Дисертації з теми "Frequency transfer"
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1
Butler, Brandon. "Reliable data transfer via frequency transmission." Thesis, Butler, Brandon (2017) Reliable data transfer via frequency transmission. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40398/.
Повний текст джерелаАнотація:
Reliable single directional frequency data transfer is a method of electronic communication that is a potential alternative to a bi-directional or wired method. It is intended to determine whether or not single directional data transfer can be designed to perform at the same reliability level as other methods of data transmission. The reason for researching this is to see whether, two-way communication is necessary. Upon finding results to this question it will be determined if single directional frequency data transfer can be as power efficient as bi directional data transfer. It will also look into the overall performance of the method and how it can deal with inhibiting factors that will be introduced to simulate real world external variations in the signal.
How reliable single directional frequency transfer is, will be determined through experiments that are tasked at finding the maximum transmission rate of the devices made and the distance that data transmission can be conducted over.
The investigation will require the design of an experimental apparatus that will allow results to be found in the maximum possible transmission rate and distance transmission can cover.
The experimental apparatus will consist of two possessors, one for encoding a message, the other for decoding a message. The apparatus will also require an integrated radio frequency transmitter circuit as well as a receiver radio frequency integrated circuit. The processors will need to be coded with a new protocol that will allow the incorporation of three forward error correction techniques. This is so that a basic, intermediate and advanced method of forward error correction can be compared when gathering results.
Throughout this research consideration into all aspects that can possibly improve the energy efficiency of the electrical apparatus will be addressed an implemented. By creating an experimental apparatus that is competitive against other data transmission methods in terms of energy efficiency. With an energy efficient experimental apparatus, then results found could be a close representation of the likely outcomes if single directional data transmission was to be implemented on a larger scale.
2
Ilvedson, Corinne Rachel 1974. "Transfer function estimation using time-frequency analysis." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50472.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (p. 135-136).
Given limited and noisy data, identifying the transfer function of a complex aerospace system may prove difficult. In order to obtain a clean transfer function estimate despite noisy data, a time-frequency analysis approach to system identification has been developed. The method is based on the observation that for a linear system, an input at a given frequency should result in a response at the same frequency, and a time localized frequency input should result in a response that is nearby in time to the input. Using these principles, the noise in the response can be separated from the physical dynamics. In addition, the impulse response of the system can be restricted to be causal and of limited duration, thereby reducing the number of degrees of freedom in the estimation problem. The estimation method consists of finding a rough estimate of the impulse response from the sampled input and output data. The impulse response estimate is then transformed to a two dimensional time-frequency mapping. The mapping provides a clear graphical method for distinguishing the noise from the system dynamics. The information believed to correspond to noise is discarded and a cleaner estimate of the impulse response is obtained from the remaining information. The new impulse response estimate is then used to obtain the transfer function estimate. The results indicate that the time-frequency transfer function estimation method can provide estimates that are often less noisy than those obtained from other methods such as the Empirical Transfer Function Estimate and Welch's Averaged Periodogram Method.
by Corinne Rachel Ilvedson.
S.M.
3
Lawson, James. "High frequency electromagnetic links for wireless power transfer." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/54841.
Повний текст джерелаАнотація:
This thesis investigates inductive links used in wireless power transfer systems. Inductive power transfer can be used as a power delivery method for a variety of portable devices, from medical implants to electric vehicles and is gaining increased interest. The focus is on high quality factor coils and MHz operation, where accurate measurements are difficult to achieve. Fast models of all pertinent aspects of inductive power transfer systems for constant cross section coils are developed. These models are used to optimise a new coil winding pattern that aims to increase efficiency in volume constrained scenarios. Measurement systems are developed to measure coil Q factors in excess of 1,000. The prototype measurement systems are verified against models of that system, as well as finite element simulations of the coil under test. Shielding of inductive power transfer systems is then investigated. A structure typically used at GHz frequencies, the artificial magnetic conductor, is miniaturised as an alternative to conventional ferrite backed ground plane shielding. Finite element simulation shows this structure significantly improves link efficiency. The artificial magnetic conductor prototype does not result in a gain in efficiency expected, however it does display the properties expected of an artificial magnetic conductor, including increased coupling factor. Finally, an unconventional inductive power transfer system is presented where transmitter and receiver are up to 6m away from each other and of radically different size. This system provides mW level power to remote devices in a room, for example thermostats or e-ink displays. Conventional approaches to design do not consider the distortion of the magnetic field caused by metallic objects in the room. It was found that treating the system as a decoupled receiver and transmitter provides a better prediction of received power in real world environments.
4
Foreman, Seth M. "Femtosecond frequency combs for optical clocks and timing transfer." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273700.
Повний текст джерела
5
Zhao, Rui. "Double resonant high-frequency converters for wireless power transfer." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22958/.
Повний текст джерелаАнотація:
This thesis describes novel techniques and developments in the design and implementation of a low power radio frequency (40kHz to 1MHz) wireless power transfer (WPT) system, with an application in the wireless charging of autonomous drones without physical connection to its on-board Battery Management System (BMS). The WPT system is developed around a matrix converter exploiting the benefits such as a small footprint (DC-link free), high efficiency and high power density. The overall WPT system topology discussed in this thesis is based on the current state-of-the-art found in literature, but enhancements are made through novel methods to further improve the converter's stability, reduce control complexity and improve the wireless power efficiency. In this work, each part of the system is analysed and novel techniques are proposed to achieve improvements. The WPT system design methodology presented in this thesis commences with the use of a conventional full-bridge converter. For cost-efficiency and to improve the converters stability, a novel gate drive circuit is presented which provides self-generated negative bias such that a bipolar MOSFET drive can be driven without an additional voltage source or magnetic component. The switching control sequences for both a full-bridge and single phase to single phase matrix converter are analysed which show that the switching of a matrix converter can be considered to be the same as a full-bridge converter under certain conditions. A middleware is then presented that reduces the complexity of the control required for a matrix converter and enables control by a conventional full-bridge controller (i.e. linear controller or microcontroller). A novel technique that can maximise and maintain in real-time the WPT efficiency is presented using a maximum efficiency point tracking approach. A detailed study of potential issues that may affect the implementation of this novel approach are presented and new solutions are proposed. A novel wireless pseudo-synchronous sampling method is presented and implemented on a prototype system to realise the maximum efficiency point tracking approach. Finally, a new hybrid wireless phase-locked loop is presented and implemented to minimise the bandwidth requirements of the maximum efficiency point tracking approach. The performance and methods for implementation of the novel concepts introduced in this thesis are demonstrated through a number of prototypes that were built. These include a matrix converter and two full WPT systems with operating frequencies ranging from sub-megahertz to megahertz level. Moreover, the final prototype is applied to the charging of a quadcopter battery pack to successfully charge the pack wirelessly whilst actively balancing the cells. Hence, fast battery charging and cell balancing, which conventionally requires battery removal, can be achieved without re-balance the weight of the UAV.
6
Marra, Giuseppe. "Transfer of optical frequency combs over optical fibre links." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/350220/.
Повний текст джерелаАнотація:
In just over a decade the optical frequency comb technique has completely transformed the field of frequency metrology. These devices have made the measurement of the frequency of light a much easier and affordable task when compared to with earlier techniques. With both research and technology development on these devices becoming more mature, optical frequency combs have been affecting other science areas. Applications are already found in spectroscopy, attosecond physics and astrophysics and more science and engineering areas can be expected to be affected in the near future. The dissemination over optical fibre of optical frequency combs between research labs, or between research labs and industry, could facilitate and accelerate this process. In particular, with optical frequency standards currently exhibiting a fractional accuracy better than 10^-17 and optical frequency combs making this accuracy available across a wide spectrum, new experiments could be devised in a wide range of research fields if ultra accurate microwave and optical frequencies were to be made available beyond the walls of metrology laboratories. However, before the work presented in this thesis, limited research was undertaken to test how accurately an optical frequency comb could be transferred over optical fibre. Environmentally-induced noise in the fibre, dispersion issues and other processes taking place during the propagation and detection of the optical signal could all degrade its quality to a level incompatible with the desired applications. The experiments described here demonstrate that optical frequency combs can be disseminated over optical links, from several-km to many tens of km-long, whilst preserving the stability and accuracy of its mode frequency spacing and mode frequency to a level compatible with the majority of the most demanding frequency metrology applications.
7
Boaventura, Alírio de Jesus Soares. "Efficient wireless power transfer and radio frequency identification systems." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17374.
Повний текст джерелаАнотація:
Doutoramento em Engenharia EletrotécnicaIn the IoT context, where billions of connected objects are expected to be ubiquitously deployed worldwide, the frequent battery maintenance of ubiquitous wireless nodes is undesirable or even impossible. In these scenarios, passive-backscatter radios will certainly play a crucial role due to their low cost, low complexity and battery-free operation. However, as passive-backscatter devices are chiefly limited by the WPT link, its efficiency optimization has been a major research concern over the years, gaining even more emphasis in the IoT context. Wireless power transfer has traditionally been carried out using CW signals, and the efficiency improvement has commonly been achieved through circuit design optimization. This thesis explores a fundamentally different approach, in which the optimization is focused on the powering waveforms, rather than the circuits. It is demonstrated through theoretical analysis, simulations and measurements that, given their greater ability to overcome the built-in voltage of rectifying devices, high PAPR multi-sine (MS) signals are capable of more efficiently exciting energy harvesting circuits when compared to CWs. By using optimal MS signals to excite rectifying devices, remarkable RF-DC conversion efficiency gains of up to 15 dB with respect to CW signals were obtained. In order to show the effectiveness of this approach to improve the communication range of passive-backscatter systems, a MS front-end was integrated in a commercial RFID reader and a significant range extension of 25% was observed. Furthermore, a software-defined radio RFID reader, compliant with ISO18000-6C standard and with MS capability, was constructed from scratch. By interrogating passive RFID transponders with MS waveforms, a transponder sensitivity improvement higher than 3 dB was obtained for optimal MS signals. Since the amplification and transmission of high PAPR signals is critical, this work also proposes efficient MS transmitting architectures based on space power combining techniques. This thesis also addresses other not less important issues, namely self-jamming in passive RFID readers, which is the second limiting factor of passive-backscatter systems. A suitable self-jamming suppression scheme was first used for CW signals and then extended to MS signals, yielding a CW isolation up to 50 dB and a MS isolation up 60 dB. Finally, a battery-less remote control system was developed and integrated in a commercial TV device with the purpose of demonstrating a practical application of wireless power transfer and passive-backscatter concepts. This allowed battery-free control of four basic functionalities of the TV (CH+,CH-,VOL+,VOL-).
No contexto da internet das coisas (IoT), onde são esperados bilhões de objetos conectados espalhados pelo planeta de forma ubíqua, torna-se impraticável uma frequente manutenção e troca de baterias dos dispositivos sem fios ubíquos. Nestes cenários, os sistemas radio backscatter passivos terão um papel preponderante dado o seu baixo custo, baixa complexidade e não necessidade de baterias nos nós móveis. Uma vez que a transmissão de energia sem fios é o principal aspeto limitativo nestes sistemas, a sua otimização tem sido um tema central de investigação, ganhando ainda mais ênfase no contexto IoT. Tradicionalmente, a transferência de energia sem-fios é feita através de sinais CW e a maximização da eficiência é conseguida através da otimização dos circuitos recetores. Neste trabalho explora-se uma abordagem fundamentalmente diferente, em que a otimização foca-se nas formas de onda em vez dos circuitos. Demonstra-se, teoricamente e através de simulações e medidas que, devido à sua maior capacidade em superar a barreira de potencial intrínseca dos dispositivos retificadores, os sinais multi-seno (MS) de elevado PAPR são capazes de excitar os circuitos de colheita de energia de forma mais eficiente quando comparados com o sinal CW tradicional. Usando sinais MS ótimos em circuitos retificadores, foram verificadas experimentalmente melhorias de eficiência de conversão RF-DC notáveis de até 15 dB relativamente ao sinal CW. A fim de mostrar a eficácia desta abordagem na melhoria da distância de comunicação de sistemas backscatter passivos, integrou-se um front-end MS num leitor RFID comercial e observou-se um aumento significativo de 25% na distância de leitura. Além disso, desenvolveu-se de raiz um leitor RFID baseado em software rádio, compatível com o protocolo ISO18000-6C e capaz de gerar sinais MS, com os quais interrogou-se transponders passivos, obtendo-se ganhos de sensibilidade dos transponders maiores que 3 dB. Uma vez que a amplificação de sinais de elevado PAPR é uma operação crítica, propôs-se também novas arquiteturas eficientes de transmissão baseadas na combinação de sinais em espaço livre. Esta tese aborda também outros aspetos não menos importantes, como o self-jamming em leitores RFID passivos, tido como o segundo fator limitativo neste tipo de sistemas. Estudou-se técnicas de cancelamento de self-jamming CW e estendeu-se o conceito a sinais MS, tendo-se obtido isolamentos entre o transmissor e o recetor de até 50 dB no primeiro caso e de até 60 dB no segundo. Finalmente, com o objetivo de demonstrar uma aplicação prática dos conceitos de transmissão de energia sem fios e comunicação backscatter, desenvolveu-se um sistema de controlo remoto sem pilhas, cujo protótipo foi integrado num televisor comercial a fim de controlar quatro funcionalidades básicas (CH+,CH-,VOL+,VOL-).
8
Hopper, David J. "Investigation of laser frequency stabilisation using modulation transfer spectroscopy." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16667/1/David_John_Hopper_Thesis.pdf.
Повний текст джерелаАнотація:
Optical frequency standards are necessary tools for accurate measurement of time and length. In practice these standards are stabilised laser systems locked to a known frequency reference. These references are typically the resonant frequencies of the atoms of an absorption medium that have been theoretically calculated to a high degree of accuracy. This thesis describes a combination of experimental and theoretical research performed on modulation transfer spectroscopy (MTS)--a technique used to frequency stabilise a laser in order to produce an accurate frequency reference--with emphasis placed on developing techniques and procedures to overcome the limitations found in existing MTS stabilised laser systems. The focus of the thesis is to generate a highly accurate frequency reference by researching the system parameters that will increase the signal to noise ratio and improve the accuracy of the reference through refinement of the signal structure.
The early theoretical interpretation of MTS was effectively a low absorption approximation that occurs at low pressures. This approximation ignores the depletion of beam energy through absorption and is a distinct limitation of the theoretical model in its ability to accurately predict the influence of a range of system parameters on signal strength and structure. To overcome this limitation a 3-D (or volumetric) analysis was developed and is presented here for the first time. This volumetric model is a measure of two depleted beams interacting collinearly in an absorbing medium of iodine and is described to accurately predict the signal maximum as a function of pressure for all wavelengths. This model was found to be more accurate in predicting the influence of system parameters on the signal strength and structure, including that of pump beam intensity, pressure, saturation parameter, cell length and modulation parameters.
The volumetric model is a novel approach to MTS theory but is more complex computationally than the traditional low pressure model and therefore more difficult to implement in many situations. To overcome this problem a hybrid model was developed as a combination of the low pressure and volumetric models.
The comparison between the rigorous volume model and the hybrid model indicate that there is a deviation in the signal strength at high pressures. However, the agreement was very good in the pressure regimes that are commonly used to realise actual frequency references. Comparison of the hybrid model to experimental data was performed over a range of different wavelengths (532 nm, 543.5 nm, 612 nm and 633 nm) and found to be in close agreement. This gives confidence in the model to accurately predict signal strength and structure in any situation.
Three mechanisms have been identified that limit the accuracy of frequency references due to the creation of residual amplitude modulation (RAM) where it shifts the frequency of the reference. The influence of RAM is included in the hybrid model as a ratio of the amplitude modulated and frequency modulated components of the saturating beam. These RAM production mechanisms result from the modulation of the saturating beam, the overlap of the beams in the medium, and the differential absorption of the sidebands in the medium. While the first mechanism has been previously reported the latter two are discussed here in detail for the first time. RAM generated by the modulators used (acousto-optic or electro-optic modulators) was typically of the order of 10% to 12%, depending on the excursion of the created sidebands. RAM generated by an asymmetric beam overlap with the modulators used was found to be as large as 30%. A combination of these two independent mechanisms can be used to provide a "RAM-free" state of the system by using one to cancel the effects of the other. The third RAM generation process--medium induced RAM--is difficult to remove but through a careful combination of absorption related parameters--namely, pump intensity, cell length, pressure and detector phase--the effects of RAM can be removed, leading to a distortion free MTS signal.
Further investigation into the predictions provided by the hybrid model shows that there is a complex relationship between cell length and the optimum pressure required for maximum signal strength, such that longer cell lengths will not necessarily improve the signal strength. This is contrary to conventional thinking and is important in the MTS design process to reduce unnecessary costs and improve the signal to noise ratio and frequency accuracy. Optimisation of frequency stabilised laser systems using MTS are generally performed using trial and error. Comparison of these optimum parameter values to those predicted by the hybrid model show that for popular wavelengths such as 532 nm they are similar.
In addition, the hybrid model is able to predict the frequency shifts that arise within the system parameters used and has shown that existing systems being used at 532 nm, 633 nm and 778 nm could improve their signal to noise ratio and accuracy through a variation in the parameters. A methodology based on the hybrid model is presented that can be used to calculate the optimum parameters for maximum signal strength and a "RAM-free" state for any wavelength. This systematic approach can therefore be used to guide the design of actual frequency stabilised laser systems prior to and during the design process.
9
Hopper, David J. "Investigation of laser frequency stabilisation using modulation transfer spectroscopy." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16667/.
Повний текст джерелаАнотація:
Optical frequency standards are necessary tools for accurate measurement of time and length. In practice these standards are stabilised laser systems locked to a known frequency reference. These references are typically the resonant frequencies of the atoms of an absorption medium that have been theoretically calculated to a high degree of accuracy. This thesis describes a combination of experimental and theoretical research performed on modulation transfer spectroscopy (MTS)--a technique used to frequency stabilise a laser in order to produce an accurate frequency reference--with emphasis placed on developing techniques and procedures to overcome the limitations found in existing MTS stabilised laser systems. The focus of the thesis is to generate a highly accurate frequency reference by researching the system parameters that will increase the signal to noise ratio and improve the accuracy of the reference through refinement of the signal structure. The early theoretical interpretation of MTS was effectively a low absorption approximation that occurs at low pressures. This approximation ignores the depletion of beam energy through absorption and is a distinct limitation of the theoretical model in its ability to accurately predict the influence of a range of system parameters on signal strength and structure. To overcome this limitation a 3-D (or volumetric) analysis was developed and is presented here for the first time. This volumetric model is a measure of two depleted beams interacting collinearly in an absorbing medium of iodine and is described to accurately predict the signal maximum as a function of pressure for all wavelengths. This model was found to be more accurate in predicting the influence of system parameters on the signal strength and structure, including that of pump beam intensity, pressure, saturation parameter, cell length and modulation parameters. The volumetric model is a novel approach to MTS theory but is more complex computationally than the traditional low pressure model and therefore more difficult to implement in many situations. To overcome this problem a hybrid model was developed as a combination of the low pressure and volumetric models. The comparison between the rigorous volume model and the hybrid model indicate that there is a deviation in the signal strength at high pressures. However, the agreement was very good in the pressure regimes that are commonly used to realise actual frequency references. Comparison of the hybrid model to experimental data was performed over a range of different wavelengths (532 nm, 543.5 nm, 612 nm and 633 nm) and found to be in close agreement. This gives confidence in the model to accurately predict signal strength and structure in any situation. Three mechanisms have been identified that limit the accuracy of frequency references due to the creation of residual amplitude modulation (RAM) where it shifts the frequency of the reference. The influence of RAM is included in the hybrid model as a ratio of the amplitude modulated and frequency modulated components of the saturating beam. These RAM production mechanisms result from the modulation of the saturating beam, the overlap of the beams in the medium, and the differential absorption of the sidebands in the medium. While the first mechanism has been previously reported the latter two are discussed here in detail for the first time. RAM generated by the modulators used (acousto-optic or electro-optic modulators) was typically of the order of 10% to 12%, depending on the excursion of the created sidebands. RAM generated by an asymmetric beam overlap with the modulators used was found to be as large as 30%. A combination of these two independent mechanisms can be used to provide a "RAM-free" state of the system by using one to cancel the effects of the other. The third RAM generation process--medium induced RAM--is difficult to remove but through a careful combination of absorption related parameters--namely, pump intensity, cell length, pressure and detector phase--the effects of RAM can be removed, leading to a distortion free MTS signal. Further investigation into the predictions provided by the hybrid model shows that there is a complex relationship between cell length and the optimum pressure required for maximum signal strength, such that longer cell lengths will not necessarily improve the signal strength. This is contrary to conventional thinking and is important in the MTS design process to reduce unnecessary costs and improve the signal to noise ratio and frequency accuracy. Optimisation of frequency stabilised laser systems using MTS are generally performed using trial and error. Comparison of these optimum parameter values to those predicted by the hybrid model show that for popular wavelengths such as 532 nm they are similar. In addition, the hybrid model is able to predict the frequency shifts that arise within the system parameters used and has shown that existing systems being used at 532 nm, 633 nm and 778 nm could improve their signal to noise ratio and accuracy through a variation in the parameters. A methodology based on the hybrid model is presented that can be used to calculate the optimum parameters for maximum signal strength and a "RAM-free" state for any wavelength. This systematic approach can therefore be used to guide the design of actual frequency stabilised laser systems prior to and during the design process.
10
Heikkinen, Jouko. "TELEMETRY AND RADIO FREQUENCY IDENTIFICATION." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607334.
Повний текст джерелаАнотація:
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaComparison of short-range telemetry and radio frequency identification (RFID) systems reveals that they are based on very similar operating principles. Combining the identification and measurement functions into one transponder sensor offers added value for both RFID and telemetry systems. The presence of a memory (e.g. FRAM) in the transponder, required for ID information, can also be utilized for storing measurement results. For passive transponders low power consumption is one of the main objectives. Wireless power transfer for passive transponder sensors together with above aspects concerning a combined telemetry and identification system are discussed.
11
Andrews, Seth Dixon. "Extensions to Radio Frequency Fingerprinting." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95952.
Повний текст джерелаАнотація:
Radio frequency fingerprinting, a type of physical layer identification, allows identifying wireless transmitters based on their unique hardware. Every wireless transmitter has slight manufacturing variations and differences due to the layout of components. These are manifested as differences in the signal emitted by the device. A variety of techniques have been proposed for identifying transmitters, at the physical layer, based on these differences. This has been successfully demonstrated on a large variety of transmitters and other devices. However, some situations still pose challenges:
Some types of fingerprinting feature are very dependent on the modulated signal, especially features based on the frequency content of a signal. This means that changes in transmitter configuration such as bandwidth or modulation will prevent wireless fingerprinting. Such changes may occur frequently with cognitive radios, and in dynamic spectrum access networks. A method is proposed to transform features to be invariant with respect to changes in transmitter configuration. With the transformed features it is possible to re-identify devices with a high degree of certainty.
Next, improving performance with limited data by identifying devices using observations crowdsourced from multiple receivers is examined. Combinations of three types of observations are defined. These are combinations of fingerprinter output, features extracted from multiple signals, and raw observations of multiple signals. Performance is demonstrated, although the best method is dependent on the feature set. Other considerations are considered, including processing power and the amount of data needed.
Finally, drift in fingerprinting features caused by changes in temperature is examined. Drift results from gradual changes in the physical layer behavior of transmitters, and can have a substantial negative impact on fingerprinting. Even small changes in temperature are found to cause drift, with the oscillator as the primary source of this drift (and other variation) in the fingerprints used. Various methods are tested to compensate for these changes. It is shown that frequency based features not dependent on the carrier are unaffected by drift, but are not able to distinguish between devices. Several models are examined which can improve performance when drift is present.Doctor of Philosophy
Radio frequency fingerprinting allows uniquely identifying a transmitter based on characteristics of the signal it emits. In this dissertation several extensions to current fingerprinting techniques are given. Together, these allow identification of transmitters which have changed the signal sent, identifying using different measurement types, and compensating for variation in a transmitter's behavior due to changes in temperature.
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Terassa, Laura Anna Maria [Verfasser], Christian [Akademischer Betreuer] Mair, and Bernd [Akademischer Betreuer] Kortmann. "Morphological simplification in Asian Englishes : : frequency, substratum transfer, and institutionalization." Freiburg : Universität, 2019. http://d-nb.info/1178321495/34.
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Oyeka, Dumtoochukwu Obiora. "Digitally fabricated epidermal transfer tattoo UHF radio frequency identification tags." Thesis, University of Kent, 2015. https://kar.kent.ac.uk/56651/.
Повний текст джерелаАнотація:
This thesis focuses on the inkjet printing of UHF RFID tags in the form of transfer tattoos for use on the skin. Inkjet printing of these tags is proposed as a cheaper and more appropriate alternative to conventional etching. The work seeks to assesses the performance of inkjet printed epidermal RFID tags using parameters such as read range, transmitted power and backscattered power. The effect of different printing parameters such as the number of conductive ink layers, sintering time and temperature on the performance of the tags are assessed by simulation and measurement. Additionally, techniques to reduce the volume of conductive ink used for the fabrication of the tag are also examined and compared with an aim to determine which has the best achieved read range and ink utilization balance. This would help to reduce the cost of fabrication of the tags. Also, due to some defects being introduced to the tags during the printing process because of printing conditions and characteristics inherent to the printing technology, the effects of these defects on the performance of the printed tag is also examined by simulation and measurement. The robustness of the epidermal transfer tattoo tag was further experimentally determined by exposure to everyday use conditions and situations involving sweat and mechanical friction. Finally, a diversity study on an inkjet printed tag integrated with a medical sticking plaster was performed. This involved the use of two to four tags placed horizontally and vertically in order to determine which orientation offers better read coverage in each of the diversity setups while a volunteer carried out a set of motions.
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Kapoor, Gaurav. "Secure ownership transfer and authentication protocols for Radio Frequency Identification (RFID)." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0022783.
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Maschino, Tyler Stephen. "FREQUENCY-SELECTIVE DESIGN OF WIRELESS POWER TRANSFER SYSTEMS FOR CONTROLLED ACCESS APPLICATIONS." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461787114.
Повний текст джерела
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Droste, Stefan [Verfasser]. "Optical frequency transfer via telecommunication fiber links for metrological applications / Stefan Droste." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1065397607/34.
Повний текст джерела
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Caldas, Fernando Pinto. "Drying of granulated products by conventional heat transfer and high-frequency techniques." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/35994.
Повний текст джерелаАнотація:
In this study the contribution of the different heat transfer methods in the drying of granulated materials is analysed from the viewpoint of the available electro-heat technology. Although the work has been directed to present day commercial applications and proposes definite drying schemes the research has been focused on high frequency heating techniques, which appear to be the most promising alternatives as far as medium and large throughput continuous processes are concerned. An experimental rig has been designed and built, this unit has been used to obtain a preliminary set of data on the performance of the high frequency drying process under different operating conditions.
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Dodson, Kathryn Kristine. "Transfer Frequency of CMY-2-Encoding Plasmids Among Fecal Flora of Pigs." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1395851225.
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19
Schulte, Walter B. III. "The frequency response, impulse response, and transfer function of an ocean waveguide." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1516.
Повний текст джерелаАнотація:
Approved for public release, distribution is unlimitedIn this thesis, the ocean was modeled as a waveguide with an ideal pressure - release surface, and an ideal rigid bottom. The ocean waveguide was then treated as a linear, time - invariant, space - variant (TISV) filter or communication channel. The filter is time - invariant because no motion was modeled and because the properties of the ocean were assumed to be constant. The filter is space - variant because of the presence of the two boundaries, that is, the ocean surface and ocean bottom. This thesis investigates the ocean as a linear TISV filter by evaluating 1) the complex frequency response, 2) the impulse response, and 3) the transfer function of the ocean with respect to depth. It is shown that the TISV impulse response of the ocean contains information that can be used to help localize a target in range and whether the target is above or below the receiver. Computer simulation results were obtained by evaluating the three filter functions for several different test cases.
Ensign, United States Navy
20
Schulte, Walter B. "The frequency response, impulse response, and transfer function of an ocean waveguide /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSchulte.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Applied Science (Signal Processing))--Naval Postgraduate School, June 2004.Thesis advisor(s): Lawrence J. Ziomek. Includes bibliographical references (p. 47). Also available online.
21
Djurberg, Axel, Fredrik Forsberg, Anton Lind, and Ludvig Snihs. "Wireless Power Transfer in Cavity Resonator." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444250.
Повний текст джерелаАнотація:
The purpose of this paper is to achieve wireless power transfer inside a resonating cavity, and thereby apply this to charge batteries. The idea is to convert radio frequency waves into direct current, which can charge the batteries. This was done by creating an LC-antenna, which in turn was connected to a rectifier. A data logger was also built, this to be able to read and log the power within the cavity to examine its power distribution. Because of COVID-19 restrictions, access to laboratory and equipment was limited. Due to this, smaller experiments where performed to make sure that all parts worked as intended before trying to perform tests inside the cavity resonator. The results were varied, some favorable, some not. However, all experiments gave insight and further understanding on the issue. The cavity operations had varied results. The data logger was able to pick up, at most, 7.6 % of the power output by the function generator. However, some problems arose with the rectifier which resulted in it not working for higher frequencies. Though, it was capable of rectifying RF signals at lower frequencies from a function generator, which was used to charge a battery. Consequently, there was no charging of batteries inside the cavity. However, three dimensional wireless power transfer was achieved. With some improvements to the current designs, the main goal could be accomplished
22
PANDEY, AJIT K. "RADIO-FREQUENCY ABLATION IN A RECONSTRUCTED REALISTIC HEPATIC TISSUE." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061210342.
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23
McCune, Robert E. "Identification of Continuous-Time and Discrete-Time Transfer Function Models from Frequency Response Measurements." Ohio University / OhioLINK, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1239731009.
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24
Lalonde, Jasmin. "Task-dependent transfer of perceptual to memory representations during delayed spatial frequency discrimination." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33911.
Повний текст джерелаАнотація:
Discrimination thresholds were obtained during a delayed spatial frequency discrimination task. In Experiment 1, we found that presentation of a mask 3 s before onset of a reference Gabor patch caused selective interference in a subsequent discrimination task. However, a 10 s interval abolished this masking effect. In Experiment 2, the mask was associated with a second spatial frequency discrimination task so that a representation of the mask had to be coded into short-term perceptual memory. The presence of this second discrimination task now caused similar interference effects on the primary discrimination task at both the 3 s and 10 s ISI conditions. The different results from these two experiments are best explained by a two-step perceptual memory mechanism. The results also provide further insight into the conditions under which stimulus representations are shared between the perceptual and memory domains.
25
Alagappan, Azhagammai. "Studies of collisional energy transfer in the CN radical by frequency-modulated spectroscopy." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/62.
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26
Senturk, Sabri. "Experimental Determination Of Transfer Functions For A Car Body-in-white." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604899/index.pdf.
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Vibration generated from various sources (engine, road surface, tires, exhaust, etc.) should be considered in the design of a car body. These vibrations travel through transfer systems (drivetrain, suspension, body, etc.) to the steering wheel, seats and other areas where it is detected by the passengers of the vehicle. Transmission routes must be studied and efforts made to keep transfer systems from amplifying vibration and to absorb it instead. Since the superior vibration transfer system is the car body, finite element analysis and experimental vibration analysis are performed on car body-in-white. Body vibration analysis entails understanding and improving the body&rsquos dynamic characteristics that act as vibration transfer channels. In the previous study, a finite element model has been created for a car body-in-white available in Automotive Laboratory (Mechanical Engineering Department, Middle East Technical University, Ankara) and its natural frequencies and mode shapes have been determined using finite element analysis software. In this study, vibration tests have been performed on actual car body-in-white. Frequency response functions between 34 response locations and force application point have been measured. Using these frequency response functions, natural frequencies and mode shapes of the body-in-white have been determined. Finite element analysis and experimental results have been compared to evaluate the finite element model reliability.
27
Zhao, Yanzhu. "Metal-transfer-molding (MTM) technique for micromachined RF components." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24750.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Mark G. Allen; Committee Member: J. Stevenson Kenney; Committee Member: Joy Laskar; Committee Member: Oliver Brand; Committee Member: Peter Hesketh.
28
Fotopoulou, Kyriaki. "Inductive wireless power transfer for RFID & embedded devices : coil misalignment analysis and design." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/10907.
Повний текст джерелаАнотація:
Radio frequency inductive coupling is extensively employed for wireless powering of embedded devices such as low power passive near-field RFID systems and implanted sensors. The efficiency of low power inductive links is typically less than 1%and is characterised by very unfavourable coupling conditions, which can vary significantly due to coil position and geometry. Although, a considerable volume of knowledge is available on this topic, most of the existing research is focused on the circuital modeling of the transformer action between the external and implanted coils. The practical issues of coil misalignment and orientation and their implications on transmission characteristics of RF links have been overlooked by researchers. The aim of this work is to present a novel analytical model for near-field inductive power transfer incorporating misalignment of the RF coil system. In this thesis the influence of coil orientation, position and geometry on the link efficiency is studied by approaching the problem from an electromagnetic perspective. In implanted devices some degree of misalignment is inevitable between external and implanted coils due to anatomical requirements. First two types of realistic misalignments are studied; a lateral displacement of the coils and an angular misalignment described as a tilt of the receiver coil. A loosely coupled system approximation is adopted since, for the coil dimensions and orientations envisaged, the mutual inductance between the transmitter and receiver coils can be neglected. Following this, formulae are derived for the magnetic field at the implanted coil when it is laterally and angularly misaligned from the external coil and a new power transfer function presented. The magnetic field solution is carried out for a number of practical antenna coil geometries currently popular in RFID and biomedical domains, such as planar and printed square, and circular spirals as well as conventional air-cored and ferromagnetic solenoids. In the second phase of this thesis, the results from the electromagnetic modeling are embodied in a near-field loosely coupled equivalent circuit for the inductive link. This allows us to introduce a power transfer formula incorporating for the first time coil characteristics and misalignment factors. This novel power transfer function allows a comparison between different coil structures such as short solenoids, with air or ferromagnetic core, planar and printed spirals with respect to power delivered at the receiver and its relative position to the transmitter. In the final stage of this work, the experimental verification of the model shows close agreement with the theoretical predictions. Using this analysis a formal design procedure is suggested that can be applied on a larger scale compared to existing methods. The main advantage of this technique is that it can be applied to a wide range of implementations without the limitations imposed by numerical modeling and existing circuital methods. Consequently, the designer has the flexibility to identify the optimum coil geometry for maximum power transfer and misalignment tolerance that suit the specifications of the application considered. This thesis concludes by suggesting a new optimisation technique for maximum power transfer with respect to read range, coil orientation, geometry and operating frequency. Finally, the limitations of this model are reiterated and possible future development of this research is discussed.
29
Yang, Shuai. "Alternative power transfer for passive RFID systems in challenging applications." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270885.
Повний текст джерелаАнотація:
This dissertation presents a case study which attempts to implement a passive Ultra High Frequency Radio Frequency Identification (UHF RFID) system on aircraft landing gear (LG) to permit component configuration management. It is shown that a monostatic RFID system with two reader antennas, one on the LG main fitting and one in the wing bay allows up to 64 kbits of data to be associated with each LG component. A 7 dB system margin allows data on each LG component to be updated wirelessly and will also enable a passive UHF RFID-based LG health and usage monitoring system when tags with required sensors become available. Results from an electromagnetic simulation show that when a metal is illuminated by a nearby antenna the E-field distribution close to its surface is stronger than in free space. To explore if the stronger E-field can be used to enhance the performance of a conventional passive tag, a 5 cm × 6 mm × 3.02 m aluminium bar has been selected as the tagging object and connected to the reader via an RF feed. It is shown that a conventional metal tag which has a maximum free space range of 1.3 m when mounted on a metal plate can be detected up to 30 m along the aluminium bar from the RF feed. When orientated with the long axis normal to the metal surface a conventional passive tag with a dipole antenna can efficiently harvest the E- field and can be read at least 50 m away from the antenna feed. The proposed use of metal objects as a nearfield antenna is well suited to some applications, but in others a significant wireless path is still required. In such a case, a semi-passive tag can be used. It is demonstrated that a semi-passive tag only requires 14.4 ̧œ‡̧‘Š to be read over 42 m in a bistatic RFID system. Such a power consumption can be easily achieved by most energy harvesting techniques. It is demonstrated that a solar-powered semi-passive tag can be read at a range of 22 m, but its performance is still limited by multipath effects. A distributed antenna system (DAS) can be used to overcome these effects by using frequency and phase hopping techniques. It is demonstrated that 50 solar-powered semi-passive tags can be read with no missed detections over a 10 m × 20 m office area with 4 dB system margin.
30
Sharma, Ragahv. "Behavioral Modeling and FPGA Synthesis of IEEE 802.11n Orthogonal Frequency Division Multiplexing (OFDM) Scheme." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6584.
Повний текст джерелаАнотація:
In the field of communications, a high data rate and low multi-path fading is required for efficient information exchange. Orthogonal Frequency Division Multiplexing (OFDM) is a widely accepted IEEE 802.11n (and many others) standard for usage in communication systems operating in fading dispersive channels. In this thesis, we modeled the OFDM algorithm at the behavioral level in VHDL/Verilog that was successfully synthesized/verified on an FPGA. Due to rapid technology scaling, FPGAs have become popular and are low-cost and high performance alternatives to (semi-) custom ASICs. Further, due to reprogramming flexibility, FPGAs are useful in rapid prototyping. As per the IEEE standard, we implemented both transmitter and receiver with four modulation schemes (BPSK, QPSK, QAM16, and QAM64). We extensively verified the design in simulation as well as on Altera Stratix IV EP4SGX230KF40C2 FPGA (Terasic DE4 Development Board). The synthesized design ran at 100 MHz clock frequency incurring 54 µ sec. end-to-end latency and 8% logic utilization.
31
Pathmanathan, Shaetrun. "Development and analysis of wireless power transfer communication systems for left Ventricular Assist Devices." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/229220/1/Shaetrun_Pathmanathan_Thesis.pdf.
Повний текст джерелаАнотація:
Where Ventricular Assist Devices show great promise in extending human life, relying on a driveline piercing the human body makes this unattractive. Wireless Power Transfer replaces this but requires an effective wireless implant feedback system. This project explores the development of an inductive power transfer assistive communication system, considering the implant environment’s delaying effect on time critical feedback communications. Experimental measurements of this delayed feedback loop were simulated with, to verify its effect on the wireless power transfer system, producing the results in this study. An improvement to the wireless power transfer control system is suggested to compensate for this.
32
Babendreier, Justin Eric. "Near aggregation: a time and frequency domain analysis using state trajectories and transfer function residues." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/91080.
Повний текст джерелаАнотація:
In this thesis we investigate concepts associated with aggregation. The basic idea of aggregation is that there exists a reduced order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are linear combinations of the trajectories of the ful 1-order model. We study systems which do not aggregate exactly, but which "nearly aggregate". It is shown that for "nearly aggregable" systems there exists a reduced-order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are near a linear combination of the trajectories of the full-order model.
Under certain conditions it has also been shown that near-aggregation is equivalent to near-unobservability (roughly, an invariant subspace close to the null space of C). Here we establish a relationship between near-unobservability and modal measures of observability as suggested by Selective Modal Analysis. With this result we then obtain an upper bound on the norm of the transfer function residue using near-unobservability measures. The Generalized Hessenberg Representation (GHR) and Dual GHR are examined throughout this analysis. It is finally shown that for SISO systems, the residue norm may be expressed in terms of certain parameters of the Dual GHR.M.S.
33
He, Shujian. "A TRANSFER MATRIX APPROACH TO DETERMINE THE LOW FREQUENCY INSERTION LOSS OF ENCLOSURES INCLUDING APPLICATIONS." UKnowledge, 2017. https://uknowledge.uky.edu/me_etds/104.
Повний текст джерелаАнотація:
Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can be predicted rapidly. Results are compared to finite element analysis and measurement with good agreement. The approach is then used to design and place resonators into a sample enclosure. Improvements in enclosure performance are predicted using plane wave simulation, compared with acoustic finite element analysis, and then validated via measurement.
34
Fayon, Lucile. "Instrumentation sismologique spatiale : Fonction de transfert du sismomètre 6 axes InSight et développement d'un capteur de déplacement picométrique par interférométrie." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC099/document.
Повний текст джерелаАнотація:
La compréhension de la formation du Système Solaire et de son Evolution est profondément connectée aux connaissances que nous pouvons avoir sur les structures internes des planètes. Des études sismiques in-situ sont donc cruciales pour sonder la structure (répartition et Épaisseur des couches) et la composition interne des planètes telluriques. L'instrument SEIS (Seismic Experiment for Interior Structure) se posera sur Mars en 2018 (mission InSight de la NASA). Il contient deux types de capteurs sismiques: les VBB (Very Broad Band) et SP (Short Period), montés sur le LVL (système de nivellement mécanique) qui a un double objectif: assurer le placement horizontal des capteurs sur le sol de Mars dans des conditions locales inconnues et fournir le couplage mécanique des sismomètres au sol. Dans cette thèse, un modèle analytique simple du LVL est développé afin de reproduire son comportement mécanique grâce au calcul de ses résonnances et de sa fonction de transfert. Ce modèle permettra d'étudier l'effet du LVL sur les données sismiques des VBB et SP enregistrées sur Mars. Celui-ci est d'abord implémenté numériquement puis sa validation est garantie grâce ˆ l'observation de grandes similitudes entre nos résultats et ceux des expériences réalisées en laboratoire avec le modèle de vol. Ces comparaisons prouvent ainsi la fidélité du modèle ˆ la réalité. Après quelques simulations, on remarque également une influence importante du couplage mécanique entre les pieds du LVL et le sol dans les résonnances trouvées. Une étude d'inversion est alors réalisée afin d'observer si le modèle pourrait permettre d'estimer les propriétés du sol au niveau du site d'atterrissage InSight. Un autre travail consiste ˆ modéliser les 6 capteurs VBB et SP sur le LVL et observer la réponse de l'instrument global en translation et en rotation. En effet, des effets de rotation du LVL ˆ courte période peuvent perturber les mesures sismiques. Cette étude peut aussi permettre d'estimer les performances en rotation de SEIS, qui peut être une information clé pour déterminer la vitesse de phase des ondes sismiques de surface, fortement dépendante de la composition du sol. Cette vitesse sera calculée sur Mars en réalisant une expérience sismique active grâce ˆ l'autre instrument principal d'InSight: HP3. Aujourd'hui, de nouveaux projets sont étudiés pour un retour sismique sur la Lune. En effet, les sismomètres Apollo bien qu'ayant une bonne résolution en terme de déplacement du sol étaient cependant incapables de détecter le bruit sismique du sol lunaire, appelé "meteoritic hum". Ce bruit, du aux chutes continues de micrométéorites, a une amplitude estimée ˆ 1/100e de la résolution des sismomètres Apollo ˆ une certaine fréquence. Les phases sismiques du noyau, même si estimées grâce au "stacking" des données, n'ont pas non plus été directement enregistrées. Une nouvelle génération de sismomètres, 100 ˆ 1000 fois plus sensibles que ceux d'Apollo, est donc désirée pour atteindre le plancher du bruit sismique lunaire. Cette sensibilité pourrait permettre de tirer bénéfice de l'intégralité des ondes sismiques générées par l'activité sismique lunaire. La structure d'un tel sismomètre serait un capteur de déplacement, toujours lié ˆ une masse d'épreuve, mais présentant de grosses améliorations en termes de performance, linéarité, et niveau de bruit. Pendant cette thèse, un prototype de système de lecture optique du déplacement de la future masse d'épreuve de ce sismomètre lunaire ultra-sensible est développé, basé sur l'utilisation de la technologie des détecteurs d'ondes gravitationnelles. En effet, ceux-ci sont une référence en termes de mesures interférométriques ˆ basse fréquence et très bas niveau de bruit. Le prototype construit est ainsi basé sur la technique de stabilisation laser appelée "Pound-Drever-Hall"The understanding of the Solar System formation and its evolution is deeply connected to the knowledge on the planet interior structures. In situ studies with seismometers are therefore crucial to probe the internal structure (distribution and thickness of layers) and composition of the telluric planets. Indeed, SEIS (Seismic Experiment for Interior Structure) will land on Mars in 2018 (NASA InSight mission). Both types of sensors of the SEIS instrument, the VBB (Very Broad Band) and SP (Short Period), are mounted on the LVL (a mechanical levelling system) for which the purpose is twofold: ensure a level placement of the sensors on the Martian ground under yet unknown local conditions and provide the mechanical coupling of the seismometers to the ground. In this thesis, we developed a simplified analytical model of the LVL structure in order to reproduce its mechanical behaviour by predicting its resonances and transfer function. This model will allow to estimate the LVL effect on the VBB and SP data recorded on Mars. It is first implemented numerically and its validation is then guaranteed thanks to the observation of a lot of similarities between our results and those of the laboratory experiments with the LVL flight model. These comparisons prove the model fidelity with reality. After some simulations, we noticed a clear influence of the mechanical coupling between the LVL feet and the ground in the resonances found. For this reason, an inversion study has been realized in order to study if this model could allow to estimate the ground properties of the InSight site. Another work consists in modeling the 3 VBB sensors and the 3 SP sensors on the LVL and to observe the response of the global SEIS instrument in translation and rotation. Indeed, some rotation effects at short period can disturb the seismic measurements. This study can also allows to estimate the performances of SEIS, especially in rotation that can be one important information to recover the phase velocity of the surface seismic waves, highly dependent of the ground composition. This can be realized on Mars with an active seismic experiment thanks to the other main instrument of InSight mission: HP3. Today, new projects are also considered for a seismic return on the Moon. Indeed, the Apollo seismometers had a good resolution in ground displacement but were however unable to detect the Lunar ground seismic noise, named "meteoritic hum". This noise is possibly due to the continuous fall of micro-meteorites and its amplitude has been estimated to be about 1/100 of the resolution of the Apollo sensors at a certain frequency. Core seismic phases, although detected through stacking, have not also been individually recorded. A new generation of broadband seismometers, 100 to 1000 times more sensitive than the Apollo ones are therefore requested in order to reach the lunar seismic noise floor. This sensitivity will allow to take benefit of all the seismic waves generated by the Moon seismic activity. The core of such seismometer will be the proof mass displacement sensors, with extreme improvement in performances, linearity and noise level. During this thesis, we developed an optical readout prototype, based on the use of gravitational waves detectorsÕ technology which is the reference in term of interferometric measurements at low frequency and very low noise levels. This prototype is based on the "Pound-Drever-Hall" laser frequency stabilization technique. The objective is to improve the sensitivity by 2 orders of magnitude compared to the current seismometers performances
35
Feng, Junjie. "6.78MHz Omnidirectional Wireless Power Transfer System for Portable Devices Application." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/101839.
Повний текст джерелаАнотація:
Wireless power transfer (WPT) with loosely coupled coils is a promising solution to deliver power to a battery in a variety of applications. Due to its convenience, wireless power transfer technology has become popular in consumer electronics. Thus far, the majority of the coupled coils in these systems are planar structure, and the magnetic field induced by the transmitter coil is in one direction, meaning that the energy power transfer capability degrades greatly when there is some angle misalignment between the coupled coils.
To improve the charging flexibility, a three–dimensional (3D) coils structure is proposed to transfer energy in different directions. With appropriate modulation current flowing through each transmitter coil, the magnetic field rotates in different directions and covers all the directions in 3D space. With omnidirectional magnetic field, the charging platform can provide energy transfer in any direction; therefore, the angle alignment between the transmitter coil and receiver coil is no longer needed.
Compensation networks are normally used to improve the power transfer capability of a WPT system with loosely coupled coils. The resonant circuits, formed by the loosely coupled coils and external compensation inductors or capacitors, are crucial in the converter design. In WPT system, the coupling coefficient between the transmitting coil and the receiving coil is subject to the receiver's positioning. The variable coupling condition is a big challenge to the resonant topology selection. The detailed requirements of the resonant converter in an omnidirectional WPT system are identified as follows: 1). coupling independent resonant frequency; 2). load independent output voltage; 3). load independent transmitter coil current; 4). maximum efficiency power transfer; 5). soft switching of active devices. A LCCL-LC resonant converter is derived to satisfy all of the five requirements.
In consumer electronics applications, Megahertz (MHz) WPT systems are used to improve the charging spatial freedom. 6.78 MHz is selected as the system operation in AirFuel standard, a wireless charging standard for commercial electronics. The zero voltage switching (ZVS) operation of the switching devices is essential in reducing the switching loss and the switching related electromagnetic interference (EMI) issue in a MHz system; therefore, a comprehensive evaluation of ZVS condition in an omnidirectional WPT system is performed. And a design methodology of the LCCL-LC converter to achieve ZVS operation is proposed.
The big hurdle of the WPT technology is the safety issue related to human exposure of electromagnetic fields (EMF). A double layer shield structure, including a magnetic layer and a conductive layer, is proposed in a three dimensional charging setup to reduce the stray magnetic field level. A parametric analysis of the double shield structure is conducted to improve the attenuation capability of the shielding structure.
In an omnidirectional WPT system, the energy can be transferred in any direction; however the receiving devices has its preferred field direction based on its positioning and orientation. To focus power transfer towards targeted loads, a smart detection algorithm for identifying the positioning and orientation of receiver devices based on the input power information is presented. The system efficiency is further improved by a maximum efficiency point tracking function. A novel power flow control with a load combination strategy to charge multiple loads simultaneously is explained. The charging speed of the omnidirectional WPT system is greatly improved with proposed power flow control.Doctor of Philosophy
Wireless power transfer (WPT) is a promising solution to deliver power to a battery in a variety of applications. Due to its convenience, wireless power transfer technology with loosely coupled coils has become popular in consumer electronics. In such system, the receiving coil embedded in the receiving device picks up magnetic field induced by the transmitter coil; therefore, energy is transferred through the magnetic field and contactless charging is achieved. Thus far, the majority of the coupled coils in these systems are planar structure, and the magnetic field induced by the transmitter coil is in one direction, meaning that the energy power transfer capability degrades greatly when there is some angle misalignment between the coupled coils. To improve the charging flexibility, a three–dimensional (3D) coils structure is proposed to transfer energy in different directions, also known as in omnidirectional manner. With omnidirectional magnetic field, the charging platform can provide energy transfer in any direction; therefore, the angle alignment between the transmitter coil and receiver coil is no longer needed. In a WPT system with loosely coupled coils, the energy transfer capability suffers from weak coupling condition. To improve the power transfer capability, the electrical resonance concept between the inductor and capacitor at the power transfer frequency is adopted. A novel compensation network is proposed to form a resonant tank with the loosely coupled coils and maximize the power transfer at the operating frequency. As for the WPT system with loosely coupled coils, the energy transfer capability is also proportional to the operating frequency. Therefore, Megahertz (MHz) WPT systems are used to improve the charging spatial freedom. 6.78 MHz is selected as the system operation in AirFuel standard, a wireless charging standard for commercial electronics. The zero voltage switching (ZVS) operation of the switching devices is essential in reducing the switching loss and the switching related electromagnetic interference (EMI) issue in a MHz system; therefore, a comprehensive evaluation of ZVS condition in an omnidirectional WPT system is performed. The big hurdle of the WPT technology is the safety concern related to human exposure of electromagnetic fields (EMF). Therefore, a double layer shield structure is first applied in a three dimensional charging setup to confine the electromagnetic fields effectively. The stray field level in our charging platform is well below the safety level required by the regulation agent. Although the energy can be transferred in an omnidirectional manner in the proposed charging platform, the energy should be directed to the target loads to avoid unnecessary energy waste. Therefore, a smart detection method is proposed to detect the receiver coil's orientation and focus the energy transfer to certain direction preferred by the receiver in the setup. The energy beaming strategy greatly improves the charging speed of the charging setup.
36
Mohieldin, Ahmed Nader. "High performance continuous-time filters for information transfer systems." Texas A&M University, 2003. http://hdl.handle.net/1969/233.
Повний текст джерела
37
Döringshoff, Klaus. "Optical frequency references based on hyperfine transitions in molecular iodine." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19156.
Повний текст джерелаАнотація:
Diese Arbeit beschäftigt sich mit der Entwicklung und Untersuchung von optischen Absolutfrequenzreferenzen basierend auf rovibronischen Übergängen in molekularen Jod. Dabei werden Methoden der Doppler-freien Sättigungsspektroskopie angewendet, um einzelne Übergänge der Hyperfeinstruktur mit Linienbreiten unterhalb von 1 MHz im B-X System von molekularem Iod bei 532 nm, der zweiten harmonischen des Nd:YAG-Laser, aufzulösen. Elektronische Regelungstechniken ermöglichen eine präzise Stabilisierung der optischen Frequenz auf die Linienmitte der Übergänge mit einer Auflösung von Teilen in 10^5.
Mit dem Ziel einer weltraumtauglichen Absolutfrequenzreferenz für zukünftige Weltraummissionen, wurden zwei Spektroskopiemodule konzipiert und in quasi-monolithischen Glaskeramik-Aufbauten, als sogenanntes elegant breadboard model und engineering model, realisiert. Diese Jodfrequenzreferenzen wurden im Detail in Bezug auf ihre Frequenzstabilität und Reproduzierbarkeit untersucht und Letzteres wurde für die angestrebte Weltraumqualifizierung ersten Umwelttests, sowohl vibrations- als auch thermischen Belastungstests, unterzogen.
Für die Untersuchung der Frequenzstabilität dieser Jodreferenzen wurde ein auf einen optischen Resonator hoher Güte stabilisiertes Lasersystem für direkte Frequenzvergleiche bei 1064 nm realisiert. Die Analyse der Frequenzstabilität der Jod Referenzen zeigt eine Frequenzstabilität von 6x10^−15 bei 1 s, und weniger als 2x10^−15 bei 100 s Integrationszeit, was der bis heute besten veröffentlichten Frequenzstabilität entspricht die mit Jod Referenzen erreicht wurde.
Mit der erreichten Frequenzstabilität ermöglichen diese Absolutfrequenzreferenzen präzise Lasersysteme für zukünftige Weltraummissionen wie z.B. zur Detektion von Gravitationswellen, zur Vermessung des Gravitationsfelds der Erde oder für Präzisionstest fundamentaler Theorien der Physik.This thesis deals with the development and investigation of optical absolute frequency references based on rovibronic transitions in molecular iodine. Doppler-free saturation spectroscopy methods are employed to resolve individual transitions of the hyperfine structure with linewidths below 1 MHz in the B-X system of molecular iodine at 532 nm with the second harmonic of Nd:YAG lasers. Electronic feedback control systems are employed for laser frequency stabilization to the line center of the optical transitions with a line splitting of 10^5. With the goal of a space qualified optical absolute frequency reference for future laser-interferometric space missions, two spectroscopy setups were designed and realized in quasi-monolithic, glass-ceramic setups as so called elegant bread board model and engineering model. These iodine references were characterized in detail with respect to their frequency stability and reproducibility and the engineering model was subject to environmental tests, including vibrations and thermal cycling to verify its applicability in future space missions. For the investigation of the frequency instability of these iodine references, a frequency stabilized laser system was realized based on a temperature controlled high Finesse ULE cavity for direct frequency comparisons at 1064 nm. Analysis of the frequency stability of the iodine references revealed exceptionally low fractional frequency instability of 6x10^−15 at 1 s, averaging down to less than 2×10^−15 at 100 s integration time, constituting the best reported stability achieved with iodine references to date. With the demonstrated performance, these absolute frequency references enable precision laser systems required for future space missions that are dedicated to, e.g., the detection of gravitational waves, mapping of the Earth’s gravitational field or precision test of fundamental physics.
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Wang, Ce. "Study on Novel Rectifiers for Microwave Wireless Power Transfer System." Kyoto University, 2020. http://hdl.handle.net/2433/253503.
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DeLong, Brock J. "Integration of Radio Frequency Harvesting with Low Power Sensors." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152408949118599.
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Bihl, Trevor Joseph. "State Variable System Identification through Frequency Domain Techniques." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1307128475.
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Roa, Rodríguez Rodrigo, and Robert Lundin. "Heatmap Visualization of Neural Frequency Data." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-186860.
Повний текст джерелаАнотація:
Complex spatial relationships and patterns in multivariate data are relatively simple to identify visually but di cult to detect computation- ally. For this reason, Anivis, an interactive tool for visual exploration of multivariate quantitative pure serial periodic data was developed. The data has four dimensions depth, laterality, frequency and time. The data was visualized as an animated heatmap, by mapping depth and laterality to coordinates in a pixel grid and frequency to color. Transfer functions were devised to map a single variable to color through parametric curves. Anivis implemented heatmap generation through both weighted sum and deconvolution for comparison reasons. Deconvolution exhibited a to have better theoretical and practical performance. In addition to the heatmap visualization a scatter-plot was added in order to visualize the causal relationships between data points and high value areas in the heatmap visualization. Performance and applicability of the tool were tested and verified on experimental data from the Karolinksa Institute’s Department of Neuroscience.Komplexa spatiala mo ̈nster och fo ̈rh ̊allanden i multivariat data a ̈r rel- ativt sv ̊ara att identifiera via bera ̈kningar men simpla att identifiera vi- suellt. Att visualisera data fo ̈r denna typ av data-analys anva ̈nds ofta i m ̊anga olika typer av fa ̈lt. Detta motiverade utvecklingen av Anivis; ett interaktivt verktyg fo ̈r visuell utforskning av multivariat kvantitativ data av neural aktivitet. Anivis anva ̈nder sig av dataset baserade p ̊a experi- mentell data fr ̊an en forskningsgrupp p ̊a Karolinska Institutets Institution fo ̈r Neurovetenskap. Dessa fyrdimensionella dataset best ̊ar av ma ̈tningar fr ̊an neuroner i form av deras position, aktivitet i form av frekvens och tidpunkt. Denna data anva ̈nds fo ̈r att generera en animerad heatmap, da ̈r neuroners frekvensva ̈rden visas i form av f ̈arg. Frekvensva ̈rdena om- vandlades till fa ̈rgva ̈rden via ̈overg ̊angsfunktioner som kopplar numeriska va ̈rden till fa ̈rgva ̈rden via parametriserade kurvor. Anivis lyckades imple- mentera tv ̊a olika metoder f ̈or att generera heatmap, viktade summor och dekonvolution. Dessa tv ̊a metoder ja ̈mfo ̈rdes med varandra, varav dekon- volution visade sig vara den teoretiskt och praktiskt e↵ektivaste meto- den. Utvecklingen av Anivis visade a ̈ven behovet fo ̈r ett punktdiagram fo ̈r att visualisera f ̈orh ̊allandet mellan ma ̈tta frekvensv ̈arden och spatial frekvensfo ̈rdelning i heatmappen.
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Shin, Yoon Shik. "Modifications to a two-control-volume, frequency dependent, transfer-function analysis of hole-pattern gas annular seals." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4751.
Повний текст джерелаАнотація:
A rotordynamic analysis of hole-pattern gas annular seals using a two-control-volume model, Ha and Childs and frequency dependent transfer-function model, Kleynhans and Childs is modified with four features. The energy equation is added, and real gas properties are used instead of the ideal gas equation of state. The depth of the hole-pattern is made variable with the axial distance along the seal. And last, the addition of deep grooves to hole-pattern seals is analyzed, and the codeâÂÂs predictions for the influence of a groove are compared with test data.
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Holmberg, David G. "A frequency domain analysis of surface heat transfer/free-stream turbulence interactions in a transonic turbine cascade." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-154531/.
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Birchfield, Neal Spencer. "STRUCTURAL MODIFICATION OF A COUPLED ROTORDYNAMIC SYSTEM FROM TRANSFER FUNCTIONS." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1376320545.
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Yang, Taeyoung. "Fundamental Limits on Antenna Size for Frequency and Time Domain Applications." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/39334.
Повний текст джерелаАнотація:
As ubiquitous wireless communication becomes part of life, the demand on antenna miniaturization and interference reduction becomes more extreme. However, antenna size and performance are limited by radiation physics, not technology.
In order to understand antenna radiation and energy storage mechanisms, classical and alternative viewpoints of radiation are discussed. Unlike the common sense of classical antenna radiation, it is shown that the entire antenna fields contribute to both radiation and energy storage with varying total energy velocity during the radiation process. These observations were obtained through investigating impedance, power, the Poynting vector, and energy velocity of a radiating antenna.
Antenna transfer functions were investigated to understand the real-world challenges in antenna design and overall performance. An extended model, using both the singularity expansion method and spherical mode decomposition, is introduced to analyze the characteristics of various antenna types including resonant, frequency-independent, and ultra-wideband antennas. It is shown that the extended model is useful to understand real-world antennas.
Observations from antenna radiation physics and transfer function modeling lead to both corrections and extension of the classical fundamental-limit theory on antenna size. Both field and circuit viewpoints of the corrected limit theory are presented. The corrected theory is extended for multi-mode excitation cases and also for ultra-wideband and frequency-independent antennas.
Further investigation on the fundamental-limit theory provides new innovations, including a low-Q antenna design approach that reduces antenna interference issues and a generalized approach for designing an antenna close to the theoretical-size limit. Design examples applying these new approaches with simulations and measurements are presented.
The extended limit theory and developed antenna design approaches will find many applications to optimize compact antenna solutions with reduced near-field interactions.Ph. D.
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Thomas, Edward John. "A C++ class library capable of handling matrix, polynomial, transfer function, state space, and frequency response data types." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1178902180.
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Sun, Keyao. "Protection, Control, and Auxiliary Power of Medium-Voltage High-Frequency SiC Devices." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103743.
Повний текст джерелаАнотація:
Due to the superior characteristics compared to its silicon (Si) counterpart, the wide bandgap (WBG) semiconductor enables next-generation power electronics systems with higher efficiency and higher power density. With higher blocking voltage available, WBG devices, especially the silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET), have been widely explored in various medium-voltage (MV) applications in both industry and academia. However, due to the high di/dt and high dv/dt during the switching transient, potential overcurrent, overvoltage, and gate failure can greatly reduce the reliability of implementing SiC MOSFETs in an MV system.
By utilizing the parasitic inductance between the Kelvin- and the power-source terminal, a short-circuit (SC) and overload (OL) dual-protection scheme is proposed for overcurrent protection. A full design procedure and reliability analysis are given for SC circuit design. A novel OL circuit is proposed to protect OL faults at the gate-driver level. The protection procedure can detect an SC fault within 50 nanoseconds and protect the device within 1.1 microsecond. The proposed method is a simple and effective solution for the potential overcurrent problem of the SiC MOSFET.
For SiC MOSFETs in series-connection, the unbalanced voltages can result in system failure due to device breakdown or unbalanced thermal stresses. By injecting current during the turn-off transient, an active dv/dt control method is used for voltage balancing. A 6 kV phase-leg using eight 1.7 kV SiC MOSFETs in series-connection has been tested with voltage balanced accurately. Modeling of the stacked SiC MOSFET with active dv/dt control is also done to summarize the design methodology for an effective and stable system. This method provides a low-loss and compact solution for overvoltage problems when MV SiC MOSFETs are connected in series.
Furthermore, a scalable auxiliary power network is proposed to prevent gate failure caused by unstable gate voltage or EMI interference. The two-stage auxiliary power network (APN) architecture includes a wireless power transfer (WPT) converter supplied by a grounded low voltage dc bus, a high step-down-ratio (HSD) converter powered from dc-link capacitors, and a battery-based mini-UPS backup power supply. The auxiliary-power-only pre-charge and discharge circuits are also designed for a 6 kV power electronics building block (PEBB). The proposed architecture provides a general solution of a scalable and reliable auxiliary power network for the SiC-MOSFET-based MV converter.
For the WPT converter, a multi-objective optimization on efficiency, EMI mitigation, and high voltage insulation capability have been proposed. Specifically, a series-series-CL topology is proposed for the WPT converter. With the optimization and new topology, a 120 W, 48 V to 48 V WPT converter has been tested to be a reliable part of the auxiliary power network.
For the HSD converter, a novel unidirectional voltage-balancing circuit is proposed and connected in an interleaved manner, which provides a fully modular and scalable solution. A ``linear regulator + buck" solution is proposed to be an integrated on-board auxiliary power supply. A 6 kV to 45 V, 100 W converter prototype is built and tested to be another critical part of the auxiliary power network.Doctor of Philosophy
The wide bandgap semiconductor enables next-generation power electronics systems with higher efficiency and higher power density which will reduce the space, weight, and cost for power supply and conversion systems, especially for renewable energy. However, by pushing the system voltage level higher to medium-voltage of tens of kilovolts, although the system has higher efficiency and simpler control, the reliability drops. This dissertation, therefore, focusing on solving the possible overcurrent, overvoltage, and gate failure issues of the power electronics system that is caused by the high voltage and high electromagnetic interference environment. By utilizing the inductance of the device, a dual-protection method is proposed to prevent the overcurrent problem. The overcurrent fault can be detected within tens of nanoseconds so that the device will not be destroyed because of the huge fault current. When multiple devices are connected in series to hold higher voltage, the voltage sharing between different devices becomes another issue. The proposed modeling and control method for series-connected devices can balance the shared voltage, and make the control system stable so that no overvoltage problem will happen due to the non-evenly distributed voltages. Besides the possible overcurrent and overvoltage problems, losing control of the devices due to the unreliable auxiliary power supply is another issue. This dissertation proposed a scalable auxiliary power network with high efficiency, high immunity to electromagnetic interference, and high reliability. In this network, a wireless power transfer converter is designed to provide enough insulation and isolation capability, while a switched capacitor converter is designed to transfer voltage from several kilovolts to tens of volts. With the proposed overcurrent protection method, voltage sharing control, and reliable auxiliary power network, systems utilizing medium-voltage wide-bandgap semiconductor will have higher reliability to be implemented for different applications.
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Arias, Diego Alejandro Guzman. "Hydrological risk transfer planning under the drought \"severity-duration-frequency\" approach as a climate change impact mitigation strategy." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-21062018-104407/.
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Climate change and increasing water demands prioritize the need to implement planning strategies for urban water security in the long and medium term. However, risk planning requires robust and timely financial support during and after the disaster. Therefore, risk transfer tools, such as insurance, have emerged as an effective strategy to ensure financial resilience and as an element that could encourage the implementation of hydrological risk reduction mechanisms. Among the main insurance design problems are the lack of information on the real drought impacts and climate uncertainty, which may incur adverse selection and/or moral hazards among the most common drawbacks in insurance practice. Currently, most of the income from water utility companies is based on water resources management, therefore during prolonged drought periods these economies can be strongly affected, despite having robust storage schemes as support. Thus, this thesis proposes an insurance plan for the water utility company of the State of Sao Paulo (SABESP) to deal with revenue reductions during long drought periods. The methodology is implemented on the MTRH-SHS model, developed under ex-ante damage cost calculation through the risk-based approach. The synthetic (\'what-if\') approach uses a \"set of change drivers\" to estimate the optimal premium through a multiyear insurance contract (MYI). The methodology integrates the hydrological simulation procedures under radiative climate forcing scenarios RCP 4.5 and 8.5, from the regional climate model outputs Eta-HadGEM and Eta-MIROC5, with time horizons of 2007-2040, 2041-2070, and 2071-2099, linked to the Water Evaluation and Planning system (WEAP) hydrologic model and under stationary and non-stationary water supply demand assumptions. The model framework is applied to the Cantareira Water Supply System for the Sao Paulo Metropolitan Region, Brazil, with severe vulnerability to droughts. As a result, the evaluated indexes showed that multi-year contracts with drought coverage higher than 240 days offer better financial performance than contracts with wider coverages. Moreover, this MYI adopted in the installed storage residual risk generates both a higher level of solvency for the insurance fund in the long term and annual average premiums closer to the expected revenue reductions by scenario. Finally, the approach can help the systematic evaluation of moral hazards and adverse selection. In the first case, the progressive evaluation must generate useful information to change or maintain the behavior of both the insured and insurers considering future risks related to climate change. In the second case, the multi-scenario valuation can help the insurer to set price thresholds, offering risk differential cover options in the premium value.As mudanças climáticas e o incremento na demanda de água priorizam a necessidade de implementar estratégias de planejamento para a segurança hídrica urbana no longo e mediano prazo. No entanto, o planejamento dos riscos exige um suporte financeiro robusto e oportuno durante e após do desastre. Portanto, as ferramentas de transferência de risco, como os seguros, emergem como uma estratégia efetiva para garantir a resiliência financeira e como um elemento que poderia incentivar a implementação de mecanismos de redução do risco hidrológico. Entre os principais problemas no planejamento de seguros, estão a falta de informações sobre os impactos reais das secas e a incerteza climática, que podem levar a seleção adversa e/ou perigo moral como as problemáticas mais comuns na prática dos seguros. Atualmente, a maior parte da renda das empresas de serviços de água é baseada na gestão do recurso hídrico; portanto, durante períodos prolongados de seca, essas economias podem ser fortemente afetadas, apesar de ter sistemas de armazenamento robustos como suporte. Assim, esta tese propõe um plano de seguro para a empresa de serviços de água do Estado de São Paulo (SABESP), para enfrentar as reduções de receita durante longos períodos de seca. A metodologia é implementada no modelo MTRH-SHS, desenvolvido no cálculo \"ex-ante\" de custos de dano, através da abordagem baseada em risco. A abordagem sintética (\"what-if\"), usa um \"conjunto de drivers de mudança\" para estimar o prêmio ótimo através de um contrato de seguro plurianual (SPA). A metodologia integra os procedimentos de simulação hidrológica, sob cenários de forçamento climático radiativo RCP 4.5 e 8.5, do modelo de clima regional Eta-HadGEM e Eta-MIROC5, com horizontes temporais de 2007-2040, 2041-2070 e 2071-2099, vinculados ao modelo hidrológico do sistema de avaliação e planejamento da água (WEAP) e sob pressupostos de demanda como abastecimento de água estacionária e não estacionária. A estrutura do modelo é aplicada ao Sistema de Abastecimento de Água de Cantareira na Região Metropolitana de São Paulo, Brasil, região com alta vulnerabilidade às secas. Como resultado, os índices de rendimento do seguro avaliados mostraram que os contratos plurianuais com cobertura para secas superiores a 240 dias, oferecem melhor desempenho financeiro do que os contratos com coberturas mais amplas. Além, o SPA adotado para o risco residual do armazenamento instalado, gera um nível mais alto de solvência para o fundo de seguros no longo prazo com prêmios médios anuais mais próximos das reduções de receita esperadas por cenário. Finalmente, a abordagem pode ajudar na avaliação sistemática do risco moral e na seleção adversa. No primeiro caso, a avaliação progressiva deve gerar informações úteis para mudar ou manter o comportamento de segurados e seguradoras considerando riscos futuros relacionados à mudança climática. No segundo caso, a valoração de múltiplos cenários pode ajudar a estabelecer limiares de preços, oferecendo opções de cobertura diferencial de risco no valor prêmio de seguro.
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Powers, Alex D. "A Study of Constant Voltage Anemometry Frequency Response." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1570.
Повний текст джерелаАнотація:
The development of the constant voltage anemometer (CVA) for the boundary layer data system (BLDS) has been motivated by a need for the explicit autonomous measurement of velocity fluctuations in the boundary layer. The frequency response of a sensor operated by CVA has been studied analytically and experimentally. The thermal lag of the sensor is quantified by a time constant, MCVA. When the time constant is decreased, the half-amplitude cut-off frequency, fCVA, is increased, thereby decreasing the amount of attenuation during measurements. In this thesis, three main approaches have been outlined in theory and tested experimentally to determine the feasibility and effectiveness of implementing them with CVA to limit attenuation: operation at higher Vw, implementation of software compensation, and utilization of smaller diameter sensors. Operation of CVA at higher voltage results in little improvement in frequency response but is accompanied by increased danger of wire burnout. However, sensors do need to be operated at high wire voltages to be more sensitive to velocity fluctuations and less sensitive to temperature fluctuations, without reaching a temperature high enough for wire burnout. Software compensation of the CVA output has been shown not to be useful for measurements with BLDS. The electrical noise present in the CVA measurement system is amplified by the correction algorithm and creates measurements that are not representative of the fluctuations being measured. Decreasing sensor diameter leads to a significant decrease of MCVA and therefore increase of fCVA. Under similar operating conditions, a 2.5 micron diameter sensor showed less roll off in the frequency spectra (measured higher turbulence intensities) than a 3.8 micron diameter sensor for tests in both a turbulent jet and in a turbulent boundary layer. Smaller sensors are more fragile and have been shown to have a decrease in sensitivity as compared to larger sensors; however, for some applications, the increase in frequency response may be worth the trade-off with fragility and sensitivity.
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Allu, Pareekshith. "A Hybrid Ballistic-Diffusive Method to Solve the Frequency Dependent Boltzmann Transport Equation." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1451998769.
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