Les principaux objectifs des opérateurs ferroviaires visent à accroître la sécurité, réduire les coûts d’exploitation et de maintenance et augmenter l’attractivité et les bénéfices du transport ferroviaire en offrant de nouveaux services aux passagers. Ceci ne pourra être atteint que grâce à la multiplication des échanges de données entre les différents acteurs du monde ferroviaire. L’interopérabilité, l’efficacité spectrale, l’optimisation de l’usage des ressources radio et l’amélioration de la fiabilité des communications sont des exigences fortes pour les applications de télécommunication ferroviaires. Les recherches dans le domaine de la radio cognitive ont vu le jour afin de répondre aux besoins de communication de l’armée ainsi qu’aux besoins dans les secteurs de la sécurité publique. Ces domaines partagent souvent les mêmes exigences que les chemins de fers. Ainsi, la radio cognitive a montré un potentiel prometteur pour répondre aux besoins listés précédemment. Une des principales fonctionnalités d’un dispositif de radio cognitive est de prendre conscience de son environnement radioélectrique et de détecter les bandes disponibles. Trois principaux éléments définissent l’environnement de la radio cognitive : l’utilisateur, les règles d’accès au spectre radio et les domaines radio. Cette thèse met en avant plusieurs contributions relatives à la reconnaissance de l’environnement radiofréquence et la détection de bandes libres. Plus spécifiquement, ces contributions portent sur la reconnaissance par la radio cognitive de l’occupation du spectre et de la modulation des signaux présents dans les bandes analysées. Ces fonctions ont été conçues pour le contexte ferroviaire, c’est-à-dire la grande vitesse et un environnement électromagnétique difficile en présence de bruit impulsif. / An essential goal of railway operators is to increase safety, reduce operation and maintenance costs, and increase attraction and profit by offering new services to passengers. These objectives will be reached thanks to a huge increase of data fluxes exchanges between railways stakeholders and infrastructures.Interoperability, spectral efficiency, optimization of radio resource usages, and improvement of communications reliability are of significant interest for railway applications. The Cognitive Radio (CR) research has been successfully applied to meet the communication needs of the military as well as the public-safety sectors, which share many of the same needs as railway. CRs have shown significant promise to answer all of the previously listed requirements. One of the main capabilities of a CR device is to sense and finally become aware of its environment. Three major domains define the environment of the CR, namely, the user, policy, and radio domains. This thesis highlights several contributions to radio environment awareness of a CR device. More specifically, these contributions lie in the spectrum awareness and waveform awareness functions of the CR. We designed these functions for the railways context, that is, a high speed vehicular context, besides difficult electromagnetic environments resulting a heavy-tailed impulsive noise.

The effect of rotation on the stability of multiple jets in planetary atmospheres is system- atically investigated. Typically in Jovian planetary atmospheres, multiple zonal jets have been observed and their morphology has been systematically studied. The formation of jets has always been viewed as a nonlinear problem where most work has followed from the ideas of potential vorticity (PV) homogenization or turbulent mixing on a β-plane. In our present work, we have aimed to look at the linear stability of multiple jets in a geophysical fluid, and hope to add further insight into the observed jet profiles in β-plane turbulence. In addition, we also study the evolution and life-cycle of these jets as they interact with each other in a non linear fashion. We begin with the linear stability of the \Bickley jet" using the linearized shallow water quasigeostrophic (QG) equations. We have included a finite deformation radius in our calculations to partially mimic the effects of compressibility. A family of synthetically generated velocity profiles with east-west jets are then studied. In particular, a variety of flow configurations with two jets have been considered with a parameter sweep across jet separation, relative jet strength and thickness. As a broad observation, it is noted that an asymmetric east-west jet profile with a stronger and sharper eastward jet is the most stable of all the profiles considered, and a finite deformation radius further stabilizes such profiles. More realistic jet profiles have also been considered and the role of a finite deformation radius in stabilizing such jets is elucidated. We also examined the nonlinear evolution of multiple jets in a periodic domain and in a channel geometry, as we undertake freely decaying long time simulations of the governing QG equation. As per the \Selective Decay" principle we observe that arbitrary initial conditions approach the flow configuration of the prescribed \suitable end states". In addition, we have shown how a finite deformation length scale modifies these \suitable end states". As a broad observation, we have noted that a linearly unstable jet flow configuration, in the presence of β, breaks down into turbulence and reforms into a more asymmetric jet profile with a stronger and sharper eastward jet. The inclusion of a finite deformation length scale in our calculations, is observed to suppress such jet formation. Similar numerical experiments have been performed in a channel and the results have been compared. Chiefly, for the end states, the nature of the observed jet asymmetry is reversed, i.e., the westward jets are observed to be stronger in a channel.

Aligning multiple biological sequences such as protein sequences or DNA/RNA sequences is a fundamental task in bioinformatics and sequence analysis. These alignments may contain invaluable information that scientists need to predict the sequences' structures, determine the evolutionary relationships between them, or discover drug-like compounds that can bind to the sequences. Unfortunately, multiple sequence alignment (MSA) is NP-Complete. In addition, the lack of a reliable scoring method makes it very hard to align the sequences reliably and to evaluate the alignment outcomes. In this dissertation, we have designed a new scoring method for use in multiple sequence alignment. Our scoring method encapsulates stereo-chemical properties of sequence residues and their substitution probabilities into a tree-structure scoring scheme. This new technique provides a reliable scoring scheme with low computational complexity. In addition to the new scoring scheme, we have designed an overlapping sequence clustering algorithm to use in our new three multiple sequence alignment algorithms. One of our alignment algorithms uses a dynamic weighted guidance tree to perform multiple sequence alignment in progressive fashion. The use of dynamic weighted tree allows errors in the early alignment stages to be corrected in the subsequence stages. Other two algorithms utilize sequence knowledge-bases and sequence consistency to produce biological meaningful sequence alignments. To improve the speed of the multiple sequence alignment, we have developed a parallel algorithm that can be deployed on reconfigurable computer models. Analytically, our parallel algorithm is the fastest progressive multiple sequence alignment algorithm.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2010.

Thesis (M.Sc.)--Memorial University of Newfoundland, Faculty of Medicine, 1998. / Typescript. Bibliography: leaves 193-209.

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International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A radiolocation problem using DS-CDMA waveforms with array-based receivers is considered. It is assumed that M snapshots of N(s) Nyquist sample long data are available, with a P element antenna array. In the handshaking radiolocation protocol assumed here, data training sequences are available for all K users. As a result, the received spatial-temporal matrix R ∈ C^(MN(s)x P) is approximated by a sum of deterministic signal matrices S(k)^b ∈ C^(MN(s) N(s)) multiplied by unconstrained array response matrices A(k) ∈ C^(N(s)x P). The unknown delays are not estimated directly. Rather, the delays are implicitly approximated as part of the symbol-length long channel, and solutions sparse in the rows of A are thus sought. The resulting ML cost function is J = ||R - ∑(k=1)^K S(k)^bA(k)||(F). The Generalized Successive Interference Cancellation (GSIC) algorithm is employed to iteratively estimate and cancel multiuser interference. Thus, at the k-th GSIC iteration, the index p(k) = arg min(l ≠ p(1),...,p(k-1)) {min(A(l)) ||R^k-S(l)^bA(l)||(F)} is computed, where R^k = ∑(l=1)^(k-1) S(pl)^bÂ(pl). Matching pursuits is embedded in the GSIC iterations to compute sparse channel/steering vector solutions Â(l). Simulations are presented for DS-CDMA signals received over channels computed using a ray-tracing propagation model.

Although bicycling has been the subject of increasing academic attention, particularly in the areas of mode choice, benefit analyses, and discussions of policies/treatments, much less attention has been devoted to actually studying how communities have made decisions about whether and what they’ll implement in regards to bicycle infrastructure. “Policy entrepreneurs” are theorized as actors centrally responsible for either creating an opportunity or capitalizing on an opportunity to pair a public problem with a policy solution. A survey instrument solicited directly the participation of the 200 most populous municipalities within the United States. Using a variety of analytical tools (and merged data sources) as well as a novel matching methodology for the selection of case studies, it was possible to identify interesting and broadly informative relationships, which were explored further via the case study comparison. 20 case interviews were conducted across 6 case study cities as a complement to the survey project. Individual policy entrepreneurs and their role or qualities were not significant quantitatively or qualitatively, despite being regularly present. However, having a network of supportive actors (including strong champions/policy entrepreneurs) played a critical role in making projects happen and at larger scales. Advocates and planners may be more successful by being attuned to these networks and political contexts and taking advantage of open “windows” of engagement. Alternatively, these windows can be opened ‘manually’ through grant applications, developing relationships, hosting trainings or speakers, and more. Lastly, city population was also associated with implementation, suggesting underlying factors to be explored in the future.

More than 50% of people with MS fall in any six-month period. The importance of developing a suitable falls management programme has been identified by people with MS and professionals. This thesis aimed to develop a model for an MS falls intervention. The studies employed a systematic approach to evaluate the risk factors for falls and to identify the optimal programme content, format and structure. Methods The thesis comprises two sections; the first involving a systematic review and an observational study of falls risk factors (n=148). Part two included a second systematic review to inform programme content, and a nominal group study (n=36) to explore approach, format and structure from the perspective of key stakeholders. Results Part one identified the potential target group (people at key mobility transition stages and those with progressive MS), and mechanisms by which the intervention could act (the identification of specific risk factors associated with falls in MS). These include non-modifiable disease and demographic characteristics (e.g. MS classification and gender), and potentially modifiable clinical characteristics (including balance, mobility, continence issues and medication usage). Part two identified that an MS specific falls programme should address falls and participation-related outcomes, incorporating educational activities and a programme of individually tailored gait, balance and functional training. The programme should use a collaborative approach; supporting participants to achieve sufficient intensity and duration of exercise and to integrate falls prevention strategies into their daily lives. The programme should enable participants to engage flexibly according to individual needs and preferences. Conclusions This thesis has identified specific risk factors associated with accidental falls in MS. The evaluation indicates that the success and sustainability of an MS falls programme requires that it is MS specific, employs a collaborative approach and moves away from the group-based, weekly format common to many generic falls programmes.

Background: The current studies aimed to explore the effects of different variants of multiple sclerosis (MS) on social cognitive skills such as emotion perception, theory of mind (ToM) and empathy. Various aspects of empathy were measured using newly developed video paradigm that generated reliable and consistent responses in study participants. Further, the relationships between social cognition abilities and cognitive functioning, MS severity, mood and age were explored. The final aim was to establish whether difficulties in social cognition predicted restricted social participation and reduced quality of life in MS. Methods: This research measured multi-domain emotion perception, ToM and empathy using more ecologically valid measures than previous studies in participants with relapsing-remitting MS (n = 30), chronic progressive MS (n = 26) and matched healthy controls (n = 31). Executive functioning was measured using verbal fluency, whereas speed of processing was tested with the Digit Symbol Coding Task. Self-report measures were administered to assess of empathy, social participation, MS severity and mood. Results: Both MS groups presented with impairments in emotion perception and ToM but not in empathy. Cognitive functioning was associated with some measures of emotion perception and ToM. Reduced quality of life was inconsistently predicted by personal distress only and some aspects of emotion perception in individuals with MS. No aspects of social cognition were found to be a significant predictor of restricted social engagement in MS. Conclusion: Both MS samples demonstrated similar emotion perception and ToM impairments and no significant empathy impairment, though those with progressive MS reported poorer social participation. Lower levels of emotion perception and personal distress predicted some aspects of quality of life. Since the pattern of these results proved to be inconsistent, it is important to interpret the findings with caution, and to further explore socio-emotional functioning in MS.