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Knowledge of the channel over which signals are sent is of prime importance in modern wireless communications. Inaccurate or incomplete channel information leads to high error rates and wasted bandwidth and energy. Although active channel measurement is commonly used to gain channel knowledge, it can only accurately represent the channel at the time the measurement was taken, makes energy and bandwidth demands, and adds significant complexity to the radio system. Due to the highly time variant nature of wireless channels, active measurements become invalid almost as soon as they are taken, making alternative approaches to predicting future behaviour highly attractive. Such systems would allow maximum advantage to be taken of the limited bandwidth available and make significant power savings. This thesis investigates a number of complementary technologies, leading towards a channel prediction scheme suitable for mobile devices. As a first step towards channel prediction, anomaly detection is investigated within periodic wireless signals to establish when radical changes in the channel occur. In pre- vious experiments, long monotonic sequences had been observed to coincide with certain anomalies but not others when using Kullback-Leibler Divergence (KLD) analysis, possibly allowing the characterisation of anomaly types. An investigation is described to explain the origin of these features in a rigorous mathematical sense. A proof is given for the causes of the monotonic sequences, followed by a discussion of the types of signal anomaly which would underly such a feature and the value of this information. The second part describes a novel channel characterisation method which uses a class of Recurrent Neural Network (RNN) called an Echo State Network (ESN). Using this tool, a channel characterisation system can be constructed without an explicit statistical or mathematical model of the wireless environment, relying instead on observed data. This approach is much more convenient than existing models which require detailed information about the wireless system's parameters and also allows for new channel classifications to be added easily. It is able to achieve double the correct classification rate of a conventional statistical classifier, and is computationally simple to implement, making it ideal for inclusion on low-power mobile devices. Following their successful use in characterisation, ESNs are used in the final part in an investigation into channel prediction in a number of different scenarios. They were however found to be unable to produce useful predictions for all but the most trivial channel models. An alternative method is described for indoor environments using an approach inspired by ray tracing. It is simple and computationally lightweight to implement, again making it suitable for mobile devices. Simulation results show that it can outperform pilot-assisted methods by a significant margin, while not wasting bandwidth on channel measurement.

Objective: Telementoring programs like Project ECHO® (Extension for Community Healthcare Outcomes) employ didactics, case-based learning and an “all teach-all learn”approach to increase PCP knowledge/confidence in managing chronic health conditions. The AAP Epilepsy and Comorbidities ECHO aimed to incorporate Quality Improvement (QI) methodology to create sustainable practice change, while increasing PCP knowledge/confidence/self-efficacy in epilepsy management using the ECHO model. Methods: ECHO sessions occurred monthly (5/2018-12/2018). Sessions included lectures, case presentations/discussion and QI review. Practices, recruited through the AAP, implementedmonthly PDSA cycles using team huddles, chart reviews, QI coaching calls and discussion. Measures for improvement were selected from the American Academy of Neurology Epilepsy Measures set. The AAP Quality Improvement Data Aggregator was used for data entry, run chart development, tracking outcomes. Participants completed pre and post-surveys and received Maintenance of Certification Part 4 credits. Results: Average session attendance was 14 (13-17), across 7 practices in 5 states. QI coaching facilitated practice change and development of resource toolkits with documentation templates, safety handouts, medication side effects sheets. Individual and aggregate run charts with data analysis augmented workflow changes. 479 chart reviews demonstrated improvement in 6/7 measures (Table1): documenting seizure frequency (7.1% increase), anti-seizure therapy side effects (23%), safety education(41.6%, p=0.036); Mental/behavioral health screening(32.2% p=0.027); Tertiary Center referral(26.7%); Health Care transition(45.3%, p=0.005). Counseling for women of childbearing age decreased by 7.8%. Participants reported gains in knowledge/confidence/self-efficacy regarding epilepsy management (p< 0.02). Conclusions: This project demonstrated that integrating QI into an ECHO model results in sustainable practice change and increases PCP knowledge/confidence/self-efficacy in managing epilepsy.

This research was motivated by the growing concerns regarding social media platforms roles in the presentation of conspiracy theories as compelling alternative narratives regarding contemporary social events. Specifically, this research asks whether Facebook’s algorithm autonomously recommends groups that are organized around conspiracy theories regarding contemporary political and social events to end users, despite the user not previously indicating interest in those topics. Based on coverage of biases in Facebooks content ranking and recommendation algorithms surrounding the 2020 presidential election, it was hypothesized that, over time, Facebook would increasingly seek to recommend conspiratorial content to its users to retain them on the platform. Eight test profiles were created under three observation protocols over the course of the fall 2022 semester. Each profile created was restricted in how it interacted with the Facebook platform. In creating the first three profiles, only the information that is necessary for profile creation was given, name, gender, birthdate, phone number, and email address. The first profile would only view the first twelve recommended groups, without joining them. The second profile would view and join the first twelve recommended groups, and the third profile would view and join the first twelve recommended groups, and then would also leave five random groups from the previous day. A second protocol was designed to expedite the observation process and expand the sample of groups observed per profile. Five profiles were made under this protocol, wherein the profiles would follow two Facebook pages prior to observation and have slight variations in their demographic information. These profiles only viewed and followed the first recommended group, and then refreshed the recommendation list to generate updated groups in real time. Over the course of this project, Facebook did not recommend a single group to any of the test profiles that principally discussed or recommended conspiracy theories. Instead, it was found that Facebook seeks to recommend groups that are popular in the users local area first, but only until the user has indicated enough unique interests to begin steering the recommendations. Each profile was recommended a geolocation based set of groups, but within days of observation, those groups were no longer chiefly recommended. Instead, it was found that user behavior is heavily influential regarding what groups and topics are recommended. Secondly, among all profiles, the topics featured among the groups being recommended homogenized over the course of observation, to the exclusion of all other topics. Further research should look into whether this homogenization is a function of having so few user inputs, or typical behavior of Facebook more broadly. If it is the latter, this may contribute to the propensity for individual users to arrive in digital echo chambers.

<p>Acoustic echo cancelation (AEC) composes a fundamental property of speech processing to enable a pleasant telecommunication conversation. Without this property of the telephone the communicator would hear an annoying echo of his own voice along with the speech from the other communicator. This would make a conversation through any telecommunication device an unpleasant experience.</p><p>AEC has been subject of interest since 1950s in the telecom industry and very efficient solutions were devised to cancel linear echo. With the advent of low cost hands free communication devices the issue of non linear echo became prominent because these devices use cheap loudspeakers that produce artifacts in addition to the desired sound which will cause non linear echo that cannot be cancelled by linear echo cancellers.</p><p>In this thesis a Harmonic Distortion Residual Echo Cancelation algorithm has been chosen for further investigations (HDRES). HDRES has many of those features that are desirable for an algorithm which is dealing with nonlinear acoustic echo cancelation, such as low computational complexity and fast convergence. The algorithm was first implemented in Matlab where it was tested and modified. The final result of the modified algorithm was then implemented in C and integrated with a complete AEC system. Before the implementation a number of measurements were done to distinguish the nonlinearities that were cause by the mobile phone loudspeaker. The measurements were performed on three different mobile pones which were documented to have problems with nonlinear acoustic echo.</p><p>The result of this thesis has shown that it might be possible to use an adaptive filter, which has both low complexity and fast convergence, in an operating AEC system. However, the request for such a system to work would be that a doubletalk detector is implemented along with the adaptive algorithm. That way the doubletalk situation could be found and the adaptation of the algorithm could be stopped. Thus, the major part of the speech would be saved.</p>

The problem this investigation deals with is how The Echo functions as a communication vehicle within the TDC. Information was gathered through visits, interviews and a questionnaire. Organization is as follows: Chapter I, introduction, Chapter II, history and development; Chapter III, analysis of questionnaire data; Chapter IV, content; Chapter V, summary and conclusions. The study found that The Echo is often the sole source of TDC information to inmates, frequently aids administrators in providing inmates with information, provides an outlet for creativity, and enjoys little censorship. The report concludes that The Echo is an effective information medium, and that future study is possible in the role of the prison press in influencing rehabilitation, its contact with the outside public, and in inmate-produced magazines and journals.

RésuméINSTRUMENT PEDAGOGIQUE LANGAGIER ET PUBLIC A BESOIN EDUCATIF PARTICULIEREléments pour la formation des enseignants spécialisésCette recherche doctorale vise à questionner la manière dont les enseignants spécialisés option D – chargés de l'enseignement et de l’aide pédagogique aux élèves présentant des troubles importants des fonctions cognitives et/ ou des troubles envahissants du développement– enseignent le langage oral. Certains enseignants sont en effet démunis face au développement des compétences langagières de leurs élèves et regrettent le peu d'outils existants. Pourtant, le langage oral est une priorité pour l'institution scolaire car il est garant d'une bonne intégration scolaire et sociale. Il est donc primordial de réfléchir à une didactique de l'oral. Il s’agit d’un travail collaboratif, inscrit dans le cadre de la didactique professionnelle, supposant la constitution d’un collectif d’enseignants volontaires qui acceptent d’analyser leur travail avec le chercheur. Quatre enseignantes et vingt-six de leurs élèves participent à notre recherche. Des entretiens en autoconfrontation de groupe permettront aux enseignantes une réflexion collective sur leur propre travail et sur le travail de leurs pairs. Cette analyse de l'activité débouchera sur une introspection professionnelle mettant en lumière l'expérience vécue qui n'est pas consciente. Ainsi, chaque enseignante pourra expliquer au collectif le but de l'activité. L'artéfact utilisé par les quatre enseignantes est l'album écho, outil éphémère s'appuyant sur des photographies d'élèves en activité. Ces photographies leur font écho car chaque élève a vécu la situation. Avec l'étayage de l'adulte, l'élève développera le vocabulaire, la syntaxe, la prononciation, mais aussi les aspects discursifs du langage ou bien déclenchera l'envie de parler chez certains élèves ayant des troubles envahissants du développement. Quels processus sont mis en œuvre pour passer de l'artéfact à l'instrument afin de favoriser le développement langagier des élèves à besoins particuliers? Quelles caractéristiques de ces interactions utiliser pour la formation des enseignants spécialisés?Mots clés : didactique professionnelle, langage oral, troubles cognitifs, troubles envahissants du développement, album écho. / SummaryLANGUAGE AND PUBLIC EDUCATIONAL INSTRUMENT A PARTICULAR EDUCATIONAL NEEDElements for the training of specialized teachersThis doctoral research aims to question the way in which Option D specialized teachers - responsible for teaching and for the pedagogical support to students with significant cognitive impairment and / or pervasive developmental disorders - teach oral language. Some teachers do not know how do deal with the language development of their students and regret the lack of existing tools. However, oral language is a priority for the school institution because it guarantees good school and a good social integration. It is, therefore, important to think about an oral didactics. It is a collaborative work, included in the framework of professional didactics, supposing the constitution of a collective of voluntary teachers who agree to analyze their work with the researcher. Four teachers and twenty-six of their students participate in our research. Self-confrontation group interviews will give teachers a collective reflection on their own work and on the work of their peers. This analysis of the activity will lead to a professional introspection highlighting the lived experience that is not conscious. Thus, each teacher will be able to explain to the collective the purpose of the activity. The artifact used by the four teachers is the album Echo, an ephemeral tool based on photographs of the students in activity. These photographs echo them because each student has experienced the situation. With the support of the adult, the student will develop the vocabulary, the syntax, the pronunciation, but also the discursive aspects of language or, for some students with pervasive developmental disorders, will trigger the desire to speak. What processes are being used to move from artifact to instrument to support the language development of students with special needs? What characteristics of these interactions should be used for the training of specialized teachers?Key words: professional didactics, oral language, cognitive disorders, pervasive developmental disorders, Echo album.

The Dixon technique is a well-established method in magnetic resonance imaging for obtaining separate images of water and fat. Here we present a generalized solution to the two-point Dixon problem with a geometric interpretation, allowing for flexible echo times and a multi-peak fat model. By simulation and experiment, we have analyzed the dependence on the echo times of the error in the water, fat, and relative background phasor values due to both signal noise and T2* decay. Furthermore, we have demonstrated that broken symmetry due to the multi-peak nature of fat enables direct water and fat determination without phase correction, and we have quantified the reliability of this technique as a function of the echo times. The results may provide valuable guidance for selecting scan parameters to balance the objectives of optimizing fat-water identification, minimizing error in the pixel values, and minimizing total scan time.

Acoustic echo cancelation (AEC) composes a fundamental property of speech processing to enable a pleasant telecommunication conversation. Without this property of the telephone the communicator would hear an annoying echo of his own voice along with the speech from the other communicator. This would make a conversation through any telecommunication device an unpleasant experience. AEC has been subject of interest since 1950s in the telecom industry and very efficient solutions were devised to cancel linear echo. With the advent of low cost hands free communication devices the issue of non linear echo became prominent because these devices use cheap loudspeakers that produce artifacts in addition to the desired sound which will cause non linear echo that cannot be cancelled by linear echo cancellers. In this thesis a Harmonic Distortion Residual Echo Cancelation algorithm has been chosen for further investigations (HDRES). HDRES has many of those features that are desirable for an algorithm which is dealing with nonlinear acoustic echo cancelation, such as low computational complexity and fast convergence. The algorithm was first implemented in Matlab where it was tested and modified. The final result of the modified algorithm was then implemented in C and integrated with a complete AEC system. Before the implementation a number of measurements were done to distinguish the nonlinearities that were cause by the mobile phone loudspeaker. The measurements were performed on three different mobile pones which were documented to have problems with nonlinear acoustic echo. The result of this thesis has shown that it might be possible to use an adaptive filter, which has both low complexity and fast convergence, in an operating AEC system. However, the request for such a system to work would be that a doubletalk detector is implemented along with the adaptive algorithm. That way the doubletalk situation could be found and the adaptation of the algorithm could be stopped. Thus, the major part of the speech would be saved.

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