Este trabalho relata o processo de fotoionização associativa em átomos ultrafrios de sódio confinados por uma armadilha magneto-óptica. O comportamento da constante de reação Kpai é medido em função da intensidade dos feixes de aprisionamento, também em função da freqüência de um segundo laser. Este estudo mostrou que fotoionização ocorre em um processo de várias etapas e mostrou a importância da emissão espontânea em colisões ultrafrias. Nós confirmamos experimentalmente pela primeira vez o processo de blindagem óptica, o qual evita a interação dos átomos com a luz incidente. O entendimento deste processo é relevante se desejar-se aumentar o número e a densidade das amostras atômicas aprisionadas. / This works reports on the photo-associative ionization process in ultracold sodium atoms confined in a magneto optical trap. The behavior of the rate constant Kpai is measured as a function of the trapping beams intensity, and as a function of the frequency of a second laser. This study showed that photo-associative ionization occurs in a multi-step process and also showed the importance of spontaneous emission in ultracold collisions. We experimentally confirmed for the first time the Optical Shielding process which prevents atoms from approaching due to repulsive states induced by the interaction of the atoms with the incident light. The understanding of this process is relevant if one intends to increase the number and density of trapped atomic samples.

Neste trabalho, apresentamos uma montagem experimental capaz de aprisionar átomos de K e Rb simultaneamente em uma armadilha óptica de dipolo cruzada. Contudo, para atingir este feito foi necessário, durante o desenvolvimento do projeto, estudar cada espécie atômica de forma isolada. Assim, desenvolvemos uma técnica inédita para carregar uma armadilha de dipolo diretamente de uma armadilha magneto-óptica de 39K, constatando a importância da estrutura hiperfina do estado 4P3/2 no processo de carregamento. Também observamos e explicamos o processo de fotoassociação de Rb devido ao laser em 1071 nm, inclusive a diferença isotópica entre 85Rb e 87Rb. Na sequência, realizamos o carregamento duplo com K e Rb na armadilha e observamos a fotoassociação de KRb. Um modelo teórico simples prevê a distribuição dos níveis vibracionais obtidos. O mesmo modelo abre caminho para um possível bombeamento óptico para a produção e acúmulo de moléculas de KRb no estado X1Σ+ (v = 0). / In this paper, we present an experimental setup to simultaneously trap atoms of K and Rb in a crossed optical dipole trap. This accomplishment required the individual study of each atomic species during the project development. This allowed the development of a new technique for loading a dipole trap directly from a magneto-optical trap of 39K, providing evidence of the importance of the hyperfine structure of the state 4P3/2 in the loading process. We also observe and explain the photoassociation process of Rb2 due to the dipole trap laser at 1071 nm, including an isotopic difference between 85Rb and 87Rb. In the sequence, we performed dual species loading of K and Rb and observed the photoassociation process of KRb. A simple theoretical model predicts the final distribution of vibrational levels obtained. The same model provides a potential path to optically pump the molecules and accumulate them in the molecular ground state X1Σ+ (v = 0) for KRb.

Le cold spray, procédé qui consiste en la projection de particules de poudre à haute vitesse sur un substrat solide, permet de réaliser des dépôts denses de tantale sur substrat de cuivre. Tout au long de la projection, les particules restent à l'état solide ce qui prévient toute pollution ou modification chimique indésirable comme l'oxydation. Le risque d'altération de la composition chimique est ainsi reporté sur d'autres étapes telles l'obtention des matériaux ou la conservation des poudres. Le tantale est particulièrement sensible à la présence d'oxygène et peut ainsi voir sa dureté augmenter même pour des très faibles taux. Cette étude s'intéresse donc aux conséquences d'une augmentation du taux d'oxygène dans les particules avant projection sur la qualité (adhérence, cohésion) du dépôt. Pour cela, des particules de poudres ont été enrichies en oxygène puis ont été analysés suivant différentes méthodes (DRX, microsonde de Castaing, MET, XPS, nanoindentation, …) afin de déterminer le type d'oxydation et le comportement mécanique des particules oxydés. Ensuite, la phénoménologie des particules à l'impact a été étudiée via l'observation de particules isolées adhérant au substrat après impact (splats), d'une part, et des dépôts, d'autre part. Les techniques d'analyses et les procédés utilisés pour caractériser leur déformation et leur adhérence sont le MEB, le MET, l'EBSD, un essai de rayure modifié, la structuration laser et un essai d'adhérence et de cohésion par choc laser (LASAT®). Enfin, une simulation numérique de la construction de dépôt a été réalisée selon les lois ensemblistes établies par la morphologie mathématique. L'influence de l'oxydation des poudres est représentée dans ce modèle via l'introduction du rebond des particules. / Cold gas dynamic process, namely Cold Spray, can be used to achieve fully-dense tantalum coatings onto a copper substrate due to spraying of powder particles at a high velocity. During spraying, the particles stay at the solid state, which prevents pollution and detrimental chemical modification such as oxidation. The risk for chemical damage therefore moves to other processing stages, primarily raw material production and powder storage. Tantalum is very sensitive to oxygen (for example, hardness increases even for low oxygen contents). In the present work, the consequences of the particle oxygen degree on coating quality are studied. Oxidized powder particles were analyzed using different methods (XRD, EPMA, TEM, XPS, nanoindentation, …) to characterize oxidation and particle mechanical properties. Particle impact phenomenology is studied from observation of splats, i.e. single deposited particles, and coatings. Analysis techniques and processes to describe splat deformation and adhesion are SEM, TEM, EBSD, modified scratch testing, laser structuring and LAser Shock Adhesion Test (LASAT®). In a final part, numerical simulation of coating build-up was developed using a mathematical morphology approach. Particle oxidation is involved in this simulation through the particle rebound phenomenon.

Le principe du procédé cold spray réside dans la projection de poudres à haute vitesse sur un matériau, le substrat. La formation d'un revêtement plus ou moins dense à sa surface passe par l'adhérence et l'empilement des particules projetées. Un des domaines d'application d'un tel procédé est la réparation de composants métalliques ou composites utilisés dans le secteur aéronautique. Les particules et le substrat adhèrent par différents mécanismes, notamment mécaniques. Les duretés respectives des matériaux et la topographie de surface du substrat influent sur l'intensité de cet ancrage mécanique. Cette étude permet de statuer sur ces deux contributions. Pour cela, des systèmes purement métalliques et composites aux propriétés mécaniques différentes sont choisis. Le dépôt de particules sur des surfaces rugueuses est étudié à travers l'élaboration de revêtements d'aluminium pur sur substrats d'alliage d'aluminium plus durs. Des mécanismes de déformation plastique et d'empilement sont analysés par construction de revêtements d'Al-SiC sur aluminium. L'élaboration de ces revêtements passe par l'optimisation de nombreux paramètres liés au procédé et à la nature des matériaux (température, pression, granulométrie). Les conditions d'impact des particules sont également déterminées par l'emploi de techniques mesurant la vitesse des poudres projetées (DPV 2000), la température du substrat par thermocouples et la température des particules par simulation numérique. L'ancrage mécanique des particules est analysé par observation en coupe de l'interface revêtement-substrat. Le gradient de dureté est également quantifié. Une analyse de la morphologie des surfaces sablées est réalisée afin de corréler la granulométrie des particules aux dimensions de rugosité mesurées. Un modèle d'impact par simulation numérique est mis en place pour étudier les déformations plastiques des interfaces en fonction de la topographie de surface. Enfin, des essais d'adhérence par choc laser (LASAT®) sont entrepris afin d'identifier le rôle de la rugosité d'interface sur les seuils de rupture déterminés numériquement. / The cold spray process is based on high-speed spraying of a powder onto a substrate. The formation of a more or less dense coating depends on sprayed particle adhesion and coating build-up. The repair of metallic or composite aircraft / aerospace components is a recent application of cold spraying. The particle-substrate bond strength is due to various mechanisms, including mechanical anchoring. Substrate material hardness and surface topography governs the degree of mechanical anchoring. This thesis study is centered on the influence of these two contributions. Pure metallic and composite systems with different mechanical properties are selected. Particle deposition onto rough surfaces is investigated through the development of pure aluminium coating of harder aluminum alloy substrates. Plastic deformation and build-up mechanisms are studied for Al-SiC coatings onto ductile substrate. All the coatings resulted from an optimization stage where process parameters and materials properties are considered (gas temperature, gas pressure, particle size). Particle impact conditions are also determined by particle speed experimental measurements (using a DPV 2000 system). Substrate temperatures are determined using thermocouple and particle temperatures are studied by numerical simulation. Mechanical anchoring of particles is investigated by cross-section observation of the coating-substrate interface. Hardness gradient is also quantified. An analysis of sand-blasted surfaces morphology is performed to correlate particle size and roughness parameters. A model of particle impact is established from a finite element analysis of interface plastic deformation as a function of surface topography. Lastly, dynamic adhesion testing using a laser shock (LASAT®) are undertaken to study the potential role of interface roughness on the fracture thresholds in the light of a numerical analysis.

The Swedish civil defense during the Cold War Era was a well-developed and well-planned organization in comparison to many other countries. This caused civil defense ideas to come closer to individual citizens’ everyday lives and influence how they should adapt to the threat of nuclear war, thus creating a culture of civil defense. The purpose of this thesis is to elucidate what this militarization of everyday life looked like in Sweden during the Cold War and how it affected people’s everyday life. This is done through studying a civil defense journal between 1945-1975. The articles in the journal are analyzed by how they are portraying the day-to-day life in the context of civil defense. Partly through articles about propaganda and various civil defense courses and exercises, and partly through articles portraying the physical militarization of society, primarily fallout shelters and bunkers. Of particular interest is the contrast between the dark Cold War narrative and the narrative concerning the security and comfort provided by the welfare state. Finally, the thesis argues that the journal and its work can be seen in the context of militarization of everyday life. It tried to spread its militarizing vision in society, and did – incomparison to other countries – succeed in that pursuit. Militarization played a vital role in reaching out to the public, and in disseminating the idea of a welfare state that takes good care of its citizens, even during the hardest of times.

The purpose of this study was to measure flexibility at the hip joint under four techniques of stretching, passive stretch-concentric contraction-passive stretch (PCP), passive stretch-three seconds isometric contraction of hip extensorsconcentric contraction of hip flexors-passive stretch (3-PIeCP) and passive stretch-three seconds isometric contraction of hip flexors-concentric contraction of hip flexorspassive stretch (3-PIfCP) based on proprioceptive neuromuscular facilitation (PNF) and passive static stretch (P). Further, this study was designed to ascertain the effect of cold application (ice) in joint range of motion of the hip extensors measured with the Leighton Flexometer.

Abstract The purpose of the study was to examine the amount of cold exposure and factors affecting it at the population level in Finland, to determine what type of cold acclimatisation, if any, develops in urban residents in winter, and to find out whether cold acclimatisation or acclimation has a functional significance on psychological or physical performance. Tasks of low physical activity requiring attention and concentration (cognition, postural control) were assessed in cold. In a cross-sectional population study Finns aged from 25 to 74 years (n=6,951) were queried of their wintertime outdoor exposure duration and factors affecting it. In experimental studies seasonal cold acclimatisation (thermal responses) and its effect on cognition were assessed in the laboratory, where 15 young urban subjects were exposed to cold in winter and summer in bright or dim light. A controlled cold acclimation trial (n=10) was performed to study the effects of repeated exposures to cold on cognitive performance and postural control in young urban subjects. In the Finnish population the average amount of cold exposure in winter represents 4% of the total time. Most of the cold exposure occurs during leisure time and in outdoor occupations (agriculture, forestry, mining, industry, construction). Factors explaining increased occupational cold exposure were: occupation, age and a lesser amount of education. Factors associated with more leisure-time cold exposure were: being employed in outdoor occupations, being a pensioner, housewife, unemployed, practising physical exercise, and reporting at least average health. The experimental studies showed seasonal differences and aggravated thermal responses in urban residents in winter, but did not detect habituation responses typical of cold acclimatisation. In both seasons, acute moderate cold exposure resulted in positive, negative or mixed effects on cognition, reflected as changes in response times and accuracy. Simple cognitive tasks were impaired in cold, and in complex tasks both negative, positive and mixed effects were observed. It is suggested that cold exposure affects cognition through different mechanisms related to either distraction or arousal. Cold exposure increased postural sway by 70-90%, suggesting impaired postural control. Repeated exposures to moderate cold, reducing stress and discomfort and dampening physiological responses, did not markedly affect cognitive performance or postural control.

abstract: ABSTRACT The cold and the flu are two of the most prevalent diseases in the world. Many over the counter (OTC) medications have been created to combat the symptoms of these illnesses. Some medications take a holistic approach by claiming to alleviate a wide range of symptoms, while others target a specific symptom. As these medications become more ubiquitous within the United State of America (USA), consumers form associations and mental models about the cold/flu field. The goal of Study 1 was to build a Pathfinder network based on the associations consumers make between cold/flu symptoms and medications. 100 participants, 18 years or older, fluent in English, and residing in the USA, completed a survey about the relatedness of cold/flu symptoms to OTC medications. They rated the relatedness on a scale of 1 (highly unrelated) to 7 (highly related) and those rankings were used to build a Pathfinder network that represented the average of those associations. Study 2 was conducted to validate the Pathfinder network. A different set of 90 participants with the same restrictions as those in Study 1 completed a matching associations test. They were prompted to match symptoms and medications they associated closely with each other. Results showered a significant negative correlation between the geodetic distance (the number of links between objects in the Pathfinder network) separating symptoms and medications and frequency of pairing symptoms with medication. This provides evidence of the validity of the Pathfinder network. It was also seen that, higher the relatedness rating between symptoms and medications in Study 1, higher the frequency of pairing symptom to medication in Study 2, and the more directly linked those symptoms and medications were in the Pathfinder network. This network can inform pharmaceutical companies about which symptoms they most closely associate with, who their competitors are, what symptoms they can dominate, and how to market their medications more effectively. / Dissertation/Thesis / Masters Thesis Engineering 2020

The main objective of this research is to extend the “Direct strength method” for determining the web crippling strength of cold-formed steel C and Z sections subjected to End one flange loading and Interior one flange loading conditions. Direct strength method is applied for designing the columns and beams earlier. The existing specifications equation for calculating the web crippling strength of cold-formed steels designed by American Institute of Iron and Steel is very old method and it is based on the extensive experimental investigations conducted at different universities. Calculating the web crippling strength of cold-formed steels using direct strength method is a new technique. In the present research the web crippling strength of cold-formed steels were calculated using Direct Strength Method. The experimental data is collected from the tests that were conducted at different universities. The critical buckling strength of the members were calculated using Abaqus. Microsoft excel is used to generate the equations. The safety and resistance factors for the designed equations were calculated using “Load and resistance factor design” and “Allowable strength design” from North American Cold-Formed Steel Specification, 2012 edition book.

No description available.