Dissertations / Theses on the topic 'High-performance transmission'

Acoustically treated, lined ducts are used in a wide range of applications, one of which is a transmission-line loudspeaker (TLL), which consists of a long, acoustically-lined, folded duct attached to the rear of the loudspeaker driver. Consequently, knowledge and understanding of sound propagation within acoustically treated ducts is essential in order to be able to create and analyse designs for the intended applications. The lowfrequency driver of a loudspeaker creates pressure fluctuations on both sides of the diaphragm. Therefore, a loudspeaker cabinet of some sort is required to control the sound radiation from the rear of the driver and to prevent the unwanted interference of those sounds with that radiated from the front of the loudspeaker. The transmission-line loudspeakers are however, designed and optimized to control this rear driver radiations by redirecting the pressure at the back of the driver and use them to extend the overall low-frequency response of the loudspeaker system. Transmission-line loudspeakers rely on the use of sound absorbing materials and, although attempts at modelling the performance of these have been reported in the literature, most transmission-line loudspeakers are designed empirically, using a combination of experience and trial-and-error. This project is concerned with creating and evaluating an engineering method of accurately modelling the sound propagating inside the transmission-line loudspeaker waveguides. Loudspeaker systems inherently suffer from an insufficient low-frequency response, due to their inefficiency at low-frequencies. Therefore, TLL rely on the use of sound absorbing materials added on their internal boundaries to extend their overall response of the loudspeaker at the lowfrequency region. The acoustic load on the driver and the sound radiated from the open end of the TLL duct both depend upon the propagation of sound through the duct; and the physical length of the duct determines the frequencies that can propagate within it. The addition of sound absorbing materials along the interior boundaries of the TLL reduces the speed of propagating sound within it, causing the TLL to respond such as having a much longer internal waveguide, consequently accommodating far lower frequencies within the TLL duct, extending the overall response of the loudspeaker system. The characteristics of sound propagation through a variety of two-dimensional and three-dimensional acoustically lined ducts at low-frequencies have been analyzed. Analytical models of straight ducts have been compared with the developed numerical models. In this research dissipative mufflers, that consist of ducts lined on the inside with an acoustically absorptive material, have been considered. Starting with the propagation of sound within hard-walled boundary condition ducts, this investigation moves to the modelling of waveguides treated with locally-reacting acoustic liners and next into the analysis of ducts treated with bulk-reacting acoustic absorbent materials; two kinds of excitations have been considered, namely pistonic and non-uniform excitation. The impedance mismatch and acoustic dissipation between the sound absorbing layer and the free propagation within the duct has been modelled numerically, and the results have been compared with the in-situ measurements conducted on a range of acoustically treated and purpose built transmission-line loudspeakers. A wide range of sound absorbing materials, namely fibrous and porous absorbers, have been characterized using their low-resistivity and acoustic impedance. Based on their individual characteristics, acoustical optimization was applied on a simple geometry U-shaped TLL duct.

The Linux Kernel protocol stack is getting more and more additions as time goes by. As new technologies arise, more functions are implemented and might result is a certain amount of bloat. However new methods have been added to the kernel to circumvent common throughput issues and to maximize overall performances, given certain circumstances. To assess the ability of the kernel to produce packets at a given rate, we will use the pktgen tool. Pktgen is a loadable kernel module dedicated to trac generation based on UDP. Its philosophy was to be in a low position in the kernel protocol stack to minimize the amount of overhead caused by usual APIs. As measurements are usually done in packets per second instead of bandwidth, the UDP protocol makes perfect sense to minimize the amount of time creating a packet. It has several options which will be investigated, and for further insights its transmission algorithm will be analysed. But a software is not just a compiled piece of code, it is a set of instructions ran on top of hardware. And this hardware may or may not comply with the design of one's software, making the execution slower than expected or in extreme cases even not functional. This thesis aims to investigate the maximum capabilities of Linux packet transmissions in high-speed networks, e.g. 10 Gigabits or 40 Gigabits. To go deeper into the understanding of the kernel behaviour during transmission we will use proling tools, as perf and the newly adopted eBPF framework.
Linux Kernel protokollstacken blir fler och fler tillägg som tiden går. Som ny teknik uppstår, fler funktioner har genomförts och kan leda till en viss mängd svälla. Men nya metoder har lagts till kärnan för att kringgå vanliga genomströmning problem och att maximera den totala föreställningar, med tanke på vissa omständigheter. Att fastställa förmågan hos kärnan för att producera paket med en given hastighet, kommer vi att använda pktgen verktyget. Pktgen är en laddbar kärnmodul tillägnad trafik generation baserad på UDP. Dess filosofi var att vara i en låg position i kärnan protokollstacken för att minimera mängden av overhead orsakad av vanliga API:er. Som mätningarna görs vanligtvis i paket per sekund i stället för bandbredd, gör UDP-protokollet vettigt att minimera mängden tid på att skapa ett paket. Det har flera alternativ som kommer att undersökas, och för ytterligare insikter sin sändningsalgoritmen kommer att analyseras. Men en programvara är inte bara en kompilerad bit kod, är det en uppsättning instruktioner sprang ovanpå hårdvara. Och den här maskinvaran kan eller inte kan följa med utformningen av en programvara, vilket gör utförandet långsammare än väntat eller i extrema fall även fungerar inte. Denna avhandling syftar till att undersöka de maximala kapacitet Linux paketsändningar i höghastighetsnät, t.ex. 10 gigabit eller 40 Gigabit. För att gå djupare in i förståelsen av kärnan beteende under överföringen kommer vi att använda profilverktyg, som perf och det nyligen antagna ramen eBPF.

Output impedance matching for transmission line drivers is not easy to implement due to unavoidable process tolerances. An automatic system for adjusting the output impedance of fast CMOS drivers, on one chip, is described. The output impedance of all identical drivers is adjusted to match the impedance at the input of a reference transmission line, equal in geometry to the lines connected to the other drivers, by a circuit for measuring and correcting the mismatch between the output impedance of one of the drivers, taken as reference and dedicated for this purpose. The voltage measured at the far end of the reference line is sent to a differential amplifier where it is compared with the supply voltage of the final driving stage. According to the comparison result at specific time intervals, a signal is supplied to the regulator which supplies power to the penultimate driving stage, thereby controlling the resistance of the driver to match the line impedance. Simulations have shown that the percentage deviations of the far-end line voltage is approximately 3% for this design compared to a system without feedback which has a far-end line voltage deviation of approximately 18%.

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.

This thesis concerns a study of the performance of an industrial low-speed high-torque hydrostatic drive system. This type of hydrostatic transmission is commonly used in continuous operation in a wide range of heavy-duty drive applications. In many applications the transmissions have to compete with e.g. electromechanical drives, such as DC or AC electric motors combined with gearboxes. In such situations, energy efficiency is a key selection criterion in that even a small increase in the efficiency of high power industrial drives would give substantial savings. Apart from efficiency, lifetime and reliability requirements are important parameters for industrial drive systems, as unplanned stops in industrial working processes can be very costly. The work presented in this thesis is primarily focused on analysing the efficiency behaviour in the transmission, both on the system level and on the component level. Attention has also been paid to lifetime issues, with special emphasis on wear occurring in a sliding contact in a radial piston hydraulic motor. In Paper A the distribution of power losses in a variable axial piston swash plate pump is investigated. The pump under study is commonly used in stationary industrial hydrostatic transmission systems. The churning losses in the pump have been estimated experimentally by measurements in a test rig. The leakage flow and the power losses in the contacts between the piston and the cylinder and between the slipper and the swash plate respectively were simulated with the help of the simulation tool CASPAR. For the pump studied, the churning losses are significant under the operating conditions typically occurring in industrial drive applications. The simulation results indicate that the leakage to the pump casing mainly originates from the gaps between the pistons and their respective cylinders and between the slippers and swash plate. The aim of Paper B is to study two sliding contacts inside a radial piston hydraulic motor and investigate their influence on the torque and power losses. Moreover, it is investigated whether and when a change in the lubrication regime can be expected in these contacts. This is accomplished by a combination of experimental and theoretical studies, with a special focus on two lubricated sliding contacts: the distributor valve contact and the piston/cam roller contact. The theoretical analysis of the contacts indicates, among other things, that the piston/cam roller contact can enter the mixed lubrication regime at low motor speeds. At low running speeds, an increased wear rate has been noted in the contact between the cylinder bore and the piston skirt in a radial piston hydraulic motor. Paper C describes a comparative investigation into different hydraulic fluids' friction properties and wear protection abilities. To simulate the contact between the cylinder bore and the piston skirt in the hydraulic motor, tests were performed in a reciprocating test rig where the contact geometry was of the cylinder-plate type. In the model test a synthetic ester aimed at meeting the conditions in water turbine applications received a top ranking regarding both friction and wear protection properties.
Godkänd; 2003; 20070217 (ysko)

D’importants progès ont été réalisés dans le développement des systèmes biomédicaux implantables grâce aux dernières avancées de la microélectronique et des technologies sans fil. Néanmoins, ces appareils restent difficiles à commercialier. Cette situation est due particulièrement à un manque de stratégies de design capable supporter les fonctionnalités exigées, aux limites de miniaturisation, ainsi qu’au manque d’interface sans fil à haut débit fiable et faible puissance capable de connecter les implants et les périphériques externes. Le nombre de sites de stimulation et/ou d’électrodes d’enregistrement retrouvés dans les dernières interfaces cerveau-ordinateur (IMC) ne cesse de croître afin d’augmenter la précision de contrôle, et d’améliorer notre compréhension des fonctions cérébrales. Ce nombre est appelé à atteindre un millier de site à court terme, ce qui exige des débits de données atteingnant facilement les 500 Mbps. Ceci étant dit, ces travaux visent à élaborer de nouvelles stratégies innovantes de conception de dispositifs biomédicaux implantables afin de repousser les limites mentionnées ci-dessus. On présente de nouvelles techniques faible puissance beaucoup plus performantes pour le transfert d’énergie et de données sans fil à haut débit ainsi que l’analyse et la réalisation de ces dernières grâce à des prototypes microélectroniques CMOS. Dans un premier temps, ces travaux exposent notre nouvelle structure multibobine inductive à résonance présentant une puissance sans fil distribuée uniformément pour alimenter des systèmes miniatures d’étude du cerveaux avec des models animaux en ilberté ainsi que des dispositifs médicaux implantbles sans fil qui se caractérisent par une capacité de positionnement libre. La structure propose un lien de résonance multibobines inductive, dont le résonateur principal est constitué d’une multitude de résonateurs identiques disposés dans une matrice de bobines carrées. Ces dernières sont connectées en parallèle afin de réaliser des surfaces de puissance (2D) ainsi qu’une chambre d’alimentation (3D). La chambre proposée utilise deux matrices de résonateurs de base, mises face à face et connectés en parallèle afin d’obtenir une distribution d’énergie uniforme en 3D. Chaque surface comprend neuf bobines superposées, connectées en parallèle et réailsées sur une carte de circuit imprimé deux couches FR4. La chambre dispose d’un mécanisme naturel de localisation de puissance qui facilite sa mise en oeuvre et son fonctionnement. En procédant ainsi, nous évitons la nécessité d’une détection active de l’emplacement de la charge et le contrôle d’alimentation. Notre approche permet à cette surface d’alimentation unique de fournir une efficacité de transfert de puissance (PTE) de 69% et une puissance délivrée à la charge (PDL) de 120 mW, pour une distance de séparation de 4 cm, tandis que le prototype de chambre complet fournit un PTE uniforme de 59% et un PDL de 100 mW en 3D, partout à l’intérieur de la chambre avec un volume de chambre de 27 × 27 × 16 cm3. Une étape critique avant d’utiliser un dispositif implantable chez les humains consiste à vérifier ses fonctionnalités sur des sujets animaux. Par conséquent, la chambre d’énergie sans fil conçue sera utilisée afin de caractériser les performances d’ une interface sans fil de transmisison de données dans un environnement réaliste in vivo avec positionement libre. Un émetteur-récepteur full-duplex (FDT) entièrement intégré qui se caractérise par sa faible puissance est conçu pour réaliser une interfaces bi-directionnelles (stimulation et enregistrement) avec des débits asymétriques: des taux de tramnsmission plus élevés sont nécessaires pour l’enregistrement électrophysiologique multicanal (signaux de liaison montante) alors que les taux moins élevés sont utilisés pour la stimulation (les signaux de liaison descendante). L’émetteur (TX) et le récepteur (RX) se partagent une seule antenne afin de réduire la taille de l’implant. L’émetteur utilise la radio ultra-large bande par impulsions (IR-UWB) basée sur l’approche edge combining et le RX utilise la bande ISM (Industrielle, Scientifique et Médicale) de fréquence central 2.4 GHz et la modulation on-off-keying (OOK). Une bonne isolation (> 20 dB) est obtenue entre le TX et le RX grâce à 1) la mise en forme les impulsions émises dans le spectre UWB non réglementée (3.1-7 GHz), et 2) le filtrage espace-efficace (évitant l’utilisation d’un circulateur ou d’un diplexeur) du spectre du lien de communication descendant directement au niveau de l’ amplificateur à faible bruit (LNA). L’émetteur UWB 3.1-7 GHz utilise un e modultion OOK ainsi qu’une modulation par déplacement de phase (BPSK) à seulement 10.8 pJ / bits. Le FDT proposé permet d’atteindre 500 Mbps de débit de données en lien montant et 100 Mbps de débit de données de lien descendant. Il est entièrement intégré dans un procédé TSMC CMOS 0.18 um standard et possède une taille totale de 0.8 mm2. La consommation totale d’énergie mesurée est de 10.4 mW (5 mW pour RX et 5.4 mW pour TX au taux de 500 Mbps).
In recent years, there has been major progress on implantable biomedical systems that support most of the functionalities of wireless implantable devices. Nevertheless, these devices remain mostly restricted to be commercialized, in part due to weakness of a straightforward design to support the required functionalities, limitation on miniaturization, and lack of a reliable low-power high data rate interface between implants and external devices. This research provides novel strategies on the design of implantable biomedical devices that addresses these limitations by presenting analysis and techniques for wireless power transfer and efficient data transfer. The first part of this research includes our proposed novel resonance-based multicoil inductive power link structure with uniform power distribution to wirelessly power up smart animal research systems and implanted medical devices with high power efficiency and free positioning capability. The proposed structure consists of a multicoil resonance inductive link, which primary resonator array is made of several identical resonators enclosed in a scalable array of overlapping square coils that are connected in parallel and arranged in power surface (2D) and power chamber (3D) configurations. The proposed chamber uses two arrays of primary resonators, facing each other, and connected in parallel to achieve uniform power distribution in 3D. Each surface includes 9 overlapped coils connected in parallel and implemented into two layers of FR4 printed circuit board. The chamber features a natural power localization mechanism, which simplifies its implementation and eases its operation by avoiding the need for active detection of the load location and power control mechanisms. A single power surface based on the proposed approach can provide a power transfer efficiency (PTE) of 69% and a power delivered to the load (PDL) of 120 mW, for a separation distance of 4 cm, whereas the complete chamber prototype provides a uniform PTE of 59% and a PDL of 100 mW in 3D, everywhere inside the chamber with a chamber size of 27×27×16 cm3. The second part of this research includes our proposed novel, fully-integrated, low-power fullduplex transceiver (FDT) to support bi-directional neural interfacing applications (stimulating and recording) with asymmetric data rates: higher rates are required for recording (uplink signals) than stimulation (downlink signals). The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by space-efficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier (LNA). The UWB 3.1-7 GHz transmitter using OOK and binary phase shift keying (BPSK) modulations at only 10.8 pJ/bit. The proposed FDT provides dual band 500 Mbps TX uplink data rate and 100 Mbps RX downlink data rate. It is fully integrated on standard TSMC 0.18 nm CMOS within a total size of 0.8 mm2. The total power consumption measured 10.4 mW (5 mW for RX and 5.4 mW for TX at the rate of 500 Mbps).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 116-123). Also available in electronic version. Access restricted to campus users.

In wireless systems, providing high data rate services is a major challenge, particularly for mobile terminals (MTs) in multi-floor buildings. The system performance is impaired by path loss, and co-channel interference due to the need to reuse the limited available spectrum. One way to achieve high data rates and better signal quality in this environment is by getting the transmitter and the receiver closer to each other through the use of distributed antenna systems (DASs). DAS reduces the overall transmit power (and hence co-channel interference) and achieves better link reliability by exploiting spatial diversity of multiple antennas. Currently, DASs are designed primarily to provide good coverage in outdoor environments. However, high quality indoor reception and high data rates may not be guaranteed if the system is not deployed within the building. Indoor environments can be very complex, and an insight into the design, and a thorough understanding of the performance of DASs inside the building is required. In this thesis, the performance of an in-building DAS employing frequency reuse is examined, where remote antenna units (RAUs) are deployed on each floor throughout the building and connected to a central unit (CU) where received signals are processea. The impact of co-channel interference on system performance is investigated by using a propagation channel model derived from multi-floor in-building path loss values retrieved from measurement results. System performance is investigated in terms of location-specific spectral efficiency and bit error rate (BER) which are analysed for a range of potential MT locations and various in-building propagation characteristics. The potential benefits of location based antenna selection and deployment options are also investigated. Co-channel interference cancellation where CUs cooperate through joint signal pro- cessing in order to reduce the impact of co-channel interference is considered. Results obtained suggest that the proposed scheme can facilitate better use of the available radio spectrum, and provide high data rates for indoor MTs.

Nous élaborons une interface cerveau-machine (ICM) entièrement sans fil afin de fournir un système de liaison directe entre le cerveau et les périphériques externes, permettant l’enregistrement et la stimulation du cerveau pour une utilisation permanente. Au cours de cette thèse, nous explorons la modélisation de canal, les antennes implantées et portables en tant que propagateurs appropriés pour cette application, la conception du nouveau système d’un émetteur-récepteur UWB implantable, la conception niveau système du circuit et sa mise en oeuvre par un procédé CMOS TSMC 0.18 um. En plus, en collaboration avec Université McGill, nous avons conçu un réseau de seize antennes pour une détection du cancer du sein à l’aide d’hyperfréquences. Notre première contribution calcule la caractérisation de canal de liaison sans fil UWB d’implant à l’air, l’absorption spécifique moyennée (ASAR), et les lignes directrices de la FCC sur la densité spectrale de puissance UWB transmis. La connaissance du comportement du canal est nécessaire pour déterminer la puissance maximale permise à 1) respecter les lignes directrices ANSI pour éviter des dommages aux tissus et 2) respecter les lignes directrices de la FCC sur les transmissions non autorisées. Nous avons recours à un modèle réaliste du canal biologique afin de concevoir les antennes pour l’émetteur implanté et le récepteur externe. Le placement des antennes est examiné avec deux scénarios contrastés ayant des contraintés de puissance. La performance du système au sein des tissus biologiques est examinée par l’intermédiaire des simulations et des expériences. Notre deuxième contribution est dédiée à la conception des antennes simples et à double polarisation pour les systèmes d’enregistrement neural sans fil à bande ultra-large en utilisant un modèle multicouches inhomogène de la tête humaine. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à l’implantation ; nous étudions des matériaux à la fois flexibles et rigides et examinons des compromis de performance. Les antennes proposées sont conçues pour fonctionner dans une plage de fréquence de 2-11 GHz (ayant S11-dessous de -10 dB) couvrant à la fois la bande 2.45 GHz (ISM) et la bande UWB 3.1-10.6 GHz. Des mesures confirment les résultats de simulation et montrent que les antennes flexibles ont peu de dégradation des performances en raison des effets de flexion (en termes de correspondance d’impédance). Finalement, une comparaison est réalisée entre quatre antennes implantables, couvrant la gamme 2-11 GHz : 1) une rigide, à la polarisation simple, 2) une rigide, à double polarisation, 3) une flexible, à simple polarisation et 4) une flexible, à double polarisation. Dans tous les cas une antenne rigide est utilisée à l’extérieur du corps, avec une polarisation appropriée. Plusieurs avantages ont été confirmés pour les antennes à la polarisation double : 1) une taille plus petite, 2) la sensibilité plus faible aux désalignements angulaires, et 3) une plus grande fidélité. Notre troisième contribution fournit la conception niveau système de l’architecture de communication sans fil pour les systèmes implantés qui stimulent simultanément les neurones et enregistrent les réponses de neurones. Cette architecture prend en charge un grand nombre d’électrodes (> 500), fournissant 100 Mb/s pour des signaux de stimulation de liaison descendante, et Gb/s pour les enregistrements de neurones de liaison montante. Nous proposons une architecture d’émetteur-récepteur qui partage une antenne ultra large bande, un émetteur-récepteur simplifié, travaillant en duplex intégral sur les deux bandes, et un nouveau formeur d’impulsions pour la liaison montante du Gb/s soutenant plusieurs formats de modulation. Nous présentons une démonstration expérimentale d’ex vivo de l’architecture en utilisant des composants discrets pour la réalisation les taux Gb/s en liaison montante. Une bonne performance de taux d’erreur de bit sur un canal biologique à 0,5, 1 et 2 Gb/s des débits de données pour la télémétrie de liaison montante (UWB) et 100 Mb/s pour la télémétrie en liaison descendante (bande 2.45 GHz) est atteinte. Notre quatrième contribution présente la conception au niveau du circuit d’un dispositif d’émission en duplex total qui est présentée dans notre troisième contribution. Ce dispositif d’émission en duplex total soutient les applications d’interfaçage neural multimodal et en haute densité (les canaux de stimulant et d’enregistrement) avec des débits de données asymétriques. L’émetteur (TX) et le récepteur (RX) partagent une seule antenne pour réduire la taille de l’implant. Le TX utilise impulse radio ultra-wide band (IR-UWB) basé sur une approche alliant des bords, et le RX utilise un nouveau 2.4 GHz récepteur on-off keying (OOK).Une bonne isolation (> 20 dB) entre le trajet TX et RX est mis en oeuvre 1) par mise en forme des impulsions transmises pour tomber dans le spectre UWB non réglementé (3.1-7 GHz), et 2) par un filtrage espace-efficace du spectre de liaison descendante OOK dans un amplificateur à faible bruit RX. L’émetteur UWB 3.1-7 GHz peut utiliser soit OOK soit la modulation numérique binaire à déplacement de phase (BPSK). Le FDT proposé offre une double bande avec un taux de données de liaison montante de 500 Mbps TX et un taux de données de liaison descendante de 100 Mb/s RX, et il est entièrement en conformité avec les standards TSMC 0.18 um CMOS dans un volume total de 0,8 mm2. Ainsi, la mesure de consommation d’énergie totale en mode full duplex est de 10,4 mW (5 mW à 100 Mb/s pour RX, et de 5,4 mW à 500 Mb/s ou 10,8 PJ / bits pour TX). Notre cinquième contribution est une collaboration avec l’Université McGill dans laquelle nous concevons des antennes simples et à double polarisation pour les systèmes de détection du cancer du sein à l’aide d’hyperfréquences sans fil en utilisant un modèle multi-couche et inhomogène du sein humain. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à des applications portables. Les antennes flexibles miniaturisées monopôles et spirales sur un 50 um Kapton polyimide sont conçus, en utilisant high frequency structure simulator (HFSS), à être en contact avec des tissus biologiques du sein. Les antennes proposées sont conçues pour fonctionner dans une gamme de fréquences de 2 à 4 GHz. Les mesures montrent que les antennes flexibles ont une bonne adaptation d’impédance dans les différentes positions sur le sein. De Plus, deux antennes à bande ultralarge flexibles 4 × 4 (simple et à double polarisation), dans un format similaire à celui d’un soutien-gorge, ont été développés pour un système de détection du cancer du sein basé sur le radar.
We are working on a fully wireless brain-machine-interface to provide a communication link between the brain and external devices, enabling recording and stimulating the brain for permanent usage. In this thesis we explore channel modeling, implanted and wearable antennas as suitable propagators for this application, system level design of an implantable UWB transceiver, and circuit level design and implementing it by TSMC 0.18 um CMOS process. Also, in a collaboration project with McGill University, we designed a flexible sixteen antenna array for microwave breast cancer detection. Our first contribution calculates channel characteristics of implant-to-air UWB wireless link, average specific absorption rate (ASAR), and FCC guidelines on transmitted UWB power spectral density. Knowledge of channel behavior is required to determine the maximum allowable power to 1) respect ANSI guidelines for avoiding tissue damage and 2) respect FCC guidelines on unlicensed transmissions. We utilize a realistic model of the biological channel to inform the design of antennas for the implanted transmitter and the external receiver. Antennas placement is examined under two scenarios having contrasting power constraints. Performance of the system within the biological tissues is examined via simulations and experiments. Our second contribution deals with designing single and dual-polarization antennas for wireless ultra-wideband neural recording systems using an inhomogeneous multi-layer model of the human head. Antennas made from flexible materials are more easily adapted to implantation; we investigate both flexible and rigid materials and examine performance trade-offs. The proposed antennas are designed to operate in a frequency range of 2–11 GHz (having S11 below -10 dB) covering both the 2.45 GHz (ISM) band and the 3.1–10.6 GHz UWB band. Measurements confirm simulation results showing flexible antennas have little performance degradation due to bending effects (in terms of impedance matching). Finally, a comparison is made of four implantable antennas covering the 2-11 GHz range: 1) rigid, single polarization, 2) rigid, dual polarization, 3) flexible, single polarization and 4) flexible, dual polarization. In all cases a rigid antenna is used outside the body, with an appropriate polarization. Several advantages were confirmed for dual polarization antennas: 1) smaller size, 2) lower sensitivity to angular misalignments, and 3) higher fidelity. Our third contribution provides system level design of wireless communication architecture for implanted systems that simultaneously stimulate neurons and record neural responses. This architecture supports large numbers of electrodes (> 500), providing 100 Mb/s for the downlink of stimulation signals, and Gb/s for the uplink neural recordings. We propose a transceiver architecture that shares one ultra-wideband antenna, a streamlined transceiver working at full-duplex on both bands, and a novel pulse shaper for the Gb/s uplink supporting several modulation formats. We present an ex-vivo experimental demonstration of the architecture using discrete components achieving Gb/s uplink rates. Good bit error rate performance over a biological channel at 0.5, 1, and 2 Gbps data rates for uplink telemetry (UWB) and 100 Mbps for downlink telemetry (2.45 GHz band) is achieved. Our fourth contribution presents circuit level design of the novel full-duplex transceiver (FDT) which is presented in our third contribution. This full-duplex transceiver supports high-density and multimodal neural interfacing applications (high-channel count stimulating and recording) with asymmetric data rates. The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by spaceefficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier. The UWB 3.1-7 GHz transmitter can use either OOK or binary phase shift keying (BPSK) modulation schemes. The proposed FDT provides dual band 500-Mbps TX uplink data rate and 100 Mbps RX downlink data rate, and it is fully integrated into standard TSMC 0.18 um CMOS within a total size of 0.8 mm2. The total measured power consumption is 10.4 mW in full duplex mode (5 mW at 100 Mbps for RX, and 5.4 mW at 500 Mbps or 10.8 pJ/bit for TX). Our fifth contribution is a collaboration project with McGill University which we design single and dual-polarization antennas for wireless ultra-wideband breast cancer detection systems using an inhomogeneous multi-layer model of the human breast. Antennas made from flexible materials are more easily adapted to wearable applications. Miniaturized flexible monopole and spiral antennas on a 50 um Kapton polyimide are designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues. The proposed antennas are designed to operate in a frequency range of 2–4 GHz (with reflection coefficient (S11) below -10 dB). Measurements show that the flexible antennas have good impedance matching while in different positions with different curvature around the breast. Furthermore, two flexible conformal 4×4 ultra-wideband antenna arrays (single and dual polarization), in a format similar to that of a bra, were developed for a radar-based breast cancer detection system.

Twisted pan (structured wire) cabling is a principal component in the communications infrastructure, with millions of meters being installed weekly. The rate of increase in upper frequency for this cable appears to be doubling approximately every two years. Clearly, a rigorous approach to the design of these cables is fundamental to achieving data transmission at these frequencies with increasingly stringent performance requirements. This thesis derives a family of equations for the secondary parameters based on an explicit relationship between cable dimensions and materials. These equations have been validated against experimental results and fOWld accurate. Further. equations are developed which calculate the overall S-parameters for cascaded multi.pair cables, the return loss and cross-talk between transmission charmels. In tenns of cable specification. the secondary parameters are the most significant with many of the perfonnance criteria based on these. With designs based largely on the manipulation of physical dimensions, there has been no family of secondary parameter equations given explicitly as functions of cable dimensions and material properties. Similarly, tools have not existed to allow the investigation of design variability or the effects of handling and installation. These are principal requirements in the cable design process. A modelling package, based on Transmission-Line Matrix (TLM) modelling, is developed to a1low the investigation of manufacturing variability and installation handling effects on overall perfonnance of a cable. This modelling technique is validated against both experimental results and analytical results the comparison is excellent. Finally a novel method for the calculation of cross talk between cable pairs is presented. This method is based on a hybrid field·circuit model. Comparisons with measurements show good agreement.

Cette thèse présente nos travaux de recherche qui ont comme principal objectif d'assurer la portabilité des performances et le passage à l'échelle des applications scientifiques complexes exécutées sur des plates-formes multi-coeurs parallèles et hiérarchiques. La portabilité des performances est obtenue lorsque l'ordonnancement des tâches d'une application permet de réduire les périodes d'inactivité des coeurs de la plate-forme. Cette portabilité des performances peut être affectée par différents problèmes tels que des déséquilibres de charge, des communications coûteuses et des surcoûts provenant de l'ordonnancement des tâches. Le déséquilibre de charge est la conséquence de comportements de charges irrégulières et dynamiques, où le volume de calcul varie dynamiquement en fonction de la tâche et de l'étape de simulation. Les communications coûteuses sont provoquées par un ordonnancement qui ne prend pas en compte les différents temps de communication entre tâches sur une plate-forme hiérarchique. Cela est accentué par des communications non uniformes et asymétriques au niveau mémoire et réseau. Enfin, ces surcoûts peuvent être générés par des algorithmes de placement trop complexes dont les coûts ne seraient pas compensés par les gains de performance.Pour atteindre cet objectif de portabilité des performances, notre approche repose sur une récolte d'informations précises sur la topologie de la machine qui vont aider les algorithmes d'ordonnancement de tâches à prendre les bonnes décisions. Dans ce contexte, nous avons proposé une modélisation générique de la topologie des plates-formes parallèles. Le modèle comprend des latences et des bandes passantes mesurées de la mémoire et du réseau qui mettent en évidence des asymétries. Ces informations sont utilisées par nos trois algorithmes d'équilibrage de charge nommés NucoLB, HwTopoLB, et HierarchicalLB. De plus, ces algorithmes utilisent des informations provenant de l'exécution de l'application. NucoLB se concentre sur les aspects non uniformes de plates-formes parallèles, alors que HwTopoLB considère l'ensemble de la hiérarchie pour ses décisions, et HierarchicalLB combine ces algorithmes hiérarchiquement pour réduire son surcoût d'ordonnancement de tâches. Ces algorithmes cherchent à atténuer le déséquilibre de charge et des communications coûteuses tout en limitant les surcoûts de migration des tâches.Les résultats expérimentaux avec les trois régulateurs de charge proposés ont montré des améliorations de performances sur les meilleurs algorithmes de l'état de l'art: NucoLB a présenté jusqu'à 19% d'amélioration de performances sur un noeud de calcul; HwTopoLB a amélioré les performances en moyenne de 19%, et HierarchicalLB a surclassé HwTopoLB de 22% en moyenne sur des plates-formes avec plus de dix noeuds de calcul. Ces résultats ont été obtenus en répartissant la charge entre les ressources disponibles, en réduisant les coûts de communication des applications, et en gardant les surcoûts d'équilibrage de charge faibles. En ce sens, nos algorithmes d'équilibrage de charge permettent la portabilité des performances pour les applications scientifiques tout en étant indépendant de l'application et de l'architecture du système
This thesis presents our research to provide performance portability and scalability to complex scientific applications running over hierarchical multicore parallel platforms. Performance portability is said to be attained when a low core idleness is achieved while mapping a given application to different platforms, and can be affected by performance problems such as load imbalance and costly communications, and overheads coming from the task mapping algorithm. Load imbalance is a result of irregular and dynamic load behaviors, where the amount of work to be processed varies depending on the task and the step of the simulation. Meanwhile, costly communications are caused by a task distribution that does not take into account the different communication times present in a hierarchical platform. This includes nonuniform and asymmetric communication costs at memory and network levels. Lastly, task mapping overheads come from the execution time of the task mapping algorithm trying to mitigate load imbalance and costly communications, and from the migration of tasks.Our approach to achieve the goal of performance portability is based on the hypothesis that precise machine topology information can help task mapping algorithms in their decisions. In this context, we proposed a generic machine topology model of parallel platforms composed of one or more multicore compute nodes. It includes profiled latencies and bandwidths at memory and network levels, and highlights asymmetries and nonuniformity at both levels. This information is employed by our three proposed topology-aware load balancing algorithms, named NucoLB, HwTopoLB, and HierarchicalLB. Besides topology information, these algorithms also employ application information gathered during runtime. NucoLB focuses on the nonuniform aspects of parallel platforms, while HwTopoLB considers the whole hierarchy in its decisions, and HierarchicalLB combines these algorithms hierarchically to reduce its task mapping overhead. These algorithms seek to mitigate load imbalance and costly communications while averting task migration overheads.Experimental results with the proposed load balancers over different platform composed of one or more multicore compute nodes showed performance improvements over state of the art load balancing algorithms: NucoLB presented improvements of up to 19% on one compute node; HwTopoLB experienced performance improvements of 19% on average; and HierarchicalLB outperformed HwTopoLB by 22% on average on parallel platforms with ten or more compute nodes. These results were achieved by equalizing work among the available resources, reducing the communication costs experienced by applications, and by keeping load balancing overheads low. In this sense, our load balancing algorithms provide performance portability to scientific applications while being independent from application and system architecture

The object of this research is to develop robust wire-line systems which demonstrate high performance while simultaneously consuming low power. The main focus of this work is the Clock and Data Recovery (CDR) system, which is the primary circuit of any modern wire-line transceiver. Different techniques starting from circuit-level to system-level have been investigated in this work to improve the performance of multi-gigabit CDRs. A 62 GHz bandwidth amplifier has been presented to address the need for a scalable amplifier for CDR needs. A new technique has been proposed to improve the radiation immunity of latches, to reduce the BER in CDRs occurring due to package radiations. An injection-lock based clock recovery method was investigated as an alternative to PLL based CDRs as they can be used for burst-mode wire-line communication. The investigation yielded the vulnerability of the method to jitter (false-locking and high jitter transfer), the attenuation of which is critical to commercial CDRs. A novel false-lock detector system has been proposed and demonstrated for the first time as a robust solution to the issue of false-locking of CDRs due to repetitive patterns. The implementation of the final CDR system required the use of an L-C tank VCO, the components of which are generic for all commercial CDRs. A new systematic layout technique for the VCO has been proposed and demonstrated in this work to substantially improve the layout area and the associated parasitics, approximately by 70 %. This new layout addresses a critical yet often neglected part of VCO design. Furthermore, a new concept has been proposed to optimize static dividers with respect to their power consumption and number of devices.

A trans-Canadian grid could lead to increased ability to integrate wind energy by increasing capacity, improving reliability, and reducing effects of non-dispatchable generation by integrating renewable energy sources over a wide geographical area. Use of HVDC technology in the trans-Canadian grid would result in lower losses for the long transmission lines required and also would provide other benefits, such as lower right-of-way requirements, high reliability, and fault isolation. However, there are no current installations connecting a tapped connection to an HVDC line; all HVDC lines are operated using two terminals. This thesis proposes two methods of connecting a wind farm to an HVDC line. Techniques using an AC grid based wind farm and a DC grid based wind farm are analyzed based on their efficiency and component requirements, as well as their ability to operate during normal and fault conditions. The advantages and disadvantages of both solutions are compared, and while the best overall efficiency can be obtained using an AC system, high efficiencies can also be obtained for the DC system when combined with wind turbines with a MV output voltage. Preliminary simulation analysis shows that the DC grid design provides superior isolation of the HVDC line from faults on the wind farm grid, but both the AC and DC grids have potential issues implementing fault ride through, depending on the location of the fault.
Un réseau trans-canadien peut aider à intégrer l'énergie éolienne, qui s'étend sur une vaste zone géographique, en augmentant la capacité de transfert de puissance des lignes de transport et en réduisant les effets non-contrôlables des sources d'énergie renouvelable. L'utilisation de la technologie 'HVDC' peut réduire les coûts des longues lignes de transmission et aussi offrir d'autres avantages comme la réduction de l'empreinte géographique, une meilleure fiabilité, et la localisation des défauts. Toutefois, il n'y a pas de raccordements multi-terminaux HVDC en opération. Cette thèse propose deux méthodes de connexion d'un parc éolien à une ligne HVDC, utilisant des réseaux c.a. et c.c. Le rendement, les composantes requises et la performance transitoire des deux méthodes de connexion sont présentés. Une meilleure efficacité peut être obtenue avec le réseau c.a., mais en intégrant les éoliennes MT, l'efficacité du réseau c.c. est améliorée. Des études préliminaires démontrent que le réseau c.c. aide à une meilleure isolation d'un court-circuit dans le parc éolien qui pourrait se transmettre aux lignes HVDC. Les deux réseaux sont capables de réduire les effets d'un court-circuit, mais peuvent avoir des problèmes à demeurer en service sans déclenchement pour un défaut transitoire.

Oxygen barrier coatings have the potential to greatly extend the lifetime of certain food products by incorporating them into existing food packaging. Present technologies face definite challenges of maintaining high performance, while attaining simple and inexpensive preparation methods. The oxygen barrier effect obtained with these coatings is also susceptible to a plasticization effect when exposed to high humidity, since water vapor molecules are readily soluble in typically hydrophilic resins. In this work, we demonstrate a 1 – 2 micron thick oxygen barrier coating, prepared on a 12 micron poly(ethylene terephthalate) substrate, that has oxygen transmission rates as low as 1.44 cc m-2 day-1 under standard conditions and can maintain similar oxygen barrier performance at high humidity. This degree of oxygen barrier meets the standard of 1 – 10 cc m-2 day-1 established for food packaging applications. The coating is prepared through use of sol-gel chemistry between poly(vinyl alcohol) and vinyltrimethoxsilane molecules, which form a strong network resin through hydrolysis and condensation reactions. The formulation of these oxygen barrier coatings allows for variability of solids percentage and viscosity without significant change in performance. The ability to scale up the preparation of these coated films was tested successfully on an industrial flexographic printing press.

Thesis (PhD)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The main aim of this research programme was to compare the relative performance of different insulator materials used in South Africa when subjected to a severe marine pollution environment. A test programme and procedure, test facility and instrumentation were established. Some novel instrumentation and monitoring equipment were developed and built specifically for this research programme, supported by data analysing software programs. In order to compare material performance only, all non-material design variables between the test insulators had to be removed (e.g. creepage distance, connecting length, inter-shed spacing, profile, etc.). To achieve this some of the test insulators had to be specially manufactured. Leakage current, electrical discharge activity, climatic and environmental data was collected successfully over a one-year test period, starting with new test insulators. The peak and energy values of the leakage current were identified as the two main parameters needed to describe the leakage current activity on the test insulators. A correlation was found between the climatic and environmental data and the leakage current data, and it was found that the leakage current can be determined successfully from some of the climatic and environmental parameters monitored by using multiple regression techniques. Surface conductivity and energy were found to be the best parameters to show the maximum and continuous interaction of the insulator material surface with the electrolytic pollution layer. A natural ageing and pollution test procedure was developed, which has become a South African standard and is gaining international acceptance. A model and hypothesis are proposed to describe the electrical discharge activity that takes place on the test insulators and explain the difference in leakage current performance of the various materials. Keywords: Insulator, Pollution, High Voltage, Leakage current, Material performance.
AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie navorsingsprogram was om die relatiewe prestasie van verskillende isolatormateriale wat in Suid-Afrika gebruik word te vergelyk in 'n swaar besoedelde marine omgewing. 'n Toetsprogram en prosedure, toets fasiliteit en instrumentasie is gevestig. 'n Paar nuwe instrumente en moniteer toerusting is ontwikkel en gebou spesifiek vir hierdie navorsingsprogram, gesteun deur data analise sagteware programme. Ten einde slegs materiaalprestasie te vergelyk, moes alle nie-materiaal ontwerpsveranderlikes tussen die toetsisolators verwyder word (bv. kruipafstand, konnekteer lengte, tussen-skerm spasiëring, profiel, ens.). Om dit reg te kry moes sommige van die toetsisolators spesiaal vervaardig word. Lekstroom, elektriese ontladingsaktiwiteit, klimaat en omgewingsdata is suksesvol versameloor 'n een-jaar toetsperiode, beginnende met nuwe toets isolators. Die piek en energie waardes van die lekstroom is identifiseer as die twee hoof parameters wat nodig is om die lekstroomaktiwiteit op die toetsisolators te beskryf. 'n Korrelasie is gevind tussen die klimaat- en omgewingsdata en die lekstroom data, en dit is gevind dat die lekstroom data suksesvol bepaal kan word van sekere van die klimaat- en omgewingsparameters wat gemoniteer is deur veelvoudige regressie tegnieke te gebruik. Oppervlakskonduktiwiteit en energie is gevind die beste parameters te wees om die maksimum en kontinue interaksie van die isolatormateriaaloppervlak met die elektrolitiese besoedelingslaag aan te toon. 'n Natuurlike veroudering en besoedeling toetsprosedure is ontwikkel, wat 'n Suid-Afrikaanse standaard geword het en besig is om internastionale aanvaarding te wen. 'n Model en hipotese word voorgestelom die elektriese ontladingsaktiwiteit wat op die toetsisolators plaasvind te beskryf en om die verskil in lekstroomprestasie van die verskeie materiale te verduidelik. S/eufelwoorde: Isolator, Besoedeling, Hoog Spanning, Leek stroom, Materiaal prestasie.

This master thesis describes the design of a track-and-hold (T&H) circuit with 10bit resolution, 80MS/s and 30MHz bandwidth. It is designed in a 0.18µm CMOS process with a supply voltage of 1.8 Volt. The circuit is supposed to work together with a 10bit pipelined analog to digital converter.

A switched capacitor topology is used for the T&H circuit and the amplifier is a folded cascode OTA with regulated cascode. The switches used are of transmission gate type.

The thesis presents the design decisions, design phase and the theory needed to understand the design decisions and the considerations in the design phase.

The results are based on circuit level SPICE simulations in Cadence with foundry provided BSIM3 transistor models. They show that the circuit has 10bit resolution and 7.6mW power consumption, for the worst-case frequency of 30MHz. The requirements on the dynamic performance are all fulfilled, most of them with large margins.

The study analyses the calibration process of a newly developed high-performance plug-in hybrid electric passenger car powertrain. The complexity of modern powertrains and the more and more restrictive regulations regarding pollutant emissions are the primary challenges for the calibration of a vehicle’s powertrain. In addition, the managers of OEM need to know as earlier as possible if the vehicle under development will meet the target technical features (emission included). This leads to the necessity for advanced calibration methodologies, in order to keep the development of the powertrain robust, time and cost effective. The suggested solution is the virtual calibration, that allows the tuning of control functions of a powertrain before having it built. The aim of this study is to calibrate virtually the hybrid control unit functions in order to optimize the pollutant emissions and the fuel consumption. Starting from the model of the conventional vehicle, the powertrain is then hybridized and integrated with emissions and aftertreatments models. After its validation, the hybrid control unit strategies are optimized using the Model-in-the-Loop testing methodology. The calibration activities will proceed thanks to the implementation of a Hardware-in-the-Loop environment, that will allow to test and calibrate the Engine and Transmission control units effectively, besides in a time and cost saving manner.

Sustaining high performance demand has led to the development of manycore processors. These manycore processors have thermal properties which are different from conventional processors. In order to understand the thermal characteristics of such manycore processors, we have developed a modeling environment with a rich set of features which can be used to used to model different scenarios in manycore processors. Using this modeling framework, we have developed a thermal management policy called 'Weight based management policy'. We have also developed a GUI based modeling tool which can be integrated into the computer architecture curriculum so as to enable students to understand the importance of thermal limitations right during the design phase.

Cette these etudie l'impact sur le plan du trafic de la fourniture des services a nx64 kbps par le rnis suivant trois aspects: caracterisation des teleservices, choix approprie de services support et problemes de teletrafic

En esta tesis, se utilizan t ecnicas matem atico-epidemiol ogicas para modelar el rendimiento acad emico en Espa~na (prestando especial atenci on en el fracaso escolar) para comprender mejor los mecanismos detr as de esta importante cuesti on, as como para predecir c omo evolucionar an los resultados acad emicos en el Bachillerato espa~nol en los pr oximos a~nos. El nivel educativo de Bachillerato en Espa~na est a formado por los dos ultimos cursos antes de acceder a la universidad o al mercado de trabajo y corresponde a los estudiantes de 16 18 a~nos. Este nivel educativo es muy importante para la formaci on de los estudiantes ya que representa un periodo en el que deber an tomar importantes decisiones sobre el futuro acad emico y profesional. En primer lugar, en el Cap tulo 2, se presenta un modelo determinista donde se analiza el rendimiento acad emico asumiendo que la actitud negativa de los alumnos de Bachillerato puede ser debida a su comportamiento aut onomo y la in uencia de compa~neros con malos resultados acad emicos. Luego, en el Cap tulo 3, se mejora el modelo basado en la idea de que no s olo los malos h abitos acad emicos se transmiten socialmente sino tambi en los buenos h abitos de estudio. Adem as, descomponemos los par ametros de transmisi on de h abitos acad emicos con el n de analizar con m as detalle qu e grupos de estudiantes son m as susceptibles a ser in uenciados por compa~neros con buenos o malos h abitos acad emicos. El abandono escolar tambi en han sido incluido en este modelo. El enfoque adoptado permite proporcionar predicciones deterministas y con intervalos de con anza de la evoluci on del rendimiento escolar (incluyendo las tasas de abandono) en Bachillerato en Espa~na en los pr oximos a~nos. Este enfoque, adem as, nos permite modelar el rendimiento acad emico en otros niveles educativos del sistema acad emico espa~nol o de fuera de Espa~na tal y como se muestra en el Cap tulo 4, donde el modelo se aplica satisfactoriamente al sistema acad emico actual de la regi on alemana de Renania del Norte-Westfalia. Para concluir esta tesis, proporcionamos una estimaci on de los costes relacionados con el rendimiento acad emico espa~nol basado en nuestras predicciones. Esta estimaci on representa la inversi on en Bachillerato por parte del Gobierno espa~nol y las familias en los pr oximos a~nos, con especial atenci on en los grupos de estudiantes que no promocionan y abandonan en los diferentes cursos acad emicos.
In this dissertation, we use epidemiologic-mathematical techniques to model the academic performance in Spain (paying special attention on the academic underachievement) to understand better the mechanisms behind this important issue as well as to predict how academic results will evolve in the Spanish Bachillerato over the next few years. The Spanish Bachillerato educational level is made up of the last courses before accessing to the university or to the work market and corresponds to students of 16¿18 years old. This educational level is a milestone in the career training of students because it represents a period to make important decisions about academic and professional future. In a rst step, in the Chapter 2 we will present a deterministic model where academic performance is analyzed assuming the negative attitude of Bachillerato students may be due to their autonomous behavior and the in uence of classmates with bad academic results. Then, in the Chapter 3, the model is improved based on the idea that not only the bad academic habits are socially transmitted but also the good study habits. Besides, we decompose the transmission academic habits into good and bad academic habits, in order to analyze with more detail which group of students are more susceptible to be in uenced by good or bad academic students. The consideration of quantifying the abandon rates is also a new issue dealt with in it. The adopted approach allow to provide both punctual and con dence intervals predictions to the evolution of academic performance (including the abandon rates) in Bachillerato in Spain over the next few years. The adopted approach allows us to model academic performance in academic levels other than Bachillerato and/or beyond the Spanish academic system. This issue is assessed in Chapter 4, where the model is satisfactorily applied to the current academic system of the German region of North Rhine-Westphalia. To conclude this dissertation, we provide an estimation of the cost related to the Spanish academic underachievement based on our predictions. This estimation represents the investment in the Spanish Bachillerato from the Spanish Government and families over the next few years, paying special attention on the groups of students who do not promote and abandon during their corresponding academic year.
Sánchez Sánchez, A. (2013). Modelling the evolution dynamics of the academic performance in high school in Spain. Probabilistic predictions of future trends and their economical consequences [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32280
TESIS

Dans le contexte des Sciences de l'Information et de la Technologie, un des challenges est de créer des systèmes de plus en plus petits embarquant de plus en plus d'intelligence au niveau matériel et logiciel avec des architectures communicantes de plus en plus complexes. Ceci nécessite des méthodologies robustes de conception afin de réduire le cycle de développement et la phase de prototypage. Ainsi, la conception et l'optimisation de la couche physique de communication est primordiale. La complexité de ces systèmes rend difficile leur optimisation notamment à cause de l'explosion du nombre des paramètres inconnus. Les méthodes et outils développés ces dernières années seront à terme inadéquats pour traiter les problèmes qui nous attendent. Par exemple, la propagation des ondes dans une cabine d'avion à partir des capteurs ou même d'une antenne, vers le poste de pilotage est grandement affectée par la présence de la structure métallique des sièges à l'intérieur de la cabine, voir les passagers. Il faut, donc, absolument prendre en compte cette perturbation pour prédire correctement le bilan de puissance entre l'antenne et un possible récepteur. Ces travaux de recherche portent sur les aspects théoriques et de mise en oeuvre pratique afin de proposer des outils informatiques pour le calcul rigoureux de la réflexion des champs électromagnétiques à l'intérieur de très grandes structures . Ce calcul implique la solution numérique de très grands systèmes inaccessibles par des ressources traditionnelles. La solution sera basée sur une grille de calcul et un supercalculateur. La modélisation électromagnétique des structures surdimensionnées par plusieurs méthodes numériques utilisant des nouvelles ressources informatiques, hardware et software, pour dérouler des calculs performants, représente le but de ce travail. La modélisation numérique est basée sur une approche hybride qui combine la méthode Transmission-Line Matrix (TLM) et l'approche modale. La TLM est appliquée aux volumes homogènes, tandis que l'approche modale est utilisée pour décrire les structures planaires complexes. Afin d'accélérer la simulation, une implémentation parallèle de l'algorithme TLM dans le contexte du paradigme de calcul distribué est proposé. Le sous-domaine de la structure qui est discrétisé avec la TLM est divisé en plusieurs parties appelées tâches, chacune étant calculée en parallèle par des processeurs différents. Pour accomplir le travail, les tâches communiquent entre elles au cours de la simulation par une librairie d'échange de messages. Une extension de l'approche modale avec plusieurs modes différents a été développée par l'augmentation de la complexité des structures planaires. Les résultats démontrent les avantages de la grille de calcul combinée avec l'approche hybride pour résoudre des grandes structures électriques, en faisant correspondre la taille du problème avec le nombre de ressources de calcul utilisées. L'étude met en évidence le rôle du schéma de parallélisation, cluster versus grille, par rapport à la taille du problème et à sa répartition. En outre, un modèle de prédiction a été développé pour déterminer les performances du calcul sur la grille, basé sur une approche hybride qui combine une prédiction issue d'un historique d'expériences avec une prédiction dérivée du profil de l'application. Les valeurs prédites sont en bon accord avec les valeurs mesurées. L'analyse des performances de simulation a permis d'extraire des règles pratiques pour l'estimation des ressources nécessaires pour un problème donné. En utilisant tous ces outils, la propagation du champ électromagnétique à l'intérieur d'une structure surdimensionnée complexe, telle qu'une cabine d'avion, a été effectuée sur la grille et également sur le supercalculateur. Les avantages et les inconvénients des deux environnements sont discutés.

Network processors are new types of multithreaded multicore processors geared towards achieving both fast processing speed and flexibility of programming. The architecture of network processors considers many special properties for packet processing, including multiple threads, multiple processor cores on the same chip, special functional units, simplified ISA and simplified pipeline, etc. The architectural peculiarities of network processors raise new challenges for compiler design and optimization. Due to very high clocking speeds, the CPU memory gap on such processors is huge, making registers extremely precious. Moreover, the register file is split into two banks, and for any ALU instruction, the two source operands must come from different banks. We present and compare three different approaches to do register allocation and bank assignment. We also address the problem of sharing registers across threads in order to maximize the utilization of hardware resources. The context switches on the IXP network processor only happen when long latency operations are encountered. As a result, context switches are highly frequent. Therefore, the designer of the IXP network processor decided to make context switches extremely lightweight, i.e. only the program counter(PC) is stored together with the context. Since registers are not saved and restored during context switches, it becomes difficult to share registers across threads. For a conventional processor, each thread can assume that it can use the entire register file, because registers are always part of the context. However, with lightweight context switch, each thread must take a separate piece of the register file, making register usage inefficient. Programs executing on network processors typically have runtime constraints. Scheduling of multiple programs sharing a CPU must be orchestrated by the OS and the hardware using certain sharing policies. Real time applications demand a real time aware OS kernel to meet their specified deadlines. However, due to stringent performance requirements on network processors, neither OS nor hardware mechanisms is typically feasible. In this work, we demonstrate that a compiler approach could achieve some of the OS scheduling and real time scheduling functionalities without introducing a hefty overhead.

This project has investigated the removal of iodine species from wastewater using LDH technology. This research focused on initial laboratory scale experiments to assess the suitability of this methodology as a cost effective means of treating water contaminated with radioiodine from industrial and medical wastes.

Mestrado em Engenharia de Computadores e Telemática
The evolution and growth of the Internet has led to a growing preoccupation regarding dynamic allocation of resources in large networks, as well as to an unprecedented growing adoption of security policies based on tra c classi cation. This phenomenon triggered the creation of deep inspection mechanisms for packets where we can see a cross-access that is based on the retrieval of speci c strings present in packet's Payload. This event raises a number of technical, ethical, and potentially legal limitations. With the increasing need to develop less invasive and more e cient inspection mechanisms, in terms of processing speed and potentially, memory management, the scienti c community began working in other types of approaches to solve the problem. In this dissertation, we propose a tra c ow classi cation system based on Shallow packet inspection. Given the latest forecasts and current statistical data, which estimates that about 90 % of all tra c will be video in the next few years, we have decided to devote special attention to this speci c type. For this, we proceeded to collect non-sensitive information, with which we perform a statistical study based on low-level statistics. The results obtained from this study were analysed from a behavioural point of view, in order to reach the extraction of coherent rules that allow the di erentiation of independent types of tra c. Finally, we studied, conceived and test an e cient ow organisation paradigm. The system has been tested and evaluated using packet ood tests. Following to the measurement and examination of results in terms of processing times as well as the use of main memory.
A evolução e crescimento da Internet tem levado a uma crescente preocupação tendo em vista a alocação dinâmica de recursos em redes de grande dimensão, assim como uma adopção sem precedente de politicas de segurança baseadas em classi ficação de tráfego. Este fenómeno desencadeou a criação de mecanismos de inspecção profunda de pacotes onde se assiste a um acesso transversal, que assenta na obtenção de sequências de bytes especificas, presentes no Payload de cada pacote, o que levanta uma série de limitações técnicas, éticas e potencialmente legais. Com a crescente necessidade de desenvolvimento de mecanismos de inspecção menos invasivos e mais e cientes em termos de velocidade e potencialmente gestão de memória, a comunidade cientifi ca começou a trabalhar em outros tipos de abordagem ao problema. Nesta dissertação, propomos um sistema de classi cação de fluxos de trafego que assenta em Shallow packet inspection. Tendo em conta as ultimas previsões e dados estatísticos atuais, que estimam que cerca de 90% de todo tráfego na Internet, seja do tipo vídeo nos próximos anos, decidimos dedicar especial atenção sobre esse tipo especifico. Para isso, procedemos a recolha de informação não sensível, com a qual efetuamos um estudo estatístico baseado em estatísticas de baixo nivel. Os resultados obtidos nesse estudo, foram analisados de um ponto de vista comportamental, por forma a alcançar uma prova de conceito na extracção de regras coerentes que permitam diferenciar tipos de tráfego independentes. Por fim, estudamos, concebemos e testamos um paradigma de organizaçao de fluxos de forma e ciente. O sistema foi testado e avaliado recorrendo a testes de inundação por pacotes, seguidos da medição e avaliação dos resultados em termos de tempo de processamento, assim como, ao uso de memoria principal.

Numerical models will be developed for the prediction of silencer transmission loss under the operating conditions present in gas turbine exhausts. In these systems the large diameter ducts and high operating temperatures produce a challenging acoustic environment due to the unverified behaviour of fibrous materials at high temperatures and the existence of complex sound fields. To understand the behaviour of fibrous materials at high temperatures their bulk acoustic properties are measured using a modified impedance tube which can heat material samples up to a temperature of 500 C. It will be demonstrated that the high temperature material properties can be extrapolated from room temperature measurements given knowledge of the temperature dependant flow resistivity. Finite element numerical models using point collocation and mode matching techniques to predict the transmission loss of silencers are developed and successfully validated. Dissipative silencer designs with various cross-sectional designs are explored numerically and experimentally according to common industry standards. It is demonstrated that transmission loss may be optimised by the arrangement of the fibrous material across the cross-section. The accurate numerical models allow for effe cient silencers to be designed reducing silencer size and cost. A new hybrid silencer is presented combining dissipative and reactive elements with the aim of increasing the low frequency attenuation of large silencers while maintaining an effective broadband spectrum. Measurements and predictions show this innovative design to be successfull. Application of the hybrid silencer allows for more flexible noise control solutions when design is limited by low frequency noise.

A influência do ultra-som terapêutico na transmissão transcutânea (sonoforese) do diclofenaco sódico como gel tópico (Voltaren Emulgel) foi investigada em 14 voluntários humanos sadios (dez mulheres, quatro homens; 26,4 anos de idade, 62 Kg de peso corporal e 1,7 m de altura, em média). Foi realizada irradiação ultra-sônica prévia da pele (modo contínuo, 1 MHz de freqüência, intensidade de 0,5 W/centímetro quadrado) por 5 minutos em duas áreas de 225 centímetros quadrados (15 x 15 cm) de cada lado da região dorsal dos voluntários usando um gel comum para acoplamento do cabeçote, com subseqüente aplicação do gel de diclofenaco (2,5 g) em cada uma das áreas pré-determinadas e deixado por três horas. Os mesmos voluntários participaram desse procedimento duas vezes com um mês de intervalo, em média, sendo que na segunda vez com o equipamento desligado (procedimento placebo), para controle. Amostras de sangue (3 ml) foram coletadas de veias do antebraço imediatamente antes e com 60, 120 e 180 minutos do procedimento, para análise da massa plasmática do diclofenaco, por meio da cromatografia líquida de alta eficiência (HPLC). Os resultados demonstraram que a massa plasmática do diclofenaco estava significativamente mais elevada (p=0,01) aos 60 e 120 minutos após a irradiação com o ultra-som do que após o procedimento placebo. Dentro das condições em que este estudo foi realizado, os resultados permitem concluir que a irradiação prévia da pele com ultra-som terapêutico facilita a penetração transcutânea de diclofenaco sódico na forma de gel tópico
The influence of therapeutic ultrasound on the transdermal transmission (sonophoresis) of sodium diclofenac as a gel of topic application (Voltaren Emulgel) was investigated in 14 human healthy volunteers (ten women, four men, 26,4 years of age, 62 Kg of body weight and 1,7 m of height on average). Therapeutic ultrasound (continuous mode, 1 MHz frequency, 0,5 W/square centimeter) was applied for 5 minutes on two 225 square centimeters (15 x 15 cm) areas on each side of the dorsum of the volunteers using ultrasound transmission gel as a coupling agent. Following ultrasonic irradiation, the gel was removed and gloves were used to apply 2,5 g on each two defined areas. The same volunteers participated in procedures twice at one-month interval on average, however the second time with the equipment turned off (sham procedure) for control. Blood samples (3 ml) were withdrawn from forearm veins, near the elbow flexure, immediately before and at 60, 120 and 180 minutes from the procedure, for analysis of the plasmatic diclofenac mass by means of high performance liquid chromatography (HPLC). The results showed that the plasmatic diclofenac mass was significantly higher (p=0,01) at 60 and 120 minutes following the ultrasound irradiation than the sham procedure. The results presented in this study support that therapeutic ultrasound applied prior to application of sodium diclofenac gel does lead to enhanced penetration of the drug across the skin under the conditions of the investigation

Un modelo de simulación presenta muchas ventajas en el campo del desarrollo de motores de combustión interna alternativos. Su utilidad es doble. Por un lado, para entender la naturaleza de los fenómenos físicos que suceden en el interior del motor, y por otro, con el fin de optimizar el diseño de los sistemas que integran el mismo. El principal objetivo de esta tesis es desarrollar un modelo de un motor de dos tiempos de 125 cc de altas prestaciones para caracterizar la fluidodinámica interna en los sistemas de admisión, cilindro y escape. Para la construcción del modelo unidimensional del motor es imprescindible conocer información experimental. Por tanto, se han caracterizado de forma experimental los elementos que forman el motor. Por una parte, se ha usado un banco de impulsos para la caracterización dinámica. Por otra parte, se ha empleado un banco de flujo para caracterizar las pérdidas de presión en los elementos. Además, en banco motor, se ha analizado el proceso de combustión, con el objetivo de determinar la ley de liberación de calor. En relación a las tareas de modelado, se ha usado un modelo de diagnóstico para caracterizar del proceso de combustión, experimentando 37 condiciones de operación modificando el régimen de giro, el avance del encendido y usando cinco sistemas de escape. Asimismo, con el fin de poder reproducir el fenómeno de propagación de ondas en el interior del sistema de escape se ha propuesto un modelo de transmisión de calor ya que los modelos convencionales usados en motores de 4T no proporcionan resultados precisos al no contemplar los fenómenos físicos que suceden en el proceso de escape espontáneo de un motor de 2T de estas características. Para ello, se ha caracterizado experimentalmente el fenómeno de propagación de ondas en el interior del sistema de escape midiendo con diversos transductores de presión a lo largo de: un escape de diámetro constante y recto, y varios sistemas de escape derivados del original del motor. El primero se usó para proceder al necesario ajuste de las constantes del modelo mientras que los segundos para realizar la validación del mismo. Para el desarrollo del modelo de transmisión de calor se han contemplado las fluctuaciones de la velocidad instantánea del fluido y la disipación de la turbulencia con una longitud de entrada. Una vez es construido el modelo unidimensional del motor con capacidad de reproducir los complejos fenómenos ondulatorios que existen en el interior de los sistemas de admisión, cilindro y escape, es necesario desarrollar correlaciones para los parámetros que definen la función de Wiebe, usada como ley de liberación de calor en el cilindro. Se ha correlacionado la variación de estos parámetros (en particular, la duración de la combustión y el parámetro de forma) con variables de funcionamiento del motor: régimen de giro y avance del encendido, y variables que se calculan en el modelo: fracción de residuales y densidad de la carga. De esta forma se dispone de un modelo predictivo de las prestaciones del motor si se conoce una correlación para las pérdidas mecánicas, que también ha sido obtenida. El uso del modelo de transmisión de calor propuesto en este trabajo reproduce con precisión la fase y amplitud de la presión de escape con valores inferiores al 1% al comparar el coeficiente de admisión medido y modelado. Las diferencias pueden alcanzar el 7% si se emplean otros modelos encontrados en la literatura. Por otra parte, los resultados obtenidos al usar las correlaciones para la combustión se traducen en: diferencias inferiores al 1.5% entre potencia medida y modelada para todas las condiciones de funcionamiento del motor si el proceso de combustión presenta un coeficiente de variación en la presión del cilindro inferior al 2.5%. Cuando el coeficiente de variación aumenta, debido a la dispersión cíclica, las diferencias entre potencia medida y modelada pueden alcanzar el 4%. Palabras clave: Motores de Combustión Interna Alternativos, Motor de Dos Tiempos, Altas Prestaciones, Instalaciones Experimentales y Medición, Modelado Unidimensional, Modelo de Acción de Ondas, Proceso de Combustión, Transmisión de Calor.
Jiménez Macedo, VD. (2013). Contribución al modelado unidimensional en motores de dos tiempos de altas prestaciones [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/30773
TESIS

ESKOM has relied primarily on impedance-based measurement protection relays for the protection of transmission lines. One of the main disadvantages of distance relays is the limited fault resistance measurement capability. High-resistance faults are characterised by low fault currents, therefore the impedance calculated would be much bigger and so the fault will appear to be beyond the protected line. The main aim of the study is to gain clear understanding of the capability of the existing relays used in Eskom Transmission network, to be able to give recommendations on the refinements to the transmission line protection philosophy required to improve future protection performance. Omicron relay tests, showed that the dynamic characteristics of the three selected relays which were tested covers more fault resistance than that of the normal static impedance and also that the effect of DC offset is negligible with regards to fault resistance measurement capability. Normally the relays have built in algorithms which are able to filter nuisance signals. Theoretical case study that compared the most used relays in Eskom Transmission was done and the results are documented. Settings recommendations to improve fault resistance coverage were deduced from the above study. Fault investigation by using digital simulations (Matlab simulations) has proven the lack of capability to operate for some impedance relays in some fault conditions, as the fault resistance sometimes moves fault impedance beyond relay characteristic even when actual . polarization of the relay is considered. Analysis of the protection performance in transmission proved that high resistance faults accounts for at least half of protection equipment performance index (PEPI) incidents. Finally the author made recommendations to improve the protection performance concerning high resistance faults.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.

碩士
國立虎尾科技大學
電機工程系碩士班
106
This paper uses the manufacturer's WigGig to set seven speed modes to design a system that can automatically adjust the speed according to the distance. It is hoped that through this system, the WigGig speed can be automatically adjusted at different distances to achieve maximum transmission efficiency. We first gave a detailed introduction to the manufacturer's WigGig equipment specifications, including its features, applications, maximum ratings, recommended operating conditions, RF performance, antenna package specifications, and the use of internal APIs provided by the WigGig device. Then the paper introduces its software development environment and its system flow and program logic. For the speed mode 1~7, the actual file data is transmitted, and the file data transmitted to the receiving end is set to be transmitted without any error and correctly opened. And test the packet situation and speed situation, but the farther the distance, the automatic speed reduction interval, the signal can not be received, and the manufacturer's WigGig because of the directivity problem, the signal transmission process does not allow serious shadowing, We carry out the package test for different distances and interference with items. In this paper, we propose a system for designing a set of automatic speed adjustment function for different distances, so that it can be effectively transmitted at different distances. The experimental results show that at different distances, when the two ends cannot transmit at the current speed due to the long distance, they will self-reducing the speed and achieve a truly effective performance. In the data transmitted by the file, we will transfer the files in three different formats, images, compression, and pictures continuously, to know the correctness and stability of the data.

博士
國立交通大學
電子研究所
98
The patterned ground shield (PGS) must be well designed; otherwise they may not at all able to improve the quality factor. Investigations into different strip length, strip spacing and metal layer positions of the slot-type floating shields for wavelength, attenuation loss, and characteristic impedance, which have not yet been conducted before, are performed in this work. In general, the assumption for lumped-equivalent-circuit-model-based techniques is valid only if the lengths of the DUT devices are much smaller than the distances between two ports. However, this is not always true for larger DUT devices and may result in over de-embedding when intrinsic device performance is involved. Therefore, the proposed de-embedding technique can address the problem of over de-embedding. The contribution of the interconnection and the via stack becomes important as the frequencies increase. Unfortunately, currently existing techniques do not account for via stack parasitic contributions. In this dissertation, high-performance transmission lines and improved de-embedding techniques are presented. The slow-wave concept has been used in order to design high-performance transmission lines and reduce the size of the transmission lines. Accurate models that describe the behavior of RF devices are critical for the circuit designs, and improved parasitic de-embedding techniques are proposed as to achieve accurate device characterization. A novel slow-wave transmission line with optimized slot-type floating shields in advanced CMOS technology is presented. Periodical slot-type floating shields are inserted beneath the transmission line to provide the substrate shield and shorten the electromagnetic propagation wavelength. This is the first study that demonstrates how the wavelength, attenuation loss, and characteristic impedance can be adjusted by changing the strip length, the strip spacing, and the metal layer positions of the slot-type floating shields. Wavelength shortening needs to be achieved with a trade-off between the slow-wave effect and the attenuation loss. The slot-type floating shields with different strip lengths, strip spacings and metal layer positions are analyzed. It is concluded that the minimum strip length provides the most optimal result. A design guideline can be established that enables circuit designers to achieve the most appropriate slot-type floating shields for optimal circuit performance. Transmission line test structures were fabricated by using 45 nm CMOS process technology. Both measurement and electro-magnetic (EM) wave simulation were performed up to 50 GHz. Transmission lines are frequently used at a length of half- or quarter-wavelength. With a shortened wavelength, a saving in silicon area of more than 67% can be achieved by using optimized slot-type floating shields. Experimental results demonstrated a higher effective relative permittivity value, improved by a factor of more than 9, and a better quality factor, improved by a factor of more than 6, as compared to conventional transmission lines. A novel transmission line de-embedding technique is presented. With this technique, the left- and right-side ground-signal-ground (GSG) probe pads can be extracted directly using two transmission line test structures of length L and 2L. An additional through structure is designed using via stack de-embedding, which is unique amongst current de-embedding methods. The advantages of the proposed method include the following: (1) a smaller silicon area; (2) the consideration for discontinuity between the pad and interconnect; (3) the consideration for substrate coupling and contact effects; (4) the employment of via stack de-embedding; and (5) the solution to the over de-embedding. The proposed novel methodology could be considered as a breakthrough in the area of ultra-high frequency de-embedding and should enable more accurate RF models to be developed. In the proposed methodology, intrinsic slow-wave coplanar waveguide (CPW) transmission line structures are placed on the inter-level metallization layers, as they are the most appropriate RF device for a cascade-based de-embedding method involving the via stack de-embedding technique. Experimental results have demonstrated that attenuation loss and wavelength can be optimized by changing the metal density and the metal layer positions of the floating shields. With a shortened wavelength, a reduction in silicon area of more than 66% can be achieved by using optimized slot-type floating shields located both above and below the CPW structure.

碩士
中華大學
電機工程學系碩士班
90
In this thesis statistical method is used to analyze the transmission quality of high-speed serial bus with consideration both of jitter and skew. The one-way (unidirectional) transmission circuit models for physical layer of IEEE 1394 data-strobe encoding scheme and the traditional data/clock scheme are constructed. It is shown that the transmission quality (Bit Error Rate) of the former is superior to the latter for tolerance of higher jitter. Consecutively, two-way (bi-directional) circuit model for IEEE 1394 is constructed and analyzed. Both of jitter and skew will degrade the performance of high-speed serial transmission.

This thesis describes the research done to achieve wideband frequency modulator and demodulator circuits for transmission of analog multi-channel cable television (CATV). These circuits were fabricated in an advanced silicon bipolar technology and resulted in the best-reported fully electronic implementation of a modulator for wideband frequency modulation (WFM) of CATV signals. Design of the modulator is achieved by using an emitter-coupled multivibrator (ECM) based oscillator. The viability of this approach is based on the ECM wideband tuning linearity at high-speed operation, particular noise requirements of CATV transmission, and a novel phase noise reduction technique. Results for an ECM-based current-controlled oscillator (ICO) show linear operation in the range of 1GHz to 2.5GHz. Results for a linearized ECM-based voltage-controlled oscillator (VCO) show linear operation in the range of 1.5GHz to 2GHz. Linearity, from static tuning measurements, show maximum deviations from an ideal linear fit of 15MHz, and 1.5MHz for the ICO and VCO respectively. Results for a wideband delay-line demodulator show linear operation in a range of 2.5GHz, with back-to-back modulator/demodulator modulation bandwidth of 1GHz. A state-of-the art phase noise measurement system, based on automatic data gathering with a spectrum analyzer followed by mathematical post-processing, is presented. This system measures the phase noise of a variable oscillator versus tuning input, at a fixed offset from the carrier, with better accuracy than the best dedicated commercial measurement instrument available at the time. The first study of phase noise in high-speed ECMs is presented from experimental measurements and circuit noise simulations. This study revealed new findings on the fundamental noise limits of ECMs. It was found that, at high frequencies, shot noise of the ECM core transistors dominates oscillator phase noise. Furthermore, phase noise was found to be directly proportional to the ECM tail current and inversely proportional to the square of ECM timing capacitor. This lead to a simple and novel optimization design approach to reduce phase noise by scaling up, by the same factor, the tail current and timing capacitor with minimal effects on tuning linearity. In addition, the modulator perspectives in a narrowcast WFM system are explored through system calculations.

碩士
國立臺灣科技大學
電子工程系
97
With the rapid growth of multimedia processing technologies, image and video compression are widely used on the network access. In recent years, there has been increased interest in the field of low power image compression and data transmission. Few studies, however, about low power data transmission for compressed image and video were presented. The compressed files are frequently transmitted on the network even though an image is usually compressed only once. For this reason, we can not neglect the power dissipation during transmitting data on the network. In order to overcome these difficulties, we improve the Huffman encoder of the JPEG flow to make the compressed data low power on transmission. Huffman encoder affects the behavior of transmission data directly since it is adopted as the last step of well-known image and video standards. On the other hand, Non Return to Zero, Inverted (NRZI) encoder is the first step in many telecommunication systems. In this thesis, thus, a low power data transmission scheme for NRZI based on Huffman encoding is presented. We propose a new Huffman table for the image and video compression to match NRZI encoder for reducing bit stuffing to achieve low power on data transmission. Simulation results test several images used by image processing research community. Our practical results indicate that the reduction rate in NRZI bit stuffing is from 22.05% to 83.95% compared with the standard JPEG compression. Therefore, it is observation that the file size after the proposed encoding process is less than that of the standard one. In other words, the compressed results can reduce power consumption during data transmission. The method provides a way to minimize the transmitted power under the same compression ratio.

博士
國立成功大學
電機工程學系碩博士班
96
The Transmission Control Protocol (TCP) provides a reliable host-to-host data transfer function in many network applications and plays a crucial role in controlling congestion throughout the Internet. The performance-related issues arising in TCP-based applications stem primarily from the various interactions between the internal TCP flow control and congestion control schemes and the surrounding communication environment. However, while many attempts have been made to improve the performance of TCP, the algorithms and parameters which are suitable for one environment are generally not transferable to others, and therefore TCP must be specifically adapted to different environments. Accordingly, this thesis discusses the fundamental problems and performance limitations of the TCP transport-layer protocol in various existing and emerging network systems and proposes a number of schemes for enhancing the TCP performance. The proposed schemes are quantified in terms of their achieved effective throughputs and are benchmarked against various existing TCP schemes. The numerical results confirm that the proposed schemes greatly enhance the performance of TCP over a variety of heterogeneous network environments.

Sneak path current is a significant remaining obstacle to the utilization of large crossbar arrays for non-volatile memories and other applications of memristors. A two-terminal selector device with an extremely large current-voltage nonlinearity and low leakage current could solve this problem. We present here a Ag/oxide-based threshold switching (TS) device with attractive features such as high current-voltage nonlinearity (~1010), steep turn-on slope (less than 1 mV/dec), low OFF-state leakage current (~10-14 A), fast turn ON/OFF speeds (<75/250 ns), and good endurance (>108 cycles). The feasibility of using this selector with a typical memristor has been demonstrated by physically integrating them into a multilayered 1S1R cell. Structural analysis of the nanoscale crosspoint device suggests that elongation of a Ag nanoparticle under voltage bias followed by spontaneous reformation of a more spherical shape after power off is responsible for the observed threshold switching of the device. Such mechanism has been quantitatively verified by the Ag nanoparticle dynamics simulation based on thermal diffusion assisted by bipolar electrode effect and interfacial energy minimization.

碩士
逢甲大學
通訊工程所
99
Cloud computation and always-connected Internet have attracted the most industrial attention for the past few years. Meanwhile, with the development of IC technologies advancing toward higher operating frequencies and the trend of miniaturization on wireless communication products, the circuits and components are placed much closer than ever before. The system with highly integrated high-speed digital circuits and multi-radio modules are now facing the challenge from performance degradation by even more complicated platform EMI noisy environment. The EM noises emitted by unintentionally radiated interference sources may severely affect the receiving performance of antenna, and thus result in the severe performance degradation of wireless communication. Therefore, we have investigated and analyzed the EMI noise characteristics of commonly embedded digital devices for further high performance wireless communication design. Since the CAMERA or CMOS camera module is most adopted to the popular mobile devices such as cellular phone or Netbook, we hence focus on EMI analysis of the built-in camera module by application of IEC 61967-3 method. The concept of noise budget for devices on wireless communication product stems from the link-budget for RF Tx/Rx performance. It also borrows the idea from EMC testing requirements for automobile industry to identify the potential interference sources that might cause safety problem. In this study, we utilized the surface scan method with near-field electromagnetic measuring system equipped with visual interface to highlight and further analyze the field strength of emitted noise by color-enhanced pattern. From the spatial distribution of interference noise measured at specific interfered communications frequency range, we can identify the locations and radiation patterns of interference sources (digital ICs or traces). We finally used Langer near-field probe for surface scan measurement system to investigate the EMI noise from the Camera module in notebook computer, and therefore further to analyze the relationship between the wireless communications performance and Camera commands with throughput measurement, and related distance to antenna respectively. To improve the wireless communication TIS performance on notebook computer, we first investigated the EMI noise from the built-in camera module and analyzed the impact of various camera modes on performance with throughput measurement. We then utilized the near-field EM surface scanner to detect the EMI sources on notebook and locate the major noise sources around antenna area with 2-D hot-spot distribution plot. Finally, we designed and implemented periodic structures for isolation on the notebook computer to effectively suppress noise source-antenna coupling and improve the receiving sensitivity of wireless communication system. Keywords:RFI、Netbook、platform noise、Noise Budget

碩士
國立臺灣科技大學
電子工程系
107
This work successfully designs and manufactures a 400-Gb/s optical transceiver module for high-speed optical interconnect in the cloud data centers. The 400-Gb/s module is constructed with 16-channel transceivers that are allocated with 4 wavelengths and 4 single-mode fibers. It includes EML driver ICs, receiver ICs, high-speed EML sources, and photodetectors. 　　Increasing the channel bandwidth and data rates is the main focus of research and development to meet the demand of high-speed optical transmission and interconnect. For data center applications, soon after the 100Gb/s optical transceivers were commercialized, 400Gb/s transceivers became the hottest topic for most fiber-optic vendors. This thesis successfully designed and enhanced the 16"×" 25 Gb/s optical transceiver module for 25 Gb/s NRZ signals. The high-speed circuit board uses a substrate with low dielectric loss. The differential transmission line is realized to reduce common mode noise. The high-frequency circuit simulation software is used to design and optimize the transmission lines and circuits. The simulated S-parameter and eye diagram are verified with the measurement results. The EML driver IC is used to generate the 25Gb/s NRZ signal, and the whole transceiver module is measured to transmit the signal along a single mode fiber for up to 10 km. Each channel can achieve <10-12 bit error rate with an optical power >-13 dBm.