The aim of this master's thesis is suggestion and following realization of voice transmission over the local network equipment and a description of used circuits and solutions in terms of hardware and software. This thesis deals with digitization of low-frequency signals, the structure of IP and UDP protocols, implementation of TCP/IP stack cIPS

The contents of this thesis is design of audio power amplifier in Class D with fully digital control and remote control and is divided into two parts . The first part is devoted to the basic principles and theory of key elements of the entire amplifier. The second part consists of a complete description of the design and construction of a power amplifier, digital control with remote control, a spectrum analyzer, equalizer, preamp VU meters and complete power supply. Each proposal contains a detailed analysis of the solutions supported by simulations and software. For individual parts have been completely measured p arameters.

L’objectif d’un traitement antirétroviral (ARV) est d’obtenir une charge virale VIH plasmatiqueindétectable afin de réduire la morbi-mortalité associée au VIH.La résistance du virus aux ARV est un facteur de risque d’échec virologique (EV). Les testsgénotypiques de résistance par séquençage classique (méthode de Sanger) ne permettent pas dedétecter les virus porteurs de mutations de résistance (MR) présents à taux minoritairereprésentant moins de 20% de la population virale plasmatique. Dans notre étude (cohorteANRS CO3), l’utilisation de l’ultra-deep sequencing (UDS) a permis de détecter 1.4 fois plusde MR avant traitement et 1.3 fois plus à l’EV en comparaison à la technique de séquençageclassique, confirmant la haute sensibilité de l’UDS pour la détection des MR. Les MRminoritaires détectées uniquement par UDS augmentaient la résistance génotypique du virus autraitement ARV chez 4% des patients à l’initiation du traitement et 21% des patients à l’EV.Les conséquences des épisodes de charges virales de faible niveau persistantes (CVF) entre 50et 200 copies/ml (CVF50-200) ne sont pas clairement établies du fait de l’insuffisance dedonnées dans la littérature. Dans nos études de cohortes (cohortes ANRS CO3 et ART-CC), 4-9% des patients ont présenté au moins un épisode de CVF50-200. La survenue d’une CVF50-200 était associée à un risque plus de 2 fois plus élevé d’EV>200 copies/ml, quels que soient ladurée de la CVF, l’historique de traitement ou le traitement ARV lors de la CVF50-200(régimes comportant des INNTI ou des IP/r). La survenue d’une CVF n’était pas associée à lasurvenue d’un évènement classant SIDA ni au décès, avec toutefois un suivi médian de 3 ans. / The goal of antiretroviral therapy (ART) is to reach undetectable plasma HIV viral load in orderto reduce HIV-related morbidity and mortality.The presence of ART-resistant virus can compromise the efficiency of these treatments,resulting in virological failure (VF). Standard genotyping by Sanger sequencing (SS) usedcurrently in clinical practice cannot detect low-frequency viral variants harbouring drugresistance associated mutations (DRM) representing less than 20% of the viral population. Inour study, the use of ultra-deep sequencing (UDS) allowed us to detect 1.4-fold more DRMsbefore ART and 1.3-fold more DRMs at VF compared to SS, confirming the high sensitivity ofUDS for the detection of DRMs. The low-frequency DMRs detected only by UDS modified thegenotypic resistance of the virus to the prescribed treatment for 4% of the patients before ARTinitiation and for 21% of the patients at VF.The impact of persistent low-level viremia (LLV) between 50 and 200 copies/ml (LLV50-200)remains uncertain due to the lack of controlled comparison data. In our cohort studies (ANRSCO3 and ART-CC cohorts), 4-9% of HIV-infected patients experienced at least one episode ofLLV50-200. LLV50-200 was strongly associated with a twice higher risk of VF>200copies/ml,independently of the duration of LLV, the history of treatment or the type of ART regimen atLLV (NNRTI or PI-based regimens). LLV was not associated with AIDS event or death witha median follow-up of only 3 years.

Lors d’essais de feux d’hydrocarbures liquides dans le dispositif DIVA de l’IRSN, un phénomène oscillatoire basse-fréquence (BF), a été observé. Ce phénomène se manifeste par des fluctuations importantes de la pression dans le local, qui peuvent conduire à une perte de confinement et ainsi favoriser la propagation du feu et le rejet de polluants au-delà du local. Il s’accompagne de déplacements intermittents de la flamme hors du bac. L’étude fine de ce phénomène oscillatoire a tout d’abord consisté à concevoir une maquette à l’échelle 1:4 du dispositif DIVA dans lequel nous avons fait varier différents paramètres. L’analyse des résultats obtenus nous a permis d’identifier différents régimes de combustion, de décrire les mécanismes responsables de l’apparition des oscillations BF et de caractériser les propriétés de ces oscillations (fréquence et amplitude). L’occurrence et la persistance des oscillations BF dépendent essentiellement de l’équilibre, plus ou moins précaire, entre la quantité d’air disponible pour la combustion et le débit d’évaporation du combustible résultant des flux thermiques reçus à sa surface. Une étude numérique exploratoire utilisant le code CFD SAFIR a été ensuite conduite en utilisant le débit d’évaporation mesuré expérimentalement, puis en le calculant à l’aide d’un modèle d’évaporation. Si le code ne permet pas de décrire correctement le déplacement de la flamme hors du bac, il reproduit de façon satisfaisante le comportement oscillatoire BF du feu, en particulier sa fréquence dominante. / During liquid hydrocarbon fire tests in the DIVA device of IRSN, a low-frequency (LF) oscillatory phenomenon, was observed. This phenomenon manifests itself by large variations of the average pressure in the room, which can lead to a loss of confinement and thus promote the spread of fire and the release of pollutants beyond the local. It is accompanied by intermittent displacements of the flame outside the fuel pan. The fine study of this phenomenon consisted in designing a 1:4 scale model of the DIVA device, allowing us to carry out a very large number of tests, varying some parameters. The analysis of the results obtained allowed us to identify different combustion regimes, to describe the mechanisms responsible for the appearance of the LF oscillations, and to characterize the properties of these oscillations (frequency and amplitude). The occurrence and persistence of LF oscillations essentially depend on the precarious equilibrium between the supply of fresh air and the supply of fuel vapors which results from the heat flux received at its surface. An exploratory numerical study using the CFD code SAFIR was then conducted using both the experimentally measured evaporation rate and that calculated using an evaporation model. The model does not correctly describe the displacements of the flame outside the fuel pan. However, it satisfactorily reproduces the LF oscillatory fire behavior, especially its dominant frequency.

Les transistors à haute mobilité d’électrons (HEMTs) en Nitrure de Gallium (GaN) s’affirment aujourd’hui comme une technologie essentielle à l’amplification de puissance à haute fréquence. Les HEMTs GaN étudiées et développées reposent essentiellement sur une hétérostructure AlGaN/GaN mais une alternative à base d’une barrière composée en InAlN, réduisant les contraintes sur les mailles cristallographiques de l’ensemble, est étudiée par certains laboratoires. Ce manuscrit de thèse rapporte une étude des potentialités de la filière HEMT InAlN/GaN développée au III-V Lab, en s’intéressant tout particulièrement aux effets de pièges induits par des défauts présents au sein de la structure. Une méthode de détection de ces défauts est proposée, basée sur la mesure de paramètres [S] en basse fréquence. Un modèle de HEMT InAlN/GaN électrothermique comprenant la contribution des effets de pièges est rapporté et sert de base à la conception d’un amplificateur de puissance en technologie MMIC, fonctionnant en bande Ka, présenté au dernier chapitre. / Nowadays, High Electron Mobility Transistors (HEMTs) in Gallium Nitride (GaN) take the lead in power amplification at microwave frequencies. Most of the studies and developments on those HEMTs concern AlGaN/GaN structures but alternative transistors with an InAlN barrier, which reduces the strain in the crystal lattice of the whole structure, are investigated by few laboratories. This thesis presents some advanced studies on the new InAlN/GaN HEMT developed by the III-V Lab, focusing on the trapping phenomena induced by defects inside the crystal structure. A new method for the characterization of these defects, based on low-frequency S-Parameters measurements, is proposed. Furthermore, a non-linear electro thermal model including trapping effects for an InAlN/GaN HEMT is detailed and used to design a MMIC power amplifier for Ka-band applications.

Les transistors à haute mobilité d’électrons (HEMTs) en nitrure de gallium (GaN) s’affirment comme les candidats prometteurs pour les futurs équipements à micro-ondes - tels que les amplificateurs de puissance à état solide (SSPA), grâce à leurs excellentes performances. Une première démonstration d'émetteur en technologie GaN-MMIC a été développée et embarquée dans la mission spatiale PROBA-V. Mais cette technologie souffre encore des effets de pièges par des défauts présents au sein de la structure. L’objectif de ce travail est donc l'étude d’effets de pièges et des aspects de fiabilité des transistors de puissance GH50 pour des applications en bande C. Un protocole d’investigation des phénomènes de pièges est présenté, qui permet l’étude des dynamiques des effets de pièges du mode de fonctionnement DC au mode de fonctionnement radiofréquence, basé sur la combinaison des mesures IV impulsionnelles, des mesures de transitoires du courant de drain avec des impulsions DC et RF et des mesures de paramètres [S] en basse fréquence. Un modèle de HEMT AlGaN/GaN non-linéaire électrothermique est présenté, incluant un nouveau modèle thermique de pièges restituant le comportement dynamique de ces pièges et leurs variations en température afin de prédire correctement les performances en conditions réelles de fonctionnement RF. Enfin, une méthodologie temporelle pour l’évaluation de la fiabilité et de limites réelles d'utilisation de transistors dans l'amplificateur de puissance RF en régime d’overdrive (très forte compression), basée sur la mesure monitorée de Formes d'Onde Temporelles (FOT), est proposée. / GaN-based high electron mobility transistors (HEMTs) are promising candidates for future microwave equipment, such as new solid state power amplifiers (SSPAs), thanks to their excellent performance. A first demonstration of GaN-MMIC transmitter has been developed and put on board the PROBA-V mission. But this technology still suffers from the trapping phenomena, principally due to lattice defects. Thus, the aim of this research is to investigate the trapping effects and the reliability aspects of the GH50 power transistors for C-band applications. A new trap investigation protocol to obtain a complete overview of trap behavior from DC to radio-frequency operation modes, based on combined pulsed I/V measurements, DC and RF drain current measurements, and low-frequency dispersion measurements, is proposed. Furthermore, a nonlinear electro-thermal AlGaN/GaN model with a new additive thermal-trap model including the dynamic behavior of these trap states and their associated temperature variations is presented, in order to correctly predict the RF performance during real RF operating conditions. Finally, an advanced time-domain methodology is presented in order to investigate the device’s reliability and to determine its safe operating area. This methodology is based on the continual monitoring of the RF waveforms and DC parameters under overdrive conditions in order to assess the degradation of the transistor characteristics in the RF power amplifier.

Supplying wireless sensors from ambient energy is nowadays highly demanded for a higher flexibility of use and low system maintenance costs. Vibration sources are thereby especially attractive due to their availability and the relatively high energy density they can provide. The aim of this work is to realize a hybrid energy converter for vibration sources having low amplitude and low frequency. The idea is to combine two diverse harvesters to realize a higher energy density and at the same time to improve the converter reliability. We focus on the design, modeling, and test of the hybrid vibration converter. For an appropriate converter design, the vibration profiles of several ambient vibration sources are characterized. The results show that the typical frequency and acceleration ranges are between 5 Hz to 60 Hz and 0.1 g to 1.5 g respectively. The proposed converter is based on the magnetoelectric (ME) and electromagnetic (EM) principles. These two principles can be easily combined within almost the same volume, because they generate energy form the same varying magnetic field coupled to the mechanical vibration of the source. Thereby, the energy density is improved as the ME converter is incorporated within the relatively large coil housing of the electromagnetic converter. The proposed converter is based on the use of a magnetic spring instead of the typically used mechanical springs, which applies the repulsive force to the seismic mass of the converter. The applied vibration is transmitted to the converter based on the magnetic spring principle instead of the conventional mechanical springs. Due to the nonlinearity of the magnetic spring, the converter is able to operate for a frequency bandwidth instead of resonant frequency which is the case while using a mechanical spring. Hence, this leads to realize a high converter efficiency even under random vibrations characterized by frequency bandwidth. As well, using magnetic spring principle enables to adjust the resonant frequency of the converter relative to the applied vibration source easily by just adjusting the moving magnet size. For the converter design, a parametric study is conducted using finite element analysis. Two main criteria are thereby taken into account, which are the compactness and the efficiency of the converter. Parameters affecting these two criteria are classified in mechanical, electromagnetic and magnetoelectric parameters. Results show that the combination of the EM and ME principles leads to an improvement of the energy output compared to a single EM or ME converter. The novel hybrid converter is realized and tested under harmonic and real vibration profiles. It comprises two main parts: A fixed part, where the coils and the ME transducer are fixed in order to ensure a good reliability of the converter by avoiding wire movements. A moving part, where the moving magnet of the magnetic spring and the magnetic circuit are placed. The presented converter is reliable and compact, which is able to harvest energy with a maximum output power density of 0.11 mW/cm³ within a frequency bandwidth of 12 Hz for a resonance frequency of 24 Hz under an applied harmonic vibration with an amplitude of 1 mm. / Die Versorgung von drahtlosen Sensoren aus der Umgebungsenergie ermöglicht heutzutage eine hohe Einsatzflexibilität und die Senkung des Systemwartungsaufwands. Schwingungsquellen sind aufgrund ihrer Verfügbarkeit und der damit erreichbaren Energiedichte besonders attraktiv. Ziel dieser Arbeit ist es, einen hybriden Energiewandler für Vibrationsquellen mit geringer Amplitude und niedriger Frequenz zu realisieren. Der Ansatz dabei ist, zwei verschiedene Wandler zu kombinieren, um eine höhere Energiedichte zu erreichen und die Zuverlässigkeit zu verbessern. Der Entwurf konzentriert sich auf die Modellierung und den Test des hybriden Vibrationswandlers. Für einen geeigneten Wandlerentwurf werden die Schwingungsprofileigenschaften mehrerer Umgebungsschwingungsquellen untersucht. Die Ergebnisse zeigen, dass die typische Frequenz zwischen 5 Hz und 60 Hz und der Beschleunigungsbereich zwischen 0,1 g und 1,5 g liegen. Der vorgeschlagene Wandler kombiniert das magnetoelektrischen (ME) Prinzip mit dem elektromagnetischen (EM) Prinzip. Diese beiden Prinzipien können innerhalb des fast gleichen Volumens leicht integriert werden, da sie Energie aus der Variation des gleichen Magnetfeldes, das mit der mechanischen Schwingung gekoppelt ist, erzeugen können. Dadurch wird die Energiedichte verbessert, da der ME-Wandler in das relativ große Spulengehäuse des elektromagnetischen Wandlers eingesetzt werden kann. Darüber hinaus basiert der vorgeschlagene Wandler auf der Verwendung von Magnetfedern, um die Repulsivkraft auf die seismische Masse zu realisieren. Aufgrund der Nichtlinearität der Magnetfeder, kann der Wandler in einem breiteren Frequenzbereich betrieben werden, anstatt nur bei der Resonanzfrequenz, wie es bei der Verwendung einer mechanischen Feder der Fall ist. Dies führt dazu, dass der Wandler auch bei zufälligen breitbandigen Schwingungsquellen effizient betrieben werden kann. Darüber hinaus ermöglicht die Verwendung des Magnetfederprinzips eine einfache Einstellung der Resonanzfrequenz des Wandlers in Bezug auf die Schwingungsquelle, durch Einstellen der Größe des beweglichen Magneten. Für den Wandlerentwurf wird eine Parameterstudie mit Hilfe der Finite-Elemente-Analyse durchgeführt. Zwei Hauptkriterien werden dabei berücksichtigt: Die Kompaktheit und die Energieeffizienz des Wandlers. Parameter die diese beiden Kriterien beeinflussen, können in mechanische, elektromagnetische und magnetoelektrische unterteilt werden. Die Ergebnisse haben gezeigt, dass die Kombination der EM- und ME-Prinzipien zu einer Verbesserung der Energieausbeute im Vergleich zu einem einzelnen EM- oder ME-Wandler geführt hat. Der neuartige Hybrid-Wandler wurde realisiert und unter harmonischen und realen Schwingungsprofilen getestet. Der Wandler besteht aus zwei Hauptteilen: Ein festes Teil, an dem die Spulen und der ME-Wandler befestigt sind, um eine hohe Zuverlässigkeit zu gewährleisten indem auf einen beweglichen Draht verzichtet wird, und ein bewegliches Teil, das sich aus einem beweglichen Magneten zusammensetzt. Der vorgestellte Wandler ist zuverlässig, kompakt und in der Lage, Energie mit einer maximalen Ausgangsleistungsdichte von 0,11 mW/cm 3 und einer Bandbreite von 12 Hz bei einer Resonanzfrequenz von 24 Hz unter einer angelegten harmonischen Schwingung mit einer Amplitude von 1 mm zu gewinnen.

Infant hearing screening (IHS) programs are not yet widespread in developing countries, such as South Africa. In order to ensure that the benefits of early hearing detection and intervention (EHDI) programs reach all infants, initial recommendations for the implementation of IHS programs in South Africa have been made by the Year 2002 Hearing Screening Position Statement by the Health Professions Council of South Africa. One of the platforms recommended for IHS in South Africa is the neonatal intensive care unit (NICU). South African NICU infants are at an increased risk for hearing loss, resultant of their high-risk birth histories, as well as the prevalence of context-specific environmental risk factors for hearing loss. There is currently a general scarcity of contextual data regarding the prevalence of risk indicators for hearing loss, and the prevalence of auditory impairment in the South African NICU population. The objective of this study was to describe an IHS program for NICU infants at a secondary hospital in Gauteng, South Africa. A quantitative descriptive research design was used to report on a cohort of 129 NICU infants followed up during a 29 month period. The objective of the study was achieved by describing the sample of infants in terms of the presence of specific risk indicators for hearing loss, the efficiency of the IHS program, and the incidence of auditory pathologies. Infants received their initial hearing screening as part of their medical and developmental follow-up visit at the hospital at three months of age. Routine rescreening visits were scheduled three monthly, whilst infants who failed the hearing screening were requested to return after three weeks for a follow-up. A data collection sheet was used to collect biographical information and risk indicators for hearing loss. Immittance measurements were recorded in the form of high-frequency and low-frequency tympanometry. Distortion product otoacoustic emissions (DPOAE) and automated auditory brainstem responses (AABR) were recorded, as well as diagnostic auditory brainstem responses (ABR) in cases where infants referred the screening protocol. Results revealed that environmental risk factors present in this sample included poor maternal education levels and prenatal HIV/AIDS exposure. At least 32% of mothers participating in this study did not complete high school. Prenatal HIV/AIDS exposure was present in at least 21% of the current sample of infants. The screening coverage rate fell short of the 95% benchmark set by the Joint Committee on Infant Hearing (JCIH, 2000). A 67% coverage rate was achieved with AABR screening, and an 88% coverage rate was achieved with DPOAE screening. 93% of infants had immittance screening performed on their initial visit to the IHS program. According to the Fisher’s two-sided exact test and the logistic regression procedure, high frequency tympanometry proved to be more effective than low frequency tympanometry, when assessing the middle ear functioning of infants younger than seven months when compared with DPOAE results. Normative pressure and admittance data was compiled for the use of high frequency tympanometry in NICU infants. Poor follow-up rates were recorded for both routine and non-routine visits, but are expected to improve over time. Furthermore, results indicated a high incidence of hearing impairment. Permanent congenital hearing loss was identified in 3% (n=4) of the sample. Half of these presented with sensorineural hearing loss, whilst the other half had auditory neuropathy. The incidence of auditory impairment is estimated to be 3.75% if the percentage of infants who did not return for follow-up is taken into account. A high incidence of middle ear pathology was recorded, with an incidence rate of 60.4%, including bilateral and unilateral middle ear pathology. The high prevalence of auditory impairment in South African NICU infants, and the lack of widespread IHS programs, indicates that many vulnerable infants are being the denied the benefits of early identification of and intervention for hearing loss. The implementation of widespread IHS programs in South Africa is therefore essential, in order to ensure that all South African infants receive the benefits of EHDI programs. / Dissertation (MCommunication Pathology)--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / Reliable detection of low-frequency single nucleotide variants (SNVs) carries great significance in many applications. In cancer genetics, the frequencies of somatic variants from tumor biopsies tend to be low due to contamination with normal tissue and tumor heterogeneity. Circulating tumor DNA monitoring also faces the challenge of detecting low-frequency variants due to the small percentage of tumor DNA in blood. Moreover, in population genetics, although pooled sequencing is cost-effective compared with individual sequencing, pooling dilutes the signals of variants from any individual. Detection of low frequency variants is difficult and can be cofounded by multiple sources of errors, especially next-generation sequencing artifacts. Existing methods are limited in sensitivity and mainly focus on frequencies around 5%; most fail to consider differential, context-specific sequencing artifacts. To face this challenge, we developed a computational and experimental framework, RareVar, to reliably identify low-frequency SNVs from high-throughput sequencing data. For optimized performance, RareVar utilized a supervised learning framework to model artifacts originated from different components of a specific sequencing pipeline. This is enabled by a customized, comprehensive benchmark data enriched with known low-frequency SNVs from the sequencing pipeline of interest. Genomic-context-specific sequencing error model was trained on the benchmark data to characterize the systematic sequencing artifacts, to derive the position-specific detection limit for sensitive low-frequency SNV detection. Further, a machine-learning algorithm utilized sequencing quality features to refine SNV candidates for higher specificity. RareVar outperformed existing approaches, especially at 0.5% to 5% frequency. We further explored the influence of statistical modeling on position specific error modeling and showed zero-inflated negative binomial as the best-performed statistical distribution. When replicating analyses on an Illumina MiSeq benchmark dataset, our method seamlessly adapted to technologies with different biochemistries. RareVar enables sensitive detection of low-frequency SNVs across different sequencing platforms and will facilitate research and clinical applications such as pooled sequencing, cancer early detection, prognostic assessment, metastatic monitoring, and relapses or acquired resistance identification.

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