Etude de matériaux réfractaires à comportement mécanique non linéaire par mesure de champs de déformations

The present thesis aimed to apply digital image correlation (DIC) used for kinematic fields’ measurements as a support for the experimental characterization of refractory materials with specific non-linear behaviour. Model and industrial materials with different degrees of flexibility were studied. The first type of materials was a single phase model flexible aluminium titanate material (AT VF) developed for academic purposes by improving the grain growth. Its non-linear mechanical behaviour was obtained thanks to the thermal expansion mismatch of its grains according to the different crystallographic axis. The second one is multi-phased magnesia based industrial materials, whose flexibility is less accentuated, and for which the non-linear mechanical behaviour is obtained thanks to the thermal expansion coefficients mismatch between spinel aggregates and magnesia matrix. In order to apply the optical methods on these materials which exhibit lower strain-to-rupture, it was necessary to optimize the accuracy of these techniques by improving experimental conditions.In the case of AT VF, DIC and mark tracking method have been applied on four-points bending test at room temperature to underline the material asymmetric mechanical behaviour which induces a significant shift of the neutral fibre and to evaluate the relative displacement of rolls. The application of DIC has been extended to other experimental testing method such as Brazilian and Wedge Splitting test using the multi-phased magnesia based materials. This highlighted fracture mechanisms (crack occurrence and propagation) and the presence of crack branching phenomenon promoted thanks to an initial micro-cracks network voluntary introduced by thermal expansion mismatch between the different phases so as to improve their thermal shock resistance. From displacement experimentally obtained by DIC, a finite element method updating (FEMU-U) has been developed to determine material properties.Cette thèse avait pour objectif de mettre en place et d’appliquer les techniques de mesure de champs de déplacements et de déformations (corrélation d’images numériques CIN) pour caractériser le comportement mécanique non linéaire de matériaux réfractaires. L’étude a été réalisée sur différents types de matériaux présentant des degrés variables de flexibilité : un matériau modèle monophasé à base de titanate d’aluminium (TA VF) et des matériaux industriels multi-phasés à base de magnésie. La flexibilité dans le cas du TA VF est obtenue grâce à l’anisotropie de la dilatation thermique entre les trois axes cristallographiques, et dans le cas des matériaux industriels grâce à la différence de coefficients de dilatation entre les agrégats de spinelle et la matrice magnésienne. Ces matériaux industriels ayant une déformation à rupture plus faible, la technique de corrélation d’images a dû être optimisée en ajustant au mieux les conditions expérimentales.La CIN et la méthode de suivi de marqueurs ont permis de mettre en évidence le caractère dissymétrique du comportement mécanique en flexion du TA VF entre la zone de l’éprouvette sollicitée en traction et celle en compression et d’investiguer le déplacement relatif des rouleaux du dispositif de flexion. Cette dissymétrie de comportement engendre un déplacement progressif de la fibre neutre au fur et à mesure que la charge appliquée augmente. Cette technique a ensuite été étendue à d’autres essais tels que l’essai brésilien et le Wedge Splitting appliqués aux matériaux industriels magnésiens. La CIN a ainsi permis d’illustrer les mécanismes de rupture (initiation et propagation de fissures) et de mettre en évidence la présence de phénomènes de « crack branching » obtenus grâce au réseau initial de microfissures volontairement généré au sein du matériau par différentiel de dilatation entre phases dans le but d’améliorer sa résistance aux chocs thermiques. Enfin, à partir des champs de déplacements obtenus par corrélation d’images, la méthode de recalage par éléments finis a été développée et utilisée pour déterminer l’évolution des propriétés élastiques du matériau pendant l’essai

Hydatidose du rachis cervical : A propos d’un cas

L’hydatidose intéresse l’os dans 0,5 à 2 % des cas, dont 44 % de localisations au niveau rachidien. L’étage cervical est la moins fréquente des localisations rachidiennes. Cette atteinte est grave par le risque de compression médullaire haute, et surtout par son caractère récidivant. Les auteurs présentent l’observation d’un jeune patient admis pour une tétraplégie progressive, due à une hydatidose vertébro-médullaire cervicale ; son diagnostic a été évoquée sur l’imagerie par résonance magnétique et confirmée par l’étude anatomopathologique

Calculating the SAR distribution in two human head models exposed to printed antenna with coupling feed for GSM/UMTS/LTE/WLAN operation in the mobile phone

The scope of this paper is to examine the Specific Absorption Rate (SAR) inside the human head model exposed to the radiation of a low-profile printed monopole antenna with coupling feed for GSM/UMTS/LTE/WLAN operation in the slim mobile phone. The presented antenna operates for most of the mobile phone applications such as the GSM850, GSM900, GSM1900, UMTS2100, LTE2300, LTE2500 and WLAN2400 bands. In this study, two different human head models are used: homogenous spherical head and spherical seven layer model. In addition, the effects of operating frequency and the gap distance between the mobile phone antenna and the human head model on distributions of the SAR within the human head are analyzed. All the simulations are done for three different distances between the antenna and the head model (5 mm, 10 mm, 20 mm). Furthermore, the SAR levels for the head tissues are calculated for and with accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP). All numerical simulations are performed using the Ansoft HFSS Software and CST Microwave Studio

Complex Leadership in Healthcare: A Scoping Review

Abstract Background: Nowadays, health systems are generally acknowledged to be complex social systems. Consequently, scholars, academics, practitioners, and policy-makers are exploring how to adopt a complexity perspective in health policy and system research. While leadership and complexity has been studied extensively outside health, the implications of complexity theories for the study of leadership in healthcare have received limited attention. We carried out a scoping review of complex leadership (CL) in healthcare to investigate how CL in healthcare has been defined, theorised and conceptualised and to explore how ‘CL’ has been applied in healthcare settings. Methods: We followed the methodological steps proposed by (Arksey and O’Malley, 2005): (1) specifying the research question, (2) identifying relevant studies, (3) study selection, (4) charting the data, (5) collating and summarizing the findings, and (6) reporting the results. We searched using Medline, Psychinfo, Wiley online library, and Google Scholar. Our inclusion criteria were: publication type (peer reviewed articles, theses, and book chapters); phenomenon of interest: complex leadership; context: healthcare and period of publication: between 2000 and 2016. Results: Our search and selection resulted in 37 papers (16 conceptual papers, 14 empirical studies and 7 advocacy papers). We note that empirical studies on CL are few and almost all research reported by these papers was carried out in the North (mainly in USA and UK). We found that there is some variation in definitions of CL. Furthermore, the research papers adopt mostly an explorative or explanatory approach and do not focus on assessing effectiveness of CL approaches. Finally, we found that the majority of researchers seem to adhere to the mathematical complexity perspective. Conclusion: Complexity concepts derived from natural sciences may not automatically fit management of health services. Further research into how social complexity theories may offer researchers useful grounds to empirically test CL theories in health settings is warranted. Specific attention should be paid to the multi-layered nature of leadership

DETECTION OF CRESCENT SAND DUNES CONTOURS IN SATELLITE IMAGES USING AN ACTIVE SHAPE MODEL WITH A CASCADE CLASSIFIER

Crescent sand dunes called barchans are the fastest moving sand dunes in the desert, causing disturbance for infrastructure and threatening human settlements. Their study is of great interest for urban planners and geologists interested in desertification (Hugenholtz et al., 2012). In order to study them at a large scale, the use of remote sensing is necessary. Indeed, barchans can be part of barchan fields which can be composed of thousands of dunes (Elbelrhiti et al.2008). Our region of interest is located in the south of Morocco, near the city of Laayoune, where barchans are stretching over a 400&thinsp;km corridor of sand dunes. We used image processing techniques based on machine learning approaches to detect both the location and the outlines of barchan dunes. The process we developed combined two main parts: The first one consists of the detection of crescent shaped dunes in satellite images using a supervised learning method and the second one is the mapping of barchans contours (windward, brink and leeward) defining their 2D pattern. For the detection, we started by image enhancement techniques using contrast adjustment by histogram equalization along with noise reduction filters. We then used a supervised learning method: We annotated the samples and trained a hierarchical cascade classifier that we tested with both Haar and LBP features (Viola et Jones, 2001; Liao et al., 2007). Then, we merged positive bounding boxes exceeding a defined overlapping ratio. The positive examples were then qualified to the second part of our approach, where the exact contours were mapped using an image processing algorithm: We trained an ASM (Active Shape Model) (Cootes et al., 1995) to recognize the contours of barchans. We started by selecting a sample with 100 barchan dunes with 30 landmarks (10 landmarks for each one of the 3 outlines). We then aligned the shapes using Procrustes analysis, before proceeding to reduce the dimensionality using PCA. Finally, we tested different descriptors for the profiles matching: HOG features were used to construct a multivariate Gaussian model, and then SURF descriptors were fed an SVM. The result was a recursive model that successfully mapped the contours of barchans dunes. We experimented with IKONOS high resolution satellite images. The use of IKONOS high resolution satellite images proved useful not only to have a good accuracy, but also allowed to map the contours of barchans sand dunes with a high precision. Overall, the execution time of the combined methods was very satisfying.</p

Investigation of dosimetry in four human head models for planar monopole antenna with a coupling feed for LTE/WWAN/WLAN internal mobile phone

The objective of the present study is to evaluate the Specific Absorption Rate (SAR) within the human head model exposed to the radiation of planar monopole antenna with T-shaped coupling feed and an inductive shorting strip. The presented design has a compact structure, a planar configuration and occupying a small size of 36×20mm2. Two wide bands can be generated by the proposed antenna 546 MHz (734-1280 MHz) and 1066 MHz (1934-3000 MHz) for the LTE/WWAN/WLAN internal mobile phone. The antenna performance parameters comprising return loss, radiation patterns, and gain are discussed. In this research work four different human head models have been implemented: homogenous spherical head, spherical seven layer model, Specific Anthropomorphic Mannequin (SAM) phantom and HUGO human head model. On the other hand the effects of operating frequency and gap distance between the mobile phone antenna and the human head model on distributions of the SAR inside the human head are investigated. All the simulations are done for three different distances between the antenna and the head model (5 mm, 10 mm and 20 mm). Moreover, the SAR levels for the head tissues are calculated in accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP)

Organizational change and everyday health system resilience: Lessons from Cape Town, South Africa

This paper reports a study from Cape Town, South Africa, that tested an existing framework of everyday health system resilience (EHSR) in examining how a local health system responded to the chronic stress of large-scale organizational change. Over two years (2017–18), through cycles of action-learning involving local managers and researchers, the authorial team tracked the stress experienced, the response strategies implemented and their consequences. The paper considers how a set of micro-governance interventions and mid-level leadership practices supported responses to stress whilst nurturing organizational resilience capacities. Data collection involved observation, in-depth interviews and analysis of meeting minutes and secondary data. Data analysis included iterative synthesis and validation processes

Modèle de gestion de la mobilité dans les réseaux IPV6 basé sur les profils de mobilité des usagers

Mobile IPv6 -- Problèmes avec mobile IPv6 -- Hierarchical mobile IPv6 -- Fast handovers for mobile IPv6 -- Cellular IP -- Simultaneous bindings for mobile IPv6 fast handovers -- Autres travaux effectués dans le domaine -- Patron de mobilité -- Algorithmes et modèle de gestion de mobilité -- Principe de base -- Module d'apprentissage des patrons de mobilité -- Modèle de gestion de mobilité -- Description des algorithmes -- Analyse mathématique -- Implémentation du protocole proposé : seamless mobile IPv6 -- Fonctionnement du modèle de gestion de mobilité -- Synthèse des travaux -- Limitations des travaux -- Indication de travaux futurs