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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Methods, goals and metaphysics in contemporary set theory

Rittberg, Colin Jakob January 2016 (has links)
This thesis confronts Penelope Maddy's Second Philosophical study of set theory with a philosophical analysis of a part of contemporary set-theoretic practice in order to argue for three features we should demand of our philosophical programmes to study mathematics. In chapter 1, I argue that the identification of such features is a pressing philosophical issue. Chapter 2 presents those parts of the discursive reality the set theorists are currently in which are relevant to my philosophical investigation of set-theoretic practice. In chapter 3, I present Maddy's Second Philosophical programme and her analysis of set-theoretic practice. In chapters 4 and 5, I philosophically investigate contemporary set-theoretic practice. I show that some set theorists are having a debate about the metaphysical status of their discipline{ the pluralism/non-pluralism debate{ and argue that the metaphysical views of some set theorists stand in a reciprocal relationship with the way they practice set theory. As I will show in chapter 6, these two stories are disharmonious with Maddy's Second Philosophical account of set theory. I will use this disharmony to argue for three features that our philosophical programmes to study mathematics should have: they should provide an anthropology of mathematical goals; they should account for the fact that mathematical practices can be metaphysically laden; they should provide us with the means to study contemporary mathematical practices.
72

Optimising the transformation and yield to ultimate strength ratio of Nb-Ti micro-alloyed low carbon line pipe steels through alloy and microstructural control

Tang, Zhenghua 21 July 2007 (has links)
Thinner walled (about 6 mm thickness) line pipe steels for smaller diameter pipelines tend to have a relatively high ratio of yield strength to ultimate tensile strength (YS/UTS) of 0.93 or higher. This study focused on the effect of the microstructures, prior deformation in the austenite, cooling rate, coiling simulation and the additions of some micro-alloying elements on the YS/UTS ratio of a currently produced Nb-Ti and some experimental Nb-Ti-Mo line pipe steels. The experimental research included the design of the chemical compositions for five experimental alloys, simulation of the controlled hot rolling process, the determination of the strain-free as well as the strain affected continuous cooling transformation (CCT) diagrams, phase identification and quantitative assessment of the microstructures by optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the latter especially on shadowed carbon extraction replicas and, tensile tests etc. This study indicated that the transformed microstructures of the alloys were a mixture of acicular ferrite plus polygonal ferrite and the volume fraction of acicular ferrite varied from 46.3 to 55.4%. Molybdenum additions did not markedly affect the formation of acicular ferrite after hot rolling and rapid cooling. The microstructural details of the acicular ferrite were successfully revealed by TEM on shadowed extraction replicas. This technique was useful to distinguish the acicular ferrite from the polygonal ferrite through a more smooth surface relief after etching in 2% Nital of the little etched polygonal ferrite whereas the deeper etched acicular ferrite showed parallel sets of internal striations. This made it possible to measure the volume fraction of acicular ferrite in the mixed microstructures of acicular ferrite and polygonal ferrite. The continuous cooling transformation behaviors of two alloys with no molybdenum and with 0.22% Mo were constructed with no prior deformation as well as with prior deformation of the austenite. Molybdenum additions shifted the strain-free CCT diagram towards longer times and expanded the region in which acicular ferrite formed from a cooling rate range of 0.3 to 5 ºCs-1 (Mo-free) to 0.1 to 15 ºCs-1 (with 0.22% Mo). However, its effect was significantly overshadowed by prior deformation in the austenite. The strain affected CCT diagrams for both alloys appear to be similar. The prior deformation had a stronger effect on the CCT diagram than molybdenum additions and promoted acicular ferrite formation, whereas it suppressed the formation of bainite. The prior deformation had two effects in acicular ferrite formation: it promoted nucleation and suppressed its growth and, therefore, resulted in a finer overall grain size. The effect on the YS/UTS ratio at various cooling rates ranging from 1 to 34, 51, 54 or 60 ºCs-1 was investigated in three cases: (i) without prior deformation and coiling simulation, (ii) with no prior deformation but with coiling simulation at 575 and 600 ºC and, (iii) with prior deformation of 33% reduction in the austenite below the Tnr followed by coiling simulation at 575 ºC for 1 hour. It was determined that the YS/UTS ratio was a function of the microstructure and cooling rate in the case treatment (i)) without any coiling simulation and prior deformation. The coarse bainite or acicular ferrite, which was formed at high cooling rates, raised the YS/UTS ratio under conditions of no deformation prior to the transformation. The yield strength and ultimate tensile strength also increased with an increase in cooling rate. With coiling conditions (treatment (ii)), the ratio was not sensitive to the cooling rate or the microstructure for the reference Mo-free alloy #6 because the coiling allows recovery of dislocations, thereby decreasing the difference in dislocation density that had arisen between a low and a high cooling rate. The YS/UTS ratio ranged from 0.75 to 0.8 after a simulated coiling at 575 ºC and from 0.76 to 0.78 after a coiling simulation at 600 ºC. Prior deformation (treatment (iii)) in the austenite raised the ratio from 0.81 to 0.86. However, the YS/UTS ratio was not sensitive to cooling rate after coiling at 575 ºC for 1 hour in the cases with and without prior deformation in the austenite. Deformation with a 33% reduction below the Tnr prior to the transformation increased the yield strength more than the ultimate tensile strength, leading to a high YS/UTS ratio that ranged from 0.81 to 0.86. The prior deformation, therefore, had a stronger effect on the YS/UTS ratio than the microstructure. Towards cache optimization in finite automata / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / PhD / unrestricted
73

Últimos levelings: conceitos, propriedades, algoritmos e aplicações em processamento e análise de imagens / Ultimate levelings: concepts, properties, algorithms and applications for image processing and analysis

Wonder Alexandre Luz Alves 06 August 2015 (has links)
Em Morfologia Matemática diversos operadores são definidos pela diferença entre outros dois operadores, como por exemplo, o gradiente morfológico, definido como a diferença entre a dilatação e a erosão. Estes operadores são denominados operadores residuais, sendo alguns deles definidos por valores residuais extraídos de famílias indexadas de operadores, como por exemplo, o esqueleto por discos maximais e a última abertura. Neste sentido, visa-se neste trabalho investigar a extração de informações residuais em famílias indexadas de operadores. Mais precisamente, em famílias de operadores conexos conhecidos como levelings. Os levelings são operadores que não criam novas estruturas (contornos e extremos regionais) e seus valores são limitados pelos valores da imagem de referência. Assim, é apresentada nesta tese uma classe de operadores residuais denominada últimos levelings, a qual consiste de poderosos operadores residuais definidos a partir de resíduos gerados por operadores consecutivos de um espaço de escala baseado em levelings. Dessa forma, objetos contrastantes podem ser detectados se relevantes resíduos são gerados quando eles são filtrados por um desses levelings. Os valores residuais revelam importantes informações sobre contrastes presentes em uma imagem. Além dos valores residuais, outras informações associadas com eles podem ser obtidas no momento da extração residual, tais como os índices dos operadores que produziram os valores residuais. Com base nessas considerações, as principais contribuições originais desta pesquisa, incluem: (i) demonstrar que árvores construídas a partir de conjuntos de níveis representam espaços de escalas baseados em levelings; (ii) introduzir a classe dos últimos levelings, passando por definições, conceitos, algoritmos, propriedades e relações com outros operadores conhecidos na literatura; (iii) apresentar estratégias para construção de operadores últimos levelings. Por fim, são apresentadas aplicações dos últimos levelings em problemas de análise e processamento de imagens. / In Mathematical Morphology several operators are defined by the difference between two operators, such as morphological gradient, defined as the difference between the dilation and erosion. These operators are called residual operators, being that some are defined by the extracted residual values from of an indexed family of operators, for example, the skeleton by maximal discs and the ultimate opening. In this sense, we intend to investigate the extraction of residual information in families of operators. More precisely, in families of connected operators known as levelings. The levelings are operators that do not create new structures (contours and regional extremes) and their values are limited by the values of the reference image. Thus, we present in this thesis a class of residual operators named ultimate levelings, which consist of powerful residual operators defined from a scale space based on levelings. With a multi-scale approach, these operators analyze an image under a series of levelings. Thus, contrasted objects can be detected if a relevant residue is generated when they are filtered out by one of these levelings. The residual values reveal important informations about contrasts present in an image. In addition of residual values, other information associated with them can be obtained at the time of extraction residual, such as the indexes of operators who produced the residual values. Based on these considerations, the main original contributions of this research include: (i) demonstrate that the trees constructed from level sets represent an scale space based on levelings; (ii) introduce the class of levelings ultimate, passing by definitions, concepts, algorithms, properties and relationships with other known operators in the literature; (iii) show some strategies for building levelings ultimate operators. Finally, we present applications of levelings ultimate in problem of image processing and analysis.
74

The Security and Foreign Policy of the Islamic Republic of Iran: An Offensive Realism Perspective

Prifti, Bledar 16 December 2009 (has links)
This study argues that security and foreign policy of the Islamic Republic of Iran is mainly driven by the main principles of the Offensive Realism theory of international relations. While the Iranian political system is considered a theocratic system, based on the Islamic Shi'a ideology, its survival is defined as the ultimate ideology-an ideology that is paramount to any other ideology. Iran's security and foreign policy is determined and shaped by its need to survive in an anarchic international system. Iran's cooperation with "two Satans", Israel and the United States, during the Iran-Iraq war demonstrates that the ultimate ideology of survival dominates over any other ideological predisposition. In addition, the lack of a supranational government and the fear about the intentions of other states make Iran aware of the need to rely on self-help. Iran has also realized that the best way to limit threats to its survival would be maximizing its relative military power and becoming a regional hegemony. Furthermore, a formidable military power would provide Iran with a new status in regional and global politics, deterrence power over any possible attack from other great powers, and bargaining power over regional and global matters. In order to enhance its military (conventional and nuclear) arsenal, Iran has established "strategic relations" with its historic enemy, Russia. In its quest to advance its military capabilities and avoid threats to its sovereignty, Iran sided with Christian states, against its Muslim brothers, during the Russia-Chechnya and Armenia-Azerbaijan conflicts. Moreover, the Islamic state is aware of the fact that its paramount goals can be achieved by relying on precise rational strategies. In order to validate these claims, this study analyzes Iran's policy during the Iran-Iraq war and Iran's policy toward Armenian-Azerbaijani conflict, the Russian-Chechen conflict, and the U.S. invasion of Iraq.
75

Ultimate Shear Capacity and Residual Prestress Force of Full-Scale, Forty-One-Year-Old Prestressed-Concrete Girders

Osborn, Parry 01 May 2010 (has links)
The ultimate shear capacity of prestressed concrete beams is difficult to predict accurately, especially after being in service for an extended period of time. The Utah Department of Transportation asked researchers at Utah State University to experimentally determine the existing shear capacity of 41-year-old prestressed, decommissioned concrete bridge girders and then provide recommendations on how to increase that ultimate shear capacity. This thesis presents the research findings that relate to the existing shear capacity of the prestressed concrete girders. Eight AASHTO Type II bridge girders were tested up to failure by applying external loads near the supports to determine their ultimate shear capacities. The measured results were then compared to calculated values obtained using the AASHTO LRFD bridge design code, and the ACI 318-08 design code. Prestress losses were also measured by means of a cracking test and then compared to values calculated according to the AASHTO prestress loss equations. Both the ultimate shear capacities and the residual prestress forces were used to evaluate the girders after being in service for more than 40 years.
76

The Effect of Age on Second Language Acquisition in Older Adults

Major, Charisse Alaine 17 March 2014 (has links) (PDF)
A primary purpose of second language (L2) research is to determine what factors hinder or help L2 acquisition. One aspect that has a strong effect on L2 proficiency is learners' age of onset of acquisition (AOA) (Johnson & Newport, 1989). These studies and others suggest that younger learners are more adept than older learners at learning an L2, especially to a near-native level. However, some older learners can become quite proficient in an L2 (Ioup, et al. 1994; Bialystok, 1997; Bongaerts, 1999), although learners who have acquired the L2 over the age of 30 are rarely studied. Why is it that some older learners are more adept at learning a second language than others? Some argue cognitive abilities (Hyltenstam & Abrahamsson, 2002; DeKeyser, 2006) while others argue social and affective factors (Moyer, 1999) differ across the lifespan, causing younger learners to achieve a higher proficiency than older learners. Little research, however, has examined both these factors, especially in learners who acquired a language beyond early adulthood. Therefore, the purpose of this study was to determine 1) if there are age effects between groups of older adults learning an L2 and 2) what causes any differences found. This study examines a variety of both cognitive, affective and demographic factors that have been previously shown to affect language learning. The participants included 38 native Spanish speakers placed into four AOA groups: 10-19, 20-29, 30-39, and over 40. In order to test cognitive factors a working memory task as well as a switch task were included (Abrahamsson, 2012; Paradis, 2009). Other factors were assessed using a survey that inquired about motivation, amount of time using the L1 versus the L2, and musical ability (Slevc & Miyake, 2006). Subjects also participated in an elicited imitation task to assess global proficiency in the L2 (Erlam, 2009).Results suggest that age effects are found even in older learners. Participants with a younger AOA who spend more time speaking the L2 (English) tended to have greater proficiency in the L2. Attentional control was also a predictor.
77

Ductility of Reinforced Concrete Masonry Shear Walls

Shedid, Marwan Mohamed Tarek January 2006 (has links)
Pages vi, 34, 68, 158, 208 and 226 are blank and therefore omitted. / <p> To assess the ductility of shear walls under earthquake loading, more experimental evidence is strongly needed. Ductile response can be achieved through the development of a flexural plastic hinge at the base characterized by yielding of the vertical reinforcement. The length of the plastic hinge and the ultimate curvatures within this region are the essential parameters affecting the ductility and ultimate displacements of reinforced masonry shear walls. The discrepancies in existing information regarding the length of plastic hinges and ultimate curvature may be attributed to the effects of many shear wall parameters such as distribution and amount of vertical and horizontal steel, level of axial load, and wall aspect ratio. </p> <p> The focus of this study was to evaluate the effect of different parameters on plastic hinge length, energy dissipation, and on general ductility of masonry shear walls. To address the aforementioned goal, six fully grouted reinforced masonry walls were tested under fully reversed cyclic lateral loading. All walls were designed to experience ductile flexural failure. The test matrix was chosen to investigate the effects of the amount and distribution of vertical reinforcement and the level of applied axial load on the lateral loading response and ductility of reinforced masonry shear walls. To examine the effects of these parameters, measurements of the applied loads, vertical and horizontal displacements as well as strains in the reinforcing bars were used to analyze the behaviour of the walls. Also, from these measurements, other quantities used in analysis were determined, including displacement ductilities, curvature profiles, energy dissipation and equivalent plastic hinge length. </p> <p> The results show high ductile capability in the plastic hinge region and very little degradation of strength for cyclic loading. High levels of energy dissipation in the reinforced concrete masonry shear walls were achieved by flexural yielding of the vertical reinforcement. All walls showed increasing hysteretic damping ratios with increase in displacement. Results showed that displacement ductility and energy dissipation were highly sensitive to increases in amount of vertical reinforcement but were less dependent on the level of applied axial stress. The results of this study also showed that the measured plastic zone length decreases with increase of the amount of reinforcement while it is almost the same for the different levels of axial stress. Based on the test results, it was shown that reinforced concrete masonry shear walls may be utilized in high intensity seismic areas with performance meeting or exceeding current expectations. </p> / Thesis / Master of Applied Science (MASc)
78

Analysis of Gait Parameters and Knee Angles in Ultimate Frisbee Players: Implications for Balance and Injury

Nikcevich, Ethan 01 October 2023 (has links) (PDF)
Biomechanics research investigating gait and balance of ultimate frisbee players is an unexplored topic. Ultimate requires a wide range of motions that could improve balance and is also a sport prone to frequent injury. This study explores the impact of playing ultimate on gait parameters associated with balance and knee angles associated with joint injury. Gait trials were conducted on 8 ultimate players and 8 control participants between the ages of 18 and 23 to obtain total double support time, stance phase time, single support time, load response time, abduction-adduction (AA) angles, internal-external (IE) rotation angles, and flexion angles of the dominant leg’s knee. Knee angles were obtained through the application of a Triangular Cosserat Point Element (TCPE) analysis for Soft-Tissue Artifact (STA) correction of knee kinematics. The gait parameters and knee angles were compared between ultimate players and control group participants using two-sample t tests. The results indicated that (1) playing ultimate may be used to improve balance, and (2) playing ultimate may reduce the range of IE rotation angles.
79

Where is our disagreement? : A Zen-inspired method to understand deep disagreements

Li, Josua January 2023 (has links)
In this thesis, I develop a method that will help you, understand, and solve deep disagreements. In forming my method I draw on Zen Buddhist philosophy. In chapter one my understanding of deep disagreement is presented. Deep disagreements is seen as being caused by underlying metaphysical fundamental beliefs and/or worldviews. My method hinges on three concepts, interconnected, conventional centric, and ultimate reality. In the process of explaining these concepts important Zen Buddhist ideas are explored. By exploring which of these three categories a view or argument engages with you will be able to avoid deep disagreements because the types of beliefs that cause deep disagreements are made transparent. In the second chapter, I first analyze an argument against theism and for naturalism and show that there is a deep disagreement at play in that argument. In using my method you can see that the conflict is not a conflict. I then analyze animism and show that animism does not need to be in opposition to naturalism and that both can coexist. In the third chapter, a meta-analysis is made. The main advantage of my method is that it tries to understand and place all types of views into a bigger picture. This makes my method unifying. I also show that there is a wide range of areas in which this method could be used. It could be used in many situation of disagreement.
80

Unprecedented Mechanical Properties in Linear Ultrahigh Molecular Weight Polyethylene via Heterogeneous Catalytic Systems

Gote, Ravindra P. 07 1900 (has links)
Regardless of the simplicity in molecular structure, polyethylene is used in high-performance applications such as medical prostheses and ballistics. Recent advancements in homogeneous catalysis produced UHMWPE in the low-entangled or dis-entangled state that allowed solvent-free-solid-state processing to achieve ultimate mechanical properties ever achieved for a synthetic polymer. Although several homogeneous complexes are known to produce dis-UHMWPE, existing major challenges are uncontrolled nascent polymer morphology, as a consequence reactor fouling/wall sheeting. In such a scenario, a heterogeneous catalyst that can produce dis-UHWMPE to an extent that the characteristics and properties equivalent to that obtained in homogeneous condition, remains an open challenge. The thesis will discuss the know-how for the synthesis of dis-UHMWPE via heterogeneous route to facilitate industrial production by following fundamental understanding of polymerization catalysis, physics, processing, and testing. In this thesis, in-situ formed nano activator/support MgClx/EtnAly(2-ethyl-1-hexoxide)z is employed with a highly active bis[N-(3-tert-butylsalicylidene)pentafluoroanilinato] titanium (IV) dichloride (Cat. 1) for synthesis of dis-UHMWPE. In addition, the relatively easy formation of the MgClx/RnClmAly(OR’) activators/supports allows tailoring by the selection of different aluminum-alkyls and alcohols, giving access to a variety of co-catalysts. This investigation resulted in UHMWPE having Mw from 3 to an unprecedented 43 M g/mol and Ð from 3 to 38 with very high activities up to 2750 kgPE molcat.-1 bar-1 h-1. The adopted route resulted in nano-support that allows tailoring of the entangled state and control over the nascent morphology without reactor fouling, thus providing feasibility of pursuing the polymerization via a continuous process. The nascent polymer shows formation of single crystals of linear UHMWPE and is suggestive of the low-entangled state. The topological differences, with the commercial entangled sample, are identified solid-state NMR, DSC, and rheology. The disentangled crystals allowed desired chain orientation for securing unprecedented tensile modulus (>200 N/tex) and tensile strength (>4.0 N/tex) via solid-state processing. Additionally, the investigation of creep response in the uniaxial tapes has revealed strong influence of molecular weight and entanglement density. These unique characteristics and unprecedented mechanical properties are equivalent to that perceived using a homogeneous catalysis and are the first of their kind achieved for a polymer synthesized using a heterogeneous catalysis.

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