Spectrally sparse signals arise in many applications of signal processing. A spectrally sparse signal is a mixture of a few undamped or damped complex sinusoids. An important problem from practice is to reconstruct such a signal from partial time domain samples. Previous convex methods have the drawback that the computation and storage costs do not scale well with respect to the signal length. This common drawback restricts their applicabilities to large and high-dimensional signals. The reconstruction of a spectrally sparse signal from partial samples can be formulated as a low-rank Hankel matrix completion problem. We develop two fast and provable non-convex solvers, FIHT and PGD. FIHT is based on Riemannian optimization while PGD is based on Burer-Monteiro factorization with projected gradient descent. Suppose the underlying spectrally sparse signal is of model order r and length n. We prove that O(r^2log^2(n)) and O(r^2log(n)) random samples are sufficient for FIHT and PGD respectively to achieve exact recovery with overwhelming probability. Every iteration, the computation and storage costs of both methods are linear with respect to signal length n. Therefore they are suitable for handling spectrally sparse signals of large size, which may be prohibited for previous convex methods. Extensive numerical experiments verify their recovery abilities as well as computation efficiency, and also show that the algorithms are robust to noise and mis-specification of the model order. Comparing the two solvers, FIHT is faster for easier problems while PGD has a better recovery ability.

Improving the efficiency of traffic operations along arterials is currently a priority for many agencies as their roadway infrastructure is built out to the largest possible capacity within the urban environment. Many advanced systems are being implemented to optimize traffic signal timing. Air quality is typically not a consideration when these decisions are made. The relationship between exposure to air pollution and traffic signal timing has not been fully explored by other researchers. This study is the first research effort to combine detailed traffic signal timing data (at 5 second intervals) and air pollutant exposure data. Results show that longer green time along the busy arterial reduces pollutant levels, while increased volume per cycle increases pollutant levels. This research quantifies the factors that contribute to pedestrian, bicyclist, and transit user exposure at a busy intersection along an urban arterial. The factors include traffic signal timing, weather related variables, traffic volumes, and heavy vehicle and bus presence. Additionally, the impact of an adaptive traffic signal system on air quality is assessed to understand the implications of signal timing on air pollutant exposure.

L’étude traite de la détection de cibles mobiles dans un contexte de radar passif bistatique utilisant les émetteursde télévision numérique TNT (DVB-T) comme émetteurs d’opportunité. Outre leur présence généralisée sur leterritoire, l’intérêt de ces émissions réside dans leur relative largeur de bande permettant une bonne précisiond’estimation. Le principal inconvénient de ce type d’approche réside dans l’éblouissement par le signal en trajetdirect, des échos de très faible intensité des cibles d’intérêt. Après un rappel du principe du radar bistatique etde la norme OFDM utilisée par les signaux TNT, une première étude donne une construction originale du signalde référence dans le cas multi-capteurs : le signal de référence est construit par un traitement d’antenne de typeCAPON où le balayage des paramètres optimaux est remplacé par la connaissance de signaux pilotes inséré dansles symboles OFDM. Ensuite le rapport se focalise sur l’estimation d’un filtre de canal multitrajet à partir dela connaissance de la modulation OFDM utilisée. Ce filtre, d’abord étudié comme réjecteur de fouillis originalavant détection par la fonction d’ambiguïté, donne des résultats semblables aux méthodes classiques de réjectionde fouillis standard. Étendu à toutes les fréquences Doppler, son module au carré est utilisé comme un nouveaudétecteur présentant un très faible niveau de clutter, surpassant ainsi la fonction d’ambiguïté. Une interprétationen terme de traitement d’antennes du nouveau détecteur ouvre la voie à des variantes haute-résolution de celui-ci.La validité du nouveau détecteur est illustrée par des résultats sur données réelles. / The study focuses on moving target detection from passive bistatic radar with DVB-T transmitters used asopportunity transmitters. In addition to their widespread geographical coverage, they allow a good estimationaccuracy due to their quite large bandpass. Nevertheless the continuous powerful direct path masks the verylow intensity echoes of targets of interest. The passive bistatic radar principle and the CP-OFDM standardused by DVB-T are briefly reminded, then, a new first study of reference signal retrieving in multiple sensorsconfiguration is given : the reference signal is built using a Capon receptor where the parameters scan is replacedby the knowledge of pilot signals inserted in the OFDM symbols. Next, the report addresses the multipath channelestimate by using the OFDM signal structure. This channel is firstly studied for clutter rejection before detectionfrom the cross ambiguity function (CAF). We obtain similar results than those of the classical rejection methods.This channel is extended to the whole Doppler shift, and its squared modulus acts as a new low clutter detectorthat outperforms classical CAF. A virtual beamforming interpretation of the channel estimation opens a new pathtowards high resolution array processing. Results given on real data illustrate the validity of this new channeldetector (CHAD).

Syftet med studien var att undersöka människors upplevelser av emojis i textlig kommunikation. I studien tillämpades en kvalitativ metod för undersökningen i form av Braun och Clarkes (2006) Tematiska analys. Datainsamlingen bestod av tre fokusgrupper med fyra deltagare i varje grupp, varav elva deltagare var kvinnor och en delatagare var man. Den Tematiska analysen genererade tre teman: Första temat Emojikodens trygghet och osäkerhet beskriver deltagarna känslan av trygghet genom användning av specifika emojis som skapar en kod för att hantera olika relationer. Emojikoden kan även skapa osäkerhet då en relation utvecklas eftersom emojis kan tolkas på olika sätt. Andra temat Emojis förstärker eller mildrar budskap beskriver hur emojis upplevs påverka innebörden av budskapet. Det sista temat Emojis ersätter känslors ord beskriver effektiviteten genom emojis i textlig kommunikation men som också kan resultera i en överdrift. Emojis i textlig kommunikation är av stor betydelse då effekten av att använda den upplevs som möjligt att hantera relationer relationer och sociala roller. Hantering av relationer och sociala roller är viktigt för att stärka självkänslan och bibehålla självbilden. / The purpose of the study was to investigate people`s experiences of emojis in textual communication. The study used qualitative method for the study in the form of Braun and Clarkes (2006) Thematic analysis. The data collection consisted of three focus groups with four participants in each group, of witch eleven particpants were woman and one particpant was male. The Thematic analysis generated three themes: First theme The secuarity and uncertainty of the emojicode describes the particpants sense of security through the use of specific emojis that create a code to manage different relationship. The emojicode can also create uncertainty as a relationship developes because emojis can be interpreted in different ways. Other themes Emoji reinforce or mitigate messages describe how emojis are perceived to affect the meaning of the message. The last theme of Emoji replaces the words of emotion describing the effectiveness of emojis in textual communication but can also result in an exaggeration. Emoji in textual communication is of great importance as the effect of using them is perceived as possible to manage relationships and social roles. Managing relationships and social roles is important for strengthening self-esteem and maintaining self-image.

Les signaux multicanaux sont des signaux captés à travers plusieurs canaux ou capteurs, portant chacun un mélange de sources, une partie desquelles est connue alors que le reste des sources reste inconnu. Les méthodes à l’aide desquelles l’isolement ou la séparation des sources est accomplie sont connues par les méthodes de séparation de sources en général, et si le degré d’inconnu est large, par la séparation aveugle des sources (SAS). Cependant, la SAS appliquée aux signaux multicanaux est en fait plus facile de point de vue mathématique que l’application de la SAS sur des signaux monocanaux, ou un seul capteur existe et tous les signaux arrivent au même point pour enfin produire un mélange de sources inconnues. Tel est le domaine de cette thèse. Nous avons développé une nouvelle technique de SAS : une combinaison de plusieurs méthodes de séparation et d’optimisation, basée sur la factorisation non-négative des matrices (NMF). Cette méthode peut être utilisée dans de nombreux domaines comme l’analyse des sons et de la parole, les variations de la bourse, et les séismographes. Néanmoins, ici, les signaux de force de réaction de terre verticaux (VGRF) monocanaux d’un groupe d’athlètes coureurs d’ultra-marathon sont analysés et séparés pour l’extraction du peak passif du peak actif d’une nouvelle manière adaptée à la nature de ces signaux. Les signaux VGRF sont des signaux cyclo-stationnaires caractérisés par des double-peaks, chacun étant très rapide et parcimonieux, indiquant les phases de course de l’athlète. L’analyse des peaks est extrêmement importante pour déterminer et prédire la condition du coureur : problème physiologique, problème anatomique, fatigue etc. De plus, un grand nombre de chercheurs ont prouvé que l’impact du pied postérieur avec la terre d’une manière brutale, l’analyse de ce phénomène peut nous ramener à une prédiction de blessure interne. Ils essayent même d’adopter une technique de course - Non-Heel-strike Running (NHS) - par laquelle ils obligent les coureurs à courir sur le pied-antérieur seulement. Afin d'étudier ce phénomène, la séparation du peak d’impact du VGRF permet d'isoler la source portant les informations patho-physiologiques et le degré de fatigue. Nous avons introduit de nouvelles méthodes de prétraitement et de traitement des signaux VGRF pour remplacer le filtrage de bruit traditionnel utilisé partout, et qui peut parfois détruire les peaks d’impact qui sont nos sources à séparer, base sur le concept de soustraction spectrale pour le filtrage, utilisée avec les signaux de parole, après l’application d’un algorithme d’échantillonnage intelligent et adaptatif qui décompose les signaux en pas isolés. Une analyse des signaux VGRF en fonction du temps a été faite pour la détection et la quantification de la fatigue des coureurs durant les 24 heures de course. Cette analyse a été accomplie au domaine fréquentiel/spectral où nous avons détecté un décalage clair du contenu fréquentiel avec la progression de la course indiquant la progression de la fatigue. Nous avons défini les signaux cyclosparse au domaine temporel, puis traduit cette définition à son équivalent au domaine temps-fréquence utilisant la transformée Fourier a court-temps (STFT). Cette représentation a été décomposée à travers une nouvelle méthode que l’on a appelé Cyclosparse Non-negative Matrix Factorisation (Cyclosparse-NMF), basée sur l’optimisation de la minimisation de la divergence Kullback-Leibler (KL) avec pénalisation liée à la périodicité et la parcimonie des sources, ayant comme but final d’extraire les sources cyclosparse du mélange monocanal appliquée aux signaux VGRF monocanaux. La méthode a été testée sur des signaux analytiques afin de prouver l’efficacité de l’algorithme. Les résultats se sont avéré satisfaisants, et le peak impact a été séparé du mélange VGRF monocanal. / The purpose of the presented work is to develop a customized Single-channel Blind Source Separation technique that aims to separate cyclostationary and transient pulse-like patterns/sources from a linear instantaneous mixture of unknown sources. For that endeavor, synthetic signals of the mentioned characteristic were created to confirm the separation success, in addition to real life signals acquired throughout an experiment in which experienced athletes were asked to participate in a 24-hour ultra-marathon in a lab environment on an instrumented treadmill through which their VGRF, which carries a cyclosparse Impact Peak, is continuously recorded with very short discontinuities during which blood is drawn for in-run testing, short enough not to provide rest to the athletes. The synthetic and VGRF signals were then pre-processed, processed for Impact Pattern extraction via a customized Single-channel Blind Source Separation technique that we termed Cyclo-sparse Non-negative Matrix Factorization and analyzed for fatigue assessment. As a result, the Impact Patterns for all of the participating athletes were extracted at 10 different time intervals indicating the progression of the ultra-marathon for 24 hours, and further analysis and comparison of the resulting signals proved major significance in the field of fatigue assessment; the Impact Pattern power monotonically increased for 90% of the subjects by an average of 24.4 15% with the progression of the ultra-marathon during the 24-hour period. Upon computation of the Impact Pattern separation algorithm, fatigue progression showed to be manifested by an increase in reliance on heel-strike impact to push to the bodyweight as a compensation for the decrease in muscle power during propulsion at toe-off. This study among other presented work in the field of VGRF processing forms methods that could be implemented in wearable devices to assess and track runners’ gait as a part of sports performance analysis, rehabilitation phase tracking and classification of healthy vs. unhealthy gait.

La navigation des axones sur de longues distances est jalonnée de zones de choix, entraînant des changements de direction pour suivre des trajectoires hautement stéréotypées. Dans ce modèle de guidage séquentiel, chaque étape est vue comme essentielle à la suivante. De façon intrigante, quelques exemples suggèrent que le suivi strict de la trajectoire puisse être dispensable pour que les axones atteignent leur destination finale. Nous nous sommes intéressés à cette capacité trajectoire indépendante des axones à localiser leur cible. Pour ce faire, nous avons utilisé deux populations neuronales de la moelle épinière ayant des cibles diamétralement opposées dans l'organisme : les interneurones dorsaux, qui projettent dans le système nerveux central, et les motoneurones ventraux, qui ciblent les muscles en périphérie. Après avoir été déplacés chirurgicalement dans des embryons de poulet, ces deux populations de neurones envoient des axones vers leurs territoires cibles qu'ils atteignent par des trajectoires inédites. Ces observations suggèrent l'existence d'un système de guidage global délivrant aux axones des informations spatiales à large échelle. Outre les signaux moléculaires de guidage bien connus, les signaux bioélectriques sont également des candidats intéressants pour remplir cette fonction. Des champs électriques (CE) ont été détectés dans les embryons en développement et sont connus pour être des vecteurs d'information spatiale. Nous avons testé sur des neurones en culture si des CE comparables à ceux mesurés pendant le développement embryonnaire pourraient guider l'élongation des axones moteurs et d'interneurones dorsaux de poulet. Nous avons trouvé que les deux types d'axones s'orientent en direction de la cathode (-) dans un CE. Cependant, ils présentent des sensibilités significativement différentes aux CE, qui pourraient contribuer à des choix de trajectoires différents in vivo. Ensuite, nous avons observé un effet inhibiteur de la Concanavaline A (ConA) sur la réponse des axones aux champs, indiquant un rôle des récepteurs membranaires connus pour lier la ConA. Nous avons donc réalisé un screen pharmacologique sur des pompes et des canaux ioniques qui se lient à la ConA, conduisant à l'identification des pompes Na+/K+ ATPases comme des candidats prometteurs. Des expériences préliminaires d'invalidation des sous-unités de ces pompes suggèrent qu'elles contribuent à la réponse aux CE et à la navigation axonale in vitro et in vivo. Finalement, nos résultats apportent une vision nouvelle des mécanismes assurant la fidélité et la résilience du guidage axonal, et révèlent la contribution méconnue des signaux bioélectriques et des pompes Na+/K+ ATPases au développement neuronal / Long distance navigation of axons is marked by choice points, instructing highly stereotyped directional changes of axon trajectories. In this stepwise model, each step is thought to be essential for the next one, but intriguingly, examples suggest that pathway experience can be dispensable for axons to reach their final destination. We investigated pathway-independent ability of axons to locate their target, using two populations of spinal cord neurons having drastically different target location in the organism: the dorsal interneurons, which target the central nervous system and ventral motoneurons, which target muscles. After grafting these neurons at ectopic positions in the chicken embryo, both neuron-types were observed to form axons which, remarkably, oriented towards and reached appropriate targets. This suggests that, in the embryo, an overall guidance information might exist that enables the axons to locate positions over large scales. Beside well-studied chemical cues, bioelectric signals are attractive candidates for this function. Electric Fields (EF) were detected in the embryo and reported to encode spatial information. Thus, using in vitro set-ups, we investigated whether EFs in the range of the ones measured in the embryo could influence the navigation of chick motor and dorsal interneuron axons. We found that both axon subsets orient parallel to EFs. Yet, they significantly exhibited different sensitivities, which could contribute to elicit different trajectory choices in vivo. Next, we found that Concanavalin A (ConA) could block axon response to EF, supporting a role of cell surface receptors known to bind to ConA. Thus, we performed a pharmacological screening on ion channels and pumps that bind ConA and identified Na+/K+ ATPases as promising candidates. Preliminary knock-down experiments targeting Na+/K+ ATPases subunits suggest their contribution to CE response and axon navigation in vitro and in vivo. Collectively, our findings should provide novel insights into the mechanisms ensuring axon guidance fidelity and resilience and reveal unknown contributions of bioelectric signals and Na+/K+ ATPases during neuronal development

The study of the spatial aspects of multipath in wireless communications environments is an increasingly important addition to the study of the temporal aspects in the search for ways to increase the utilization of the available wireless channel capacity. Traditionally, multipath has been viewed as an encumbrance in wireless communications, two of the major impairments being signal fading and intersymbol interference. However, recently the potential advantages of the diversity offered by multipath rich environments in multiuser communications have been recognised. Space time coding, for example, is a recent technique which relies on a rich scattering environment to create many practically uncorrelated signal transmission channels. Most often, statistical models have been used to describe the multipath environments in such applications. This approach has met with reasonable success but is limited when the statistical nature of a field is not easily determined or is not readily described by a known distribution.¶ Our primary aim in this thesis is to probe further into the nature of multipath environments in order to gain a greater understanding of their characteristics and diversity potential. We highlight the shortcomings of beamforming in a multipath multiuser access environment. We show that the ability of a beamformer to resolve two or more signals in angle directly limits its achievable capacity.¶ We test the probity of multipath as a source of spatial diversity, the limiting case of which is co-located users. We introduce the concept of separability to define the fundamental limits of a receiver to extract the signal of a desired user from interfering users’ signals and noise. We consider the separability performances of the minimum mean square error (MMSE), decorrelating (DEC) and matched filter (MF) detectors as we bring the positions of a desired and an interfering user closer together. We show that both the MMSE and DEC detectors are able to achieve acceptable levels of separability with the users as close as λ/10.¶ In seeking a better understanding of the nature of multipath fields themselves, we take two approaches. In the first we take a path oriented approach. The effects on the variation of the field power of the relative values of parameters such as amplitude and propagation direction are considered for a two path field. The results are applied to a theoretical analysis of the behaviour of linear detectors in multipath fields. This approach is insightful for fields with small numbers of multipaths, but quickly becomes mathematically complex.¶ In a more general approach, we take a field oriented view, seeking to quantify the complexity of arbitrary fields. We find that a multipath field has an intrinsic dimensionality of (πe)R/λ≈8.54R/λ, for a field in a two dimensional circular region, increasing only linearly with the radius R of the region. This result implies that there is no such thing as an arbitrarily complicated multipath field. That is, a field generated by any number of nearfield and farfield, specular and diffuse multipath reflections is no more complicated than a field generated by a limited number of plane waves. As such, there are limits on how rich multipath can be. This result has significant implications including means: i) to determine a parsimonious parameterization for arbitrary multipath fields and ii) of synthesizing arbitrary multipath fields with arbitrarily located nearfield or farfield, spatially discrete or continuous sources. The theoretical results are corroborated by examples of multipath field analysis and synthesis.

This study focuses on the experiences of a group of educators engaged in a professional development program by distance education in Papua New Guinea. The participants in this study have been keeping professional journals, for periods of up to three years, about their experiences of distance education. Their discourses have been used to form a ‘connected group’ of research participants, who use an action framework to focus on problematic issues surrounding distance education in Papua New Guinea. It is a piece of research, framed by critical theory, and characterised by participation, collaboration, reflexivity, reciprocity and empowerment. The process of the study is based in dialogue, and takes the view that research is constituted of a transformative perspective, which alters the way research participants understand the multiple realities in which they live and work, arid ultimately results in improvements in their lived experiences. The nature of the methodology privileges Voice' and a discourse of difference from each participant which contributes to the problematic nature of the study. The study has concerned itself, increasingly, with issues of power and control in the research process, and this has resulted in significant changes in the research as participants have become more conscious of issues such as distance, dialogue and difference. The study has evolved over a period of time in significant ways, and evidence is available that teachers in Papua New Guinea, despite structural and pedagogical barriers, are critically reflective and are able to transform their practice in ways which are consistent with social, cultural and political contexts in which they live and work. A number of 'local1 theories about research and distance education in Papua New Guinea are developed by the participants as they become informed about issues during the research. The practice of distance education and professional development, at personal and institutional levels, undergoes reconstruction during the life of the research and the study 'signals' other ways in which distance education and professional development may be reconstructed in Papua New Guinea.

To many, high-frequency (HF) radio communications is obsolete in this age of long distance satellite communications and undersea optical fiber. Yet despite this, the HF band is used by defence agencies for backup communications and spectrum surveillance, and is monitored by spectrum management organizations to enforce licensing. Such activity usually requires systems capable of locating distant transmitters, separating valid signals from interference and noise, and recognizing signal modulation. Research presented here targets the latter issue. The ultimate aim is to develop robust algorithms for automatic modulation recognition of real HF signals, where real means signals propagating by multiple ionospheric modes with co-channel signals and non- Gaussian noise. However, many researchers adopt Gaussian noise models for signals for the sake of convenience at the cost of accuracy. Furthermore, literature describing the probability density function (PDF) of HF noise does not abound. So an additional aim of this research is measurement of the PDF of HF noise. A simple empirical technique, not found in the literature, is described that supports the hypothesis that HF noise is generally not Gaussian. In fact, the probability density function varies with the time of day, electromagnetic environment, and state of the ionosphere. Key contributions of this work relate to the statistics of HF noise and the discrimination of real HF signals via three signal features. Through two unique experiments, the density function of natural HF noise is found to closely follow a Bi-Kappa distribution. This distribution can model natural and man-made HF noise through a single control parameter. Regarding signal features, the coherence function is found to be a brute-force technique suitable only for hard (not soft) decisions. A novel application of an entropic distance measure proves able to separate four real HF signals based on their modulation types. And, an estimator for signal-to-noise (SNR) ratio is shown to provide reasonable measures of SNR for the same real HF signals. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1330848 / Thesis (Ph.D.) - University of Adelaide, School of Electrical and Electronic Engineering, 2008

<p>In modern medicine, the measurement of electrophysiological signals play a key role in health monitoring and diagnostics. Electrical activity originating from our nerve and muscle cells conveys real-time information about our current health state. The two most common and actively used techniques for measuring such signals are electrocardiography (ECG) and electroencephalography (EEG).</p><p>These signals are very weak, reaching from a few millivolts down to tens of microvolts in amplitude, and have the majority of the power located at very low frequencies, from below 1 Hz up to 40 Hz. These characteristics sets very tough requirements on the electrical circuit designs used to measure them. Usually, measurement is performed by attaching electrodes with direct contact to the skin using an adhesive, conductive gel to fixate them. This method requires a clinical environment and is time consuming, tedious and may cause the patient discomfort.</p><p>This thesis investigates another method for such measurements; by using a non-contact, capacitively coupled sensor, many of these shortcomings can be overcome. While this method relieves some problems, it also introduces several design difficulties such as: circuit noise, extremely high input impedance and interference. A capacitively coupled sensor was created using the bottom layer of a printed circuit board (PCB) as a capacitor plate and placing it against the signal source, that acts as the opposite capacitor plate. The PCB solder mask layer and any air in between the two acts as the insulator to create a full capacitor. The signal picked up by this sensor was then amplified by 60 dB with a high input impedance amplifier circuit and further conditioned through filtering.</p><p>Two measurements were made of the same circuit, but with different input impedances; one with 10 MΩ and one with 10 GΩ input impedance. Additional filtering was designed to combat interference from the main power lines at 50 Hz and 150 Hz that was discovered during initial measurements. The circuits were characterized with their transfer functions, and the ability to amplify a very low-level, low frequency input signal. The results of these measurements show that high input impedance is of critical importance for the functionality of the sensor and that an input impedance of 10 GΩ is sufficient to produce a signal-to-noise ratio (SNR) of 9.7 dB after digital filtering with an input signal of 25 μV at 10 Hz.</p>