In this thesis, multiple on-road vehicle tracking problem is explored, with greater consideration of road constraints and interactions between vehicles. A comprehensive method for tracking multiple on-road vehicles is proposed by making use of domain knowledge of on-road vehicle motion. Starting with raw measurements provided by sensors, bias correction methods for sensors commonly used in vehicle tracking are briefly introduced and a fast but effective bias correction method for airborne video sensor is proposed. In the proposed method, by assuming errors in sensor parameter measurements are close to zero, the bias is separately addressed in converted measurements of target position by a linear term of errors in sensor parameter measurements. Based on this model, the bias is efficiently estimated by addressing it while tracking or using measurements of targets that are observed by multiple airborne video sensors simultaneously. The proposed method is compared with other airborne video bias correction methods through simulations. The numerical results demonstrate the effectiveness of the proposed method for correcting bias as well as its high computational efficiency. Then, a novel tracking algorithm that utilizes domain knowledge of on-road vehicle motion, i.e., road-map information and interactions among vehicles, by integrating a car-following model into a road coordinate system, is proposed for tracking multiple vehicles on single-lane roads. This algorithm is extended for tracking multiple vehicles on multi-lane roads: The road coordinate system is extended to two-dimension to express lanes on roads and a lane-changing model is integrated for modeling lane-changing behavior of vehicles. Since the longitudinal and lateral motions are mutually dependent, the longitudinal and lateral states of vehicles are estimated sequentially in a recursive manner. Two estimation strategies are proposed: a) The unscented Kalman filter combined with the multiple hypothesis tracking framework to estimate longitudinal and lateral states of vehicles, respectively. b) A unified particle filter framework with a specifically designed computationally-efficient joint sampling method to estimate longitudinal and lateral states of vehicles jointly. Both of two estimation methods can handle unknown parameters in motion models. A posterior Cramer-Rao lower bound is derived for quantifying achievable estimation accuracy in both single-lane and multi-lane cases, respectively. Numerical results show that the proposed algorithms achieve better track accuracy and consistency than conventional multi-vehicle tracking algorithms, which assumes that vehicles move independently of one another. / Thesis / Doctor of Philosophy (PhD)

Literature on change point analysis mostly requires a sudden change in the data distribution, either in a few parameters or the distribution as a whole. We are interested in the scenario that the variance of data may make a significant jump while the mean of data changes in a smooth fashion. It is motivated by a liver procurement experiment with organ surface temperature monitoring. Blindly applying the existing change point analysis methods to the example can yield erratic change point estimates since the smoothly-changing mean violates the sudden-change assumption. In my dissertation, we propose a penalized weighted least squares approach with an iterative estimation procedure that naturally integrates variance change point detection and smooth mean function estimation. Given the variance components, the mean function is estimated by smoothing splines as the minimizer of the penalized weighted least squares. Given the mean function, we propose a likelihood ratio test statistic for identifying the variance change point. The null distribution of the test statistic is derived together with the rates of convergence of all the parameter estimates. Simulations show excellent performance of the proposed method. Application analysis offers numerical support to the non-invasive organ viability assessment by surface temperature monitoring. The method above can only yield the variance change point of temperature at a single point on the surface of the organ at a time. In practice, an organ is often transplanted as a whole or in part. Therefore, it is generally of more interest to study the variance change point for a chunk of organ. With this motivation, we extend our method to study variance change point for a chunk of the organ surface. Now the variances become functions on a 2D space of locations (longitude and latitude) and the mean is a function on a 3D space of location and time. We model the variance functions by thin-plate splines and the mean function by the tensor product of thin-plate splines and cubic splines. However, the additional dimensions in these functions incur serious computational problems since the sample size, as a product of the number of locations and the number of sampling time points, becomes too large to run the standard multi-dimensional spline models. To overcome the computational hurdle, we introduce a multi-stages subsampling strategy into our modified iterative algorithm. The strategy involves several down-sampling or subsampling steps educated by preliminary statistical measures. We carry out extensive simulations to show that the new method can efficiently cut down the computational cost and make a practically unsolvable problem solvable with reasonable time and satisfactory parameter estimates. Application of the new method to the liver surface temperature monitoring data shows its effectiveness in providing accurate status change information for a portion of or the whole organ. / Ph. D.

Syftet med studien är att undersöka vad elever i årskurs 9 har för syn på deltagande och ombyte i samband med lektioner i idrott och hälsa. Metoden som användes i studien var av kvalitativ ansats i form av fokusgruppsintervjuer. Elever i årskurs 9 intervjuades i grupper om tre-fem personer.  I resultatet framkom att eleverna anser att ämnet idrott och hälsa är roligt och att de oftast deltar. Vidare var det en stor variation vad gäller ombyte till lektionerna. Deltog några elever i föreningsidrott var det större sannolikhet att de valde att byta om till lektioner i idrott och hälsa. De elever som inte byter om till lektionerna anser att det beror på orken, lektionsinnehållet och hur omklädningsrummen är uppbyggda. Det kan dras likheter mellan tidigare forskning och teoretisk bakgrund. Om det finns en inre motivation till deltagande byter eleven oftare om. Anledningar till att eleverna inte byter om beskrivs liknande i den tidigare forskningen som visar att omklädningsrummen kan vara en orsak då det är en otrygg plats.  Studien kan bidra till en ökad förståelse för lärare i idrott och hälsa, för hur elever känner i samband med deltagande och ombyte till lektioner i idrott och hälsa. / The purpose of this study is to examine what pupils in Grade 9 think of participation and changing clothes in physical education lessons. The method used in this study was of a qualitative approach in the form of focus group interviews. Pupils in Grade 9 were interviewed in groups of three to five people. The result showed that the pupils think that the subject of physical education is fun, and they usually participate. Furthermore, there were varying conditions for pupils to change clothes before the lessons. If some pupils participated in club sports, they were more likely to choose to switch clothes to lessons in physical education. The pupils who do not change before lessons believe that it depends on the energy, the lesson content, and how the dressing rooms are structured. Similarities between previous research and the theoretical background can be drawn. If you are motivated to participate, you are more likely to change clothes because you feel an inner motivation. The reasons why pupils do not change are described similarly in previous research, which shows that the changing rooms can be a reason for this, with it being an unsafe place. The study can contribute to an increased understanding of how pupils feel concerning their participation and changing habits before the physical education and health lessons for physical education and health teachers.

Afrikaans speaking believers have been experiencing a degree of disillusionment due to changes in the South African political landscape. This has caused spiritual instability that again caused people to want to escape to beter opportunities elsewhere, reduced church attendance and social isolation. This disillusionment is due to the fact that Afrikaans speaking believers hold to a cultural, social and self empowering type of hope that looks to the advantages of positive circumstances. A great void exists in research dealing with the hope and spirituality of Afrikaans speaking believers who experience such a disillusionment, and that resulted in this study. An empirical study revealed that the Afrikaans community struggles to deal completely with the new South African community. They feel the pressure of limited or no work opportunities due to affirmative action, uncertainty regarding their role in the new South Africa and the breaking down of Afrikaans as a historically respected language and culture. Materialism, a false trust in political and world leaders, negative media reporting, as well as people immigrating for beter opportunities, were singled out as contributors to the breaking down of hope, a hope that takes on the form of cultural entitlement and social self empowerment. A literary study showed that true Christian hope must be distinguished from wishful thinking, the outcome of social, political or economical self empowerment or emotional optimism, but rather that it is grounded in the faith knowledge of Jesus Christ as Redeemer. The church as the family of God provides hope in a space where the past and the future comes together in an active walk of faith that follows the life of Jesus Christ in serving and caring for others. Preaching must be the carrier of hope and the reminder that the promises of God will be realized up and until the coming of Jesus Christ in glory. Perspectives from Scripture confirmed that hope is not just a human thought of wishful thinking, an emotional state of mind or optimism. True Christian hope is an inner faith conviction and trust in the promises of God for salvation, provision and grace, even in the midst of poor or bad circumstances, caused by sin. This Christian hope is initiated and developed through a knowledge of the Word of God, that finds fulfillment in Jesus Christ. True Christian hope is an inner spiritual conviction through faith in Jesus Christ, a practical lifestyle of love in accordance with God’s will and a living expectation for the coming of Jesus Christ. Practical-theoretical guidelines and study work were developed where Afrikaans speaking believers, experiencing a degree of disillusionment due to a changing South Africa, can be pastorally guided to a true Christian hope. / MA (Pastoral Studies), North-West University, Potchefstroom Campus, 2014

Afrikaans speaking believers have been experiencing a degree of disillusionment due to changes in the South African political landscape. This has caused spiritual instability that again caused people to want to escape to beter opportunities elsewhere, reduced church attendance and social isolation. This disillusionment is due to the fact that Afrikaans speaking believers hold to a cultural, social and self empowering type of hope that looks to the advantages of positive circumstances. A great void exists in research dealing with the hope and spirituality of Afrikaans speaking believers who experience such a disillusionment, and that resulted in this study. An empirical study revealed that the Afrikaans community struggles to deal completely with the new South African community. They feel the pressure of limited or no work opportunities due to affirmative action, uncertainty regarding their role in the new South Africa and the breaking down of Afrikaans as a historically respected language and culture. Materialism, a false trust in political and world leaders, negative media reporting, as well as people immigrating for beter opportunities, were singled out as contributors to the breaking down of hope, a hope that takes on the form of cultural entitlement and social self empowerment. A literary study showed that true Christian hope must be distinguished from wishful thinking, the outcome of social, political or economical self empowerment or emotional optimism, but rather that it is grounded in the faith knowledge of Jesus Christ as Redeemer. The church as the family of God provides hope in a space where the past and the future comes together in an active walk of faith that follows the life of Jesus Christ in serving and caring for others. Preaching must be the carrier of hope and the reminder that the promises of God will be realized up and until the coming of Jesus Christ in glory. Perspectives from Scripture confirmed that hope is not just a human thought of wishful thinking, an emotional state of mind or optimism. True Christian hope is an inner faith conviction and trust in the promises of God for salvation, provision and grace, even in the midst of poor or bad circumstances, caused by sin. This Christian hope is initiated and developed through a knowledge of the Word of God, that finds fulfillment in Jesus Christ. True Christian hope is an inner spiritual conviction through faith in Jesus Christ, a practical lifestyle of love in accordance with God’s will and a living expectation for the coming of Jesus Christ. Practical-theoretical guidelines and study work were developed where Afrikaans speaking believers, experiencing a degree of disillusionment due to a changing South Africa, can be pastorally guided to a true Christian hope. / MA (Pastoral Studies), North-West University, Potchefstroom Campus, 2014

Thesis (MSc (Conservation Ecology and Entomology))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: During 2007, two evidence-based studies were undertaken in two catchment areas in South Africa. The first study ascertained the relationships between demographic attributes and general awareness, human impacts, attitudes and water use behaviour. The second study determined whether or not State-of-River (SoR) materials developed for foundation phase learners (grades 1 to 3) improved their understanding of and influenced their attitudes towards river conservation. Surveys were conducted amongst learners (n=1178) and parents (n=1144) from different cultures and socio-economic backgrounds. Questionnaires were available in three languages, namely English, isiXhosa and Afrikaans. The SoR reporting materials were not adequately distributed. The first study could therefore not ascertain whether increased awareness or attitudinal and behavioural changes could be ascribed to SoR reporting in the catchments. The majority of respondents (82%) indicated that there was a need for more information on rivers and 60% of the respondents indicated that they would participate in a follow-up survey. Thirty percent of respondents from the Buffalo catchment and 22% of respondents from the Hartenbos and Klein Brak catchment indicated that they use water very sparingly. Respondents from urban areas scored higher in their attitudes towards river conservation and were more aware of water issues than those from rural areas. Both attitudinal and awareness scores did not align with water use behaviour, with rural respondents using water more sparingly. Attitude and awareness improved with increased education levels. Respondents who indicated that they would rather pay more for water than change their water use behaviour showed the lowest score for attitude towards river conservation. Learners from the Buffalo rural area showed a significant increase in understanding the benefits that healthy rivers provide, and this can be ascribed to the distributed SoR activity book and poster. A survey consisting of quantitative and qualitative items, as well as participatory evaluations determined learners’ level of understanding of human impacts on rivers. The quantitative study showed learners from the Hartenbos and Klein Brak area as well as the Buffalo rural area improved the most over time. The qualitative items showed a 35% and 40% increase in the number of correctly listed items as either making a river happy (healthy) or sad (unhealthy) after exposure to SoR materials. Respondents from both catchments taking part in the participatory evaluations displayed an overall increase in their understanding of good practices, as well as the negative impact of human activities on rivers. Those learners that scored low in the participatory evaluations at time 1 showed the most improvement over time, concluding that those learners who knew the least at the start of the study, gained the most understanding of human impacts on rivers. All schools in the Hartenbos and Klein Brak catchment, with the exception of one, showed a slight increase in understanding of human impacts on rivers. Results from the schools in the Buffalo catchment were more variable. Data gathered demonstrated that the SoR materials helped learners to better understand benefits from clean rivers as well as human impact on rivers. Although the learners from urban areas had a better understanding of the concept of river conservation before contact with the SoR materials, learners from the rural areas showed the most improvement over time. There was an increase in the number of learners that showed a willingness to take responsibility for their actions that could impact on river health. Far more learners mentioned remediation types of actions than protection or preventative actions. A change in peoples’ attitudes and behaviour is needed to ensure adequate protection of South Africa’s natural water resources. Imprinting values and perceptions that would last into adulthood need intervention at an early age and throughout children’s’ formative years. / AFRIKAANSE OPSOMMING: Gedurende 2007, twee bewysgebaseerde ondersoeke is in twee wateropvangsgebiede in Suid Afrika gedoen. Die eerste studie was gerig op die bepaling van die verband tussen demografiese kenmerke, algemene bewustheid, menslike impak, houdings en waterverbruik. Die tweede studie het bepaal of die Stand-van-Rivier (SvR) inligtingsmateriaal wat vir grondslagfase leerlinge (graad 1 tot 3) ontwikkel is, bygedra het tot hulle begrip van en houding jeens die bewaring van riviere. Steekproeftrekkings het leerlinge (n=1178) en ouers (n=1144) vanuit verskillende kultuur- en sosioekonomiese agtergronde betrek. Vraelyste was in drie landstale naamlik Engels, Xhosa en Afrikaans beskikbaar. Die SvR kommunikasie material is nie toereikend versprei nie. Die eerste studie kon derhalwe nie bepaal of groter bewustheid of veranderings in houding en gedrag in hierdie opvangsgebiede aan die SvR verslaggewing toegeskryf kon word nie. Die meerderheid respondente (82%) het aangedui dat daar ‘n tekort and rivierinligting is en 60% van die respondente het hulself bereidwillig verklaar om aan ’n opvolgstudie deel te neem. Dertig persent van die respondente uit die Buffels- en 22% uit die Hartenbos- en Klein Brak-opvangsgebiede het aangedui dat hulle water spaarsamig gebruik. Respondente afkomstig van stedelike gebiede het beter rivierbewaringshoudings getoon en was meer bewus van wateraangeleenthede as die van landelike gebiede. Houdings en bewustheids-vlakke het nie ooreengestem met waterverbruik nie – landelike respondente gebruik water meer spaarsamig. Beide houdings en algemene bewustheid het toegeneem met hoër onderwysvlakke. Respondente wat aangedui het dat hulle eerder meer vir water sal betaal as om hulle verbruik te verminder, het die swakste houding jeens die bewaring van riviere getoon. Leerlinge uit die landelike gebiede van die Buffels opvangsgebied het groter begrip getoon vir die voordele wat gesonde riviere inhou, en dit kan toegeskryf word aan die aktiwiteitsboek en SvR plakkaat wat onder hulle versprei is. ‘n Steekproef bestaande uit kwantitatiewe en kwalitatiewe items, sowel as deelnemende evaluasies is gebruik om leerlinge se vlak van begrip van menslike impak op riviere te bepaal. Die kwantitatiewe studie het aangedui dat die begrip van leerlinge van die Hartenbos en Klein Brak sowel as die van die landelike Buffelsrivieropvangsgebiede oor tyd die meeste toegeneem het. Op die vraag wat riviere gelukkig (gesond) of hartseer (ongesond) maak, het die kwalitatiewe items, na blootstelling van die leerders aan die SvR materiaal, ‘n toename van 35% en 40% in korrekte antwoorde getoon. In die deelnemende evaluasie het respondente van beide opvangsgebiede ‘n toename in begrip van goeie praktyke sowel as die negatiewe impak van menslike aktiwiteite op riviere getoon. Leerlinge wat swak gevaar het in die deelnemende evaluasie gedurende die eerste rondte het die meeste vordering getoon. Die gevolgtrekking is dus dat leerlinge wat die minste geweet het aan die begin van die studie, die meeste geleer het oor menslike impak op riviere. Op een na, het alle skole in die Hartenbos- en Klein Brakrivieropvangsgebied ‘n geringe verhoging in begrip van menslike impak op riviere getoon. Resultate van skole uit die Buffelsopvangsgebied het meer gevarieer. Data versamel het gedemonstreer dat die gebruik van die aktiwiteitsboek en plakkate gelei het tot ’n beter begrip by leerders van die voordele van skoon riviere asook van menslike impak op riviere. Alhoewel die leerlinge van stedelike gebiede beter begrip getoon het oor rivierbewaring voor kontak met die SvR material, het die landelike leerlinge die grootste toename in begrip oor die verloop van die studie getoon. Daar was ook ‘n toename in die aantal leerlinge wat bereid was om verantwoordelikheid vir hulle aktiwiteite wat ‘n impak op riviergesondheid kon hê, te aanvaar. Veel meer leerlinge het tydens die tweede fase verwys na herstel eerder as beskermings of voorkomende gedrag. ’n Verandering in mense se houdings en gedrag is noodsaaklik om genoegsame bewaring van Suid Afrika se natuurlike waterhulpbronne te verseker. Waarde sisteme en persepsies wat met volwassewording steeds geldig sal wees, word reeds teen ’n vroeë ouderdom, gedurende kinders se vormingsjare, vasgelê.

This thesis investigates the use of binocular information for motion-in-depth (MID) perception. There are at least two different types of binocular information available to the visual system from which to derive a perception of MID: changing disparity (CD) and inter-ocular velocity differences (IOVD). In the following experiments, we manipulate the availability of CD and IOVD information in order to assess the relative influence of each on MID judgements. In the first experiment, we assessed the relative effectiveness of CD and IOVD information for MID detection, and whether the two types of binocular information are processed by separate mechanisms with differing characteristics. Our results suggest that, both CD and IOVD information can be utilised for MID detection, yet, the relative dependence on either of these types of MID information varies between observers. We then went on to explore the contribution of CD and IOVD information to time-to-contact (TTC) perception, whereby an observer judges the time at which an approaching stimulus will contact them. We confirmed that the addition of congruent binocular information to looming stimuli can influence TTC judgements, but that there is no influence from binocular information indicating no motion. Further to this, we found that observers could utilise both CD and IOVD for TTC judgements, although once again, individual receptiveness to CD and/or IOVD information varied. Thus, we demonstrate that the human visual system is able to process both CD and IOVD information, but the influence of either (or both) of these cues on an individual’s perception has been shown to be mutually independent.

Trends and patterns of reproductive behaviour in Germany, Austria and Switzerland Abstract The main goal of this diploma thesis is to analyse fertility trends in the (former) German Democratic Republic, the (former) Federal Republic of Germany, Austria and Switzerland after Second World War to 2010 and attitudes of population of the countries above towards parenthood and the changing roles of men and women. German-speaking countries belong to countries with long-term low fertility level, however each country has its own specific reproductive behavior due to historical development. Analysis of fertility is focused on describing the trends of the number of live births and the proportion of children born outside marriage, total fertility rate, cohort fertility, fertility rates by age and the mean age of women at childbirth. Attitudes of respondents towards parenthood and the changing roles of men and women were analyzed based on international survey, European Values Study 2008, by statistical methods - chi-square test and factor analysis. Further, the thesis deals with family policy in German-speaking countries with a focus on current measures. The main findings of this thesis are summarized in the final chapter.

De nos jours, les antennes sont de plus en plus complexes en raison notamment de la nécessité de réaliser une reconfigurabilité en fréquence et/ou en diagramme. Les réseaux réflecteurs et les surfaces sélectives en fréquence sont des candidats particulièrement intéressants pour couvrir les besoins actuels. Cependant, en raison de leur grande taille et de la complexité géométrique croissante de leurs cellules élémentaires, l‘analyse électromagnétique complète de ces structures rayonnantes nécessite énormément de ressources informatiques (mémoire) et exige des temps de calcul prohibitifs, notamment lorsque des éléments de commande tels que des MEMS-RF sont intégrés au sein des cellules. Les techniques numériques classiques basées sur un maillage (spatial ou spectral) systématique ne parviennent pas à simuler de manière efficace de telles structures multi-échelles et nécessitent souvent des ressources informatiques difficiles d’accès pour le concepteur d'antennes. Une technique originale baptisée « Scale Changing Technique (SCT) » tente de résoudre ce problème en segmentant le réseau en de multiples domaines imbriqués les uns dans les autres et présentant divers niveaux d'échelle. Le multi-pôle par changement d’échelle, appelé « Scale Changing Network (SCN) », modélise le couplage électromagnétique entre deux niveaux d’échelle successifs. Ce multi-pôle peut être calculé en résolvant les équations de Maxwell à partir d’une Formulation par Equations Intégrales. La mise en cascade des multi-pôles par changement d’échelle permet alors le calcul de la matrice impédance (ou admittance) de surface du réseau complet. Cette matrice peut à son tour être utilisée pour simuler la diffusion électromagnétique d’une onde incidente par le réseau. Le calcul des différents multi-pôles par changement d’échelle peut être effectué séparément de sorte que le temps de simulation du réseau complet peut être considérablement réduit en parallélisant le calcul. Par ailleurs, la modification de la géométrie de la structure à une échelle donnée, lors de la phase de conception, nécessite seulement le calcul de deux multi-pôles par changement d’échelle et ne requiert pas une nouvelle simulation de toute la structure. Cette caractéristique fait de la SCT un outil de conception modulaire. Dans le cadre de cette thèse, la SCT a permis de tenir compte de la taille finie des réseaux et de modéliser efficacement les couplages électromagnétiques entre les cellules élémentaires. Des réseaux réflecteurs uniformes et non uniformes ont été simulés par la SCT et les performances numériques de la méthode ont été analysées. / Future antenna architectures especially for space applications are becoming more and more complex due to the need of reconfigurability. This reconfigurability is needed in terms of frequency, reliability, radiation pattern and power consumption. In this context, reflectarrays and frequency selective surfaces (FSSs) are particularly the hottest domains of RF design. The accurate analysis of electromagnetic (EM) scattering from such type of complex finite-sized reflectarray antenna structures is of great practical interest. However due to their large electrical size and complex cellular patterns specially when tuning elements such as RF-MEMS are also integrated within the array elements, conventional full-wave EM analysis of such multiscale structures either fail or require enormous amount of computational resources to resolve prohibitively large number of unknowns. Moreover the characterization of large structures would normally require a second step for optimization and fine-tuning of several design parameters, as the initial design procedure assumes several approximations. Therefore a full-wave analysis of the initial design of complete structure is necessary prior to fabrication to ensure that the performance conforms to the design requirements. A modular analysis technique which is capable of incorporating geometrical changes at individual cell-level without the need to rerun the entire simulation is extremely desirable at this stage. An indigenous technique called Scale Changing Technique (SCT) addresses this problem by partitioning the cellular reflectarray geometry in numerous nested domains and subdomains defined at different scale-levels in the array plane. Multi-modal networks, called Scale Changing Networks (SCNs), are then computed to model the electromagnetic interactions between any two successive partitions by method of moments (MoM) based integral equation approach. The cascade of these networks allows the computation of the equivalent surface impedance matrix of the complete array which in turn is utilized to compute far-field radiation patterns. Full-wave analysis of both passive and active (electronically tunable by RF-MEMS) reflectarrays has successfully been performed by the SCT while utilizing very small amount of computational resources as compared to conventional full wave methods. Moreover, to speed up the SCT modeling of the reflectarrays, equivalent electrical circuit models have been extracted and applied for individual design and optimization of the reflectarray phase shifter elements.

Le vieillissement de la population nécessite une politique de prévention des chutes efficace chez les personnes âgées. Les chutes ont des conséquences importantes aussi bien en termes de baisse de qualité de vie et de perte d’autonomie, que financiers, occasionnés par leurs soins et leur prise en charge. Cependant, la complexité du mécanisme de la chute et son caractère multifactoriel, rendent le diagnostic et l’évaluation du risque de chute encore difficile, notamment parmi la population des personnes dites « en bonne santé ». Conjointement, bien que les programmes multi-interventionnels commencent à montrer leur efficacité, ces derniers restent peu, sinon mal, évalués. Par ailleurs, la mise en place d’une politique de prévention adaptée et efficace, doit être centrée sur la qualité du soin et la satisfaction du patient. Celles-ci nécessitent le passage vers un mode d’organisation du travail coopératif, en réseau. Toutefois, ce changement conduit à des modifications dans les pratiques et identités professionnelles. Cette thèse a pour objectif d’étudier les conditions de réussite d’une action de prévention, structurée et coordonnée, en santé publique. Nous présentons et proposons tout d’abord les conditions et outils permettant une homogénéisation et une standardisation des pratiques incontournables pour la mutualisation des efforts individuels et permettre ainsi une plus grande efficacité. Nous étudions également les impacts d’une telle intervention, en termes financiers et de risque de chute. Nous analysons ensuite comment conduire le changement pour permettre une évolution et une adaptation des mentalités mais aussi des modes d’organisation de l’activité. / The prevention of falls amongst the elderly population is a major public health concern. Since the elderly live longer and longer, it is crucial to think of efficient measures in order to prevent such falls. Falls amongst the elderly can have dramatic consequences such as a decrease in quality of life, a loss of autonomy as will cause financial difficulty due to high cost of rehabilitation. However, depending upon the complexity of the fall and its multiple determinants, diagnosing and evaluating the risk of a fall remains complicated, particularly amongst those in "good health". While multi interventional programs may exist such as equilibrium coordination and muscular reinforcement, these programs are rarely proved to be efficient in fall prevention. An adapted and efficient method of prevention must be centered on quality and satisfaction of the patient in the offered care. Such method would imply replacement of an older organization with a system defined in a network activity. However, this method would go hand in hand with the modifications in professional practices and identities. In this thesis I will examine the success rate to implement a structured method of health care prevention against falls. To achieve this prevention, we must first present the necessary conditions and tools which will homogenize and standardize these success rates. Next, I will analyze the characteristics of current methods to prevent falls in order to modernize and rationalize the process. In order to be successful, this process needs to be targeted towards a network strategy.