The purpose of this monograph is to study the mathematical principles behind the Global Positioning System, the so-called GPS. We start with a historical approach of the evolution of this technology. Then we show some theorems in geometry: plane, spatial and analytic, which together with some physical principles (average speed, speed of light, the Doppler effect,...) guided the creators of this powerful tool that determines with remarkable accuracy the position (latitude, longitude and altitude) of a transmitter. Finally, we suggest activities to be performed at the level of basic education, to stimulate students curiosity by scientific knowledge contained therein. / A presente monografia tem como objetivo evidenciar os princípios matemáticos por trás do funcionamento do Sistema de Posicionamento Global conhecido por GPS. Após uma abordagem geral da evolução ocorrida até chegarmos a essa tecnologia, demonstraremos alguns teoremas das geometrias: plana, espacial e analítica que, aplicados juntamente com alguns princípios da Física (velocidade média, velocidade da luz, efeito Doppler,...), nortearam os criadores desta poderosa ferramenta que determina com notáveis precisão e exatidão, em qualquer parte do globo terrestre incluindo a atmosfera, a hora e a posição (latitude, longitude e altitude) de um transmissor. E, a partir daí, sugerir atividades interdisciplinares, a serem desenvolvidas em nível de educação básica, que estimulem a curiosidade dos alunos pelos conhecimentos científicos nelas contidos.

De manière générale, avoir un emploi est un élément de satisfaction pour la plupart des personnes. En revanche, beaucoup de salariés sont sujets au stress, ce qui a une incidence non négligeable à la fois sur les individus et sur les structures. Ces dernières ne possèdent souvent pas de modèles appropriés pour évaluer de manière approfondie ce phénomène. Le manque de connaissances précises du stress au travail, et de ses origines, particulièrement les deux dimensions du statut personnel et le statut professionnel en France, nous a conduits à réaliser un diagnostic approfondi pendant plusieurs années au sein d’une grande entreprise industrielle sur plusieurs sites. L’entreprise choisie est emblématique de l’organisation du travail industriel en France. La cartographie du stress au travail, avec l’identification des populations principalement exposées, devrait être applicable à d’autres organisations afin de définir rapidement un plan d’actions anti-stress, sans avoir à réaliser préalablement un état des lieux détaillé ; pour le plus grand bénéfice des salariés, de l’ambiance de travail et de la production. Les différentes parties prenantes au déploiement d’une politique contre le stress, à savoir : les salariés, l’encadrement, les directions des ressources humaines, les psychologues du travail, les médecins du travail ont été sollicités dans le cadre de cette recherche.Après un diagnostic général, face au grand nombre de thèmes de recherches possibles et du fait de l’insuffisance d’études sur la relation entre le statut personnel et la situation de travail avec les autres facteurs déjà intégrés aux modèles classiques sur le stress au travail, nous nous sommes concentrés sur ce sujet en définissant un modèle théorique à valider expérimentalement au travers de questionnaires. Dans la recherche présente, nous expliquons comment nous avons constaté que, parmi les facteurs liés au stress professionnel, la catégorie « situation de travail » influence plus ce phénomène que la catégorie « statut personnel ». Parmi les facteurs présents dans la catégorie « situation de travail », les plus importants par ordre décroissant sont : la catégorie socioprofessionnelle, la pratique de l’anglais, et l’ancienneté. Parmi les facteurs présents dans la catégorie « statut personnel », les plus importants par ordre décroissant sont : le niveau de formation, le genre et l’âge. Ce constat est plutôt une bonne nouvelle pour les entreprises, car elles pourront diminuer le stress au travail en agissant sur la situation de travail, sachant qu’elles ne peuvent intervenir sur le statut personnel des salariés. Cette contribution devra être complétée par d’autres recherches afin de renforcer l’exhaustivité du diagnostic sur le stress au travail et de conduire des plans d’action complets couvrant tous les thèmes. / In general, having a job is a satisfactory factor for the majority of persons. However, most of the employees are stress-prone, which has an important effect both on individuals and on structures. Those structures often do not possess relevant standards to thoroughly evaluate this phenomenon.The lack of precise knowledge about stress at work and its origins, especially the two dimensions of personal status and professional status in France, has led us to conduct a thorough diagnosis for several years on several plants of a large industrial company. The chosen company is emblematic of the industrial labour organization in France. The mapping of stress at work, with the identification of mainly exposed populations, should be applicable to other organizations to quickly set an anti-stress action plan, without first making a detailed inventory; for the greatest benefit of employees and the work environment and production. The different stakeholders interested in deploying a policy against stress, the employees, the hierarchy, Human Resources Departments, occupational psychologists, occupational doctors have been solicited as part of this research. After a general diagnosis, facing the large number of possible research topics and because of the lack of studies on the relationship between staff’s personal status and "professional situation" with the other factors already integrated within conventional models about stress at work, we focused on this issue by defining a theoretical model to be validated experimentally through questionnaires. In this research we explain how we found that among the factors related to stress at work, the category "professional situation" influenced this phenomenon more than the "personal status" category.Among the factors in the category "professional situation", the most important in decreasing order are: socio-professional category, English practice, and seniority. Among the factors in the "personal status" category, the most important in decreasing order are: the level of education, gender and age. This finding is rather good news for companies because they will be able to reduce stress at work by acting on the "professional situation", knowing that they cannot interfere with the personal status of employees. This contribution should be supplemented by other researches to enhance the completeness of the diagnosis about stress at work and to conduct complete actions plans covering all topics.

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Denna kvalitativa studie syftade till att undersöka två skolors verksamheter utifrån begreppet flexibilitet. Skolpersonal intervjuades med hjälp av sex semistrukturerade intervjuer om sina upplevelser av möjligt handlingsutrymme, samt bredd och variation av arbetsuppgifter. Studiens syfte var att ta reda på vilka lärprocesser och kompetenser som utvecklades för att hantera kravet på flexibilitet. Resultatet visade att skolpersonals arbete var oförutsägbart, föränderligt, varierande och kravfyllt från olika håll. Respondenterna fick utföra fler arbetsuppgifter av administrativ karaktär idag och deras yrkesroller har blivit komplexa och breddade. Många arbetade på sin fritid för att känna att de "hann med" arbetet. Upplevelsen var att organisationen inte var flexibel, men att den förväntade sig att medarbetarna var flexibla och att de arbetade för att nå målen med begränsat handlingsutrymme. Respondenterna menade att det krävs en större samverkan mellan utbildning och arbetsliv så att utbildningarna blir mer verklighetsförankrade och uppdaterade. Kollegor i form av arbetslag, tillsammans med erfarenhet, verkade vara det viktigaste för att uppleva hanterbarhet kring kraven på flexibilitet. Lärare upplevde, i större utsträckning än övrig personal, ett större handlingsutrymme och mer tid i arbetslaget. De hade därmed större möjlighet till utvecklingsinriktat lärande och kompetens som utveckling, snarare än anpassning. Andra yrkesgrupper menade att planeringstid och delaktighet i arbetslag krävs i större utsträckning för kompetensutveckling och utvecklingsinriktat lärande. Resultatet av denna studie visar likheter med tidigare forskning, men att det också finns behov av lärande – och kompetensutvecklingsstrategier kring komplexa arbeten, och hur skolpersonals yrken ska hanteras på ett sätt som är stärkande för professionen. Denna studie skulle kunna vara ett bidrag till underlag för en sådan forskning. / This qualitative study aimed to examine the organization of two schools by the term flexibility. School personnel was interviewed, using six semi-structured interviews, about their experiences of possible latitude and the breadth and variety of tasks. The study's purpose was to find out which learning processes and competences developed to cope with the requirement for flexibility. The study showed that school personnel work was unpredictable, changeable, diverse and demanding from different directions. The respondents had more tasks of an administrative nature nowadays and their professional roles have become complex and broadened. Many worked in their spare time to feel they "catch up" on work. It was felt that the organization wasn't flexible, but that it expected that employees were flexible and worked to achieve the goals with limited latitude. Respondents believed that a greater synergy between education and employment was required, so that the programs are more reality-based and updated.Colleagues, along with experience, appeared to be the most important to manage the requirements for flexibility. Teachers experienced, to a greater extent than other employees, more freedom and more time with colleagues and thus had greater opportunities for development-oriented learning and competence development, rather than adaptation-oriented learning. Other professionals believe that planning time and involvement in work teams is required to a greater extent for competence and learning development. This study has some similarities to earlier research, but it also shows that there is a need for more research in this area. There is a need for learning - and skills development strategies for complex jobs and how they should be managed in an empowering way. My study could be a contribution to a basis for such research.

La possibilité pour les employés de participer aux décisions qui les concernent a une incidence sur leur santé psychologique au travail. Les comportements de mobilisation adoptés par les gestionnaires envers les employés ont également une influence sur la santé psychologique au travail de ces derniers. Loin d'être simple à développer, la compétence à mobiliser nécessite pour l'individu de modifier ses façons de penser, ses représentations et ses comportements : des aspects profonds de l'identité. Ce type de transformation est toutefois facilité par une réflexion sur son propre comportement et ses propres actions.La démarche d'apprentissage dans l'action expérimentée dans cette thèse s'inscrit dans le cadre d'une recherche-intervention visant à aider trois gestionnaires d'un centre hospitalier, à adopter de nouveaux comportements favorisant la mobilisation, à partir de leur action d'animation de réunions éclair avec les employés. Elle cherche à concilier le besoin de formation des gestionnaires avec un contexte de travail où le temps disponible pour la formation est restreint, compte tenu de la continuité des services à offrir, de la charge de travail élevée et de la pénurie de personnel. Le cadre d'intervention a la particularité d'être à la fois une situation de perfectionnement et un contexte d'exploration, dans lequel la chercheure agit également à titre de facilitatrice. L'action d'animation des réunions éclairs sert de point d'ancrage à la période de réflexion-sur-l'action, qui permet aux gestionnaires d'examiner leur action et d'apprendre de nouvelles stratégies d'animation plus mobilisatrices. Plusieurs types de données sont recueillies : observations des réunions éclair, enregistrements des sessions individuelles avec chacun des gestionnaires (période de réflexion-sur-l'action), des rencontres avec les trois gestionnaires et des entrevues de groupe ou individuelles avec les employés. Le traitement des données, à partir de l'analyse thématique, permet de construire des arbres thématiques et de reconstituer trois récits de leur expérience. Les récits donnent accès à la description de trois situations distinctes. Les résultats sont modestes, mais démontrent que pour un des trois gestionnaires, la démarche est concluante. Elle lui permet d'adopter de nouveaux comportements à mobiliser : un plus grand niveau d'écoute et une lucidité accrue en réunion quant aux réactions des employés et quant à l'impact de ses interventions sur le niveau de la mobilisation des employés ainsi qu'une capacité nouvelle à s'autoréguler dans l'action afin d'utiliser des stratégies plus mobilisatrices. L'analyse met en lumière deux facteurs qui favorisent l'adoption de comportements à mobiliser. Premièrement, il doit y avoir un cadre et un contexte qui permettent d'apprendre à partir de l'action, incluant l'accompagnement d'un facilitateur capable à la fois de soutenir et de confronter le gestionnaire. Le facilitateur doit privilégier des interventions favorisant la responsabilisation du gestionnaire dans le choix de ses stratégies d'animation et le maintenant centré sur son action. À cet effet, le Test personnel d'efficacité s'avère être un outil efficace. Deuxièmement, il faut tenir compte des facteurs individuels propres aux gestionnaires participant à ce type de démarche d'apprentissage dans l'action.

L’influence des dirigeants sur la performance (ou contre-performance) de la firme fait l’objet de nombreux débats. Selon la vision déterministe, les pressions internes et externes qui s’exercent sur le dirigeant sont si importantes que ce dernier dispose de très peu de marge de manoeuvre pour influencer les résultats de la firme. D’un autre côté, selon les partisans de l’école du leadership, le dirigeant est l’unique architecte de l’entreprise et c’est à lui qu’incombe la performance de l’entreprise. Ces deux points de vue sont nuancés par le concept de latitude managériale qui mesure la marge de manoeuvre dont le dirigeant qui lui permet de se démarquer significativement des autres entreprises du secteur. Cette thèse s’intéresse à la responsabilité du dirigeant sur la performance de la firme ainsi que sur les décisions qui y sont opérées. Elle porte sur les grands patrons français qui ont, notamment, la particularité de former de puissants réseaux sociaux. Le premier chapitre dresse un portrait des grands dirigeants français et met en évidence les principales caractéristiques des décideurs hexagonaux. Le deuxième chapitre étudie le phénomène d’endogamie observé lors des successions de dirigeants ainsi que l’impact sur la performance de la firme. Le troisième chapitre propose une évaluation de l’effet du dirigeant sur la performance de la firme. Enfin le quatrième chapitre mesure l’impact du pouvoir du dirigeant sur les décisions de de croissance externe de la firme. Cette thèse corrobore l’idée que le pouvoir économique demeure au sein d’une castedirigeante fermée / CEO effect on firm performance (or non-performance) is the point of many debates. According to the deterministic view, the CEO is constrained by internal and external forces and has no enough latitude for influence significantly the firm out comes. Other side, the leadership school considers that the CEO is the only one designer of the firm and is the responsible of the firm performance.These views are qualified by the managerial discretion which measures the margin flexibility theCEO has in order to make decisions to, significantly, differentiate the firm from others within a same sector. This thesis focuses on the CEO’s effect on the firm performance and the decisions that are operated in the firm. It deals with the major French CEOs who have the particularity to build powerful social networks. Chapter 1 is about the major French CEOs and draws the main features of these deciders. The phenomen on of endogamy observed during CEO succession and its impact on the firm performance are studied in Chapter 2. Chapter 3 offers an evaluation of the CEO’s impact on the firm performance and Chapter 4 measures the CEO’s power on decision about the acquisitions. This thesis confirms the idea that the economic power remains inside a closed executive cast

La thèse cherche à comprendre la marge de manœuvre des dirigeants mandataires sociaux pour l’engagement stratégique socialement responsable des entreprises françaises cotées. Notre cadre théorique se définit autour des approches financières et stratégiques de la latitude managériale des dirigeants dans une vision synthétique des théories contractuelles et cognitives de la gouvernance.Nous adoptons une démarche d’exploration hybride alternant logique abductive et déductive. Un design multi-méthodes est mobilisé : entretiens, tests statistiques et étude de cas unique. Nos résultats montrent la prudence des dirigeants d’entreprises françaises cotées concernant leur engagement dans la RSE (Responsabilité Sociale de l’Entreprise) à titre individuel. Ils ne s’engageraient que dans le cas de pratiques proactives de leurs entreprises ou dans le cas de l’atteinte d’une performance financière conséquente. Une importante logique de légitimation de ces acteurs est révélée.Concernant l’influence des dirigeants sur l’engagement dans RSE de leurs entreprises, leur ancienneté en poste y serait positivement associée. Le renforcement de la capacité des dirigeants à percevoir et à répondre à la demande sociale tout au long de leur mandat peut expliquer ce résultat. Les dirigeants rechercheraient aussi leur enracinement à travers la RSE. Celui-ci pourrait être favorable à la performance de long terme des entreprises notamment celles témoignant de systèmes de gouvernance très financiarisés. Pour éviter des dérives personnelles dommageables, nos résultats montrent que l’autonomie acquise par les dirigeants par leur ancienneté se devrait d’être contrebalancée par des mécanismes de contrôle.Nos résultats insistent sur le rôle actif et positif potentiellement endossable par les dirigeants pour le repérage et l’intégration stratégique d’opportunités liées à la RSE dans le cadre d’une création de valeur partenariale / The research aims to understand top managers’ discretion for the strategic commitment of French listed companies to Corporate Social Responsibility (CSR). Our theoretical framework is based on the financial and strategic views of managerial discretion. Our approach simultaneously considers the contractual and cognitive approaches of corporate governance.We conducted an exploratory study based on both abductive and deductive reasoning. A multi-method design is developed and includes interviews, statistical tests and a case study.Our results show the top managers’ caution to be personally committed to CSR. Looking for legitimization, they would only be socially committed when their companies had demonstrated a strong positioning in this field or when they have reached a sufficient financial performance. Top management team’s tenure also appears positively linked to the company’s CSR strategic commitment at an organizational level. Indeed, top managers’ tenure contributes to develop their capabilities to perceive and to answer stakeholders’ expectations. Top managers may also have the possibility, year after year, to seek for their entrenchment through CSR. This managerial entrenchment could be positive for the long term performance of companies characterized by a strongly short-term oriented governance system. To avoid top managers’ personal abuses of their autonomy, control mechanisms may also have to be implemented in the same time.Our results underline the critical but fundamental role of top managers to identify and integrate CSR strategic opportunities for creating shared value

Thesis advisor: Prof. Michael J. Naughton / Thesis advisor: Dr. Cesar E. Valladares / The equatorial and low-latitude ionosphere of the Earth exhibits unique features on its structuring, coupling, and electrodynamics that offer the possibility to forecast the dynamics and fluctuations of ionospheric plasma densities at later times. The scientific understanding and forecasting of ionospheric plasma are necessary for several practical applications, such as for mitigating the adverse effects of space weather on communication, navigation, power grids, space mission, and for various scientific experiments and applications. The daytime equatorial electrojet (EEJ), equatorial ionization anomaly (EIA), as well as nighttime equatorial plasma bubble (EPB) and plasma blobs are the most prominent low-latitude ionospheric phenomena. This dissertation focuses on the multi-diagnostic study of the mechanism, properties, abnormalities, and interrelationships of these phenomena to provide significant contributions to space weather communities from the ground- and space-based measurements. A strong longitudinal, seasonal, day-to-day variability and dependency between EEJ, ExB vertical plasma drift, and total electron content (TEC) in the EIA distribution are seen in the equatorial and low-latitude region. In general, the EEJ strength is stronger in the west coast of South America than in its east coast. The variability of the EEJ in the dayside ionosphere significantly affects the ionospheric electron density variation, dynamics of the peak height of F2-layer, and TEC distributions as the EEJ influences the vertical transport mechanism of the ionospheric plasma. The eastward electric field (EEF) and the neutral wind play a decisive role in controlling the actual configuration of the EIA. The trans-equatorial neutral wind profile calculated using data from the Second-generation, Optimized, Fabry-Perot Doppler Imager (SOFDI) located near the geomagnetic equator and a physics-based numerical model, LLIONS (Low-Latitude IONospheric Sector) give new perspectives on the effects of daytime meridional neutral winds on the consequent evolution of the asymmetry of the equatorial TEC anomalies during the afternoon onwards. The spatial configurations including the strength, shape, amplitude and latitudinal extension of the EIA crests are affected by the EEF associated with the EEJ under undisturbed conditions, whereas the meridional neutral winds play a significant role in the development of their asymmetric structure in the low-latitude ionosphere. Additionally, the SWARM satellite constellation and the ground-based LISN (Low-Latitude Ionospheric Sensor Network) data allow us to resolve the space-time ambiguity of past single-satellite studies and detect the drastic changes that EPBs and plasma blobs undergo on a short time scale. The coordinated quantitative analysis of a plasma density observation shows evidence of the association of plasma blobs with EPBs via an appropriate geomagnetic flux tube. Plasma blobs were initially associated with the EPBs and remained at the equatorial latitude right above the EPBs height, but later were pushed away from geomagnetic equator towards EIA latitudes by the EPB/ depleted flux tubes that grew in volume. Further, there exists a strong correlation between the noontime equatorial electrojet and the GPS-derived TEC distributions during the afternoon time period, caused by vertical E × B drift via the fountain effect. Nevertheless, only a minor correlation likely exists between the peak EEJ and the net postsunset ionospheric scintillation index (S4) greater than 0.2. This study not only searches for a mutual relationship between the midday, afternoon and nighttime ionospheric phenomena but also aims at providing a possible route to improve our space weather forecasting capability by predicting nighttime ionospheric irregularities based on midday measurements at the equatorial and low latitudes. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Electron density irregularities influence Global Navigation Satellite System (GNSS) signals, manifesting as ionospheric scintillation. Scintillation poses a service risk to safety-critical GNSS applications at high latitudes. It is difficult to predict, as ionospheric instability processes are not yet fully characterised. This research combines the fields of ionospheric imaging and scintillation monitoring, to investigate the causes of scintillation in the Antarctic and Arctic. Results revealed a plasma patch structure above Antarctica, in response to the impact of a solar wind shock front. Measurements from a network of Global Positioning System scintillation receivers across the continent revealed moderate levels of phase scintillation associated with Total Electron Content (TEC) gradients at the patch break-off point. Scintillation was also driven by solar particle precipitation at E and F region altitudes, verified with in situ spectrometers on polar-orbiting satellites. The current receiver coverage in the region provided the Multi-Instrument Data Analysis Software (MIDAS) tomography tool with sufficient data to track the lifetime of the plasma patch without a convection model. A second experiment was performed at the South Pole, using a collocated GPS scintillation receiver and auroral imager. This allowed simultaneous line-of-sight tracking of GPS signals through the optical auroral emissions. Results showed the first statistical evidence that auroral emissions can be used a proxy for ionospheric irregularities causing GPS scintillation. The relationship was strongest during the presence of discrete auroral arcs. Correlation levels of up to 74% were found over periods of 2-3 hours. The use of multiple emission wavelengths provided basic altitude discrimination. Current capability of ionospheric TEC mapping in the Arctic was tested, where GPS receiver distribution is extensive compared to present Antarctic coverage. Analysis of the ionosphere’s response to a storm event revealed a sequential picture of polar cap patch activity, without the aid of plasma convection modelling. The electron density enhancements of the auroral oval were imaged in completeness for the first time using GPS tomography. Reconstructions were verified using ultraviolet auroral imagery from polar-orbit satellites, and vertical profiles from an incoherent scatter radar.

For decades scientists believed that herbivory had minimal impact on freshwater ecosystems. We now know that herbivory in freshwater systems equals or exceeds herbivory in terrestrial and marine systems. In extreme cases, herbivores can change clear, macrophyte dominated ecosystems into turbid plankton dominated ecosystems. Even though research on plant-herbivore interactions in freshwater systems has increased, there is still much that is unknown. This thesis is comprised of four studies investigating freshwater plant-herbivore interactions across multiple spatial scales. The first study investigated how induced chemical defenses in Cabomba caroliniana suppress herbivore consumption and growth as well as how this herbivore-generated change in plant chemistry affects the growth of plant associated microbes. At the spatial scale of individual ponds or lakes, consumers that induce their host plants may also be indirectly affecting other consumers and microbial pathogens via changes in this shared resource. The second study moves to an ecosystem scale and investigates how exotic versus native apple snails may impact Everglades' habitats. We investigated plant preference, consumption, growth and conversion efficiencies in the singly native apple snail to occur in the U.S. (Pomacea paludosa) versus four introduced species (P. canaliculata, P. insularum, P. haustrum and P. diffusa). We found that even though plant preferences are similar, invasive snails tend to eat more, grow more rapidly, and sometimes more efficiently than natives. This suggests that invasive species could have a large impact on the environment, especially the abundance of submerged plants. The third study investigated how palatability of freshwater plants varies with latitude (i.e. geographic scale). Increased herbivory at lower latitudes is hypothesized to select for increased plant defenses, which has been shown to be true for tropical forests, salt marshes, and seaweeds. When we contrasted eight confamilial plants collected in Indiana versus Southern Florida, three of four herbivores significantly preferred northern plants. When we evaluated a second set of plants collected from Indiana versus Central Florida, only one of three herbivores preferred the northern plants. Overall, our results suggest a preference for northern plants, but the strength of this relationship was variable. We hypothesize that this variability may be driven by 1) local variance in herbivore pressure that creates variance in plant defenses, and/or 2) the effect of winter length on the survival and feeding rate of herbivores. The final study expanded to a world scale, and investigated herbivore preference for native vs exotic plants. We found that both N. American crayfish and S. American snails preferred exotic plants over confamilial natives, despite responding to different plant characteristics. The single species of apple snail that occurs in N. American showed no preference for native or exotic plants from a N. American perspective, but instead exhibited preferences that correlated with its history of evolution in S. America. As the N. American species is a sister species of the S. American snails, feeding by the N. American snail appears more affected by its S. American lineage than its recent history in N. America. This suggests that phylogenetic legacy will affect choices of the herbivore as well as resistance or susceptibility of plants.