La décrépitation (fracturation) des matériaux actifs de batteries associée à leur variation volumique lors des cycles de charge/décharge a pour effet d'accélérer leur corrosion par l'électrolyte et/ou d'induire une perte de connectivité électronique au sein de l'électrode ce qui réduit notablement leur durée de vie. C’est particulièrement le cas des hydrures métalliques utilisés dans les batteries Ni-MH. À ce jour, l'évaluation de leur fracturation se limite généralement à une observation post mortem des électrodes par microscopie ce qui ne permet pas une analyse détaillée du processus de décrépitation. À ce titre, un de nos principaux objectifs dans le cadre de ce travail de recherche a été de développer une méthode d'analyse novatrice et performante basée sur l'émission acoustique (EA) afin d'étudier in situ la fracturation d'électrodes négatives pour batteries Ni-MH. Dans une première étape, nous avons analysé en détail les signaux acoustiques produits lors de la charge (hydruration) d'un alliage commerciale à base de LaNi5 et d'un alliage MgNi obtenu par broyage mécanique. Nous avons ainsi pu séparer les signaux générés par la fracturation des particules d’hydrures métalliques de ceux associés à la formation de bulles de H2, ce qui a permis d’établir les mécanismes qui régissent leur fracturation. Par la suite, un montage expérimental, constitué d’une cellule électrochimique connectée à un capteur de force en compression et d’un équipement d’EA, a été mis point pour suivre in-situ la fracturation et la force générée par l’expansion/contraction lors du cyclage des électrodes MgNi et LaNi5. Nous avons ainsi pu confirmer que l’expansion/contraction volumique de l’alliage MgNi est plus progressif que pour l’alliage à base de LaNi5. Par la suite, l’étude comparée par EA des alliages MgNi, Mg0.9Ti0.1Ni et Mg0.9Ti0.1NiAl0.05 a permis de mettre en évidence l'influence de leur composition sur leur résistance à la pulvérisation. Finalement, nous avons étudié en détail l’influence de l’addition de palladium dans l’alliage Mg0.9Ti0.1NiAl0.05 sur son comportement électrochimique et sa résistance à la fracturation. / The pulverization (cracking) of active materials in batteries, induced by their volume change during charge/discharge cycles, accentuates their corrosion by the electrolyte and/or leads to a loss of electronic connectivity within the electrode, which notably reduces their cycle life. This particularly occurs for metallic hydrides used in Ni-MH batteries. To date, the evaluation of their cracking is generally limited to post mortem observations of the electrodes by microscopy, which does not allow for a detailed analysis of the decrepitation process. In this respect, one of our main research objectives was to develop an innovative and efficient analysis method based on acoustic emission (AE) for in situ monitoring of the cracking of negative electrodes for Ni-MH batteries. As a first step, a detailed analysis of the acoustic signals generated during the charge (hydriding) of a commercial LaNi5-based alloy and a MgNi alloy obtained by mechanical alloying was performed. This allowed separating the signals generated by the cracking of the metallic hydride particles from those induced by the formation of H2 bubbles. We have shown that the mechanism which governs the pulverization of the MgNi alloy remarkably differs from that of the LaNi5-based alloy. In a second step, an experimental set-up made of an electrochemical cell linked to a compression force cell and an AE equipment was elaborated, in order to monitor concomitantly the cracking and the force generated by the expansion/contraction of the MgNi and LaNi5 during cycling. We have thereby been able to confirm that the volume expansion/contraction of the MgNi alloy is more progressive than that of the LaNi5 alloy. The AE-based comparative study of MgNi, Mg0.9Ti0.1NiAl5 and Mg0.9Ti0.1NiAl0.05 alloys then allowed demonstrating the positive effect of the partial Mg substitution by Ti and adding of Al on the alloy decrepitation resistance. As a final step, we have studied the impact of palladium addition in the Mg0.9Ti0.1NiAl0.05 alloy on its electrochemical behaviour and cracking resistance.

Afin d'améliorer la compréhension de la corrosion atmosphérique des bronzes, nous avons mis en oeuvre : - La caractérisation des composés d'étain, susceptibles d'être formés en corrosion atmosphérique, par une approche multi-analytique, la spectroscopie Mössbauer joue un rôle central (analyse sélective et quantitative). Les paramètres hyperfins et les facteurs Lamb-Mössbauer de plusieurs oxydes, sulfates et chlorures d'étain ont été déterminés. Les facteurs f sont dispersés et dépendants de température, montrant la nécessité de l'analyse à basse température. - Le développement d'un détecteur CEMS associant basse température et analyse non-destructive de surface : le dispositif a été mis en point entre 41 et 300 K. Les principaux paramètres affectant ses performances ont été étudiés et optimisés. - La réalisation d'une campagne d'exposition de 2 ans en site urbain de CuSn9, CuSn3Zn9, CuZn33 et leurs métaux purs. Les vitesses de corrosion ont été déterminées ainsi que les quantités de métaux entraînés par les eaux de pluie du fait de la solubilisation des produits de corrosion.

Afin d'améliorer l'adhérence des chaussées, il est nécessaire d'accéder à une caractérisation de leur état de surface tant à l'échelle des granulats (macrotexture) que de leur rugosité locale (microtexture). Or, à ce jour, la microtexture et plus particulièrement les aspérités d'amplitude comprise entre un et quelques dizaines de micromètres, ne peut être appréhendée de manière satisfaisante par les moyens mis en œuvre en génie civil (limitation de l'étendue de mesure des profilomètres aux résolutions souhaitées). Les travaux de recherches réalisés s'inscrivent dans le cadre plus global de travaux du LCPC destinés à accéder à une meilleure compréhension de l'apport de la microtexture au frottement pneumatique/chaussée. Ils ont pour objectif l'élaboration d'une méthode de caractérisation globale de la microtexture par l'emploi des techniques du speckle, plus particulièrement dans le cas d'un speckle subjectif non résolu. Devant le peu d'informations disponibles sur l'application des techniques du speckle aux surfaces multi-échelles, des simulations du contraste de speckle dans la configuration expérimentale particulière choisie sont réalisées pour une surface comportant deux échelles de texture à l'aide du modèle de diffraction scalaire de Kirchhoff. Celles-ci démontrent la possibilité de caractériser la finesse de la microtexture ou son évolution avec l'usure par la méthode choisie. Dans un second temps, les paramètres statistiques du premier ordre du speckle (contraste, histogramme de l'intensité) sont examinés dans le cadre d'expérimentations réalisées sur des surfaces de référence (papiers abrasifs de différente finesse) et sur des modèles de surface de chaussée (différentes roches, différents stades d'usure), chaque échantillon étant étalonné par des relevés de profils. Par des traitements adaptés des images de speckle, nous parvenons à séparer les surfaces de référence et dans le cas des modèles de chaussée, deux finesses différentes et deux stades d'usure.

<p>The purpose of this thesis is to study the personal problems that can occur when defecting from a destructive cult, and what kind of support you may need from social authorities. The aim is to develop guidelines for social workers who are in contact with sect defectors. It’s a qualitative study based on interviews with six defectors from Jehovah’s witnesses. The results shows that all the defectors that have been interviewed have had anxiety problems, lost contact with friends and relatives, low level of education, and low self esteem when defecting or after. Most respondents have reported that they have had thoughts of suicide. It also occurs that respondents have had eating disorders, psychosomatic problems, drug abuse, lack of knowledge about society and have felt threatened and harassed in connection with the defection. These psychosocial problems that have been ascertained to constitute areas where social authorities should aid sect defectors. In accordance with the purpose of this thesis, guidelines are formed for social workers.</p> / <p>Syftet med undersökningen är att undersöka den personliga problematik som kan uppstå vid avhopp från en destruktiv sekt och de behov av stöd och hjälp man kan behöva ha från sociala myndigheter. Avsikten med studien är att försöka utveckla vägledande anvisningar för socialarbetare som kommer i kontakt med avhoppare. Det är en kvalitativ studie baserad på intervjuer med sex avhoppare från Jehovas vittnen. Resultatet visar att alla de avhoppare som intervjuats hade haft ångestproblematik, förlorat kontakt med vänner och familj, låg utbildningsnivå samt svag självkänsla i samband med avhoppet eller där efter. De flesta respondenterna sagt sig ha haft självmordstankar. Det förekommer även att respondenter säger sig ha haft ätstörningar, psykosomatisk problematik, narkotikamissbruk, bristande kunskap om samhället samt känt sig hotade och trakasserade i samband med avhoppet. De psykosociala problem som intervjupersonerna berättar om liknar det som tidigare studier funnit och som utgör områden där sociala myndigheter bör bistå sektavhoppare. I enlighet med syftet är slutligen vägledande anvisningar utformade för socialarbetare.</p>

<p>The aim with this study was to learn about the experiences of field workers and welfare officers in the field of possible self-harm behavior among young people.Our problem was: Do field workers and welfare officers treat young people with deliberate self-harm differently and - How do field workers and welfare officers describe deliberate self- harm?</p><p>Our study was conducted through qualitative semistructured interviews with twelve interviewee’s.The result of this study shows that there is a difference in how young people with self-harm behavior are being treated - based on their gender.One possible cause for this result could be the old tradition mindset of viewing boys and girls differently – and thus, treating them differently when they seek help.Our study shows there is a possibility of treating boys and girls differently – which shows that we made a thought-provoking point</p>

The aim with this study was to learn about the experiences of field workers and welfare officers in the field of possible self-harm behavior among young people.Our problem was: Do field workers and welfare officers treat young people with deliberate self-harm differently and - How do field workers and welfare officers describe deliberate self- harm? Our study was conducted through qualitative semistructured interviews with twelve interviewee’s.The result of this study shows that there is a difference in how young people with self-harm behavior are being treated - based on their gender.One possible cause for this result could be the old tradition mindset of viewing boys and girls differently – and thus, treating them differently when they seek help.Our study shows there is a possibility of treating boys and girls differently – which shows that we made a thought-provoking point

Fretting fatigue is a damage process that may arise in engineering applications where small cyclic relative displacements develop inside contacts leading to detrimental effects on the material fatigue properties. Fretting is located in regions not easily accessible, which makes it a dangerous phenomenon. It is therefore important to be able to make reliable predictions of the fretting fatigue lives. The work presented in this thesis has its focus on different aspects related to fretting fatigue in the titanium alloy Ti-17. A fretting experiment was developed which allowed for separate control of the three main fretting loads. Initially, the evolution of the coefficient of friction inside the slip region was investigated experimentally and analytically. Subsequently, 28 fretting tests were performed in which large fatigue cracks developed. The fretting tests were firstly evaluated with respect to fatigue crack initiation through five multiaxial fatigue criteria. The criteria predicted a too high fretting fatigue limit. A possible clue to the discrepancy was found in the fretting induced surface roughness with the asperity-pit interactions. The fatigue growth of the large fretting cracks was numerically modelled through a parametric crack growth procedure. The predicted lives were compared to the experimental outcome. The numerical simulations showed that linear elastic fracture mechanics was an appropriate tool for the prediction of fretting fatigue propagation lives in the long crack regime. Fatigue cracks spend most of their propagation life in the small crack regime. The possibility of modelling the small crack behaviour is therefore very important from the engineering point of view. The fatigue growth of through thickness short cracks was studied experimentally and numerically in the four-point bend configuration. It was found that linear elastic fracture mechanics and closure-free material growth data furnished conservative estimates for cracks longer than 50 μm. One method to improve fretting fatigue life is to shot peen the contact surfaces. Experimental results on fretting life with or without shot peening were simulated. The fatigue life enhancement in shot peened specimens could be explained by slower crack growth in the surface material layer with residual compressive stresses. / QC 20100827

Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material. A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres. The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared. / As the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Accepted. Paper 5: Manuscript. Paper 6: Submitted.

The purpose of this thesis is to study the personal problems that can occur when defecting from a destructive cult, and what kind of support you may need from social authorities. The aim is to develop guidelines for social workers who are in contact with sect defectors. It’s a qualitative study based on interviews with six defectors from Jehovah’s witnesses. The results shows that all the defectors that have been interviewed have had anxiety problems, lost contact with friends and relatives, low level of education, and low self esteem when defecting or after. Most respondents have reported that they have had thoughts of suicide. It also occurs that respondents have had eating disorders, psychosomatic problems, drug abuse, lack of knowledge about society and have felt threatened and harassed in connection with the defection. These psychosocial problems that have been ascertained to constitute areas where social authorities should aid sect defectors. In accordance with the purpose of this thesis, guidelines are formed for social workers. / Syftet med undersökningen är att undersöka den personliga problematik som kan uppstå vid avhopp från en destruktiv sekt och de behov av stöd och hjälp man kan behöva ha från sociala myndigheter. Avsikten med studien är att försöka utveckla vägledande anvisningar för socialarbetare som kommer i kontakt med avhoppare. Det är en kvalitativ studie baserad på intervjuer med sex avhoppare från Jehovas vittnen. Resultatet visar att alla de avhoppare som intervjuats hade haft ångestproblematik, förlorat kontakt med vänner och familj, låg utbildningsnivå samt svag självkänsla i samband med avhoppet eller där efter. De flesta respondenterna sagt sig ha haft självmordstankar. Det förekommer även att respondenter säger sig ha haft ätstörningar, psykosomatisk problematik, narkotikamissbruk, bristande kunskap om samhället samt känt sig hotade och trakasserade i samband med avhoppet. De psykosociala problem som intervjupersonerna berättar om liknar det som tidigare studier funnit och som utgör områden där sociala myndigheter bör bistå sektavhoppare. I enlighet med syftet är slutligen vägledande anvisningar utformade för socialarbetare.

Nondestructive testing is used extensively throughout the industry for quality assessment and detection of defects in engineering materials. The range and variety of anomalies is enormous and critical assessment of their location and size is often complicated. Depending upon final operational considerations, some of these anomalies may be critical and their detection and classification is therefore of importance. Despite the several advantages of using Nondestructive testing for flaw detection, the conventional NDT techniques based on the heuristic experience-based pattern identification methods have many drawbacks in terms of cost, length and result in erratic analysis and thus lead to discrepancies in results. The use of several statistical and soft computing techniques in the evaluation and classification operations result in the development of an automatic decision support system for defect characterization that offers the possibility of an impartial standardized performance. The present work evaluates the application of both supervised and unsupervised classification techniques for flaw detection and classification in a semi-infinite half space. Finite element models to simulate the MASW test in the presence and absence of voids were developed using the commercial package LS-DYNA. To simulate anomalies, voids of different sizes were inserted on elastic medium. Features for the discrimination of received responses were extracted in time and frequency domains by applying suitable transformations. The compact feature vector is then classified by different techniques: supervised classification (backpropagation neural network, adaptive neuro-fuzzy inference system, k-nearest neighbor classifier, linear discriminate classifier) and unsupervised classification (fuzzy c-means clustering). The classification results show that the performance of k-nearest Neighbor Classifier proved superior when compared with the other techniques with an overall accuracy of 94% in detection of presence of voids and an accuracy of 81% in determining the size of the void in the medium. The assessment of the various classifiers’ performance proved to be valuable in comparing the different techniques and establishing the applicability of simplified classification methods such as k-NN in defect characterization. The obtained classification accuracies for the detection and classification of voids are very encouraging, showing the suitability of the proposed approach to the development of a decision support system for non-destructive testing of materials for defect characterization.