Tesi sul tema "Internal lengths"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Internal lengths.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Internal lengths".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Chamma, Layal. "Effets des longueurs internes microstructurales sur le comportement mécanique des aciers ferritiques : caractérisations expérimentales et modélisation micromécanique". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0350.
Abstract (sommario):
Les longueurs internes microstructurales jouent un rôle important sur le comportement mécanique local et macroscopique des aciers. Ces longueurs internes correspondent notamment à la taille des grains et à une couche de densités de "dislocations géométriquement nécessaires" (GND) accumulées en raison des incompatibilités de réseau cristallin crées autour des joints de grains (ou des joints de phase), d'une épaisseur notée λ, produite pendant la déformation plastique. Dans cette étude, un acier ferritique polycristallin monophasé à faible teneur en carbone (Al-k) produit par ArcelorMittal a été étudié, en considérant des échantillons non déformés et pré-déformés à différents niveaux de déformation en traction. La densité de GND a été estimée à partir de cartes EBSD bidimensionnelles (2D) en considérant les cinq composantes du tenseur de Nye disponibles et calculées à partir des courbures du réseau. Des essais de nanoindentation instrumentée ont ensuite été réalisés avec une pointe Berkovich et une charge de 1 mN. La densité totale de dislocations a été estimée à l'aide d'un modèle mécanistique basé sur les mesures de nanodureté. Une étude combinée utilisant à la fois l'EBSD-2D et la nanoindentation instrumentée a alors été proposée afin de quantifier l'existence et l'évolution de la longueur interne λ de la zone affectée par les joints de grains. Tout d'abord, une étude locale a été réalisée sur deux paires de grains provenant d'une éprouvette pré-déformée en traction à 18% de déformation plastique. Cette étude a montré une corrélation spatiale claire entre la densité totale de dislocations déduite des mesures de nanodureté et la densité de GND obtenue par EBSD-2D. De forts gradients spatiaux de densités de GND et de densités totales de dislocations ont été observés sur une des paires de grains étudiée. Une couche d'épaisseur λL proche de 2µm a été trouvée par les deux techniques. Cependant, l'étude de l'évolution locale de λL pour un même grain avec la déformation plastique n'a pas été possible par les deux techniques. De plus, l'étude locale souffrait d'un manque de représentation statistique. Par conséquent, afin d'améliorer la description de la longueur interne λ tout au long de la déformation plastique, nous avons proposé une analyse statistique basée sur toutes les données obtenues par EBSD-2D et par nanoindentation pour s'éloigner du choix arbitraire des grains. Ensuite, une analyse statistique des données expérimentales a été réalisée. Le but était de déterminer une longueur interne statistique λS à chaque taux de déformation plastique par les deux méthodes expérimentales. Les résultats obtenus par les deux méthodes ont confirmé l'existence statistique d'un gradient de densités de dislocations aux joints de grains qui nous a permis de déterminer une longueur λS évolutive au cours de la déformation plastique. Par ailleurs, les résultats expérimentaux ont montré que les grains ferritiques dans l'acier Al-k pouvaient être divisés en deux régions mécaniquement différentes. La première région est située à proximité du joint de grains, où un gradient de densité de dislocations a été clairement observé et s'étend en moyenne sur la distance λS. La deuxième région est l'intérieur du grain où aucune variation marquée des densités de dislocations n'a été reportée en moyenne. Les mesures expérimentales ont été utilisées pour alimenter une nouvelle approche à champs moyen intégrant les longueurs internes microstructurales (ACMLI) capable de capter les effets de taille de grains. Cette nouvelle approche intègre directement l'évolution de la longueur interne λS mesurée expérimentalement. En plus de représenter fidèlement le comportement macroscopique, les prédictions des densités de dislocations à plusieurs niveaux de déformation comparée aux mesures expérimentales et une évolution réaliste des champs mécaniques locaux dans chaque phase ont été obtenusMicrostructural internal lengths play an important role on the local and macroscopic mechanical behavior of steels. These internal lengths correspond, in particular, to the grain size and to the thickness λ of the layer of "geometrically necessary dislocations" (GNDs) accumulated at grain boundaries (GBs) due to crystal lattice incompatibilities, produced during plastic deformation. In this study, a single-phase polycrystalline ferritic steel with low carbon content (Al-k) produced by ArcelorMittal was investigated through the analysis of undeformed and pre-deformed samples at different tensile deformations. The GND density was estimated from two-dimensional EBSD (2D) maps by considering the available five components of the Nye tensor computed from lattice curvatures. Instrumented nanoindentation tests were then performed with a Berkovich tip and a load of 1 mN. The total dislocation densities were estimated using a mechanistic model from the nanohardness measurements. A combined study using both 2D-EBSD and instrumented nanoindentation was then proposed to quantify the existence and the evolution of the internal length λ of the GB affected zone. First, a local study was performed on two pairs of grains from a specimen pre-deformed at 18% of plastic deformation. This study showed a clear spatial correlation between the total dislocation densities deduced from nanohardness measurements and the GND densities obtained from 2D-EBSD. Strong spatial gradients of GND and total dislocation density were observed on one of the studied grain pairs. A layer of thickness λL around 2µm was found by both techniques. However, it was not possible to do an in-situ study of the local evolution of λL with plastic deformation for a same grain using the both techniques. Moreover, the local study was limited owing to a lack of statistical representation. Therefore, in order to improve the description of the internal length evolution during the plastic deformation, a statistical analysis based on all 2D-EBSD and nanoindentation data was proposed. The goal was to determine a statistical internal length λS at each plastic strain by both experimental methods. The results obtained by these methods confirmed the statistical existence of a gradient of dislocation densities at GBs. As well, it allowed us to determine an evolving internal length λS during plastic deformation. Furthermore, the experimental results showed that the ferritic grains in Al-k steel could be divided into two mechanically different regions. The first region is located near the GBs, where a dislocation density gradient was clearly observed to spread over the characteristic distance λS. The second region is the interior of the grain where no marked variation in average dislocation density was found. The experimental measurements were used to improve a new Internal Length Mean Field (ILMF) approach capable to capture grain size effects. This new approach directly integrates the evolution law of the internal length λS. In addition to the prediction of the macroscopic behavior, a good estimate of the evolution of dislocation densities compared to the experimental measurements and a realistic evolution of the local fields in each phase were obtained
2
Jarmolowicz, David P. "The fixed-interval scallop effects of reinforcer magnitude and interval length /". Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10316.
Abstract (sommario):
Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains vii, 50 p. : ill. Includes abstract. Includes bibliographical references (p. 37-41).
3
deCamp, Philip Draper. "The efficiency of nonparametric inference methods based on confidence interval lengths". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/25510.
4
Bort, Anja [Verfasser]. "The Role of External and Internal Stress on Telomere Length Regulation / Anja Bort". Konstanz : KOPS Universität Konstanz, 2017. http://d-nb.info/1200354907/34.
5
Liu, Luchen. "Interval Estimation for Binomial Proportion, Poisson Mean, and Negative –binomial Mean". Thesis, Uppsala universitet, Statistiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-175767.
Abstract (sommario):
This paper studies the interval estimation of three discrete distributions: thebinomial distribution, the Poisson distribution and the negative-binomialdistribution. The problem is the chaotic behavior of the coverage probabilityfor the Wald interval. To solve this problem, alternative confidence intervals areintroduced. Coverage probability and expected length are chosen to be thecriteria evaluating the intervals.In this paper, I firstly tested the chaotic behavior of the coverageprobability for the Wald interval, and introduced the alternative confidenceintervals. Then I calculated the coverage probability and expected length forthose intervals, made comparisons and recommended confidence intervals forthe three cases. This paper also discussed the relationship among the threediscrete distributions, and in the end illustrated the applications on binomialand Poisson data with brief examples.
6
Gosselin, Frederic. "Why do we SLIP to the basic level? : a formal model". Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312669.
7
Hauck, João Vitor de Sá. "Iterative edge length interval constraining in triangular meshes based on local parametrization". Universidade Federal de Juiz de Fora (UFJF), 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/4827.
Abstract (sommario):
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-06T13:21:41Z
No. of bitstreams: 1
joaovitordesahauck.pdf: 33226275 bytes, checksum: b7a8ed469369e9bbccd22738ced13ab0 (MD5)Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-06-06T14:07:12Z (GMT) No. of bitstreams: 1 joaovitordesahauck.pdf: 33226275 bytes, checksum: b7a8ed469369e9bbccd22738ced13ab0 (MD5)
Made available in DSpace on 2017-06-06T14:07:12Z (GMT). No. of bitstreams: 1 joaovitordesahauck.pdf: 33226275 bytes, checksum: b7a8ed469369e9bbccd22738ced13ab0 (MD5) Previous issue date: 2015
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Malhas com restrições no comprimento das arestas são úteis para diversas aplicações, especialmente para simulações de processos químicos e físicos. Este trabalho apresenta um método iterativo para remalhar uma malha triangular arbitraria de variedade 2 em uma malha com o comprimento de todas as arestas dentro de um intervalo de restrição definido pelo usuário. O método usa operações estelares para ajustar a quantidade de vértices e triângulos no modelo e para melhorar a valência dos vértices. Ele também aplica o operador Laplaciano em um espaço paramétrico local para melhorar a distribuição de vértices sobre a superfície. Propõe-se, uma otimização não linear, aplicada localmente, para os casos em que a malha é praticamente regular. Perdas geométricas são evitadas pela realização de uma projeção sobre a superfície original. O método proposto resulta em uma malha praticamente regular, com os vértices distribuídos uniformemente sobre a superfície. A dual da malha é usada em simulações de nano estruturas de carbono como uma aplicação do método. A principal contribuição deste trabalho é uma nova abordagem para restringir explicitamente o comprimento das arestas em um intervalo dado. Nosso método ainda garante baixa perda global de geometria e baixo custo de memória em comparação com métodos disponíveis na literatura.
Meshes with constraints in the edge length are useful for several applications, spe-cially for chemical and physical simulations. This work presents an iterative method for remeshing an arbitrary triangular 2-manifold mesh into a mesh with all edge lengths within an user-defined constraining interval. The method uses stellar operations to adjust the amount of vertices and triangles in the model and for improving the valence of the vertices. It also applies the Laplacian operator in a local parametric space to improve the distribution of the vertices over the surface. We propose a nonlinear optimization, locally applied, for cases in which the mesh is almost regular. Geometric losses are prevented by performing a projection over the original surface. Our method results in a nearly regu-lar mesh, with vertices uniformly distributed over the surface. The dual of the mesh is used in simulations of carbon nanostructures as an application of the method. The main contribution of this work is a new approach for constraining the edge length within an explicitly given interval. Our method also ensures lower global geometry losses and lower memory cost in comparison to methods available in the literature.
8
Lee, Sang Hyun. "Modelling growth and yield of Douglas-fir using different interval lengths in the South Island of New Zealand". Thesis, University of Canterbury. Forestry, 1998. http://hdl.handle.net/10092/7204.
Abstract (sommario):
This study describes several refinements and improvements in whole stand growth and yield modelling of Douglas-fir grown in four regions of the South Island of New Zealand, namely Canterbury, Nelson, Southland and Westland. Modelling growth and forecasting yields are necessary for providing adequate tools with which to manage wood production from forests.
The study comprised three major components: 1) development of whole stand growth and yield models with data sets of various interval lengths; 2) cross fitting models with different data sets reciprocally; and 3) check estimates using a growth and yield model derived from a data set free of auto-correlation.
The methodology emphasised in developing the equations in this study involved rearrangement of the data to reflect different interval lengths among re-measurements for modelling purposes. Modification of data sets allowed an investigation into which growth intervals should be used to obtain the least biased models overall, and efficiently. The approach involved fitting single equations to each of three state variables, mean top height (h1OO), basal area/ha (0) and stocking/ha (N). Differences in growth trajectories across the four regions were identified and incorporated into single variable equations using dummy variables for improving the fitting of mean top height (h1OO), basal area/ha (0), and stocking/ha (N) equations. The main finding from this study was the level of improvement in making predictions through adoption of a mixed interval projection equation strategy compared with other options.
Examining consistency among the predicting equations which had been developed from the different interval data sets, involved testing each form of model individually for all the data sets. The models based on mixed intervals were found to fit well for all the other interval length data sets. A subset of uncorrelated data was then created by selecting one re-measurement from each permanent sample plot (PSP), which was then used to validate the appropriateness of the equations derived from the full data sets, in order to overcome problems of dealing with correlated data. Coefficients for each of the equations for mean top height, basal area/ha and stocking/ha which were derived from this check data set were found to be very similar to the regression coefficients obtained from the full data set.
Although the growth models developed in this study may require further examination, they do provide a very useful guide for selecting appropriate re-measurement interval lengths to derive satisfactory models which are the least biased overall. It is strongly recommended that modellers in the future adopt a mixed interval strategy as one data set option to evaluate.
9
Goda, Ibrahim. "Micromechanical models of network materials presenting internal length scales : applications to trabecular bone under stable and evolutive conditions". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0055/document.
Abstract (sommario):
Des méthodes micromécaniques spécifiques ont été développées pour la détermination du comportement effectif de matériaux cellulaires dotés d’une architecture discrète à l’échelle microscopique. La méthode d’homogénéisation discrète a été appliquée à des structures tissées monocouches ainsi qu’à l’os trabéculaire. La topologie discrète initiale de ces milieux est remplacée à l’échelle mésoscopique par un milieu effectif anisotrope micropolaire, qui rend compte des effets d’échelles observés. Ces méthodes d’homogénéisation permettent d’accéder à des propriétés classiques et non classiques dont la mesure expérimentale est souvent difficile. Des modèles 3D ont été développé afin de décrire la rupture fragile et ductile de l’os trabéculaire, incorporant des effets de taille des surfaces d’écoulement plastique. Nous avons construit par des analyses éléments finis de la microstructure de l’os trabéculaire un milieu de substitution 3D homogène, orthotrope de type couple de contraintes, sur la base d’une équivalence en énergie. Les tissus osseux ont la capacité d’adapter leur densité locale et leur taille et forme aux stimuli mécaniques. Nous avons développé des modèles de remodelage interne et externe dans le cadre de la thermodynamique des processus irréversibles, aux échelles cellulaire et macroscopique. Finalement, le remodelage interne anisotrope a été couplé à l’endommagement de fatigue, dans le cadre de la théorie continue de l’endommagementA methodology based on micromechanics has been developed to determine the effective behavior of network materials endowed with a discrete architecture at the microscopic level. It relies on the discrete homogenization method, which has been applied to textile monolayers and trabecular bones. The initially discrete topology of the considered network materials results after homogenization at the mesoscopic level in anisotropic micropolar effective continuum, which proves able to capture the observed internal scale effects. Such micromechanical methods are useful to remedy the difficulty to measure the effective mechanical properties at the intermediate mesoscopic level scale. The bending and torsion responses of vertebral trabecular bone beam specimens are formulated in both static and dynamic situations, based on the Cosserat theory. 3D models have been developed for describing the multiaxial yield and brittle fracture behavior of trabecular bone, including the analysis of size-dependent non-classical plastic yield. We have constructed by FE analyses a homogeneous, orthotropic couple-stress continuum model as a substitute of the 3D periodic heterogeneous cellular solid model of vertebral trabecular bone, based on the equivalent strain energy approach. Bone tissues are able to adapt their local density and load bearing capacities as well as their size and shape to mechanical stimuli. We have developed models for combined internal and external bone remodeling in the framework of the thermodynamics of irreversible processes, at both the cellular and macroscopic levels. We lastly combined anisotropic internal remodeling with fatigue continuum damage
10
Chavarria, Pablo C. "Reduction of Confidence Interval Length for Small-Normal Data Sets Utilizing Bootstrap and Conformal Prediction Methods". Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10840988.
Abstract (sommario):
It is of common practice to evoke a t-confidence interval for estimating the mean of a small data set with an assumed Normal distribution. These t-intervals are known to be wide to account for the lack of information. This thesis will focus on exploring ways to reduce the length of the interval, while preserving the level of confidence. Simulated small normal data sets will be used to analyze a combination of Bootstrapping and Conformal Prediction methods, while investigating measures of spread, such as standard deviation, kurtosis, excess CS kurtosis, skewness, etc. to create a criterion for when this combination of methodologies will greatly reduce the interval length. The goal is to be able to use the insight simulated data have to offer in order to apply to real world data. If time permits, a further look into the theory behind the results will be explored.
11
Liu, Huabing, Marcel Nogueira D’Eurydice, Sergei Obruchkov e Petrik Galvosas. "Pore length scales and pore surface relaxivity of sandstone determined by internal magnetic fields modulation at 2 MHz NMR". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-178759.
Abstract (sommario):
Pore length scales and pore surface relaxivities of sandstone were studied on a 2 MHz Rock Core Analyzer in this work. To determine the pore length scales of rock cores, high eigenmodes of diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields B in. The results were confirmed by a 64 MHz NMR system. Furthermore, this methodology was combined with relaxometry measurements , which provides the two-dimensional correlation of pore length with relaxation time and yield information on the surface relaxivity of rock cores. The estimated surface relaxivities were compared with the results from an independent NMR method.
12
Liu, Huabing, Marcel Nogueira D’Eurydice, Sergei Obruchkov e Petrik Galvosas. "Pore length scales and pore surface relaxivity of sandstone determined by internal magnetic fields modulation at 2 MHz NMR". Diffusion fundamentals 22 (2014) 7, S. 1-5, 2014. https://ul.qucosa.de/id/qucosa%3A13487.
Abstract (sommario):
Pore length scales and pore surface relaxivities of sandstone were studied on a 2 MHz Rock Core Analyzer in this work. To determine the pore length scales of rock cores, high eigenmodes of diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields B in. The results were confirmed by a 64 MHz NMR system. Furthermore, this methodology was combined with relaxometry measurements , which provides the two-dimensional correlation of pore length with relaxation time and yield information on the surface relaxivity of rock cores. The estimated surface relaxivities were compared with the results from an independent NMR method.
13
Panchal, Hemang B., Kalpit Devani, Shimin Zheng, Sellasi Denutsui, Sukhdeep Bhogal, Abdul Ahad Khan, Syed Imran Zaidi, Thomas Helton, Nirat Beohar e Timir K. Paul. "Impact of Chronic Kidney Disease on Length of Hospital Stay and Cost among Patients Admitted with Acute ST Elevation Myocardial Infarction: A Nationwide Inpatient Sample 2012-2014". Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/6303.
14
Wu, Lai Man Natalie. "Role of Periaxin dimerization in peripheral myelination". Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/9610.
Abstract (sommario):
In the peripheral nervous system (PNS), Schwann cells ensheathe and myelinate axons to promote saltatory conduction of nerve impulses. Close interactions between Schwann cells and axons, and Schwann cells and the basal lamina are essential for the regulation of Schwann cell development and function. Myelinating Schwann cells are highly polarized radially and longitudinally for specifying distinct domains in the axon, which is required for fast action potential propagation. In addition, the Schwann cell cytoplasm is organized into discrete compartments, called Cajal bands, which contain different dystrophin-glycoprotein complexes that are believed to segregate the Schwann cell plasma membrane into appositions between the outer surface of the myelin sheath and the cytoplasmic face of the Schwann cell plasma membrane. Periaxin is expressed in myelinating Schwann cells, and homodimerizes at its PDZ domain to form a transmembrane complex with dystrophin-related protein 2 (DRP2) and dystroglycan. This PDG complex is concentrated at the appositions, and is essential for myelin sheath maintenance and stability in the mature PNS. In mice lacking Periaxin, an intact myelin sheath is formed but subsequently becomes unstable. Periaxin-null Schwann cells are also shorter, which has been proposed to result in a reduction in nerve conduction velocity. This thesis is a study of how Periaxin PDZ domain dimerization contributes to the regulation of PDG complex stability, apposition maintenance, Schwann cell internodal distance and myelin stability. I have studied the function of Periaxin by generating a conditional mutant mouse that lacks the PDZ domain, which is predicted to abrogate dimerization. In these mutants, DRP2 is severely depleted and appositions containing DRP2 fail to form. Mutant Schwann cells also have disrupted Cajal bands and shorter internodal lengths. In the mature peripheral nerves, mutant mice display a peripheral neuropathy characterized by hypermyelination with focally folded myelin. Nerve conduction velocity, motor coordination and sensory function were also studied in these mutant mice. Taken together, these data suggest that dimerization of the Periaxin PDZ domain is required for the stabilization of the PDG and appositions, and regulation of Schwann cell elongation and myelin maintenance. By analyzing a tamoxifen-inducible conditional mouse lacking Periaxin’s PDZ domain in mature myelinating Schwann cells, this work also shows that Periaxin dimerization is essential for maintaining Schwann cell compartmentalization and myelin stability in adult nerves. Finally, studies of single amino acid mutations of the Periaxin PDZ reveal that subtle changes in the structure of the PDZ domain can abrogate dimerization,and a possible mechanism for PDZ-PDZ homodimerization of Periaxin is proposed.
15
Butcher, Daniel S. A. "Influence of asymmetric valve timing strategy on in-cylinder flow of the internal combustion engine". Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/23327.
Abstract (sommario):
Variable Valve Timing (VVT) presents a powerful tool in the relentless pursuit of efficiency improvements in the internal combustion engine. As the valves have such ultimate control over the gas exchange processes, extensive research effort in this area has shown how valve event timing can be manipulated to reduce engine pumping losses, fuel consumption and engine out emissions. Pumping losses may be significantly reduced by use of throttleless strategies, making use of intake valve duration for load control, while alternative cycles such as the Miller cycle allow modification of the effective compression ratio. More recently, the value of single valve operation in part load conditions is exploited, bringing with it the concept of asymmetric valve lifts. Work in this area found the side effect of asymmetric valve operation is a significant change in the behaviour of the in-cylinder flow structures, velocities and turbulence intensity. Work presented in this thesis exploits asymmetric valve strategies to modify the in-cylinder flow conditions. The Proper Orthogonal Decomposition (POD) is a method employed in the fluids dynamics field to facilitate the separation of coherent motion structures from the turbulence. In the presented work, the application of POD to in-cylinder flow analysis is further developed by the introduction of a novel method for identifying the POD modes representative of coherent motion and those representative of the turbulence. A POD mode correlation based technique is introduced and developed, with the resulting fields showing evidence of coherence and turbulence respectively. Experimental tests are carried out using a full length optically accessible, single cylinder research engine equipped with a fully variable valve train (FVVT) to allow full control of both valve timing and lift. In-cylinder flow is measured through the use of Particle Image Velocimetry (PIV) at several crank angle timings during the intake stroke whilst the engine is operated under a range of asymmetric valve strategies. The exhaust valves and one intake valve have their respective schedules fixed, while the second intake valve schedule is adjusted to 80\%, 60\%, 40\%, 20\%, 0\% lift. The resulting PIV fields are separated into coherent motion and turbulence using the developed technique, allowing for analysis of each constituent independently. The coherent element gives insight to large scale flows, often of the order of magnitude of the cylinder. These structures not only give a clear indication of the overall motion and allow assessment of flow characteristics such as swirl and tumble ratio, but the variation in the spatial location of these structures provides additional insight to the cyclic to cycle variation (CCV) of the flow, which would not otherwise be possible due to the inclusion of the turbulent data. Similarly, with the cyclic variation removed from the turbulent velocity field, a true account of the fluctuating velocity, u' and derived values such as the Turbulent Kinetic Energy (TKE) may be gained. Results show how manipulation of a one intake valve timing can influence both the large scale motions and the turbulence intensity. By the reduction of lift, the swirl ratio is increased almost linearly as the typical counter-rotating vortex pair becomes asymmetric, before a single vortex structure is observed in the lowest lift cases. A switching mechanism between the two is identified and found to be responsible for increased levels of CCV. With the reduction in lift, TKE is observed not only to increase, but change the spatial distribution of turbulence. Of course, the reduction in valve lift comes with the penalty of a reduced valve curtain area. However, it was identified both in literature and throughout this study that the reduction in lift did not negatively influence the engine breathing as the same trapped mass was achieved under all cases with no adjustment of manifold pressure. While literature shows both bulk motion and turbulence are key in liquid fuel break-up during the intake stroke, the mixing effects under port-injected natural gas were investigated experimentally using Laser Induced Fluorescence (LIF). The valve strategy was found to have no significant effect on the mixture distribution at the time of spark.
16
Tantasuparuk, Wichai. "Sow reproductive performance in Thailand : effects of climate, breed, parity, lactation length, weight loss during lactation and weaning-to-service interval /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5938-9.pdf.
17
Elhfnawy, Ahmed [Verfasser], e Jens [Gutachter] Volkmann. "Relation between the length of the internal carotid stenotic segment and ischemic cerebrovascular events as well as white matter lesion load / Ahmed Elhfnawy ; Gutachter: Jens Volkmann". Würzburg : Universität Würzburg, 2019. http://d-nb.info/1200856074/34.
18
TEDONE, ENZO. "LEUKOCYTE TELOMERE LENGTH, TELOMERASE ACTIVITY AND PREVALENCE OF AGE-RELATED DISEASES IN SEMISUPERCENTENARIANS, CENTENARIANS AND CENTENARIANS' OFFSPRING". Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/263860.
Abstract (sommario):
Centenarians and their offspring are increasingly considered a useful model to study and characterize the mechanisms underlying healthy aging and longevity. The aim of this project is to compare the prevalence of age-related diseases, telomere length (TL), a marker of biological age and mortality, and telomerase activity, an enzyme able to lengthen telomeres, across five groups of subjects: semisupercentenarians (SSCENT) (105–109 years old), centenarians (CENT) (100–104 years old), centenarians' offspring (CO), age- and gender-matched offspring of parents who both died at an age in linewith life expectancy (CT) and age- and gender-matched offspring of both non-long-lived parents (NLO). Information was collected on lifestyle, past and current diseases, medical history and medication use. SSCENT displayed a lower prevalence of acute myocardial infarction (p = 0.027), angina (p = 0.016) and depression (p = 0.021) relative to CENT. CO appeared to be healthier compared to CT who, in turn, displayed a lower prevalence of both arrhythmia (p = 0.034) and hypertension (p = 0.046) than NLO, characterized by the lowest parental longevity. Interestingly, CO and SSCENT exhibited the longest (p b 0.001) and the shortest (p b 0.001) telomeres respectively while CENT showed no difference in TL compared to the younger CT and NLO. Up to now, telomerase activity was assessed only in SSCENT and CO, with the latter showing a significantly lower telomerase activity compared to SSCENT (p=0.031). Our results strengthen the hypothesis that the longevity of parents may influence the health status of their offspring. Moreover, our data also suggest that both CENT and their offspring may be characterized by a better TL maintenance which, in turn, may contribute to their longevity and healthy aging. The observation that SSCENT showed considerable shorter telomeres compared to CENT may suggest a progressive impairment of TL maintenance mechanisms over the transition from centenarian to semisupercentenarian age. Accordingly, the higher level of telomerase activity found in SSCENT may be a compensatory mechanism induced by an accelerated telomere disfunction.
19
Barcelos, Daniel de Souza. "Gerenciamento do fluxo de pacientes : criação de uma unidade de curta permanência em um Serviço de Medicina Interna". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/72937.
Abstract (sommario):
Diversos serviços de saúde no Brasil vem apresentado episódios de superlotação, em um contexto onde os recursos são limitados. A redução do tempo de permanência em internações hospitalares tem como consequência direta a disponibilização de mais leitos-dia. O gerenciamento e melhoria do fluxo de pacientes ao longo das internações hospitalares é importante, sendo que o uso eficiente dos leitos pode acontecer devido a uma série de fatores. Estudos demonstram que equipes multidisciplinares podem realizar uma assistência de qualidade, reduzindo custos e o tempo em que os pacientes permanecem internados, sem impacto na reinternação ou mortalidade. Também há trabalhos que apontam a eficácia de unidades dedicadas ao atendimento de doenças específicas. A admissão de pacientes dentro de critérios bem definidos aumenta o giro de leitos. Com o objetivo de analisar se a equipe multidisciplinar Medicina Interna – Emergência (MIE) poderia contribuir para a redução do tempo de permanência hospitalar dos pacientes portadores de doenças prevalentes, sem alterar os indicadores de reinternação e mortalidade, o presente estudo experimental, controlado, não-randomizado, comparou o período pré e pós-intervenção, ou seja, a criação de uma Unidade de Curta Permanência no Serviço de Medicina Interna, do Hospital de Clínicas de Porto Alegre (HCPA). Foram analisadas internações ocorridas através da Emergência do HCPA, de pacientes com 14 anos ou mais, com as doenças prevalentes classificadas conforme grupos do CID-10 (J09-J018; J40-J47; N30-N39; I30-I52; I60-I69; B20-B24; C15-C26; A30-A49; e E10-E14), no período compreendido entre 01 de dezembro de 2008 a 30 de novembro de 2010 (n = 11040). Os resultados do estudo demonstram que após a criação da equipe E-MEI e a sua unidade de curta permanência, houve uma redução do tempo de permanência dos pacientes internados pelas causas selecionadas (antes: 10,89 ± 13,17 dias, após: 9,47 ± 11,24 dias, p = 0,006), e uma diminuição mais acentuada nas internações do Serviço de Medicina Interna [antes (n = 680): 14,33 ± 14,57 dias, após (n = 1243): 9,77 ± 10,62 dias, p = 0,000]. Não ocorreu alteração na taxa de mortalidade de todos os pacientes admitidos para as causas selecionadas [antes (n = 3800): 11,3%, após (n = 3958): 11,8% p = 0,123]. Também não houve alteração na taxa de reinternação de 7 dias na amostra estudada [antes (n = 3369): 7,2%, depois de (n = 3491): 6,7%, p = 0,407].Several health services in Brazil has shown episodes of overcrowding, in a context where resources are limited. Reducing the length of stay in hospital has as a direct consequence the provision of more beds-day. Managing and improving the flow of patients throughout the hospital is important, and the efficient use of beds can happen due to a number of factors. Studies have shown that multidisciplinary teams can perform quality care, reducing costs and the time patients remain hospitalized, with no impact on mortality or rehospitalization. There are also studies that show the effectiveness of units dedicated to the treatment of specific diseases. The admission of patients into well-defined criteria increases the turnover of beds. With the objective of analyzing the multidisciplinary team Internal Medicine – Emergency, could help to reduce the length of hospital stay of patients with diseases prevalent, without changing the indicators of rehospitalization and mortality, the present study experimental, controlled, not -randomized study compared the pre-and post-intervention, ie the creation of a Short Stay Unit in the Department of Internal Medicine, Hospital de Clinicas de Porto Alegre (HCPA). We analyzed hospital admissions through the Emergency HCPA, for patients aged 14 years or older with prevalent disease groups classified according to the ICD-10 (J09-J018, J40-J47, N30-N39, I30-I52, I60-I69; B20-B24, C15-C26, A30-A49, and E10-E14), during the period from December 1, 2008 to November 30, 2010 (n = 11,040). The study results show that after the creation of the multidisciplinary team, and its Short Stay Unit, there was a reduction in the length of stay of inpatients by selected causes (before: 10.89 ± 13.17 days after: 9 47 ± 11.24 days, p = 0.006) and a greater reduction in hospitalizations Service of Internal Medicine [before (n = 680): 14.33 ± 14.57 days after (n = 1243): 9, 77 ± 10.62 days, p = 0.000]. No change in the mortality rate of all patients admitted to selected causes [before (n = 3800): 11.3% after (n = 3958): 11.8% p = 0.123]. There was also no change in the rate of readmission than 7 days in our sample [before (n = 3369): 7.2% after (n = 3491): 6.7%, p = 0.407].
20
Bui, Huu Phuoc. "Approche multi-échelle de la rupture des structures en béton : Influence des agrégats sur la longueur interne du matériau". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI070/document.
Abstract (sommario):
Pour l'analyse de durabilité et la conception économique (moins de matériel) de structures en matériaux ressemblant à du béton, la modélisation de la rupture est essentielle. Dans le cadre de la mécanique des milieux continus, une longueur interne est introduite dans les modèles non locaux pour remédier au problème lié à la sensibilité du maillage qui est une pathologie des modèles d'endommagement classiques , lorsqu'il s'agit de matériaux adoucissantes. Toutefois, l'évaluation de la longueur interne de hétérogénéités du matériau est toujours une question difficile, ce qui rend un problème obscur en utilisant des modèles non locaux. Nos travaux portent sur le développement d'un outil numérique basée sur la méthode des éléments en treillis (LEM) qui est un modèle discret pour la simulation et la prévision de la rupture des structures en béton. En utilisant le modèle de réseau à l'échelle mésoscopique, il n'est pas nécessaire d'introduire une longueur interne dans la loi de comportement, comme cela se fait dans les modèles non locaux, et nous pouvons affranchir ce paramètre en introduisant explicitement la mesotructure matérielle via une description géométrique. Basé sur l'outil numérique développé, nous avons étudié, en effectuant des tests numériques de traction uniaxiale, l'influence géométrique de la mesotructure du matériau ainsi que l'influence des conditions aux limites et de tailles d'échantillons (qui se traduisent par le gradient de sollicitation et le champ de rotation de matériel différents) sur le taille de la FPZ (fracture process zone) et sur la longueur caractéristique du matériau quasi-fragile homogénéisé. Ces études fournissent des recommandations/avertissements lors de l'extraction d'une longueur interne nécessaire pour les modèles nonlocaux à partir de la microstructure du matériau. Par ailleurs, les études contribuent un aperçu direct de l'origine mésoscopic de la taille FPZ et la longueur de la caractéristique du matériau, et par conséquent sur l'origine et la nature du comportement non linéaire du matériau. Ensuite, nous avons implanté le modèle du treillis dans la bibliothèque de SOFA développé par l'INRIA pour réaliser le couplage avec la méthode des éléments finis (MEF) afin de faire face avec des structures à grande échelle. Nous avons proposé un algorithme de couplage entre une approche macroscopique représentée par MEF et une approche mésoscopique infligés par LEM au sein d'une manière adaptative. Le modèle de couplage est d'abord utilisée pour valider l'approche multi-échelle proposée sur des simulations heuristiques. Et à long terme, il fournit un outil prometteur pour des simulations de grandes structures en matériaux quasi-fragiles de la vie réelleFor durability analysis and economic design (less material) of structures made of concrete-like materials, modeling of cracking process and failure is essential. In the framework of continuum mechanics, an internal length is introduced in nonlocal models to remedy the problem related to mesh sensitivity which is a pathology of classical damage models, when dealing with softening materials. However, the assessment of the internal length from heterogeneities of the material is still a difficult question, which makes an obscure issue in using nonlocal models. Our work concerns developing of a numerical tool based on the Lattice Element Method (LEM) which is a discrete model for simulating and predicting fracture in concrete(-like) material. Using the lattice model at the mesoscopic scale, there is no need to introduce any internal length in the constitutive law, as done in nonlocal models, and we can enfranchise this parameter by explicitly introducing the material mesotructure via geometric description. Based on the developed numerical tool, we studied, by performing numerical uniaxial tensile tests, the geometric influence of the material mesotructure as well as the influence of the boundary conditions and specimen sizes (that result in different stress gradient and material rotation field) on the size of the FPZ (Fracture Process Zone) and on the characteristic length of the homogenized quasi-brittle material. These studies provide recommendations/warnings when extracting an internal length required for nonlocal damage models from the material microstructure. Moreover, the studies contribute a direct insight into the mesoscale origin of the FPZ size and the material characteristic length, and consequently into the origin and nature of the nonlinear behavior of the material. Then, we implemented the lattice model into SOFA library developed by INRIA for realizing the coupling with the Finite Element Method (FEM) in order to deal with large-scale structures. We proposed a strong coupling algorithm between a macroscopic approach represented by FEM and a mesoscopic approach dealt by LEM within an adaptive manner. The coupling model is first used to validate the multiscale approach proposed on heuristic simulations. And in the long term, it provides a promising tool for simulations of large-scale structures made of quasi-brittle materials of real life
21
Nordhage, Örjan. "On a Hydrogen Pellet Target for Antiproton Physics with PANDA". Doctoral thesis, Uppsala University, Department of Nuclear and Particle Physics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7137.
Abstract (sommario):
The PANDA experiment is a part of the future FAIR accelerator facility and will study the strong interaction by detecting the reaction products from antiproton-proton annihilations in a near full solid-angle configuration. One option for the internal proton target in PANDA is frozen micro-spheres of hydrogen, so-called pellets.
Such a pellet target is interesting because of the unique characteristics it offers; the high target thickness, the small interaction volume, the minimal gas load on the vacuum system, and the possibility of tracking individual pellets. Nevertheless, it is possible to allocate the bulky equipment needed to produce the pellets at a few meters away from the beam. This way particle detectors can be located close and almost fully around the interaction point.
This thesis is devoted to the optimization of a pellet target. To perform measurements, a Pellet-Test Station was built at The Svedberg Laboratory, Uppsala. For the first time, experimental results show the pellet distribution in space and time, and in addition, the vacuum along the pellet pipes. Furthermore, dedicated measurements carried out at CELSIUS/WASA demonstrate the existence of pellet heating as a result of beam-target interactions.
In performing calculations, the potential problems with pellet heating at PANDA are outlined. Moreover, to look at the consequences for the desired physics, a reaction involving short-lived D-mesons has been used to show the advantages of pellets compared to a more spacious target.
In conclusion, these studies lead to a deeper understanding of the pellet properties, which makes it possible to suggest future improvements, such as cooling with no vibrations.
22
Shavitranuruk, K. "Long Cavity Quantum Dot Laser Diode and Monolithic Passively Mode-Locked Operation". Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3392.
Abstract (sommario):
Advantage of the single QD active layer is its potential for very low threshold current density, which in turn can produce low internal optical loss. The low threshold current density and low internal loss thus enable a significant increase in laser diode cavity length. Because of the importance of the threshold current density in heatsinking, future technology of broad-area monolithic laser diodes can be implemented. The dissertation describes the development and the unique characteristics of single QD active layer laser with long cavity. The data are presented on single layer QD laser diodes that reach threshold current densities values of 11.7 A/cm2 in a p-up mounted 2 cm long cavity and as low as 10 A/cm2, with CW output power of 2 W in a p-down mounted 1.6 cm long cavity. The 8.8 A/cm2 in a p-down mounted 2 cm long cavity is reported. To our knowledge the value 8.8 A/cm2 is the lowest threshold current density ever reported for a room temperature laser diode. These single layer QD laser diodes reach an internal loss of ~0.25 cm-1, which is also the lowest ever reported for a room temperature laser diode. These unique characteristics of single layer QD and laser diode size are potentially promising for the monolithic mode-locked laser because of relatively high peak power with a low repetition rate that is on the order of a few GHz, which can be the novel device for external clocking in the optical interconnect applications. In this dissertation, the stable optical pulse train in a 40 µm wide stripe with a repetition rate of 3.75 GHz with 1.1 cm cavity length through the passive mode-locked onto the monolithic two-section device fabricated from this single layer QD laser is observed.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
23
Lu, Yinghua. "Empirical Likelihood Inference for the Accelerated Failure Time Model via Kendall Estimating Equation". Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/math_theses/76.
Abstract (sommario):
In this thesis, we study two methods for inference of parameters in the accelerated failure time model with right censoring data. One is the Wald-type method, which involves parameter estimation. The other one is empirical likelihood method, which is based on the asymptotic distribution of likelihood ratio. We employ a monotone censored data version of Kendall estimating equation, and construct confidence intervals from both methods. In the simulation studies, we compare the empirical likelihood (EL) and the Wald-type procedure in terms of coverage accuracy and average length of confidence intervals. It is concluded that the empirical likelihood method has a better performance. We also compare the EL for Kendall’s rank regression estimator with the EL for other well known estimators and find advantages of the EL for Kendall estimator for small size sample. Finally, a real clinical trial data is used for the purpose of illustration.
24
Razola, Mayor Barbara. "Las interacciones entre estudiantes en el aula de lenguas y en los entornos pedagogicos multimedia : convergencia, divergencia y potencialidad". Grenoble 3, 2009. http://www.theses.fr/2009GRE39023.
Abstract (sommario):
Cette thèse s'inscrit dans le champ de l'analyse des potentialités pédagogiques des interactions synchrones écrites pour l'apprentissage de la langue étrangère. L'objectif central est de découvrir dans quelle mesure le chat peut être considéré comme un moyen de communication valide pour la réalisation de tâches communicatives. De ce fait, ce dispositif de Communication Médiatisée par Ordinateur (CMO) peut être intégré de manière adéquate dans les environnements pédagogiques virtuels. Les ancrages théoriques reposent sur l'approche socio-interactionniste de l'acquisition et sur la linguistique interactionnelle, comprise comme l'ensemble des disciplines linguistiques dédiées à l'étude de la parole. Les analyses et leurs résultats s'appuient sur un corpus de données obtenues des réalisations de deux tâches communicatives en contexte institutionnel, un débat et un jeu de rôle, par un même groupe d'apprenants universitaires issus de deux classes d'espagnol langue étrangère. L'analyse de données s'articule en trois axes : la co-construction du discours interactionnel, les processus d'apprentissage provoqués par l'assistance entre apprenants dans l'interaction et la gestion collective de la tâche. Les résultats obtenus constituent un guide pour l'incorporation et l'usage du chat aux formations de langues étrangèresThis work is based on the framework of the analysis of the pedagogical potentialities of the synchronous written interaction for the learning of the foreign language. The central aim is to discover to what extend the chat can be considered as a valid communication way for the realisation of communicative tasks. In that way, this Computer Mediated Communication (CMC) device can be adequately integrated in the pedagogical virtual environments. The theoretical background lies on the socio-interactionnist approach of the acquisition and on the interactionist linguistics, known as every linguistic discipline dedicated to study the speech. The analyses and their results rely on data got from the realisation of two communicative tasks -one debate et one role play- in a institutional context by a group of university learners coming from two Spanish courses. The data analyse is based on three dimensions: the interactional discourse co-construction, the learning process caused by the learners' assistance in the interaction and the task collective management. The results constitute a guide for the incorporation and the utilisation of the chat in the foreign language education
25
Lin, Hui-Ling. "Jackknife Empirical Likelihood for the Variance in the Linear Regression Model". Digital Archive @ GSU, 2013. http://digitalarchive.gsu.edu/math_theses/129.
Abstract (sommario):
The variance is the measure of spread from the center. Therefore, how to accurately estimate variance has always been an important topic in recent years. In this paper, we consider a linear regression model which is the most popular model in practice. We use jackknife empirical likelihood method to obtain the interval estimate of variance in the regression model. The proposed jackknife empirical likelihood ratio converges to the standard chi-squared distribution. The simulation study is carried out to compare the jackknife empirical likelihood method and standard method in terms of coverage probability and interval length for the confidence interval of variance from linear regression models. The proposed jackknife empirical likelihood method has better performance. We also illustrate the proposed methods using two real data sets.
26
Mukka, Sebastian. "Aspects on treatment of femoral neck fractures : studies on treatment methods, surgical approach and external validity". Doctoral thesis, Umeå universitet, Ortopedi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-108269.
Abstract (sommario):
Femoral neck fracture (FNF) is a great challenge for today´s health care and is associated with high mortality and morbidity in the elderly. In the short term several studies in the literature have demonstrated improved hip function, quality of life and fewer re-operations in elderly patients treated with total hip arthroplasty (THA) instead of internal fixation (IF). There are few reports on the long-term outcome comparing IF and THA. The vast majority of orthopaedic departments in Sweden use the direct lateral (DL) or posteriolateral (PL) approaches for hip arthroplasty. The PL approach has been linked to an increased risk of dislocation of the prosthesis and a higher rate of revision surgery in comparison to the DL approach. There are few reports focusing on radiological risk factors for prosthetic dislocation and patient reported hip function comparing the two surgical approaches for hip arthroplasty in FNF. The randomized controlled trial (RCT) is the gold standard for evaluating medical or surgical interventions. An RCT of high quality has to be internally and externally valid. Internal validity refers to a correct study design to avoid bias skewing the results. External validity (EV) refers to whether the results will be clinically relevant to a definable group of patients and can be extrapolated to the general health care situation. There are only a few reports in the orthopaedic literature focusing on the EV of published studies and none in the field of hip fractures. Study I: This is a RCT of 100 patients with a displaced FNF comparing THA and IF. Follow-up evaluations were performed at three months and 1, 2, 4, 11 and 17 years. It was found that the Harris hip score (HHS) was higher and the rate of reoperations lower for patients treated with THA. Study II: This is a prospective cohort study of 185 hips, comparing the DL and the PL approaches in patients treated with a hemiarthroplasty (HA) for a displaced FNF. Follow-up was after 1 year. There was no difference in patient reported outcome between the groups measured with the HHS and WOMAC index. The PL approach resulted in a higher re-operation rate while the DL approach in a higher incidence of limping. Study III: This is a retrospective cohort study of 373 patients with a cemented bipolar HA using a PL approach for a FNF with a follow-up ranging from 6 months to 7 years. Radiographs and all surgical records were reviewed regarding femoral offset (FO), leg length discrepancy (LLD) and Wiberg angle. Patients with recurrent dislocations had a decreased postoperative FO, LLD and shallower acetabulum on the operated side compared with their controls. Study IV: This is a prospective cohort study of 840 hips comparing patients included in a RCT with those that did not give their informed consent (NC) or did not fulfill the criteria for participating in the trial (MS). Patients in the NC and MS groups had an increased mortality rate in comparison to those included in the study. We did not find any differences in hip function between these groups. The main conclusions of this thesis are: Healthy and lucid elderly patients with good hip function preoperatively, should be treated with THA for a displaced FNF. The DL approach is favourable in treating displaced FNF with HA due to its decreased risk of reoperation but with an identical hip function outcome as the PL approach. Care should be taken to restore the LLD and FO otherwise this may increase the risk of recurrent dislocation of a HA. Our findings suggest that trial participants had a lower mortality rate than non-participants but the functional outcome of non-participants appeared to be satisfactory. This is important to take into consideration when extrapolating study results to a health care system.Lårbenshalsfrakturer (FNF) är en utmaning för dagens sjukvård och förknippad med hög mortalitet i den äldre befolkningen. FNF orsakas främst av lågenergitrauma efter fall i samma plan hos patienter med benskörhet. Total höftledsprotes (THA) har visat sig ge en bättre höftfunktion, livskvalitet med färre omoperationer hos äldre patienter än sluten reposition samt fixering med skruvar (IF) under de första två-fyra åren efter operation. Få studier har publicerats med långtidsuppföljning av THA jämfört med IF. Vid behandling av felställd FNF med halv höftledsplastik (HA) eller THA finns olika kirurgiska metoder (snittföring) för implantation av protesen. Majoriteten av ortopedkliniker i Sverige använder direkt lateral (DL) eller posteriolateral (PL) snittföring. PL har kopplats till en ökad risk för luxation av protesen (urledsvridning), vilket i sin tur genererat en högre risk för omoperation jämfört med DL. Få studier har utvärderat höftfunktion med avseende på snittföring. Detsamma gäller vilka radiologiska faktorer som påverkar risken förprotesluxation. Det finns olika typer av studiedesigner för utvärdering av medicinska och kirurgiska behandlingsmetoder. Studiedesignen med högst bevisvärde anses vara den randomiserade kontrollerade studien (RCT). För att en RCT skall hålla hög kvalitet krävs intern och extern validitet. Intern validitet syftar på ett korrekt studieupplägg som mäter det som avses och undviker påverkan av icke önskvärda faktorer. Extern validitet (EV) innebär att erhållna resultat från studien är generaliserbara och kan extrapoleras till andra grupper än den studerade. Det inga rapporter i ortopediska litteraturen med fokus på EV med patienter som drabbats av FNF. Studie I: Prospektiv randomiserad studie av 100 patienter med en felställd FNF jämförs THA med IF med avseende på höftfunktion och reoperationer. Uppföljning gjordes efter tre månader samt 1, 2, 4, 11 och 17 år. HHS som mått på höftfunktion var högre och andelen reoperationer lägre för patienter som behandlades med THA. Studie II: Prospektiv kohortstudie med 183 patienter med felställd FNF behandlade med HA och antingen DL eller PL. Vi fann ingen skillnad i patientrapporterad höftfunktion utvärderat med HHS och WOMAC efter 1 år men en ökad förekomst av hälta vid DL. Studie III: Retrospektiv kohortstudie av 373 patienter opererade med en cementerad bipolär HA och PL. Postoperativa röntgenbilder granskades avseende femoral offset (FO), postoperativ benlägdsskillnad (LLD) samt acetabulär Wibergvinkel och relaterades till återkommande protesluxationer. Detta relaterades till återkommande luxationer. Uppföljningstiden varierade mellan 6 månader och 7 år. Patienter med återkommande luxationer hade en minskad postoperativ global FO, förkortad LLD och grundare acetabulum på den opererade sidan jämfört med kontroller. Studie IV: Prospektiv kohortstudie av 840 patienter med felställd FNF där patienter som ingick i en RCT jämförs med de som inte gav sitt samtycke för deltagande eller ej inkluderats i screeningprocessen. De patienterna som inte gav sitt samtycke hade ökad dödlighet, men ingen skillnad i höftfunktion jämfört med deltagare. Slutsatser • Friska och kognitivt vitala äldre patienter med god höftfunktion innan en felställd lårbenshalsfraktur bör behandlas med total höftledsprotes. • DLsnittföring ger ett lika bra patientrapporterad höftfunktion men en ökad förekomst av hälta jämfört med PL snitt vid behandling med halvprotes på grund av en felställd lårbenshalsfraktur. • Ansträngning bör göras för att återställa benlängdsskillnad samtfemoral offset och därigenom minska risken för återkommande luxation. • Våra resultat tyder på att patienter som deltar i en randomiserad studie har lägre dödlighet än patienter som avböjt att delta samt de som missats i screeningprocessen. Det är viktigt att ta hänsyn till när extrapolerar studieresultat till ett hälso-och sjukvårdssystem. Detta bör vägas in i värderingen av studieresultatens externa validitet.
27
Médeau, Victor. "Rupture des composites tissés 3D : de la caractérisation expérimentale à la simulation robuste des effets d’échelle". Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0025/document.
Abstract (sommario):
Ces travaux s’attachent à décrire et quantifier les mécanismes de ruptures des compositestissés 3D sous chargement de traction quasi-statique et à mettre en place une méthode de simulationnumérique adaptée et robuste, pouvant à terme être appliquée en bureau d’études.Dans cette optique, une étude expérimentale a été menée afin de quantifier la propagation defissures dans ces matériaux. Celle-ci a permis de mettre en place un scenario de rupture, entirant parti de la multi-instrumentation des essais. L’étude a également été effectuée sur deséprouvettes de géométries et de tailles variées et a mis en évidence d’importantes variations dutaux de restitution d’énergie avec les conditions d’essai. Un formalisme d’analyse et de modélisationintroduisant des longueurs internes a ensuite été présenté et adapté aux mécanismes derupture des composites tissés 3D. Ce formalisme est étayé par la recherche des mécanismes àl’aide de l’analyse des faciès de rupture. Les longueurs introduites ont ainsi été mises en relationavec les paramètres du tissage. Une méthode d’identification des paramètres a été proposée etles conséquences de ce comportement sur le dimensionnement de pièces composites discutées.Enfin, le transfert de ces résultats a été effectué vers des simulations numériques robustes. Desméthodes de régularisation des modèles d’endommagement continu ont été présentées et évaluéesà l’aune de leur capacité à assurer, d’une part, la robustesse des résultats et, d’autre part,la bonne retranscription des effets d’échelle expérimentaux. La prise en compte de ces considérationsnumériques et physiques nous a amené à proposé un modèle d’endommagement Non-Local.Une méthode d’identification des paramètres et de la longueur interne à partir des données expérimentalesa été proposéeThis work aims to describe and quantify the failure mechanisms of 3D woven composites underquasi-static tensile loading and to implement an adapted and robust numerical simulationmethod, that can be applied in industry. To this end, an experimental study was carried out toquantify the propagation of cracks in these materials. Thus, a crack propagation scenario wasestablished, thanks to the multi-instrumentation used during the tests. The experimental campaignwas carried out on specimens of various geometries and sizes and highlighted significantvariations in the fracture toughness with the test conditions. A modelisation framework introducinginternal lengths was then presented and adapted to 3D woven composites. This frameworkis supported by the identification of the failure mechanisms subsequent to the analysis of thecrack profile. The introduced lengths were thus related to the weaving parameters. A method foridentifying the parameters was proposed and the consequences of this behaviour on the designof the composite parts discussed. Finally, these results were transferred to robust numerical simulations.Regularisation methods of continuous damage models were presented and evaluatedin terms of their ability to ensure, on the one hand, the robustness of the results and, on theother hand, the correct transcription of experimental size effects. Taking into account these numericaland physical considerations led us to propose a Non-Local damage model. A method foridentifying the parameters and the internal length on experimental data was proposed
28
Peraza, Ávila Jesús Enrique. "Experimental study of the diesel spray behavior during the jet-wall interaction at high pressure and high temperature conditions". Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/149389.
Abstract (sommario):
[EN] The potential of diesel engines in terms of robustness, efficiency and energy density has made them widely used as power generators and propulsion systems. Specifically, fuel atomization, vaporization and air-fuel mixing, have a fundamental effect on the combustion process, and consequently, a direct impact on pollutant formation, fuel consumption and noise emission. Since the combustion chamber has a limited space respect to the spray penetration, wall impingement is considered to be a common event in direct injection diesel engines, having a relevant influence in the spray evolution and its interaction with both surrounding air and solid walls. This makes of spray-wall interaction an important factor for the combustion process that is still hardly understood.
At cold-start conditions, the low in-chamber pressures and temperatures promote the deposition of fuel in the piston wall, which leads to a boost in the formation of unburned hydrocarbons. Additionally, modern design trends such as the increment of rail pressures in injection systems and the progressive reduction of the engine displacement, favor the emergence of spray collision onto the walls. In spite of the evident relevance of the comprehension of this phenomenon and the efforts of engine researchers to reach it, the transient nature of injection process, its small time scales and the complexity of the physical phenomena that take place in the vicinity of the wall, make challenging the direct observation of this spray-wall interaction. Even though computational tools have proven to be priceless in this field of study, the need for reliable experimental data for the development of those predictive models is present.
This thesis is aimed to shed light on the fundamental characteristics of spray-wall interaction (SWI) at diesel-like chamber conditions. A flat wall was set at different impingement distances and angles respect to the spray. In this way, two different kinds of experimental investigations on colliding sprays were carried out: A transparent quartz wall was employed into the chamber to, in isolation, analyze the macroscopic characteristics of the spray at both evaporative inert and reactive conditions, which have been observed laterally and through the wall, thanks to the use of a high-pressure and high-temperature vessel with optical accesses. This same test rig was used in the second kind of experiments, where instead of the quartz plate, a stainless steel wall was used to capture the effect of the operating conditions on the heat flux between the wall and the spray during the injection-combustion events and to determine how spray and flame evolution are affected by realistic heat transfer situations. This wall was instrumented to control its initial in-chamber surface temperature and to measure its variation with time by using high-speed thermocouples. Tests at free-jet conditions were also performed in order to provide a solid comparative base for those experiments.[ES] El potencial de los motores diesel en términos de robustez, eficiencia y la densidad de energía los ha hecho ser ampliamente usados como generadores de energía y sistemas propulsivos. Específicamente, la atomización de combustible, vaporización y mezcla de aire y combustible tienen un efecto fundamental en el proceso de combustión y, en consecuencia, un impacto directo en la formación de emisiones contaminantes, consumo de combustible y generación de ruido. Dado que la cámara de combustión tiene un espacio limitado con respecto la capacidad de penetración del chorro, el impacto de la pared se considera bastante común en motores de inyección directa diésel, que tienen una influencia relevante en la evolución del chorro y su interacción con el aire circundante y las paredes sólidas. Esto hace de interacción chorro-pared, un factor importante para el proceso de combustión que aún es dificilmente comprendido. En condiciones de arranque en frío, las bajas presiones y temperaturas en la cámara promueven la deposición de combustible en la pared del pistón, lo que conduce a un aumento en los niveles de formación de hidrocarburos no quemados. Además, las tendencias modernas de diseño como el incremento de las presiones de rail en los sistemas de inyección y la progresiva reducción en la cilindrada de los motores, favorecen la aparición de colisiones entre chorro y pared. A pesar de la evidente importancia en la comprensión de este fenómeno y los esfuerzos de los investigadores para alcanzarla, la transitoria naturaleza del proceso de inyección, sus pequeñas escalas de temporales y la complejidad de los fenómenos físicos que tienen lugar en las proximidades de la pared, hacen que la observación directa de esta interacción chorro-pared sea un desafío. Aunque las herramientas computacionales han demostrado ser invaluables en este campo de estudio, la necesidad de datos experimentales confiables para el desarrollo de esos modelos predictivos está muy presente. Esta tesis tiene como objetivo arrojar luz sobre las características fundamentales de la interacción chorro-pared (SWI por sus siglas en inglés) en condiciones de cámara similares a las de un motor diesel. Se colocó una pared plana a diferentes distancias de impacto y ángulos con respecto al jet. De esta manera, dos tipos diferentes de investigaciones experimentales sobre chorros en colisión se llevaron a cabo: se empleó una pared de cuarzo transparente en la cámara para, de forma aislada, analizar las características macroscópicas del chorro en condiciones evaporativas inertes y reactivas, que pueden observarse lateralmente y a través de la pared, gracias al uso de una instalación de alta presión y alta temperatura ópticamente accesible. Esta misma instalación se utilizó en el segundo tipo de experimentos en los que se introdujo una pared de acero inoxidable para capturar adicionalmente el efecto de las condiciones de operación en el flujo de calor entre ésta y el chorro durante los eventos de inyección y combustión y para determinar cómo la evolución del chorro y la llama son afectadas por una situación realista de transferencia de calor. Esta pared fue instrumentada para controlar la temperatura inicial de su superficie expuesta a la cámara y medir su variación con el tiempo, utilizando termopares de alta velocidad. Ensayos en condiciones de chorro libre también se realizaron para proporcionar una base comparativa sólida para esos experimentos.
[CA] El potencial dels motors dièsel en termes de robustesa, eficiència i la densitat d'energia els ha fet ser àmpliament usats com a generadors d'energia i sistemes propulsius. Específicament, l'atomització de combustible, vaporització i barreja d'aire i combustible tenen un efecte fonamental en el procés de combustió i, en conseqüència, un impacte directe en la formació d'emissions contaminants, consum de combustible i generació de soroll. Atès que la cambra de combustió té un espai limitat pel que fa la capacitat de penetració de l'raig, l'impacte de la paret es considera bastant comú en motors d'injecció directa dièsel, que tenen una influència rellevant en l'evolució del doll i la seva interacció amb el aire circumdant i les parets sòlides. Això fa d'interacció doll-paret, un factor important per al procés de combustió que encara és difícilment comprès. En condicions d'arrencada en fred, les baixes pressions i temperatures a la cambra promouen la deposició de combustible a la paret del pistó, el que condueix a un augment en els nivells de formació d'hidrocarburs no cremats. A més, les tendències modernes de disseny com l'increment de les pressions de rail en els sistemes d'injecció i la progressiva reducció en la cilindrada dels motors, afavoreixen l'aparició de col·lisions entre el doll i la paret. Tot i l'evident importància en la comprensió d'aquest fenomen i els esforços dels investigadors per aconseguir-la, la transitòria naturalesa de l'procés d'injecció, les seves petites escales de temporals i la complexitat dels fenòmens físics que tenen lloc en les proximitats de la paret , fan que l'observació directa d'aquesta interacció doll-paret siga un desafiament. Tot i que les eines computacionals han demostrat ser invaluables en aquest camp d'estudi, la necessitat de dades experimentals fiables per al desenvolupament d'aquests models predictius està molt present. Aquesta tesi té com a objectiu donar llum sobre les característiques fonamentals de la interacció doll-paret (SWI per les seues sigles en anglès) en condicions de cambra similars a les d'un motor dièsel. Es va col·locar una paret plana a diferents distàncies d'impacte i angles pel que fa al jet. D'aquesta manera, dos tipus diferents d'investigacions experimentals sobre dolls en col·lisió es van dur a terme: es va emprar una paret de quars transparent a la cambra per, de forma aïllada, analitzar les característiques macroscòpiques del doll en condicions evaporació inerts i reactives, que poden observar lateralment i a través de la paret, gràcies a l'ús d'una instal·lació d'alta pressió i alta temperatura òpticament accessible. Aquesta mateixa instal·lació es va utilitzar en el segon tipus d'experiments en els quals es va introduir una paret d'acer inoxidable per capturar addicionalment l'efecte de les condicions d'operació en el flux de calor entre aquesta i el dull durant els esdeveniments d'injecció i combustió i per determinar com l'evolució del doll i la flama són afectades per una situació realista de transferència de calor. Aquesta paret va ser instrumentada per controlar la temperatura inicial de la seua superfície exposada a la càmera i mesurar la seua variació amb el temps, utilitzant termoparells d'alta velocitat. Assajos en condicions de doll lliure també es van realitzar per proporcionar una base comparativa sòlida per a aquests experiments.
Peraza Ávila, JE. (2020). Experimental study of the diesel spray behavior during the jet-wall interaction at high pressure and high temperature conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149389
TESIS
29
Manrrique, Ostos Nely Beatrís. "Evaluación del uso de internet como recurso educativo en el rendimiento académico del Área de Comunicación en los estudiantes del sexto grado de primaria de la institución educativa Nº 3071-Manuel García Cerrón, Puente Piedra, Lima 2011". Master's thesis, Universidad Nacional Mayor de San Marcos, 2013. https://hdl.handle.net/20.500.12672/3758.
Abstract (sommario):
La investigación científica que se ha realizado es básica, correlacional causal no experimental, los factores de estudio son dos: el uso del internet como recurso educativo en el rendimiento académico en la Institución Educativa N° 3071 Manuel García Cerrón, Puente Piedra. La población y muestra estuvo conformada por 135 alumnos de la I.E. Manuel García Cerrón distribuidos de la siguiente manera: los alumnos seleccionados son del 6° grado de primaria del área de comunicación.
El diseño de la investigación es transaccional, correlacional, causal, bivariada, transversal. Para la recolección de datos se confeccionaron dos cuestionarios estructurados como medición y consta de dos aspectos: El uso del internet con sus dimensiones: frecuencia del uso del internet, tiempo del uso del internet y el control del uso del internet. En cuanto al rendimiento académico se empleo las siguientes dimensiones: Comprensión de textos, expresión y comprensión oral y producción de textos que se aplico a los 135 alumnos de la muestra.
Los instrumentos cumplen con las cualidades de validez y confiabilidad. El estudio plantea la siguiente hipótesis de investigación existe relación significativa entre Evaluación del uso del internet como recurso educativo en el rendimiento académico de los estudiantes del sexto grado en el área de Comunicación en la Institución Educativa N° 3071 Manuel García Cerrón, Puente Piedra, Lima-Perú 2011.
Los resultados obtenidos permiten rechazar la hipótesis nula y aceptar la hipótesis investigadas pues se ha encontrado al aplicar la fórmula Rho de Spearman con un nivel de significancia del 95% se encontró que el coeficiente de correlación Rho de Spearman es de 0,828 y el p_ valor es de 0,000 por lo tanto establecemos que tiene un nivel correlación muy bueno, vemos que existe una relación directa y un nivel de significancia menor que 0,05 por tal motivo se rechaza la hipótesis Nula y se acepta la alternaTesis
30
Iturriaga, Gamboa Cristina. "La expresión de significados evaluativos en foros de opinión en inglés en Internet". Tesis, Universidad de Chile, 2010. http://repositorio.uchile.cl/handle/2250/108626.
Abstract (sommario):
Durante las últimas décadas, los avances tecnológicos en el campo de las comunicaciones han generado grandes cambios en la forma de intercambio de información entre los seres humanos. Estos cambios se ven reflejados en el creciente número de personas que cada día pasan a formar parte de una comunidad global interconectada cuya expansión y consolidación parece no detenerse. Al respecto, Internet representa una de las herramientas de información y comunicación masiva más utilizada en variados ámbitos del quehacer humano y social. Esta herramienta posee importantes características tales como la libertad de expresión y flexibilidad de acceso a la información. Estas características han abierto un valioso espacio para quienes, por ejemplo, sin ser científicos, críticos especializados o periodistas profesionales, desean expresar sus opiniones respecto de una gran cantidad de temas planteados diariamente en variados foros interactivos en Internet. En la presente investigación, se ha emprendido un estudio de carácter empírico y cuantitativo de las expresiones evaluativas empleadas en foros interactivos generados en sitios web, en los cuales se vierten e intercambian juicios y opiniones de carácter técnico y no técnico acerca de temas presentados por una persona iniciadora de discusión. El propósito principal ha sido dar cuenta de la frecuencia de ocurrencia de las distintas categorías de significados evaluativos expresados en los textos interactivos escritos como ‗respuestas‘ a los temas planteados en los foros de opinión referidos. Para este efecto, se ha empleado, y modificado parcialmente, el modelo descriptivo de las categorías evaluativas propuesto por Martin y White (2005), aplicable tanto en el nivel oracional como en el nivel textual –especialmente- y discursivo.
31
Parmeggiani, Rafaela Prosdocini [UNESP]. "Atividade cambial em ramos de Kielmeyera grandiflora (WAWRA) saddi (Callophylaceae) ocorrentes no cerrado paulista". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/134277.
Abstract (sommario):
Submitted by Rafaela Prosdocini Parmeggiani (rafaela.prosdocini@gmail.com) on 2016-02-16T16:01:51Z
No. of bitstreams: 1
Atividade cambial em ramos de Kielmeyera grandiflora (Wawra) Saddi (Calophyllaceae) ocorrentes no cerrado paulista.pdf: 2086514 bytes, checksum: d4efa2e5aa9b442218c364e59bc53a9a (MD5)Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-02-17T15:53:14Z (GMT) No. of bitstreams: 1 parmeggiani_rp_me_bot.pdf: 2086514 bytes, checksum: d4efa2e5aa9b442218c364e59bc53a9a (MD5)
Made available in DSpace on 2016-02-17T15:53:14Z (GMT). No. of bitstreams: 1 parmeggiani_rp_me_bot.pdf: 2086514 bytes, checksum: d4efa2e5aa9b442218c364e59bc53a9a (MD5) Previous issue date: 2015-12-16
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
No cerrado, as estações são bem demarcadas pela sazonalidade pluvial, portanto, espera-se que haja uma sazonalidade na atividade do câmbio vascular. Kielmeyera grandiflora é considerada uma espécie modelo para estudos de atividade cambial em ramos, pois possui módulos de crescimento bem demarcados, formados por cicatrizes da gema terminal. Nosso objetivo foi de entender qual a relação entre a atividade cambial de Kielmeyera grandiflora (Wawra) Saddi (Calophyllaceae), os fatores ambientais e a fenologia e responder se a atividade cambial varia entre três módulos de crescimentos consecutivos. A área de estudo é um fragmento de cerrado em regeneração no município de Botucatu, estado de São Paulo, Brasil (S 22º53’11.0’’, W 48º29’17.3’’). Foram amostrados mensalmente os três últimos módulos de crescimento dos ramos de três indivíduos durante o período de fevereiro de 2012 a fevereiro de 2013. No mesmo período, a fenologia (brotação, folhas novas, folhas adultas, folhas senescentes e queda foliar) foram avaliadas. O material foi fixado em CRAF III para conservação do conteúdo celular. As amostras foram desidratadas em série alcoólica e incluídas em resina metacrilato para posterior corte em micrótomo rotativo. As análises foram feitas em fotomicroscópio de luz. Utilizamos Modelo Generalizado Linear Misto (GLMM) com erro Binomial para a variável resposta presença/ausência da atividade cambial e erro de Poisson para a variável resposta de contagem de paredes recém formadas. O início da atividade cambial, a brotação e o desenvolvimento de folhas novas ocorreram durante o mês de agosto no período seco. O período de atividade cambial sobrepôs-se à estação chuvosa, temperaturas elevadas e comprimento do dia entre 12 e 13,6 h. O câmbio vascular entrou em dormência em maio, mês que ainda chovia, contudo a temperatura e o comprimento do dia passavam por quedas acentuadas. A variação da atividade cambial entre os módulos de crescimento foi representativa somente no período de reativação cambial, mostrando que o módulo 1, mais próximo às fontes de auxina, apesar de ter iniciado atividade junto ao módulo 3, produziu em todo o período analisado, maior quantidade de células novas, possivelmente devido à ação de hormônios produzidos nos tecidos jovens e em desenvolvimento.
In the cerrado, the seasons are well marked by rain seasonality; therefore, there is a seasonality in the vascular cambium activity. Kielmeyera grandiflora is considered a model for branch cambial activity studies because it has well marked growth modules formed by terminal bud scars. Our goal was to understand what the relationship between cambial activity of Kielmeyera grandiflora (Wawra) Saddi (Calophyllaceae), environmental factors and the phenology and answear wheter cambial activity varies between three consecutive sections of internodal growth. The study area is a cerrado fragment in regeneration in the city of Botucatu, São Paulo State, Brazil (22° 53 ' S 11.0 '', W 48° 29 ' 17.3 ''). Were sampled on a monthly basis the last three modules of growth of branches of three individuals during the period between February 2012 to February 2013. The material was fixed in CRAF III for preservation of cell content. The samples were dehydrated in alcohol series and included in historesin for further cut in rotary microtome. Analyses were made on light microscope. We used Generalized Linear Mixed Model (GLMM) with Binomial error for the variable reply presence/absence of cambial activity and Poisson error for the variable count response of newly formed walls. The beginning of cambial activity, the sprouting and the development of new leaves occurred during the month of August in the dry period. The period of cambial activity overlapped the rainy season, high temperatures and day length between 12 and 13, 6 h. The vascular cambium dormancy was observed in May, a raining month; however, temperature and day length was decreasing. The variation of cambial activity between the internodal growth sections was representative just in reactivation period, showing that the younger internodal section, closest to the sources of auxin, has produced in the whole study period a larger number of new cells that the older, possibly due to the action of hormones produced in young and development tissues.
32
Zanatta, Anne Marie. "Using wikis for collaborative writing in the english for tourism classroom". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/482229.
Abstract (sommario):
The recent surge in studies and literature on the use of wikis and other Web 2.0 tools in language learning emphasizes the pedagogical benefits of using these tools for collaborative writing tasks in the Foreign Language classroom. Nonetheless, existing research regarding collaborative writing projects involving more than two writers is limited. This may, in part, be due to the fact that writing is a complex and challenging act which becomes even more so when it is collaborative and involves more than two people. Furthermore, the implementation of a wiki or any other digital collaborative writing tool may serve to complicate rather than facilitate it even more. This dissertation presents a mixed methods case study of the use of a wiki for a collaborative writing project carried out in the English for Tourism classroom at the higher education level. The subjects of the study, 63 first-year students enrolled in a 4-year degree program in Tourism Studies at a private institution in Barcelona, were participants of an English for Tourism language course divided into 3 different class groups based on language proficiency and led by 3 different teachers. A total of 18 small working groups of 3 or 4 students participated in the project known as Touripedia which took place over a 6 month period divided into 3 project phases. Findings from this study reveal how student use and perceptions of the wiki tool differ according to the three phases of the collaborative writing project. The overriding goal of this research is to provide understanding of how the wiki influences learner processes and perceptions when involved in a collaborative writing task. By offering insight and guidelines which increase learning opportunities and minimize the challenges of effective use of the wiki tool, this study also aims to assist language teachers considering the implementation of such activities into their own classrooms and may also help software designers to better understand the needs of both learners and teachers for the continued development of collaborative tools which specifically facilitate language learning processes.El recent augment en els estudis i la literatura sobre l’ús de wikis i altres eines de la Web 2.0 en l’aprenentatge d’idiomes emfatitza els beneficis pedagògics de la utilització d’aquestes eines per a les tasques d’escriptura de col·laboració a l’aula de llengua estrangera. No obstant això, l’existent recerca és encara escassa, doncs són pocs els projectes d’escriptura col·laborativa amb més de dos escriptors que s’han desenvolupat fins ara. Això pot ser degut al fet que l’escriptura és un acte complex i desafiant, el qual es torna encara més difícil quan es tracta d’un treball col·laboratiu i involucra a més de dues persones. A més d’això, la implementació d’un wiki o d’una altra eina de col·laboració digital pot servir per complicar en lloc de facilitar encara més. Aquesta tesi presenta un estudi de cas de mètodes mixtos sobre l'ús d'un wiki per a un projecte d'escriptura col·laborativa dut a terme a l'aula d'Anglès per al Turisme a nivell d'educació superior. Els subjectes d'estudi, 63 estudiants de primer any matriculats en un programa de grau de 4 anys d'Estudis Turístics en una institució privada a Barcelona, van ser els participants d'un curs de llengua anglesa per al Turisme dividits en 3 grups diferents basats en el domini de l'idioma i ensenyats per 3 professors diferents. Un total de 18 petits grups de treball d'entre 3 o 4 alumnes van participar en el projecte conegut com Touripedia, el qual va ser dut a terme durant un període de 6 mesos dividit en 3 fases del projecte. Els resultats d'aquest estudi posen de manifest com les reaccions dels alumnes sobre l'ús de l'eina difereixen d'acord a les fases i les etapes del projecte d'escriptura col·laborativa. L'objectiu primordial d'aquesta investigació és proporcionar comprensió sobre com l'ús d'un wiki influeix en els processos i en les percepcions de l'aprenent quan participa en una tasca d'escriptura col·laborativa. En oferir una visió i unes directrius que augmenten les oportunitats d'aprenentatge i minimitzen els desafiaments de l'ús efectiu de l'eina wiki, aquest estudi també té com a objectiu ajudar els professors d'idiomes tenint en compte l'aplicació de tals activitats en les seves pròpies aules, així com també pot ajudar els dissenyadors de software per a comprendre millor les necessitats dels alumnes i dels professors per al desenvolupament continu d'eines de col·laboració que facilitin específicament els processos d'aprenentatge d'idiomes.
El reciente aumento en los estudios y la literatura sobre el uso de wikis y otras herramientas de la Web 2.0 en el aprendizaje de idiomas enfatiza los beneficios pedagógicos de la utilización de estas herramientas para las tareas de escritura de colaboración en el aula de lengua extranjera. Sin embargo, la existente investigación es todavía escasa, pues son pocos los proyectos de escritura colaborativa con más de dos escritores que se han desarrollado hasta ahora. Esto puede ser debido, en parte, a que la escritura es un acto complejo y desafiante, el cual se vuelve aún más difícil cuando se trata de un trabajo colaborativo e involucra a más de dos personas. Además de esto, la implementación de un wiki o de otra herramienta de colaboración digital puede servir para complicar en lugar de facilitar aún más. Esta tesis presenta un estudio de caso de métodos mixtos sobre el uso de un wiki para un proyecto de escritura colaborativa llevado a cabo en el aula de Inglés para el Turismo a nivel de educación superior. Los sujetos de estudio, 63 estudiantes de primer año matriculados en un programa de grado de 4 años de Estudios Turísticos en una institución privada en Barcelona, fueron los participantes de un curso de lengua Inglesa para el Turismo divididos en 3 grupos distintos basados en el dominio del idioma y enseñados por 3 profesores diferentes. Un total de 18 pequeños grupos de trabajo de entre 3 o 4 alumnos participaron en el proyecto conocido como Touripedia, el cual fue llevado a cabo durante un período de 6 meses dividido en 3 fases del proyecto. Los hallazgos de este estudio ponen de manifiesto cómo las reacciones de los alumnos sobre el uso de la herramienta difieren de acuerdo a las fases y las etapas del proyecto de escritura colaborativa. El objetivo primordial de esta investigación es proporcionar comprensión sobre cómo el uso de un wiki influye en los procesos y en las percepciones del aprendiz cuando participa en una tarea de escritura colaborativa. Al ofrecer una visión y unas directrices que aumentan las oportunidades de aprendizaje y minimizan los desafíos del uso efectivo de la herramienta wiki, este estudio también tiene como objetivo ayudar a los profesores de idiomas teniendo en cuenta la aplicación de tales actividades en sus propias aulas, así como también puede ayudar a los diseñadores de software para comprender mejor las necesidades de los alumnos y de los profesores para el desarrollo continuo de herramientas de colaboración que faciliten específicamente los procesos de aprendizaje de idiomas.
33
Le, Cunuder Anne. "Étude expérimentale des forces de Casimir". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN007/document.
Abstract (sommario):
L'étude des fluctuations dans les milieux confinés constitue un domaine de recherche très récent, que ce soit du point de vue théorique ou expérimental. Afin d'analyser le rôle du confinement sur les propriétés des fluctuations de densité dans un mélange binaire, nous avons développé un système de mesure d'une grande sensibilité, où l'intensité des fluctuations et leur longueur de corrélation peuvent être amplifiées. L'idée consiste à travailler proche du point critique d'une transition de phase de démixion d'un mélange binaire. En effet, la longueur de corrélation augmente exponentiellement lorsqu'on s'approche de la température Tc du point critique de démixion.Nous avons développé un montage permettant de confiner le mélange entre un échantillon plan et une sphère colloïdale attachée à l'extrémité d'un levier de Microscope à Force Atomique (AFM). D'après les prédictions de Fisher et De Gennes, un effet intéressant émerge lorsque la longueur de corrélation est comparable avec la taille du confinement: les deux surfaces vont soit s'attirer, soit se repousser suivant les préférences d'adsorption des composants du mélange pour chacune des surfaces. On nomme cet effet l'effet Casimir critique, en référence à la force de Casimir électrodynamique qui résulte du confinement des fluctuations quantiques du champ électromagnétique.Durant cette thèse, nous avons mesuré la force de Casimir électrodynamique avec le système de mesure que nous avons développé, d'abord dans une atmosphère d'azote puis dans l'éthanol. Ces mesures prouvent que notre appareil de mesure est assez sensible pour mesurer des forces très faibles de l'ordre de la dizaine de pN. Les forces mesurées sont comparées à la théorie de Lifshitz, où les effets de conductivité finie des surfaces sont considéréesThe study of density fluctuations inside confined liquid systems has received the attention of recent theoretical and experimental papers. In order to analyze the role of confinement on the statistical properties of fluctuations, we developed a highly sensitive system where the intensity of fluctuations, as well as their spatial correlation length can be simply tuned. The idea will be to enhance the role of fluctuations working close to the critical temperature Tc of a second order phase transition in a binary mixture. Indeed, the correlation length dramatically increases when one approaches the critical demixion point.The confinement is obtained by using a sphere-plane geometry with a colloidal particle attached to the cantilever of an Atomic Force Microscope (AFM). When the correlation length is comparable with the distance of confinement, Fisher and De Gennes predicted the existence of an interesting effect: the two surfaces will be submitted to either an attracting or a repelling force, depending on boundary conditions. This effect is called the critical Casimir force in reference to the quantum Casimir force resulting from the confinement of quantum fluctuations of the electromagnetic field.During this thesis, we measured the quantum Casimir force between the sphere and the plate, first in a nitrogen atmosphere and then in ethanol, showing that the developed instrument is sufficiently sensible to measure very weak force, of the same order of magnitude or even weaker than the critical Casimir force. Measurements are compared to Lifshitz theory, taking into account the finite conductivity of surfaces
34
Sanz, Gil Mercedes. "Las Tecnologías de la Información y de la Comunicación y la autonomía de aprendizaje de lenguas. Análisis crítico y estudio de casos en el aprendizaje del FLE". Doctoral thesis, Universitat Jaume I, 2003. http://hdl.handle.net/10803/10437.
Abstract (sommario):
Las TIC representan en sí mismas un campo de conocimiento en expansión, tanto en el ámbito de la investigación como en el de la enseñanza.Esta tesis se encuadra en el ámbito del aprendizaje en autonomía, y en concreto, en la formación a la autonomía a través de las potencialidades de las TIC, campos de investigación, autonomía y TIC, de corte muy actual, pero que, tal y como se expone en los diferentes capítulos, no se trata de conceptos nuevos, sino que sus principios estructuradores suponen una evolución en el tiempo y un proceso de maduración.
En este sentido, en la primera parte se hace un recorrido por las diferentes corrientes psicopedagógicas y metodologías de aprendizaje de lenguas, señalando cómo aparecen los diferentes aspectos relacionados con el aprendizaje en autonomía. Se presenta también, la evolución producida en el campo de las tecnologías aplicadas a la educación, en cuanto a las posibilidades técnicas que ofrecen, y en cuanto a la interacción con el usuario.
Finalmente, un estudio de casos muestra cómo las propuestas tecnológicas de aprendizaje más recientes pueden ser integradas en diferentes proyectos de aprendizaje, según los aprendices y según su estilo cognitivo y de aprendizaje.
35
ElNady, Khaled. "Modèles de comportement non linéaire des matériaux architecturés par des méthodes d'homogénéisation discrètes en grandes déformations. Application à des biomembranes et des textiles". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0032/document.
Abstract (sommario):
Ce travail porte sur le développement de modèles micromécaniques pour le calcul de la réponse homogénéisée de matériaux architecturés, en particulier des matériaux se présentant sous forme de treillis répétitifs. Les matériaux architecturés et micro-architecturés couvrent un domaine très large de de propriétés mécaniques, selon la connectivité nodale, la disposition géométrique des éléments structuraux, leurs propriétés mécaniques, et l'existence d'une possible hiérarchie structurale. L'objectif principal de la thèse est la prise en compte des nonlinéarités géométriques résultant des évolutions importantes de la géométrie initiale du treillis, causée par une rigidité de flexion des éléments structuraux faible en regard de leur rigidité en extension. La méthode dite d'homogénéisation discrète est développée pour prendre en compte les non linéarités géométriques pour des treillis quais périodiques; des schémas incrémentaux sont construits qui reposent sur la résolution incrémentale et séquentielle des problèmes de localisation - homogénéisation posés sur une cellule de base identifiée, soumise à un chargement contrôlé en déformation. Le milieu continu effectif obtenu est en général un milieu micropolaire anisotrope, dont les propriétés effectives reflètent la disposition des éléments structuraux et leurs propriétés mécaniques. La réponse non affine des treillis conduit à des effets de taille qui sont pris en compte soit par un enrichissement de la cinématique par des variables de microrotation ou par la prise en compte des seconds gradients du déplacement. La construction de milieux effectifs du second gradient est faite dans un formalisme de petites perturbations. Il est montré que ces deux types de milieu effectif sont complémentaires en raison de l'analogie existant lors de la construction théorique des réponses homogénéisées, et par le fait qu'ils fournissent des longueurs internes en extension, flexion et torsion. Des applications à des structures tissées et des membranes biologiques décrites comme des réseaux de filaments quais-périodiques ont été faites. Les réponses homogénéisées obtenues sont validées par des comparaisons avec des simulations par éléments finis réalisées sur un volume élémentaire représentatif de la structure. Les schémas d'homogénéisation ont été implémentés dans un code de calcul dédié, alimenté par un fichier de données d'entrée de la géométrie du treillis et de ses propriétés mécaniques. Les modèles micromécaniques développés laissent envisager du fait de leur caractère prédictif la conception de nouveaux matériaux architecturés permettant d'élargir les frontières de l'espace 'matériaux-propriétés'The present thesis deals with the development of micromechanical schemes for the computation of the homogenized response of architectured materials, focusing on periodical lattice materials. Architectured and micro-architectured materials cover a wide range of mechanical properties according to the nodal connectivity, geometrical arrangement of the structural elements, their moduli, and a possible structural hierarchy. The principal objective of the thesis is the consideration of geometrical nonlinearities accounting for the large changes of the initial lattice geometry, due to the small bending stiffness of the structural elements, in comparison to their tensile rigidity. The so-called discrete homogenization method is extended to the geometrically nonlinear setting for periodical lattices; incremental schemes are constructed based on a staggered localization-homogenization computation of the lattice response over a repetitive unit cell submitted to a controlled deformation loading. The obtained effective medium is a micropolar anisotropic continuum, the effective properties of which accounting for the geometrical arrangement of the structural elements within the lattice and their mechanical properties. The non affine response of the lattice leads to possible size effects which can be captured by an enrichment of the classical Cauchy continuum either by adding rotational degrees of freedom as for the micropolar effective continuum, or by considering second order gradients of the displacement field. Both strategies are followed in this work, the construction of second order grade continua by discrete homogenization being done in a small perturbations framework. We show that both strategies for the enrichment of the effective continuum are complementary due to the existing analogy in the construction of the micropolar and second order grade continua by homogenization. The combination of both schemes further delivers tension, bending and torsion internal lengths, which reflect the lattice topology and the mechanical properties of its structural elements. Applications to textiles and biological membranes described as quasi periodical networks of filaments are considered. The computed effective response is validated by comparison with FE simulations performed over a representative unit cell of the lattice. The homogenization schemes have been implemented in a dedicated code written in combined symbolic and numerical language, and using as an input the lattice geometry and microstructural mechanical properties. The developed predictive micromechanical schemes offer a design tool to conceive new architectured materials to expand the boundaries of the 'material-property' space
36
Sitta, Martin. "Montovaná železobetonová konstrukce výrobní haly s administrativou". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265275.
Abstract (sommario):
As the main topic this thesis describes the design and evaluation of selected reinforced concrete members of the prefabricated reinforced concrete industrial building with administration at ultimate limit state in accordance with applicable standards. Movable overhead crane with carrying capacity of 50 tons is the main distinction of the industrial hall. Lateral frame whit main structural parts which are roof prestressed girder, load-bearing column supporting the overhead crane and drilled pile transferring loads from the upper construction to the load bearing subsoil, is designed in particular. Furthermore, design of the Gerber beam which forms the slab construction in the administrational part of the building is elaborated. Structural design and evaluation of other structures of the building is not part of this thesis.
37
Vyhnalíková, Kateřina. "Betonová konstrukce krytého parkoviště pro bytové domy". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240439.
Abstract (sommario):
The aim of diploma thesis is a design and an assessment of selected structural elements of one floor in monolithic concrete structures serving as covered parking for an apartment house. Software RFEM is used here to calculate internal forces. The thesis also includes manual calculation of internal forces and comparison with software results. It also includes drawings of proposed solution. All calculation are done in accordance with Eurocode 2.
38
Subramani, Manoj. "Dynamic response of porous ductile materials containing cylindrical voids". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0310.
Abstract (sommario):
La rupture des matériaux ductiles résulte de l’interaction de trois mécanismes, à savoir la nucléation, la croissance et la coalescence des vides. Dans ce doctorat, nous nous intéressons à l’endommagement des matériaux poreux par croissance de vides cylindriques, sous chargement dynamique. Cette étude a un intérêt particulier notamment pour l’atténuation des ondes de choc dans le cadre de la protection des structures. Par ailleurs, du fait du développement de la fabrication additive, la conception de matériaux contenant des vides cylindriques est une voie possible pour créer des matériaux légers à haut pouvoir dissipatif. Ce travail s’attèle à décrire le comportement dynamique de matériaux architecturés tels que des nids d’abeille faiblement poreux. En conditions dynamiques, les vides sont soumis à une expansion rapide, induisant localement (au voisinage de la cavité) de très fortes accélérations. Cet effet d’inertie locale, ou micro-inertie, est connu pour influencer fortement la réponse macroscopique mais aussi le développement de la porosité. En fait, il a été montré précédemment que le tenseur des contraintes macroscopiques est la somme d’un tenseur des contraintes statiques (dans le sens indépendant de la micro inertie) et d’un tenseur des contraintes dynamiques. Ce dernier terme va contenir toutes les informations liées aux accélérations et sera intrinsèquement relié à la microstructure (taille et forme des vides). Dans ce travail, un volume élémentaire représentatif cylindrique est adopté (rayons interne a et externe b, hauteur 2l). Les contraintes statiques dérivent d’un modèle de la littérature. Les contraintes dynamiques sont évaluées à partir d’un champ cinématiquement admissible. On observe in fine que les contraintes dynamiques sont proportionnelles à la masse volumique de la matrice, sont liées à la porosité, au tenseur vitesse de déformation de manière quadratique, à sa dérivée temporelle de manière linéaire mais surtout fait intervenir deux longueurs internes (rayon interne du vide et longueur de celui-ci). Pour des chargements axisymétriques, on montre que les contraintes dynamiques dans le plan ne dépendent que du rayon du vide alors que les contraintes dynamiques hors plan font apparaître les deux longueurs internes. Les prédictions du modèle ont été testées en considérant de nombreux exemples parmi lesquels le chargement sphérique, en contraintes planes, déformations planes, traction uniaxiale, chargement biaxial. En déformation plane sous chargement axisymétrique, le modèle quasi-statique prédit que le tenseur des contraintes associé est sphérique. En chargement dynamique, en revanche la contrainte axiale est différente de la composante radiale. Nous avons aussi observé pour un chargement sphérique que l’accroissement de la porosité résulte d’une augmentation du rayon du vide et d’une diminution du rayon externe du VER. Cette observation est propre aux effets de micro-inertie. De nombreuses tendances originales sont illustrées dans ce document. A noter que l’ensemble des prédictions du modèle a été validé par confrontation avec des calculs éléments finis sur des cellules élémentaires cylindriquesThe fracture of ductile materials is often the result of the nucleation, growth and coalescence of microscopic voids. In this thesis, we mainly focus on the dynamic void evolution in porous media containing cylindrical voids. This study covers a problem that is of particular interest in many areas of research (e.g. development of shock mitigation devices for civil or military applications). Owing to the development of additive manufacturing, the processing of porous material with cylindrical voids is an option to create lightweight materials having interesting properties in terms of energy dissipation. Therefore, our work aims at describing the dynamic response of architectured materials such as honeycomb structures. In dynamic loading, microvoids sustain an extremely rapid expansion which generates strong acceleration of particles in the vicinity of cavities. These micro-inertia effects are known to play a significant role in the macroscopic response and the development of damage in porous media. In fact, the overall macroscopic stress is found to be the sum of two contributions: a static term (micro-inertia independent term) and a dynamic term (micro-inertia dependent term), the latter being related to the microstructure (e.g. size and aspect ratio of voids). In our work, a cylindrical shell is adopted as a Representative Volume Element (internal and external radii a and b, length 2l) for the porous material. The static term is derived from a yield function available in the literature. The dynamic stress is evaluated analytically using a trial velocity field for cylindrical voids combined with the multi-scale approach developed in the literature in LEM3. It is shown that the dynamic stress is scaled by the mass density, two characteristic lengths of the voids, the porosity, the macroscopic strain rate tensor and the time derivative of the strain rate tensor. An important outcome of the model is the differential lengthscale effect which exists between in-plane and out of plane components of the macroscopic stress. Namely, it is observed for axisymmetric loading that in-plane dynamic stress components are only related to the void radius a while the out of plane stress component is linked to a and the length of the RVE, l. In the thesis, we present the dynamic response of the porous medium when subjected to various loading conditions: spherical loading, axisymmetric plane strain loading, uniaxial loading and biaxial loading. While for plane strain loading under quasi static condition, the overall axial stress is spherical, in dynamic conditions, the inertia contribution hinders the overall stress tensor from being spherical. Another important result of the proposed theory is the effect of the void length, which does not exist in quasi static conditions where the overall response is solely modulated by the porosity. The case of thin cylinders under dynamic loading reveals a peculiar damage kinetics. In fact, the damage developed in such porous materials results from an increase of the void radius and a reduction of the external radius. The void collapse for uniaxial as well as for biaxial loadings are new observations. The analytical model predictions are validated based on comparisons with finite element calculations (Abaqus/Explicit)
39
Pevner, Jan. "Nadzemní parkovací dům". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226965.
Abstract (sommario):
The work focuses on the design and assessment of selected structural elements of one overground floor monolithic concrete structures and staircases. All calculations are done in accordance with Eurocode 2.
40
Hájek, Jan. "Projekt podzemních garáží v Brně". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225505.
Abstract (sommario):
The goal of the project is behaviour and dimensioning of selected monolithic concrete structure elements. Design and assessment of the building foundation was made. Slabs of the floors are dimensioned in detail. All computations are made in accordance with Eurocode 2. Drawing documentation is part of this project.
41
Štys, Jiří. "Implementace statistických kompresních metod". Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2013. http://www.nusl.cz/ntk/nusl-413295.
Abstract (sommario):
This thesis describes Burrow-Wheeler compression algorithm. It focuses on each part of Burrow-Wheeler algorithm, most of all on and entropic coders. In section are described methods like move to front, inverse frequences, interval coding, etc. Among the described entropy coders are Huffman, arithmetic and Rice-Golomg coders. In conclusion there is testing of described methods of global structure transformation and entropic coders. Best combinations are compared with the most common compress algorithm.
42
Makhalova, Tatiana. "Contributions à la fouille d'ensembles de motifs : des données complexes à des ensembles de motifs signifiants et réutilisables". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0124.
Abstract (sommario):
Nous étudions différents aspects de l’exploration ou fouille de motifs dans des jeux de données tabulaires binaires et numériques. L’objectif de l’exploration de motifs est de découvrir un petit ensemble de motifs non redondants qui peuvent recouvrir presque entièrement un ensemble de données et être interprétés comme des unités de connaissances significatives et utiles. Nous nous concentrons sur les questions clés telles que la définition formelle de l’intérêt des motifs, la minimisation de l’explosion combinatoire des motifs, la définition de mesures pour évaluer les performances des méthodes d’exploration de motifs, et le rapprochement entre l’intérêt et la qualité des ensembles de motifs. Nous proposons une structure dite “de niveaux de fermetures” et l’algorithme GDPM qui la calcule. Cette structure nous permet d’estimer à la fois la complexité des données et celle des motifs. En pratique, cette structure peut être utilisée pour représenter la topologie des données par rapport à une mesure d’intérêt. Du point de vue conceptuel, cette structure autorise un analyste à comprendre la configuration intrinsèque des données avant de sélectionner une mesure d’intérêt plutôt que de comprendre les données au moyen d’une mesure d’intérêt choisie arbitrairement. Nous discutons également de la différence entre l’intérêt et la qualité des ensembles de motifs. Nous proposons d’adopter les bonnes pratiques de l’apprentissage supervisé et de les adapter à la fouille de motifs. Ainsi, nous avons développé un algorithme d’exploration d’ensembles de motifs appelé KeepItSimple, qui met en relation l’intérêt et la qualité des ensembles de motifs et qui permet de retrouver de façon efficace un ensemble de motifs intéressants sans craindre d’explosion combinatoire. De plus, nous proposons un algorithme glouton d’énumération de motifs susceptibles d’intérêt qui remplace les méthodes classiques d’énumération de motifs fermés fréquents lorsque les motifs sont trop nombreux. Enfin une dernière contribution porte sur le développement d’un algorithme qui s’appuie sur le principe MDL appelé Mint qui a pour objectif d’extraire des ensembles de motifs dans les données numériques. Il repose sur des bases théoriques solides tout en ayant l’objectif pratique de retourner un ensemble concis de motifs numériques qui sont non redondants et informatifs. Les expérimentations montrent que Mint surpasse généralement ses concurrents en efficacité et qualité des motifs retournésIn this thesis, we study different aspects of pattern mining in binary and numerical tabular datasets. The objective of pattern mining is to discover a small set of non-redundant patterns that may cover entirely a given dataset and be interpreted as useful and significant knowledge units. We focus on some key issues such as (i) formal definition of pattern interestingness, (ii) the minimization of pattern explosion, (iii) measure for evaluating the performance of pattern mining, and (iv) the discrepancy between interestingness and quality of the discovered pattern sets. Moreover, we go beyond the typical perspectives of pattern mining and investigate the intrinsic structure underlying a tabular dataset. The main contributions of this research work are theoretical, conceptual, and practical. Regarding the theoretical novelty, we propose a so-called closure structure and the GDPM algorithm for its computing. The closure structure allows us to estimate both the data and pattern complexity. Furthermore, practically the closure structure may be used to represent the data topology w.r.t. an interestingness measure. Conceptually, the closure structure allows an analyst to understand the intrinsic data configuration before selecting any interestingness measure rather than to understand the data by means of an arbitrarily selected interestingness measure. In this research work, we also discuss the difference between interestingness and quality of pattern sets. We propose to adopt the best practices of supervised learning in pattern mining. Based on that, we developed an algorithm for itemset mining, called KeepItSimple, which relates interestingness and the quality of pattern sets. In practice, KeepItSimple allows us to efficiently mine a set of interesting and good-quality patterns without any pattern explosion. In addition, we propose an algorithm for a greedy enumeration of likely-occurring itemsets that can be used when frequent closed itemset miners return too many itemsets. The last practical contribution consists in developing an MDL-based algorithm called Mint for mining pattern sets in numerical data. The Mint algorithm relies on a strong theoretical foundation and at the same time has a practical objective in returning a small set of numerical, non-redundant, and informative patterns. The experiments show that Mint has very good behavior in practice and usually outperforms its competitors
43
McNamee, Jeff. "Accuracy of momentary time sampling a comparison of varying interval lengths using SOFIT /". 2004. http://www.oregonpdf.org.
Abstract (sommario):
Thesis (Ph. D.)--Oregon State University, 2004.Includes bibliographical references (leaves 41-49). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.
44
McNamee, Jeff B. "Accuracy of momentary time sampling : a comparison of varying interval lengths using SOFIT". Thesis, 2003. http://hdl.handle.net/1957/30142.
Abstract (sommario):
The U.S. Department of Health and Human Services has made the promotion
of regular physical activity a national health objective, and experts believe that
physical education can play a significant role in the promotion of physical activity.
Feasible measurement tools to assess physical activity behavior, by physical
educators, are lacking. One validated instrument is the System for Observing Fitness
Instruction Time (SOFIT; McKenzie, Sallis & Nader, 1991). SOFIT's physical
activity data are collected using momentary time sampling (MTS) with a 20-second
interval length and provide estimates of Moderate to Vigorous Physical Activity
(MVPA). Whether variations in interval lengths would adversely affect the accuracy
of the MVPA data has not been investigated. From a clinical perspective, if physical
education teachers are to utilize MTS procedures for on-going assessment they will
require longer time intervals to collect accurate MVPA data. Therefore, this project
sought to determine the accuracy of MVPA levels collected through varying
observation tactics (i.e., 20s, 60s, 90s, 120s, 180s, and random) relative to those
collected through duration recording (DR). Video records of 30 randomly selected
elementary school physical education classes were utilized for this study. Utilizing
modified physical activity codes from SOFIT, the researchers collected MTS data
regarding students' MVPA at varying interval lengths (i.e., 20s, 60, 90s, 120s, 180s,
and random). Three statistical techniques, Pearson-product moment (PPM) correlation
coefficients, Repeated Measures Analysis of Variance (RM ANOVA), and Average
Error (AE), were utilized to demonstrate concurrent validity of the varying interval
lengths. Results demonstrated moderate-low to high correlations between the 20s,
60s, 90s, and random interval lengths and the DR tactic during the total class. The
RM ANOVA indicated similarity between all the varying interval lengths and the DR
tactic for total class observation. The MTS procedure that created the least amount of
AE across classes was the 20s variable followed by the 60s, random, and 90s
variables. These findings build empirical evidence for the use of a 60s, random, and
90s MTS procedure for the purpose of MVPA assessment by physical educators.Graduation date: 2004
45
Lin, Yi-Fan. "Bayesian interval estimation and performance measurement". Thesis, 2019. http://hdl.handle.net/1959.13/1407919.
Abstract (sommario):
Research Doctorate - Doctor of Philosophy (PhD)Background: Quality measurement and reporting systems are used in healthcare internationally. Clinical indicators are increasingly being used to assess, compare and improve the quality of care provided by health care systems. In Australia, the Australian Council on Healthcare Standards records and reports hundreds of clinical indicators nationally across the healthcare system. These indicators are measures of performance in the clinical setting, and are used as a screening tool to help assess whether a standard of care is being met. Existing analysis and reporting of these indicators incorporate Bayesian methods to address sampling variation; however, such assessments are retrospective in nature, reporting upon the previous six or twelve months of data. The use of Bayesian methods within statistical process control for monitoring systems is an important pursuit to support more timely decision-making. Objectives: This thesis aimed to develop and assess a new graphical monitoring tool, similar to a control chart, utilising the benefits of Bayesian hierarchical models, and potentially improving the monitoring of the health care system. Methods: Simulations were developed based upon a factorial design parameter space to compare the traditional Bernoulli CUSUM (BC) chart with three charts utilising the Bayesian paradigm. The first two charts are based on the beta-binomial posterior predictive (BBPP) distribution with each of the more traditional “central” and “highest posterior density” (HPD) interval approaches to define the limits, named BBPPCI and BBPPHPD charts, respectively. The third chart was a Bayesian CUSUM, based on the beta-binomial posterior (BBP) distribution with the traditional Bernoulli CUSUM (BC) chart procedure, named the BBPBC chart. These charts were compared via heat maps, regression models and tree-based models to identify parameter spaces where the new charts were superior to the traditional BC chart, based on in-control and out-of-control average run lengths, assuming that the parameter representing the underlying clinical indicator rate (proportion of cases with an event of interest) required estimation. Results: The in-control ARLs for all charts were very high, exceeding traditional Shewhart charts. The newly developed BBPP chart with HPD interval estimation was found to have the best performance based on the out-of-control ARL (ARLout) for the case of when the underlying parameter changes immediately. The BBPPHPD chart had, on average, a smaller ARLout than the BC chart in 75% of the simulations conducted. Conclusions: Bayesian hierarchical models and the newly developed control charts utilising these models have been shown to offer value to the health care system. These new charts offer improved abilities to detect changes in the system, and can do so in a more timely manner than retrospective system reports. It is recommended that these charts continue to be explored and assessed for a broader parameter space and utilising traditional run rules. A final chapter in the thesis explored a Bayesian approach to a problem surrounding interval estimation that was recently addressed by frequentist methods. The article in question was the result of a practical application requiring inference for the weighted sum of two binomial proportions, which is related to the more common problem of inference for the difference between two proportions. Bayesian credible intervals were derived which perform better than the frequentist-based confidence intervals that were developed for the application, not only in terms of frequentist coverage, but especially in terms of intervals for extreme data outcomes.
46
"Applications of frustrated total internal reflection for short interaction length devices in photonic integrated circuits". SOUTHERN METHODIST UNIVERSITY, 2010. http://pqdtopen.proquest.com/#viewpdf?dispub=3366145.
47
CHANG, LING-CHEN, e 張聆真. "Exploiting the big data analysis to investigate the length of stay for internal medicine patients". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/735zpe.
Abstract (sommario):
碩士國立中正大學
企業管理系研究所
106
The application of big data in the medical/healthcare field is gradually receiving attention. Hospitals and medical institutions are committed to using big data to predict and monitor diseases, optimize resource utilization, reduce healthcare costs, and relieve financial pressure of hospital. Managers and hospital administrators in hospitals also need analyzed data to assist them in making decisions so that patients can receive better medical care. However, in the medical/healthcare field, the amount of data is huge and cluttered. How to gain and choose the valuable data then turns into the biggest challenge at present. Predicting inpatient length of stay (LOS) is an important and necessary measurement to help hospitals or physicians allocate medical resources appropriately. Therefore, we applied data mining algorithms to identify some important variables that may affect the inpatient LOS and compare the accuracy of these algorithms. Data mining can find out the hidden patterns, associations, and knowledge from a large amount of data based on databases, statistics, and machine learning; therefore, we use the classification method in this study. According to the previous studies, predicting the inpatient LOS, this study chose two frequent used data mining algorithms, support vector machine (SVM) and decision tree. We found the significant variables from the 7 variables in our collected dataset, and presented the analysis results of prediction by variables on the decision tree diagram. The significant variables include the main diagnostic code, the second and the third diagnostic codes, and the department of admission and discharge. Observing the comparison between the two models in accuracy, the results show that although the SVM model has high accuracy (93.54%) in the training set, it is far from the accuracy of the testing set (71.34%). The decision tree presents almost the same degree of accuracy between the training set and testing set and is suitable for applying to the actual forecasting.
48
Hsieh, Yong-Hsiang, e 謝詠翔. "Optimal Algorithms for the Interval Location Problem with Range Constraints on Length and Average". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/84227236403823748438.
Abstract (sommario):
博士國立清華大學
資訊工程學系
95
Let A be a sequence of n real numbers, L1 and L2 be two integers such that L1 <= L2 , and R1 and R2 be two real numbers such that R1 <= R2. An interval of A is feasible if its length is between L1 and L2 and its average is between R1 and R2. In this dissertation, we study the following problems: finding all feasible intervals of A, counting all feasible intervals of A, finding a maximum cardinality set of non-overlapping feasible intervals of A, locating a longest feasible interval of A, and locating a shortest feasible interval of A. The problems are motivated from the problem of locating CpG islands of a DNA sequence. Locating CpG islands is important for gene finding as well as for cancer research. In this dissertation, we firstly show that all the problems have an Ω(n log n)-time lower bound in the comparison model. Then, we use geometric approaches to design optimal algorithms for the problems. All the presented algorithms run in an on-line manner and use O(n) space.
49
Hsu, Tsai-Jen, e 許載仁. "Study Of Minimum Length Of Confidence Interval About Chi-Square Distribution And F Distribution". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/30875034150373393960.
Abstract (sommario):
碩士淡江大學
數學學系碩士班
101
This article is to explore the minimum length of confidence interval of F distribution. In 1975, Crisman had mentioned a bisection method to calculate the confidence interval with the minimum length about the Chi-Square distribution to meet the desired critical values. This paper will first explore Crisman’s research and applies the same method on F distribution to find the confidence interval with minimum length, finally we will provide a SAS Macro program and use some examples to illustrate how to use it.
50
曾鈺婷. "Concept of Average Run Length for Coverage Interval & p values for Gene Expression Analysis". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/12876198101850364007.