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Cho, Seong-Ho 1966. "Laser micromachining of active and passive photonic integrated circuits." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30086.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2004.Includes bibliographical references (leaves 149-158).
This thesis describes the development of advanced laser resonators and applications of laser-induced micromachining for photonic circuit fabrication. Two major advantages of laser-induced micromachining are direct patterning and writing on large areas of substrates at high speed following the exposure of laser light, without using complicated photomask steps. For passive photonic devices fabrication, a novel femtosecond laser with unprecedented low repetition rates of 4 MHz is demonstrated to generate high intensity pulses, as high as 1.25 MW with 100 nJ pulse energies and 80 fs pulse durations directly from this laser resonator, without using any active devices or amplifiers. These high intensity pulses are applied to transparent glass materials to demonstrate micromachining of waveguides, gratings, couplers, and three dimensional waveguides and their beam couplings. Active and passive semiconductor devices can be monolithically integrated by employing high energy laser pulses to locally disorder quantum well regions. The 45 nm bandgap shifts at 1.55 ptm with a standard Q-switched Nd:YAG laser at 535 nm are realized. Finally, unidirectional semiconductor ring lasers for high-density integration are developed as a potential application to photonic integrated circuits. Hybrid semiconductor S-crossover and retro-reflected ring lasers, as prototypes for unidirectional operation, are built and result in up to 21.5 dB and 24.5 dB of counter-mode suppression ratio, respectively, which is in good agreement with theoretical predictions.
by Seong-Ho Cho.
Ph.D.
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McCullough, Denis. "Active and passive filters in the control of industrial harmonics." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334582.
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Tee, Chyng Wen. "Vertically-coupled microring architecture for large-scale active-passive integration of photonic circuits." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612543.
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Chirala, Mohan Krishna. "Passive and active circuits in cmos technology for rf, microwave and millimeter wave applications." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2069.
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Sarmiento, Leon Mayra Susana. "Testing platform implementation and system integration for an active/passive imager system including readout circuit design." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.32 Mb., 170 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220740.
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Zanzi, Andrea. "Passive and active silicon photonics devices at TLC telecommunication wavelengths for on-chip optical interconnects." Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/149377.
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[EN] Optical technologies are the backbone of modern communication systems providing
high-speed access to the Internet, efficient inter and intra-data center interconnects
and are expending towards growing research fields and new markets such as satel-
lite communications, LIDARs (Laser Imaging Detection and Ranging) applications,
Neuromorphic computing, and programable photonic circuits, to name a few. Be-
cause of its maturity and low-cost, silicon photonics is being leveraged to allow these
new technologies to reach their full potential.As a result, there is a strong need for
innovative, high-speed and energy-efficient photonic integrated building blocks on
the silicon platform to increase the readiness of silicon photonic integrated circuits.
The work developed and presented in this thesis is focused on the design and char-
acterization of advanced passive and active devices, for photonic integrated circuits.
The thesis consists of three main chapters as well as a motivation and concluding
sections exposing the rationale and the accomplishments of this work. Chapter one
describes the design and characterization of an electro-optical Mach-Zehnder mod-
ulator embedded in highly efficient vertical pn junction exploiting the free-carrier
dispersion effect in the O-band.. Chapter two is devoted to the design and charac-
terization of a novel geometry of asymmetrical multimode interference device and
its implementation in a Mach-Zehnder modulator. Chapter three is dedicated to
the design and characterization of innovative 1-dimensional photonic crystal designs
for slow- lightmodulation applications. An extensive analysis of the main trade-off
arising from the use of slow light is presented.[ES] Las tecnologías ópticas son el eje vertebrador de los sistemas de comunicación mod- ernos que proporcionan acceso de alta velocidad a la Internet, interconexiones efi- cientes entre centros de datos y dentro de ellos. Además, se están expandiendo hacia campos de investigación crecientes y nuevos mercados como son las aplicaciones de comunicaciones por satélite, los LIDAR (Laser Imaging Detection and Ranging), la computación neuromórfica y los circuitos fotónicos programables, por nombrar algunos. La fotónica de silicio está considerada y aceptada ampliamente como una de las tecnologías clave para que dichas aplicaciones puedan desarrollarse. Como resultado, hay una fuerte necesidad de estructuras fotónicas básicas integradas que sean innovadoras, que soporten altas velocidades de transmisión y que sean más eficientes en términos de consumo de potencia, a fin de aumentar la capacidad de los circuitos integrados fotónicos de silicio. El trabajo desarrollado y presentado en esta tesis se centra en el diseño y la car- acterización de dispositivos avanzados pasivos y activos, para circuitos fotónicos integrados. La tesis consta de tres capítulos principales, así como de sendas sec- ciones de motivación y conclusiones que exponen los fundamentos y los logros de este trabajo. El capítulo uno describe el diseño y la caracterización de un modulador electro-óptico Mach-Zehnder incorporado en una unión pn vertical altamente eficien- ciente que explota el efecto de dispersión de plasma en banda O. El capítulo dos está dedicado al diseño y caracterización de una nueva geometría de dispositivo de interferencia multimodo asimétrico y su aplicación en un modulador Mach-Zehnder. El capítulo tres está dedicado al diseño y caracterización de innovadores cristales fotónicos unidimensionales para aplicaciones de modulación con luz lenta. Se pre- senta un amplio análisis de los principales retos derivados del uso de la misma.
[CA] Les tecnologies òptiques són l'eix vertebrador d'aquells sistemes de comunicació moderns que proporcionen accés d'alta velocitat a la Internet, així com intercon- nexions eficients inter i entre centres de dades. A més a més, s'estan expandint cap a camps d'investigació creixents i nous mercats com són les aplicacions de co- municacions per satèl·lit, els LIDAR (Laser Imaging Detection and Ranging), la computació neuromòrfica i els circuits fotònics programables, entre d'altres. La fotònica de silici és considerada i acceptada àmpliament com una de les tecnologies clau i necessàries perquè aquestes aplicacions puguen desenvolupar-se. Per aquest motiu, es fa necessària l'existència d'estructures fotòniques bàsiques integrades que siguen innovadores, que suporten altes velocitats de transmissió i que siguen més eficients en termes de consum de potència, a fi d'augmentar la capacitat dels cir- cuits integrats fotònics de silici. El treball desenvolupat i presentat en aquesta tesi se centra en el disseny i la caracterització de dispositius avançats passius i actius, per a circuits fotònics integrats. La tesi consta de tres capítols principals, així com d'una secció de motivació i una altra de conclusions que exposen els fonaments i els assoliments d'aquest treball. El capítol u descriu el disseny i la caracterització d'un modulador electro-òptic Mach-Zehnder incorporat en una unió pn vertical d'alta efi- ciència que explota l'efecte de dispersió de plasma en la banda O. El capítol dos està dedicat al disseny i caracterització d'una nova geometria de dispositiu d'interferència multimode asimètric així com a la seua aplicació en un modulador Mach-Zehnder. El capítol tres està dedicat al disseny i caracterització d'innovadors cristalls fotònics unidimensionals per a aplicacions de modulació amb llum lenta. S'inclou també una anàlisi detallada dels principals reptes derivats de l'ús d'aquest tipus de llum.
I want to thank you the Generelitat Valenciana and the European Project L3MATRIX for the funding, without them my doctorate would not taken place.
Zanzi, A. (2020). Passive and active silicon photonics devices at TLC telecommunication wavelengths for on-chip optical interconnects [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149377
TESIS
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Al-Bayaty, Hussein Kamal Anwer. "Novel methods of utilization, elimination, and description of the distortion power in electrical circuits." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/10646.
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Firstly, this thesis investigates the electrical power harmonics in an attempt to utilize harmonic current and its distortion power in a novel idea to reconvert the distortion power into useful power. This is done, in order to feed different DC or AC loads in single and three-phase power system by using passive or active filters and accordingly, develop a new topology of hybrid active power filter (HAPF). In addition, this circuit can be considered as a power factor corrector (PFC) because it reduces the total harmonic distortion (THD) and improves the power factor (PF). Secondly, this thesis works on a new design of active power factor correction (APFC) circuit presenting two circuits with the same design principle: the first design consists of two active switches without an external complex control circuit, while the second design contains a single active switch with an additional control circuit. The main contribution of this circuit is 98% reduction of the inductor's value used in the newly proposed PFC circuit in comparison with the conventional boost converter which may lead to a huge reduction in size, weight and the cost of the new PFC circuit. Also, the active switches depend on a carefully designed switching pattern that results in an elimination of the third order harmonic from the input source current which decreases the value of total current harmonic distortion (THDI) to (14%) and improves the input PF to (0.99). Consequently, the simplicity of the design without requiring a complex control circuit and without a snubber circuit plus the minimum size of inductor, gives the newly proposed circuit the superiority on other PFC circuits. Thirdly, this research aims to describe the distortion power through submitting two novel power terms called effective active power (Pef ) & reactive power (Qef ) terms with a new power diagram called Right-Angled Power Triangle (RAPT) Diagram. In addition, a novel de nition of total apparent power (St) has been submitted in order to illustrate the physical meaning of (St) in non-sinusoidal systems. The new RAPT Diagram is based on the orthogonality law and depends on geometrical summation to describe the relationship between different aspects (apparent-active-reactive) of power, and different components (total-fundamental distortion), drawing a bridge to connect the time domain with the frequency domain in a two-dimensional diagram.
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Oliver, John Marcus. "3D Micromachined Passive Components and Active Circuit Integration for Millimeter-wave Radar Applications." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77049.
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The development of millimeter-wave (30-300 GHz) sensors and communications systems has a long history of interest, spanning back almost six decades. In particular, mm-wave radars have applications as automotive radars, in remote atmospheric sensing applications, as landing radars for air and spacecraft, and for high precision imaging applications. Mm-wave radar systems have high angular accuracy and range resolution, and, while susceptible to atmospheric attenuation, are less susceptible to optically opaque conditions, such as smoke or dust. This dissertation document will present the initial steps towards a new approach to the creation of a mm-wave radar system at 94 GHz.
Specifically, this dissertation presents the design, fabrication and testing of various components of a highly integrated mm-wave a 94 Ghz monopulse radar transmitter/receiver. Several architectural approaches are considered, including passive and active implementations of RF monopulse comparator networks. These architectures are enabled by a high-performance three-dimensional rectangular coaxial microwave transmission line technology known as PolyStrataTM as well as silicon-based IC technologies. A number of specific components are examined in detail, including: a 2x2 PolyStrata antenna array, a passive monopulse comparator network, a 94 GHz SiGe two-port active comparator MMIC, a 24 GHz RF-CMOS 4-port active monopulse comparator IC, and a series of V- and W-band corporate combining structures for use in transmitter power combining applications.
The 94 GHz cavity-backed antennas based on a rectangular coaxial feeding network have been designed, fabricated, and tested. 13 dB gain for a 2 x 2 array, as well as antenna patterns are reported. In an effort to facilitate high-accuracy measurement of the antenna array, an E-probe transition to waveguide and PolyStrata diode detectors were also designed and fabricated. AW-band rectangular coaxial passive monopulse comparator with integrated antenna array and diode detectors have also been presented. Measured monopulse nulls of 31.4 dB in the ΔAZ plane have been demonstrated.
94-GHz SiGe active monopulse comparator IC and 24 GHz RF-CMOS active monopulse comparator RFIC designs are presented, including detailed simulations of monopulse nulls and performance over frequency. Simulations of the W-band SiGe active monopulse comparator IC indicate potential for wideband operation, with 30 dB monopulse nulls from 75-105 GHz. For the 24-GHz active monopulse comparator IC, simulated monopulse nulls of 71 dB and 68 dB were reported for the azimuthal and elevational sweeps. Measurements of these ICs were unsuccessful due to layout errors and incomplete accounting for parasitics.
Simulated results from a series of rectangular coaxial power corporate power combining structures have been presented, and their relative merits discussed. These designs include 2-1 and 4-1 reactive, Wilkinson, and Gysel combiners at V- and W-band. Measured back-to-back results from Gysel combiners at 60 GHz included insertion loss of 0.13 dB per division for a 2-1 combination, and an insertion loss of 0.3 dB and 0.14 dB for "planar" and "direct" 4-1 combinations, respectively. At 94 GHz, a measured insertion loss of 0.1 dB per division has been presented for a 2-1 Gysel combination, using a back-to-back structure. Preliminary designs for a solid-state power amplifier (SSPA) structure have also been presented. Finally, two conceptual monopulse transceivers will be presented, as a vehicle for integrating the various components demonstrated in this dissertation.Ph. D.
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Viellard, Juliette. "Etudes des circuits neuronaux organisant l'évitement actif instrumental et l'évitement contextuel non instrumental." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0456.
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Les mammifères, y compris les rongeurs, présentent un large éventail de comportements défensifs actifs, tels que l’évitement, ou passif, tel que l’immobilisation (le freezing), à des fins d’adaptation et de survie. La réponse d'évitement est une réaction apprise dans laquelle un individu prend le contrôle de situations dangereuses pour faire face aux menaces. Une forme d'évitement qui a été étudiée est l'évitement actif signalé, où les individus sont entraînés à éviter une situation et fuient en réponse à un signal précédemment associé à un stimulus aversif. Il a été souligné que le Cortex préfrontal dorso-médian (CPFdm) joue un rôle important dans l’encodage de l’acquisition et de l’expression du freezing ainsi que dans les réponses d’évitement. Cependant, sa contribution à l'acquisition et à l'expression de comportements d'évitement n'est pas claire, et les circuits neuronaux du CPFdm qui gèrent ensemble les stratégies d’adaptation actives et passives, restent à découvrir. Pour répondre à cette question, nous avons développé un nouveau paradigme comportemental dans lequel une souris a la possibilité de se figer ou d’éviter un stimulus aversif en fonctions des contingences contextuelles. Premièrement, nous avons étudié le rôle de la voie entre le CPFdm et la matière grise periaqueducale (PAG) dans l’évitement actif signalé, et sa relation avec le freezing. Nos résultats indiquent que (i) le CPFdm et le dl/lPAG sont activés lors du comportement d'évitement, (ii) et que l'inhibition optogénétique de cette voie bloque l'acquisition de l'évitement conditionné. Une forme d'évitement non instrumental est également étudiée, dans laquelle l'individu apprend à éviter l'environnement aversif en utilisant uniquement des indices contextuels et affichant des comportements d'évaluation des risques à l’encontre de l'environnement dangereux. Il a été précédemment démontré que dans cette situation, un circuit septohippocampale-hyptothalamique-tronc cérébrale est spécialement activé. Cette analyse a aussi révélé que le noyau dorsal pré-mamillaire (PMD) devait être impliqué de manière critique dans l'évitement passif contextuel. Nous avons analysé l'influence de la modulation du PMD et de ses projections au niveau de ses cibles principales, sur le processus d'expression et de reconsolidation de l'évitement passif contextuel. Nos résultats ont montré qu’une (i) voie septohippocampale-hyptothalamique-tronc cérébrale spécifique était impliquée dans notre paradigme d’évitement passif. (ii) De plus, l’inhibition du PMD lors d'une exposition au contexte aversif altère à la fois l'expression des comportements d'évitement et la reconsolidation de la mémoire. (iii) Enfin l’inhibition au niveau des terminaux du PMD altère l'expression et la reconsolidation de la mémoire dans le dlPAG et dans l’AMv. Les expériences de ce projet ont été menées à bien à l’aide d’analyse Fos, d'inhibition pharmacogénétique et optogénétiquesMammals, including rodents show a broad range of defensive behaviors as a mean of coping actively, such as avoidance behaviors, or passively such as freezing behavior. The avoidance response is a learned response in which an individual takes control in dangerous situations to deal with threats. One form of avoidance that has been investigated is the signaled active avoidance, where individuals are trained to avoid an environment, and escape in response to a cue previously associated with an aversive stimulus. It has been emphasized that the dmPFC plays an important role in encoding freezing acquisition and expression as well as active avoidance responses. However the neural circuits of the dmPFC processing the expression and acquisition of both active and passive coping strategies are yet to be discovered. To adress this question, we developed a novel behavioral paradigm in which a mouse has the possibility to either passively freeze to an aversive stimulus or to actively avoid it as a function of contextual contingencies. We first investigated the role of the pathway between the dmPFC and PAG in signaled active avoidance, and its relation with freezing. Our results indicate that (i) dmPFC and dl/lPAG sub-regions are activated during avoidance behavior, (ii) and that the optogenetic inhibition of this pathway blocked the acquisition of active avoidance. A non-instrumental form of avoidance is also investigated where the individual learns to avoid the aversive environment using contextual clues only, and displaying risk assessment behaviors toward the fearful environment. It has been previously shown that in this situation, a circuit involving the septohippocampal-hypothalamic-brainstem pathway is involved. It also revealed that the dorsal premammillary nucleus (PMD) must be critically involved in contextual passive avoidance. We analysed how the manipulation of the PMD and its projections to its main targets influences the expression and reconsolidation processes of contextual passive avoidance. Our results showed that (i) a specific septohippocampal-hypothalamic-braintem pathway is involved in our passive avoidance paradigm. (ii) Silencing the PMD during context exposure impairs both avoidance expression and memory reconsolidation and that (iii) the inhibition at terminal level impairs the expression and memory reconsolidation in both dlPAG and AMv. Both parts of the project assessed these questions using Fos immunochemistry analysis, manipulations of neural circuits using optogenetic, and pharmacogenetic techniques
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Santos, Heinsten Frederich Leal dos. "Controle de vibrações estruturais usando cerâmica piezoelétricas em extensão e cisalhamento conectadas a circuitos híbridos ativo-passivos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-28082009-170649/.
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Esta dissertação apresenta uma análise numérica do controle de vibrações estruturais através de cerâmicas piezoelétricas em extensão e em cisalhamento conectadas a circuitos ativo-passivos compostos por resistência, indutância e fonte de tensão. Para tal, um modelo de elementos finitos de vigas sanduíche com três camadas elásticas e/ou piezoelétricas foi desenvolvido. Realizou-se também uma modelagem dos componentes do circuito elétrico e seu acoplamento à estrutura gerando assim uma equação de movimento acoplada para a estrutura com elementos piezoelétricos conectados aos circuitos elétricos. Uma análise harmônica das equações obtidas foi realizada para se obter uma avaliação preliminar dos efeitos causados pelos componentes elétricos do circuito na estrutura. Observou-se que os elementos passivos do circuito, resistência e indutância, tem não somente um efeito de absorvedor dinâmico de vibrações mas, também, promovem uma amplificação da autoridade de controle no caso de se atuar através da fonte de tensão. Usando a metodologia tradicional de projeto de absorvedores dinâmicos de vibrações, derivou-se expressões para os valores de resistência e indutância de modo a maximizar o desempenho passivo do sistema. Uma análise numérica do desempenho na redução das amplitudes de vibração em um viga engastada-livre com uma cerâmica piezoelétrica em extensão ou cisalhamento foi realizada mostrando bons resultados. Em seguida, uma análise da autoridade de controle para estas estruturas foi realizada visando a implementação de um controle híbrido ativo-passivo. A parcela ativa do controle foi obtida usando-se uma estratégia de controle por retroalimentação ótima do tipo linear quadratic regulator para calcular a tensão aplicada ao circuito. Uma comparação entre os resultados mostra que o controle híbrido ativo-passivo é sempre superior aos controles puramente ativos ou passivo para os dois casos estudados, com cerâmicas piezoelétricas em extensão e cisalhamento.This work presents a numerical analysis of the structural vibration control using piezoelectric materials in extension and shear mode connected to active-passive electric circuits composed of the resistance, inductance and voltage source. For that, a finite element model for sandwich beams with three elastic or piezoelectric layers was developed. A modeling of the electric circuit dynamics and its coupling to the structure with piezoelectric elements was also done. A harmonic analysis of the resulting equations was performed to yield a preliminary evaluation of the effects caused by the electric circuit components on the structure. It was observed that the passive circuit components not only lead to a dynamic vibration absorber effect but also to an amplification of the control authority in case of actuation using the voltage source. Using the standard methodology for the design of dynamic vibration absorbers, expressions were derived for the resistance and inductance values that optimize the passive vibration control performance of the system. A numerical analysis of the passive vibration control was performed for cantilever beams with extension and shear piezoelectric ceramics showing satisfactory results. Then, an analysis of the control authority was carried out for the same structures aiming at an active-passive vibration control. The active control was achieved using a linear quadratic regulator optimal feedback strategy to evaluate the voltage applied to the circuit. A comparison between the obtained results show that hybrid active-passive control is always superior to the purely active or purely passive control for both cases studied, with extension and shear piezoelectric ceramics.
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Eleyele, Abidemi Oluremilekun. "Isolated Single-Stage Interleave Resonant PFC Rectifier with Active and Novel Passive Output Ripple Cancellation Circuit." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423117.
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With the increasing demand for fast, cheaper, and efficient power converters come the need for a single-stage power factor correction (PFC) converter. Various single-stage PFC converter proposed in the literature has the drawback of high DC bus voltage at the input side and together with the shift to wide bandgap switches like GaN drives the converter cost higher. However, an interleaved topology with high-frequency isolation was proposed in this research work due to the drastic reduction in the DC bus voltage and extremely low input current ripple thereby making the need for an EMI filter circuit optional. Meanwhile, this research work focuses on adapting the proposed topology for a high voltage low current application (EV charger - 400V, 7KW) and low voltage high current application (telecom power supply - 58V, 58A) owing to cost benefits. However, all single-stage PFC are faced with the drawback of second-order (100Hz) output harmonic ripple. Therefore, the design and simulation presented a huge peak to peak ripple of about 50V/3A and 26V/26A for the EV charger and telecom power supply case, respectively. This created the need for the design of a ripple cancellation circuit as the research required a peak to peak ripple of 8V and 200mV for the EV - charger and telecom power supply, respectively. A novel output passive ripple cancellation technique was developed for the EV charger case due to the ease it offers in terms of control, circuit complexity and extremely low THDi when compared with the active cancellation approach. The ripple circuit reduced the 50V ripple to 431mV with the use of a total of 2.2mF capacitance at the output stage. Despite designing the passive technique, an active ripple cancellation circuit was designed using a buck converter circuit for the telecom power supply. The active approach was chosen because the passive has a slow response and incurs more loss at a high current level. Adding the active ripple cancellation circuit led to a quasi-single stage LLC PFC converter topology. A novel duty-ratio feedforward control was added to synchronize the PFC control of the input side with the buck topology ripple cancellation circuit. The addition of the ripple circuit with the feedforward control offered a peak to peak ripple of 6.7mV and a reduced resonant inductor current by half. After analysis, an extremely low THDi of 0.47%, PF of 99.99% and a peak efficiency of 97.1% was obtained for the EV charger case. The telecom power supply offered a THDi of 2.3%, PF of 99.96% with a peak efficiency of 95%.
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Zhu, Ning. "Electrically Small, Near-Field Resonant Parasitic (NFRP) Antennas Augmented with Passive and Active Circuit Elements to Enhance their Functionality." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/297013.
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Metamaterials have drawn considerable attention because they can exhibit epsilon-negative (ENG) and/or mu-negative (MNG) properties, which in turn can lead to exotic physical effects that can enable interesting, practical applications. For instance, ENG and MNG properties can be engineered to yield double negative (DNG) properties, such as a negative index of refraction, which leads to flat lenses. Similarly, their extreme versions enable cloaking effects. Inspired by such metamaterial properties, a promising methodology has been developed to design electrically small antennas (ESAs). These ESAs use unit cells of metamaterials as their near-field resonant parasitic (NFRP) elements. This new metamaterial-inspired antenna miniaturization method is extended in this dissertation by augmenting the antenna designs with circuits. A rectifying circuit augmentation is used to achieve electrically small, high efficiency rectenna systems. Rectennas are the enabling components of power harvesting and wireless power transmission systems. Electrically small, integrated rectennas have become popular and in demand for several wireless applications including sensor networks and bio-implanted devices. Four global positioning system (GPS) L1 frequency (1.5754 GHz) rectenna systems were designed, fabricated and measured: three resistor-loaded and one supercapacitor-loaded. The simulated and measured results will be described; good agreement between them was obtained. The NFRP ESAs are also augmented with active, non-Foster elements in order to overcome the physical limits of the impedance bandwidth of passive ESA systems. Unlike conventional active external matching network approaches, the non-Foster components are incorporated directly into the NFRP element of the ESA. Three 300 MHz non-Foster circuit-augmented broadband, ESA systems were demonstrated: an Egyptian axe monopole (EAM) antenna, an Egyptian axe dipole (EAD) antenna, and a protractor antenna. The simulated and measured results will be described; reasonable agreement between them was obtained. Moreover, a deeper practical engineering understanding of how lumped components with tighter tolerances, more accurate transistor models, and integrated circuit-based implementations will lead to more satisfactory performance characteristics of the non-Foster circuit-augmented ESAs was accomplished and is also reported.
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Pascal, Yoann. "Étude multicritère pour l'enfouissement partiel ou total de convertisseurs d'électronique de puissance dans un circuit imprimé." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN038/document.
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Les travaux présentés dans ce manuscrit traitent de l’enfouissement dans un circuit imprimé de convertisseurs de puissance, paradigme visant l’insertion de composants électroniques au sein du circuit imprimé.Une structure simple et économique de composant inductif enfoui, pouvant être employé comme inductance, coupleur, ou résonateur monolithique, est tout d’abord décrite. Un modèle analytique complet est développé. Des prototypes sont réalisés, validant le modèle et démontrant l’intérêt de la topologie.L’agencement des composants de puissance constituant une cellule de commutation est ensuite étudié. En particulier, un modèle analytique permettant une compréhension intuitive des mécanismes oscillatoires dans le cadre de l’emploi de transistors rapides est décrit.Une technique de reprise de contact de face avant pour puce enfouie, basée sur un morceau de mousse pressée, est proposée. Une étude préliminaire, à forte composante expérimentale, est présentée. Elle démontre que certains prototypes enfouis présentent des caractéristiques électriques et une fiabilité similaires à celles obtenus avec des fils de bonding.Enfin, les résultats de l’étude sur l’agencement des composants d’une cellule de commutation sont appliqués pour concevoir et réaliser un hacheur basé sur des transistors SiC connectés par mousse pressée. La structure délivre 3 kW sous 600 V en continu, démontrant la viabilité du procédé de reprise de contact proposéThis thesis deals with Printed-Circuit Board (PCB) embedding of power converters, paradigm according to which electronic components are placed within the substrate itself.First, a simple and economical structure of inductive component, which can be used either as an inductor, a coupler, or a monolithic resonator, is described. A comprehensive analytical model is developed. Prototypes are manufactured, validating the analytical model and highlighting the value of the topology.The arrangement of the power components of a switching cell is then studied. In particular, an analytical model offering an intuitive understanding of the oscillation mechanisms in cells using fast transistors is proposed.A simple and economical top-side connection technic for PCB-embedded power dies using a pressed piece of metal foam is described. A preliminary study, with strong experimental component, is proposed. It shows that the embedded prototypes have electrical performances and a reliability close to that of wire-bonded dies.Finally, the results from the study on the arrangement of the components of a switching cell are used to design and manufacture a chopper based on SiC transistors connected using a piece of pressed metal foam. This chopper proved to be able to continuously deliver 3 kW under 600 V to a load, thereby validating the proposed top-side connection technic
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Santos, Heinsten Frederich Leal dos. "Controle ativo-passivo de vibrações estruturais usando materiais piezelétricos: otimização e quanticação de incertezas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-11052015-100332/.
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Esta tese apresenta uma análise numérica do controle de vibrações estruturais através de cerâmicas piezelétricas em extensão conectadas a circuitos ativo-passivos compostos por resistência, indutância e fonte de tensão. Para tal, um modelo de elementos finitos de vigas sanduíche com três camadas elásticas e/ou piezelétricas foi desenvolvido. Realizou-se também uma modelagem dos componentes do circuito elétrico e seu acoplamento à estrutura gerando assim uma equação de movimento acoplada para a estrutura com elementos piezelétricos conectados aos circuitos elétricos. Uma análise harmônica das equações obtidas foi realizada para se obter uma avaliação preliminar dos efeitos causados pelos componentes elétricos do circuito na estrutura. Observou-se que os elementos passivos do circuito, resistência e indutância, tem não somente um efeito de absorvedor dinâmico de vibrações mas, também, promovem uma amplificação da autoridade de controle no caso de se atuar através da fonte de tensão. Usando a metodologia tradicional de projeto de absorvedores dinâmicos de vibrações, derivou-se expressões para os valores de resistência e indutância de modo a maximizar o desempenho passivo do sistema. Uma análise do efeito de incertezas das constantes piezelétricas e dielétricas da cerâmica piezelétrica considerada e dos componentes de resistência e indutância do circuito elétrico no desempenho do controle passivo e ativo-passivo de estrutura tipo viga cantilever foi realizada. O objetivo desta análise foi quantificar robustez e sensibilidade do controle proposto. Em sequida, um estudo de otimização dos valores de resistência e indutância do circuito elétrico em função da tensão elétrica de controle máxima a ser aplicada em uma placa com diversos atuadores piezelétricos foi realizado. Finalmente e também para a estrutura tipo placa, uma análise de incertezas da rigidez da cola na interface entre estrutura e atuadores piezelétricos e seus efeitos no desempenho do controle passivo e ativo-passivo foi realizada.This work presents a numerical analysis of the structural vibration control using piezoelectric materials in extension mode connected to active-passive electric circuits composed of resistance, inductance and voltage source. For that, a finite element model for sandwich beams with three elastic or piezoelectric layers was developed. A modeling of the electric circuit dynamics and its coupling to the structure with piezoelectric elements was also done. A harmonic analysis of the resulting equations was performed to yield a preliminary evaluation of the effects caused by the electric circuit components on the structure. It was observed that the passive circuit components not only lead to a dynamic vibration absorber effect but also to an amplification of the control authority in case of actuation using the voltage source. Using the standard methodology for the design of dynamic vibration absorbers, expressions were derived for the resistance and inductance values that optimize the passive vibration control performance of the system. An analysis of the effect of uncertainties of piezoelectric and dielectric constants of piezoelectric ceramic and resistance and inductance components of the shunt circuit on the passive and active-passive control performance for a cantilever beam structure was performed. The objective of this analysis was to quantify robustness and sensitivity of the proposed control. Then, an optimization study of the values of resistance and inductance of the shunt circuit as a function of the maximum control voltage to be applied on a plate with several piezoelectric actuators was performed. Finally and also for the plate structure, an analysis of uncertainties in the stiffness of the adhesive interface between structure and piezoelectric actuators and their effects on the performance of passive control and active-passive was performed.
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Settaf, Zakaria. "Étude et réalisation d'un duplexeur SOI accordable multibande pour les futures générations de systèmes de téléphonie mobile." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2327/document.
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Plusieurs standards de téléphonie mobile ont été définis et sont utilisés actuellement. Dans un avenir proche, avec le développement de la 5G de nouveaux standards et de nouvelles bandes de fréquence faire leur apparition. De ce fait, avec l'utilisation de nombreux circuits dédiés à un standard et donc à une bande de fréquence, des difficultés d'intégration et desproblèmes de coûts apparaissent. Il est donc devenu nécessaire pour les concepteurs de proposer des circuits intégrés reconfigurables pour plusieurs gammes de fréquences avec des modes de fonctionnement différents.Dans un système d'émetteur récepteur, le duplexeur permet l'établissement d'une communication simultanée en utilisant une seule antenne pour la transmission et la réception de données, sans que celles-ci soient corrompues. C'est un composant vital, surtout pour la chaine de réception car la réception du signal désiré dépend de ses caractéristiques. Ce dispositif est conçu sur du matériau piézoélectrique, qui ne permet pas d'obtenir un filtre agile en fonction de la fréquence. Dans ce contexte, il est intéressant de rechercher une nouvelle architecture de duplexeur, permettant une réalisation intégrée et un fonctionnement agile.Plusieurs architectures de duplexeur ont été retenues en se basant sur des études récentes menées dans différentes équipes de recherche. Un classement de ces architectures a été proposé, avec des améliorations pour les rendre intégrables et reconfigurables. Parmi toutes les solutions de duplexeurs passifs étudiées, le duplexeur à coupleur hybride 3dB est unesolution permettant d'obtenir des performances attractives. Les simulations pour différentes bandes de fréquences ont montré qu’il était difficile de respecter les spécifications de l’isolation Tx/Rx. Des solutions possibles ont été présentées et des modifications de la structure d'un amplificateur du LNA ont été évaluées en simulation. Ainsi, les performancesd’isolation peuvent être améliorées grâce à des structures actives d’annulation du signal résiduel Tx.La conception, la réalisation et le test de coupleurs hybrides et duplexeurs sont présentés. Le circuit a été implémenté en utilisant la technologie SOI 0.13 micromètre de ST Microelectronics et mesuré avec un boitier BT soudé sur un support de test PCB. Les performances RF du duplexeur peuvent être ajustées en fonction de la bande de fréquence désirée grâce aux capacités commutées. Les performances RF du coupleur hybride 3dB permettent d’envisager l’application de la structure proposée pour les futurs développements de systèmes de téléphonieSeveral standards have been defined and are currently used on mobile phones. With the high request for the broadband, several new standards are developed and introduced in 5G. This results in the use of many circuits, dedicated to one standard and thus one frequency band, which increase the difficulty of integrating these dedicated circuits and therefore costly. It hasbecome necessary for designers to propose tunable integrated circuit that can address several frequency ranges with different operating modes.The duplexer allows the establishment of simultaneous communications, using a single antenna for sending and receiving data, without any interferences. It is a vital component, especially for receiver. In fact, the quality of the received signal depends greatly on the duplexer characteristics. This device is designed on the piezoelectric material, which does not allow to achieve a tunable filter according to the frequency. In this context, it seems interesting to study a new architecture of duplexer. Therefore, it is necessary to define the duplexer function based on studies and system simulations, thus identify the constraints and technology limitations. Several duplexer architectures were selected based on recent studies in different research teams.A classification of these architectures was proposed and also improvements to make them integrated and tunable. Among all the solutions studied, the duplexer using hybrid 3dB coupler shown the most attractive performance. Simulations for different frequency bands showed that it's difficult to achieve Tx/Rx isolation requirements. Different solutions have been presented and LNA structure have been changed and thus evaluated by simulations. Thanks to that, the Tx/Rx isolation can be improved through active cancellation structures.The final chapter presents the design, implementation and testing of hybrid 3dB coupler and duplexer. It has been implemented using SOI 0.13 micrometer from ST Microelectronics and tested on BT-resin substrat. The RF performance of the duplexer can be corrected according to the desired frequency band through the switched capacitor. The RF performance of the hybrid 3dB coupler is in the line with expectations and allows to consider its integration in future system developments
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Do, Minh-Nhut. "Co-conception et caractérisation de circuits actifs et passifs tri-dimensionnels en bande K pour l'intégration de mycrosystèmes sur silicium aux fréquences milimétriques." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00196619.
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Les travaux menés dans le cadre de cette thèse proposent de tirer profit des nouvelles technologies disponibles pour répondre aux besoins de la montée en fréquence et de la miniaturisation des systèmes de communication tout en améliorant le niveau des performances. Les études se sont axées vers la conception d'une structure à mélangeur de réjection de fréquence image permettant de relâcher les contraintes sur les structures critiques de filtrage amont. L'intégration des parties actives et passives de ce système, a ainsi été menée avec comme objectifs de tirer au maximum partie des potentialités de chaque technologie, de proposer des solutions techniques pour palier aux inconvénients de chaque technologie, et d'optimiser l'architecture globale en partitionnant le système suivant les contraintes technologiques et/ou techniques. La première partie des travaux a ainsi porté sur le développement en bande K d'une nouvelle topologie de mélangeur à base de transistors à hétérojonction Si-SiGe à linéarité améliorée. Se basant sur une compréhension des phénomènes intrinsèques du circuit, des topologies modifiées ont de plus été proposés afin de repousser l'ensemble des performances atteignables sur cette technologie. La seconde partie des travaux concerne la conception de coupleurs passifs, toujours en bande K, avec pour objectif la miniaturisation maximale de ces fonctions. Une méthodologie de conception a, dans ce cadre, été développée et validée par une intégration sur une technologie spécifiquement développée au LAAS-CNRS et compatible avec une future intégration avec les circuits actifs. Nous avons ainsi obtenu des performances optimales (à l'état de l'art) avec un gain d'intégration d'un facteur 2. Enfin, en amont et en aval de ces travaux, une étude sur l'architecture globale du système de mélangeur à réjection de fréquence image a été conduite, et sans cesse raffinée, afin de partitionner les contraintes de performances entre les différents blocs et de vérifier l'obte ntion des performances.
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Pourabdollah, Nezhad Maziar. "Active and passive plasmonic devices." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3284224.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed January 14, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 93-102).
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Zuo, Fei. "Passive and active currency portfolio optimisation." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/22612.
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This thesis examines the performance of currency-only portfolios with different strategies, in out-of-sample analysis. I first examine a number of passive portfolio strategies into currency market in out-of-sample analysis. The strategies I applied in this chapter include sample-based mean-variance portfolio and its extension, minimum variance portfolio, and equally-weighted risk contribution model. Moreover, I consider GDP portfolio and Trade portfolio as market value portfolio for currency market. With naïve portfolio, there are 12 different asset allocation models. In my out-of-sample analysis, naïve portfolio performs reasonably well among all 12 portfolios, and transaction cost does not seriously affect the results prior to transaction cost analysis. The results are robust across different estimation windows and perspectives of investors from different countries. Next, more portfolio strategies are examined to compare with naïve portfolio in currency market. The first portfolio strategy called ‘optimal constrained portfolio’ in this chapter is derived from the idea of maximising the quadratic utility function. In addition, the timing strategies, a set of simple active portfolio strategies, are also considered. In my out-of-sample analysis with rolling sample approach, naïve portfolio can be beaten by all the strategies discussed in this chapter. In chapter six, the characteristics of currency are exploited to construct a currency only portfolio. Firstly, the pre-sample test proves that the characteristics, both fundamental and financial, are relevant to the portfolio construction. I then examine the performance of parametric portfolio policies. The results show that while fundamental characteristics can bring investor benefits of active portfolio management, financial characteristics cannot. Moreover, I find the relationship between characteristics of currency and weights of optimal portfolio. The overall results show that currencies can be thought of as an asset in their own right to construct optimal portfolios, which have better performance than naïve portfolio, if suitable strategies are used. In addition, ‘lesser’ currencies, indeed, bring significant benefits to the investors.
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Maldonado-Mercado, Julio Cesar. "Passive and active control of structures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36654.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.Includes bibliographical references (leaves 94-98).
by Julio Cesar Maldonado-Mercado.
M.S.
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Scheitrum, Raquel. "Smoking passive addiction or active coping? /." Instructions for remote access. Click here to access this electronic resource. Access available to Kutztown University faculty, staff, and students only, 1999. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.A.)--Kutztown University of Pennsylvania, 1999.Source: Masters Abstracts International, Volume: 45-06, page: 2778. Typescript. Abstract included as two unpaged leaves at back of volume. Includes bibliographical references (leaves 30-35).
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Kartha, Satish Chandrashekhar. "Active, Passive and Active/Passive Control Techniques For Reduction of Vibrational Power Flow in Fluid Filled Pipes." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31156.
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The coupled nature of vibrational energy flow in fluid filled piping systems makes its control and subsequent reduction a difficult problem. This work experimentally explores the potential of different active, passive and active/passive control methodologies for control of vibrational power flow in fluid filled pipes. Circumferential modal decomposition and measurements of vibrational power carried by individual wave types were carried out experimentally. The importance of dominant structural bending waves and the need to eliminate them in order to obtain meaningful experimental results has been demonstrated. The effectiveness of the rubber isolator in reducing structural waves has been demonstrated. Improved performance of the quarter wavelength tube and Helmholtz resonator was obtained on implementation of the rubber isolator on the experimental rig. Active control experiments using the side-branch actuator and 1/3 piezoelectric composite yielded significant dB reductions revealing their potential for practical applications. A combined active/passive approach was also implemented as part of this work. This approach yielded promising results, which proved that combining advantages of both active and passive approaches was a feasible alternative.Master of Science
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Hassan, Samy Aly. "Fundamental studies of passive, active and semi-active automotive suspension systems." Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/2691/.
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The fundamental properties of various automotive suspension systems are theoretically investigated on the basis of simple vehicle models subjected to realistic inputs chosen to represent road surfaces of different qualities. The vehicle response is evaluated through a performance index representing ride comfort, dynamic tyre load and suspension working space parameters, and interpreted in the light of these individual parameters together with the implications of the suspension design for attitude control and steering behaviour. Linear analysis procedures are followed in studying the passive, active and slow-active suspension systems while suitable simulations are used for the non-linear semi-active suspension systems. Linear optimal control theory is used to determine the optimal parameters of the active and slow-active suspension systems. Semi-active suspension behaviours are evaluated on the basis of applying the optimal active parameters to each system, but the semi-active damper can only dissipate energy and switches off when external power would be needed for the system to follow the optimal active control law. Results are generated and discussed for each of these types of system and their performance capabilities are compared with each other. Conclusions concerning the practical viability of each of the systems are drawn.
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Kim, Sangcheol. "Fabrication of active and passive terahertz structures." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 60 p, 2006. http://proquest.umi.com/pqdweb?did=1203570961&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Garcia, Nil. "Optimization Methods for Active and Passive Localization." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14192/1/garcia.pdf.
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Active and passive localization employing widely distributed sensors is a problem of interest in various fields. In active localization, such as in MIMO radar, transmitters emit signals that are reflected by the targets and collected by the receive sensors, whereas, in passive localization the sensors collect the signals emitted by the sources themselves. This dissertation studies optimization methods for high precision active and passive localization. In the case of active localization, multiple transmit elements illuminate the targets from different directions. The signals emitted by the transmitters may differ in power and bandwidth. Such resources are often limited and distributed uniformly among the transmitters. However, previous studies based on the well known Crámer-Rao lower bound have shown that the localization accuracy depends on the locations of the transmitters as well as the individual channel gains between different transmitters, targets and receivers. Thus, it is natural to ask whether localization accuracy may be improved by judiciously allocating such limited resources among the transmitters. Using the Crámer-Rao lower bound for target localization of multiple targets as a figure of merit, approximate solutions are proposed to the problems of optimal power, optimal bandwidth and optimal joint power and bandwidth allocation. These solutions are computed by minimizing a sequence of convex problems. The quality of these solutions is assessed through extensive numerical simulations and with the help of a lower-bound that certifies their optimality. Simulation results reveal that bandwidth allocation policies have a stronger impact on performance than power. Passive localization of radio frequency sources over multipath channels is a difficult problem arising in applications such as outdoor or indoor geolocation. Common approaches that combine ad-hoc methods for multipath mitigation with indirect localization relying on intermediary parameters such as time-of-arrivals, time difference of arrivals or received signal strengths, are unsatisfactory. This dissertation models the localization of known waveforms over unknown multipath channels in a sparse framework, and develops a direct approach in which multiple sources are localized jointly, directly from observations obtained at distributed sources. The proposed approach exploits channel properties that enable to distinguish line-of-sight (LOS) from non-LOS signal paths. Theoretical guarantees are established for correct recovery of the sources’ locations by atomic norm minimization. A second-order-cone-based algorithm is developed to produce the optimal atomic decomposition, and it is shown to produce high accuracy location estimates over complex scenes, in which sources are subject to diverse multipath conditions, including lack of LOS.
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Oh, Yim-Taek. "Passive and active drag of paralympic swimmers." Thesis, Manchester Metropolitan University, 2015. http://e-space.mmu.ac.uk/615953/.
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The aim of this thesis was to contribute to the development of an objective, evidence-based international classification system for para-swimmers by quantifying the effect of physical impairment on passive and active drag. The thesis comprises five studies. Study 1 identified a significant relationship between normalised passive drag and the para-swimmers’ International Paralympic Committee (IPC) Class, but an inconsistent difference in normalised passive drag between adjacent classes. High within-class variability in passive drag indicates that the current classification system does not always differentiate clearly between swimming groups. Study 2 found that anthropometric features of para-swimmers, such as height and body mass, differed significantly between IPC Classes, whereas Shoulder Width, Chest Depth, Shoulder Girth and Torso Girth did not. A weak correlation existed between para-swimmers’ anthropometry and their passive drag, which indicates that other factors, such as impairment type, may be more important predictors of passive drag than anthropometry. Study 3 revealed that certain impairments, such as double-leg amputation above knee level, may predispose a para-swimmer to a relatively high passive drag which disadvantages them in competition. Study 4 compared two methods of estimating active drag during front crawl swimming: the Naval Architecture Based Approach (NABA) and the Active Towing Method (ATM). The means were not statistically different. Using a sensitivity analysis, the NABA was identified as the more reliable method of assessing active drag. Study 5 found that active and passive drag of elite para-swimmers are highly correlated but no relationship existed between active drag and International Paralympic Committee S Class (IPC S Class), indicating that factors other than impairment level may be more important in determining active drag. The relationships discovered between drag, IPC Class, anthropometry and impairments will contribute to the development of the future IPC Classification system.
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Al-Mahmoud, Abdulrazzak M. "Microwave passive tunable and active bandpass filters." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309711.
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Campillo, Javier. "From Passive to Active Electric Distribution Networks." Doctoral thesis, Mälardalens högskola, Framtidens energi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-31592.
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Large penetration of distributed generation from variable renewable energy sources, increased consumption flexibility on the demand side and the electrification of transportation pose great challenges to existing and future electric distribution networks. This thesis studies the roles of several actors involved in electric distribution systems through electricity consumption data analysis and simulation models. Results show that real-time electricity pricing adoption in the residential sector offers economic benefits for end consumers. This occurs even without the adoption of demand-side management strategies, while real-time pricing also brings new opportunities for increasing consumption flexibility. This flexibility will play a critical role in the electrification of transportation, where scheduled charging will be required to allow large penetration of EVs without compromising the network's reliability and to minimize upgrades on the existing grid. All these issues add significant complexity to the existing infrastructure and conventional passive components are no longer sufficient to guarantee safe and reliable network operation. Active distribution networks are therefore required, and consequently robust and flexible modelling and simulation computational tools are needed for their optimal design and control. The modelling approach presented in this thesis offers a viable solution by using an equation-based object-oriented language that allows developing open source network component models that can be shared and used unambiguously across different simulation environments.
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Zhou, Shaoyi. "Advances in passive and active damping techniques." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI066.
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Les systèmes mécaniques (e.g. structures flexibles) sont généralement peu amortis, et par conséquent des vibrations de fortes amplitudes peuvent apparaitre. Il apparait nécessaire de développer des stratégies de contrôle vibratoire pour atténuer ces vibrations mécaniques. Cette thèse a pour objectif de développer plusieurs techniques d'amortissement de vibration passives ou actives. La première partie porte sur l'utilisation d'un “inerter” pour améliorer les performances de contrôle vibratoire de deux dispositifs existants, l'amortisseur à masse accordée (TMD) et deux TMDs placés en série (SDTMD). Dans le cas avec un TMD, on considère un système mécanique avec incertitudes ainsi que son optimisation H-infinity (worst-case optimization) en adoptant une approche purement algébrique. Dans le cas de SDTMD, on vise à contrôler la vibration d'un système déterministe. Son optimisation H-infinity s'effectue ici en utilisant une version étendue de la théorie de points fixes (FPT). Dans une seconde partie, on cherche à améliorer les performances de ce type de dispositif en positionnant un élément linéaire de raideur négative entre la base et la masse accordée. Deux cas d'étude sont menés: le TMD seul et celui basé sur l'inerter (IDVA). Les deux dispositifs ont une configuration non-traditionnelle, dont la masse accordée est liée à la base par l'intermédiaire d'un amortisseur visqueux ou un réseau mécanique basé sur l'inerter. La réalisation de ces dispositifs non-traditionnelles avec ou sans raideur négative et leurs shunts piézoélectriques sont étudiés et une analogie électromécanique est établie. Cette analogie permet d'étendre l'applicabilité des amortisseurs mécaniques et de faciliter les réglages. Dans la dernière partie, deux techniques d'amortissement actif et semi-actif sont développées. La première stratégie concerne une loi de contrôle hybride applicable au TMD et à l'IDVA. Le contrôleur proposé est composé d'un seul ou plusieurs compensateurs identiques, qui est caractérisé par un pôle à l'origine et deux zéros coïncidents réels. Les expressions analytiques sont développées dans les deux cas. La seconde technique de contrôle s'appuie sur l'atténuation de vibration par shunt électromagnétique (EMSD), pour laquelle aucun capteur est requis. Une inductance négative (NI) est employée dans les shunts électromagnétiques afin d'améliorer l'amortissement. Trois architectures possibles de NI dans un EMSD sont évaluées à travers le facteur de couplage électromécanique, qui quantifie l'efficacité de conversion énergétique entre les domaines mécanique et électrique. Finalement, six shunts électromagnétiques utilisant des NIs sont optimisés et analysésMechanical systems (e.g. flexible structures) are usually lightly damped so that they vibrate severally in response to dynamic loads. Therefore, vibration control strategies should be adopted in order to reduce the undesired vibration of mechanical systems. The objective of this thesis is to develop multiple vibration control techniques, which are either passive or active. The first part focuses on the application of inerter to enhance the vibration control performance of two existing control devices, the tuned mass damper (TMD) and the series double TMD (SDTMD). The inerter is employed to relate the tuned mass to the ground. In the case of TMD, a mechanical system under stiffness uncertainty is considered and the worst-case H-infinity optimization is addressed by means of an entirely algebraic approach. In the case of SDTMD, the vibration of a deterministic mechanical system is to be controlled and the H-infinity optimal design is carried out via an extended version of fixed points theory (FPT). Instead of using the inerter, the second part consists in improving the control effect by incorporating a linear negative stiffness between the ground and the tuned mass. Two case studies are conducted based on the non-traditional TMD and inerter-based dynamic vibration absorber (IDVA), whose tuned mass is related to the ground by a viscous damper or an inerter-based mechanical network, respectively. Later, the exact electrical realization of non-traditional configurations with or without negative stiffness is proposed, which is based on the piezoelectric transducer enclosed by a particular shunt circuit. This electromechanical analogy enables to extend the applicability of mechanical control devices and to facilitate the precise tuning. In the last part, active and semi-active vibration control techniques are developed. The first strategy consists in enhancing the control capability of passive TMD and IDVA by feeding back the displacement signal of mechanical system to the electromagnetic actuator. The proposed controller can be regarded as one or multiple basic units arranged in series, which is featured by one pole at the origin and two coalesced zeros on the real axis. Distinguished from the previous strategy, the semi-active control technique is based on electromagnetic shunt damping (EMSD), therefore, no additional sensor is required to measure the information of mechanical system. In order to artificially increase the shunt damping performance, the employment of negative inductance (NI) in the shunt circuit is considered. Three possible layouts of NI in the EMSD are assessed in terms of the electromechanical coupling factor, which quantifies the energy conversion efficiency between mechanical and electrical domains. Finally, six types of shunt circuits are optimally tuned according to the FPT and the beneficial effect of NI and the influence of its layout can be underlined
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Molander, Jonathan, and Loo Lennart van. "Active Versus Passive Investing : A Comparative Analysis." Thesis, Internationella Handelshögskolan, Jönköping University, IHH, Företagsekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-49153.
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The increasing popularity of passive investment strategies causes the long-term feasibility of active investing to be questioned more often. Therefore, this research aimed to uncover whether active investors' influence on fund performance is positive and significant enough to offset the cost involved, thereby providing reasoning for active rather than passive investing. A comparative analysis of 211 actively managed funds and 191 market and industry-specific indices is performed. Security selection skills and market timing ability are captured through a model comprising of the Fama French three-factor and the Treynor and Mazuy market timing model. The sample is tested between 2005 and 2020, with 5-year sub-periods. Over the full period, active and passive returns are found to be nearly indistinguishable. However, active funds seem to excel during bearish periods, where passive funds excel in bullish periods. The standard deviation is higher overall for passive investing. This difference, however, disappears during bearish periods. The security selection skill is barely distinguishable from zero for either strategy. On the other hand, market timing ability is existent for active investors, indicating a positive effect in bearish markets and a negative effect in bullish markets. Additionally, for both investing strategies, more than 90% of the returns are explained by the movements of the general market. The most suitable investment strategy is truly determined by an investor's level of risk aversion. Nevertheless, this research found that, in general, the passive investing strategy is dominant under normal market conditions. Active investors can act on the macroeconomic developments that fuel crises. This advantage enables them to achieve returns superior to indices while preserving a lower standard deviation during bearish market conditions.
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SAXBY, DYANI J. "ACTIVE AND PASSIVE FATIGUE IN SIMULATED DRIVING." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195507547.
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Watson, Rose E. (Rose Elliott). "Active or Passive Voice: Does It Matter?" Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc501082/.
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This thesis reports on the use of active and passive voice in the workplace and classroom through analysis of surveys completed by 37 employees and 66 students. The surveys offered six categories of business writing with ten sets of two sentences each, written in active and passive voice. Participants selected one sentence from each set and gave a reason for each selection. The participants preferred active over passive 47 to 46 percent of opportunities, but they preferred mixed voice over both, 49 percent. The participants preferred active only for memos to supervisors; in the other five categories they preferred passive or mixed voice. Both males and females preferred mixed voice, and age appeared to influence the choices. They cited context as the most common reason for using passive.
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Poon, Joyce Kai See Yariv Amnon. "Active and passive coupled-resonator optical waveguides /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05242007-105741.
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Moore, Garrett Lee. "A Hybrid (Active-Passive) VANET Clustering Technique." Diss., NSUWorks, 2019. https://nsuworks.nova.edu/gscis_etd/1077.
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Clustering serves a vital role in the operation of Vehicular Ad hoc Networks (VANETs) by continually grouping highly mobile vehicles into logical hierarchical structures. These moving clusters support Intelligent Transport Systems (ITS) applications and message routing by establishing a more stable global topology. Clustering increases scalability of the VANET by eliminating broadcast storms caused by packet flooding and facilitate multi-channel operation. Clustering techniques are partitioned in research into two categories: active and passive. Active techniques rely on periodic beacon messages from all vehicles containing location, velocity, and direction information. However, in areas of high vehicle density, congestion may occur on the long-range channel used for beacon messages limiting the scale of the VANET. Passive techniques use embedded information in the packet headers of existing traffic to perform clustering. In this method, vehicles not transmitting traffic may cause cluster heads to contain stale and malformed clusters. This dissertation presents a hybrid active/passive clustering technique, where the passive technique is used as a congestion control strategy for areas where congestion is detected in the network. In this case, cluster members halt their periodic beacon messages and utilize embedded position information in the header to update the cluster head of their position. This work demonstrated through simulation that the hybrid technique reduced/eliminated the delays caused by congestion in the modified Distributed Coordination Function (DCF) process, thus increasing the scalability of VANETs in urban environments. Packet loss and delays caused by the hidden terminal problem was limited to distant, non-clustered vehicles. This dissertation report presents a literature review, methodology, results, analysis, and conclusion.
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Dussopt, Laurent. "Technologies et concepts nouveaux d'antennes planaires pour systèmes de communication : structures passives et actives." Nice, 2000. http://www.theses.fr/2000NICE5425.
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Les technologies associées aux antennes imprimées, peu répandues dans les dispositifs grand public, peuvent apporter des solutions intéressantes aux spécifications de plus en plus strictes (coût, débit de transmission, dimensions) imposées aux divers systèmes de télécommunication actuels (téléphonie mobile, internet, télévision numérique, etc. ). La première partie de ce mémoire est consacrée à l'utilisation d'un nouveau matériau de faible permittivité et à faibles pertes, la mousse d'imide polyméthacrylate, pour la conception de réseaux d'antennes passives à polarisation circulaire pour les communications terrestres et satellitaires. (. . . ). Dans la deuxième partie du mémoire, de nouveaux concepts sont présentés dans le domaine des antennes actives à base d'antennes oscillantes. Tout d'abord, une antenne mélangeuse auto-oscillante utilisant une antenne à cavité a été conçue et mesurée. L'oscillateur fonctionnant à une fréquence de résonance de la cavité, les niveaux de bruit de phase et de rayonnement parasite de l'oscillateur sont faibles. La modulation de phase à 2 et 4 états d'une antenne oscillante est ensuite mise en oeuvre et a permis des débits supérieurs à 1 Mbit/s. Enfin, une nouvelle méthode de mise en réseau d'antennes oscillantes permettant, grâce à une configuration séquentielle, d'obtenir un réseau générant une polarisation circulaire de bonne qualité et de façon très fiable, est étudiée théoriquement et validée expérimentalement. (. . . )
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Liu, Yanzhen. "Active supply harmonic filtering." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266446.
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Emonin, Stéphanie. "Analyse de circuits optiques passifs et actifs en microscopie a sonde locale." Dijon, 1998. http://www.theses.fr/1998DIJOS038.
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Le principal objectif de cette étude est de montrer que les microscopes à sonde locale sont tout-à-fait adaptés à la caractérisation de circuits optiques passifs et actifs de l'optique intégrée, que ce soit par une utilisation individuelle des microscopes AFM (atomic force microscope) et PSTM (photon scanning tunneling microscope) ou par le couplage de deux techniques AFM/LFM (lateral force microscope) et AFM/PSTM. Dans un premier chapitre, nous déterminons les longueurs d'onde de coupure de guides d'ondes planaires à gradient d'indice grâce a un PSTM. A l'aide d'une méthode numérique adaptée, on parvient à remonter aux caractéristiques opto-géométriques du guide et à comparer nos résultats avec ceux généralement obtenus par des méthodes plus classiques. Dans un deuxième chapitre, nous proposons quatre techniques utilisant des microscopes a sonde locale afin de pouvoir localiser les dopants de fibres optiques dopées erbium clivées. Des mesures de friction, de détection de phase, d'analyse modale et de fluorescence sont réalisées et montrent l'influence de la sonde locale utilisée (leviers AFM, fibre courbée, importance de la métallisation). Dans un troisième chapitre, nous étudions deux types de diodes laser a semi-conducteurs émettant dans le proche infra-rouge. Une étude comparative est réalisée avec les dispositifs AFM/LFM et AFM/PSTM qui permettent tous deux de détecter les modes transverses des diodes. Dans le cas de l'AFM/LFM, seuls les effets thermiques qui entrent en jeu fournissent une explication des images topographiques et de friction obtenues et mettent ainsi en évidence la sensibilité à la température d'un levier AFM classique.
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Han, Yehui Ph D. Massachusetts Institute of Technology. "Circuits and passive components for radio-frequency power conversion." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57983.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 141-149).
This thesis focuses on developing technology for high efficiency power converters operating at very high frequencies. The work in the thesis involves two aspects of such converters: rf (radio-frequency) power circuit design techniques and magnetic material characterization and application. In the aspect of circuit design techniques, the thesis investigates a new class of matching networks that overcomes a major limitation of rf converter circuits - their high sensitivity to loading condition. These networks, which are termed resistance compression networks, serve to substantially decrease the variation in effective resistance seen by a tuned rf inverter as loading conditions change. The thesis explores the operation, performance characteristics, and design of these networks, and present experimental results demonstrating their performance. The thesis also presents analysis and design considerations for lumped (inductor and capacitor) matching networks operating at high efficiency (> 95%). Formulas for calculating matching network efficiency are given and used to evaluate the optimum number of matching stages as a function of conversion ratio. Both simulation and experimental results are presented that validate the analytical formulation. In the aspect of magnetic materials and applications, the thesis investigates the loss characteristics of several commercial rf magnetic materials for power conversion applications in the 10 MHz to 100 MHz range.
(cont.) A measurement method is proposed to identify loss characteristics of different commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. Based on results in characterization of magnetic materials, the thesis describes a procedure for magnetic components design with low permeability magnetic materials that is for very high frequency power conversion applications. This procedure provides a method to compare and evaluate different magnetic materials for given specifications of a magnetic-core inductor. Some important information, e.g. quality factor and size of the inductor can be predicted before the final design. The thesis also investigates some problems such as optimization of a magnetic-core inductor.
by Yehui Han.
Ph.D.
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Svanberg, Mikaela, and Emilia Karlsson. "Active or Passive Fund Management : A comparison between active and passive Swedish funds before, during and after the financial crisis." Thesis, Linnéuniversitetet, Institutionen för ekonomistyrning och logistik (ELO), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-75394.
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The essay investigates if there is a correlation between a funds management fee and return in relation to the risk that is taken by the investor. Furthermore, the essay examines if it is worth paying a higher fee for an actively managed fund compared to the lower fee for a passively managed fund. In addition, the essay will investigate whether the results differ before, during and after the financial crisis which took place between 2007 and 2009. To answer the questions 38 different Swedish equity funds, 33 active and five passive, are used. The funds are investigated using performance measures, correlation analysis and regression analysis. The results show that there is no clear correlation between funds management fee and return in relation to the risk that is taken. In addition, the essay conclude that it is not worth paying a higher management fee for an actively managed fund.
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Huo, Xiao. "High performance passive components modeling and integration in RF/microwave systems /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20HUO.
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Kazemi, Alireza. "Mutual Fund Performance : Active- and Passive Fund Management." Thesis, Jönköping University, JIBS, Economics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1226.
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In this thesis I will examine active equity mutual fund managers’ ability to outperform an index, which is done by utilizing a sample of four equity mutual funds that mainly invest in large Swedish quoted companies. In order to measure the risk-adjusted performance of the funds, a model created by Michael Jensen will be used. Furthermore, I will investigate whether the managers of the mutual funds increase/decrease the risk level, or rather the beta, when the stock market is bullish/bearish. Hence, two time spans have been chosen, 2001-2003 and 2004-2006, where the previous represents a bearish stock market and the later represents a bullish stock market.
The empirical evidence indicates that one fund in each period was significantly outper-formed by the comparable index. Furthermore, the result also suggests that two significant funds were talking more risk than the index in the bearish time period while three signifi-cant funds decreased the risk level during the bullish time period.
Denna kandidatuppsats undersöker aktiva fondförvaltares förmåga att upptäcka och inve-stera i fonder som presterar bättre än deras jämförekse index. Undersökningen är baserad på fyra aktiefonder som huvudsakligen investerats i Svenska börsnoterade företag. Fonder-nas riskjusterade prestation kommer att mätas med hjälp av en modell som är utformad av Michael Jensen.
Vidare kommer uppsatsen att undersöka om fondförvaltarna ökar eller minskar risk nivån, eller betavärdet, baserat på börsens utveckling under åren 2001-2003 och 2004-2006. Det förgående intervallet representerar en sjunkande börsperiod och det senare en stigande börsperiod.
Det empiriska resultatet indikerar att en signifikant fond i varje tidsintervall presterade säm-re än index. Utöver detta visade även resultatet att två signifikanta fonder ökade risk nivån, jämfört med index, i den sjunkande börsperioden medan tre signifikanta fonder minskade risk nivån i den stigande börsperioden.
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Karam, Philippe Chucri. "Modeling passive and active mechanisms in motoneuron dendrites." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13713.
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Sherwani, Hashir. "Resource management in active-passive multifunction radar networks." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10056926/.
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Despite the extensive research within the field of resource management in monostatic multifunction radar, the resource management techniques for a multifunction radar network are still in their infancy. More specifically, a network which has the ability to switch modes between monostatic and bistatic configuration may potentially be able to capitalise on the advantages of both configurations. This is a gap which has been identified and is the aim of this thesis to explore. The research within this thesis begins by exploring the advantages provided by a bistatic configuration over a monostatic configuration. The conclusions from the initial research are carried forward to design a complete resource management framework for a multifunction radar network consisting of active and passive nodes. The resource management framework is broken into two sub-problems, resourceallocation and the scheduling problem. The resource-allocation problem deals with the task parameter selection methodology to optimally distribute the finite resources. This incorporates the concept of information sharing, which can be considered as a subset of information fusion theory, to delegate a given task to the best suited sensor within the network. A Quality of service framework is utilised to solve the resource-allocation problem where the resulting algorithm is referred to as APNQ-RAM. The scheduling problem is solved by deploying an earliest deadline first scheduler on master-slave architecture where the resulting algorithm is named as MS-EDFS. The research has also explored the impact of the networks geometry and the number of nodes on the network’s performance in tracking and surveillance functions. The research shows significant advantages in terms of tracking and surveillance performance provided by such a network in comparison to a monostatic configuration functioning on its own.
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Sousa, Júnior Gabriel Faria de. "Active versus passive management : the case of BOVESPA." Master's thesis, Instituto Superior de Economia e Gestão, 2016. http://hdl.handle.net/10400.5/11647.
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Mestrado em FinançasO principal objetivo deste trabalho é analisar alguns modelos subjacente à gestão de carteiras ativa e passiva e qual seria seu impacto sobre a escolha de uma determinada carteira constituída por ações que estão integrados no índice BOVESPA, maior mercado bolsista do Brasil. A gestão passiva é baseada numa carteira que visa replicar o comportamento do Índice BOVESPA, tendo como base os preços históricos do índice e no método naïve (1/N), no qual composição da carteira inclui todos os ativos do índice com as mesmas proporções. A gestão ativa baseia-se no método de Markowitz, conhecido como modelo de média variância, que visa maximizar o retorno tendo definido um determinado nível de risco, ou minimizar o risco tendo em conta um nível de retorno esperado. Também é usado o método da variância mínima que consiste em minimizar o risco independentemente do retorno. Nesta abordagem as proporções a investir em cada ativo são revistas mensalmente tendo em conta a evolução do mercado. Outro modelo utilizado será um método ajustado da média variância em que serão mantidos os pesos ótimos do primeiro período para as restantes janelas de dados. Para as determinar são consideradas "janelas" de dados de 1 e 2 anos. É considerado um horizonte de investimento de 10 anos, a partir de Janeiro de 2005 a Dezembro de 2014. Com base nos resultados é possível afirmar que a carteira de média variância deve ser a escolhida, uma vez que apresenta os melhores resultados.
The main purpose of this paper is to analyze some models underlying the active and passive portfolio management and what would be its impact on the choice of a portfolio composed by stocks which are integrated in BOVESPA Index, Brazilian biggest stock market. The passive management approach is based on the historical prices of BOVESPA Index which replicates the behavior of the market and on the naïve method (1/N), in which the portfolio includes all the stocks on the index with the same proportions. Active management is based on the Markowitz model, also known as mean variance model, whose objective is to maximize the return give a set risk level or, minimize the risk given an expected return. The minimum variance model is also used, whose goal is to minimize the risk independent of the return. On these approach the weights of each asset in the portfolio are revised monthly, based on the market evolution. Another model used is a Mean Variance adjusted method in which the first period optimal weights will be maintained for the remaining data windows. In order for these to be determined, "windows" of 1 and 2 years were used. We are considering a 10 year investment horizon, from January 2005 to December 2014. Based on the results, we can affirm that the mean variance portfolio should be chosen, as performed better both in terms of returns and, especially, in terms of Sharpe ratio when compared with the other two portfolios.
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Zhang, Zhaowei. "Passive and active Bragg gratings for optical networks." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/47760/.
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This thesis investigates fibre Bragg grating (FBG) devices. Specifically, it consists of the developments and applications of two groups of devices: the optical phase en/decoders and the tunable fibre Bragg gratings based on an S-bending technique. The advantage of an S-bending tuning FBG is that its central wavelength is invariant as the linear strain gradient along the FBG is altered. Two new devices are developed by embedding a pair of FBGs in a single uniform beam for S-bending. One is the tunable dispersion compensator with a wide tuning range, and the other is a tunable pure dispersion slope compensator. The application of an S-bending tuning FBG in controlling the output pulse width of a soliton fibre laser is also experimentally demonstrated.
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Goldstein, Andre L. "Control of Sound Transmission with Active-Passive Tiles." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27913.
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Nowadays, numerous applications of active sound transmission control require lightweight partitions with high transmission loss over a broad frequency range and simple control strategies. In this work an active-passive sound transmission control approach is investigated that potentially addresses these requirements. The approach involves the use of lightweight stiff panels, or tiles, attached to a radiating base structure through active-passive soft mounts and covering the structure surface. The resulting double-partition configuration was shown to have good high frequency passive isolation, but poor low frequency transmission loss due to the coupling of the tiles to the base vibration through the air gap. The low frequency transmission loss performance of the partition was increased by using the active mounts to cancel the local volume velocity of the tiles. The use of a decentralized control approach with independent single channel controllers for each tile facilitates the implementation of a multiple tile system in a large scale application.
A coupled structural-acoustic model based on an impedance mobility matrix approach was formulated to investigate the potential performance of active-passive tile approach in controlling sound transmission through plates. The model was initially applied to investigate the sound transmission characteristics of a double-panel partition consisting of a single tile-plate configuration and then extended to model a partition consisting of multiple-tiles mounted on a plate. The system was shown to have significant passive performance above the mass-spring-mass resonance of the double-panel system. Both feedback and feedforward control approaches were simulated and shown to significantly increase the transmission loss of the partition by applying control forces in parallel with the mounts to reduce the tile normal velocity. A correspondent reduction in sound radiated power was obtained over a broad frequency range limited by the tile stiffness.
The experimental implementation of the active-passive tile approach for the control of sound transmission through plates was also performed. Two main experimental setups were utilized in the investigations, the first consisting of a single tile mounted on a clamped plate and the other consisting of four active tiles mounted of a simply supported plate. Tile prototypes were implemented with lightweight stiff panels and integrated active-passive mounts were implemented with piezoelectric Thunder actuators. Both analog feedback and digital feedforward control schemes where designed and implemented with the objective of reducing the normal velocity of the tiles. Experimental results have demonstrated significant broad frequency range reductions in the sound transmission through the partition by active attenuation of the tile velocity. In addition, the experiments have shown that decentralized control can be successfully implemented for multiple tiles systems. The active-passive sound transmission control characteristics of the systems experimentally studied were observed to be in accordance with the analytical results.Ph. D.
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Lam, Margaretha Johanna. "Hybrid Active/Passive Models with Frequency Dependent Damping." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30770.
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To add damping to structures, viscoelastic materials (VEM)
are added to structures. In order to enhance the damping
effect of the VEM, a constraining layer is attached,
creating a passive constrained layer damping treatment
(PCLD). When this constraining layer is an active element,
the treatment is called active constrained layer damping
(ACLD). Recently, the investigation of ACLD treatments has
shown it to be an effective method of vibration suppression.
In this work, two new hybrid configurations are introduced
by separating the passive and active elements. In the first
variation, the active and passive element are constrained
to the same side of the beam. The other variation allows
one of the treatments to be placed on the opposite side of
the beam. A comparison will be made with pure active, PCLD,
ACLD and a variation which places the active element
underneath PCLD. Energy methods and Lagrange's equation
are used to obtain equations of motion, which are
discretized using assumed modes method. The frequency
dependent damping is modeled using the Golla-Hughes-McTavish
(GHM) method and the system is analyzed in the time domain.
GHM increases the size of the original system by adding
fictitious dissipation coordinates that account for the
frequency dependent damping. An internally balanced model
reduction method is used to reduce the equations of motion
to their original size. A linear quadratic regulator and
output feedback are used to actively control vibration. The
length and placement of treatment is optimized using
different criteria. It is shown that placing the active
element on the opposite side of the passive element is
capable of vibration suppression with lower control effort
and more inherent damping. If the opposite surface is not
available for treatment, a suitable alternative places the
PZT underneath the PCLD. LQR provides the best control,
since it assumes all states are available for feedback.
Usually only select states are available and output
feedback is used. It is shown that output feedback, while
not as effective as full state feedback, is still able to
damp vibration.Ph. D.
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Ziolkowski, Richard W. "Passive and active metamaterial-inspired nano-scale antennas." IEEE, 2016. http://hdl.handle.net/10150/623141.
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A variety of open and closed multi-layered nanoparticle structures have been considered analytically and numerically for their use as scatterers and radiators. These include metamaterial-inspired structures based on dielectrics and metals excited by either plane waves or electric Hertzian dipoles at optical frequencies. Both passive and active (gain impregnated dielectric) materials have been considered. Enhanced and mitigated scattering and radiating effects have been modeled. Nano-antenna and nano-amplifier configurations for optical applications have been emphasized. A review of these modeling efforts will be presented.
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Huang, Caijin. "Optical nano-antennas : passive properties and active control." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS011/document.
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Les nano-antennes optiques sont de nouveaux éléments, généralement métalliques, permettant d’améliorer les interactions électromagnétiques entre le rayonnement lumineux et un objet sub-longueur d’onde. Ces dispositifs innovants, fonctionnant dans une gamme de longueur d’onde correspondant au spectre visible et proche infrarouge, répondent à certaines contraintes inhérentes à l’optique lorsque les échelles d’interactions relèvent du nanomètre. En particulier, les propriétés des antennes optiques métalliques sont régies par l’apparition de résonances plasmons qui permettent, d’une part de confiner le champ électromagnétique dans des volumes très inférieurs aux limites imposées par la diffraction, et d’autre part d’exalter fortement les processus optiques à faibles sections efficaces. L’objectif de cette thèse est de comprendre par l’expérience quels sont les paramètres clés qui caractérisent une nano-antenne optique afin d’en contrôler son fonctionnement. Ces paramètres ont été accessibles expérimentalement grâce au développement d’une microscopie adaptée basée sur une illumination diascopique à faible ouverture numérique avec soit une détection coronographique confocale ou conoscopique. Cet appareillage nous a permis de mesurer la capacité d’une antenne optique unique à diffuser un rayonnement lumineux. Les études ont débutées avec des systèmes modèles simples (nanoparticules) pour évoluer vers des antennes couplées (dimères). Par analogie avec le domaine radiofréquences, les paramètres importants d’une antenne optique que sont la plage fréquentielle, le désaccord, le gain et le diagramme de rayonnement ont été définis et mesurés. L’influence des caractéristiques morphologiques de l’antenne sur ces paramètres a complété l’étude. Toujours par comparaison avec les antennes radiofréquences, nous avons introduit le concept de tuner optique. Le principe est de modifier la réponse optique de la charge de l’antenne, c’est-à-dire le milieu dans lequel elle émet son rayonnement. Dans ce but, nous avons utilisé un milieu anisotrope composé des molécules de cristal liquide dont l’orientation de l’ellipsoïde des indices peut être commandée par un champ électrostatique. Le fonctionnement du tuner, c’est-à-dire l’accord de l’antenne à une fréquence de travail, a été démontré pour des antennes optiques coupléesOptical nanoantennas are a new class of optical devices, generally constituted of metal nanoparticles, used for enhancing the interaction between an electromagnetic wave and a nano-scale object. These components are operating in the visible to near infra-red part of the spectrum and are offering solutions for the inherent limitations of optics at the nanometer scale. In particular, the properties of optical antennas are governed by the surface plasmon resonances of the underlying structure. These resonances are associated with a large field confinement, beyond the diffraction limit, and an enhancement of the local electromagnetic response that is used to amplify weak optical processes. The objective of this doctoral thesis is to understand by an experimental approach what are the key parameters characterizing an optical antenna with the aim to control its operation. Through the development of an original microscopy based on a low numerical aperture diascopic illumination and a subsequent spatial filtering, the scattering characteristics of a single optical nano-antenna were successfully measured. Our approach was first tested with simple model antennas (nanoparticles) before investigating multi-element coupled antennas (dimers). In analogy to radiofrequency theory, we have defined and measured important antenna characteristics: operating frequency, detuning factor, gain and emission diagram. We have studied the influence of the morphology of the antenna on these characteristics. Continuing the comparison with microwave antennas, we have introduced the concept of an optical tuner. The operating principle is to modify the medium in which the antenna is emitting its radiation i.e. the load of the device. To this aim, we have employed anisotropic liquid crystal molecules. With this load medium, the orientation of the anisotropy can be controlled by a static electric field. The operation of the optical tuner, i.e. tuning of the antenna to a broadcasting frequency, is demonstrated for electromagnetically coupled antennas
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Meade, S. A. "The rapid and rigorous mathematical modelling of passive planar microwave circuits." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238860.
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Balik, Hasan Huseyin. "Passive open planar microwave circuit analysis by enhanced spectral domain method." Thesis, University of Bristol, 1997. http://hdl.handle.net/1983/3b619722-649b-483b-a806-6a3494f942ce.
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