Dissertations / Theses: 'Modelling math'

1

Techaphulphol, Kanta. "The effects of using video self-modelling and an IPad application on self-efficacy and acquisition of basic math skills in Year 5 students." Thesis, University of Canterbury. Child and Family Psychology/Educational Studies and Leadership, 2014. http://hdl.handle.net/10092/10037.

Full text

Abstract:

This study aimed to examine the effectiveness of video self-modelling (VSM) and the iPad application (Fast Fact Math, FFM) interventions on a group of Year 5 students to increase their knowledge of basic number facts. This study also aimed to measure the intervention group’s self-efficacy levels (Patterns of Adaptive Learning Scales, PALS) before and following the interventions. Participants were drawn from a decile 9 primary school in a suburban area (teaches Year 1 to Year 6). The Test (pre-, mid-, and post-test phases) were administered by a class teacher to all Year 5 students. Following consultation with the teacher, eight students whose scores fell below the 25th percentile were invited to participate in the study. The intervention group took a specific level test to ascertain their basic number facts performance on all four operations (addition, subtraction, multiplication, and division). The videos and the FFM app were personalised to each intervention group’s members in an effort to elicit from the errors that they made on specific level test. At the completion of each intervention sessions, session probes were conducted. Meanwhile, the researcher gave a self-efficacy test (PALS) to the participants before and following intervention phases. Results showed that, although more than half of the intervention group increased their basic number fact performance level following the interventions, their overall self-efficacy rating on PALS did not change. Results also showed that VSM is a time-efficient and rapid learning method to use with the intervention group as opposed to the iPad app, which took two times longer to complete a session. Further areas of study are suggested.

APA, Harvard, Vancouver, ISO, and other styles

2

Franco, Dionys Fabrício Soares. "Qualidade hídrica da bacia do córrego do cerrado/cadunga no município de Canápolis (MG)." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/7613.

Full text

Abstract:

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-07-25T12:37:47Z No. of bitstreams: 2 Dissertação - Dionys Fabrício Soares Franco - 2016.pdf: 7802481 bytes, checksum: 3fdd105e5ba06583ec207cb01e0a71f0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-26T11:49:52Z (GMT) No. of bitstreams: 2 Dissertação - Dionys Fabrício Soares Franco - 2016.pdf: 7802481 bytes, checksum: 3fdd105e5ba06583ec207cb01e0a71f0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2017-07-26T11:49:52Z (GMT). No. of bitstreams: 2 Dissertação - Dionys Fabrício Soares Franco - 2016.pdf: 7802481 bytes, checksum: 3fdd105e5ba06583ec207cb01e0a71f0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-09-02
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
The water is becoming the reason of worrie in the actual context current Brazilian and global water environment; pollution levels and pollution has reached alarming levels, and the same proportion is increasing, its demand in this sense is used to show that the quality of water is becoming an important tool for the treatment issue and even for the water´s preservation. Mathematical models have been used over the years for the analysis of several variables, and from these variables measure and transformed into a numerical factor that facilitates their understanding, and turn this procedure able to show the level of degradation from the water to the society and also the government. In this sense this work was to evaluate the level of water quality of the Cerrado Stream Basin \ Cadunga in the municipality of Canápolis / MG, framing it on a scale that goes from excellent to bad, for it was used the methodology proposed by the Canadian Council for the IQA-CCME Environment. This model still little used in Brazil, has the advantage of choosing the variables taking into account the specificities of the place searched, another interesting issue is that the data used for the equation are given based on the indexes of existing and current laws. We were used 10 parameters (variables) to assess the level of degradation of the waters from the Basin Cerrado stream / Cadunga, as follows: temperature, hydrogenionic Potential Electrical Conductivity, Turbidity, Dissolved Oxygen, suspension solids, nitrite, nitrate, ammonia and phosphorus. four campaigns were conducted in different periods for the collection of data regarding the season (spring, summer, autumn and winter) at nine different points of the basin. According to the data evaluated the basin waters are eutrophic with huge problems of pollution being framed as Class tree by CONAMA Resolution 357/2005 and classified according to water quality index proposed by CCME.
A água vem se tornando motivo de preocupação no atual contexto hídrico brasileiro e mundial. Os índices de poluição e contaminação vêm atingindo níveis alarmantes, e na mesma proporção, vem crescendo sua demanda. Neste sentido, trabalhos que demonstrem a qualidade das águas se tornam importantes ferramentas para a questão do tratamento e até mesmo da preservação das águas. Modelos matemáticos vêm sendo utilizados no decorrer dos anos para a análise de diversas variáveis, e a partir destas variáveis mensurar e transformar em um fator numérico que facilite o seu entendimento, para que este, por sua vez, possa mostrar o nível de degradação da água à sociedade e também ao poder público. Neste sentido este trabalho teve por objetivo avaliar o nível da qualidade das águas da Bacia do córrego do Cerrado\Cadunga, no município de Canápolis/MG, enquadrando-o em uma escala que vai de excelente a péssimo. As metodologias utilizadas para realizar a classificação do corpo hídrico estão em acordo com a proposta apresentada pela Resolução CONAMA 357/2005 e pelo Conselho Canadense de Meio Ambiente a partir do índice de qualidade das águas (IQA-CCME). O IQA-CCME é um modelo ainda pouco utilizado no Brasil, e tem a vantagem da escolha das variáveis levando em consideração as especificidades do local pesquisado. Outra questão interessante é que os dados utilizados para a equação são dados baseados nos índices das legislações existentes e vigentes. Foram utilizados 10 parâmetros (variáveis) para avaliar o nível de degradação das águas da Bacia do córrego do Cerrado/Cadunga, sendo: Temperatura, Potencial Hidrogeniônico Condutividade Elétrica, Turbidez, Oxigênio Dissolvido, Sólidos em Suspensão, Nitrito, Nitrato, Amônia e Fósforo. Foram realizadas quatro campanhas para a coleta de dados, referente as estações climáticas primavera, verão, outono e inverno) em nove pontos distintos da bacia. De acordo com os dados avaliados, as águas da bacia se encontram impactadas com enormes problemas de poluição, sendo enquadrado como de classe três.

APA, Harvard, Vancouver, ISO, and other styles

3

Boyaval, Sébastien. "Mathematical modelling and numerical simulation in materials science." Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00499254.

Full text

Abstract:

In a first part, we study numerical schemes using the finite-element method to discretize the Oldroyd-B system of equations, modelling a viscoelastic fluid under no flow boundary condition in a 2- or 3- dimensional bounded domain. The goal is to get schemes which are stable in the sense that they dissipate a free-energy, mimicking that way thermodynamical properties of dissipation similar to those actually identified for smooth solutions of the continuous model. This study adds to numerous previous ones about the instabilities observed in the numerical simulations of viscoelastic fluids (in particular those known as High Weissenberg Number Problems). To our knowledge, this is the first study that rigorously considers the numerical stability in the sense of an energy dissipation for Galerkin discretizations. In a second part, we adapt and use ideas of a numerical method initially developped in the works of Y. Maday, A.T. Patera et al., the reduced-basis method, in order to efficiently simulate some multiscale models. The principle is to numerically approximate each element of a parametrized family of complicate objects in a Hilbert space through the closest linear combination within the best linear subspace spanned by a few elementswell chosen inside the same parametrized family. We apply this principle to numerical problems linked : to the numerical homogenization of second-order elliptic equations, with two-scale oscillating diffusion coefficients, then ; to the propagation of uncertainty (computations of the mean and the variance) in an elliptic problem with stochastic coefficients (a bounded stochastic field in a boundary condition of third type), last ; to the Monte-Carlo computation of the expectations of numerous parametrized random variables, in particular functionals of parametrized Itô stochastic processes close to what is encountered in micro-macro models of polymeric fluids, with a control variate to reduce its variance. In each application, the goal of the reduced-basis approach is to speed up the computations without any loss of precision

APA, Harvard, Vancouver, ISO, and other styles

4

Qi, Rui. "Optimization and optimal control of plant growth : application of GreenLab model for decision aid in agriculture." Phd thesis, Châtenay-Malabry, Ecole centrale de Paris, 2010. http://tel.archives-ouvertes.fr/tel-00494918.

Full text

Abstract:

The objective of the thesis is to improve plant yield through optimization and optimal control based on the GreenLab plant growth model. Therefore, the thesis proposed a methodology for investigation of plant yield improvement，whose characteristics are that (1) investigations are all based on the functional-structural plant growth model GreenLab and (2) heuristic optimization algorithm and optimal control techniques are applied to the plant growth model in order to improve plant yield. By applying optimization techniques on different species of plants (crops or trees) and for different kinds of optimization problems, common characteristics that a plant with high yield should possess were obtained. The optimal results in the thesis revealed the source-sink dynamics during the plant growth. The optimization results can be considered as references to guide breeding for ideotype and to improve cultivation modes. The optimization application of GreenLab could thus be possibly used to the agricultural decision support system.To achieve the aims of the thesis, the thesis investigated the effects of endogenous factors and exogenous environmental factors of plant growth on plant yield separately. First, given environmental conditions, the thesis investigated endogenous factors, and then the thesis did optimal control on exogenous environmental factors given plant genotype. Therefore, the problems investigated in the thesis consist of general optimization problems and optimal control problems.The main contributions of the thesis include following issues: According to the species of plants, single optimization problems, multi-objective optimization problems and optimization problems with constraints with respect to plant endogenous factors were formulated and investigated, in order to find the ideotype of plants with high plant yield. A population based algorithm is more suitable for the optimization problems in this thesis. Due to its better performance compared with other heuristic optimization algorithms, all optimization problems were solved by a population-based, heuristic optimization algorithm, namely Particle Swarm Optimization (PSO). Optimal control on the pruning strategy was formulated and investigated in the thesis. As GreenLab can be considered as discrete dynamic system and the objective function of the optimal control problem is analytical, the gradient based method, which is based on the variational approach and Lagrange theory, was used to solve the optimal control problem. Moreover, the optimal solutions were compared with the ones found by PSO, in order to validate the PSO method. The insect population dynamics was modeled mathematically, which was compatible with the plant model GreenLab in terms of spatial and temporal scales, to study the effect of biotic factors on plant growth. The interaction among plants, pests and auxiliaries was implemented, and the ecosystem model, which involves the three tri-trophic components, was thus developed in the thesis. The tri-trophic ecosystem model can simulate the insect population dynamics and the plant growth with consideration of the interaction of insects. Moreover, the tri-trophic ecosystem model considered the partition of individuals in the insect population among plant organs, which is not taken into account in the previous works. A global sensitivity analysis method Morris method was used to analyze the most important parameters and the least influential parameters to model outputs of interest. Through optimization on pest management techniques, the optimal strategies of the application of the pest management techniques were obtained. Estimation of GreenLab parameters with about 400 sets of observation data of 44 tomato genotypes was done in the thesis, by using a generalized non-linear least square algorithm. Taking the estimated parameter values as parameter space, the GreenLab model parameters were optimized, in order to maximize the fruit yield. Through the analysis of the correlation of estimated and optimal parameters with the fruit yield by statistical analysis methods, the most important parameters that result in the difference of fruit yield were found. According to the correlation and optimization results, the phenotypic differences among genotypes were explained from the physiological point of view.

APA, Harvard, Vancouver, ISO, and other styles

5

Kaczmarek, Derli. "MODELAGEM NO ENSINO DA MATEMÁTICA: UM VIÉS NA AÇÃO E INTERAÇÃO DO PROCESSO DE ENSINO E APRENDIZAGEM." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/1369.

Full text

Abstract:

Made available in DSpace on 2017-07-21T20:32:06Z (GMT). No. of bitstreams: 1 DERLI KACZMAREK.pdf: 3307495 bytes, checksum: 32d28e7c1d4e9fdf6a68e3567b56a745 (MD5) Previous issue date: 2014-03-24
The goal of this paper is to describe the actions and interactions of the students afforded by activities of Math Modelling and to establish possible relations with the Vygotsky's Theory. This way, the question put in investigation has been defined like this: what are the actions and interactions of the students identified in the activities of Math Modelling as from of Vygotsky's reference? Therefore, were described two activities developed using the Math Modelling assuming the conception adopted for Burak (2010). The data collect was realized in a public school in Araucária, in the metropolitan region of Curitiba, state of Paraná, local of work of the teacher and researcher. The research subjects are students from regular middle school, a 8th grade class and a 5th grade class, involving a total of 57 students. The notes in the diary field the activities development and of the comments held, the activities produced by students and their testimony, are part of this material of analisys. The research and the data treatment, putting emphasys on qualitative aspects, are ruled by Bogdan's and Biklen's perspectives (1994). The actions and interactions noticed and invariable in the data collected were discussed in Vygotsky's theory (2007; 2004; 1991; 1988). The signifiers from actions and interactions were considered as from the four-phase model of interest development proposed by Hidi and Renninger (2006), classified as Triggered Situational Interest, Maintained Situational Interest, Emerging Individual Interest, and Individual Interest. The actions classified signalize the process of the internalization the way of think and act, launched in relations with another one - the learning impelling the development. This way, actions noticed by the students, like learn, know, understand, measure, do, think, invent and talk, e.g., show themselves in Individual Interest as result of the Triggered Situational Interest generated by the environment of choice of theme of interest and the shared development of activities - in interactions. This fact corroborated the interest prominence and the other person's role in the individual development. It follows that the Math Modelling tie itself straightly in the Vygotsky's principles, and one is "What the child is able to do with assistance today, will do tomorrow alone". This is the path in the action and interaction in teaching learning mediated by Math Modelling.
Este trabalho tem por objetivo descrever as ações e interações dos estudantes proporcionadas pelas atividades da Modelagem Matemática e estabelecer possíveis relações com a Teoria de Vygotsky. Dessa forma, a questão colocada à investigação ficou assim definida: Que ações e interações, dos estudantes, são identificadas nas atividades de Modelagem Matemática a partir do referencial Vygotskyano? Para tanto, foram descritas duas atividades desenvolvidas utilizando-se a Modelagem Matemática assumindo-se a concepção adotada por Burak (2010). A coleta dos dados foi realizada em uma escola pública municipal de Araucária, região metropolitana de Curitiba-Pr, local de trabalho da professora e pesquisadora. Os sujeitos da pesquisa são estudantes do Ensino Fundamental regular, sendo uma turma de nono ano e outra turma de sexto ano, envolvendo um total de 57 estudantes. As anotações no diário de campo do desenvolvimento das atividades e das observações realizadas, as atividades produzidas pelos estudantes e os seus depoimentos, fazem parte do material de análise. A pesquisa e o tratamento de dados, com ênfase em aspectos qualitativos, são pautados na perspectiva de Bogdan e Biklen (1994). As ações e as interações, percebidas e constantes nos dados coletados, foram tratadas na perspectiva da teoria de Vygotsky (2007; 2004; 1991; 1988). Os significantes, das ações e interações, foram considerados a partir do modelo de quatro fases do desenvolvimento do interesse, proposto por Hidi e Renninger (2006), categorizadas nos focos de interesse de Motivação (ambiente), Sustentação Externa (tarefas significativas), Mobilização (emergência do interesse pessoal) e Aprendizagem Autônoma. As ações categorizadas sinalizaram o processo de internalização do modo de pensar e agir, iniciados nas relações com o outro – o aprendizado impulsionando o desenvolvimento. Dessa forma, ações pontuadas pelos estudantes, como aprender, conhecer, entender, medir, fazer, pensar, inventar e falar, por exemplo, se refletiram em Aprendizagem Autônoma em decorrência da Motivação gerada pelo ambiente da escolha do tema de interesse e do desenvolvimento compartilhado das atividades – nas interações. Este fato corroborou a relevância do interesse e do papel do outro no desenvolvimento individual. O que se conclui é que a Modelagem Matemática liga-se estreitamente aos postulados de Vygotsky de que ―aquilo que a criança é capaz de fazer com a assistência hoje, ela será capaz de fazer sozinha amanhã‖: esse é o viés na ação e interação do processo de ensino e aprendizagem mediado pela Modelagem Matemática. Palavras-chave: Modelagem Matemática; Ações e Interações; Vygotsky; Ensino e Aprendizagem.

APA, Harvard, Vancouver, ISO, and other styles

6

Tazzyman, S. J. "Modelling the evolution and consequences of mate choice." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/814889/.

Full text

Abstract:

This thesis considers the evolution and the consequences of mate choice across a variety of taxa, using game theoretic, population genetic, and quantitative genetic modelling techniques. Part I is about the evolution of mate choice. In chapter 2, a population genetic model shows that mate choice is even beneficial in self-fertilising species such as Saccharomyces yeast. In chapter 3, a game theoretic model shows that female choice will be strongly dependent upon whether the benefits are fixed, so that females receive the same fitness boost from a mating with a given male regardless of how many matings that male has, or dilutable, where the more females a male mates with, the lower the expected benefit to each. This leads to the prediction that mating skew should be higher in species in which the benefits of mate choice are hypothesised to be due to good genes. Part II is about the consequences of mate choice. The theoretical prediction from chapter 3 is borne out by a literature review of studies of wild populations of birds in chapter 4. In chapter 5, a quantitative genetic model about poison-dart frogs suggests that sexual selection can speed up the effect of random genetic drift. This may be of more general importance, further widening the evolutionary impact of sexual selection. Finally, in chapter 6, a game theoretic model of sperm competition shows that pre-copulatory mate choice can also have evolutionary effects upon post-copulatory behaviour, affecting the optimal ejaculate expenditure of males. Overall, mate choice is shown to be an important evolutionary force, with wide-ranging ramifications across diverse taxa, and eects so varied as to include the evolution of sex, the genetic variation in species, speciation, and post-copulatory behaviour, amongst others. These effects can be effectively explored using mathematical modelling.

APA, Harvard, Vancouver, ISO, and other styles

7

Olivier, Julien. "Fluides vitreux, sutures craniofaciales, diffusion réactive : quelques contributions à l'étude de ces systèmes multi-échelles ou singuliers." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00625455.

Full text

Abstract:

On s'attache à étudier des modèles mathématiques multi-échelles pour des domaines variés : la rhéologie des matériaux vitreux, la biochimie dans la balnéothérapie et la biomécanique des sutures craniofaciales. Pour les matériaux vitreux, nous étudions un modèle de type cinétique et justifions mathématiquement des propriétés macroscopiques (transition vitreuse à faible cisaillement et comportement de type fluide newtonien à fort taux de cisaillement) après avoir remarqué une certaine analogie avec la pénalisation d'obstacles en mécanique des fluides. Nous proposons également une généralisation multi-dimensionnelle de ce modèle afin de prendre en compte des types d'écoulements généraux. En biochimie nous présentons un premier modèle très simplifié de réaction-diffusion et montrons comment concevoir un schéma numérique adapté en utilisant les hypothèses de modélisation. Enfin nous proposons un modèle de couplage biomécanique pour le développement des sutures qui rend compte du phénomène d'interdigitation que l'on observe en pratique.

APA, Harvard, Vancouver, ISO, and other styles

8

Gallo, Ignacio Alejandro <1981&gt. "An equilibrium approach to modelling social interaction." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2126/.

Full text

Abstract:

The aim of this work is to put forward a statistical mechanics theory of social interaction, generalizing econometric discrete choice models. After showing the formal equivalence linking econometric multinomial logit models to equilibrium statical mechanics, a multi- population generalization of the Curie-Weiss model for ferromagnets is considered as a starting point in developing a model capable of describing sudden shifts in aggregate human behaviour. Existence of the thermodynamic limit for the model is shown by an asymptotic sub-additivity method and factorization of correlation functions is proved almost everywhere. The exact solution for the model is provided in the thermodynamical limit by nding converging upper and lower bounds for the system's pressure, and the solution is used to prove an analytic result regarding the number of possible equilibrium states of a two-population system. The work stresses the importance of linking regimes predicted by the model to real phenomena, and to this end it proposes two possible procedures to estimate the model's parameters starting from micro-level data. These are applied to three case studies based on census type data: though these studies are found to be ultimately inconclusive on an empirical level, considerations are drawn that encourage further refinements of the chosen modelling approach, to be considered in future work.

APA, Harvard, Vancouver, ISO, and other styles

9

Lin, C. A. "Computational study of compressibility effects in two-dimensional steady turbulent junction flow at high subsonic mach numbers." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380181.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Massip, Florian. "The Statistical Fate of Genomic DNA : Modelling Match Statistics in Different Evolutionary Scenarios." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS008/document.

Full text

Abstract:

Le but de cette thèse est d'étudier la distribution des tailles des répétitions au sein d'un même génome, ainsi que la distribution des tailles des appariements obtenus en comparant différents génomes. Ces distributions présentent d'importantes déviations par rapport aux prédictions des modèles probabilistes existants. Étonnamment, les déviations observées sont distribuées selon une loi de puissance. Afin d'étudier ce phénomène, nous avons développé des modèles mathématiques prenant en compte des mécanismes évolutifs plus complexes, et qui expliquent les distributions observées. Nous avons aussi implémenté des modèles d'évolution de séquences in silico générant des séquences ayant les mêmes propriétés que les génomes étudiés. Enfin, nous avons montré que nos modèles permettent de tester la qualité des génomes récemment séquencés, et de mettre en évidence la prévalence de certains mécanismes évolutifs dans les génomes eucaryotes
In this thesis, we study the length distribution of maximal exact matches within and between eukaryotic genomes. These distributions strongly deviate from what one could expect from simple probabilistic models and, surprisingly, present a power-law behavior. To analyze these deviations, we develop mathematical frameworks taking into account complex mechanisms and that reproduce the observed deviations. We also implemented in silico sequence evolution models that reproduce these behaviors. Finally, we show that we can use our framework to assess the quality of sequences of recently sequenced genomes and to highlight the importance of unexpected biological mechanisms in eukaryotic genomes

APA, Harvard, Vancouver, ISO, and other styles

11

Pollock, Jeffrey. "Statistical modelling and Bayesian inference for match outcomes and team behaviour in association football." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3097.

Full text

Abstract:

This thesis presents advances in modelling and inference for match outcomes in the association football English Premier League. We firstly extend earlier models by introducing a behavioural aspect which can be used to investigate how teams react to the state of play in a match. We show that the model, in its simplest form, outperforms existing models and is able to select a portfolio of pro table bets against a bookmaker. Secondly, we introduce a dynamic component to the model by allowing team ability parameters to vary stochastically in time. We employ particle filtering methods to cope with a mixture of static and dynamic parameters and find that the updating of posterior distributions is particularly fast, a necessary attribute should we wish to update parameter estimates while matches are in-play. Furthermore, it is shown that the methods are able to recover model parameters based on simulated league data. Finally, we propose an extension to the model so that we are able to investigate how a team modifies its behaviour based on their league situation. We consider league positions that are closely attainable and suggest that since teams modify their behaviour based on their current league position, outcomes of different matches are not necessarily independent.

APA, Harvard, Vancouver, ISO, and other styles

12

Haapala, Jari. "Modelling of the seasonal ice cover of the Baltic Sea." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/geofy/vk/haapala/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Mapagha, Saül. "Qualification de la prédiction du comportement vibratoire d'un sous-système sur véhicule." Phd thesis, INSA de Rouen, 2010. http://tel.archives-ouvertes.fr/tel-00557906.

Full text

Abstract:

Le présent travail de thèse porte sur la prédiction des efforts vibratoires transmis à l'interface entre deux structures mécaniques. L'étude relève de la dynamique des structures en basses fréquences et concerne des aspects relatifs à la modélisation de couplages structuraux, notamment en présence de paramètres incertains et d'aspects expérimentaux. Les équipements automobiles actifs sont des sources vibratoires qui agissent sur la structure d'accueil (souvent le châssis) sur laquelle ils sont montés. La maîtrise, a priori, du champ vibratoire (et donc acoustique) de l'assemblage, suppose la prédiction des efforts vibratoires à l'interface équipement/structure d'accueil. Le formalisme utilisé pour décrire le couplage entre sous-systèmes permet d'établir que la recherche, dans des situations pratiques, des efforts appliqués à l'accueil est un problème inverse. Une méthode prédictive des efforts est construite et validée par une mise en œuvre expérimentale. Pour que les efforts vibratoires transmis respectent un gabarit imposé a priori, un problème d'optimisation numérique de l'interface est proposé et résolu. Il sera montré que pour l'interface ainsi optimisée, la dispersion de la norme des efforts transmis est systématiquement plus faible que pour l'interface nominale.

APA, Harvard, Vancouver, ISO, and other styles

14

Ennari, Jaana. "Atomistic molecular modelling of PEO sulfonic acid anion based polymer electrolytes." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/ennari/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Zhang, Zhanhai. "On modelling ice dynamics of semi-enclosed seasonally ice-covered seas." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/geofy/vk/zhang/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Helaja, Juho. "Structural analysis of natural chlorin derivatives utilizing NMR spectroscopy and molecular modelling." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/helajaj/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Popelková, Ilona. "Purpurové řeky Matematické modelování výkonnosti podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2008. http://www.nusl.cz/ntk/nusl-221785.

Full text

Abstract:

This master's thesis discourse the proposal of the strategy of increasing efficiency of the enterprise. It includes the analysis of the present efficiency level of the company and also a file of math-economical issues, like the riverbed of interconnected flows, whose correct modelling will improve the current entrepreneurial situation.

APA, Harvard, Vancouver, ISO, and other styles

18

Buck-Sorlin, Gerhard Hartwig. "Crown architecture and modelling of oak (Quercus robur L., Q.petraea (Matt.) Liebl.) and sycamore (Acer pseudoplatanus L.)." Thesis, Bangor University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361257.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Boscolo, Danilo. "Influência da estrutura da paisagem sobre a persistência de três espécies de aves em paisagens fragmentadas da Mata Atlântica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-13022008-180423/.

Full text

Abstract:

A perda e fragmentação de habitats são, atualmente, as principais ameaças à conservação da biodiversidade. Espécies que outrora tinham sua distribuição contínua são forçadas a sobreviver de forma segmentada, em populações menores e mais susceptíveis à extinção. Segundo a teoria de metapopulações, se extinções locais em fragmentos específicos puderem ser compensadas por recolonizações provenientes de populações adjacentes, uma espécie pode persistir apesar da fragmentação. Extinções e recolonizações são processos que dependem da estrutura da paisagem. Fragmentos pequenos e com baixa qualidade de habitat possuem maior probabilidade de extinção, assim como paisagens pouco conectadas e com alta resistência à dispersão de indivíduos têm menores taxas de recolonização. Modelos de dinâmica populacional espacialmente explícitos (MVPEE) possibilitam a análise da influência de diferentes tipos de paisagens sobre a persistência de espécies, contribuindo na decisão de estratégias para sua conservação. Esta tese teve o objetivo de identificar os fatores que afetam a persistência de três espécies de aves florestais endêmicas à Mata Atlântica (Chiroxiphia caudata, Xiphorhyncus fuscus e Pyriglena leucoptera) através de um MVPEE. Foram estudadas quatro paisagens do Planalto Atlântico de São Paulo que possuem florestas fragmentadas. A técnica de play-back foi utilizada para atestar a presença ou ausência das aves em 80 fragmentos dispersos por essas paisagens. Esses dados foram utilizados para gerar modelos logísticos de incidência capazes de estimar sua probabilidade de ocorrência de acordo com a cobertura e arranjo espacial da paisagem circundante. Ademais, o padrão de movimentação das aves entre fragmentos florestais foi determinado através de experimentos de play-back que as induziu a transpor a matriz, e pela translocação de indivíduos acompanhados por radio-telemetria. Os modelos de incidência indicaram que a probabilidade de ocorrência das aves em locais de matas fragmentadas depende em larga escala da distribuição espacial dos remanescentes florestais, sendo maior em locais onde o isolamento dos fragmentos é baixo. Esse efeito torna-se ainda mais importante em locais onde os fragmentos não são grandes o suficiente para prover as aves com todos os recursos necessários, forçando-as a buscá-los em matas adjacentes, mas não muito distantes entre si a ponto de coibir sua movimentação. Essa capacidade das aves de transpor a matriz inter-habitat, alcançando florestas próximas, foi confirmada pelos estudos de movimentação. As espécies estudadas são capazes de se movimentar entre fragmentos florestais próximos, mostrando-se ainda capazes de utilizar corredores de habitat ou árvores isoladas para facilitar sua passagem pela paisagem. Esses resultados indicam que os territórios das espécies estudadas podem incluir fragmentos isolados, porém funcionalmente conectados pela movimentação das aves, sendo que as condições mínimas para o estabelecimento destes territórios em termos de quantidade e espaçamento das florestas variam em função da espécie. Esses resultados, somados às informações bibliográficas sobre a biologia das espécies estudadas, foram utilizados para guiar a construção de um MVPEE ecologicamente calibrado, onde as células da paisagem foram definidas como sendo os territórios potenciais das aves. Esse modelo de viabilidade se mostrou de grande utilidade para avaliar os efeitos de variações estruturais da paisagem sobre a persistência de populações de pequenas aves territoriais. Simulações conduzidas tanto com paisagens artificiais como reais indicaram que, em uma escala espacial ampla, a persistência dessas espécies está em grande parte sujeita à quantidade de territórios que a paisagem pode suportar, mas não à sua agregação. No entanto, o aumento da densidade de florestas na paisagem leva a um aumento na quantidade de territórios possíveis, afetando positivamente a persistência das espécies. O MVPEE desenvolvido para esta tese permitiu conciliar uma análise estrutural de paisagens com a modelagem de dinâmicas populacionais, o que é considerado como um dos assuntos prioritários de pesquisa em ecologia de paisagens.
Habitat loss and fragmentation are currently the most important threats to the conservation of biodiversity. These processes may generate patchy landscapes where several species are forced to survive in small and isolated populations, which are very susceptible to local extinctions. According to the metapopulation theory, if local extinctions in specific patches can be compensated by re-colonization from surrounding populations, a species can persist despite fragmentation. Extinctions and re-colonizations are processes that depend directly on landscape structure. Small patches with low habitat quality have increased extinction probabilities, while poorly connected landscapes with high resistance to the dispersal of individuals have decreased re-colonization rates. Spatially explicit population viability models (SEPVM) allow analyses of the influence of different types of landscapes on the persistence of species, contributing to conservation strategies decision making. The objective of the current thesis was to identify the factors which affect the persistence of three forest bird species endemic to the Atlantic forest (Chiroxiphia caudata, Xiphorhynchus fuscus and Pyriglena leucoptera) through a SEPVM. Four different fragmented landscapes of the Atlantic plateau of São Paulo were chosen for this study. The playback technique was used to assess the incidence of the birds inside 80 forest fragments in these landscapes. These data were used to derive logistic incidence models to estimate their occurrence probabilities according to the cover and spatial pattern of the surrounding landscape. Furthermore, the movement pattern of the birds between forest fragments was inferred from playback experiments which induced birds to overcome the matrix, and through the translocation of individual birds which were followed by radio-telemetry. The incidence models indicated that the occurrence probability of the birds in places of fragmented habitat depends in large scale on the spatial distribution of forest remnants, being higher where patch isolation is low. This effect becomes even more important in places where habitat patches are not big enough to provided the birds with sufficient resources, forcing them to search for it in nearby forests, which shall not be further away than the birds\' aptitude to move through the landscape. Their ability to overcome the inter-habitat matrix, reaching close by forests, was confirmed by the experiments on individuals\' movements. The studied species are able to move between nearby forest patches, being even able to use habitat corridors or isolated trees to ease their passage through the landscape. These results indicate that the territories of the studied species can include isolated patches which are connected by birds\' movement. Also, the minimum conditions to the establishment of these territories in terms of amount and aggregation of forests varies according to the species. These results, added to bibliographical information on the studied birds\' biology, were used to guide the development of an ecologically scaled SEPVM, in which the landscape cells were defined as potential bird territories. This viability model was greatly useful to assess the effects of landscape structural changes on the persistence of small territorial birds\' populations. Simulations using both artificial and real landscapes indicated that, in a wide landscape scale, the persistence of these species is largely subjected to the amount of territories the landscape can bear, but not to its aggregation. Nevertheless, increases of forest density lead to a higher amount of possible territories, positively affecting the persistence of the species. The SEPVM developed for the current thesis allowed the reconciliation of a structural analysis of the landscape to dynamical population modeling, what is considered as a top priority research subject in landscape ecology.

APA, Harvard, Vancouver, ISO, and other styles

20

Blaauw, Maarten Ake. "An investigation of holocene sun-climate relationships using numerical 14C wiggle-match dating of peat deposits." Amsterdam : Amsterdam : IBED, Universiteit van Amsterdam ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/67138.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Roggensack, Arne [Verfasser], and Ingenuin [Akademischer Betreuer] Gasser. "Low Mach number equations with a heat source on networks : Modelling and analysis / Arne Roggensack. Betreuer: Ingenuin Gasser." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1059237873/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Kostet, Daniel. "Railway bridges with floating slab track systems : Numerical modelling of rail stresses - Dependence on properties of floating slab mats." Thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67297.

Full text

Abstract:

The increased use of continuously welded rails in the railway systems makes it necessary to increase the control of the rail stresses to avoid instability and damages of the rails. Large stresses are especially prone to appear at discontinuities in the railway systems, such as bridges, due to the interaction between the track and the bridge. The interaction leads to increased horizontal forces in the rails due to the changed stiffness between the embankment and the bridge, temperature variations, bending of the bridge structure because of vertical traffic loads and braking and traction forces. If the compressive rail stresses become too high it is necessary to use costly and maintenance-requiring devices such as rail expansion joints and other rail expansion devices. These devices increase the railway systems life cycle cost and should if possible be avoided. The use of non-ballasted track on high-speed railways, tramways and subways, has increased since this kind of track requires less maintenance and according to some investigations have a lower life cycle cost compared to ballasted track. The non-ballasted track is usually made of a track slab to which the rails are connected through fastenings. The track slab is connected to the bridge structure and held in place by shear keys. When non-ballasted tracks are used in populated areas it is sometimes necessary to introduce some vibration and noise damping solution. One of the possible solutions is to introduce a floating slab mat (elastic mat) under the track slab on the bridge. The influence of the floating slab mats properties on the rail stresses is investigated in this degree project. The investigation was performed through a numerical modelling of two railway bridges using the finite element software SOFiSTiK. The results from the investigation showed that there was a small reduction of the compressive rail stresses by approximately 3 – 7% (depending on the stiffness of the elastic support, load positions and the properties of the mat) when a mat was installed under the track slab. The results from the investigation also showed that there was a small reduction (up to approximately 1 %) of the compressive stresses in the rail when the thickness of the mat was increased, and the stiffness of the mat was reduced. This reduction of the compressive stresses is assumed to be caused by the mat being mounted on the sides of the shear keys. The lower stiffness of the mat allows the track slab and the bridge deck to move more freely parallel to each other in the horizontal direction. This leads to a decrease of the stresses in the rail due to a lower interaction between the track and the bridge. It was also shown that the rail stresses increased if the friction between the slab mat and the bridge deck was considered. This is because of an increase of the interaction between the track and the bridge due to the mats horizontal stiffness.
Den ökade användningen av kontinuerligt svetsade räler i järnvägsnäten i världen leder till en ökad kontroll av rälsspänningarna för att undvika instabilitet och skador på rälsen. Särskilt vid en diskontinuit i järnvägssystemet, som vid broar, kan stora tillskottspänningar i rälsen uppstå till följd av interaktionen mellan spår och bro. Interaktion leder till ökade horisontella krafter som verkar på rälsen och beror på den förändrade styvheten mellan järnvägsbank och bro, temperaturvariationer, nedböjning av bron på grund av vertikala trafiklaster samt broms- och accelerationskrafter. Om spänningarna i rälsen blir för stora behöver kostsamma och underhållskrävande dilatationsfogar införas. Dessa dilatationsfogar ökar järnvägssystemets livscykelkostnad och är något som ska undvikas att införas i den mån det är möjligt. Användningen av ballastfritt spår för höghastighetsjärnvägar, spårvägar och tunnelbanor ökar på grund av att dessa spår kräver mindre underhåll och har enligt vissa undersökningar en lägre livscykelkostnad i jämförelse med ballasterat spår. Ballastfritt spår består oftast av en betongplatta till vilken rälsen är kopplad genom befästningar. Plattan är i sin tur kopplad till underbyggnaden genom skjuvförbindare som håller plattan på plats. När ballastfritt spår används i bebodda områden är det ibland nödvändigt att ta till vibrations- och ljuddämpande åtgärder. En åtgärd som används på brokonstruktioner för att minska vibrationer och ljudföroreningar är att montera en vibrationsdämpande matta, som är tillverkad av ett elastiskt material, mellan betongplattan och broöverbyggnaden. I detta examensarbetet undersöks hur den vibrationsdämpande mattans egenskaper påverkar rälsspänningarna. Resultaten från undersökningen visar att spänningarna i rälsen minskar med cirka 3–7 % (beroende på det elastiska stödets styvhet, lastpositioner och mattans egenskaper) när en elastisk matta installeras under spårplattan i jämförelse med när ingen matta används. När mattans tjocklek ökar och när styvheten sänks minskar spänningarna med cirka 1 % i jämförelse mellan den tjockaste och tunnaste mattan. Denna minskning av spänningarna antas bero på att den vibrationsdämpande mattan som är monterad på sidan av skjuvförbindarna ger en möjlighet för spåret och bron att förskjutas fritt parallellt varandra innan en interaktion mellan spår och bro uppstår. Det visade sig även att om friktionen mellan mattan och broöverbyggnaden medräknas ökar spänningarna i rälsen. Detta beror på att mattan då skapar en större interaktion mellan spåret och bron gentemot fallet då mattans horisontella styvhet inte beaktas.

APA, Harvard, Vancouver, ISO, and other styles

23

Grandi, Diego <1975&gt. "Modelli Matematici per Transizioni di Fase in Materiali Speciali." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1960/.

Full text

Abstract:

In questa Tesi vengono trattati alcuni temi relativi alla modellizzazione matematica delle Transizioni di Fase, il cui filo conduttore è la descrizione basata su un parametro d'ordine, originato dalla Teoria di Landau. Dopo aver presentato in maniera generale un modo di approccio alla dinamica delle transizioni mediante campo di fase, con particolare attenzione al problema della consistenza termodinamica nelle situazioni non isoterme, si considerano tre applicazioni di tale metodo a transizioni di fase specifiche: la transizione ferromagnetica, la transizione superconduttrice e la transizione martensitica nelle leghe a memoria di forma (SMA). Il contributo maggiore viene fornito nello studio di quest'ultima transizione di fase per la quale si è elaborato un modello a campo di fase termodinamicamente consistente, atto a descriverne le proprietà termomeccaniche essenziali.

APA, Harvard, Vancouver, ISO, and other styles

24

Ould, Aly Sidi Mohamed. "Modélisation de la courbe de variance et modèles à volatilité stochastique." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00604530.

Full text

Abstract:

La première partie de cette thèse est consacrée aux problématiques liées à la modélisation markovienne de la courbe de variance forward. Elle est divisée en 3 chapitres. Dans le premier chapitre, nous présentons le cadre général de la modélisation de type HJM-Markov pour la courbe de variance forward. Nous revisitons le cadre affine-markovien modélisation et nous l'illustrons par l'exemple du modèle de Bühler. Dans le deuxième chapitre, nous proposons un nouveau modèle pour la courbe de variance forward qui combine les caractéristiques des deux versions (continue et discrète) du modèle de Bergomi 2008, sans se réduire ni à l'une ni à l'autre. Un des avantages de ce modèle est que les prix des futures et options sur VIX peuvent être exprimés comme des espérances de fonctions déterministes d'une variable aléatoire gaussienne, ce qui réduit le problème de la calibration à l'inversion de certaines fonctions monotones. Dans le troisième chapitre, on propose une méthode d'approximation pour les prix d'options européennes dans des modèles à volatilité stochastique de type multi-factoriels lognormal (comprenant le modèle présenté dans le deuxième chapitre, les modèles de Bergomi et le modèle de Scot 1987). Nous obtenons un développement d'ordre 3 de la densité du sous-jacent par rapport au paramètre de la volatilité de la volatilité. Nous présentons aussi une méthode de réduction de variance de type "variable de contrôle" pour la simulation par la méthode de Monte-Carlo qui utilise l'approximation explicite que nous obtenons de la fonction de répartition de la loi du sous-jacent. La deuxième partie de cette thèse est consacrée à l'étude des propriétés de monotonie des prix d'options européennes par rapport aux paramètres du CIR dans le modèle de Heston. Elle est divisée en deux chapitres. Dans le premier chapitre (cf. chapitre 4), nous donnons quelques résultats généraux sur le processus CIR. Nous montrons d'abord que les queues de distribution d'une combinaison du CIR et de sa moyenne arithmétique se comportent comme des exponentielles. Nous étudions ensuite les dérivées de la solution de ce processus par rapport aux paramètres de sa dynamique. Ces dérivées sont données comme solutions d'équations différentielles stochastiques, qu'on résout pour obtenir des représentations de ces dérivées en fonction des trajectoires du CIR. Le chapitre 5 est consacré à l'étude de la monotonie du prix d'un Put européen par rapport aux paramètres du CIR et à la corrélation dans le modèle de Heston. Nous montrons que, sous certaines conditions, les prix d'options européennes sont monotones par rapport aux paramètres du drift du CIR. Nous montrons ensuite que le paramètre de la volatilité de la volatilité joue le rôle de la volatilité si on prend la variance réalisée comme sous-jacent. En particulier, les prix d'options convexes sur la variance réalisée sont strictement croissants par rapport à la volatilité de la volatilité. Enfin, nous étudions la monotonie du prix du Put européen par rapport à la corrélation. Nous montrons que le prix du put du Put est croissant par rapport à la corrélation pour les petites valeurs du Spot et décroissant pour les grandes valeurs. Nous étudions ensuite les points de changement de monotonie pour les courtes et longues maturités

APA, Harvard, Vancouver, ISO, and other styles

25

Cheng, Bin. "On the modelling of sea ice thermodynamics and air-ice coupling in the Bohai Sea and the Baltic Sea." Helsinki : Finnish Institute of Marine Research, 2002. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/cheng/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Ribeiro, Tiago da Silva. "Filogeografia de Chiroxiphia caudata (Pipridae, Aves) e de Hemitriccus diops (Rynchocyclidae, Aves): estrutura populacional e história demográfica de passeriformes da Mata Atlântica." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/41/41131/tde-16042014-144631/.

Full text

Abstract:

Estudos filogeográficos almejam compreender a distribuição da diversidade genética de uma espécie. E ainda, estudos de organismos co-distribuídos permitem inferir os processos atuantes na história da região de sua ocorrência. Dentro desse contexto o presente trabalho se propôs a estudar a filogeografia de duas espécies de passeriformes endêmicos da Mata Atlântica, Chiroxiphia caudata e Hemitrccus diops, visando auxiliar na compreensão da evolução da biota neste bioma. Foram utilizados indivíduos amostrados ao longo da distribuição das espécies: 112 de C. caudata e 82 de H. diops. Foram obtidas sequências parciais do gene mitocondrial ND2 (932 pb e 910 pb, respectivamente para C. caudata e H. diops), de um íntron do gene G3PDH (303 pb e 323 pb, respectivamente), e de íntrons do gene ODC (517 pb) para H. diops. Não foi encontrada estrutura filogeográfica em C. caudata, que apresentou sinal de expansão recente. A ausência de estrutura pode ser decorrência do longo tempo de geração da espécie. Modelos de distribuição da espécie durante o último máximo glacial apresentaram dois cenários divergentes, um com distribuição predominantemente ao norte e outro com distribuição similar ou maior que a atual. Em contraste, foi encontrada uma baixa, mas clara estrutura filogeográfica em H. diops. Os sinais de alteração demográfica, entretanto, são menos claros, havendo tanto sinal de expansão quanto de estabilidade populacional ao longo dos ciclos glaciais. A diversidade de padrões filogeográficos encontrada na presente Dissertação é congruente com achados sobre a distribuição da diversidade genética de outros organismos da Mata Atlântica, e ultimamente, refletem a complexidade do bioma como um todo
Phylogeographic studies aim to analyze the distribution of the genetic diversity of a given species. In addition, studies of co-distributed organisms enable to infer historic processes acting on the region where they occur. In this context the present work intended to study the phylogeography of two Atlantic Forest endemic birds, Chiroxiphia caudata and Hemitriccus diops to help to understand how this biome evolved. 112 individuals of C. caudata and 82 of H. diops were sampled throughout their distributions. We obtained partial sequences of the mitochondrial gene ND2 (932 bp and 910 bp, respectively, for C. caudata and H. diops), of an intron of the G3PDH gene (303 bp and 323 bp, respectively), and introns from the ODC gene (517 bp) of H. diops. No signal of phylogeographic structure was found for C. caudata,, which exhibits signal of recent demographic expansion. The absence of population structure may be a consequence of the species long generation time. Models of distribution during the last glacial maximum exhibited two discordant scenarios: one with its main distribution in the north and another with a similar or larger distribution than the current one. In contrast, we found a shallow, but clear phylogeographic structure for H. diops. The demographic history, however, was not clear, with signal of both demographic expansion and stability during the glacial cycles. The different phylogeographic patterns found here are congruent with the diversity of patterns observed in other Atlantic Forest organisms, reflecting the complex history of the biome

APA, Harvard, Vancouver, ISO, and other styles

27

Hugues, Florian. "Modelling the vibrations generated by turbulent flows in ducts." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2470/document.

Full text

Abstract:

La prédiction des vibrations induites par un écoulement est essentielle dans la conception des conduits de nombreuses installations industrielles, en particulier dans l’industrie du gaz. Notre étude concerne la prévision du bruit et la vibration des conduits soumis à un écoulement turbulent à faible nombre de Mach. Notre objectif est de présenter une étude numérique et expérimentale permettant aux ingénieurs de mieux comprendre le couplage entre l’excitation aléatoire et le conduit pour deux géométries (circulaire ou rectangulaire). Une approche expérimentale est développée et utilisée pour valider les prévisions numériques. Deux cas sont étudiés : (i) un conduit droit sans singularité, où les modes acoustiques du conduit sont excités par une couche limite turbulente (TBL) et (ii) un conduit droit avec un diaphragme inséré en amont qui génère une source acoustique localisée. La contribution acoustique est déterminée soit par des méthodes de mesure d’interspectres, soit à l’aide des outils de mécanique des fluides numérique (CFD) et d’analogies aéroacoustiques. La réponse de la structure est estimée par une approche dite de « couplage faible » qui utilise des fonctions de transfert modale d’un conduit fini simplement appuyé. Les mesures conduiront à évaluer et suggérer des améliorations de modèles empiriques existants de densité interspectrale de puissance (CPSD) dans un contexte d’écoulements internes turbulents. Une analyse modale expérimentale d’un conduit rectangulaire finie est confrontée à des méthodes de calcul pour évaluer l’effet des conditions aux limites, du rayonnement acoustique et de l’amortissement aérodynamique. Le couplage fluide structure est analysé par la fonction de « joint acceptance » à la fois dans le domaine spatial et dans le domaine des nombres d’onde. L’excitation comprend à la fois les contributions acoustiques et hydrodynamiques à l’aide des CPSD exprimées sur la base des fonctions de cohérence de type Corcos, champ diffus et modes acoustiques d’ordre élevé. Enfin, les études numériques et expérimentales de cette thèse ont été utilisées pour développer un cadre d’étude et de modélisation du bruit et des vibrations dans les conduites, qui relie la dynamique des fluides, les modèles analytiques et empiriques à des techniques efficaces d’analyse aléatoire
Pipeline and duct vibrations can cause a range of issues from unplanned shutdownsto decreased equipment life time. Thus, the prediction of flow-induced vibrations is essential in piping design in many industrial plants, especially, for Gas industry. This study deals with the prediction of pipe flow noise and vibration at low Mach number. We aim to present a numerical and experimental study which can offer engineers a better understanding of the coupling between random excitation and duct section for two geometries (circular or rectangular). An experimental facility and measurement approach is developed and used to validate numerical predictions. Two cases are investigated: (i) a straight duct with no singularity, duct acoustic modes are excited by the Turbulent Boundary Layer (TBL) and (ii) a straight duct with a diaphragm inserted upstream generating a localized acoustic source. The acoustic contribution is either measured via cross-spectra based methods or calculated using Computational Fluid Dynamics (CFD) and aeroacoustic analogies. The response of the structure is estimated via a ‘blocked’ approach using analytical modal Frequency Response Functions (FRFs) of a simply supported finite duct. Measurements will lead to evaluate and suggest improvements to existing Cross Power Spectral Density (CPSD) empirical models in a context of internal turbulent flows. Experimental modalanalysis of a finite rectangular duct are confronted to computational methods to assess the effect of the Boundary Conditions (BCs), the resistive damping from coupling with the internal acoustic medium and aerodynamic damping. The fluid-structure coupling is analyzed through the joint acceptance function both in the spatial and wave number domain. The excitation includes both the acoustic and hydrodynamic contributions using CPSD written on the basis of Corcos, Diffuse Acoustic Field (DAF) and acoustic duct mode coherence functions. Finally, the numerical and experimental studies in this thesis were used to develop a framework for studying and modelling pipe flow noise and vibration which links CFD, analytical and empirical models to efficient random analysis techniques

APA, Harvard, Vancouver, ISO, and other styles

28

Wang, Chen. "Large-scale 3D environmental modelling and visualisation for flood hazard warning." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/3350.

Full text

Abstract:

3D environment reconstruction has received great interest in recent years in areas such as city planning, virtual tourism and flood hazard warning. With the rapid development of computer technologies, it has become possible and necessary to develop new methodologies and techniques for real time simulation for virtual environments applications. This thesis proposes a novel dynamic simulation scheme for flood hazard warning. The work consists of three main parts: digital terrain modelling; 3D environmental reconstruction and system development; flood simulation models. The digital terrain model is constructed using real world measurement data of GIS, in terms of digital elevation data and satellite image data. An NTSP algorithm is proposed for very large data assessing, terrain modelling and visualisation. A pyramidal data arrangement structure is used for dealing with the requirements of terrain details with different resolutions. The 3D environmental reconstruction system is made up of environmental image segmentation for object identification, a new shape match method and an intelligent reconstruction system. The active contours-based multi-resolution vector-valued framework and the multi-seed region growing method are both used for extracting necessary objects from images. The shape match method is used with a template in the spatial domain for a 3D detailed small scale urban environment reconstruction. The intelligent reconstruction system is designed to recreate the whole model based on specific features of objects for large scale environment reconstruction. This study then proposes a new flood simulation scheme which is an important application of the 3D environmental reconstruction system. Two new flooding models have been developed. The first one is flood spreading model which is useful for large scale flood simulation. It consists of flooding image spatial segmentation, a water level calculation process, a standard gradient descent method for energy minimization, a flood region search and a merge process. The finite volume hydrodynamic model is built from shallow water equations which is useful for urban area flood simulation. The proposed 3D urban environment reconstruction system was tested on our simulation platform. The experiment results indicate that this method is capable of dealing with complicated and high resolution region reconstruction which is useful for many applications. When testing the 3D flood simulation system, the simulation results are very close to the real flood situation, and this method has faster speed and greater accuracy of simulating the inundation area in comparison to the conventional flood simulation models

APA, Harvard, Vancouver, ISO, and other styles

29

Schulz, Paul Christopher. "The value base of water governance in the Upper Paraguay River basin, Mato Grosso, Brazil." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29548.

Full text

Abstract:

Values have been identified as important factors that guide decision-making and influence preferences in water governance. Comparing the values reflected in water governance decisions with the values held by stakeholders and the general public may inform the debate on the political legitimacy of water governance. The research presented in this PhD thesis draws on multiple research traditions on values, ranging from ecological economics and political ecology to social and environmental psychology, to investigate the value base of water governance in the Upper Paraguay River Basin, in the state of Mato Grosso, Brazil. It first introduces a novel conceptual framework that integrates these various research traditions and suggests that water governance is closely related to the fundamental values, governance-related values, and assigned values of stakeholders and actors in water governance more generally. These different types of values vary in their level of abstractness, as well as in their ‘locus’, i.e. where the valuing person locates them, and are hypothesised to be closely interrelated in a hierarchical structure, with fundamental values being the most abstract type of values. Water governance, in turn, is defined as the synthesis of water policy (the ‘content’ of decisionmaking), water politics (the ‘power play’ between actors) and water polity (the institutional framework). The thesis then proceeds to apply this novel conceptual framework in a case study on stakeholders’ values in the Upper Paraguay River Basin, and investigates the relationship of their values with their preferences regarding the construction of the Paraguay-Paraná Waterway through the Pantanal wetland, in the south of Mato Grosso. This water infrastructure project has a long history of conflict attached to it, as it might impact the hydrology and ecology of the Pantanal, the world’s largest tropical freshwater wetland and UNESCO biosphere reserve, while at the same time benefitting Mato Grosso’s rapidly growing agribusiness sector by lowering the cost of soybean exports. Based on 24 semi-structured interviews with relevant stakeholders, it was found that supporters and opponents possess different, clashing ‘value landscapes’ (i.e. groups of related values), which may explain the protracted nature of the conflict around the construction of the waterway, while at the same time highlighting political legitimacy deficits of the project. This research was followed up by a quantitative study with members of the general public (n=1067), which sought to measure and test the assumption that we can empirically identify such clashing value landscapes, and their relationship with preferences for or against the Paraguay-Paraná Waterway. Using structural equation modelling (SEM), statistically significant links between people’s values and their preferences in water governance could indeed be found, as well as between different types of values, which formed two contrasting value landscapes. This suggests that water governance conflicts may in part be explained by the presence of different value landscapes among involved actors, which may include even the most abstract level of fundamental values. The research presented in this thesis thus contributes to interdisciplinary debates on the role of values for water governance from multiple conceptual, as well as methodological perspectives. Additionally, through its application to a concrete case study, it highlights the policy relevance of such research, as addressing conflicts in water governance and examining alternative policy options may require a more explicit consideration of the values of the actors involved.

APA, Harvard, Vancouver, ISO, and other styles

30

Zemzemi, Nejib. "Étude théorique et numérique de l'activité électrique du cœur: Applications aux électrocardiogrammes." Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00470375.

Full text

Abstract:

La modélisation du vivant, en particulier la modélisation de l'activité cardiaque, est devenue un déﬁ scientiﬁque majeur. Le but de cette thématique est de mieux comprendre les phénomènes physiologiques et donc d'apporter des solutions à des problèmes cliniques. Nous nous intéressons dans cette thèse à la modélisation et à l'étude numérique de l'activité électrique du cœur, en particulier l'étude des électrocardiogrammes (ECGs). L'onde électrique dans le cœur est gouvernée par un système d'équations de réaction-diﬀusion appelé modèle bidomaine ce système est couplé à une EDO représentant l'activité cellulaire. Aﬁn simuler des ECGs, nous tenons en compte la propagation de l'onde électrique dans le thorax qui est décrite par une équation de diﬀusion. Nous commençons par une démonstrer l'existence d'une solution faible du système couplé cœur-thorax pour une classe de modèles ioniques phénoménologiques. Nous prouvons ensuite l'unicité de cette solution sous certaines conditions. Le plus grand apport de cette thèse est l'étude et la simulation numérique du couplage électrique cœur-thorax. Les résultats de simulations sont représentés à l'aide des ECGs. Dans une première partie, nous produisons des simulations pour un cas normal et pour des cas pathologiques (blocs de branche gauche et droit et des arhythmies). Nous étudions également l'impact de certaines hypothèses de modélisation sur les ECGs (couplage faible, utilisation du modèle monodomaine, isotropie, homogénéité cellulaire, comportement résistance-condensateur du péricarde,. . . ). Nous étudions à la ﬁn de cette partie la sensibilité des ECGs par apport aux paramètres du modèle. En deuxième partie, nous eﬀectuons l'analyse numérique de schémas du premier ordre en temps découplant les calculs du potentiel d'action et du potentiel extérieur. Puis, nous combinons ces schémas en temps avec un traîtement explicite du type Robin-Robin des conditions de couplage entre le cœur et le thorax. Nous proposons une analyse de stabilité de ces schémas et nous illustrons les résultats avec des simulations numériques d'ECGs. La dernière partie est consacrée à trois applications. Nous commençons par l'estimation de certains paramètres du modèle (conductivité du thorax et paramètres ioniques). Dans la deuxième application, qui est d'originie industrielle, nous utilisons des méthodes d'apprentissage statistique pour reconstruire des ECGs à partir de mesures ('électrogrammes). Enﬁn, nous présentons des simulations électro-mécaniques du coeur sur une géométrie réelle dans diverses situations physiologiques et pathologiques. Les indicateurs cliniques, électriques et mécaniques, calculés à partir de ces simulations sont très similaires à ceux observés en réalité.

APA, Harvard, Vancouver, ISO, and other styles

31

Ranzini, Maurício. "Modelagem hidrológica de uma microbacia florestada da Serra do Mar, SP, com o modelo TOPMODEL : simulação do comportamento hidrológico em função do corte raso." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-29092015-090451/.

Full text

Abstract:

Utilizou-se o modelo hidrológico TOPMODEL, baseado em aspectos físicos e topográficos, em uma das três microbacias do Laboratório de Hidrologia Florestal Eng. Agr. Walter Emmerich, do Instituto Florestal/SP. O laboratório localiza-se na Serra do Mar, junto às cabeceiras do rio Paraibuna, um dos formadores do rio Paraíba do Sul. O modelo usa um índice topográfico que indica as áreas de contribuição para o deflúvio da microbacia e permite simular a vazão e analisar o comportamento hidrológico da microbacia. A primeira parte do trabalho buscou determinar os valores iniciais dos parâmetros de calibração, testar a validade das premissas do modelo, e, principalmente, compreender melhor o funcionamento hidrológico da bacia D. Os resultados indicam uma eficiência maior para as simulações de eventos isolados do que para as de períodos longos. A simulação do comportamento hidrológico em função do corte raso mostrou uma diminuição do tempo de pico e um aumento significativo do volume de vazão simulado: de 17 a 44%, em comparação a bacia D coberta com floresta. Mostram, também, que de 7 a 93% do deflúvio é gerado a partir das áreas variáveis de afluência (A.V.A.). Recomenda-se que o corte raso seja evitado a qualquer custo. Caso seja necessário, as matas ciliares devem ser mantidas; onde elas não existem mais, devem ser recuperadas imediatamente. As áreas com agricultura ou pastagem devem utilizar as melhores técnicas de conservação do solo, de forma que as condições naturais de infiltração não sejam drasticamente alteradas.
A physically based semi-distributed model, TOPMODEL, has been applied to one catchment in Cunha, São Paulo, Brazil. The model uses a topographic index which highlights significant hydrological areas within the catchment. The model simulate streamflow and analyse the behaviour of the catchment. The first part of this paper concerns to the first values of calibration parameters, experiments the validity of the premisses of the model, and, mainly, tries to understand how does the hydrology of D catchment works. The results are more efficient on simulation of isolate events than on events of long period. The simulation of hydrology behaviour subject to clear-cutting has showed a diminution of the time of rise and a significant increase of streamflow simulated: from 17 to 44%, in comparaison to D forest catchment. They also show that from 7 to 93% of the streamflow is generated from saturated contributing areas (sources areas). It\'s advisable to avoid clear-cutting. If necessary, the riparian zone has to be preserved; and where they have been destroyed, they have to be recovered urgently. Agricultural lands or grasslands have to use the best management practices, in order to keep the natural conditions of infiltration.

APA, Harvard, Vancouver, ISO, and other styles

32

Mura, Antonio <1978&gt. "Non-Markovian stochastic processes and their applications: from anomalous diffusion to time series analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/846/.

Full text

Abstract:

This work provides a forward step in the study and comprehension of the relationships between stochastic processes and a certain class of integral-partial differential equation, which can be used in order to model anomalous diffusion and transport in statistical physics. In the first part, we brought the reader through the fundamental notions of probability and stochastic processes, stochastic integration and stochastic differential equations as well. In particular, within the study of H-sssi processes, we focused on fractional Brownian motion (fBm) and its discrete-time increment process, the fractional Gaussian noise (fGn), which provide examples of non-Markovian Gaussian processes. The fGn, together with stationary FARIMA processes, is widely used in the modeling and estimation of long-memory, or long-range dependence (LRD). Time series manifesting long-range dependence, are often observed in nature especially in physics, meteorology, climatology, but also in hydrology, geophysics, economy and many others. We deepely studied LRD, giving many real data examples, providing statistical analysis and introducing parametric methods of estimation. Then, we introduced the theory of fractional integrals and derivatives, which indeed turns out to be very appropriate for studying and modeling systems with long-memory properties. After having introduced the basics concepts, we provided many examples and applications. For instance, we investigated the relaxation equation with distributed order time-fractional derivatives, which describes models characterized by a strong memory component and can be used to model relaxation in complex systems, which deviates from the classical exponential Debye pattern. Then, we focused in the study of generalizations of the standard diffusion equation, by passing through the preliminary study of the fractional forward drift equation. Such generalizations have been obtained by using fractional integrals and derivatives of distributed orders. In order to find a connection between the anomalous diffusion described by these equations and the long-range dependence, we introduced and studied the generalized grey Brownian motion (ggBm), which is actually a parametric class of H-sssi processes, which have indeed marginal probability density function evolving in time according to a partial integro-differential equation of fractional type. The ggBm is of course Non-Markovian. All around the work, we have remarked many times that, starting from a master equation of a probability density function f(x,t), it is always possible to define an equivalence class of stochastic processes with the same marginal density function f(x,t). All these processes provide suitable stochastic models for the starting equation. Studying the ggBm, we just focused on a subclass made up of processes with stationary increments. The ggBm has been defined canonically in the so called grey noise space. However, we have been able to provide a characterization notwithstanding the underline probability space. We also pointed out that that the generalized grey Brownian motion is a direct generalization of a Gaussian process and in particular it generalizes Brownain motion and fractional Brownain motion as well. Finally, we introduced and analyzed a more general class of diffusion type equations related to certain non-Markovian stochastic processes. We started from the forward drift equation, which have been made non-local in time by the introduction of a suitable chosen memory kernel K(t). The resulting non-Markovian equation has been interpreted in a natural way as the evolution equation of the marginal density function of a random time process l(t). We then consider the subordinated process Y(t)=X(l(t)) where X(t) is a Markovian diffusion. The corresponding time-evolution of the marginal density function of Y(t) is governed by a non-Markovian Fokker-Planck equation which involves the same memory kernel K(t). We developed several applications and derived the exact solutions. Moreover, we considered different stochastic models for the given equations, providing path simulations.

APA, Harvard, Vancouver, ISO, and other styles

33

Zanlungo, Francesco <1976&gt. "Microscopic dynamics of artificial life systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/355/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Gould, Geoffrey Michael. "Signaling and Communication in the Breeding Behavior of the Lesser Prairie-Chicken (Tympanuchus pallidicinctus)." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595442814242732.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Johari, Shirazi Iman. "Combining Business Intelligence, Indicators, and the User Requirements Notation for Performance Monitoring." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23540.

Full text

Abstract:

Organizations use Business Intelligence (BI) systems to monitor how well they are meeting their goals and objectives. Yet, very often BI systems do not include clear models of the organization’s goals or of how to measure whether they are satisfied or not. Several researchers now attempt to integrate goal models into BI systems, but there are still major challenges related to how to get access to the BI data to populate the part of the goal model (often indicators) used to assess goal satisfaction. This thesis explores a new approach to integrate BI systems with goal models. In particular, it explores the integration of IBM Cognos Business Intelligence, a leading BI tool, with an Eclipse-based goal modeling tool named jUCMNav. jUCMNav is an open source graphical editor for the User Requirements Notation (URN), which includes the Use Case Map notation for scenarios and processes and the Goal-oriented Requirement Language for business objectives. URN was recently extended with the concept of Key Performance Indicator (KPI) to enable performance assessment and monitoring of business processes. In jUCMNav, KPIs are currently calculated or modified manually. The new integration proposed in this thesis maps these KPIs to report elements that are generated automatically by Cognos based on the model defined in jUCMNav at runtime, with minimum effort. We are using IBM Cognos Mashup Service, which includes web services that enable the retrieval of report elements at the most granular level. This transformation provides managers and analysts with useful goal-oriented and process-oriented monitoring views fed by just-in-time BI information. This new solution also automates retrieving data from Cognos servers, which helps reducing the high costs usually caused by the amount of manual work required otherwise. The novel approach presented in this thesis avoids manual report generation and minimizes any contract with respect to the location of manually created reports, hence leading to better usability and performance. The approach and its tool support are illustrated with an ongoing example, validated with a case study, and verified through testing.

APA, Harvard, Vancouver, ISO, and other styles

36

Rietz, Andreas. "Numerisk modell för global transport av spårämnen i atmosfären." Thesis, Linköping University, Department of Mechanical Engineering, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2931.

Full text

Abstract:

The aim of this project was to develop a numerical model simulating the global transport of air pollution. The model currently used by SMHI, the Swedish Meteorological and Hydrological Institute, was intended to perform such simulations at regional scales. However, the usage of a grid based on longitudes and latitudes makes this model work poorly in global simulations. The problem with this grid is that the nodes are concentrated near the North and South Poles. Due to this characteristic, the Courant, Friedrich and Lewy-condition for numerical stability puts a sharp bound on the timestep length. In order to keep the transport algorithms stable, the timestep length has to be very small.

To avoid too short timesteps, we adopted a new kind of grid. In principle, we defined the global grid on the surface of a cube. By replacing straight lines on the cube with great circles we took the curvature of the Earth into account. The result was almost equal distances between the nodes, and thus we were able to use an acceptable timestep length.

Målet med detta examensarbete var att utveckla en datormodell för global transportsimulering av luftföroreningar. Den modell som hittills använts av SMHI, Sveriges meterologiska och hydrologiska institut, utvecklades för att göra transportsimuleringar över begränsade områden. Detta innebar att ett gitter baserat på latituder och longituder kunde utnyttjas. Problemet som uppkommer då detta gitter används i globala simuleringar är att noderna ligger alltför tätt i närheten av polerna. Enligt CFL-villkoret för numerisk stabilitet så kommer då de numeriska algoritmer som simulerar vindtransport att bli instabila i polarområdena om inte tidssteglängden görs mycket liten.

För att undvika en alltför kort tidssteglängd så har vi i detta projekt begagnat oss av ett nytt slags gitter. Grundideen bakom det nya gittret var att utgå från en numerisk metod definierad på en kub. För att tillämpa metoden på en sfär så ersatte vi kubens räta linjer med storcirklar till sfären. Resultatet blev en någorlunda jämn geografisk spridning av beräkningsnoderna, vilket innebar att en godtagbar tidssteglängd kunde användas.

APA, Harvard, Vancouver, ISO, and other styles

37

Soares, Patricia Lima. "The reunion of two lineages of the Neotropical brown stinkbug in soybean lands in the heart of Brazil." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11146/tde-13032018-154536/.

Full text

Abstract:

The rapid pace of conversion of natural areas to agronomic systems is a matter of great concern, and the consequences for conservation and pest management are not yet fully understood. We examined mitochondrial (COI and Cytb) and nuclear (ITS1) gene regions of 21 Euschistus heros populations to investigate the genetic diversity, genetic structure, and the demographic history of this emerging pest of soybean crops in South America. Two deep divergent lineages that separated in the Pliocene (4.5 My) have been found over a wide area. The northern lineage is older, more diverse, and prevalent in the Amazon and Caatinga, while the southern lineage is younger, less diverse, and prevalent in the Atlantic Forest and Chaco biomes. The secondary contact is occurring mainly in the Cerrado, an important agriculture frontier. Euschistus heros populations are expanding in size and range, but are strongly affected by environment variables. Historical changes during the Plio-Pleistocene created significant genetic differentiation between E. heros populations, which differentiated further in several biomes. The present populations are expanding at different rates, mixing highly diverse populations with less-diverse populations in regions of intensive farming. This, individuals adapted to different environmental conditions and to large monocultures might currently be combining into a panmictic and hard-to-control pest population.
O ritmo acelerado da conversão de áreas naturais em sistemas agronômicos é motivo de grande preocupação e as consequências para conservação e manejo de pragas ainda não são totalmente compreendidas. Examinamos regiões de genes mitocondriais (COI e Cytb) e nucleares (ITS1) de 21 populações de Euschistus heros para investigar a diversidade genética, a estrutura genética e a história demográfica dessa praga emergente de soja na América do Sul. Duas linhagens profundamente divergentes que se separaram no Plioceno (4.5 My) foram encontradas amplamente distribuidas na América do Sul. A linhagem norte é mais antiga, mais diversificada e predomina na Amazônia e Caatinga, enquanto a linhagem sul é mais jovem, menos diversificada e prevalente nos biomas da Mata Atlântica e Chaco. O contato secundário está ocorrendo principalmente no Cerrado, uma importante fronteira agrícola. As populações de E. heros estão se expandindo em tamanho e área, mas são fortemente afetadas pelas variáveis ambientais. As mudanças históricas durante o Plio-Pleistoceno criaram significativa diferenciação genética entre as populações de E. heros, que se encontram estruturadas nos biomas. As populações atuais estão se expandindo em diferentes taxas, misturando populações altamente diversas com populações menos diversas em regiões de agricultura intensiva. Assim, indivíduos adaptados a diferentes condições ambientais e grandes monoculturas podem combinar-se em uma população de pragas panmítica e difícil de controlar.

APA, Harvard, Vancouver, ISO, and other styles

38

Demeyer, Séverine. "Approche bayésienne de l'évaluation de l'incertitude de mesure : application aux comparaisons interlaboratoires." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2011. http://tel.archives-ouvertes.fr/tel-00585727.

Full text

Abstract:

La modélisation par équations structurelles est très répandue dans des domaines très variés et nous l'appliquons pour la première fois en métrologie dans le traitement de données de comparaisons interlaboratoires. Les modèles à équations structurelles à variables latentes sont des modèles multivariés utilisés pour modéliser des relations de causalité entre des variables observées (les données). Le modèle s'applique dans le cas où les données peuvent être regroupées dans des blocs disjoints où chaque bloc définit un concept modélisé par une variable latente. La structure de corrélation des variables observées est ainsi résumée dans la structure de corrélation des variables latentes. Nous proposons une approche bayésienne des modèles à équations structurelles centrée sur l'analyse de la matrice de corrélation des variables latentes. Nous appliquons une expansion paramétrique à la matrice de corrélation des variables latentes afin de surmonter l'indétermination de l'échelle des variables latentes et d'améliorer la convergence de l'algorithme de Gibbs utilisé. La puissance de l'approche structurelle nous permet de proposer une modélisation riche et flexible des biais de mesure qui vient enrichir le calcul de la valeur de consensus et de son incertitude associée dans un cadre entièrement bayésien. Sous certaines hypothèses l'approche permet de manière innovante de calculer les contributions des variables de biais au biais des laboratoires. Plus généralement nous proposons un cadre bayésien pour l'amélioration de la qualité des mesures. Nous illustrons et montrons l'intérêt d'une modélisation structurelle des biais de mesure sur des comparaisons interlaboratoires en environnement.

APA, Harvard, Vancouver, ISO, and other styles

39

Fiskaare, Jenny, and Pernilla Johansson. "Mat kring Vättern : Ett gemensamt varumärke, ett sätt att öka horisontellt värdeskapande?" Thesis, Linköpings universitet, Företagsekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-131054.

Full text

Abstract:

Bakgrund/problem: Då svensk matproduktion länge varit dominerad av massproduktion och förädlade livsmedel, pekar nu trenden mot att allt fler intresserar sig för lokalproducerad mat. Detta innebär en möjlighet för lokalproducenter att sälja och marknadsföra sina varor i en större omfattning jämfört med tidigare. För att detta skall realiseras visar forskning att det krävs samarbete aktörerna emellan för att maximera värdet. Dock är forskningen begränsad i att förklara hur dessa samarbeten bör utformas. Syfte: Syftet med studien är att undersöka om en brandingmöjlighet skulle kunna ge upphov till ett horisontellt värdeskapande och vilka dimensioner som i så fall skulle vara kritiska i en affärsmodell för att möjliggöra denna typ av värdeskapande. Metod: Vätterns nutida förutsättningar för framtida matsamarbeten har formats som en fallstudie där kvalitativt arbetssätt använts för att samla empiriskt material. Resultatet bygger på en kombination av långa och korta intervjuer där respondenter från tre olika infallsvinklar hörts. Dessa tre infallsvinklar; samordning, aktör och marknadsföring har valts för att kunna få en holistisk syn på den angivna problematiken. Resultat/Bidrag: Resultatet av studien påvisar att en identifierad brandingmöjlighet via identitetsbyggande faktorer kan bygga ett starkt varumärke, vilket kan ligga till grund för ett horisontellt värdeskapande. För att det horisontella värdeskapandet i slutändan ska möjliggöras kräver affärsmodellen fyra kritiska dimensioner (balans av aktörer, finansiell och mobiliserande kraft, tillfredsställande ledning samt nätverkande).
Background/problem: For a long time the food industry has been dominated by mass production and refined food, though times are changing and more people are getting interested in locally produced food. This enables great possibilities for local food producers, which give them great opportunities to sell and market their goods, but it requires them to cooperate with each other. The present research is rather limited on how to create these types of cooperation in the food industry. Purpose: The purpose of this research paper is to examine if a branding opportunity can enable horizontal value co-creation and which dimensions that will be critical in a business model in order to enable that type of value co-creation. Method: A case study has been formed based upon the present conditions of Vättern to enable a food based cooperation, where qualitative methods have been used to collect data. The result is based upon a combination of in-depth and shorter interviews where the respondents represent three approaches; coordinator, stakeholder and marketing. These approaches were chosen in order to enable a holistic perspective on the problem area. Results/contribution: The study shows that a branding opportunity can result in a strong brand, which can build a foundation for horizontal value co-creation. In order to enable horizontal value cocreation, the business model requires four critical dimensions, (operators in balance, financial- and mobilizing muscle, a satisfying management and lastly, networking), which are identified in this study.

APA, Harvard, Vancouver, ISO, and other styles

40

Etienne, Loic. "L'évolution du choix du partenaire par sélection sexuelle directe : une approche théorique." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20235.

Full text

Abstract:

Le choix du partenaire sexuel est un comportement très fréquent dans la nature et qui présente une grande variabilité. Notamment, le niveau de sélectivité lors du choix est très divers entre et au sein des espèces. Afin d'expliquer cette diversité, un certain nombre de modèles théoriques se sont focalisés sur les contraintes génétiques ou cognitives qui pouvaient influencer l'évolution du choix. Toutefois, les contraintes écologiques ont été sous-estimées par ces approches. En particulier, l'influence du compromis entre qualité des partenaires et taux d'appariement, bien qu'intrinsèquement lié au choix, a été largement ignorée. Des modèles analytiques et numériques sont présentés, dans lesquels le choix évolue uniquement sous l'influence de ce compromis, c'est- à-dire par sélection sexuelle directe. Il est montré qu'en fonction du contexte écologique, cette force évolutive peut produire une grande diversité de situations de choix, notamment en termes de sélectivité et condition-dépendance, tant chez les femelles que chez les mâles. L'émergence du choix mutuel, et plus généralement la coévolution entre choix femelle et choix mâle est discutée. Un prédicteur général de l'évolution du choix suite à une modification du taux d'appariement des individus est identifié. Il s'agit de la sensibilité du RST (relative searching time), c'est-à-dire la variation à sélectivité constante de la proportion du temps de vie consacrée à chercher des partenaires. Ce prédicteur englobe ceux proposés par les modèles précédents, s'applique à des situations de choix très variées et offre des perspectives empiriques intéressantes. Pris dans leur ensemble, ces résultats plaident pour une reconsidération de l'influence des contraintes écologiques sur l'évolution du choix du partenaire sexuel. Enfin, des perspectives sont proposées afin d'étudier cette influence dans des contextes variés de choix de partenaire et plus généralement de prise de décision
Mate choice is a widespread behaviour in nature and is highly variable. Notably, the level of choosiness when choosing ones mates is very diverse between and within species. In order to explain this diversity, numerous models have focused on the genetic and cognitive constraints that could influence the evolution of mate choice. However, ecological constraints have been underestimated by these approaches. In particular, the influence of the trade-off between mating benefits and mating rate, although it is intrinsically associated with mate choice, has been largely ignored. Analytical and numerical models are presented, in which choosiness evolved solely under the influence of this trade-off, that is, by direct sexual selection. It is shown that according to the ecological context, this selection pressure is able to generate a high diversity of choice situations, notably in terms of choosiness and condition dependence, for females as much as for males. The emergence of mutual mate choice, and more generally the coevolution between female and male choice is discussed. A general predictor of the evolution of choosiness following a change in the mating rate of individuals is identified. It is the sensitivity of the RST (relative searching time), that is, the variation of the amount of lifetime devoted searching for mates when choosiness remains constant. This predictor encompasses previously proposed ones, applies to many different situations of mate choice and offers interesting empirical perspectives.Overall, these results call for a reconsideration of the influence of ecological constraints on the evolution of mate choice. Finally, some perspectives are proposed in order to study this influence in various contexts of mate choice and more generally of decision-making

APA, Harvard, Vancouver, ISO, and other styles

41

Nyman, Frida. "Uppfattningar om hälsosam mat och attityder till Livsmedelsverkets kostråd hos unga kvinnor och män i åldern 18 till 30 år." Thesis, Uppsala universitet, Institutionen för folkhälso- och vårdvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385907.

Full text

Abstract:

Bakgrund: Enligt Världshälsoorganisationen (WHO) utgör ohälsosamma matvanor den största risken för ohälsa i Europa. Sveriges regering belyser även ohälsosamma matvanor som den största risken till för tidig död. Svenskarnas intag av hälsosam mat har visat sig vara bristfälligt. Den målgrupp som har sämst matvanor är unga vuxna kvinnor och män. Tidigare studier har även visat på att de kostråd Livsmedelsverket förmedlar inte alltid anses trovärdiga. Syfte: Syftet med denna studie var att undersöka uppfattningar om hälsosam mat och attityder till Livsmedelsverkets kostråd hos unga kvinnor och män i åldern 18 till 30 år. Metod: Denna studie genomfördes med en beskrivande kvalitativ metod med semistrukturerade intervjuer som datainsamlingsmetod. Urvalet skedde genom ett ändamålsenligt urval. Totalt rekryterades tio deltagare, sex kvinnor och fyra män. Samtliga deltagare medverkade frivilligt i studien. Den analysmetod som tillämpades var kvalitativ manifest innehållsanalys. Resultat: Resultatet visade på att samtliga deltagare ansåg frukt, bär och grönsaker som hälsosamt. Uppfattningar gällande vad som är hälsosam mat utöver detta överensstämde inte fullt ut med de kostråd Livsmedelsverket förmedlar, då olika åsikter om fett, mejeriprodukter, fisk och skaldjur samt rött kött och charkprodukter framkom. Attityden till en del av Livsmedelsverkets kostråd visade sig i denna studie vara negativ bland flera av deltagarna. Detta gällde främst råden angående fett, mejeriprodukter och proteinkällor. Slutsats: Att arbeta aktivt för att skapa en mer enhetlig bild av innebörden av hälsosam mat kan därför vara av vikt. Genom informationsförmedling från en och samma vetenskapligt grundad källa kan matvanorna hos befolkningen förbättras. Detta kan även medföra att en mer positiv attityd till de fullständiga kostråden ökar.
Background: According to the World Health Organization (WHO), unhealthy eating habits represent the primary cause of illness in Europe. The Swedish Government also highlights unhealthy eating habits as the primary cause of premature death. Swedes´ consumption of healthy food has further proved to be insufficient from a health perspective. Young women and men have generally the poorest eating habits. Previous studies have shown that the dietary recommendations provided by the National Food Agency are in addition not always considered credible. Purpose: The purpose of this study is to investigate perceptions of healthy food and attitudes towards the National Food Agency's dietary guidelines amongst women and men aged 18 to 30 years. Method: The study was conducted with a descriptive qualitative method with semi-structured interviews as data collection method. Selection was made through a targeted selection. In total, ten participants were recruited, six women and four men. They all participated on a voluntary basis. The analytical method applied was qualitative manifest content analysis. Results: All participants considered fruit, berries and vegetables to be healthy food. Perceptions of the participants regarding what constitutes healthy food in addition to this proved to be partly out of line with the recommendations of the National Food Agency. Different opinions about fat, dairy products, fish and shellfish as well as red meat and char products emerged. The attitude towards some of the National Food Agency's dietary guidelines turned out to be negative among several of the participants. This mainly concerned the advice on fat, dairy products and protein sources. Conclusion: Working actively to create a more unified and correct view of what constitutes healthy food is therefore important. By providing information from one and the same scientifically based source, knowledge and as a result eating habits of the population can be improved. This can also generate a more positive attitude towards the complete dietary guidelines.

APA, Harvard, Vancouver, ISO, and other styles

42

Dasappa, Prasad. "Constitutive Modelling of Creep in a Long Fiber Random Glass Mat Thermoplastic Composite." Thesis, 2008. http://hdl.handle.net/10012/4187.

Full text

Abstract:

Random Glass Mat Thermoplastic (GMT) composites are increasingly being used by the automotive industry for manufacturing semi-structural components. The polypropylene based materials are characterized by superior strength, impact resistance and toughness. Since polymers and their composites are inherently viscoelastic, i.e. their mechanical properties are dependent on time and temperature. They creep under constant mechanical loading and the creep rate is accelerated at elevated temperatures. In typical automotive operating conditions, the temperature of the polymer composite part can reach as high as 80°C. Currently, the only known report in the open literature on the creep response of commercially available GMT materials offers data for up to 24 MPa at room temperature. In order to design and use these materials confidently, it is necessary to quantify the creep behaviour of GMT for the range of stresses and temperatures expected in service. The primary objective of this proposed research is to characterize and model the creep behaviour of the GMT composites under thermo-mechanical loads. In addition, tensile testing has been performed to study the variability in mechanical properties. The thermo-physical properties of the polypropylene matrix including crystallinity level, transitions and the variation of the stiffness with temperature have also been determined. In this work, the creep of a long fibre GMT composite has been investigated for a relatively wide range of stresses from 5 to 80 MPa and temperatures from 25 to 90°C. The higher limit for stress is approximately 90% of the nominal tensile strength of the material. A Design of Experiments (ANOVA) statistical method was applied to determine the effects of stress and temperature in the random mat material which is known for wild experimental scatter. Two sets of creep tests were conducted. First, preliminary short-term creep tests consisting of 30 minutes creep followed by recovery were carried out over a wide range of stresses and temperatures. These tests were carried out to determine the linear viscoelastic region of the material. From these tests, the material was found to be linear viscoelastic up-to 20 MPa at room temperature and considerable non-linearities were observed with both stress and temperature. Using Time-Temperature superposition (TTS) a long term master curve for creep compliance for up-to 185 years at room temperature has been obtained. Further, viscoplastic strains were developed in these tests indicating the need for a non-linear viscoelastic viscoplastic constitutive model. The second set of creep tests was performed to develop a general non-linear viscoelastic viscoplastic constitutive model. Long term creep-recovery tests consisting of 1 day creep followed by recovery has been conducted over the stress range between 20 and 70 MPa at four temperatures: 25°C, 40°C, 60°C and 80°C. Findley’s model, which is the reduced form of the Schapery non-linear viscoelastic model, was found to be sufficient to model the viscoelastic behaviour. The viscoplastic strains were modeled using the Zapas and Crissman viscoplastic model. A parameter estimation method which isolates the viscoelastic component from the viscoplastic part of the non-linear model has been developed. The non-linear parameters in the Findley’s non-linear viscoelastic model have been found to be dependent on both stress and temperature and have been modeled as a product of functions of stress and temperature. The viscoplastic behaviour for temperatures up to 40°C was similar indicating similar damage mechanisms. Moreover, the development of viscoplastic strains at 20 and 30 MPa were similar over all the entire temperature range considered implying similar damage mechanisms. It is further recommended that the material should not be used at temperature greater than 60°C at stresses over 50 MPa. To further study the viscoplastic behaviour of continuous fibre glass mat thermoplastic composite at room temperature, multiple creep-recovery experiments of increasing durations between 1 and 24 hours have been conducted on a single specimen. The purpose of these tests was to experimentally and numerically decouple the viscoplastic strains from total creep response. This enabled the characterization of the evolution of viscoplastic strains as a function of time, stress and loading cycles and also to co-relate the development of viscoplastic strains with progression of failure mechanisms such as interfacial debonding and matrix cracking which were captured in-situ. A viscoplastic model developed from partial data analysis, as proposed by Nordin, had excellent agreement with experimental results for all stresses and times considered. Furthermore, the viscoplastic strain development is accelerated with increasing number of cycles at higher stress levels. These tests further validate the technique proposed for numerical separation of viscoplastic strains employed in obtaining the non-linear viscoelastic viscoplastic model parameters. These tests also indicate that the viscoelastic strains during creep are affected by the previous viscoplastic strain history. Finally, the developed comprehensive model has been verified with three test cases. In all cases, the model predictions agreed very well with experimental results.

APA, Harvard, Vancouver, ISO, and other styles

43

"A comparative study of methodologies for modelling complex surveys modelling an application to saeb 99." Tese, MAXWELL, 2001. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=1745:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

"Transportation networks modelling using object oriented programming." Tese, MAXWELL, 1997. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=1732:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Kale, Kishor B. "Specification and Verification of Tolerances for Parts with Free-Form Surfaces." Thesis, 2013. http://etd.iisc.ernet.in/handle/2005/2815.

Full text

Abstract:

The need for increased product variety and improved aesthetics require the manufacturing enterprise to reduce time to market and to increase use of free-form surfaces in the form of the product. These changes lead to problems in the traditional approach for specification and verification of tolerances especially for a free form surfaces. In the case of freeform surfaces, the desired performance of a product depends on its geometry and is often controlled by intrinsic parameters such as curvature. Design intent therefore requires control on variations in these parameters. Ideally therefore, tolerances have to be applied on these parameters to prescribe allowable variations in the geometry of free-form surfaces. Since only the geometry of the product is controlled in manufacturing, tolerance specification has to ensure that the tolerances specified on the part geometry will ensure that the resulting value of the parameter of interest is within the limits prescribed by the designer. Relationship between allowable range in design parameters and that in geometry is not linear. Tolerance specification therefore becomes a trial and error process requiring considerable expertise and time. This thesis provides designers with a tool to automatically derive the corresponding tolerances to be specified to the manufacturing process to realize the final shape, such that the parameters that are used to control shape of the surface are within the prescribed variations. Automation in acquiring inspection data has brought dramatic changes in procedure for tolerance verification too. Optical scanners and similar non-contact devices provide large amount of points on the surface of the part quite rapidly. The unstructured point data are then processed to determine if the part complies with the given tolerance specifications. For freeform surfaces, current methods of verification uses minimum distance criterion between the nominal surface and unstructured point data. This ignores the correspondence between the points in the two data sets and may result in the rejection of good parts and acceptance of bad parts. There are other unresolved such as the singularity at corners of polyhedral shapes and handling datum. A new approach based on the Medial Axis Transform (MAT) has been proposed. It has been shown that reasoning on the MAT of the nominal model and the measured point set respectively enables the identification of corresponding points in the two sets. Verification of the tolerance allocated is therefore free from the problem mentioned above. MAT exhibits dimensional reduction and hence reduces verification time. It also eliminates surface fitting for detected feature. Results of implementation are provided for tolerance specification and verification using MAT.

APA, Harvard, Vancouver, ISO, and other styles

46

Haladuick, Tyler. "Numerical Simulation of Blast Interaction with the Human Body: Primary Blast Brain Injury Prediction." Thesis, 2014. http://hdl.handle.net/10012/8265.

Full text

Abstract:

In Operations Enduring Freedom and Iraqi Freedom, explosions accounted for 81% of all injuries; this is a higher casualty percentage than in any previous wars. Blast wave overpressure has recently been associated with varying levels of traumatic brain injury in soldiers exposed to blast loading. Presently, the injury mechanism behind primary blast brain injury is not well understood due to the complex interactions between the blast wave and the human body. Despite these limitations in the understanding of head injury thresholds, head kinematics are often used to predict the overall potential for head injury. The purpose of this study was to investigate head kinematics, and predict injury from a range of simulated blast loads at varying standoff distances and differing heights of bursts. The validated Generator of body data multi-body human surrogate model allows for numerical kinematic data simulation in explicit finite element method fluid structure interaction blast modeling. Two finite element methods were investigated to simulate blast interaction with humans, an enhanced blast uncoupled method, and an Arbitrary Lagrangian Eularian fully coupled method. The enhanced blast method defines an air blast function through the application of a blast pressure wave, including ground reflections, based on the explosives relative location to a target; the pressures curves are based on the Convention Weapons databases. LBE model is efficient for parametric numerical studies of blast interaction where the target response is the only necessary result. The ALE model, unlike classical Lagrangian methods, has a fixed finite element mesh that allows material to flow through it; this enables simulation of large deformation problems such as blast in an air medium and its subsequent interaction with structures. The ALE model should be used when research into a specific blast scenario is of interest, since this method is more computationally expensive. The ALE method can evaluate a blast scenario in more detail including: explosive detonation, blast wave development and propagation, near-field fireball effects, blast wave reflection, as well as 3D blast wave interaction, reflection and refraction with a target. Both approaches were validated against experimental blast tests performed by Defense Research and Development Valcartier and ConWep databases for peak pressure, arrival time, impulse, and curve shape. The models were in good agreement with one another and follow the experimental data trend showing an exponential reduction in peak acceleration with increasing standoff distance until the Mach stem effect reached head height. The Mach stem phenomenon is a shock front formed by the merging of the incident and reflected shock waves; it increases the applied peak pressure and duration of a blast wave thus expanding the potential head injury zone surrounding a raised explosive. The enhanced blast model was in good agreement with experimental data in the near-field, and mid-field; however, overestimated the peak acceleration, and head injury criteria values in the far-field due to an over predicted pressure impulse force. The ALE model also over predicted the response based on the head injury criteria at an increased standoff distance due to smearing of the blast wave over several finite elements leading to an increased duration loading. According to the Abbreviated Injury Scale, the models predicted a maximal level 6 injury for all explosive sizes in the near-field, with a rapid acceleration of the head over approximately 1 ms. There is a drastic exponential reduction in the insult force and potential injury received with increasing standoff distance outside of the near-field region of an explosive charge.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Modelling math'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles