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Dissertations / Theses on the topic 'THz frequency range'
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1
Thoma, Petra [Verfasser]. "Ultra-fast YBa2Cu3O7-x direct detectors for the THz frequency range / Petra Thoma." Karlsruhe : KIT Scientific Publishing, 2013. http://www.ksp.kit.edu.
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Sung, Chieh. "Interaction of a relativistic electron beam with radiation in the THz frequency range." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1679290761&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Beneš, Adam. "Plazmonické antény pro vysoké vlnové délky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443226.
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Tato diplomová práce se zabývá vlastnostmi plazmonických antén v oblasti vysokých vlnových délek. Důraz je kladen na popis rezonančních vlastností jednotlivých antén i antén uspořádaných do periodických polí. Těžiště práce spočívá v počítačovém modelování navýšení magnetického pole v blízkosti antén, které lze využít ve vysokofrekvenční elektronové paramagnetické rezonanci (HFEPR) k zesílení měřeného signálu. Autor se zabývá kvantifikací zesílení v anténách s odlišnou geometrií a navrhuje i geometrii vlastní. Značná část práce se také věnuje snaze rozlišit příspěvky k navýšení magnetického pole od různých zdrojů při měření HFEPR v uspořádání s dvojitou transmisí záření.
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Morgan, Matthew James. "Extending the tuning range of electrostatic actuators." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11016.
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Blom, Peter. "Magneto-sensitive rubber in the audible frequency range." Doctoral thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4024.
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Herron, David. "Vibration of railway bridges in the audible frequency range." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/151141/.
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The noise level associated with a train travelling on a bridge is normally greater than that for a train travelling on plain track. It is sometimes the bridge noise that causes the highest levels of disturbance to people in the vicinity or triggers action under regulations such as the Environmental Noise Directive. Consequently, there is a need to study means of predicting noise levels from proposed bridges, noise control measures for existing structures and principles of low-noise bridge design. This thesis describes a programme of work in which an existing calculation model for bridge noise and vibration has been tested and alternative calculation methods have been developed where required. The existing model is based on analytical models for wheel-rail interaction and the calculation of the power input to the bridge. The response of the various component parts of the bridge for this power input is found using a simplified SEA scheme. In this work, the existing model has been tested against measurements made on railway bridges and the results of an advanced method of structural analysis, the Waveguide Finite Element (WFE) method. This method is well-suited to modelling some important types of railway bridge. Specifically, it allows a numerical modelling approach to be used up to higher frequency than conventional Finite Element methods. It has been found to offer some significant advantages over the existing bridge noise model, particularly for concrete-steel composite bridges and concrete box-section viaducts. The track support structure has an important influence on bridge noise and vibration, through its role in the transmission of vibration from the rail to the bridge. Laboratory measurements have been made in this work to characterise the vibration transmission properties of two important types of track support structure on bridges; ballasted track and two-stage resilient baseplate track. Improved methods of modelling the dynamic behaviour of these track forms have been developed from the measurements, which can be used in calculation models for both bridge noise and also for rolling noise.
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Hoefener, Carl E., and James Stone. "THE ADVANTAGES OF APPLYING GPS FREQUENCY TRANSLATORS TO RANGE TRACKING." International Foundation for Telemetering, 1985. http://hdl.handle.net/10150/615741.
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International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, NevadaWhen applying the Global Positioning System (GPS) to Time, Space, and Position Information (TSPI), the use of GPS frequency translators should be considered. The primary space positioning problem in the test and evaluation applications is trajectory reconstruction. Although this can be accomplished by flying a GPS receiver on the test vehicle and telemetering its position to the ground, there are significant advantages to translating the “L” band GPS signals to “S” band, and transmitting the broad band signal to the ground for processing. A translator-based system offers several advantages. Physical advantages include smaller size, lower weight, and lower cost. Technical advantages include: 1) ground station data aiding that provides a 6 dB advantage, 2) elimination of system bias errors, 3) computation complexity at the ground station vs. the vehicle under test, and 4) the ability to reconstruct a test scenario enabling flexibility in data analysis techniques.
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Paik, Steve Sunghwan 1974. "The design and implementation of a new wide-range frequency detector." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9471.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 65).
In this thesis, I designed and implemented a wide range frequency detector for use in clock recovery and data retiming applications. The new detector works in conjunction with the existing "mid-range" frequency detector to accurately lock the VCO to the incoming data rate. The new detector consists of two halves: one to detect when the VCO is too fast, and one to detect when the VCO is too slow. The design and analysis of the new frequency detectors, in addition to a method for integrating it with the existing detector, is discussed. Simulation data of the new and original frequency detectors are used to support the concepts upon which the new detector is designed. Some topics for future work are suggested at the end of this thesis.
by Steve Sunghwan Paik.
M.Eng.
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Green, Sean David. "Improving the range information of high frequency over-the-horizon skywave radar." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268265.
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Mackall, Dale A., Robert Sakahara, and Steven E. Kremer. "THE X-33 EXTENDED FLIGHT TEST RANGE." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/609678.
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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaDevelopment of an extended test range, with range instrumentation providing continuous vehicle communications, is required to flight-test the X-33, a scaled version of a reusable launch vehicle. The extended test range provides vehicle communications coverage from California to landing at Montana or Utah. This paper provides an overview of the approaches used to meet X-33 program requirements, including using multiple ground stations, and methods to reduce problems caused by reentry plasma radio frequency blackout. The advances used to develop the extended test range show other hypersonic and access-to-space programs can benefit from the development of the extended test range.
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Jenkins, Ruth Ann. "The Affects of Vocal Fatigue on Fundamental Frequency and Frequency Range in Actresses as Opposed to Non-Actresses." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5062.
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Differences may exist between the voice qualities of those who professionally use and train their voices and those who do not. The examination of fundamental frequency and frequency range m actresses and non-actresses is integral to determining voice quality differences in these populations. These differences, whether the result of frequent use or training of the voice, may exist relative to fatiguing conditions such as may be experienced by actresses in the course of their work. Fatigue has been shown to produce greater effects in normals than in performers, particularly in singers (Gelfer, Andrews, and Schmidt, 1991). Little research has been found comparing actresses to non-actresses in such an interaction effect. In order to determine whether a separate set of normative values should be sought for actresses, it is first necessary to determine whether significant differences exist between these populations in voice quality parameters. The purpose of the present study was to determine whether or not significant changes in fundamental frequency and frequency range occurred in non-actresses relative to actresses as a result of fatigue. The subjects for the study included ten actresses between the ages of 20 and 30 who had a minimum of one quarter of voice training and three years of acting experience and ten women of the same age group who had no voice training or experience in acting. Each subject passed a puretone audiometric screening, had a negative history of voice disorders, and had not smoked within the last year. These two groups were evaluated for: 1) fundamental frequency in prolonged productions of the vowel lal; 2) speaking fundamental frequency in connected speech; 3) frequency range in sung scales; and 4) frequency range in connected speech. Data was statistically analyzed using one way ANOV A tests with repeated measures. No significant interactions occurred between group and time, suggesting that non-actresses did not produce a greater shift than did actresses in fundamental frequency or frequency range as a result of fatigue. These results contradicted some findings and supported other findings of previous research based on similar samples.
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Porter, Nathan Edward. "Spectroscopic studies of quantum dot intersublevel transitions in the few terahertz frequency range." Thesis, University of Sheffield, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577683.
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This thesis presents intraband optical studies of self-assembled quantum dots (QDs) in the few terahertz (THz) range and optical THz frequency mixing in the same samples. Magneto-transmission measurements of QDs in the few-terahertz range are described. The polaronic nature of the excitations of the system was studied by tracking the intraband transition energy as a function of magnetic field up to 28T. The first direct measurement of anticrossings in the I-LO phonon energy range are reported and evidence of polarons consisting of an electron bound with an InAs-like optical phonon in addition to phonon-like polarons is presented. Degenerate pump-probe spectroscopy was used to study intraband energy relaxation for transition energies below the LO phonon energy. Post-growth annealing was used to reduce the energy level separation of the samples to below the typical as-grown transition energy of 40 - 60me V. It was observed that as the intraband transition energy reduced, the relaxation times increased, exhibiting very strong energy dependence. It was found that at an energy of ~ 30meV (7THz) the relaxation times were of the order of 2ps, whilst at an energy of ~ 14meV (3.4THz) the relaxation times increased to 1.5ns. These results were explained using a microscopic polaron relaxation model (developed by colleagues at the ENS, Paris), in which decay occurs via phonon anharmonicity, with very good agreement found between experiment and theory. Optical sideband generation via frequency mixing of a near infrared (NIR) laser beam and a THz beam using interband and intraband resonances in QDs is described.
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Shroyer, Kathryn E. "Variation of French horn timbre over the frequency and intensity range of the instrument." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54498.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 36).
Timbre describes the perceptual difference between sounds with the same loudness and pitch generated from different sources such as different instruments. Each instrument has its own unique timbre making it distinguishable. Within each instrument however, this timbre changes slightly with respect to frequency and intensity of sound. This is perceived qualitatively by the use of words such as "bright", "mellow", "harsh" and many others to describe sounds of different intensity or frequency in a given instrument. However, this is only a subjective view and does not describe what changes in the acoustic properties produce these different timbres. This study quantitatively examined the change in timbre over the frequency and intensity range of the French horn. Two main acoustical properties were measured: number of frequency partials and shape of the spectral envelope, where "partials" refers to harmonics of the fundamental frequency. The parameter represented by the number of partials includes both the total number of partials as well as the number of partials with critical band overlap. The shape of the spectral envelope was characterized through its center frequency and width of the major peaks as well as the strength of the fundamental frequency. Each of these parameters was related to qualitative timbre descriptions such as "fullness" or "roughness". The results showed a significant change in timbre over the frequency and intensity range of the French horn. The extremes of French horn span from timbre that is "thin" and "smooth" to "rich" and "rough". Within this spectrum, low frequency notes and high intensity sounds lie at one end exhibiting "rich" and "rough" timbre. The high frequency and low intensity sounds lie at the other extreme exhibiting "thin" and "smooth" timbre. As frequency increases and intensity decreases the number of partials decreases and the spectral contour shifts from wide and flat to a strong narrow peak. This produces a timbre shift from sounds that seem "rough" and "rich" to those that seem "smooth" and "thin".
by Kathryn E. Shroyer.
S.B.
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Hotchkiss, John. "A psychophysical investigation of audio-visual timing in the millisecond range." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5771.
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The experiments described in this thesis use psychophysical techniques and human observers to investigate temporal processing in the millisecond range. The thesis contains five main sections. Introductory chapters provide a brief overview of the visual and auditory systems, before detailing our current understanding of duration processing. During the course of this review, several important questions are highlighted. The experiments detailed in Chapters 8-11 seek to address these questions using the psychophysical techniques outlined in Chapter 7. The results of these experiments increase our understanding of duration perception in several areas. Firstly, Experiments 1 and 2 (Chapter 8) highlight the role of low level stimulus features: even when equated for visibility stimuli of differing spatial frequency have different perceived durations. Secondly, a psychophysical hypothesis arising from the 'duration channels' or 'labelled lines' model of duration perception is given strong support by the adaptation experiments detailed in Chapter 9 and 10. Specifically, adaptation to durations of a fixed temporal extent induces repulsive duration aftereffects that are sensory specific and bandwidth limited around the adapted duration. Finally Chapter 11 describes the results of experiments designed to probe the processing hierarchy within duration perception by measuring the interdependency of illusions generated via duration adaptation and via multisensory cue combination. The results of these experiments demonstrate that duration adaptation is a relatively early component of temporal processing and is likely to be sub served by duration selective neurons situated in early sections of the visual and auditory systems.
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Chronopoulos, Dimitrios. "Prediction of the vibroacoustic response of aerospace composite structures in a broadband frequency range." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00787864.
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During its mission, a launch vehicle is subject to broadband, severe, aeroacoustic and structure-borne excitations of various provenances, which can endanger the survivability of the payload and the vehicles electronic equipment, and consequently the success of the mission. Aerospace structures are generally characterized by the use of exotic composite materials of various configurations and thicknesses, as well as by their extensively complex geometries and connections between different subsystems. It is therefore of crucial importance for the modern aerospace industry, the development of analytical and numerical tools that can accurately predict the vibroacoustic response of large, composite structures of various geometries and subject to a combination of aeroacoustic excitations. Recently, a lot of research has been conducted on the modelling of wave propagation characteristics within composite structures. In this study, the Wave Finite Element Method (WFEM) is used in order to predict the wave dispersion characteristics within orthotropic composite structures of various geometries, namely flat panels, singly curved panels, doubly curved panels and cylindrical shells. These characteristics are initially used for predicting the modal density and the coupling loss factor of the structures connected to the acoustic medium. Subsequently the broad-band Transmission Loss (TL) of the modelled structures within a Statistical Energy Analysis (SEA) wave-context approach is calculated. Mainly due to the extensive geometric complexity of structures, the use of Finite Element(FE) modelling within the aerospace industry is frequently inevitable. The use of such models is limited mainly because of the large computation time demanded even for calculations in the low frequency range. During the last years, a lot of researchers focus on the model reduction of large FE models, in order to make their application feasible. In this study, the Second Order ARnoldi (SOAR) reduction approach is adopted, in order to minimize the computation time for a fully coupled composite structural-acoustic system, while at the same time retaining a satisfactory accuracy of the prediction in a broadband sense. The system is modelled under various aeroacoustic excitations, namely a diffused acoustic field and a Turbulent Boundary Layer (TBL) excitation. Experimental validation of the developed tools is conducted on a set of orthotropic sandwich composite structures. Initially, the wave propagation characteristics of a flat panel are measured and the experimental results are compared to the WFEM predictions. The later are used in order to formulate an Equivalent Single Layer (ESL) approach for the modelling of the spatial response of the panel within a dynamic stiffness matrix approach. The effect of the temperature of the structure as well as of the acoustic medium on the vibroacoustic response of the system is examined and analyzed. Subsequently, a model of the SYLDA structure, also made of an orthotropic sandwich material, is tested mainly in order to investigate the coupling nature between its various subsystems. The developed ESL modelling is used for an efficient calculation of the response of the structure in the lower frequency range, while for higher frequencies a hybrid WFEM/FEM formulation for modelling discontinuous structures is used.
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Kuehner, Nathanael P. "Extension of transiently evoked otoacoustic emission measurements to cover the entire audiometric frequency range." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29410.pdf.
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Davis, Darren D. "Characterization of the MEMS directional sound sensor in the high frequency (15 - 20 kHz) range." Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10588.
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The Sensor Research Laboratory (SRL) at Naval Postgraduate School (NPS) has developed a micro-electromechanical system (MEMS) based directional sound sensors that mimics the aural system of the Ormia Ochracea Fly. The goal of this research is to characterize a set of directional sound sensors with varying configurations that operate in the high frequency range (15?20 kHz). The sensor consists of two identical wings coupled in the middle and the entire structure is connected to a substrate using two legs in the middle. In response to sound, the coupled wings oscillate with rocking and bending like motions at frequencies that depend on the mechanical characteristics of the structure. A simulation of sensor characteristics using COMSOL finite element software showed a resonant frequency of about 20 kHz for each device. The devices were fabricated by the MEMSCAP foundry service using silicon-on-insulator (SOI) substrate with a 25 ?m device layer. Using a laser vibrometer, response to incident sound pressure was measured at different frequencies and angles. All the devices showed that measured and simulated frequencies were in reasonably close agreement. The measurements showed good sensitivity to the direction of sound as predicted.
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Müller, Daniel [Verfasser]. "RF Probe-Induced On-Wafer Measurement Errors in the Millimeter-Wave Frequency Range / Daniel Müller." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Welsh, David William. "Investigations of cable coupling between various cable types in the frequency range 300kHz to 1GHz." Thesis, University of York, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306280.
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Alison, John Michael. "A dielectric study of lossy materials over the frequency range four to eighty-two gigahertz." Thesis, King's College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263831.
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Kohno, Haruhiko. "Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/76360.
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Thesis (Sc. D. in Applied Plasma Physics)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 183-191).
Electromagnetic plasma waves in the ion cyclotron range of frequencies (ICRF) are routinely used in magnetic fusion experiments to heat plasmas and drive currents. However, many experiments have revealed that wave energy losses in the plasma edge and at the wall are significant, and detected that the acceleration of ions into the walls due to the formation of radio-frequency (RF) sheaths is one of the root causes of this problem. Since the RF-enhanced sheaths have many undesirable effects, such as impurity production and hot spot generation, a predictive numerical tool is required to quantitatively evaluate these effects with complicated boundary shapes of tokamaks taken into account. In this thesis the numerical code that solves self-consistent RF sheath-plasma interactions in the scrape-off layer for ICRF heating is developed based on a nonlinear finite element technique and is applied to various problems in the one-dimensional (1D) and two-dimensional (2D) domains corresponding to simplified models for the poloidal plane of a tokamak. The present code solves for plasma waves based on the cold plasma model subject to the sheath boundary condition, in which the most important physics that happens in the sheath is captured without using the field quantities in the sheath. Using the developed finite element code, several new properties of the RF sheath plasma interactions are discovered. First, it is found in the 1D domain that multiple roots can be present due to the resonance of the propagating slow wave and its nonlinear interaction with the sheath. Second, sheath-plasma waves are identified in a 2D slab geometry, and it is proved in conjunction with an electrostatic 2D sheath mode analysis that the sheath-plasma wave only appears in the vicinity of the sheath surface if the plasma density is greater than the lower hybrid density, and its wavelength depends on various parameters. Third, as a consequence of the self-consistent interaction between the propagating slow wave and the sheath, it is shown that the electric field distribution pattern in the plasma smoothly varies along the magnetic field lines between the conducting-wall and quasi-insulating limits. In the numerical analysis employing the 2D domain whose scale is equivalent to the Alcator C-Mod device, it is demonstrated that the calculated sheath potential can reach the order of kV, which is sufficient to yield enhanced sputtering at the wall. In addition, it is shown that the sheath potential in the close vicinity of the antenna current strap can be insensitive to the direction of the background magnetic field in the RF sheath dominated regime. Further, it is found from a series of nonlinear calculations that the sheath potential sensitively varies depending on the plasma density and electron temperature, which is consistent with the scaling derived from the Child-Langmuir law and the definition of the RF sheath potential. Lastly, a new finite element approach, which is named the finite element wave-packet method, is developed for the purpose of solving for multiscale plasma waves in the tokamak poloidal plane accurately with reasonable computational cost. This method is established by combining the advantages of the finite element and spectral methods, so that important properties in the finite element method, such as the sparsity of the global matrix and the ease in satisfying the boundary conditions, are retained. The present scheme is applied to some illustrative 1D multiscale problems, and its accuracy improvement is demonstrated through comparisons with the conventional finite element method.
by Haruhiko Kohno.
Sc.D.in Applied Plasma Physics
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Xu, Jinshan. "Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42295.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2007.Includes bibliographical references (p. 183-191).
This thesis covers a comprehensive analysis of long-range, deep-ocean, low-frequency, sound propagation experimental results obtained from the North Pacific Ocean. The statistics of acoustic fields after propagation through internal-wave-induced sound-speed fluctuations are explored experimentally and theoretically. The thesis starts with the investigation of the North Pacific Acoustic Laboratory 98-99 data by exploring the space-time scales of ocean sound speed variability and the contributions from different frequency bands. The validity of the Garret & Munk internal-wave model is checked in the upper ocean of the eastern North Pacific. All these results impose hard bounds on the strength and characteristic scales of sound speed fluctuations one might expect in this region of the North Pacific for both internal-wave band fluctuations and mesoscale band fluctuations. The thesis then presents a detailed analysis of the low frequency, broadband sound arrivals obtained in the North Pacific Ocean. The observed acoustic variability is compared with acoustic predictions based on the weak fluctuation theory of Rytov, and direct parabolic equation Monte Carlo simulations. The comparisons show that a resonance condition exists between the local acoustic ray and the internal wave field such that only the internal-waves whose crests are parallel to the local ray path will contribute to acoustic scattering: This effect leads to an important filtering of the acoustic spectra relative to the internal-wave spectra. We believe that this is the first observational evidence for the acoustic ray and internal wave resonance. Finally, the thesis examined the evolution with distance, of the acoustic arrival pattern of the off-axis sound source transmissions in the Long-range Ocean Acoustic Propagation EXperiment.
(cont.) The observations of mean intensity time-fronts are compared to the deterministic ray, parabolic equation (with/without internal waves) and (one-way coupled) normal mode calculations. It is found the diffraction effect is dominant in the shorter-range transmission. In the longer range, the (internal wave) scattering effect smears the energy in both the spatial and temporal scales and thus has a dominant role in the finale region.
by Jinshan Xu.
Ph.D.
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Kathree, Umur. "Investigating the use of hopped frequency waveforms for range and velocity measurements of radar targets." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13266.
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Includes bibliographical references.In the field of radar, High Range Resolution (HRR) profiles are often used to improve tracking accuracy in range and to allow the radar system to produce an image of an object. This work focuses on the use of HRR profiles generated using a sub-class of HRR techniques termed hopped frequency and stepped frequency waveforms. These wideband waveforms are usually synthesised by combining the spectra of the transmitted pulses in the burst [1]. When used with hopped frequency waveforms, this adds the advantage of range-Doppler decoupling and robustness against electronic countermeasures (ECM) [2, 3]. However these waveforms suffer from high levels of sidelobes [4] and improving the spurious free dynamic range (SFDR) of target measurements was required. This was done with the CLEAN technique [5] which could reduce sidelobe levels to below -60 dB and would allow smaller targets masked by the sidelobes to be uncovered. To analyse the practicality of this work, simulated rotating scatterers were used and these techniques could perform adequately for signal to noise ratios (SNR) above -10 dB and signal to clutter ratios (SCR) above 14 dB. Clutter mitigation is to be investigated in future work to make it applicable to lower SCR and sub-clutter visibility.
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Yildiz, Inanc. "Design And Construction Of Reduced Size Planar Spiral Antenna In The 0.5-18 Ghz Frequency Range." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605610/index.pdf.
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iv
ABSTRACT
DESIGN AND CONSTRUCTION OF REDUCED SIZE
PLANAR SPIRAL ANTENNA IN THE
0.5-18 GHz FREQUENCY RANGE
YILDIZ, 5nançM.S., Department of Electrical and Electronics Engineering Supervisor: Prof. Dr. Altunkan HIZAL October 2004, 106 pages In this thesis, theoretical and practical evaluation of usual spiral antenna is revised. Working principles of both types of planar spiral antennas as Equiangular and Archimedean are introduced. A predesigned microstrip tapered balun used for feeding section of a spiral antenna is simulated on Ansoft HFSS software. Successful simulation results are obtained and measurements of implemented balun structure are made by using an HP 8722 D vector network analyzer. Antenna measurement techniques used in this study are introduced. Measurement set-ups are defined and some preliminary knowledge is given on these. As the main matter of thesis, reduced size planar spiral antennas are designed and implemented. Return loss, gain
radiation and polarization patterns of antennas are measured. Datasets of measurements are compared with each other and with reference spiral antenna. Quite promising results are obtained and size reduction of spiral antenna is achieved in many aspects.
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Arriagada, Anton. "A wideband high dynamic range frequency hopping hardware front-end for the joint tactical radio system." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/fullcit?p1477881.
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Thesis (M.S.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed July 13, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (leaf 63).
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Plattner, Kristina. "The association between exercise-induced muscle damage and cortical activity in the alpha and beta frequency range." Doctoral thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11524.
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Includes abstract.Includes bibliographical references (p. 139-178).
This thesis examines the regulation of muscle function following exercise-induced muscle damage (EIMD), in an attempt to determine whether regulation occurs primarily in the muscle (neuromuscular) or further upstream. Upstream regulation has been hypothesized to occur in the lower brain structures, but one may assume that the efferent output to the muscle should be guided by the motor and pre-motor cortex alongside other associated cortical areas.
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Duran, Rolando Silvano. "Noise in gallium nitride-based quantum well structures used for nanometer devices in the frequency range 1 HZ-3 MHZ and temperature range 77K - 324K." FIU Digital Commons, 2002. http://digitalcommons.fiu.edu/etd/3104.
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Electronic noise has been investigated in AlxGa1-xN/GaN Modulation-Doped Field Effect Transistors (MODFETs) of submicron dimensions, grown for us by MBE (Molecular Beam Epitaxy) techniques at Virginia Commonwealth University by Dr H. Morkoç and coworkers. Some 20 devices were grown on a GaN substrate, four of which have leads bonded to source (S), drain (D), and gate (G) pads, respectively. Conduction takes place in the quasi-2D layer of the junction (xy plane) which is perpendicular to the quantum well (z-direction) of average triangular width ~3 nm. A non-doped intrinsic buffer layer of -5 nm separates the Si-doped donors in the AlxGa1-xN layer from the 2D-transistor plane, which affords a very high electron mobility, thus enabling high-speed devices. Since all contacts (S, D, and G) must reach through the AlxGa1-xN layer to connect internally to the 2D plane, parallel conduction through this layer is a feature of all modulation-doped devices. While the shunting effect may account for no more than a few percent of the current IDS, it is responsible for most excess noise, over and above thermal noise of the device.
The excess noise has been analyzed as a sum of Lorentzian spectra and 1/ƒ noise. The Lorentzian noise has been ascribed to trapping of the carriers in the AlxGa1-xN layer. A detailed, multitrapping generation-recombination noise theory is presented, which shows that an exponential relationship exists for the time constants obtained from the spectral components as a function of 1/kT. The trap depths have been obtained from Arrhenius plots of log (τT2) vs. 1000/T Comparison with previous noise results for GaAs devices shows that: a) many more trapping levels are present in these nitride-based devices; b) the traps are deeper (farther below the conduction band) than for GaAs Furthermore, the magnitude of the noise is strongly dependent on the level of depletion of the AlxGa1-xN donor layer, which can be altered by a negative or positive gate bias VGS.
Altogether, these frontier nitride-based devices are promising for bluish light optoelectronic devices and lasers; however, the noise, though well understood, indicates that the purity of the constituent layers should be greatly improved for future technological applications.
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Burgess, Samuel J. "An investigation of the propagation characteristics of a single frequency mid-latitude NVIS radio channel." Thesis, University of Ulster, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370086.
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Kobayashi, Katsuya. "Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation." Kyoto University, 2015. http://hdl.handle.net/2433/202676.
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Umchid, Sumet Lewin Peter A. "Development of calibration techniques for ultrasonic hydrophone probes in the frequency range from 1 to 100 MHz /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/2524.
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Usman, Isa Shamsuddeen. "Development of point to multi-point models for availability and fade mitigation in the millimetre wave frequency range." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760857.
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Rida, Amin Hassan. "Integrated RF modules and passives on low-cost flexible materials for applications up to the mm-wave frequency range." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39552.
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The objective of the proposed research is to develop solutions for High-Performance Low-Cost Passives for Radar, Identification, and Communication Applications up to mm-Wave Frequencies. This research will bring to the table potential solutions that will meet three main requirements: small size (or low weight), high performance, and low cost. This research embarks on antenna design and development for passive RFID tags on LCP substrates, and then a transition towards lower cost modules investigates and explores the possibilities of using paper as RF substrates with inkjet printing as a low cost fabrication technology. Modules such as dual band antenna for Wifi frequencies (2.4 GHz and 5 GHz) and UWB (up to 10GHz) on paper substrate using inkjet printing are presented. This work then bridges into developing higher frequency modules. These include: highly selective filter design on LCP for X-band Radar application to be used as a benchmark for an easy adjustment for higher frequencies, and antenna modules LCP using inkjet printing for communication such as mm-Wave WLAN or WPAN.
A transition into mm-Wave Modules then takes place for the general realization of low-cost high-performance mm-Wave modules and more specifically the low cost automotive radar. After proposing an architecture for integrated mm-Wave module, this work then investigates 2D/3D interconnections (and their integration with antennas) on LCP using conventional etching design guidelines up to 100GHz. Antenna arrays that are implemented with phase shifters for beam steering are then designed using edge fed and multilayer technology. Furthermore, crosstalk reductions for highly dense transmission lines are analyzed via simulations for the optimum performance and space saving of such mm-Wave modules such as the IC interface where space restrictions are strictly enforced.
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Kirtay, Selçuk. "Interference analysis of broadband space and terrestrial fixed radio communications systems in the frequency range 12 to 30 GHz." Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/4118/.
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This thesis presents research into the principles of spectrum sharing analysis methods developed for investigating implications of interference from Nongeostationary Fixed Satellite Service (NGSO FSS) systems into Geostationary Fixed Satellite Service (GSO FSS) systems and Fixed Service (FS) terrestrial radio systems operating or planned for operation in the 12 to 30 GHz frequency range. Spectrum sharing is an effective way of allowing new services to operate without cancelling the existing allocations in the same part of the spectrum. The use of spectrum sharing results in re-use of the available spectrum among different services and, therefore, increases the efficient use of the radio frequencies. However, it is necessary to carry out extensive feasibility studies into technical or operational compatibility between the services involved. Often, sharing constraints are placed on systems, such as the power of emissions and the transmitter and receiver antenna pointings to reduce the interference into negligible levels. Traditionally, radio spectrum allocated to GSO FSS has been shared with FS. In recent years, there has been a growing interest in the use of low Earth orbits and a number of NGSO FSS constellations has been designed to provide broadband data services. This has led to the allocation of certain bands used by the FS and GSO FSS systems to NGSO FSS. In line with the new allocations, NGSO FSS, GSO FSS and FS systems are required to co-exist in parts of the 12 to 30 GHz frequency range. The primary objectives of this research were to identify principal factors affecting the feasibility of spectrum sharing and to develop spectrum sharing analysis methodologies to examine the implications of these factors with a view to identifying sharing constraints that would give rise to an acceptable sharing environment.
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Pokkuluri, Kiran S. "Effect of Admixtures, Chlorides, and Moisture on Dielectric Properties of Portland Cement Concrete in the Low Microwave Frequency Range." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/37039.
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The use of electromagnetic waves as a nondestructive
evaluation technique to evaluate Portland cement concrete
(PCC) structures is based on the principle that a change in
the structure, composition, or properties of PCC results in
a change in its dielectric properties. The coaxial
transmission line is one of the few devices that can
measure the dielectric properties of PCC at a frequency
range of 100-1000 MHz. A coaxial transmission line
developed at Virginia Tech was used to study the effect
of moisture, type of aggregate, water/cement ratio, curing
period, admixture type (microsilica, superplasticizer, and
shrinkage admixture), and chloride content on the dielectric
properties of PCC.
Measurements were conducted in the time
domain and converted to the frequency domain using Fast
Fourier Transform. The research found that an increase in
the moisture content of PCC resulted in an increase in the
dielectric constant. Mixes containing limestone aggregate
had a greater dielectric constant than those containing
granite. The dielectric constant decreased with curing
period due to the reduction in free water availability.
Mixes containing higher water/cement ratios exhibited a
higher dielectric constant, especially in the initial
curing period. The admixtures did not significantly
affect the dielectric constant after one day of curing.
After 28 days of curing, however, all three admixtures
had an effect on the measured dielectric constant as
compared to control mixes. Chloride content had a
significant effect on the loss part of the dielectric
constant especially during early curing. A relationship
was also established between the chloride permeability
(based on conductance measurements) of PCC and its
dielectric constant after 75 days of moist curing.Master of Science
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Greeff, Wildine Marion. "Ototoxicity Monitoring using Automated Extended High-Frequency Audiometry and the Sensitive Range of Ototoxicity in Patients with MDR-TB." Master's thesis, Faculty of Health Sciences, 2021. http://hdl.handle.net/11427/32696.
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Background: Disabling hearing loss is a global burden. This burden is worsened by the emergence of multi-drug resistant tuberculosis (MDR-TB). Some of the medications used to treat MDR-TB are damaging to the cochlea and auditory nerve (ototoxic) and can lead to permanent hearing loss and/or balance disorders. Ototoxicity monitoring aims to reduce this burden by preventing or minimising the damage caused by ototoxic treatment as it can progress and worsen speech perception difficulties. However, the proposed test battery for ototoxicity monitoring is lengthy and demands active participation which is not ideal for ill patients (such as those on MDR-TB treatment). The Sensitive Range of Ototoxicity (SRO) technique is recommended to shorten the test time. The SRO consists of seven consecutive relatively high frequencies determined from the highest frequency the participant responded to. The SRO technique is time efficient. Although the SRO technique provides the prospect of a shortened test battery, there is still a global lack of audiologists. Automated audiometry is a vital application for testing especially when audiologists are not available to physically do the test. Automated audiometry has been previously validated. Clinically, automated audiometry is objective and allows for standardisation. Even though automated audiometry helps improve access to monitoring more patients, patient preference is an important factor when using automated audiometry to ensure patient-centred care is not compromised. Aims and Objectives: This study aimed to investigate the specificity and sensitivity of the SRO technique with automated audiometry compared to the gold standard (manual audiometry). This comparison was made by firstly, determining the testing time efficiency and the correlation of thresholds obtained with the different test methods and, secondly, testing the diagnostic value of automated audiometry using the SRO technique. The incidence of an ototoxicity-induced hearing loss was described by determining the time interval between starting ototoxic MDR-TB treatment and the onset of a significant threshold shift (STS) according to ASHA's criteria. Lastly, the test method preference of the participants with MDR-TB was described and compared using a short exit survey. Study Design: A prospective repeated-measures study design was used. Participants were chosen based on a risk factor (i.e. exposure to ototoxic medication) for an outcome of interest (i.e. the presence or absence of an STS). With a repeated measures study, multiple tests using different test methods can be compared with the same sample. Participants: Twenty-seven in-patients at Brooklyn Chest Hospital and DP Marais TB Hospital with normal hearing and on MDR-TB medication were included in the study. Their age range was from 19 to 51 years old with an average age of 33 years old. Non-probability convenience sampling was used as it was cost-effective, reduced data collection time and was relatively easy to execute. Data collection materials and procedures: The procedure for data collection included weekly follow-up testing for a maximum of four weeks. The test battery was as follows: an auditory symptom questionnaire, otoscopy examination, and manual and automated audiometry using the SRO technique with a fifteen-minute break in between. Participants were tested with the KUDUwave ™ in a non-sound treated room. The frequency range was determined with the SRO technique. If an STS was obtained, the patient was discharged from the study after completing an exit survey. Statistics: Analysis included descriptive statistics and inferential statistics. A Bonferroni corrected p-value (initially p ≤ 0.05) was used. Manual and automated audiometry thresholds were compared using the Pearson's Correlation Coefficient test. Manual and automated audiometry testing time and threshold means were compared using paired sample's t-tests. The diagnostic value of automated audiometry with the SRO technique was assessed with Receiver Operating Characteristics (ROC) Curves. Results: Manual audiometry was statistically more time-efficient compared to automated audiometry by an average of one minute and ten seconds (t (94) = -5.44; p< 0.003). There was a strong positive correlation for both left and right ears between the thresholds' obtained from manual and automated audiometry at 8kHz to 16 kHz (df> 28 = r > 0.70, p< 0.003). Automated audiometry was found to be a fair diagnostic test (area under the curve was 0.75; p= 0.002). Also, the ROC curve revealed that automated audiometry had a sensitivity of 61% and specificity of 90% when compared to manual audiometry (gold standard). Only participants that started data collection within 31 days after starting their MDR-TB treatment were included in the analysis of determining the incidence of an ototoxicity-induced hearing loss (n= 24 ears). This study found that 41.67% of ears (n= 10) had an ototoxicity-induced hearing loss. A box and whisker plot revealed that data was skewed to the right (i.e. more variation in data between the median and the maximum values) and that the median number of days for an ototoxicity-induced hearing loss to appear was 33 days. Secondly, 55.55% of participants (n=15 out of 27) reported auditory symptoms before data collection commencement. Aural fullness was the most reported symptom (n= eight out of 15). Ten out of 15 (66.66%) participants that reported auditory symptoms obtained an ototoxicity-induced hearing loss. Lastly, most participants (i.e. 13 out of 19; 68.42%) that completed the exit survey had no preference between manual or automated audiometry. The common rationale among these participants was “No difference noted.” Conclusion: This research study has revealed that manual audiometry was more time-efficient compared to automated audiometry in patients with MDR-TB. Also, automated audiometry was a fair diagnostic test. It may aid in reducing the disproportionate audiologist to patient ratio, especially in a developing country. However, manual audiometry (with the SRO technique) is more clinically appropriate in patients that are difficult-to-test. Secondly, audiometric settings can be changed to accommodate testing frequencies in 1/6 octaves so that the SRO technique can be clinically adopted. An ototoxicity-induced hearing loss seems to appear 33 days after ototoxic MDR-TB treatment commencement. Aural fullness was a commonly reported symptom among participants with MDRTB. Aural fullness is omnipresent in peripheral auditory pathologies. Therefore, auditory symptoms reported by patients' needs a comprehensive audiological investigation. Lastly, more research is needed on how patients (and clinicians) experience the advances in technology innovation especially in audiology where technology innovation is continuously evolving.
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Bennett, Bradley Wayne. "The effects of nutrition and reproductive strategies on performance of beef cattle grazing native shortgrass range in western Kansas." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/16294.
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Master of ScienceDepartment of Animal Sciences and Industry
John Jaeger
Cattle grazing dormant native range (< 7% crude protein; CP) require supplementation of additional protein to sustain body weight (BW) and body condition score (BCS). Daily delivery of these supplements is an economic burden to cattle producers faced with challenging economic circumstances. Supplementing cows infrequently (as little as once/week) has produced equivalent BW and BCS changes compared to daily delivery. Dried distiller’s grains with solubles (DDGS) provides more ruminally-undegradable protein (RUP; 50-60%) compared to traditional oilseed-meal supplements (i.e. soybean meal) that are >50% ruminally-degradable protein (RDP). Therefore, our objective was to evaluate the effects of supplementation frequency on performance, reproductive success, eating behavior, and subsequent calf performance of spring-calving cows supplemented with DDGS. No differences in ending BW (P = 0.69) and BCS (P = 0.49), or changes in BW and BCS over the supplementation period (P = 0.82 and 0.70, respectively) were observed among cows supplemented every d, every 3 d, or every 6 d. Calf BW at birth, weaning weight (WW), and average daily gain (ADG) were similar among treatments (P = 0.19, 0.12, and 0.10, respectively). First-service conception rate (FSCR) and final pregnancy rate (PR) were also not affected by supplementation frequency (P = 0.62 and 0.76, respectively). The development of replacement heifers is a large expense for cow-calf producers. Improved breeding and heifer development strategies aimed at ensuring the success of replacement females have been developed but reproductive failure still remains a problem. The stress associated with breeding and handling procedures may decrease reproductive success. Therefore, the objective was to determine if intramuscular administration of flunixin meglumine (1.1 mg/kg BW) 14 days post-breeding would improve FSCR and PR in non-transported replacement heifers. Under the conditions of our study, flunixin meglumine did not improve (P = 0.87) first service conception rate above that of control heifers (41.2% and 42.3%, respectively). Final pregnancy rate also was not different between treatments and averaged 81.8% (P = 0.40).
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Smith, Norman Alan. "The steady-state and post-ignition transient luminous behaviour of the tubular fluorescent lamp operating throughout the dimmed mode range using high frequency dimming." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387764.
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Yang, Liyu. "Modeling and Characterization of a PFC Converter in the Medium and High Frequency Ranges for Predicting the Conducted EMI." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/35226.
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This thesis presents the conducted electro-magnetic interference (EMI) prediction results for a continuous conduction mode (CCM) power factor correction (PFC) converter as well as the theoretical analysis for the noise generation and propagation mechanisms.
In this thesis, multiple modeling and characterization techniques in the medium and high frequency ranges are developed for the circuit components that are important contributors to the EMI noise, so that a detailed simulation circuit for EMI prediction can be constructed.
The conducted EMI noise prediction from the simulation circuit closely matches the measurement results obtained by a spectrum analyzer. Simulation time step and noise separator selection are two important issues for the noise simulation and measurement. These two issues are addressed and the solutions are proposed.
The conducted EMI generation and propagation mechanisms are analyzed in a systematic way. Two loop models are proposed to explain the EMI noise behavior. The effects of the PFC inductor, the parasitic capacitance between the device and the heatsink, the rising/falling time of the MOSFET VDS voltage, and the input wires are studied to verify the validity of the loop models.Master of Science
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Tye, Thomas N. "Application of digital signal processing methods to very high frequency omnidirectional range (VOR) signals in the design of an airborneflight measurement system." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1177702951.
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Tye, Thomas N. "Application of digital signal processing methods to very high frequency omnidirectional range (VOR) signals in the design of an airborne flight measurement system." Ohio University / OhioLINK, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1177702951.
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Lu, LingFeng. "Modelling of plasma-antenna coupling and non-linear radio frequency wave-plasma-wall interactions in the magnetized plasma device under ion cyclotron range of frequencies." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0173/document.
Full textAbstract:
Le Chauffage Cyclotron Ionique (ICRH) par des ondes dans la gamme 30-80MHz est couramment utilisé dans les plasmas de fusion magnétique. Excitées par par des réseaux phasés de rubans de courant à la périphérie du plasma, ces ondes existent sous deux polarisations. L’onde rapide traverse le bord ténu du plasma par effet tunnel puis se propage à son centre où elle est absorbée. L’onde lente, émise de façon parasite, existe seulement à proximité des antennes. Quelle puissance peut être couplée au centre avec 1A de courant sur les rubans? Comment les champs radiofréquence (RF) proches et lointains émis interagissent-ils avec le plasma de bord par rectification de gaine RF à l’interface plasma-paroi? Pour répondre simultanément à ces deux questions, en géométrie réaliste sur l’échelle spatiale des antennes ICRH, cette thèse a amélioré et testé le code numérique SSWICH (Self-consitent Sheaths and Waves for ICH). SSWICH couple de manière auto-cohérente la propagation des ondes RF et la polarisation continue (DC) du plasma via des conditions aux limites non-linéaires de type gaine (SBC) appliquées à l’interface plasma / paroi. La nouvelle version SSWICH-FW est pleine onde et a été développée en deux dimensions (toroïdale/radiale). De nouvelles SBCs couplant les deux polarisations d’ondes ont été obtenues et mises en œuvre le long de parois courbes inclinées par rapport au champ magnétique de confinement. Avec ce nouvel outil en l'absence de SBCs, nous avons étudié l'impact d'une densité décroissant continûment à l'intérieur de la boîte d'antenne en traversant la résonance hybride basse (LH). Dans les limites mémoire de notre poste de travail, les champs RF au-dessous de la résonance LH ont changé avec la taille de maille. Par contre spectre de puissance couplée n’a que très peu évolué, et n’était que faiblement influencé par la densité à l'intérieur de l'antenne. En présence de SBCs, les simulations SSWICH-FW ont identifié le rôle de l'onde rapide sur l’excitation de gaines RF et reproduit certaines observations expérimentales clés. SSWICH-FW a finalement été adapté pour réaliser les premières simulations 2D électromagnétiques et de gaine-RF de la machine plasma cylindrique magnétisée ALINEIon Cyclotron Resonant Heating (ICRH) by waves in 30-80MHz range is currently used in magnetic fusion plasmas. Excited by phased arrays of current straps at the plasma periphery, these waves exist under two polarizations. The Fast Wave tunnels through the tenuous plasma edge and propagates to its center where it is absorbed. The parasitically emitted Slow Wave only exists close to the launchers. How much power can be coupled to the center with 1A current on the straps? How do the emitted radiofrequency (RF) near and far fields interact parasitically with the edge plasma via RF sheath rectification at plasma-wall interfaces? To address these two issues simultaneously, in realistic geometry over the size of ICRH antennas, this thesis upgraded and tested the Self-consistent Sheaths and Waves for ICH (SSWICH) code. SSWICH couples self-consistently RF wave propagation and Direct Current (DC) plasma biasing via non-linear RF and DC sheath boundary conditions (SBCs) at plasma/wall interfaces. Its upgrade is full wave and was implemented in two dimensions (toroidal/radial). New SBCs coupling the two polarizations were derived and implemented along shaped walls tilted with respect to the confinement magnetic field. Using this new tool in the absence of SBCs, we studied the impact of a density decaying continuously inside the antenna box and across the Lower Hybrid (LH) resonance. Up to the memory limits of our workstation, the RF fields below the LH resonance changed with the grid size. However the coupled power spectrum hardly evolved and was only weakly affected by the density inside the box. In presence of SBCs, SSWICH-FW simulations have identified the role of the fast wave on RF sheath excitation and reproduced some key experimental observations. SSWICH-FW was finally adapted to conduct the first electromagnetic and RF-sheath 2D simulations of the cylindrical magnetized plasma device ALINE
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Oakes, Benjamin. "On long-range and high frequency propagation alongparallel strip conductors in layered media : A simplified yet accurate method using the mode matching technique in the spectral domain." Thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129538.
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Electrical arcing in the railway environment radiates wideband noise that can disturb nearbysensitive electronics e.g. signaling systems. High frequency disturbances follow conducting wiresand rails. For Electromagnetic Compatibility reasons, radiation from wire structures is studied atspecific frequencies, to assess the risk to sensitive electrical devices further along the track.The specific problem is to construct a fast and accurate solver for computing the currents inducedby a dipole source on an arbitrary number of parallel wires inside a layered medium. In this project, atwo-layered medium is considered, each medium defined by arbitrary permittivity and permeability.Once the wire currents are known, the fields may be calculated everywhere.The approach is to transform the circular wires into equivalent strips, creating a planarly layeredstructure. The fields from a source in a layered structure may be expanded as a sum of planewaves propagating in the direction of stratification. The strip currents are expanded into Chebyshevpolynomials and together with the fields and boundary conditions, the currents are solved with themode matching technique in the spectral domain.Moreover, a simplified model for strips much narrower than the wavelength is derived, onlyconsidering axial currents, further reducing the complexity of the problem and still exhibiting highaccuracy.Unlike most full wave methods, the spectral domain approach does not rely on spatial discretisationof wires. Since infinitely long wires are considered, they are electrically large and thusconventional full wave methods yield to massive computations as many grid points are required, thusmotivating the spectral domain approach.The result is a linear system of integral equations solving the currents on an arbitrary numberof narrow strips. Results for different configurations of strips and dipole locations are shown andverified by comparing them with a commercial Method of Moments based solver, 4NEC2, using finitelengths of wire.In conclusion, a simple, fast and accurate method has been developed in Matlab for solving thecurrents along parallel strip conductors.Blixtar längs järnvägen strålar bredbandigt brus som kan störa närligande känslig elektronik t.ex.signaleringssystem. Högfrekventa störningar följer ledningar och spår. För elektromagnetisk förenlighet,studeras strålning från ledningstrukterer vid specifika frekvenser, för att bedömma risken förkänsliga system längre bort längs ledningen.Problemet är att konstruera en snabb och nogrann numerisk lösare för att beräkna strömmarnainducerade av en dipolkälla hos en godtycklig antal parallella ledare innuti en lagrad struktur. Idetta projekt används en tvålagrig struktur, varje medium definierad av godtycklig permittivitet ochpermeabilitet. Då strömmarna i ledningarna är kända, kan fälten bestämmas överallt.Metoden är att transformera de circulära ledarna till ekvivalenta strips, vilket skapar ett plantlagrat struktur. Fält som härör en källa i ett lagrat medium kan expanderas som en summa planavågor som utökar sig i avlagringsrikningen. Strömmar på stripen expanderas som Chebyshev polynomoch tillsammans med fält och gränsvärden, kan strömmarna tas fram med modanpassning ispektrala rummet.Utöver detta, har en simplifierad model för strips mycket smalare än våglängen härleds fram,där enbart strömmar i stripens parallella riktning utses vilket vidare förenklar problemet utan attförlora mycket nogrannhet.Olikt de alra flest helvågsmetoderna, använder sig inte spektrala metoden av rumdiskretiseringav ledare. Eftersom ledarna i frågan är oändligt långa är de elektriskt stora som gör att rumdiskretiseringkommer att orsaka för stora beräkningar då det kräver för många diskretiserings punkter,vilket motiverar valet av spektrala metoden.Resultatet är ett linjärt ekvationssystem bestående av integralekvationer för att lösa strömmarnalängs en godtycklig antal smala ledare. Resultat för olika konfigurationer av strips och dipolpositionär redovisade och överensstämmer väl med den kommersiella Method of Moments baserade lösaren4NEC2 med ändligt långa ledare.Sammanfattningsvis, har det tagits fram en enkel, snabb och nogrann metod i Matlab för attlösa strömmarna längs parallella ledande strips.
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Sudiarto, Budi [Verfasser], and Holger [Akademischer Betreuer] Hirsch. "The properties and behavior of disturbances in the frequency range 9 kHz to 150 kHz produced by household appliances in a residential network environment / Budi Sudiarto ; Betreuer: Holger Hirsch." Duisburg, 2017. http://d-nb.info/1142113612/34.
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Bohnert, Julia [Verfasser], and O. [Akademischer Betreuer] Dössel. "Effects of Time-Varying Magnetic Fields in the Frequency Range 1 kHz to 100 kHz upon the Human Body : Numerical Studies and Stimulation Experiment / Julia Bohnert ; Betreuer: O. Dössel." Karlsruhe : KIT Scientific Publishing, 2012. http://d-nb.info/1184494185/34.
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Kahl, Philipp. "Identification of long-range solid-like correlations in liquids and role of the interaction fluid-substrate." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1002/document.
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Les liquides diffèrent des solides par une réponse retardée à la sollicitation en cisaillement; c’est-à-dire une absence d’élasticité de cisaillement et un comportement d'écoulement à basses fréquences (<1 Hz). Ce postulat pourrait ne pas être vrai à toutes échelles. A l’échelle submillimétrique, les mesures viscoélastiques (VE) réalisées en améliorant l'interaction entre le liquide et le substrat, montrent qu’une élasticité basses-fréquences existe dans des liquides aussi variés que les polymères, les surfondus, les liquides à liaison H, ioniques ou van der Waals. Ce résultat implique que les molécules à l'état liquide ne seraient pas dynamiquement libres, mais élastiquement corrélées.En utilisant les propriétés biréfringentes des fluctuations prétransitionnelles qui coexistent dans la phase isotrope des cristaux liquides, nous montrons qu'il est possible de visualiser ces corrélations « cachées ». Dans des conditionssimilaires aux mesures VE, une biréfringence optique synchrone à la déformation est observée dans la phase isotrope à des fréquences aussi basses que 0.01 Hz et des températures éloignées de toute transition. Le comportement dela biréfringence basses-fréquences a des similitudes avec l'élasticité; elle est en phase avec la déformation à faibles amplitudes de déformation, puis en phase avec le taux de déformation à plus grandes amplitudes. La biréfringence basses- fréquences est forte, sans défaut et réversible. Elle indique un ordre à longue portée. La synchronisation de la réponse à la sollicitation en fréquence et l’état ordonné qu’elle produit ne sont pas compatibles avec un état liquide isotrope mais montrent qu’il s’agit d’un état élastique soumis à déformation (entropie élastique)Liquids differ from solids by a delayed response to a shear mechanical solicitation; i.e. they have no shearelasticity and exhibit a flow behaviour at low frequency (<1 Hz). This postulate might be not verified at thesub-millimeter scale. By optimizing the measurement in particular by improving the liquid/substrate interactions (wetting), a low frequency shear elasticity has been found in liquids including molten polymers, glass-formers, H-bond polar, ionic or van der Waals liquids. This result implies that molecules in the liquid state may not be dynamically free but weaklyelastically correlated. Using the birefringent properties of the pretransitional fluctuations coexisting in the isotropic phase of liquid crystals, we show that it is possible to visualize these “hidden” shear-elastic correlations. We detect a synchronized birefringent optical response in the isotropic phase that is observable at frequencies as low as 0.01 Hz and at temperatures far away from anyphase transition. The low-frequency birefringence exhibits a strain dependence similar to the low frequency elasticity: An optical signal that is in-phase with the strain at low strain amplitudes and in-phase with the strain-rate at larger strain amplitudes. The birefringent response is strong, defect-free, reversible and points out a collective response. This long-range ordering rules out the condition of an isotropic liquid and its synchronized response supports the existenceof long-range elastic (solid-like) correlations. In the light of this, the strain dependence of the harmonic birefringent signal and the shear elasticity may correspond to an entropy-driven transition
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Li, Xun. "Soybean rust in the United States assess its potential epidemic ranges and frequency based on disease limiting factors, disease attributes, and comparative epidemiology /." [Ames, Iowa : Iowa State University], 2007.
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Lott, Gus K. Jr. "High Frequency (HF) radio signal amplitude characteristics, HF receiver site performance criteria, and expanding the dynamic range of HF digital new energy receivers by strong signal elimination [electronic resource]." Thesis, Monterey, California: Naval Postgraduate School, 1990. http://hdl.handle.net/10945/34806.
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Approved for public release; distribution unlimited.The dissertation discusses High Frequency (HF) radio sources. It consolidates data from all available, published HF spectrum surveys. The author conducted a new HF survey using detection of new energy events. The first cumulative probability distribution function for the amplitude of detected non-broadcast HF signals is developed, and the distribution is log-normal. HF receiver site performance quantification is possible using the HF signal distributions. Site performance degradation results from noise, interference, and signal path attenuation. Noise examples are presented in a 3-D format of time, frequency, and amplitude. Graphs are presented that allow estimation of the percentage of HF non-broadcast signals lost as a function of noise and interference levels. Limitations of HF search receivers using analog-to-digital converters as the receiver front-end are discussed. Derived bounds on AD converter performance show that today's digital technology does not provide enough dynamic range, sensitivity, or sampling rate. Alternative dynamic range extension methods are examined. A new method of dynamic range extension by removing the strongest signals present is presented. Greater receiver sensitivity results from changing the HF signal environment seen by the AD converter. The new method uses a phase-tracking network and signal reconstruction techniques.
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Al-Share, Mohammad A. (Mohammad Abdel). "Anomalous Behavior in the Rotational Spectra of the v₈=2 and the v₈=3 Vibrations for the ¹³C and ¹⁵N Tagged Isotopes of the CH₃CN Molecule in the Frequency Range 17-95 GHz." Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc330976/.
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The rotational microwave spectra of the three isotopes (^13CH_3^12C^15N, ^12CH_3^13C^15N, and ^13CH_3^13C^15N) of the methyl cyanide molecule in the v_8=3, v_8=2, v_7=1 and v_4=1 vibrational energy levels for the rotational components 1£J£5 (for a range of frequency 17-95 GHz.) were experimentally and theoretically examined. Rotational components in each vibration were measured to determine the mutual interactions in each vibration between any of the vibrational levels investigated.
The method of isotopic substitution was employed for internal tuning of each vibrational level by single and double substitution of ^13C in the two sites of the molecule. It was found that relative frequencies within each vibration with respect to another vibration were shifted in a systematic way. The results given in this work were interpreted on the basis of these energy shifts. Large departure between experimentally measured and theoretically predicted frequency for the quantum sets (J, K=±l, ϑ=±1), Kϑ-l in the v_8=3 vibrational states for the ^13c and ^15N tagged isotopes of CH_3CN showed anomalous behavior which was explained as being due to Fermi resonance. Accidently strong resonances (ASR) were introduced to account for some departures which were not explained by Fermi resonance.
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Trent, Vanessa. "An investigation into the effect of stretching frequency on range of motion at the ankle joint thesis submission to Auckland University of Technology in partial fulfilment of the degree of Master in Health Science, September 2002." Full thesis. Abstract, 2002. http://puka2.aut.ac.nz/ait/theses/TrentV.pdf.
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Mbonye, Marx. "Novel Waveguide Techniques in the Terahertz Frequency Range." Thesis, 2013. http://hdl.handle.net/1911/72001.
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Over the last decade, considerable research interest has peaked in realizing an efficient Terahertz (THz) waveguide for potential applications in imaging, sensing, and communications applications. Two of the promising candidates are the two-wire waveguide and the parallel-plate waveguide (PPWG). I present theoretical and experimental evidence that show that the two-wire waveguide supports low loss terahertz pulse propagation, and illustrate that the mode pattern at the end of the waveguide resembles that of a dipole. In comparison to the weakly guided Sommerfeld wave of a single wire waveguide, this two-wire structure exhibits much lower bending losses. I also observe that a commercial 300-Ohm two-wire TV-antenna cable can be used for guiding frequency components of up to 0.2 THz, although these cables are generally designed to operate only up to about 800 MHz. The parallel-plate waveguide is another promising candidate that would make an efficient THz waveguide, since it has relatively low Ohmic losses. The transverse electromagnetic mode (TEM) of this waveguide has been generally preferred since it has no cutoff frequency, and therefore no group velocity dispersion. Utilizing this TEM mode, I study the reflection of THz radiation at the end of a PPWG, due to the impedance mismatch between the propagating transverse-electromagnetic mode and the free-space background. I find that for a PPWG with uniformly spaced plates, the reflection coefficient at the output face increases as the plate separation decreases, consistent with predictions by early low frequency ray optical theory. I observe this same trend in tapered PPWGs, when the input separation is fixed, and the output separation is varied. In another study, I investigate how to minimize diffraction losses in PPWGs by using plates with slightly concave surfaces. Using a simple “bouncing plane wave” analysis, I demonstrate how to determine an ideal radius of curvature for a waveguide operating at a given THz frequency. I perform a detailed experimental and simulation study that illustrates, for a waveguide with a plate separation of 1 cm, one can inhibit the diffraction around a frequency of 0.1 THz, when the surface has a curvature of 6.7 cm. Using much longer PPWGs (about 170cm), I reliably measure the overall losses in a PPWG with a radius of curvature of R=6.7 cm, and find it to be less than 1db/m around the design frequency (of 0.1 THz). This is very close to the lowest achieved loss to date with any terahertz waveguide.