Made available in DSpace on 2014-07-29T15:13:43Z (GMT). No. of bitstreams: 1 alineteseca.pdf: 944325 bytes, checksum: 5f0b947649cbf727f1cd020b11cdb011 (MD5) Previous issue date: 2008-12-15 / Sheep rearing is becoming an important economic activity, where it is necessary to establish the ideal slaughter weight per genetic group and sex to acheive standardized carcasses which meet customer needs in terms of product quality.This experiment evaluated the effect of genetic group and slaughter weight on carcass traits and meat quality in lambs. Twenty four Santa Ines (SI), 24 ½ Ile de France x ½ Santa Inês (ILE x SI) and 8 ½ Texel x ½ Santa Inês (TE x SI), slaughtered at different weights (30, 35, 40 and 45 kg ) were used.Eye rib area and fat thickness were measured in vivo and on the carcass. After a 16 hour food and water fast the animals were slaughtered conventionally and the carcasses placed in a cold chamber at 4ºC/24h. pH was measured at slaughter and after 24h as were subjective measurements on the Longissimus dorsi. A section of the rib region from the 11th to 13th ribs of the left side of the carcass was used for tissue and fractional composition, physic-chemical parameters and fatty acid composition. The experiment was in a 3 x 2 x 4 factorial design. For physic-chemical and fatty acids a 3 x 4 factorial and analysed using CORR (Correlation), REG (Regression) and Duncan (5%) means test in SAS ®. Genetic group did not influence (P>0.05) means for rib eye area or fat thickness measured by ultrasound or paquimeter. These measurements increased with slaughter weight. Tissue composition was influenced by genetic group and slaughter weight (P<0.05). The Texel x Santa Inês had most muscle (63.75 g), fat (53.75 g), bone (29.37 g) and edible portion (78.75%) at 35 and 45 kg . Slaughter weight centesimal composition, with an increase in total lipids as weight increased. No significant differences were found for final pH between genetic groups and slaughter weights. Genetic group did not influence colour (3.32), shear force (3.57 kgf) or loss in cooking (24.05%) of the Longissimus dorsi, but slaughter weight affected these, causing stronger colour, tougher meat and greater loss in cooking as slaughter weight increased. Significant differences were found in the sensorial traits of the meat with different genetic groups and slaughter weights. The fatty acids found included oleic (43%); palmitic (22%) and estearico (18%). Higher quantities of desirable fatty acids were found in the Texel x Santa Inês (66.78%) group. Slaughter weight caused a significant difference (P<0.05) in the fatty acid profile of saturated and polyunsaturated fats. / A criação de ovinos surge como atividade de importância econômica, na qual busca-se estabelecer o peso ideal para abate por grupo genético e sexo, proporcionando carcaças padronizadas que satisfaçam as perspectivas dos consumidores em termos de qualidade do produto. Objetivou-se com este experimento avaliar os grupos genéticos e peso de abate nas características da carcaça e qualidade da carne de cordeiros. Foram utilizados 24 cordeiros Santa Inês (SI), 24 cordeiros mestiços ½ Ile de France x ½ Santa Inês (ILE x SI) e 8 cordeiros mestiços ½ Texel x ½ Santa Inês (TE x SI), abatidos em diferentes pesos (30, 35, 40 e 45 kg). As análises de área de olho de lombo e espessura de gordura foram realizadas in vivo e na carcaça dos animais. Após jejum e dieta hídrica de 16 h, os animais foram submetidos ao abate convencional e as carcaças permaneceram em câmara fria a 4ºC/24h. Durante esse período foi realizada a leitura de pH inicial e final (24 h) e avaliações subjetivas no músculo Longissimus dorsi. Posteriormente foram retiradas as frações correspondentes à região da 11ª a 13ª costelas da carcaça esquerda para as análises de composição tecidual e centesimal, avaliação dos parâmetros físico-químicos e composição de ácidos graxos. O delineamento utilizado foi inteiramente casualizado em esquema de fatorial 3 (grupo genético) x 2 (sexo) x 4 (peso de abate). Para as análises físico-químicas e perfil de ácidos graxos foi utilizado fatorial 3 x 4 com aplicação de procedimentos CORR (Correlação), REG (Regressão) e teste de médias (Duncan 5%) do programa estatístico SAS. Os grupos genéticos não influenciaram (P>0,05) os valores médios da área de olho de lombo e espessura de gordura pelo ultra-som e paquímetro. Observou-se maior a área de olho de lombo e espessura de gordura na 12a costela com o aumento dos pesos ao abate. A composição tecidual foi influenciada pelos grupos genéticos e peso ao abate (P<0,05). Os animais Texel x Santa Inês apresentaram maior quantidade de músculo (63,75 g), gordura (53,75 g), osso (29,37 g) e porção comestível (78,75%) aos 35 e 45 kg. Houve efeito dos pesos de abate para a composição centesimal, apresentando aumento do teor de lipídeos à medida que os pesos eram elevados. Não houve diferença para pH final entre os grupos genéticos e pesos ao abate avaliados. Os grupos genéticos não influenciaram a cor (3,32), força de cisalhamento (3,57 kgf) e perda por cozimento (24,05%) do músculo Longissimus dorsi, no entanto, houve diferença significativa para os grupos de peso ao abate, atribuindo-se a coloração mais acentuada, carne menos macia e maior perda de líquido por cozimento com a elevação do peso ao abate. Foram detectadas diferenças nos atributos sensoriais avaliados nas carnes de cordeiros de diferentes genótipos e pesos ao abate. Os ácidos graxos encontrados em maior concentração foram o oléico (43%); palmítico (22%); esteárico (18%). Verificou-se maiores quantidades de ácidos graxos desejáveis em animais Texel x Santa Inês (66,78%). O peso de abate dos cordeiros determinou diferença significativa (P<0,05) no perfil dos ácidos graxos saturados e poliinsaturados.

Myndigheten för samhälle och beredskap (MSB) är den myndighet som på central nivå ska verka för och utveckla förmågan till effektiva räddningsinsatser. I dess uppgift ingår att stödja räddningstjänsterna med information, utbildning och övningsverksamhet. På kommunal nivå svarar kommunerna inom sitt geografiska område och insatserna utförs av räddningstjänsten. Anställda inom räddningstjänsten består av både heltidsanställda brandmän och räddningspersonal i beredskap (RiB), det som tidigare kallades för deltidsbrandmän. RiB är den vanligaste typen av anställningar på mindre tätorter. Att rekrytera in RiB har blivit ett problem och en utmaning för kommunerna då människor inte längre bor och arbetar på samma ort. Kan kommunerna inte rekrytera in personal får de svårt att upprätthålla den beredskap som de enligt lag är skyldiga att ha. De personer som väljer att bli RiB är beroende av att huvudarbetsgivare godkänner detta. Här kan man se att det skett en minskning inte bara bland de privata företagarna utan även bland de offentliga arbetsgivarna. Syftet med vår undersökning är att få RiB:s perspektiv på hur kompetensförsörjningen till räddningstjänsten ska se ut i framtiden. Vi har valt att använda oss av en kvalitativ undersökning i form av intervjuer. Våra respondenter är 13 RiB-anställda som har arbetat i räddningstjänsten mellan 1 och 30 år och är i åldrarna 20-58 år. De arbetar på fyra olika brandstationer någonstans i Sverige och det gemensamma för alla fyra stationer är att de är belägna på mindre orter. Vi har analyserat vårt intervjumaterial och kopplat det till våra teorier. Resultatet visar att respondenterna är medvetna om problemet med att bemanna upp brandstationer på mindre orter och de har många idéer kring en möjlig lösning på problemet. De ser dock fortfarande ljust på framtiden, att RiB på ett eller annat sätt kommer att finnas kvar. / The Swedish Rescue Agency is the central authority body that shall promote and develop the capacity for effective emergency and rescue work. Within its responsibility is support to the rescue crews with information, education and training development. The council is responsible for rescue and emergency services within council boundaries. Employees with emergency services consist of both of full-time firemen and standby rescue crew. They used to be called part-time firemen and are known today as standby rescue crew. The standby crews are most commonly employed in smaller villages.  Recruiting standby rescue crew has always been a problem and a challenge for small councils due to the fact that there are less people to choose from that work and live in the same place. This creates a problem of having enough staff there required by law. People who choose to become part-time firemen are dependent on their main employees to approve their needs as part-time firemen. Due to private and public employees being less tolerant to the needs required to be part-time firemen there has been a reduction in their numbers. Our main purpose is to get the standby rescue crews perspective on how the emergency services can recruit employees in the future.  We have chosen to use a qualitative study in the form of interviews. Our respondents are 13 part-time firemen that have worked as rescue crews between 1 and 30 years and are aged between 20 to 58. They work in four different fire stations throughout Sweden and have in common that they are all placed in small communities. We have analyzed our interviews and linked them to our theories. The result shows that the respondents are aware of the problems of having enough crew at the stations in smaller communities and they have many ideas for a possible solution to the problems. They are feeling positive that standby crews will be around in the future in one form or another.

In this thesis a numerical study has been undertaken to investigate turbulent flow and heat transfer in a number of flow problems, representing the gas-cooled reactor core flows. The first part of the research consisted of a meticulous assessment of various advanced RANS models of fluid turbulence against experimental and numerical data for buoyancy-modified mixed convection flows, such flows being representative of low-flow-rate flows in the cores of nuclear reactors, both presently-operating Advanced Gas-cooled Reactors (AGRs) and proposed ‘Generation IV’ designs. For this part of the project, an in-house code (‘CONVERT’), a commercial CFD package (‘STAR-CD’) and an industrial code (‘Code_Saturne’) were used to generate results. Wide variations in turbulence model performance were identified. Comparison with the DNS data showed that the Launder-Sharma model best captures the phenomenon of heat transfer impairment that occurs in the ascending flow case; v^2-f formulations also performed well. The k-omega-SST model was found to be in the poorest agreement with the data. Cross-code comparison was also carried out and satisfactory agreement was found between the results.The research described above concerned flow in smooth passages; a second distinct contribution made in this thesis concerned the thermal-hydraulic performance of rib-roughened surfaces, these being representative of the fuel elements employed in the UK fleet of AGRs. All computations in this part of the study were undertaken using STAR-CD. This part of the research took four continuous and four discrete design factors into consideration including the effects of rib profile, rib height-to-channel height ratio, rib width-to-height ratio, rib pitch-to-height ratio, and Reynolds number. For each design factor, the optimum configuration was identified using the ‘efficiency index’. Through comparison with experimental data, the performance of different RANS turbulence models was also assessed. Of the four models, the v^2-f was found to be in the best agreement with the experimental data as, to a somewhat lesser degree were the results of the k-omega-SST model. The k-epsilon and Suga models, however, performed poorly. Structured and unstructured meshes were also compared, where some discrepancies were found, especially in the heat transfer results. The final stage of the study involved a simulation of a simplified 3-dimensional representation of an AGR fuel element using a 30 degree sector configuration. The v^2-f model was employed and comparison was made against the results of a 2D rib-roughened channel in order to assess the validity and relevance of the precursor 2D simulations of rib-roughened channels. It was shown that although a 2D approach is extremely useful and economical for ‘parametric studies’, it does not provide an accurate representation of a 3D fuel element configuration, especially for the velocity and pressure coefficient distributions, where large discrepancies were found between the results of the 2D channel and azimuthal planes of the 3D configuration.

Chest compressions during cardiopulmonary resuscitation (CPR) may be associated with iatrogenic chest wall injuries. The extent to which these CPR-associated chest wall injuries contribute to a delay in the respiratory recovery of cardiac arrest survivors has not been sufficiently explored. In a single-center retrospective cohort study, surviving intensive care unit (ICU) patients, who had undergone CPR due to medical reasons between 1 January 2018 and 30 June 2019, were analyzed regarding CPR-associated chest wall injuries, detected by chest radiography and computed tomography. Among 109 included patients, 38 (34.8%) presented with chest wall injuries, including 10 (9.2%) with flail chest. The multivariable logistic regression analysis identified flail chest to be independently associated with the need for tracheostomy (OR 15.5; 95% CI 2.77–86.27; p = 0.002). The linear regression analysis identified pneumonia (β 11.34; 95% CI 6.70–15.99; p < 0.001) and the presence of rib fractures (β 5.97; 95% CI 1.01–10.93; p = 0.019) to be associated with an increase in the length of ICU stay, whereas flail chest (β 10.45; 95% CI 3.57–17.33; p = 0.003) and pneumonia (β 6.12; 95% CI 0.94–11.31; p = 0.021) were associated with a prolonged duration of mechanical ventilation. Four patients with flail chest underwent surgical rib stabilization and were successfully weaned from the ventilator. The results of this study suggest that CPR-associated chest wall injuries, flail chest in particular, may impair the respiratory recovery of cardiac arrest survivors in the ICU. A multidisciplinary assessment may help to identify patients who could benefit from a surgical treatment approach.

The heat transfer and friction augmentation in the fully developed portion of a 2:1 aspect ratio rectangular channel with orthogonal ribs at channel Reynolds numbers of 20,000, 30,000, and 40,000 is studied both experimentally and computationally. Ribs are applied to the two opposite wide walls. The rib aspect ratio is varied systematically at 1, 3, and 5, with a constant rib height and constant rib pitch (rib-pitch-to-rib-height ratio of 10). The purpose of the study is to extend the knowledge of the performance of rectangular channels with ribs to include high aspect ratio ribs. The experimental investigation is performed using transient Thermochromic Liquid Crystals technique to measure the distribution of the local Nusselt numbers on the ribbed walls. Overall channel pressure drop and friction factor augmentation is also obtained with the experimental setup. A numerical simulation is also performed by solving the 3-D Reynolds-averaged Navier-Stokes equations using the realizable-k-Greek lowercase letter episilon] turbulence model for closure. Flow visualization is obtained from the computational results as well as numerical predictions of local distributions of Nusselt numbers and overal channel pressure drop. Results indicate that with increasing rib width, the heat transfer augmentation of the ribbed walls decreases with a corresponding reduction in channel pressure drop.

Frontal motor vehicle collisions (MVCs) resulted in 10,813 fatalities and 937,000 injuries in 2014, which is more than any other type of MVC. In order to mitigate the injuries and fatalities resulting from MVCs, new safety restraint technologies and more biofidelic anthropomorphic test devices (ATDs) have been developed. However, the biofidelity of these new ATDs must be evaluated, and the mechanisms of injury must be understood in order to accurately predict injury. Evaluating the biomechanical response, injury mechanisms, and injury threshold of the thorax are particularly important because the thorax is one of the most frequently injured body regions in MVCs. Furthermore, sustaining a severe thoracic injury in an MVC significantly increases mortality risk. The overall objective of this dissertation was to evaluate the biomechanical responses of human surrogates under various frontal loading conditions. This objective was divided into three sub-objectives: 1) to evaluate the biofidelity of the current frontal impact ATDs, 2) to evaluate the effect of different safety restraints on occupant responses, and 3) to evaluate rib material properties with respect to sex, age, structural response, and loading history. In order to meet sub-objectives 1 and 2, full-scale frontal sled tests were performed on three different human surrogates: the 50th percentile male Hybrid III (HIII) ATD, the 50th percentile male Test Device for Human Occupant Restraint (THOR-M) ATD, and approximately 50th percentile male post-mortem human surrogates (PMHS). All surrogates were tested under three safety restraint conditions: knee bolster (KB), KB and steering wheel airbag (KB/SWAB), and knee bolster airbag and SWAB (KBAB/SWAB). The kinematic, lower extremity, abdominal, thoracic, and neck responses were then compared between surrogates and restraint conditions. In order to assess biofidelity, the ATD responses were compared to the PMHS responses. For both the kinematic and thoracic responses, the HIII and THOR-M had comparable biofideltiy. However, the HIII responses were slightly more biofidelic. The ATDs experienced similar lower extremity kinetics, but very different kinetics at the upper and lower neck due to differences in design. Evaluation of the different restraint conditions showed that the SWAB and KBAB both affected injury risk. The SWAB decreased head injury risk for all surrogates, and increased or decreased thoracic injury risk, depending on the surrogate. The KBAB decreased the risk of femur injury, but increased or decreased tibia injury risk depending on the surrogate and injury metric used to predict risk. In order to meet sub-objective 3, the tensile material properties of human rib cortical bone and the structural properties of whole ribs were quantified at strain rates similar to those observed in frontal impacts. The rib cortical bone underwent coupon tension testing, while the whole ribs underwent bending tests intended to simulate loading from a frontal impact. The rib material properties accounted for less than 50% of the variation observed in the whole rib structural properties, indicating that other factors, such as rib geometry, were also influencing the structural response of whole ribs. Age was significantly negatively correlated with the modulus, yield stress, failure strain, failure stress, plastic strain energy density, and total strain energy density. However, sex did not significantly influence any of the material properties. Cortical bone material properties were quantified from the ribs that underwent the whole rib bending tests and subject-matched, untested (control) ribs in order to evaluate the effect of loading history on material properties. Yield stress and yield strain were the only material properties that were significantly different between the previously tested and control ribs. The results of this dissertation can guide ATD and safety restrain design. Additionally, this dissertation provides human surrogate response data and rib material property data for the validation of finite element models, which can then be used to evaluate injury mitigation strategies for MVCs. / PHD / Frontal motor vehicle collisions (MVCs) resulted in 10,813 fatalities and 937,000 injuries in 2014, which is more than any other type of MVC. In order to mitigate the injuries and fatalities resulting from MVCs, new safety restraint technologies, e.g., seat belts, and more biofidelic (human-like) anthropomorphic test devices (ATDs), i.e., crash test dummies, have been developed. However, the biofidelity of these new ATDs must be evaluated, and the mechanisms of injury must be understood in order to accurately predict injury. Evaluating the biomechanical response, injury mechanisms, and injury threshold of the thorax (chest) are particularly important because the thorax is one of the most frequently injured body regions in MVCs. Furthermore, sustaining a severe thoracic injury in an MVC significantly increases the risk of death. The overall objective of this dissertation was to evaluate the biomechanical responses of human surrogates under various frontal loading conditions. This objective was divided into three sub-objectives: 1) to evaluate the biofidelity of the current frontal impact ATDs, 2) to evaluate the effect of different safety restraints on occupant responses, and 3) to evaluate rib material properties with respect to sex, age, structural response, and loading history. In order to meet sub-objectives 1 and 2, frontal crash tests were simulated in the laboratory using a crash sled. These sled tests were performed on three different human surrogates: the Hybrid III (HIII) ATD, the Test Device for Human Occupant Restraint (THOR-M) ATD, and post-mortem human surrogates (PMHS), i.e., cadavers. All surrogates were tested under three safety restraint conditions: knee bolster (KB), KB and steering wheel airbag (KB/SWAB), and knee bolster airbag and SWAB (KBAB/SWAB). The kinematic (body movements), lower extremity, abdominal, thoracic, and neck responses were then compared between surrogates and restraint conditions. In order to assess biofidelity, the ATD responses were compared to the PMHS responses. For both the kinematic and thoracic responses, the HIII and THOR-M had comparable biofideltiy. However, the HIII responses were slightly more biofidelic. The ATDs experienced similar lower extremity kinetics (forces and moments), but very different kinetics at the upper and lower neck due to differences in design. Evaluation of the different restraint conditions showed that the SWAB and KBAB both affected injury risk. The SWAB decreased head injury risk for all surrogates, and increased or decreased thoracic injury risk, depending on the surrogate. The KBAB decreased the risk of femur injury, but increased or decreased tibia injury risk depending on the surrogate and how injury risk was predicted. In order to meet sub-objective 3, the material properties of human rib cortical bone and the structural response of whole ribs were quantified under experimental conditions reminiscent of what the bone would experience during a frontal impact. The rib cortical bone underwent material testing, while the whole ribs underwent bending tests intended to simulate a frontal impact. The rib material properties only partially influenced the structural response of the whole rib. This indicated that other factors, such as rib shape and thickness, were also influencing the structural response. Age was correlated to a decrease in several material properties. However, there was no significant difference between male and female material properties. Some differences in material properties were observed in cortical bone from fractured and intact ribs, indicating that the fracture influenced the rib material properties. results of this dissertation can guide ATD and safety restrain design. Additionally, this dissertation provides human surrogate response data and rib material property data for finite element (computer) models, which can then be used to evaluate injury prevention strategies for MVCs.

The aim of this diploma thesis is to design a load-bearing structure of the botanical pavillion in Jihlava. The construction is designed as a variable structure of both steel and timber. Each solution has a different type of ribs. The layout is a hexadecagon with maximum dimension of 30 meters. The height of the building is considered to be 10 meters.

This study performed detailed measurements on and around scaled up conducting and adiabatic airfoils with and without film cooling. The conducting vane was a matched Bi airfoil, which accurately scaled the convective heat transfer and conduction through the solid, in order to produce non-dimensional surface temperatures and thermal boundary layers that were representative of an actual engine. Measurements made on all vane models included surface temperature measurements and thermal profiles above the walls. Separate measurements on non-film cooled and film cooled conducting models allowed for the individual contributions of the internal convective cooling and external film cooling to the overall cooling scheme to be quantified. Surface temperature and thermal field measurements above the wall were also performed on a film cooled adiabatic model. For the conducting model with internal cooling only, strong streamwise temperature variations were seen. The surface temperature variations were highly dependent on the local external and internal heat transfer coefficients. Spanwise temperature variations also existed, but were modest in comparison to streamwise variations. Comparing the thermal fields above the film cooled adiabatic and conducting walls allowed for the assumption that the conducting wall would not significantly affect the thermal field in the film cooling jet to be tested. Near the edge of the film cooling jet the developing thermal boundary layer had a clear effect on the overlying gas temperature, suggesting that the common assumption that the adiabatic wall temperature is the appropriate driving temperature for heat transfer to a film cooled wall was invalid. On the jet centerline thermal boundary layer effects were less influential, due to the development of a new, thin boundary layer. This suggested that the adiabatic wall temperature as driving temperature for heat transfer was a reasonable assumption on the jet centerline for most cases tested. As film cooling momentum flux ratio increase, thermal boundary layer effects became more influential on the jet centerline. Additionally, the high resolution surface temperature measurements and thermal field measurements above the wall presented in the current study represent a significant improvement in the data available for validation of computational simulations of conducting turbine airfoils. / text

An experimental study was designed to investigate the effect of different parameters on the development and structure of turbulent 3D offset jets. The present investigation considered the effects of offset height ratio, expansion ratio, surface roughness and rib placement on the flow dynamics of a turbulent 3D offset jet. The velocity measurements were performed using an acoustic Doppler velocimetry (ADV) and particle image velocimetry (PIV). Measurements were conducted within the symmetry and lateral planes. For the PIV technique, the measurements in the symmetry and lateral planes were conducted over a streamwise range of 0 ≤ x/bo ≤ 80 and 12 ≤ x/bo ≤ 60, respectively (where bo is the nozzle height). Likewise, velocity measurements using the ADV technique were conducted over a range of 4 ≤ x/bo ≤ 45 in both the symmetry and lateral planes. The velocity measurements were analyzed using both one-point and multi-point statistics. The one-point statistics included profiles of the mean velocities, Reynolds stresses and some of the budget terms in the turbulent kinetic energy transport equation. The quadrant analysis technique was used to investigate the dominant events that contribute towards the Reynolds shear stress. The two-point correlation analysis was used to investigate how the turbulence quantities are correlated. Information obtained from the two-point correlation analysis was also used to investigate the inclination of vortical structures within the inner and outer shear layers of the 3D offset jet. The direction of the positive mean shear gradient played an active role in the inclination of these vortical structures within the inner and outer shear layers. The reattachment process resulted in the breakdown of these structures within the developing region. Similarly, various length scales were estimated from these structures. The proper orthogonal decomposition was used to examine the distribution of the turbulent kinetic energy within the offset jet flow. Also, the dynamic role of the large scale structures towards the turbulent intensities, turbulent kinetic energy and Reynolds shear stress was investigated. / October 2016

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.