiometry demonstriert. Die Abhängigkeit der magnetischen Anisotropie innerhalb der Schichtebene von der Schichtdicke weist zwei Bereiche auf: einen Beresich mit dominanter uniaxialer Anisotropie für Fe-Schichten = 70 MLs. Weiterhin wird eine magnetische Anisotropie senkrecht zur Schichtebene in sehr dünnen Schichten gefunden. Der Grenzflächenbeitrag sowohl der uniaxialen als auch der senkrechten Anisotropiekonstanten, die aus der Dickenabhängigkeit bestimmt wurden, sind unabhängig von der [113]-Orientierung und eine inhärente Eigenschaft der Fe/GaAs-Grenzfläche. Die anisotrope Bindungskonfiguration zwischen den Fe und den As- oder Ga-Atomen an der Grenzfläche wird als Ursache für die uniaxiale magnetische Anisotropie betrachtet. Die magnetische Anisotropie der Fe_3Si-Schichten auf GaAs(113)A-Substraten zeigt ein komplexe Abhängigkeit von der Wachstumsbedingungen und der Komposition der Schichten. In den Magnetotransportuntersuchungen tritt sowohl in Fe(113)- als auch in Fe_3Si(113)-Schichten eine antisymmetrische Komponente (ASC) im planaren Hall-Effekt (PHE) auf. Ein phänomenologisches Modell, dass auf der Kristallsymmetrie basiert, liefert ein gute Beschreibung sowohl der ASC im PHE als auch des symmetrischen, anisotropen Magnetowiderstandes. Das Modell zeigt, dass die beobachtete ASC als Hall-Effekt zweiter Ordnung beschreiben werden kann.In this work, the molecular-beam epitaxial growth and properties of ferromagnets, namely Fe and Fe_3Si are studied on low-symmetric GaAs(113)A substrates. Three important aspects are investigated: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe_3Si films on GaAs(113)A substrates. The growth of Fe and Fe_3Si films is optimized at growth temperatures of 0 and 250 degree Celsius, respectively, where the layers exhibit high crystal quality and a smooth interface/surface similar to the [001]-oriented films. The stability of Fe_(3+x)Si_(1-x) phase over a range of composition around the Fe_3Si stoichiometry is also demonstrated. The evolution of the in-plane magnetic anisotropy with film thickness exhibits two regions: a uniaxial magnetic anisotropy (UMA) for Fe film thicknesses = 70 MLs. The existence of an out-of-plane perpendicular magnetic anisotropy is also detected in ultrathin Fe films. The interfacial contribution of both the uniaxial and the perpendicular anisotropy constants, derived from the thickness-dependent study, are found to be independent of the [113] orientation and are hence an inherent property of the Fe/GaAs interface. The origin of the UMA is attributed to anisotropic bonding between Fe and As or Ga at the interface, similarly to Fe/GaAs(001). The magnetic anisotropy in Fe_3Si on GaAs(113)A exhibits a complex dependence on the growth conditions and composition. Magnetotransport measurements of both Fe(113) and Fe_3Si(113) films shows the striking appearance of an antisymmetric component (ASC) in the planar Hall effect (PHE). A phenomenological model based on the symmetry of the crystal provides a good explanation to both the ASC in the PHE as well as the symmetric anisotropic magnetoresistance. The model shows that the observed ASC component can be ascribed to a second-order Hall effect.
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Hadi, Muhammad Usman. "Digital predistortion for compensation of nonlinearities in Radio over Fiber Links." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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In order to cope up with the ever increasing demand for larger transmission bandwidth, Radio over Fiber technology is a very beneficial solution. These systems are expected to play a major role within future fifth generation wireless networks due to their inherent capillary distribution properties.
Nonlinear compensation techniques are becoming increasingly important to improve the performance of telecommunication channels by compensating for channel nonlinearities. Indeed, significant bounds on the technology usability and performance degradation occur due to nonlinear characteristics of optical transmitter, nonlinear generation of spurious frequencies, which, in the case of RoF links exploiting Directly Modulated Lasers , has the combined effect of laser chirp and optical fiber dispersion among its prevailing causes.
The purpose of the research is to analyze some of the main causes of harmonic and intermodulation distortion present in Radio over Fiber (RoF) links, and to suggest a solution to reduce their effects, through a digital predistortion technique.
Predistortion is an effective and interesting solution to linearize and this allows to demonstrate that the laser’s chirp and the optical fiber’s dispersion are the main causes which generate harmonic distortion. The improvements illustrated are only theoretical, based on a feasibility point of view. The simulations performed lead to significant improvements for short and long distances of radio over fiber link lengths.
The algorithm utilized for simulation has been implemented on MATLAB. The effects of chirp and fiber nonlinearity in a directly modulated fiber transmission system are investigated by simulation, and a cost effective and rather simple technique for compensating these effects is discussed. A detailed description of its functional model is given, and its attractive features both in terms of quality improvement of the received signal, and cost effectiveness of the system are illustrated.
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Moncayo, Winston Junior Zumaeta. "Análise de segunda ordem global em edifícios com estrutura de concreto armado." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-19042011-085946/.
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A análise de segunda ordem global de edifícios é indispensável nos dias atuais, em que as estruturas são cada vez mais esbeltas. No mercado, há diversos sistemas computacionais que realizam essa análise, e alguns dos novos engenheiros estruturais podem não saber os conceitos em que ela se baseia. Portanto, este trabalho pretende: avaliar os efeitos de segunda ordem em edifícios por meio dos coeficientes \'gama\'z e FAVt, este desenvolvido pela TQS, e por meio do processo P-Delta; mostrar como este processo P-Delta funciona e como o sistema computacional CAD/TQS o considera; e analisar também os esforços de segunda ordem calculados a partir dos de primeira ordem multiplicados por O,95 \'gama\'z. Em relação à avaliação da estabilidade global, serão comparados os resultados obtidos com os parâmetros \'alfa\', \'gama\'z, FAVt e RM2M1, este último gerado a partir do processo P-Delta. Pretende-se, assim, fornecer subsídios para que os novos engenheiros tenham condições de atuar com base conceitual bem fundamentada, tanto na escolha do método quanto na análise dos resultados.The overall second-order analysis of buildings is essential nowadays, in which the structures are each time more slender. In the market, there are several computer systems that perform this analysis, and some new structural engineers can not know the concepts on which it rests. Therefore, this study aims: to evaluate the second-order effects in buildings making use of the coefficients \'gama\'z and FAVt, this developed by TQS, and using P-Delta process; to show how this P-Delta process works and how the computer system CAD/TQS considers it; and also analyze the second order efforts obtained from the first-order ones multiplied by O,95 \'gama\'z. Regarding the evaluation of overall stability, will be compared the results obtained with the parameters \'alfa\', \'gama\'z, FAVt, and RM2M1, the latter generated from the P-Delta process. It is intended, therefore, to provide subsidies for new engineers to be able to work with well-founded conceptual base, both in the choice of method and analysis of results.
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Malakoski, Joice. "Pilares esbeltos de concreto armado com seção variável." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-22022018-152222/.
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São descritas as recomendações da Norma Brasileira NBR-6118/1978 e do Código Modelo do Comité Euro-internacional du Béton CEB-1990 para a verificação da estabilidade de pilares esbeltos de concreto armado com seção variável submetidos à flexão normal composta, empregando-se a teoria do método geral. Para a obtenção dos momentos de segunda ordem são descritos os métodos de Engesser-Vianello e da integração numérica das curvaturas das seções transversais ao longo do pilar. Para a determinação do momento fletor absorvido pelas seções em função da curvatura proveniente da flexão do pilar sob a ação de uma força normal, desenvolvem-se as expressões para seções retangulares e circulares (cheias e vazadas) com base nas relações de tensão-deformação dos materiais segundo a norma e o código supracitados. Apresenta-se também um programa para microcomputador, elaborado em linguagem PASCAL, destinado à verificação da estabilidade de pilares com opção de adoção dos critérios da NBR-6118/1978 ou do CEB-1190. Não foram abordados os efeitos decorrentes de vibrações, fazendo-se apenas a descrição dos métodos de consideração dos efeitos decorrentes da deformação lenta.The recommendations of Brazilian Code NBR-6118/1978 and Comité Euro-Internacional du Béton Model Code CEB-1990 are described, for stability verification of concrete slender columns with variable cross sections, subjected to axial load and bending moment, using the exact method. To obtain the second order bending moments, the Engesser-Vianello method and the numeric integration of the cross section curvatures along the longitudinal axial of column method are described. To obtain of bending moment supported by the cross sections due to curvature resultant of the column flexure under axialload, expressions for rectangular and circular (full and hollow) cross sections are developed, using stress-strain relations for materials proposed by model codes above mentioned. It\'s also presented a software written in PASCAL language for microcomputer and destined to column stability verification, with option to adopt the NBR-6118/1978 or CEB-1990 model code recommendations. Effects due to vibrations were nor included. Methods to take in account creep effects were described.
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Antoniades, Savopoulos Anastasia. "Exploring the experiences of mothers after participating in a mother-child interaction intervention, within an HIV context." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-07082009-084041.
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Prawatmuang, Woramon. "Effects of positive evidence, indirect negative evidence and form-function transparency on second language acquisition : evidence from L2 Chinese and L2 Thai." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270338.
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This study investigates second language (L2) acquisition of word orders and markers of collectivity in Chinese and Thai. One of the differences between Chinese and Thai is that Chinese nominal phrases appear with a “numeral + classifier + noun” word order while Thai phrases appear as “noun + numeral + classifier”. Another difference is that men, the Chinese collective marker, cannot be used with nouns referring to animals or indefinite nouns, while phûak, the Thai collective marker, can do so. Based on the cross-linguistic differences, an empirical study was conducted to answer whether Thai learners of Chinese and Chinese learners of Thai would be able to acquire target language (TL) structures that are different from those in their native language (L1) and whether they could reject incorrect TL structures. One hundred and forty-four participants were recruited to complete an acceptability judgment task and a self-paced reading task. It is found that both Chinese and Thai learners could perform native-like in their acceptance of TL word orders since early stages of acquisition. However, it took them until an advanced level to be able to completely reject incorrect TL word orders that resembled structures in their L1. Thai learners also faced difficulty rejecting the use of men with animal and indefinite nouns in their L2 Chinese. In contrast, Chinese learners tended to be successful in their acquisition of phûak. The results are interpreted in terms of roles of positive evidence and form-function transparency. In general, L2 learners tend to acquire a TL structure earlier when they can receive positive evidence in TL input and when a form-function connection of the structure is transparent. Nonetheless, these factors do not have an absolute effect on acquisition outcome since some learners may be able to use a probabilistic learning strategy to successfully acquire L2 knowledge even when positive evidence is unavailable.
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Pham, Duc Toan. "Analyse par le calcul à la rupture de la stabilité au feu des panneaux en béton armé de grandes dimensions." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1073/document.
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Le présent travail propose et développe une méthode originale de dimensionnement vis-à-vis de l'incendie de parois de bâtiments industriels, en s'intéressant plus spécifiquement au cas des panneaux en béton armé de grande hauteur. Soumis à un fort gradient thermique, ces derniers subissent en effet des déplacements hors plan importants qui, du fait de l'excentrement du poids propre qui en résulte, vont engendrer des efforts de flexion venant s'ajouter aux efforts de compression déjà existants. Un tel changement de géométrie, d'autant plus prononcé que le panneau est de grande hauteur, combiné à une dégradation simultanée des propriétés de résistance des matériaux sous l'effet de l'élévation de température, peut conduire à un effondrement de la structure sous poids propre, bien avant par exemple l'apparition d'une instabilité de type flambement. L'approche proposée repose très largement sur la théorie du Calcul à la Rupture, appliquée d'une part à la détermination d'un diagramme d'interaction au feu caractérisant la résistance du panneau en chacune de ses sections, d'autre part à l'analyse de la ruine globale du panneau dans sa configuration déformée. Cette démarche est d'abord mise en œuvre et complètement explicitée dans le cas où le panneau peut être modélisé comme une poutre unidimensionnelle, conduisant à la détermination exacte d'un facteur adimensionnel caractérisant la stabilité de ce dernier. La généralisation de la méthode de calcul à la configuration plus réaliste, mais plus complexe, d'un panneau schématisé comme une plaque rectangulaire, est ensuite développée. Elle aboutit à un certain nombre de résultats préliminaires qui devront être confortés et affinés dans un travail ultérieur. L'approche théorique ici présentée est par ailleurs complétée par un volet expérimental (essais de flexion quatre points de dalles dans un four à maquette) qui a permis de valider au moins partiellement les évaluations du diagramme d'interaction prédites par le calculIn this contribution, an original and comprehensive method aimed at designing vertical concrete walls submitted to fire loadings, is proposed and developed, with a special emphasis on high rise panels used in industrial buildings. Indeed, when subjected to high thermal gradients, such slender structures exhibit quite significant out-of-plane movements, resulting in an eccentricity of the gravity loads and thus to bending moments in addition to the pre-existing compressive forces. It is such a change of geometry, which is all the more pronounced as the panel is tall, combined with a temperature-induced degradation of the constituent materials strength properties, which may explain why an overall collapse of the structure may occur, well prior to buckling instability. The proposed approach is fundamentally based on the theory of yield design. This theory is first applied to the determination of an interaction diagram, characterizing the fire resistance of a reinforced concrete panel cross-section. It is then implemented as a design method for analysing the stability of the panel in its previously calculated deformed configuration. The whole procedure is explained in full details in the simplified situation when the high rise panel can be modeled as a one-dimensional beam, leading to the exact determination of a dimensionless factor characterizing the stability of the panel. The method is then extended to deal with a more realistic, but somewhat more complex, configuration of a rectangular panel. Some preliminary results, which need to be further validated in a subsequent work, are finally produced. As a necessary complement to the mostly theoretical and computational approach presented in this work, a series of four-point bending tests has been performed on reduced scale slabs placed in a furnace. The results of these tests partially validate the predicted interaction diagram of a fire loaded panel section
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Pinto, Rivelli da Silva. "Não-linearidade física e geométrica no projeto de edifícios usuais de concreto armado." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-25052018-173137/.
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Neste trabalho são discutidos os procedimentos simplificados para a consideração da não linearidade física (NLF) e da não linearidade geométrica (NLG) na análise de edifícios de concreto armado. Deste modo, pretende-se estabelecer o grau de confiabilidade desses processos. Algumas prescrições para redução na inércia dos elementos estruturais são comparadas com os resultados obtidos através de modelos em elementos finitos, permitindo, assim, a avaliação destas prescrições. Um estudo detalhado do parâmetro γz, como majorador dos esforços em primeira ordem para a obtenção dos esforços finais em segunda ordem, é efetuada, de modo que se possa estabelecer, de forma mais clara, as vantagens e as limitações deste parâmetro.This work shows some simplified procedures to consider physical non-linearity (FNL) and geometrical non-linearity (GNL), for reinforced concrete buildings, and discusses its reliability. For FNL, prescriptions for stiffness reduction of structural elements are compared with the results obtained from finite elements analysis, in order to verify its assessment. For GNL, a detailed study of the accuracy of γz parameter to evaluate final second order effects is made. The behavior of the parameter along the height of the building and for each effort considered is shown.
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Ozgur, Cagri. "Behavior and Analysis of a Horizontally Curved and Skewed I-girder Bridge." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14637.
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This thesis investigates the strength behavior of a representative highly skewed and horizontally curved bridge as well as analysis and design procedures for these types of structures. The bridge responses at and above a number of limits in the AASHTO (2007) Specifications are considered. The study includes the evaluation of various attributes of the elastic analysis of the subject bridge. These attributes include: (1) the accuracy of 3-D grid versus 3-D FEA models, (2) first-order versus second-order effects during the construction, (3) the ability to predict layover at bearing lines using simplified equations and (4) the benefit of combining the maximum and concurrent major-axis and flange lateral bending values due to live load compared to combining the maximums due to different live loads when checking the section resistances. The study also addresses the ability of different AASHTO 2007 resistance equations to capture the ultimate strength behavior. This is accomplished by comparing the results from full nonlinear 3-D FEA studies to the elastic design and analysis results. Specifically the use of the 2007 AASHTO moment based one-third rule equations is evaluated for composite sections in positive bending.
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Camargo, Rafael Eclache Moreira de. "Contribuição ao estudo da estabilidade de edifícios de andares múltiplos em aço." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-23102012-095939/.
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Este trabalho apresenta uma análise comparativa de diferentes sistemas estruturais para um edifício de 20 pavimentos. Cada um dos modelos foi dimensionado através dos princípios do método da análise direta, presente na ABNT NBR 8800:2008. O método da amplificação dos esforços solicitantes (MAES) foi usado para se obter de forma simplificada os esforços atuantes nos elementos do edifício considerando os efeitos locais e globais de segunda ordem. A incidência do vento foi simulada de duas formas diferentes. Na primeira, chamada de uniforme, o vento foi aplicado sem excentricidade, gerando apenas o efeito de tombamento nas estruturas. Na segunda hipótese, considerou-se uma excentricidade devida aos efeitos de vizinhança, prescrita pela ABNT NBR 6123:1988, responsável por ocasionar o tombamento e a torção dos edifícios. Todas as análises numéricas foram repetidas fazendo o uso de outro método simplificado de segunda ordem, conhecido como P-Delta. Por meio dos resultados obtidos, constatou-se que a possibilidade de se reduzir a sobrecarga para o dimensionamento de pilares proporciona uma economia de material, mas, por outro lado, tem como consequência o aumento do tempo de análise, pois exige a utilização de diferentes combinações de cálculo para o dimensionamento de vigas e pilares. A estratégia utilizada para simular os efeitos de vizinhança mostrou-se satisfatória, pois permitiu introduzir de maneira fácil e prática a torção ocasionada pela incidência excêntrica do vento. Observou-se também que esses efeitos ocasionaram o aumento dos momentos fletores e dos deslocamentos das estruturas analisadas. Em relação à avaliação dos efeitos de segunda ordem, comprovou-se que, para a classificação da deslocabilidade, a combinação de cálculo crítica é aquela que possui o maior carregamento gravitacional. Entretanto, para o dimensionamento dos elementos, foi constatado que outras hipóteses de cálculo, principalmente aquelas em que o vento é a ação variável principal, podem ser determinantes. Por fim, foi observado que os resultados obtidos pelo método P-Delta ficaram bastante semelhantes àqueles calculados pelo MAES, com desvios desprezíveis. O MAES, por sua vez, mostrou-se bastante trabalhoso, pois exige a modelagem de diferentes tipos de estruturas para a determinação dos esforços.This work presents a comparative analysis of different structural systems for a 20-storey building. Each model has been designed using the principles of the direct analysis method (DAM), present in the ABNT NBR 8800:2008. The first-order amplification method (FOAM) was used to obtain, in a simplified manner, the forces acting on the building elements, including local and global second-order effects. The incidence of the wind was simulated in two different ways. In the first case, named uniform, the wind was applied without eccentricity, generating only structure overturning. In the second case, it was considered an eccentricity due to vicinity effects, prescribed by the ABNT NBR 6123:1988, responsible for causing twisting and building overturning. All numerical analysis were carried out a simplified second-order method known as P-Delta. From the results obtained it was found that the reduction of live loads in the design of columns provides material economy, but on the other hand, increases analysis time, since it requires different combinations for beams and columns. The strategy used to simulate the vicinity effects was satisfactory, because it allowed, in an easy and practical way, the consideration of the torsion produced by the wind eccentric impact. It was also observed that these effects increased the bending moments and the displacements of the structures. About the second-order effects, it was shown that, for sway or non-sway classification, the critical combination is one with greatest gravitational loading. However, for the design of the elements, it was observed that other loading conditions can be critical, especially those in which the wind is the main live load. Finally, the results obtained by the P-Delta method were very similar to those calculated by the first-order amplification method. The FOAM was, in turn, very laborious, because it requires the modeling of different types of structures for the determination of the forces.
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Descamps, Théo. "Numerical analysis and development of accurate models in a CFD solver dedicated to naval applications with waves." Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0049.
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L’objectif de cette thèse est de développer des solveurs numériques et des méthodologies afin d’améliorer le temps de calcul et la précision des simulations de tenue à la mer et de résistance ajoutée sur houle. Tout d’abord, une synthèse de l’algorithme du solver foamStar développé en interne est effectuée. A partir de cette analyse, une modification est proposée afin de pouvoir utiliser le "Multidimensional Universal Limiterfor Explicit Solution" (MULES) avec un schéma temporel backward d’ordre deux. Ensuite, plusieurs études successives sont réalisées afin de : vérifier l’implémentation du schéma backward ; définir une configuration numérique et des maillages efficaces pour la simulation de houle. Les cas d’étude sont : les tourbillons de Taylor-Green, la houle régulière non linéaire se propageant dans un domaine periodique, et enfin, la houle régulière générée avec des zones de relaxation et des configurations numériques proches de celles utilisées pour des applications navales. Dans la dernière partie de cette thèse, une étude préliminaire est réalisée en simulant un porte-conteneur avec une vitesse d’avance dans des houles régulières de face. Les recommandations définies tout au long de cette thèse sont également évaluéesThe objective of the present thesis is to develop solvers and methodologies in order to improve the computational cost andthe accuracy with regard to the thematics of seakeeping and added resistance. First, a synthetic workflow of the algorithmof the in-house solver foamStar is proposed. From this analysis a modification is proposed in order to use the Multidimensional Universal Limiter for Explicit Solution (MULES) with a second-order backward time scheme. Then, successive studies are done in order to: verify the implementation of the backward scheme; define an efficient numerical set-up and adequate mesh structures for numerical wave simulations. The case studies are, Taylor-Green vortices, nonlinear regular wave propagating in a periodic domain, and finally, regular waves generated with relaxation zones considering numerical configurations close to what is used for naval applications. In the last part of this Thesis, a preliminary study is done simulating a containership with forward speed in head regular waves. The recommendations derived all along this thesis are also evaluated
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Ayad, Mohammad. "Homogenization-based, higher-gradient dynamical response of micro-structured media." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0062.
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Une approche dynamique discrète (DDM) est proposée dans le contexte de la mécanique des poutres pour calculer les caractéristiques de dispersion des structures périodiques. Cette démarche permet de calculer les caractéristiques de dispersion de milieux périodiques unidimensionnels et bidimensionnels. Il est montré qu’un développement d'ordre supérieur suffisamment élevé des forces et des moments d’éléments structuraux est nécessaire pour décrire avec précision les modes de propagation d’ordre supérieur. Ces résultats montrent dans l’ensemble que les calculs des caractéristiques de dispersion de systèmes structurels périodiques peuvent être abordés avec une bonne précision par la dynamique des éléments discrets. Les comportements non classiques peuvent être capturés non seulement par une expansion d'ordre supérieur mais aussi par des formulations à gradient supérieur. Nous calculons ainsi les paramètres constitutifs macroscopiques jusqu'au deuxième gradient du déplacement en utilisant deux formulations différentes, soit selon une méthode d'homogénéisation dynamique à gradient supérieur (DHGE) prenant en compte les effets de micro-inertie, ou alternativement selon le principe de Hamilton. Nous analysons ensuite la sensibilité des termes constitutifs du second gradient aux paramètres microstructuraux pour des matériaux composites à microstructure périodique de type laminés. En plus, on montre que les modèles du deuxième gradient formulés à partir de l'énergie interne totale en tenant compte des termes de gradient d'ordre supérieur donnent la meilleure description du propagation d’onde à travers ces milieux. On analyse les contributions d'ordre supérieur et de micro-inertie sur le comportement mécanique de structures composites en utilisant une méthode d'homogénéisation dynamique d'ordre supérieur qui intègre les effets de micro-inertie. Nous calculons la réponse effective statique longitudinale à gradient d’ordre supérieur, en quantifiant la différence relative par rapport à la formulation classique de type Cauchy qui repose sur le premier gradient du déplacement. Nous analysons ensuite les propriétés de propagation d’ondes longitudinales en termes de fréquence propre de composites, en tenant compte de la contribution de la micro-inertie. La longueur interne joue un rôle crucial dans les contributions de micro-inertie avec un effet substantiel pour les faibles valeurs de longueur interne, et qui correspond à une large gamme de matériaux utilisés en ingénierie des structures. La méthode d’homogénéisation développée montre un effet de taille important pour les modules élastiques homogénéisés d’ordre supérieur. Par conséquent, nous développons une formulation indépendante de la taille qui est basée sur des termes de correction liée aux moment quadratique. Dans ce contexte, on analyse l’influence des termes de correction sur le comportement statique et dynamique de composites à inclusionA discrete dynamic approach (DDM) is developed in the context of beam mechanics to calculate the dispersion characteristics of periodic structures. Subsequently, based on this dynamical beam formulation, we calculate the dispersion characteristics of one-dimensional and two-dimensional periodic media. A sufficiently high order development of the forces and moments of the structural elements is necessary to accurately describe the propagation modes of higher order. These results show that the calculations of the dispersion characteristics of structural systems can be approached with good accuracy by the dynamics of the discrete elements. Besides, non-classical behaviors can be captured not only by higher order expansion but also by higher gradient formulations. To that scope, we develop a higher gradient dynamic homogenization method with micro-inertia effects. Using this formulation, we compute the macroscopic constitutive parameters up to the second gradient, using two distinct approaches, namely Hamilton’s principle and a total internal energy formulation. We analyze the sensitivity of the second gradient constitutive terms on the inner material and geometric parameters for the case of composite materials made of a periodic, layered microstructure. Moreover, we show that the formulations based on the total internal energy taking into account higher order gradient terms give the best description of wave propagation through the composite. We analyze the higher order and micro-inertia contributions on the mechanical behavior of composite structures by calculating the effective static and dynamic properties of composite beams using a higher order dynamic homogenization method. We compute the effective longitudinal static response with higher order gradient, by quantifying the relative difference compared to the classical formulation of Cauchy type, which is based on the first gradient of displacement. We then analyze the propagation properties of longitudinal waves in terms of the natural frequency of composite structural elements, taking into account the contribution of micro-inertia. The internal length plays a crucial role in the contributions of micro-inertia, which is particularly significant for low internal length values, therefore for a wide range of materials used in structural engineering. The developed method shows an important size effect for the higher gradients, and to remove these effects correction terms have been incorporated which are related to the quadratic moment of inertia. We analyze in this context the influence of the correction terms on the static and dynamic behavior of composites with a central inclusion
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Lin, Yu-Ren, and 林育仁. "Analysis Frame of Second Order Effect by SCEM." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/75412669032615157772.
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Shie, Shu-Hao, and 謝樹豪. "The Analysis of Dispersion Effect for First-order and Second-order Optical Element in White Light LEDs." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/d3386t.
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碩士逢甲大學
光電學系
103
In this study, we discusse the dispsersion effect in White light LEDs (WL-LED) according to Snell’s law, obtaining the relationship between the shape of packaging lens and it by analyzing the light pattern. Besides, to understand the influence to the first-order dispersion by second-order optics, we also add a reflecting optics to our experiment and simulation. Furthemore, we fabricate lens and use equivalent light emitting surface that avoid other factors such as reflector cup、phosphor coating which might affect the dispersion effect, and we also can infer the position of each wavelengths that emiitinng out from the optical system by our formula, then explain the result we had. Hence, according to our results, Round typ LED has the largest angular difference for ∆θ_br=0.76° under the normalize intensity at 0.1 a.u, and Lambertian type LED has the smallest valuse for ∆θ_br=0.14°, moreover, with increasing the size of packaging lens, the values of angular difference will also be reduced. Eventually, taking Round type LED as example, we find the angular difference will be dramatically reduced from 0.76° to 0.035° at normalized intensity at 0.1 a.u when reflecting optics is applied.
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Chiu, W.-J., and 邱文榮. "Parasitic Effect of the Current-Mode Second-Order OTA-C Low Pass Filter Structure." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/90126113367102609867.
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碩士中原大學
電機工程研究所
96
It is worthy of research to do the analogue circuit using Operational Transconductance Ampplifiers (OTAs) and Capacitors (Cs), because an OTA with the property of an active element can replace a resistor such that no resistors will be needed in the integrated circuit. In addition, the equivalent resistor value can be electronically tuned by varying the bias current. Recently, owing to the appearance of “Analytical Synthesis Method”, the circuit with third-order OTA-C elliptic filters has achieved the three following important advantages: (i) using single-ended-input OTAs (overcoming the feed-through effect due to the use of differential-input OTAs), (ii) using grouded capacitors (absorbing the shunt parasitic capacitance), and (iii) using the minimum components and all the parasitic capacitances have the same places as those of all the given capacitors in the realized circuits. The output signals will be distorted in the high frequency as a result of the varieties of parasitic capacitances and the non-ideal effect. Therefore, taking the non-ideal effect of OTAs into consideration, we analyze the ratio of the output current to the input voltage of OTAs, which is called frequency dependent transconduce, for the purpose of increasing the switching frequency in the filter structure. The experimental results also show that the non-ideal effect indeed influences the output signal. Based on the non-ideal effect upon the output signal and the improvement on the frequency dependent transconduce, we propose a method that adopts tunable OTA to improve the non-ideal effect of OTA to solve the problems resulted from the non-ideal effect and parasitic effect. Accordingly, the signal can be output more precisely. Finally, the H-spice simulation with Tsmc35.l process verifies the theoretical predictions.
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TSOU, CHING-HUEI, and 鄒慶暉. "Second-Order Analysis of Planar Steel Frames Considering the Effect of Spread of Plasticity." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/31531045545480266838.
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Chang, Wei-Chun, and 張惟淳. "Non-ideal Effect and Improvement of TheVoltage-Mode Second-Order High-fequency OTA-C Filter Structure." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/35761895246144589741.
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碩士中原大學
電機工程研究所
93
There are several kinds of parasitic capacitances, including input and output parasitic capacitances of an OTA and the nodal parasitic capacitance at the internal node in an OTA-C (Operational Transconductance Amplifier and Capacitor) circuit. This leads to the difficulty to have the same places for both given capacitors and all the parasitic capacitances. When the differential-input OTA and floating capacitances are employed in the circuit structure, and the impossibility to obtain a high–frequency circuit with precise output responses by giving a proper capacitor value after absorbing the parasitic capacitance. Recently, the “Analytical Synthesis Method” has been proposed to realize the high-order OTA-C circuits which achieving the following three important criteria simultaneously for the design of OTA-C filters: (i) using single-ended-input OTAs (overcoming the feedthrough effect due to the use of differential-input OTAs), (ii) using grounded capacitors (absorbing the shunt parasitic capacitance), and (iii) using the least number of component counts (reducing the total parasitic effects). Note that all the parasitic capacitances have the same places as those of all the given capacitors in the realized circuits achieving the above three important criteria. An improvement approach is then proposed by the absorption of parasitic capacitances from the given capacitors to obtain a precise high-frequency circuit. The non-ideal effect in an OTA is resulted from the parasitic capacitances spreaded among the MOS transistors which is called the frequency dependent transconduce, namely, the ratio between the output current phasor and the input voltage phasor, of an OTA. The non-ideal effect out of the OTA includes the input and output parasitic capacitance and the output parasitic conductance of an OTA and the nodal parasitic capacitance at each internal node. In this thesis, a voltage-mode second-order OTA-C universal filter structure is used for example to demonstrate this new improvement for a high-frequency circuit. When the simulation resonance frequency is higher than the theoretical value, this implies that the given transconductance is also higher than the exact value. The reduction of the given transconductance leads to approach the theoretical prediction. On the contrary, if the simulation resonance frequency is lower than the theoretical value, it means that the additional parasitic capacitance makes a total capacitance larger than the exact value. The absorption of parasitic capacitance from the given capacitor leads to close the ideal requirement. After several reductions of transconductances or absorptions of capacitances can enter the very precise range with the error lower than 1% for the simulation resonance frequency. Furthermore, as the operational frequency increases, the numbers of pole and zero of the frequency dependent transconductance of an OTA three-OTA circuit increases, too Based upon different simulation results, different frequency dependent transconductance are given to consist with the practical variation. Finally, The above proposed improvement was verified by UMC05 H-spice simulation with supply voltages ±2.5V.