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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
361

Design of Inductive Power Transmission System for Low Power Application with Movable Receiver and Large Air Gap

Kallel, Bilel 09 April 2019 (has links)
Inductive power transmission is very useful, not only for systems where energy transfer should take place in hazardous, humid and wet areas, but also for mobile and very small systems. It finds today a widespread use in several fields, such as industry, automotive, medicine and smart buildings. For a good efficiency and a high-power transmission, the sending and the receiving coils should be perfectly aligned and close to each other. A misalignment between the sender and the receiver becomes unavoidable especially for systems with movable parts. This thesis aims to improve the transmitted power, the mutual inductance, the power at the load, and consequently the power transmission efficiency in case of lateral misalignment between the sending and receiving coils and at large coil-to-coil distance. For this purpose, we adopt a multi input single output (MISO) coil system able to orientate the issued magnetic field to the receiving coil by powering the neighbouring sending coils of the active ones with a weak current in the opposite direction. Furthermore, an analytical model of the used coils and an accurate three-dimensional model of the system have been developed to calculate the induced voltage, the induced current, and the equivalent mutual inductance. Both simulation and experimental results prove that the proposed multi-coil inductive system having an hexagonal arrangement and the sending coils, which have the half diameter of the receiving coil, is able to improve significantly the transmitted power in case of lateral misalignment and big air gap. The novel MISO system reaches better efficiency beginning with an air gap of 50% of the sending coil diameter, and a misalignment of 28% of the sending coil diameter. It reaches the double of the transmitted power of the conventional two-coil inductive system at 50 mm air gap (corresponding to 166% of the sending coil diameter) and at 10 mm lateral misalignment (corresponding to 33% of the sending coil diameter). In order to improve the equivalent mutual inductance between the primary and secondary sides and to avoid energy losses, we propose a receiver detection method using the sending coils themselves as detectors. Thereby, only the sending coils, under the receiver, are activated and the others remain switched off. For that, the peak of the AC current of the sending coils, is measured and then compared to a detection threshold. The excitation strategy of the active sending coils is optimized corresponding to the receiving coil position. The novel excitation strategy increases the mutual inductance by 85% and the induced voltage by 13% at perfect alignment and by 30% and 10% respectively at 10 mm lateral misalignment, in comparison to the MISO system without a receiver detector and coil-excitation strategy. In order to increase the transmitted power by resonance, different system topologies have been investigated, such as series-series SS, series-parallel SP, parallel-series PS, and parallel-parallel PP topologies for different levels of load impedance. The results show that a multi-coil inductive system with parallel-parallel PP topology realizes a higher transmitted power than the other topologies for both high and low load impedance values. The proposed multi-coil inductive system is suitable for low-power systems, such as wireless sensors and biomedical implants, but can be also applied to higher range of power at a flexible position of the receiver. / Die induktive Energieübertragung ist interessant, nicht nur für Systeme, bei denen die Energieübertragung in rauen, feuchten und nassen Bereichen erfolgen soll, sondern auch für mobile und sehr kleine Systeme. Diese Art von Energieübertragung findet heute eine breite Anwendung in verschiedenen Bereichen, wie z.B. Industrie, Automobil, Medizin und intelligente Gebäude. Um eine gute Effizienz und eine hohe Energieübertragungsleistung zu realisieren, sollten die Sende- und Empfangsspulen perfekt ausgerichtet und nahe beieinander sein. Insbesondere bei Systemen mit beweglichen Teilen ist jedoch eine Fehlausrichtung zwischen Sender und Empfänger unvermeidlich. Diese Arbeit zielt darauf ab, die übertragene Leistung, die gegenseitige Induktivität, die Leistung an der Last und damit den Wirkungsgrad der Leistungsübertragung im Falle einer seitlichen Fehlausrichtung zwischen Sende- und Empfangsspule und bei großem Abstand von Spule zu Spule zu verbessern. Zu diesem Zweck wird ein Multi-Input Single-Output (MISO)-Spulensystem vorgeschlagen, das in der Lage ist, das ausgegebene Magnetfeld auf die Empfangsspule auszurichten, indem die benachbarten Spulen der aktiven Sendespulen mit einem schwachen Strom in der entgegengesetzten Richtung versorgt wird. Darüber hinaus wurde ein analytisches Modell für die verwendeten Spulen und ein genaues dreidimensionales Modell für das System entwickelt, um die induzierte Spannung, den induzierten Strom und die äquivalente gegenseitige Induktivität zu berechnen. Sowohl die Simulation als auch die experimentellen Ergebnisse belegen, dass das vorgeschlagene induktive Mehrfachspulensystem mit hexagonaler Anordnung und die Sendespulen, die den halben Durchmesser der Empfangsspule haben, in der Lage sind, die Sendeleistung bei lateraler Fehlausrichtung und großem Luftspalt deutlich zu verbessern. Das neuartige MISO-System erreicht einen besseren Wirkungsgrad, beginnend mit einem Luftspalt von 50% des Sendespulendurchmessers und einer Fehlausrichtung von 28% des Sendespulendurchmessers. Sie erreicht bei 50 mm Luftspalt (entspricht 166% des Sendespulendurchmessers) und bei 10 mm seitlichem Versatz (entspricht 33% des Sendespulendurchmessers) das Doppelte der Sendeleistung des herkömmlichen Zwei-Spulen-Induktivsystems. Um die äquivalente gegenseitige Induktivität zwischen Primär- und Sekundärseite zu verbessern und Energieverluste zu vermeiden, schlagen wir ein Verfahren zur Detektion des Empfängers vor, bei dem die Sendespulen selbst als Detektoren verwendet werden. Dabei werden nur die Sendespulen unter dem Empfänger aktiviert und die anderen bleiben ausgeschaltet. Dazu wird der Scheitelwert des Wechselstroms der Sendespulen gemessen und mit einem vorgegebenem Schwellenwert verglichen. Die Anregungsstrategie der aktiven Spulen wird entsprechend der Position der Empfangsspule optimiert. Die neuartige Anregungsstrategie erhöht die gegenseitige Induktivität um 85% und die induzierte Spannung um 13% bei perfekter Ausrichtung und um 30% bzw. 10% bei 10 mm seitlichem Versatz, im Vergleich zum MISO-System ohne Empfängerdetektor und Spulenanregungsstrategie. Um die übertragene Leistung durch Resonanz zu erhöhen, wurden verschiedene Systemtopologien untersucht, wie z.B. Serien-SS, Serien-Parallel-SP, Parallel-Series-PS und Parallel-Parallel-PP-Topologien für verschiedene Stufen der Lastimpedanz. Die Ergebnisse zeigen, dass ein MISO System mit parallel-paralleler PP-Topologie eine höhere Sendeleistung realisiert als die anderen Topologien für hohe und niedrige Last-Impedanzen. Das vorgeschlagene induktive Mehrspulensystem eignet sich für Systeme mit geringer Leistung, wie drahtlose Sensoren und biomedizinische Implantate, kann aber auch flexibler Position des Empfängers in einen höheren Leistungsbereich angewendet werden.
362

CHAIN-LENGTH PROPERTIES OF CONJUGATED SYSTEMS: STRUCTURE, CONFORMATION, AND REDOX CHEMISTRY

Saadia T Chaudhry (8407140) 22 April 2021 (has links)
The development of solution-processable semiconducting polymers has brought mankind’s long-sought dream of plastic electronics to fruition. Their potential in the manufacturing of lightweight, flexible yet robust, and biocompatible electronics has spurred their use in organic transistors, photovoltaics, electrochromic devices, batteries, and sensors for wearable electronics. Yet, despite the successful engineering of semiconducting polymers, we do not fully understand their molecular behavior and how it influences their doping (oxidation/reduction) properties. This is especially true for donor-acceptor (D-A) p-systems which have proven to be very efficient at tuning the electronic properties of organic semiconductors. Historically, chain-length dependent studies have been essential in uncovering the relationship between the molecular structure and polymer properties. Discussed here is the systematic investigation of a complete D-A molecular series composed of monodispersed and well-defined conjugated molecules ranging from oligomer (n=3-21) to polymer scale lengths. Structure-property relationships are established between the molecular structure, chain conformation, and redox-active opto-electronic properties for the molecular series in solution. This research reveals a rod-to-coil transition at the 15 unit chain length, or 4500 Da, in solution. The redox-active optical and electronic properties are investigated as a function of increasing chain-length, giving insight into the nature of charge carriers in a D-A conjugated system. This research aids in understanding the solution behavior of conjugated organic materials. <br>
363

Compact Multi-Coil Inductive Power Transfer System with a Dynamic Receiver Position Estimation

Bouattour, Ghada 07 April 2022 (has links)
Inductive power transfer (IPT) systems with tolerance to the lateral misalignment are advantageous for enhancing the transmitted power, usability and security of the system. In this thesis, a misalignment tolerant multi-coil design is proposed to supply stationary and dynamic battery-free wireless devices. A compact architecture composed of individually switchable 3 layers of printed coils arranged with overlap for excellent surface coverage. A hybrid architecture based on three compact AC supply modules reduces the supply circuit complexity on the sending Seite 2 von 4side. It detects the position of the receiver coil quickly, controls the activation of the transmitting coils and estimates the next receiver position. The proposed architecture reduces the circuit footprint by a factor of 62% compared to common architectures. A transmitter coil activation strategy is proposed based on the detection of the transmitting coils voltage and communication between sending side and receiving side to detect devices to supply nature and position and to differentiate them from other conductive objects in the sending area to the supplying security. The experimental results prove that the proposed architecture has a good performance for different trajectories when the device speed does not exceed 15 mm/s. Besides, the maximum detection time for the initial device position is about 1.6 s. The maximal time interval to check the transmitter coils is around 0.7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK / Induktive Energieübertragungssysteme (IPT) mit Toleranz gegenüber seitlichem Versatz sind vorteilhaft, um die übertragene Leistung, die Nutzbarkeit und die Sicherheit des Systems zu verbessern. In dieser Arbeit wird ein versatztolerantes Multispulen-Design vorgeschlagen, um stationäre und dynamische batterielose drahtlose Geräte zu versorgen. Die kompakte Architektur besteht aus 3 einzeln schaltbaren Schichten gedruckter Spulen, die überlappend angeordnet sind, um eine hervorragende Oberflächenabdeckung zu gewährleisten. Eine hybride Architektur, die auf drei kompakten AC-Versorgungsmodulen basiert, reduziert die Komplexität der Versorgungsschaltung auf der Senderseite. Sie erkennt die Position der Empfängerspule schnell, steuert die Aktivierung der Sendespulen und schätzt die nächste Empfängerposition. Die vorgeschlagene Architektur reduziert den Platzbedarf der Schaltung um einen Faktor von 62 % im Vergleich zu herkömmlichen Architekturen. Es wird eine Aktivierungsstrategie für die Sendespulen vorgeschlagen, die auf der Erkennung der Spannung der Sendespulen und der Kommunikation zwischen Sende- und Empfangsseite basiert, um die Art und Position der zu versorgenden Geräte zu erkennen und sie von anderen leitfähigen Objekten im Sendebereich zu unterscheiden. Die experimentellen Ergebnisse zeigen, dass die vorgeschlagene Architektur eine gute Leistung für verschiedene Trajektorien hat, wenn die Geschwindigkeit der Geräte 15 mm/s nicht überschreitet. Außerdem beträgt die maximale Erkennungszeit für die anfängliche Geräteposition etwa 1,6 s. Das maximale Zeitintervall für die Überprüfung der Senderspulen beträgt etwa 0,7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK
364

Explorations into protein structure with the knob-socket model

Fraga, Keith Jeffrey 01 January 2016 (has links)
Protein sequences contain the information in order for a protein to fold to a unique compact, three-dimensional native structure. The forces that drive protein structures to form compact folds are largely dominated by burial of hydrophobic amino acids, which results in non-specific packing of amino acid side-chains. The knob-socket model attempts to organize side-chain packing into tetrahedral packing motifs. This tetrahedral motif is characterized with a three residues on the same secondary structure forming the base of the tetrahedron packing with a side-chain from a separate secondary structure. The base of the motif is termed the socket, and the other side-chain is called the knob. Here, we focus on extending the knob-socket model to understand tertiary and quaternary structure. First, single knobs sometimes pack into more than one socket in real structures. We focus on understanding the topology and amino acid preferences of these tertiary packing surfaces. The main results from the study of tertiary packing surfaces is that they have a preferred handedness, some interactions are ancillary to the packing interaction, there are specific amino preferences for specific positions in packing surfaces, and there is no relationship between side-chain rotamer of the knob packing into the tertiary packing surface. Next, we examine the application of the knob-socket to irregular and mixed packing in protein structure. The main conclusions from these efforts show canonical packing modes between secondary structures and highlight the important of coil secondary structure in providing many of the knobs for packing. Third, we investigate protein quaternary structure with a clique analysis of side-chain interactions. We identify a possible pseudo knob-socket interaction, and compare knob-socket interactions between tertiary and quaternary structure. Lastly, we discuss the workflow used in CASP12 to predict side-chain contacts and atomic coordinates of proteins.
365

PCBA verification and fault detection using a low-frequency GMR-based near-field probe with magnetic closed-loop feedback compensation : A non-contact alternative to physical probing / Verifiering och feldetektering av kretskort mha en lågfrekvent närfältssond baserad på en GMR-sensor med magnetisk återkopplingskrets med sluten kompensationsslinga : Ett kontaktlöst alternativ till fysisk sondering

Sundh, Joacim January 2022 (has links)
As electronics are getting both smaller and more advanced, the need to verify and validate remains and the means are getting more complex the more functions and components are added. Traditionally, in-circuit tests (ICTs) are performed by probing dedicated test points on the Printed Circuit Board Assembly (PCBA) in a test sequence that is unique to each product. But as the density of components increases, the choice between component and test point must be considered. Instead of decreasing the reliability during verification by having to remove less system-critical test points, this thesis suggests the use of a near-field probe (NFP) based around a Giant Magneto-Resistance (GMR) sensor to possibly replace the need for a physical test point by instead performing contactless testing. The use of a GMR sensor allows for bandwidth from 0 Hz up to the MHz range, whereas commercial NFPs are based on a different technique and are operational from the MHz range and up. The goal of this project was to improve the non-linearity of typically 15% present in the AAH002-02 model from NVE by the use of an analogue closed-loop magnetic feedback circuit. The project successfully improved the linearity to 99.8% by the use of an instrumentation amplifier, a subtractor and a push-pull amplifier in conjunction with a 3x30 turn planar coil embedded in a PCB, located beneath the sensor Integrated Circuit (IC). The resulting linearity was verified by a Helmholtz coil where a uniform magnetic field was produced with linearly increased field strength, and calculated using the R2 value from a linear regression analysis on the acquired data. In the future, the data acquired from this kind of NFP could be used together with a Machine Learning (ML) model to remove the manual labour required when constructing these product-unique test sequences. / Dagens elektronik blir både mindre och mer avancerad, men behovet av verifiering och validering av dessa kvarstår och metoderna för detta ökar i komplexitet ju fler funktioner och komponenter som läggs till. Dagens kretskortstester genomförs genom att sondera dedikerade testpunkter strategiskt utplacerade på kretskortet enligt en testsekvens som är unikt skapad för varje produkt. Men med att densiteten av komponenter ökar måste valet mellan komponent och testpunkt tas i beaktning. Instället för att minska tillförlitligheten vid validering genom att ta bort mindre kritiska testpunkter föreslår denna avhandling användandet av en närfältssond baserad runt en Giant Magneto-Resistance (GMR)-sensor för att möjligen ersätta behovet av en fysisk testpunkt genom att istället genomföra kontaktlös testning. Användandet av en GMR-sensor tillåter en bandbredd från 0 Hz upp till MHzområdet, där kommersiella närfältssonder är baserade på annan teknik och är funktionsdugliga från MHz-området och uppåt. Målet med detta projekt var att förbättra olinjäriteten på typiskt 15% som är närvarande hos en sensor av modell AAH002-02 från NVE genom en analog magnetisk återkopplingskrets med sluten slinga. Projektet lyckades förbättra linjäriteten till 99.8% genom användandet av en intrumentförstärkare, en subtraherare och en push-pull-förstärkare i samverkan med en plan spole på 3x30 varv inbyggd i ett mönsterkort placerd under sensorns integrerade krets. Den resulterande linjäriteten validerades med hjälp av en Helmholtz-spole där ett uniformt magnetfält producerades med linjärt ökande fältstyrka och beräknades genom R2 -värdet från en linjär regression-analys på den inhämtade datan. I framtiden kan datan som inhämtats från den här sortens närfältssond kunna användas tillsammans med en maskininlärningsmodell för att ersätta det manuella arbetet som idag krävs för att konstruera dessa produktunika testsekvenser
366

Μέθοδοι και διατάξεις απευθείας ηλεκτροακουστικής μετατροπής για ψηφιακό ήχο / Methods and implementations for direct electroacoustic transduction of digital audio

Κοντομίχος, Φώτιος 06 October 2011 (has links)
Η παρούσα διδακτορική διατριβή εστιάστηκε στη μελέτη συστημάτων ακουστικής εκπομπής για απευθείας αναπαραγωγή ψηφιακού ήχου. Η ερευνητική διαδικασία βασίστηκε στον προσδιορισμό και βελτίωση των δυνατοτήτων δύο διαφορετικών υλοποιήσεων ακουστικής μετατροπής: i. Ένα υβριδικό πρωτότυπο θερμοακουστικό στοιχείο και ii. Μια συστοιχία 32 ηλεκτροδυναμικών μεγαφώνων σχεδιασμένη, ώστε να αναπαράγει ψηφιακά ηχητικά σήματα. Η θερμοακουστική μετατροπή προσφέρει μια εναλλακτική τεχνική για υλοποιήσεις ακουστικών στοιχείων. Είναι βασισμένη στο μετασχηματισμό των διακυμάνσεων της θερμικής ενέργειας σε ακουστικό κύμα που προκαλούνται από τη ροή του ηλεκτρικού σήματος ήχου σε μια συσκευή στερεάς κατάστασης που λειτουργεί χωρίς τη χρήση οποιουδήποτε κινούμενου τμήματος ή μηχανισμού. Η υλοποίηση αυτής της τεχνικής ηχητικής αναπαραγωγής, μελετάται με τη χρήση ενός πρωτότυπου μετατροπέα ο οποίος αναπτύχθηκε πάνω σε πλακέτα κρυσταλλικού πυριτίου (silicon wafer). H απόδοση της συσκευής αυτής βελτιώνεται ιδίως όσον αφορά στις μη γραμμικές παραμορφώσεις που προσθέτει ο φυσικός μηχανισμός κατά την αναπαραγωγή των ακουστών συχνοτήτων. Για τις ανάγκες της ερευνητικής μελέτης κατασκευάσθηκε εξειδικευμένο στάδιο οδήγησης, ενώ επίσης αναπτύχθηκαν εργαλεία που προσομοιώνουν την απόδοση αυτών των συσκευών. Οι ψηφιακές συστοιχίες μεγαφώνων (DLAs) σήμερα βασίζονται σε μικρούς μετατροπείς κινούμενου πηνίου για την ανακατασκευή ακουστικών σημάτων από ροές ψηφιακού ήχου. Τα σημαντικά ζητήματα απόδοσης για τα συστήματα αυτά αναλύονται από την παρούσα διατριβή, με στόχο να ερμηνευθεί η απόκριση συχνότητας και οι ρυθμοί των διακριτών (on/off) μεταβάσεων των μεγαφώνων, εξαιτίας των ψηφιακών σημάτων. Λεπτομερείς προσομοιώσεις που επιτρέπουν την πραγματοποίηση συγκρίσεων για μια πανομοιότυπη συστοιχία 32 μετατροπέων η οποία τροφοδοτείται από αναλογικά σήματα, σε παρόμοια τοποθέτηση και ενεργοποίηση των στοιχείων. Οι μελέτες αυτές παράγουν πρωτότυπα αποτελέσματα για τις απαιτήσεις σε ηλεκτρική ενέργεια και την ευαισθησία της συστοιχίας, καταλήγοντας στο συμπέρασμα ότι αυτά τα δύο συστήματα επιτυγχάνουν συγκρίσιμες επιδόσεις. / The present Phd Thesis is focused on the study of acoustic transduction systems for direct digital audio signal emission. The research process was based on the evaluation and optimization of the behavior of two different implementations: i. A novel hybrid thermoacoustic device and ii. A loudspeaker array consisting of 32 moving coil speakers designed for digital audio reproduction. Thermoacoustic transduction offers an alternative technique for transducer implementations, based on the transformation of thermal energy fluctuations into sound after the direct application of the electrical audio signal on a solid state device which operates without the use of any moving/mechanical components. Here, an implementation of this sound generation technique is studied based on a prototype developed on silicon wafer and its performance is optimised, especially with respect to non-linear distortions within the audio band. For the purposes of the research study a specialised driving circuit was constructed and also the appropriate tools were developed to simulate the performance of these devices. Digital loudspeaker arrays currently are based on small moving-coil speakers to reconstruct acoustic signals out of binary audio streams. An overview of significant performance issues for such systems is given here to explain frequency response and speaker discrete transition rates due to the digital data. Detailed simulations provided comparisons for a 32-speaker DLA with similar arrangements of speakers driven by analogue signals. These tests produce novel results for electrical power requirements and array sensitivity, concluding that these two systems achieve comparable performance.
367

Self-assembled rolled-up devices: towards on-chip sensor technologies

Smith, Elliot John 29 August 2011 (has links)
By implementing the rolled-up microfabrication method based on strain engineering, several systems are investigated within the contents of this thesis. The structural morphing of planar geometries into three-dimensional structures opens up many doors for the creation of unique material configurations and devices. An exploration into several novel microsystems, encompassing various scientific subjects, is made and methods for on-chip integration of these devices are presented. The roll-up of a metal and oxide allows for a cylindrical hollow-core structure with a cladding layer composed of a multilayer stack, plasmonic metamaterial. This structure can be used as a platform for a number of optical metamaterial devices. By guiding light radially through this structure, a theoretical investigation into the system makeup of a rolled-up hyperlens, is given. Using the same design, but rather propagating light parallel to the cylinder, a novel device known as a metamaterial optical fiber is defined. This fiber allows light to be guided classically and plasmonically within a single device. These fibers are developed experimentally and are integrated into preexisting on-chip structures and characterized. A system known as lab-in-a-tube is introduced. The idea of lab-in-a-tube combines various rolled-up components into a single all-encompassing biosensor that can be used to detect and monitor single bio-organisms. The first device specifically tailored to this system is developed, flexible split-wall microtube resonator sensors. A method for the capturing of embryonic mouse cells into on-chip optical resonators is introduced. The sensor can optically detect, via photoluminescence, living cells confined within the resonator through the compression and expansion of a nanogap built within its walls. The rolled-up fabrication method is not limited to the well-investigated systems based on the roll-up from semiconductor material or from a photoresist layer. A new approach, relying on the delamination of polymers, is presented. This offers never-before-realized microscale structures and configurations. This includes novel magnetic configurations and flexible fluidic sensors which can be designed for on-chip and roving detector applications.
368

Construção de um sistema experimental para desaceleração de átomos. / Construction of an experimental system for stopping atoms.

Firmino, Marcel Eduardo 21 March 1991 (has links)
Neste trabalho apresentamos a construção e teste de um sistema experimental que nos permite produzir um fluxo intenso de átomos lentos. Discutimos o desenho e construção do solenóide que compensa o efeito Doppler que surge durante o processo de desaceleração, as câmaras de vácuo, o forno que gera o feixe atômico e o sistema ótico utilizado. Estudamos a técnica de desaceleração de átomos pelo ajuste Zeeman. Uma nova técnica de observação que consiste no acompanhamento da fluorescência do feixe ao longo do caminho de desaceleração é usada, o que nos permite uma observação direta do processo. / This work presents the development and test of an experimental set-up which allows to produce a very strong slow motion atomic beam. We discuss the calculation and construction of the solenoid to compensate the Doppler effect arising during the deceleration process, vacuum chambers, the oven which produces the atomic beam and the optical system used. We have studied the Zeeman-tuned technique to slow an atomic beam of sodium atoms. A new technique to study the deceleration which Consist in monitoring the fluorescence along the deceleration path is used, which allow us a direct observation of the process.
369

Construção de um sistema experimental para desaceleração de átomos. / Construction of an experimental system for stopping atoms.

Marcel Eduardo Firmino 21 March 1991 (has links)
Neste trabalho apresentamos a construção e teste de um sistema experimental que nos permite produzir um fluxo intenso de átomos lentos. Discutimos o desenho e construção do solenóide que compensa o efeito Doppler que surge durante o processo de desaceleração, as câmaras de vácuo, o forno que gera o feixe atômico e o sistema ótico utilizado. Estudamos a técnica de desaceleração de átomos pelo ajuste Zeeman. Uma nova técnica de observação que consiste no acompanhamento da fluorescência do feixe ao longo do caminho de desaceleração é usada, o que nos permite uma observação direta do processo. / This work presents the development and test of an experimental set-up which allows to produce a very strong slow motion atomic beam. We discuss the calculation and construction of the solenoid to compensate the Doppler effect arising during the deceleration process, vacuum chambers, the oven which produces the atomic beam and the optical system used. We have studied the Zeeman-tuned technique to slow an atomic beam of sodium atoms. A new technique to study the deceleration which Consist in monitoring the fluorescence along the deceleration path is used, which allow us a direct observation of the process.
370

Simulace toroidních cívek v Ansoft Maxwell 3D / Simulation of toroid coils in Ansoft Maxwell 3D

Daněk, Michal January 2009 (has links)
The master thesis is focused on the simulation of the toroid coils in Ansoft Maxwell 3D software, which uses finite element method for electromagnetic field simulation. Firstly the process creation of the geometric model toroid coil with seventy-five threaded is presented. It is necessary to debug this model and prepare it for the mesh generation. Physical properties are assign to this model and it gives rise to the physical model. We will set boundaries, excitation current, core material, winding material and the parameters for the mesh generations. New material Kashke K4000 will be created in the materials library and subsequently we will define its BH curve on the basis of datasheet. Analysis is made in two modes. Direct currents (7,5A; 10A; 15A; 20A; 25A) and (non)linear materials are used in magnetostatic solution. Toroid coil is excited by current pulse in transient solution. In Ansoft Maxwell Circuit editor a source which generates current pulse will be created. This excitation will be assigned to the toroid coil as an extern source through a terminal. Core material is linear in the case of transient analysis, because Ansoft Maxwell 3D doesn´t allow to use nonlinear material in this solution. Settings are different in transient and in magnetostatic analysis. End time and time step are entered to solve this task in transient analysis. Time points are entered too. Flux density and electromagnetic field strength are calculated in these time points and later it will be possible to view the results. Calculated fields are shown as the pictures in this thesis. The procedure how to use a field calculator in the postprocessing is given as well. The achievements are summarized in the conclusion.

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