Dissertations / Theses: 'Sweep frequency'

1

Burt, Graeme C. "Sweep-frequency microwave pulse compression using a helically corrugated waveguide." Thesis, University of Strathclyde, 2004. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21549.

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A new type of pulse compressor based on sweep frequency pulse compression has been developed using a helically corrugated waveguide as a dispersive medium. This structure provides selective coupling between a TE₁₁ travelling wave and a near cut-off TE₂₁ wave, creating an eigenwave where the dispersion characteristics of one mode gradually converts into that of other. As the compressor works far from cut-off the reflections associated with operation close to cut-off are reduced and allows the compressor to be used at the output of a powerful amplifier. An experimental and theoretical study of swept-frequency based pulse compression as well as a theoretical and experimental investigation of the dispersive properties of a circular waveguide with a helical corrugation on its inner surface was carried out. Measurements of the helically corrugated compressor obtained a maximum optimum power compression ratio of 10.9 for a helically corrugated waveguide of length 208.08cm. A 1 kilowatt input pulse with a frequency sweep from 9.60GHz to 9.35GHz over 70ns was compressed by the helically corrugated waveguide. The compressed pulse had a duration of 3ns and gave a compression efficiency of 44%. The helical compressor experiments conducted were the first of their kind to be carried out and were found to be in good agreement with theory. A numerical study of the potential of the helically corrugated waveguide to produce multi-GW output pulses using frequency modulation at the falling edge of a microwave pulse produced from a high-power BWO was investigated.

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2

Pedholla, Prashanth Kumar. "Rheological and mechanical analysis of bituminous mixtures modified with recycled crumb rubber by wet technology." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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Road construction and maintenance is not only expensive, but it also has a huge impact on the environment. Being context sensitive in finding the material for the asphalt pavement with a superior quality have been always a challenge. The use of recycled material might be a good solution for reducing the overall impact of the road infrastructures. This report studied the effect of using crumb rubber in the asphalt mixture. The research was based on a practical experience of using crumb rubber modified mixture in Zola Predosa, Bologna (Italy). The mixtures were also having limestone filler as a modifier. Mastic(Binder-modifier system) and mortar (mastic-fine aggregate system) mixture having different quantities of crumb rubber and limestone filler modifiers have been tested in order to find the best rutting resistance combination with an acceptable stiffness. The rheological tests on bituminous mastics and mortars have done in the laboratories of University of Bologna. The results show that using fine crumb rubber reduces the thermo sensibility of the mastic (Binder Bitumen System) and improves its elasticity. Limestone filler in the other hand increases the mixture stiffness at high Frequencies.

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3

Slone, Rodney Daryl. "Fast frequency sweep model order reduction of polynomial matrix equations resulting from finite element discretizations /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu148645926752162.

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4

Kramer, Michael L. "Collinearity and Surround Size Effects on Spatial Discrimination Tasks." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1154716341.

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5

Chandrasekharan, Nair Vinod Chandran [Verfasser], and Martin [Akademischer Betreuer] Jansen. "Heteronuclear spin decoupling sequences with frequency sweep in solid-state NMR spectroscopy / Vinod Chandran Chandrasekharan Nair. Betreuer: Martin Jansen." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/1021343560/34.

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6

Bircan, Cavit. "Determination of protein denaturation and other conformational changes using the dielectric properties utilizing a frequency sweep at different temperatures /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486394475980442.

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7

Al-Tahir, Hibah. "Multidimensional Measurements : on RF Power Amplifiers." Thesis, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-729.

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In this thesis, a measurement system was set to perform comprehensive measurements on RF power amplifiers. Data obtained from the measurements is then processed mathematically to obtain three dimensional graphs of the basic parameters affected or generated by nonlinearities of the amplifier i.e. gain, efficiency and distortion. Using a class AB amplifier as the DUT, two sets of signals – both swept in power level and frequency - were generated to validate the method, a two-tone signal and a WCDMA signal. The three dimensional plot gives a thorough representation of the behavior of the amplifier in any arbitrary range of spectrum and input level. Sweet spots are consequently easy to detect and analyze. The measurement setup can also yield other three dimensional plots of variations of gain, efficiency or distortion versus frequencies and input levels. Moreover, the measurement tool can be used to plot traditional two dimensional plots such as, input versus gain, frequency versus efficiency etc, making the setup a practical tool for RF amplifiers designers.

The test signals were generated by computer then sent to a vector signal generator that generates the actual signals fed to the amplifier. The output of the amplifier is fed to a vector signal analyzer then collected by computer to be handled. MATLAB® was used throughout the entire process.

The distortion considered in the case of the two-tone signals is the third order intermodulation distortion (IM3) whereas Adjacent Channel Power Ratio (ACPR) was considered in the case of WCDMA.

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8

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&rsquo
s 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.

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9

Bowman, Denise Michelle. "Estimating mechanical frequency tuning properties of the cochlea with f¦1- and f¦2-sweep distortion-product otoacoustic emission measurements in normal hearing human adults." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0001/NQ34658.pdf.

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10

Calamelli, Filippo. "Studio reologico di mastici per miscele di conglomerato bituminoso drenante contenente polverino di gomma da pfu." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016.

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Le prestazioni meccaniche di una miscela di conglomerato bituminoso dipendono principalmente dai materiali che la compongono e dalla loro interazione. La risposta tenso-deformativa delle sovrastrutture stradali è strettamente legata al comportamento reologico del legante bituminoso e dalla sua interazione con lo scheletro litico. In particolare nelle pavimentazioni drenanti, a causa dell’elevato contenuto di vuoti, il legame che si crea tra il legante (mastice bituminoso) e l’aggregato è molto forte, per questo motivo è importante migliorarne le prestazioni. Additivando il mastice con polverino di gomma da PFU (pneumatici fuori uso), non solo si migliorano prestazioni, resistenza alle deformazioni permanenti ed elastoplasticità del materiale, ma si sfruttano anche materiali di recupero, portando vantaggi anche dal punto di vista ambientale. In quest’ottica la ricerca effettuata nella tesi si pone come obiettivo l’analisi reologica e lo studio di mastici additivati con polverino di gomma ricavato da PFU, per la realizzazione di conglomerati bituminosi drenanti. In particolare, partendo da un bitume di base, sono stati preparati due mastici: il primo ottenuto miscelando bitume modificato e filler calcareo, il secondo aggiungendo al precedente anche il polverino di gomma. Tale studio è stato eseguito mediante l’utilizzo del DSR (Dynamic Shear Rheometer – UNI EN 14770), con il quale sono state affrontate tre prove: Amplitude Sweep test, per la valutazione del valore di deformazione di taglio γ entro il quale il materiale si mantiene all’interno del campo di viscoelasticità lineare (Linear visco-elasticity, LVE); Frequency Sweep test, per l’estrapolazione delle master curves; Multiple stress Creep Recovery, per valutare la resistenza del materiale alle deformazioni permanenti. Dall’analisi dei dati è stato possibile definire il comportamento reologico di entrambi i mastici e, in seconda analisi, confrontarne le caratteristiche e le prestazioni.

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11

Singh, Gurjashan. "Health Monitoring of Round Objects using Multiple Structural Health Monitoring Techniques." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/330.

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Structural Health Monitoring (SHM) techniques are widely used in a number of Non – destructive Evaluation (NDE) applications. There is a need to develop effective techniques for SHM, so that the safety and integrity of the structures can be improved. Two most widely used SHM methods for plates and rods use either the spectrum of the impedances or monitor the propagation of lamb waves. Piezoelectric wafer – active sensors (PWAS) were used for excitation and sensing. In this study, surface response to excitation (SuRE) and Lamb wave propagation was monitored to estimate the integrity of the round objects including the pipes, tubes and cutting tools. SuRE obtained the frequency response by applying sweep sine wave to surface. The envelope of the received signal was used to detect the arrival of lamb waves to the sensor. Both approaches detect the structural defects of the pipes and tubes and the wear of the cutting tool.

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Haller, Kristian. "Nonlinear Acoustics Applied to NonDestructive Testing." Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00374.

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Sensitive nonlinear acoustic methods are suitable for material characterization. This thesis describes three nonlinear acoustic methods that are proven useful for detection of defects like cracks and delaminations in solids. They offer the possibility to use relatively low frequencies which is advantageous because attenuation and diffraction effects are smaller for low frequencies. Therefore large and multi-layered complete objects can be investigated in about one second. Sometimes the position of the damage is required. But it is in general difficult to limit the geometrical extent of low-frequency acoustic waves. A technique is presented that constrains the wave field to a localized trapped mode so that damage can be located.

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13

Eriksson, Anna, Viktoria Andersson, Katrin Berezniak, Markus Hall, Victor Håkanson, and Ida Biörs. "Reologi på gelberedningar." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-297837.

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Konsistensen på en gel bestående av tvärbunden hyaluronsyra beror av tre faktorer: total koncentration hyaluronsyra, gelningsgrad och tvärbindningsdensitet. För att utföra detta projekt erhölls tre olika geler med olika tvärbindningsdensitet. Dessa geler späddes dels med lösning av fri, icke tvärbunden, HA från 100 % gelningsgrad till 90 % och 80 %. De olika gelningsgraderna späddes också med natriumkloridlösning från den totala koncentrationen HA, 35 mg HA/g gel, till 25 mg/g och 15 mg/g. Projekts huvudfråga är att kartlägga gelens reologiska egenkaper då både total koncentration HA och gelningsgrad varieras. För att kunna kartlägga detta har en reometer brukats där följande tre tester körts: tidssvep, frekvenssvep och amplitudsvep. Från erhållen data har sedan två parametrar som representerar gelkompositionernas viskösa egenskaper (G'') och elastiska egenskaper (G') observerats. Även mätning av extruderingskraft har genomförts för att dra vidare paralleller och slutsatser mellan extruderingskraften och de reoligiska egenskaperna. Ur resultaten ses att förlusttangenten tenderar att sjunka när gelningsgraden ökar, d.v.s. gelerna blir då mer viskösa och mindre elastiska. Förlusttangenten sjunker även vid ökande total koncentration HA vilket betyder att G’ ökar mer än G’’ i vardera punkt som gör att förlusttangenten minskar.Det gick även att avläsa att de viskösa egenskaperna i gelen ökar då total koncentration hyaluronsyra minskar samt att de viskösa egenskaperna i gelerna minskar vid en sjunkande gelningsgrad. Mellan gelningsgrad 90-100 % och total koncentration HA 25-35 mg HA/g har analyserna som gjorts i detta projekt gett följande slutsatser. Konsistensen på gel A och C är mer påverkade av gelningsgraden än total koncentration HA. För gel B kan ingen dominerande parameter utläsas.
The softness of a gel made of crosslinked HA (HA = hyaluronic acid) depends onthree factors. One is the amount of free hyaluronic acid in the gel. Another is thedensity of the crosslinked network, which is the molecular entanglements in the gel.The third is the total concentration of HA. In this project a rheometer is used to measure the rheological properties by runningthe following tests: time sweep, frequency sweep and amplitude sweep. From theobtained data, parameters related to viscous properties (G’’) and elastic properties(G’) of the gels were observed. 27 different compositions of gels with three differentconcentrations (35 mg HA/g, 25 mg HA/g, 15 mg HA/g), three different gel contents(100%, 90%, 80%) and three different densities of crosslinked network (A, B, C) wereanalyzed. To draw further conclusions an analysis of extrusion force was performedas well. The results from the frequency sweeps show that the loss tangent for a gel increasedas the total concentration of HA was reduced and that the loss tangent for a gelincreased as the gel content was decreased. This indicates that the gels become moreviscous when either the concentration of HA or the gel content was decreased. Anincrease in concentration of HA results in an increase of G' and an increase of gelcontent also results in an increase of G'. The results from the amplitude sweeps showthat xG' (xG' = storage modulus at the crossover point between G' and G'') increasesas either the concentration of HA or the gel content is increased. For xStrain (xStrain= deformation of the gel at the crossover point) and xStress (xStress = the stressapplied to the gel at the crossover point) no clear trend can be seen regarding the gelcontent. But an increase in concentration of HA results in an increase of both xStrainand xStress. The results from the analysis of extrusion force show that an increase intotal concentration HA increases the force.

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14

Mattila, T. (Tiina). "Post-glacial colonization, demographic history, and selection in Arabidopsis lyrata:genome-wide and candidate gene based approach." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526217093.

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Abstract Demographic history and natural selection are central forces shaping the genetic diversity of populations. Knowledge on these forces increases understanding of processes shaping genetic variability of populations. In this PhD thesis I investigated demographic history and selection in multiple populations of Arabidopsis lyrata, an outcrossing herbaceous plant species of the Brassicaceae family. Due to its wide distribution in the temperate and boreal regions, A. lyrata serves as a good model system to study population genetic consequences of colonization of northern latitudes. The first aim of this study was to characterize the demographic and colonization history of the species using site frequency spectra estimated from whole-genome diversity data. Another aim was to detect genetic loci targeted by recent selective sweeps at genome-wide scale as well as at candidate flowering time genes. Patterns of genome-wide selection at linked sites (linked selection) were also compared between populations of Capsella grandiflora and A. lyrata with contrasting demographic histories. Evidence for strong effective population size decline in the past few hundred thousand years was detected in A. lyrata populations species-wide. This study also suggests recent Scandinavian colonization from an unknown refugium, distinct from the Central European source population. Selection analyses revealed loci targeted by positive selection in two Scandinavian lineages after the recent population split as well as selective sweeps in flowering time genes in the colonizing populations. In comparison with the studied C. grandiflora population, the Norwegian A. lyrata population had weaker purifying selection and no evidence for reduction of diversity around genes was found. This thesis offers novel information on species colonization history and its genome-wide effects, which is important for understanding the framework of local adaptation
Tiivistelmä Populaation demografinen historia ja luonnonvalinta ovat keskeisiä populaation perinnöllisen muuntelun muokkaajia. Näiden tekijöiden tutkimus on tärkeää eliöiden sopeutumisen ymmärtämiselle. Tässä väitöskirjassa tutkin demografista historiaa ja valintaa monivuotisen ristisiittoiseen ruohovartisen Brassicaceae-heimon kasvilajin idänpitkäpalon (Arabidopsis lyrata) useissa eri populaatioissa. Idänpitkäpalko on erinomainen mallilaji pohjoiseen ympäristöön sopeutumisen tutkimukseen, koska sen toisistaan eristäytyneet paikalliset populaatiot ovat levittäytyneet laajalle boreaalisella ja lauhkealla ilmastovyöhykkeellä. Tutkimuksen tarkoituksena oli luonnehtia populaatioiden demografista historiaa ja kolonisaatioreittejä käyttäen koko perimän laajuisesta muunteluaineistosta estimoituja alleelifrekvenssispektrejä. Lisäksi koko perimän laajuista aineistoa sekä kukkimisaikaa ohjaavien geenien sekvenssejä käytettiin positiivisen luonnonvalinnan merkkien tunnistukseen. Genominlaajuista kytkeytynyttä valintaa vertailtiin toiseen ristisiittoiseen Brassicaceae-heimon lajin Capsella grandifloran populaatioon, jonka demografinen historia poikkeaa huomattavasti tutkituista idänpitkäpalon populaatioista. Tutkimuksessa havaittiin, että kaikissa tutkituissa idänpitkäpalon populaatioissa tehollinen populaatiokoko oli pienentynyt viimeisen muutaman sadantuhannen vuoden aikana. Kolonisaatiohistorian tarkastelu osoitti, että idänpitkäpalon skandinaaviset populaatiot ovat todennäköisesti peräisin keskieurooppalaisesta refugiosta erillisestä läntisestä refugiosta. Skandinavian kolonisaation yhteydessä vaikuttaneen positiivisen luonnonvalinnan merkkejä havaittiin useissa eri genomin osissa sekä erityisesti valojaksoa mittaavissa geeneissä. Tämä kertoo erilaisiin valojaksoihin sopeutumisen tärkeydestä skandinaavisen kolonisaation yhteydessä. Verrattuna tutkittuun C. grandifloran populaatioon, idänpitkäpalolla puhdistavan valinnan havaittiin olevan heikompaa ja muuntelun vähenemistä geenien ympärillä ei havaittu. Tämä tutkimus tarjoaa uutta tietoa Skandinavian kolonisaatiohistoriasta ja sen genominlaajuisista vaikutuksista. Tutkimuksessa tuotettua tietoa voidaan hyödyntää paikallisen sopeutumisen ymmärtämisessä

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Kurt, Sinan. "Range Resolution Improvement Of Fmcw Radars." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608808/index.pdf.

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Frequency Modulated Continuous Wave (FMCW) radar has wide application areas in both civil and military use. The range resolution is a critical concept for these FMCW radars as for the other radar types. There are theoretical restrictions in the range resolution. In addition, the non-ideal properties of the modules used in the systems negatively affects the range resolution. The transmitter leakage, non-linear frequency sweep, FM to AM distortion and measurement errors are some of the critical non-ideal properties. The problems arising from these non-ideal properties further restrict the range resolution of FMCW radars. Another important concept for the range resolution that can be obtained from FMCW radars is the signal processing method. This thesis deals with the non-ideal properties of the system modules and techniques to reduce their effects on the range resolution. Furthermore, the signal processing methods used for FMCW radar signals and the possible improvement techniques for these methods are discussed. Moreover, a simple signal processing unit called zero crossing counter which can be used for short range FMCW radars is implemented and range resolution performance of this zero crossing counter is investigated by carrying out measurements on a prototype FMCW radar at 2200MHz.

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16

McKinnon, Douglas John Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Novel efficiency evaluation methods and analysis for three-phase induction machines." Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 2005. http://handle.unsw.edu.au/1959.4/21869.

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This thesis describes new methods of evaluating the efficiency of three-phase induction machines using synthetic loading. Synthetic loading causes the induction machine to draw full-load current without the need to connect a mechanical load to the machine's drive shaft. The synthetic loading methods cause the machine to periodically accelerate and decelerate, producing an alternating motor-generator action. This action causes the machine, on average over each synthetic loading cycle, to operate at rated rms current, rated rms voltage and full-load speed, thereby producing rated copper losses, iron loss and friction and windage loss. The excitation voltages are supplied from a PWM inverter with a large capacity DC bus capable of supplying rated rms voltage. The synthetic loading methods of efficiency evaluation are verified in terms of the individual losses in the machine by using a new dynamic model that accounts for iron loss and all parameter variations. The losses are compared with the steady-state loss distribution determined using very accurate induction machine parameters. The parameters were identified using a run-up-to-speed test at rated voltage and the locked rotor and synchronous speed tests conducted with a variable voltage supply. The latter tests were used to synthesise the variations in stator leakage reactance, magnetising reactance and the equivalent iron loss resistance over the induction machine's speed range. The run-up-to-speed test was used to determine the rotor resistance and leakage reactance variations over the same speed range. The test method results showed for the first time that the rotor leakage reactance varied in the same manner as the stator leakage and magnetising reactances with respect to current. When all parameter variations are taken into account there is good agreement between theoretical and measured results for the synthetic loading methods. The synthetic loading methods are applied to three-phase induction machines with both single- and double-cage rotors to assess the effect of rotor parameter variations in the method. Various excitation waveforms for each method were used and the measured and modelled efficiencies compared to conventional efficiency test results. The results verify that it is possible to accurately evaluate the efficiency of three-phase induction machines using synthetic loading.

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Hall, David. "Tracing selection and adaptation along an environmental gradient in Populus tremula." Doctoral thesis, Umeå : Institutionen för Ekologi, miljö och geovetenskap, Umeå universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30123.

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Colaux, Henri. "Investigating sensitivity improvement methods for quadrupolar nuclei in solid-state nuclear magnetic resonance." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/9628.

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The study of quadrupolar nuclei using NMR spectroscopy in the solid state significantly increased in popularity from the end of the 20th century, with the introduction of specific methods to acquire spectra free from the effects of the quadrupolar interaction, that results in broadened lineshapes that cannot be completely removed by spinning the sample at the magic angle (MAS), unlike most of the other interactions present in the solid state. The first technique which allows, without any specific hardware, the removal of this broadening has been the Multiple-Quantum MQMAS experiment. The method quickly gained a popularity within the NMR community, with numerous successful applications published. However, the multiple-quantum filtration step in this experiment relies on severely limits sensitivity, restricting application to the most sensitive nuclei. Extending the applicability of MQMAS to less receptive nuclei requires the use of signal improvement techniques. There are multiple examples of such approaches in the literature, but most of these require additional optimisation that may be time-consuming, or simply impossible, on less receptive nuclei. This work introduces a novel signal improvement technique for MQMAS, called FAM-N. Its optimisation is solely based on density matrix simulations using SIMPSON, implying no additional experimental optimisation is required, while improving the signal in MQMAS spectra by equivalent or higher amounts than other common methods. In order to prove the applicability of this method on virtually any system, FAM-N has been investigated by simulation, and tested experimentally using a number of model samples, as well as samples known to be challenging to study by NMR. This work also explores other aspects of NMR spectroscopy on quadrupolar nuclei. Adiabatic inversion of the satellite populations can be performed to improve the central transition signal in static or MAS spectra. A range of methods has been tested and compared, with particular attention given to hyperbolic secant-shaped pulses, for which its performance have been described. Finally, cross-polarisation from a spin I = 1/2 nucleus to a quadrupolar nucleus has been investigated. After reviewing the theory for the static case, simulations have been performed under MAS in order to identify the conditions for efficient magnetisation transfer, with applications in spectral editing or for the combination with MQMAS.

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Davis, Abbie M. "BINAURAL INTERACTION OF EXPERIENCE-DEPENDENT BRAINSTEM RESPONSES TO FREQUENCY SWEEPS IN NORMAL-HEARING CHINESE ADULTS." Ohio University Honors Tutorial College / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1366978237.

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Lee, Hyo Jin. "The effects of aging on temporal processing in the rat inferior colliculus, responses to frequency-modulated sweeps." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63226.pdf.

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Saravanakumar, A. "Terminal Connection And System Function For Making Sweep Frequency Response Measurements On Transformers." Thesis, 2008. http://hdl.handle.net/2005/739.

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Sweep Frequency Response (SFR) measurement on a transformer is a low voltage, offline exercise. So, it virtually permits determination of any network or system function, by imposing any desired terminal condition for the nontested windings and terminals. The terminal conditions employed have significant influence on the achievable fault detection ability, and maximizing this ability should obviously be one of the main aims of frequency response measurements. Simply stated, this requirement translates to the ability to identify/measure as many natural frequencies as possible. However, there is a practical limitation that not all system functions can exhibit all natural frequencies. Hence, it is necessary to determine the most appropriate combination of terminal connection and system function for achieving this objective. The growing popularity of SFR measurements has led to a new IEEE Guide. This document (IEEE Std PC57.149TM/D1) on SFR measurement lists out most of the possible terminal connections and system functions, for both 1φ and 3φ transformers. Surprisingly, it does not identify and recommend any one of them as preferred for maximizing this objective. Initially, considering the high frequency equivalent circuit representation of a 1φ, twowinding transformer, system function for different terminal conditions were computed. Depending on the number of natural frequencies distinguishable in the amplitude frequency response of a system function, each measuring condition was ranked. Thus, it led to identification of the best configuration. Later, these findings were verified on an actual 1φ, two-winding transformer. However, 3φ transformers are quite different in construction compared to 1φ transformers. So, whether the same configuration would also be applicable for SFR measurements on 3φ transformers had to be ascertained. So, the study was next extended to 3φ transformers. Performance of best configuration identified during this investigation are compared with currently employed low-voltage impulse test (used during short-circuit testing of transformers) and currently practiced SFR measurement test conditions, and found to be better. In conclusion, it is believed that after adequate field verifications, the identified configuration can be declared as the preferred way of making SFR measurement on transformers.

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Yeh, Wan-ting, and 葉菀婷. "Detection of Frequency-Modulated Sweep Direction by English and Chinese Speakers: An ERP Study." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/18662972010914917507.

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碩士
國立中央大學
認知與神經科學研究所
101
調頻 (frequency modulation)是構成複雜溝通訊號的基本聽覺元素，舉凡人類語言、音樂至同物種發聲。調頻掃描(frequency-modulated sweeps)是調頻中重要的類別之一，可提供語言編碼(speech encoding)與詞匯特徵(lexicon distinction)等重要線索，此線索以語調語言(tonal language)尤為明顯。本實驗致力於偵測調頻掃描訊號處理中的聽覺敏感度與語言經驗，並執行心理物理學與事件相關腦電位實驗。實驗一，利用非配對誘發電位成分(mismatch negativity component)探討分辨線性頻率掃描訊號方向之神經基質。實驗二，利用非配對誘發電位成分與行為分辨(discrimination)實驗，探討變化複合頻率掃描訊號的方向、頻寬與速率之敏感度。實驗三，母語為中文及英文受試者參與聽覺閾限追蹤實驗，此實驗目的為檢測語言經驗影響基礎調頻處理程度。行為實驗顯示，中文為母語受試者擁有較準確的辨別能力於第一共振峰的頻間(600-900Hz)，且不受刺激長短影響(30, 100 及300毫秒)均有出色的辨別能力；但在基頻頻間(180-270Hz)，只有較長的刺激(100及300毫秒)表現較好。事件相關腦電位實驗顯示，中文為母語的受試者，在不受注意力介入的情況下，僅在較長(100及300毫秒)的下行訊號之條件，仍可辨認頻率掃描訊號及複合頻率掃描訊號之方向。非配對誘發電位成分的振幅在較長的訊號與第一共振峰的頻率區間較大，代表偵測能力較好。聽覺閾限追蹤實驗(auditory threshold tracking)顯示中文受試者分辨頻率掃描訊號的能力比英文受試者更好，隱含著複合調頻訊號之敏感度會隨語言經驗而不同。研究結果顯示語言經驗會影響非語言知覺性聽覺訊號處理，如調頻掃描訊號。

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23

ChangTsao-Kai and 張朝凱. "An Approach to FPGA-based Time-Frequency Spectrogram by Real-Time Sweep Spectral Extraction Algorithm." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/56001183905681831310.

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碩士
崑山科技大學
電子工程研究所
94
We have proposed an approach to build up an FPGA-based time-frequency spectrogram for time-varying signal. Instead of short time-interval FFT algorithm, we have adopted real-time sweep spectral extraction algorithm to reduce large memory usage. By fixing the sweep frequency range of local oscillator and the center frequency of Finite Impulse Response (FIR) filter, we can obtain more effective usage of FPGA hardware resource and stable spectrum analysis performance. The time-frequency scaling algorithm has been used to guarantee the measurement of wide frequency range (sub-Hz to MHz) for arbitrary input time-varying signal. The high speed FPGA performance enables us to build up a three dimension time-frequency spectrogram for audio signal by accumulating the spectral data against the evolution time.

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24

Brown, Trecia. "Development of Neuronal Responses to Frequency-modulated Tones in Chinchilla Auditory Cortex." Thesis, 2010. http://hdl.handle.net/1807/24695.

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A central issue in auditory research is how the auditory brain encodes complex stimuli. However, the process by which the auditory cortex interprets complex sounds during development and the extent to which cortical organization can be manipulated by complex stimulation is still undetermined. We have addressed this gap in the following three studies. First, we characterized the responses of cortical neurons in adult chinchillas to frequency-modulated (FM) stimulation. Next, we asked whether FM coding at the cortical level is innate or if its development is influenced by normal postnatal environmental experience. Finally, we investigated the effect of sustained neonatal FM sweep exposure on the development of cortical responses to tonal and FM stimuli. In our adult study, results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds ( 0.3 kHz/ms). Three types of temporal response patterns were observed: a single peak at sweep onset/offset (‘onset’) and a single peak (‘late’) or multiple peaks (‘burst’) during the sweep. ‘Late’ units expressed the highest direction and speed selectivity; ‘onset’ units were selective only for direction and ‘burst’ units were selective for neither direction nor speed. In our developmental study, our results showed a significant developmental increase in FM direction selectivity. However, FM speed selectivity appeared to be established early in development. In our developmental plasticity study, we hypothesized that constant FM exposure would increase the proportion of auditory neurons that are selectively responsive to the conditioning FM sweep. However, our results showed that while tonal response latencies increased after the exposure period, the conditioning stimulus had minimal effect on the FM direction preferences of cortical neurons and decreased overall neuronal FM speed selectivity. In conclusion, we suggest that chinchilla auditory cortical neurons are not uniquely activated by FM sounds but that FM responses are largely predictable based on how changing frequency stimuli interact with the receptive fields of these neurons. We also propose that the development of FM direction sensitivity is experience-independent and that perhaps normal acoustic experience is required to maintain FM speed tuning.

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Dissertations / Theses on the topic 'Sweep frequency'

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