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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
391

Modélisation statistique de la géométrie 3D de la cage thoracique à partir d'images médicales en vue de personnaliser un modèle numérique de corps humain pour la biomécanique du choc automobile / Statistical modeling of the 3D geometry of the rib cage from medical images to personalize a numerical human body model for the biomechanics of car crash

Moreau, Baptiste 14 March 2018 (has links)
La sécurité routière est un enjeu majeur de santé publique et de protection des personnes. D'après l'organisation mondiale de la santé (OMS), près de 1,2 millions de personnes meurent chaque année dans le monde suite à des accidents de la route (2015). D’après des données accidentologiques, 36,7% des blessures graves ont pour origine des lésions au thorax (Page et collab., 2012). La biomécanique en sécurité passive a pour rôle d'améliorer notre compréhension du corps humain dans le but de construire de meilleurs outils pour évaluer le risque de blessure.Les modèles numériques d'être humain sont employés pour simuler virtuellement les conditions d'un accident. Aujourd'hui, ils sont de plus en plus utilisés par les constructeurs automobiles et équipementiers pour mieux comprendre les mécanismes lésionnels. Cependant, ils n’existent que dans certaines tailles et ne prennent alors pas en compte les variations morphologiques observées dans la population.L'imagerie médicale 3D donne accès aux géométries des différentes structures anatomiques composant le corps humain. Les hôpitaux regorgent aujourd'hui de quantités d'images 3D couvrant une très large partie de la population en termes d'âge, de corpulence et de sexe.L’objectif global de cette thèse est de modéliser statistiquement la géométrie 3D de la cage thoracique à partir d'images médicales afin de personnaliser un modèle numérique de corps humain pour simuler par éléments finis des conditions de choc automobile. Le premier objectif est d’élaborer un protocole de segmentation une base de CT-scans de manière à obtenir des données géométriques adaptées à la construction d’un modèle statistique de forme de la cage thoracique.Le deuxième objectif est de construire un modèle statistique de forme de la cage thoracique, en prenant en compte sa structure articulée.Le troisième objectif est d’utiliser le modèle statistique de la cage thoracique pour déformer un modèle numérique d’être humain, de manière à étudier l’influence de certains paramètres sur le risque de blessure. / Road safety is a major issue of public health and personal safety. According to the World Health Organization (WHO), nearly 1.2 million people die each year worldwide due to road accidents (2015). According to accident data, 36.7% of serious injuries are caused by thoracic injuries (Page et al., 2012). The aim of biomechanics in passive safety is to improve our understanding of the human body in order to build better tools for assessing the risk of injury.Numerical human body models are used to virtually simulate the conditions of an accident. Today, they are increasingly used by car manufacturers and equipment manufacturers to better understand injury mechanisms. However, they exist only in few sizes and do not take into account the morphological variations observed in the population.3D medical imaging gives access to the geometries of the different anatomical structures that make up the human body. Today, hospitals are full of 3D images covering a very large part of the population in terms of age, body size and sex.The overall objective of this thesis is to statistically model the 3D geometry of the rib cage from medical images in order to personalize a numerical human body model to simulate car crash conditions.The first objective is to develop a segmentation process based on CT-scans in order to obtain geometric data adapted to the construction of a statistical model of shape of the rib cage.The second objective is to build a statistical model of the shape of the rib cage, taking into account its articulated structure.The third objective is to use the statistical model of the rib cage to deform a numerical human body model, in order to study the influence of certain parameters on the risk of injury.
392

Avaliação da mobilidade urbana com ênfase na condição da acidentalidade do usuário vulnerável / Urban mobility evaluation focused in vulnerable user accidentality condition

Igor Machado da Silveira 15 April 2016 (has links)
Atualmente vive-se uma mudança de paradigma no planejamento dos transportes: o ser humano volta a ser o centro da tomada de decisões e o automóvel fica em segundo plano. Para que isso ocorra, são necessárias ferramentas confiáveis as quais avaliem a situação atual das cidades para que sejam traçadas metas no sentido de melhorar a vida da população. A mobilidade urbana sustentável busca a melhoria do transporte baseada no tripé social, ambiental e econômico. Esse trabalho busca avaliar a condição de segurança do usuário vulnerável (sem carenagem protetora) em relação ao usuário não vulnerável (com carenagem), buscando avaliar fatores como o modo escolhido para justificar a segurança do usuário. Apesar da mudança de paradigma, as intervenções urbanas continuam voltadas ao transporte individual, assim o usuário de transporte público de má qualidade migra para outros modos, o que causa o aumento do risco relativo do usuário vulnerável. Um dos fatores que influenciam muito para essa migração é o tempo de viagem, significativamente maior para o usuário do transporte público. / The present time is known by its change in the paradigm of the transport planning. The human being is once again the main point of the decision making and the automotive vehicles are transcending to a second plan. This demands trust tools to evaluate the real situation of the cities so that real goals to improve people\'s life get drawn. The sustainable urban mobility seeks to improve the transport based on the social, environmental and economic tripod. This essay seeks to evaluate the vulnerable user safety condition (without external protection), against the non vulnerable user (with external protection), such as estimate the choice of the user justifying its safety. Besides the change of the scenario, the urban interventions are still focused in the individual transportation kind, what means that the poor conditions of the transit makes users migrate increasing the relative risk for the vulnerable users. One factor that influences the migration is the time spent on the traveling, which is a lot longer for the user of transit.
393

Analyst forecast accuracy, dispersion, and stock returns before and during stock market crashes.

January 2008 (has links)
Wang, Xiaolei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 34-39). / Abstracts in English and Chinese. / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Identification of Stock Market Crashes --- p.5 / Chapter 2.1 --- Identification Criteria --- p.7 / Chapter 2.2 --- Identification Results --- p.8 / Chapter Chapter 3. --- Data --- p.10 / Chapter 3.1 --- Data Issue for Chapter 4 --- p.10 / Chapter 3.2 --- Data Issue for Chapter 5 --- p.12 / Chapter 3.3 --- Data Issue for Chapter 6 --- p.12 / Chapter Chapter 4. --- Examination of AFE --- p.13 / Chapter 4.1 --- Definition of AFE and MAAFE --- p.13 / Chapter 4.2 --- Examination of MAAFE --- p.14 / Chapter 4.3 --- Examination of AFE by Grouping Duration --- p.15 / Chapter Chapter 5. --- Examination of AFD --- p.18 / Chapter Chapter 6. --- Examination of the Relationship between AFD and ESR --- p.22 / Chapter 6.1 --- Portfolio Strategy - Sorting by Size and Dispersion --- p.23 / Chapter 6.2 --- Portfolio Strategy - Sorting by Size and Book to Market Ratio --- p.26 / Chapter 6.3 --- Fama-French Time Series Regression Test (Three-Factor Model) --- p.28 / Chapter 6.4 --- Fama-French Time Series Regression Test (Three-Factor Model with Dispersion on the Right Hand Side) --- p.30 / Chapter 6.5 --- Introduction of a Nonlinear Form of AFD to the Fama-French Model --- p.31 / Chapter Chapter 7. --- Conclusions --- p.32 / References --- p.34 / Appendix Table I to Table XVI --- p.40-55 / Figure I to Figure VI --- p.56-61
394

Assessing the transferability of crash prediction models for two lane highways in Brazil / Avaliação da transferabilidade de modelos de previsão de acidentes em rodovias de pista simples do Brasil

Silva, Karla Cristina Rodrigues 04 September 2017 (has links)
The present study focused on evaluating some crash prediction models for two lane highways on Brazilian conditions. Also, the transferability of models was considered, specifically by means of a comparison between Brazil, HSM and Florida. The analysis of two lane highways crash prediction models was promising when the road characteristics were well known and there was not much difference from base conditions. This conclusion was attained regarding the comparison of results for all segments, non-curved segments and curved segments, confirming that a transferred model can be used with caution. In addition, two novel models for Brazilian two-lane highways segments were estimated. The model developed showed better results for non-curved segments in the calibration/validation sample. Thus, for a general analysis purpose of non-curved segments this model is recommended. Finally, there are many factors that could not be measured by these models and reflects road safety various condition. Even so, the study of crash predict models in Brazilian context could provide a better start point in safety road analysis. / O foco desta pesquisa foi avaliar a aplicação de alguns modelos de previsão de acidentes em rodovias de pista simples de três estados brasileiros. Ainda, a transferabilidade destes modelos foi abordada, especificamente por meio de uma comparação entre características do Brasil, Florida e aquelas recomendadas pelo Highway Safety Manual. O uso dos distintos modelos se mostrou promissor para situações nas quais as características da via se mantiveram semelhantes às condições para as quais os modelos foram desenvolvidos. A avaliação foi empreendida para todos os segmentos homogêneos, separados posteriormente segundo a existência de curvas horizontais. Adicionalmente, dois novos modelos foram equacionados para a amostra brasileira. O modelo de previsão de acidentes desenvolvido apresentou melhores medidas de desempenho para segmentos sem curvas horizontais, sendo recomendável para previsão de acidentes em análises preliminares. Por fim, foi constatado que outros fatores não contemplados pelos modelos podem ter impactado as condições de segurança dos locais estudados. Ainda assim, essa pesquisa representa no contexto do Brasil um ponto de partida em análises relacionadas à segurança de rodovias de pista simples.
395

THE USE OF 3-D HIGHWAY DIFFERENTIAL GEOMETRY IN CRASH PREDICTION MODELING

Amiridis, Kiriakos 01 January 2019 (has links)
The objective of this research is to evaluate and introduce a new methodology regarding rural highway safety. Current practices rely on crash prediction models that utilize specific explanatory variables, whereas the depository of knowledge for past research is the Highway Safety Manual (HSM). Most of the prediction models in the HSM identify the effect of individual geometric elements on crash occurrence and consider their combination in a multiplicative manner, where each effect is multiplied with others to determine their combined influence. The concepts of 3-dimesnional (3-D) representation of the roadway surface have also been explored in the past aiming to model the highway structure and optimize the roadway alignment. The use of differential geometry on utilizing the 3-D roadway surface in order to understand how new metrics can be used to identify and express roadway geometric elements has been recently utilized and indicated that this may be a new approach in representing the combined effects of all geometry features into single variables. This research will further explore this potential and examine the possibility to utilize 3-D differential geometry in representing the roadway surface and utilize its associated metrics to consider the combined effect of roadway features on crashes. It is anticipated that a series of single metrics could be used that would combine horizontal and vertical alignment features and eventually predict roadway crashes in a more robust manner. It should be also noted that that the main purpose of this research is not to simply suggest predictive crash models, but to prove in a statistically concrete manner that 3-D metrics of differential geometry, e.g. Gaussian Curvature and Mean Curvature can assist in analyzing highway design and safety. Therefore, the value of this research is oriented towards the proof of concept of the link between 3-D geometry in highway design and safety. This thesis presents the steps and rationale of the procedure that is followed in order to complete the proposed research. Finally, the results of the suggested methodology are compared with the ones that would be derived from the, state-of-the-art, Interactive Highway Safety Design Model (IHSDM), which is essentially the software that is currently used and based on the findings of the HSM.
396

Étude de la prédiction de chocs véhicule-piéton

Wakim, Christophe 01 December 2005 (has links) (PDF)
Cette thèse CIFRE s'intéresse à la « prédiction de chocs véhicule-piéton » au sein d'un dispositif de protection des piétons, de type pré-crash. <br /><br />Les accidents véhicule-piéton ont d'abord été étudiés, afin de disposer d'une base de référence pour l'évaluation, grâce aux simulations, de systèmes intelligents de protection des piétons. Le comportement des piétons a ensuite été étudié, et un modèle statistique, à temps continu, reposant sur quatre états discrets, a été proposé et évalué. Ce modèle de piétons a été utilisé pour réaliser une prédiction probabiliste des chocs véhicule-piéton. Cette prédiction est réalisée grâce à des simulations de type Monte Carlo. Pour en améliorer l'efficacité, des méthodes de réduction de variance, de type « splitting » et « roulette russe » ont été évaluées. Enfin, diverses hypothèses sur la qualité des mesures, réalisées par le futur dispositif de « détection de piétons et d'estimation de leurs positions et vitesses relatives », qui sont les entrées du module de prédiction de chocs, ont été évaluées, afin de spécifier le besoin sur un tel dispositif. <br /><br />Ce travail a fait l'objet de trois articles publiés et de cinq brevets.
397

Skadeplatsarbete : Ambulanssjuksköterskors upplevelser från skadeplatsarbete / Working at the trauma scene : Ambulance nurses experiences from working at the trauma scene

Gudmundsson, Magnus, Rosén, Martin January 2010 (has links)
<p><strong>Syfte:</strong> Syftet med denna studie var att undersöka ambulanssjuksköterskors upplevelser av arbete på skadeplats med en till fyra drabbade personer. <strong>Metod:</strong> Fyra män och fyra kvinnor, med en erfarenhet mellan två och elva år av ambulanssjukvård, deltog i studien. Semistrukturerade intervjuer genomfördes och data analyserades med innehållsanalys. <strong>Resultat:</strong> Sju kategorier identifierades: Kommunikation, Ledarskap, Medicinskt omhändertagande, Rutiner och riktlinjer, Organisation, Personlighet och relationer, samt Samverkan. Skadeplatsarbetet sker utanför sjukhusets kontrollerade verksamhet. Att varje gång anpassa sig till situationen, omhänderta, leda och organisera arbetet är det som krävs av en ambulanssjuksköterska. Samtidigt ställs stora krav på den omkringliggande organisationen inklusive alla övriga resurser, på att kunna samarbeta och fungera som grupp.<strong> Slutsats:</strong> Skadeplatsarbetet kräver en organisation som måste fungera i minsta detalj och samtidigt alltid förbättra sig. Då många av de upplevda problemen ansågs bero på personlighet och relationer så kräver det dessutom att personalen är stresstålig, ödmjuk, social, kreativ och noggrann.</p> / <p><strong>Aim:</strong> The aim with this study was to analyze the ambulance nurses experiences from working at the trauma scene, with up to four injured patients. <strong>Method:</strong> four men and four women, with a two to eleven years time of experience in the ambulance service, participated. Data from qualitative interviews were analyzed with content analysis. <strong>Result:</strong> Seven categories were identified: Communication, Leadership, Medical treatment, Routines and guidelines, Organization, Personalities and relations, and finally Cooperation. An ambulance nurse needs to be able to adapt to any given situation. To nurse and treat, to lead and organize the activity at the trauma scene, is some things that could be asked from the nurse. A great requirement is also put on the surrounding organization, including all other resources, to cooperate and to function as a team. <strong>Conclusion:</strong> Professional work at the trauma scene demands an organization that needs to function in any unique situation. At the same time it’s just as important that this organization continuously improves. Experiences from problems in prehospital work could be related to personalities and relations between colleagues. This shows the importance of personnel that can handle stress, show humbleness, empathy and skills of being creative, social and precise.</p>
398

Safe Streets, Livable Streets: A Positive Approach to Urban Roadside Design

Dumbaugh, Eric 08 August 2005 (has links)
Transportation safety is a highly contentious issue in the design of cities and communities. To enhance community livability, urban designers, architects and city planners often encourage the placement of street trees, aesthetic street lights, and other roadside features in a buffer zone between the pedestrian realm and the vehicle travelway. While such designs clearly enhance the aesthetic quality of a roadway, conventional geometric design practice regards roadside features located in the clear zone as fixed-object hazards, and strongly discourages their use. This study examines roadside safety in urban environments to better understand the nature of urban fixed-object crashes, as well as the safety impacts of livable streetscape treatments. While the prevailing assumption is that livable street treatments have a negative impact on a roadways safety performance, the existing empirical evidence indicates that such designs are much safer than more conventional roadside designs. Current safety objections to the use of livable street treatments are not based on empirical evidence, but are instead the result of a design philosophy that systematically overlooks the real-world operating behavior of road users. This study details the origin and evolution of this philosophy, termed passive safety, and subjects it to an empirical test to evaluate its applicability to urban arterial roadways. It finds that passive safety assumptions do not meaningfully explain empirical observations of crash frequency and severity. To enhance contemporary geometric design practice, this study then proceeds to more thoroughly examine the nature and characteristics of urban roadside crashes, and proposes a new design approach, termed positive design that better addresses the twin goals of safety and livability.
399

Analyse du comportement mécanique des côtes humaines en dynamique

Charpail, Estelle 27 October 2006 (has links) (PDF)
Dans les accidents automobiles, les blessures au thorax arrivent en deuxième position après celles à la tête pour : la zone la plus souvent lésée et le nombre global de décès et de lésions sérieuses. Les fractures de côtes et les volets costaux sont les blessures les plus fréquentes suivies par les lacérations des poumons, du foie et des artères. Afin de mieux comprendre la réponse du thorax lors d'un crash, des modèles en éléments finis ont été développés. Cependant, ces modèles échouent à reproduire des mécanismes lésionnels détaillés tels que les fractures costales. Améliorer la biofidélité de ces modèles passe par une meilleure connaissance des propriétés mécaniques des côtes. L'objectif de ce travail est donc d'étudier expérimentalement et numériquement le comportement mécanique des côtes humaines en dynamique. Des essais de compression axiale et des tests de calcination ont été réalisés pour caractériser le matériau costal. Des essais de flexion trois points et un nouvel essai permettant de solliciter la côte dans la direction antéropostérieure ont servi à caractériser la structure. Les résultats montrent que le niveau costal influence les propriétés de matériaux en compression et le comportement en sollicitation antéropostérieure. Les simulations numériques ont permis de mettre en évidence l'influence de l'os spongieux dans le comportement mécanique des modèles ainsi que l'importance de la géométrie sur la réponse en effort. Aucune influence de l'âge, ni de la vitesse de sollicitation a été relevée. Il faut noter le nombre de pièces testées est petit par rapport aux variations inter-individuelles.
400

Safety belts in lifeboats : evaluation and dynamic tests for improved launch safety /

Hansson, Anders. Stolt, Andreas. January 2002 (has links) (PDF)
Thesis (M.S.)--Kungl. Tekniska högskolan, 2002. / Includes bibliographical references (p. 125-126). Also available online via the Swedish National Road and Transport Research Institute web site (www.vti.se).

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