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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.
1

Elastic and viscoelastic properties of resin composites at the macroscopic and nano scales

El Safty, Samy January 2012 (has links)
Restoring both anterior and posterior teeth with resin-composite materials is now an established clinical procedure with almost universal acceptance. The clinical performance of these restorations in the patient’s mouth is determined by a number of factors including the clinical techniques involved in their placement, the patient’s oral habits, and the physical and mechanical properties of the restorative materials themselves. These materials are being increasingly used in load-bearing areas of the posterior dentition and are therefore inevitably subject to masticatory forces of varying magnitude. The success of different resin-composites in different applications is understood through their clinical performance and laboratory-based experimental evaluation.My research was divided into two parts; the first part was concerned with the examination of different types of contemporary restorative resin-composites and in the second part, I compared different methods of examination. In the first part, I investigated and compared different sets of varied types of resin-composites, such as flowable resin-composites, bulk-fill resin-composites and conventional resin-composites. Using different sets of these materials, I examined a number of properties that affect their clinical performance and durability.In the second part, I studied and compared the conventional (macroscopic) methods of investigation with nanoindentation method. Both methods were applied to examine and characterise different properties for some types of resin-composites.The flowable and the bulk-fill resin-composites exhibited satisfactory results comparable with conventional resin-composites. The properties investigated included strength properties, modulus of elasticity, hardness and viscoelastic time-dependent creep deformation. The results obtained by nanoindentation confirmed that this method of examination is a valuable experimental tool to investigate and characterise some mechanical properties of resin-composites.
2

Theoretical analysis of the effects of bus operations on urban corridors and networks

Castrillon, Felipe 07 January 2016 (has links)
Bus systems have a large passenger capacity when compared to personal vehicles and thus have the potential to improve urban mobility. However, buses that operate in mixed vehicle traffic can undermine the effectiveness of the road system as they travel at lower speeds, take longer to accelerate and stop frequently to board and alight passengers. In traffic flow theory, buses are known as slow-moving bottlenecks that have the potential to create queue-spillbacks and thus increase the probability of gridlock. Currently, traditional metropolitan transportation planning models do not account for these negative effects on roadway capacity. Also, research methods that study multimodal operations are often simulated or algorithmic which can only provide specific results for defined inputs. The objective of this research is to model and understand the effects of bus operations (e.g., headway, number of stops, number of routes) on system performance (e.g. urban corridor and network vehicular capacity) using a parsimonious analytical approach with a few parameters.The models are built using the Macroscopic Fundamental Diagram (MFD) of traffic which provides aggregate measures of vehicle density and flow. Existing MFD theory, which accounts for corridors with only one vehicle class are extended to include network roadway systems and bus operations. The results indicate that buses have two major effects on corridors: the moving bottleneck and the bus short-block effect. Also, these corridor effects are expanded to urban networks through a vehicle density-weighted average. The models have the potential to transform urban multimodal operations and management as they provide a simple tool to capture aggregate performance of transportation systems.
3

Modèles macroscopiques de conduction et d’élasticité linéarisée pour des milieux fortement hétérogènes et anisotropes / Macroscopic models of conduction and linear elasticity for highly heterogeneous and anisotropic media

Charef, Hamid 17 December 2012 (has links)
Dans cette thèse on étudie quelques modèles macroscopiques pour des milieux conducteurs ou élastiques fortement hétérogènes et anisotropes obtenus par homogénéisation. Nous considérons le cas de l’homogénéisation périodique. En particulier pour le système de l’élasticité linéarisée modélisant les petites déformations d’un matériau fibré, nous étudions l’effet de l’anisotropie du matériau sur le modèle macroscopique et nous montrons que sous l’effet conjugué des conditions aux limites et de l’anisotropie des fibres, le système modélisant les déplacements à l’échelle macroscopique fait intervenir des termes non standard. Nous considérons plusieurs scalings et deux situations géométriques : dans la première le rayon des fibres cylindriques est du même ordre de grandeur que la taille de la période du milieu et dans la seconde la rayon est petit devant la période. Les résultats obtenus dans les deux cas, indépendants d’hypothèses de symétrie sur le matériau, permettent de retrouver les résultats déjà connus dans le cas de matériaux isotropes. / In this thesis we study some macroscopic models for drivers or elastic media highly heterogeneous and anisotropic obtained by homogenization. We consider the case of periodic homogenization. In particular the system of linearized elasticity modeling small deformations of a fiber material, we study the effect of material anisotropy on the macroscopic model and show that the combined effect of the boundary conditions and the anisotropy of the fiber system modeling movement at the macroscopic scale involves non-standard terms. We consider several scalings and two geometric situations: in the first radius of cylindrical fibers is of the same order of magnitude as the size of the middle period and in the second the radius is small compared to the period. The results obtained in both cases, independent of symmetry assumptions on the material used to find the results already known in the case of isotropic materials.
4

Extended macroscopic dispersion model with applications to confined packed beds and capillary column inverse gas chromatography

Hamdan, Emad, Aerospace, Civil & Mechanical Engineering, Australian Defence Force Academy, UNSW January 2008 (has links)
Until present, many researchers relied on the conventional plug flow dispersion models to analyse the concentration profiles obtained from the tracer injection experiments to evaluate the dispersion coefficients in packed beds. The Fickian concept in the limit of long time duration is assumed to be applicable and it implies that the mean-square displacement of the tracer profile is constant with time and the concentration profile is Gaussian. There were very few studies on identifying the conditions under which this assumption is valid and delineate the range of applicability of the existing plug flow dispersion models. If the time scales of a tracer injection experiment are not sufficient for a tracer to traverse the bed radius and sample the velocity variations, this could give rise to persisting non-Fickian transients where the mean-square displacement of the tracer profile is not constant with time and the concentration profile deviates from the normal Gaussian distribution. These transients cannot be predicted by the conventional plug dispersion models. An extended axial non-Fickian macroscopic dispersion model is derived to describe the transient development of a solute tracer when injected into a fluid flowing through a cylindrical packed bed or empty tube and some non-Fickian effects in the dispersion process. The flow profile in beds packed with uniform particles exhibits radial non-uniformity due to the oscillatory variation in porosity because of the wall confinement (wall effect). Compared with the axial plug flow dispersion model, the extended model contains time-dependent coefficients such as the transient axial dispersion coefficient and higher order derivatives (higher than second order) of the cross-sectionally averaged concentration. Including them provides some insight on non-Fickian transport in the dispersion process. The model provides time criteria on the basis that the effelongitudinal dispersion coefficient in the packed bed reaches its asymptotic value and the non-Fickian transients will die out. Some experimental conditions in the literature were checked by these criteria and found to be either marginally satisfied, or not satisfied at all, which indicates that the Fickian concept is not valid. The model results for tracer dispersion in cylindrical packed beds show that the longitudinal dispersion coefficient converges to its asymptotic value on a time scale proportional to R2/(DT) where R is the column radius and (DT) is the area averaged lateral dispersion coefficient. The extended model encouraged study of the consequences of the additional dispersion terms in other applications such as the pulse spread in the field of capillary column inverse gas chromatography (CCIGC). CCIGC is used to evaluate the solute-polymer diffusion coefficient Dp and the partition coefficient K at infinite dilute conditions. The tube geometry in CCIGC is more complex than the conventional Taylor dispersion problem due to the polymer coating on the inside of the capillary wall. The extended CCIGC model presented in this study has advantages over the previous models by including the effects of Taylor dispersion and higher order derivatives of the pulse area-averaged concentration. Taylor dispersion effect causes more pulse spread in the longitudinal direction and by not including it in the CCIGC regression models may cause a significant error in the measured Dp values. The extended CCIGC model provides for the first time criteria on capillary dimensions for the transient coefficients (multiplying the second and higher order derivatives) to become constant and for the non-Fickian effects associated with the higher order derivatives to be neglected. Model results show that Taylor dispersion effect has a significant effect on the elution profiles at high values of Dp and/or low values of gas diffusion coefficients Dg and it can be used to increase the sensitivity range of the previous CCIGC models at extremely low and high Dp values.
5

The Study of Deflation in China in 1990's

Cheng, Tung-hsu 18 June 2005 (has links)
To resolve the inflation caused by overheated economy in 1992, China executed Macroscopic Control Policy to stabilize the fluctuation of price standard in 1993. It seemed to achieve the effort of controlling inflation. However, because of longtime Macroscopic Control Policy after Asian Financial Crisis, it resulted in negative impacts. CPI in China has been minus quantity for 39 months from October in 1997 to December in 2000. And CPI turned plus into minus from April in 1998 to January in 2000. And CPI turned plus into minus from April in 1998 to January in 2000. The growth rate of RPI is -2.6% and that of CPI is -0.8% in 1998. It declined to -3.0%(RPI) and -1.4%(CPI) in 1999. The growth rate of GDP has fallen down since 1992. The main purpose of this paper is to explore the reason of the deflation late in 1990 in China. I want to find out why deflation was happened in china? What is the main cause of deflation in china? What are the impacts and shocks to china economic growth by these causes? How are the impacts and shocks to china economic growth by these causes? The whole supply and demand and money contraction resulted in the downfall of GDP and CPI. To prevent the phenomena of overheated economy since 1993, most of investment moved away China because of Macroscopic Control Policy. Under this kind of situation, we couldn¡¦t say that the investments were excess. Therefore, the main reason isn¡¦t prices dropping caused by too much supply. China continued Deflation Policy after Asian Financial Crisis in 1997, so the speed of economy development decreased slowly. It also reduced the whole consumption, public spending, investment export, and money supply and demand. The effect of negative development resulted in the deflation of economy development.
6

A comparative study between Emme and Visum with respect to public transport assignment

Hildebrand, Cisilia, Hörtin, Stina January 2014 (has links)
Macroscopic traffic simulations are widely used in the world in order to provide assistance in the traffic infrastructure development as well as for the strategic traffic planning. When studying a large traffic network macroscopic traffic simulation can be used to model current and future traffic situations. The two most common software used for traffic simulation in Sweden today are Emme and Visum, developed by INRO respective PTV. The aim of the thesis is to perform a comparison between the software Emme and Visum with respect to the assignment of public transport, in other words how passengers choose their routes on the existing public transport lines. However, in order to make a complete software comparison the run-time, analysis capabilities, multi-modality, capacity to model various behavioural phenomena like crowding, fares etc. this will not be done in this comparison. It is of interest to study the differences between the two software algorithms and why they might occur because the Swedish Transport Administration uses Emme and the Traffic Administration in Stockholm uses Visum when planning public transport. The comparison will include the resulting volumes on transit lines, travel times, flow through specific nodes, number of boarding, auxiliary volumes and number of transits. The goal of this work is to answer the following objective: What are the differences with modelling a public transport network in Emme and in Visum, based on that the passengers only have information about the travel times and the line frequency, and why does the differences occur? In order to evaluate how the algorithms work in a larger network, Nacka municipality (in Stockholm) and the new metro route between Nacka Forum and Kungsträdgården have been used. The motivation for choosing this area and case is due to that it is interesting to see what differences could occur between the programs when there is a major change in the traffic network. The network of Nacka, and parts of Stockholm City, has been developed from an existing road network of Sweden and then restricted by "cutting out" the area of interest and then removing all public transportation lines outside the selected area. The OD-matrix was also limited and in order not to loose the correct flow of travellers portal zones was used to collect and retain volumes. To find out why the differences occur the headway-based algorithms in each software were studied carefully. An example of a small and simple network (consisting of only a start and end node) has been used to demonstrate and show how the algorithms work and why volumes split differently on the existing transit lines in Emme and Visum. The limited network of Nacka shows how the different software may produce different results in a larger public transport network. The results show that there are differences between the program algorithms but the significance varies depending on which output is being studied and the size of the network. The Visum algorithm results in more total boardings, i.e. more passengers have an optimal strategy including a transit. The algorithms are very similar in both software programs, since they include more or less parts of the optimal strategy. The parameters used are taken more or less into consideration in Emme and Visum. For example Visum will first of all focus on the shortest total travel time and then consider the other lines with respect to the maximum waiting time. Emme however, first focuses on the shortest travel time and then considers the total travel time for other lines with half the waiting time instead of the maximum wait time. This results in that less transit lines will be attractive in Emme compared to Visum. The thesis concludes that varying the parameters for public transport in each software algorithm one can obtain similar results, which implies that it is most important to choose the best parameter values and not to choose the "best" software when simulating a traffic network.
7

Once Upon a Genre: Distant Reading, the Newbery Medal, and the Affordances of Interdisciplinary Paradigms for Understanding Children’s Literature

Griffin, Melanie 16 March 2018 (has links)
Typical critical patterns for studying children’s literature, defined in this study as a written text intended for a reader up to the age of 14, make it difficult to chart generic change across a large corpus of texts. Traditionally, criticism of children’s literature focuses on cherry picked archetypes, exemplars, and the standout extraordinary. This study employs interdisciplinary methods and data sources from library science, education, and literary studies to create a method for analyzing a sample corpus of children’s literature more holistically vis-à-vis distant, macroscopic reading techniques. In this dissertation, I macroscopically read the corpus of Newbery Medal-winning texts in order to identify patterns of change in the genre of prized 20th century American children’s literature, seeking to animate this corpus of texts in different ways than is possible through microscopic analysis alone. The resulting analysis foregrounds the shared conventions of the text set, including descriptive elements, including bibliographic information, author information, publisher information, illustrative content, and length; structural elements, point of view, literary form, and select measures of text complexity; and thematic elements, including book summaries and subject analyses from a range of library, publisher, and social media databases. In addition, I consider various metrics for assessing popularity of the corpus as a whole and the ways in which popularity changes as time passes. Ultimately, in this dissertation I distantly read the corpus in conversation with existing critical understandings of the Newbery Medal, which previous critics generated using microscopic, close reading techniques, in order to investigate what changes with the introduction of distant methods. Distantly reading this corpus in conversation with existing critical understandings of the Newbery reveal that a more holistic approach to analysis paints a broader, more complete picture of the genre of prized children’s literature than microscopic, close reading alone does. Further, distant reading underscores the critical importance of explicit attention to methodology. The results that distant reading uncovers are inextricably intertwined with the methodological decisions made.
8

Infecção por helmintos gastrintestinais em cães (Canis familiaris, Linnaeus, 1758) errantes procedentes do município de Recife - PE

OSTERMANN, Auxiliadora de Moraes 11 February 2008 (has links)
Submitted by (edna.saturno@ufrpe.br) on 2016-08-11T12:45:21Z No. of bitstreams: 1 Auxiliadora de Moraes Ostermann.pdf: 1065380 bytes, checksum: 7562bc6d4f94fe6fff4c90d431b36942 (MD5) / Made available in DSpace on 2016-08-11T12:45:21Z (GMT). No. of bitstreams: 1 Auxiliadora de Moraes Ostermann.pdf: 1065380 bytes, checksum: 7562bc6d4f94fe6fff4c90d431b36942 (MD5) Previous issue date: 2008-02-11 / The gastrointestinal helminths assume importance for the aetiology of gastroenteritis in dogs, being the canine helminthosis a global and high prevalence problem, showing many of them, important zoonotic potential. The stray dogs are an important point in a program to control helminth infection in urban centers. They are generally excluded from any program, although assume great importance in the maintenance and dissemination of these parasites in urban areas. The more accurate knowledge about the epidemiology and prophylaxis of the most important parasites of dogs, particularly about its impact and prevalence, are fundamental to the adoption of appropriate prophylactic measures to protect human. It was proposed in this paper to evaluate the gastrointestinal helminth infection and techniques of diagnosis of infection in stray dogs from the municipality of Recife - Pernambuco State - Brazil. Strays dogs captured by the Center for Environmental Surveillance of the City of Recife - PE were used, totalizing 96 dogs. The animals were subjected to euthanasia and necropsy, and fecal samples were collected and submitted to the techniques of simple fluctuation and spontaneous sedimentation. It was realized macroscopic examination of the intern organs, whose changes were noted in files of necropsy, and performed the collection of adult gastrointestinal helminths for identification. The results showed positivity of 96.8% (93/96), with 83.3%, 14.6%, 30.2%, 6.3%, 28.1%, 34.4% and 2.1%, respectively for Ancylostoma caninum, A. braziliense, Toxocara canis, Toxascaris leonina, Dypilidium caninum and Spirocerca lupi. The methods of Willis, sedimentation and necropsy were significantly different only in the detection of Ancylostoma spp. Willis and sedimentation showed no differences among themselves for the other helminths. Macroscopic lesions were found in all organs of the gastrointestinal tract or organs involved in the parasitic phase of the life cycle of helminths, becoming the majority of them in bleeding, predominantly in the small intestine. / Os helmintos gastrintestinais assumem importância significativa na etiologia das gastrenterites em caninos, sendo as helmintoses de origem canina um problema mundial e de prevalência elevada, apresentando, muitas delas, importante potencial zoonótico. Um ponto importante em um programa de controle de verminose nos centros urbanos são os cães errantes. Eles estão geralmente excluídos de qualquer programa, embora assumam grande importância na manutenção e disseminação dessas parasitoses no meio urbano. O conhecimento mais acurado sobre epidemiologia e a profilaxia dos parasitos mais importantes de cães, particularmente sobre as suas incidências e prevalências, são fundamentais para a adoção de medidas profiláticas adequadas para a proteção humana. Propôs-se neste trabalho avaliar a infecção por helmintos gastrintestinais e as técnicas de diagnóstico da infecção em cães errantes procedentes do município de Recife – PE. Foram utilizados 96 cães errantes, apreendidos pelo Centro de Vigilância Ambiental da Cidade do Recife – PE (CVA/PE). Os animais foram submetidos à eutanásia e necropsia, sendo coletadas amostras fecais que foram submetidas às técnicas de flutuação simples e sedimentação espontânea. Realizou-se exame macroscópico dos órgãos, cujas alterações foram anotadas em fichas de necropsia, efetuou-se, ainda a coleta de helmintos gastrintestinais adultos para identificação. Os resultados apontaram positividade de 96,9% (93/96), sendo 83,3%, 14,6%, 30,2%, 6,3%, 28,1%, 34,4%, 2,1%, respectivamente para Ancylostoma caninum, A. braziliense, Toxocara canis, Toxascaris leonina, Trichuris vulpis, Dypilidium caninum e Spirocerca lupi. Os métodos de Willis, sedimentação e necropsia foram significativamente diferentes entre si apenas na detecção de infecção por Ancylostoma spp. Willis e sedimentação não apresentaram diferenças entre si para os demais helmintos. Lesões macroscópicas foram evidenciadas em todos os órgãos do trato gastrintestinal ou em órgãos envolvidos na fase parasitária do ciclo biológico dos helmintos, constituindo-se a maioria delas em hemorragias, predominantemente no intestino delgado.
9

Coerência quântica macroscópica em sistemas ferromagnéticos / Macroscopic quantum coherence in ferromagnetic systems

Paula, Fagner Muruci de, 1983- 19 August 2018 (has links)
Orientador: Amir Ordacgi Caldeira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-19T09:51:01Z (GMT). No. of bitstreams: 1 Paula_FagnerMurucide_D.pdf: 4858080 bytes, checksum: a43c455fc79aac38fc3e9bd9d81abe32 (MD5) Previous issue date: 2011 / Resumo: Por muitas décadas, fenômenos quânticos foram observados com partículas microscópicas, tais como átomos, elétrons e fótons. No entanto, avanços na fabricação e controle de sistemas físicos com dimensões extremamente reduzidas vêm permitindo a manifestação de eventos quânticos em proporções gigantescas. Por exemplo, existem evidências de superposições quânticas com uma supercorrente composta por bilhões de elétrons num SQUID (Superconducting Quantum Interference Device). Motivados por tais evidências, nosso objetivo reside na busca de novos dispositivos capazes de exibir efeitos quânticos macroscópicos. Em particular, estamos interessados em sistemas ferromagnéticos que manifestem CQM (Coerência Quântica Macroscópica), isto é, ferromagnetos nos quais o campo de magnetização tunela periodicamente no tempo entre dois estados topologicamente distintos e degenerados. Nesta tese, sugerimos dois dispositivos: um ?o ferromagnético no qual uma parede de domínio tunela entre dois centros de aprisionamento arti?ciais; e um MQUID (Magnetic Quantum Interference Device), isto é, um análogo magnético do SQUID que permite efeitos de tunelamento com uma ¿supercorrente¿ formada por vórtices de spin. Esses dispositivos são úteis não só na exploração dos limites de validade da mecânica quântica, mas também abrem novas possibilidades de implementação de um bit quântico / Abstract: For many decades, quantum phenomena were observed with microscopic particles, such as atoms, electrons and photons. However, advancements in manufacture and control of physics systems with very small dimensions have allowed verifying quantum events in large proportions. For instance, there are evidences of quantum superposition with a supercurrent formed by billions of electrons on a SQUID (Superconducting Quantum Interference Device). Such evidences have driven our work in a way to investigate new devices that are capable to exhibit macroscopic quantum effects. In particular, we are interested in ferromagnetic systems that present MQC (Macroscopic Quantum Coherence), in other words, ferromagnets in which the magnetization ?eld tunnels periodically in time between two distinct and degenerate topological states. In this thesis, we have suggested two devices: a ferromagnetic wire in which a domain wall tunnels between two arti?cial pinning centers; and a MQUID (Magnetic Quantum Interference Device) that is a magnetic device analogous to SQUID that permit quantum tunneling effects with a supercurrent formed by spin vortices. These devices are useful to explore the limits of validity of quantum mechanics, as well they open new possibilities to put into operation a quantum bit / Doutorado / Física / Doutor em Ciências
10

Using the Macroscopic Fundamental Diagram to Characterize the Traffic Flow in Urban Network

Ahmed, Istiak 04 February 2016 (has links)
Various theories have been proposed to describe vehicular traffic flow in cities on an aggregate level. This dissertation work shows that a number of MFDs exist in an urban network. The number of MFDs basically indicate the existence of different levels of service on different network routes. It also demonstrate that the modification of control strategy can optimize the signal timing plan for the links with high congestion and spillbacks. With the proposed control strategy, the location of points are shifted from lower MFDs to upper MFDs which means the congestion are reduced and the overall network traffic flow operation is improved. In this thesis, the emergency vehicle preemption (EVP) operation is also evaluated by using the MFDs. The concept of MFD can help to illustrate the effect on various types of roads due to EVP operation. The results show that the volume of links along the emergency route is increased and the volume of other links closed to the emergency route is decreased due to preemption. The researchers and practitioners can apply the proposed approach to identify the affected links and minimize the total network delay during EVP. / Master of Science

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