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El-Fandi, Mahmoud. „New multisymbol signals and recursive algorithms for frequency response measurement“. Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248819.
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Jeon, Byung Ho. „Proposed automobile steering wheel test method for vibration“. Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4623.
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This thesis proposes a test method for evaluating the perceived vibration which occurs at the driver's hand in automotive steering wheel interface. The objective of the research was to develop frequency weightings for quantifying the human perception of steering wheel hand-arm vibration. Family of frequency weightings were developed from equal sensation curves obtained from the psychophysical laboratory experimental tests. The previous literature suggests that the only internationally standardised frequency weighting Wh is not accurate to predict human perception of steering wheel hand-arm vibration (Amman et. al, 2005) because Wh was developed originally for health effects, not for the human perception. In addition, most of the data in hand-arm vibration are based upon responses from male subjects (Neely and Burström, 2006) and previous studies based only on sinusoidal stimuli. Further, it has been continuously suggested by researchers (Gnanasekarna et al., 2006; Morioka and Griffin, 2006; Ajovalasit and Giacomin, 2009) that only one weighting is not optimal to estimate the human perception at all vibrational magnitudes. In order to address these problems, the investigation of the effect of gender, body mass and the signal type on the equal sensation curves has been performed by means of psychophysical laboratory experimental tests. The test participants were seated on a steering wheel simulator which consists of a rigid frame, a rigid steering wheel, an automobile seat, an electrodynamic shaker unit, a power amplifier and a signal generator. The category-ratio Borg CR10 scale procedure was used to quantify the perceived vibration intensity. A same test protocol was used for each test and for each test subject. The first experiment was conducted to investigate the effect of gender using sinusoidal vibration with 40 test participants (20 males and 20 females). The results suggested that the male participants provided generally lower subjective ratings than the female participants. The second experiment was conducted using band-limited random vibration to investigate the effect of signal type between sinusoidal and band-limited random vibration with 30 test participants (15 males and 15 females). The results suggested that the equal sensation curves obtained using random vibration were generally steeper and deeper in the shape of the curves than those obtained using sinusoidal vibration. These differences may be due to the characteristics of random vibration which produce generally higher crest factors than sinusoidal vibration. The third experiment was conducted to investigate the effect of physical body mass with 40 test participants (20 light and 20 heavy participants) using sinusoidal vibration. The results suggested that the light participants produced generally higher subjective ratings than the heavy participants. From the results it can be suggested that the equal sensation curves for steering wheel rotational vibration differ mainly due to differences of body size rather than differences of gender. The final experiments was conducted using real road signals to quantify the human subjective response to representative driving condition and to use the results to define the selection method for choosing the adequate frequency weightings for the road signals by means of correlation analysis. The final experiment was performed with 40 test participants (20 light and 20 heavy participants) using 21 real road signals obtained from the road tests. From the results the hypothesis was established that different amplitude groups may require different frequency weightings. Three amplitude groups were defined and the frequency weightings were selected for each amplitude group. The following findings can be drawn from the research: • the equal sensation curves suggest a nonlinear dependency on both the frequency and the amplitude. • the subjective responses obtained from band-limited random stimuli were steeper and the deeper in the shape of the equal sensation curves than those obtained using sinusoidal vibration stimuli. • females provided higher perceived intensity values than the males for the same physical stimulus at most frequencies. • light test participants provided higher perceived intensity than the heavy test participants for the same physical stimulus at most frequencies. • the equal sensation curves for steering wheel rotational vibration differ mainly due to differences in body size, rather than differences of gender. • at least three frequency weightings may be necessary to estimate the subjective intensity for road surface stimuli.
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Hall, Melissa A. „Characterization of Vibration Test Fixtures using Modal Analysis“. University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627664784639955.
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Park, Doh Young. „Parameter identification of salient-pole synchronous machines using the SSFR, standstill frequency response, test“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20579.pdf.
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Zhao, Sen Peng. „Design and implementation of a frequency response test system for instrument voltage transformer performance studies“. Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/design-and-implementation-of-a-frequency-response-test-system-for-instrument-voltage-transformer-performance-studies(3e65a4d8-937e-4a3d-8308-734e03f29255).html.
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Power system harmonics are always an important issue in power networks as they can cause many negative impacts, such as equipment thermal stress, on installations within power networks. Recently, with the increasing connections of power electronic devices based Renewable Energy Source (RES) and High Voltage Direct Current (HVDC) transmission applications, harmonics in power networks, especially high frequency harmonics (>50th order or 2.5 kHz) are on the rise. Currently, the majority of conventional VTs, such as Wound-type Voltage Transformers (WVT) and Capacitor Voltage Transformers (CVT), are widely installed and used in High Voltage (HV) and Extra High Voltage (EHV) power networks for voltage measurement. Since most of them were mainly designed to measure voltage with the required accuracy at the fundamental frequency (i.e. 50Hz in the UK), they are limited to measuring high frequency harmonics due to the coupling of their internal inductive and capacitive elements. To achieve high frequency harmonic measurements, voltage measurement devices with wide frequency bandwidths are required. Recently, non-conventional VTs, such as optical voltage transducers, are commercially available, which could provide accurate voltage measurements over a wide range of frequency. However, before they can be considered by any power utilities, their frequency response performances must be tested at a rated fundamental voltage with required minimum harmonic injections from 100Hz to 5 kHz. This must require a test system which should be capable of providing a rated fundamental voltage up to 400kV with controllable harmonic injections at required levels from 100Hz to 5 kHz. Therefore, the objective of this project is to design and implement such a test system in the National Grid (NG) HV laboratory at the University of Manchester. However, the design and the implementation of such a test system bring many challenges; for instance, a lack of adequate equipment and considerable power to provide the required harmonic injections above 0.5% to the test object.In this thesis, an Instrument Voltage Transformer Frequency Response (VTFR) test system with three different voltage power source designs is presented; The voltage power source designs are: (i) Design 1 is based on a single power source inductive coupling method to provide both a rated fundamental voltage and controllable harmonics; (ii) Design 2 is based on two separate voltage power sources inductive coupling method to provide both a rated fundamental voltage and controllable harmonics; and (iii) Design 3 is based on two separate voltage power sources capacitive coupling method to provide both the rated fundamental voltage and controllable harmonics. A hybrid approach, which combines the VTFR test system with both the voltage power sources Design 2 and 3, is proposed for testing the frequency response of any type of VTs at their rated fundamental voltages with 1% harmonic injections from 100Hz to 5 kHz. The proposed VTFR test system with voltage power source designs were firstly validated at a relatively low voltage of 33kV in the HV laboratory. Then three different VTFR test systems were constructed based on available equipment for testing VTs from 11kV to 400kV. An 11kV, a 33kV WVT and a 400kV WVT and a 275kV CVT were tested. The test results were analyzed, compared and discussed. The models of the test systems were also established and simulated. Simulation results were analysed, compared and discussed.
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Bodnaruc, Alexandra. „Sensory Evaluation, Frequency of Food Consumption and Metabolic Responses to a Test Breakfast Meal in Middle-Aged Adults“. Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38094.
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Sigfridsson, Simon. „Is it possible to create an indistinguishable or equal frequency response between a digital equalizer and an analog emulating equalizer plug-in?“ Thesis, Luleå tekniska universitet, Medier ljudteknik och upplevelseproduktion och teater, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-69129.
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This research examines if an indistinguishable, or equal, frequency response of a software plug-in that is emulating an analog equalizer can be reconstructed using a more standard digital equalizer such as one incorporated with a digital audio workstation (DAW). It is narrowed down to solely involve high frequency bands by analyzing the emulating plug-ins hi-shelving filters. A two-comparison forced choice ABX-test was conducted to verify the hypotheses and the results show that the difference between the original and the reconstructed hi-shelving filter was inaudible to the listening test participants. Further research and application for these findings is discussed
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Cierocka, Joanna, und Jiayue Tang. „Vibrational tests of preloaded rubber vibration isolators : A cam controlled displacement excitation“. Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-53703.
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Vibrations are very common phenomenon. It influences structures and generates acoustic noise which might be harmful to human beings. The vibration isolator was invented to reduce the effect from vibrations. However, the behavior of rubber material, which many vibration isolators are made of, is hard to predict. Consequently, vibration tests are needed to obtain the dynamic properties of rubber isolator.In this case, a six-year old LORD 2204-5 rubber isolator provided by Atlas Copco was tested. The aim of this paper is to obtain the FRF (Frequency Response Function) diagram which can describe the property of the rubber material. Moreover, the influence of aging of rubber material on the dynamic properties was studied.As the vibration test should simulate the working environment of the isolators that are both a static load from the structure and a dynamic force from the engine, a new excitation method was designed. The camshaft with the shape of an epitrochoid induced the sinusoidal signal of the isolator and the frame transferred the static load from the hydraulic machine. The artificial aging was performed in a hot air oven in 90°C for 42 hours, which according to Arrhenius equation should be equivalent to six years of natural aging. The vibration isolator was tested again after being aged.The obtained data showed that the aging process decreased the stiffness of the material. The results were corresponding with other studies regarding aging of rubber.
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Bladh, Johan. „Hydropower generator and power system interaction“. Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182188.
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After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. At the same time, an extensive reinvestment programme has commenced where many old components and apparatus are being refurbished or replaced. Introduction of new technical solutions in existing power plants requires good systems knowledge and careful consideration. Important tools for research, development and analysis are suitable mathematical models, numerical simulation methods and laboratory equipment. This doctoral thesis is devoted to studies of the electromechanical interaction between hydropower units and the power system. The work encompasses development of mathematical models, empirical methods for system identification, as well as numerical and experimental studies of hydropower generator and power system interaction. Two generator modelling approaches are explored: one based on electromagnetic field theory and the finite element method, and one based on equivalent electric circuits. The finite element model is adapted for single-machine infinite-bus simulations by the addition of a network equivalent, a mechanical equation and a voltage regulator. Transient simulations using both finite element and equivalent circuit models indicate that the finite element model typically overestimates the synchronising and damping properties of the machine. Identification of model parameters is performed both numerically and experimentally. A complete set of equivalent circuit parameters is identified through finite element simulation of standard empirical test methods. Another machine model is identified experimentally through frequency response analysis. An extension to the well-known standstill frequency response (SSFR) test is explored, which involves measurement and analysis of damper winding quantities. The test is found to produce models that are suitable for transient power system analysis. Both experimental and numerical studies show that low resistance of the damper winding interpole connections are vital to achieve high attenuation of rotor angle oscillations. Hydropower generator and power system interaction is also studied experimentally during a full-scale startup test of the Nordic power system, where multiple synchronised data acquisition devices are used for measurement of both electrical and mechanical quantities. Observation of a subsynchronous power oscillation leads to an investigation of the torsional stability of hydropower units. In accordance with previous studies, hydropower units are found to be mechanically resilient to subsynchronous power oscillations. However, like any other generating unit, they are dependent on sufficient electrical and mechanical damping. Two experimentally obtained hydraulic damping coefficients for a large Francis turbine runner are presented in the thesis.
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Zhang, Yan. „The impact of midbrain cauterize size on auditory and visual responses' distribution“. unrestricted, 2009. http://etd.gsu.edu/theses/available/etd-04202009-145923/.
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Thesis (M.S.)--Georgia State University, 2009.Title from file title page. Yu-Sheng Hsu, committee chair; Xu Zhang, Sarah. L. Pallas, committee members. Description based on contents viewed June 12, 2009. Includes bibliographical references (p. 37). Appendix A: SAS code: p. 38-53.
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Kornrumpf, Luiz Henrique Damato. „Algoritmos de tratamento de curvas para determinação de parâmetros de geradores síncronos através do ensaio de resposta em frequência utilizando metodologia com inversor de frequência“. Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-08032017-085403/.
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O ensaio de resposta em frequência em geradores síncronos vem ganhando espaço nas últimas décadas, porém o alto custo dos equipamentos empregados para realização do ensaio ainda é um empecilho, tanto para fabricantes como para consumidores finais. Este trabalho tem por objetivo complementar trabalhos anteriores, através do uso de redes neurais artificiais para identificação de padrões em ensaios realizados com equipamentos de baixo custo e baixa resolução. Através das redes neurais artificiais utilizadas é possível estimar novos pontos de ensaio sem que seja necessário um novo ensaio ou até mesmo um ensaio com equipamentos mais caros. Através de uma combinação de algoritmos de tratamento de dados, é possível a aproximação de modelos ensaiados com modelos teóricos e através desses resultados obter parâmetros elétricos dos geradores síncronos.The frequency response test on synchronous generators has been increasing in recent decades, but the high cost of equipment used for conducting the test is still a stumbling block for both manufacturers and end-consumers. This dissertation aims to complement previous work, through the use of artificial neural networks to identify patterns in tests conducted with low-cost and low-resolution equipment. Through the artificial neural networks used it is possible to estimate a new set of test points without retesting is necessary or even a more expensive assay equipments. Through a combination of data processing algorithms, the approach tested models with theoretical models is possible and through these results to obtain electrical parameters of synchronous generators.
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Cattabiani, Alessandro. „Simulation of low- and mid-frequency response of shocks with a frequency approach“. Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN012/document.
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Récemment, les industries aérospatiale et automobile sont de plus en plus intéressées par les tests virtuels, car ils accélèrent le processus de conception et ils réduisent les coûts. C’est particulièrement vrai dans le cas des industries spatiales où les maquettes sont très coûteuses car les fusées sont uniques ou produites en nombre limité. Ariane 5 (et 6 dans l'avenir) est un lanceur qui est fabriqué par CNES et Airbus DS. Pendant le lancement, la coiffe est détachée par des charges pyrotechniques quand la fusée est à une hauteur suffisante (généralement au-dessus de 100 km). Les vibrations générées par les explosions se propagent dans les coques de la fusée jusqu'à la charge utile qui peut être endommagé. Le test au sol età pleine échelle HSS3+ a été effectué par CNES et Airbus DS pour enquêter sur cette éventualité. Cette thèse développe un logiciel capable de simuler le test HSS3+ pour caractériser les efforts produits par les charges pyrotechniques et pour réduire dans l'avenir le nombre de tests réels nécessaires. La tâche est difficile car la bande de fréquence considérée est très large (jusqu'à moyenne fréquence), les efforts des explosions sont inconnus, la géométrie est complexe et la maquette est composé des coques composites et sandwich. Le logiciel appelé Transient Analysis for PYROtechnic Shocks in Shells (TAPYROSS) est basée sur la Théorie variationnelle des Rayons Complexes (TVRC) qui est une méthode de Trefftz spécifiquement développé pour analyser la moyenne fréquence. De nombreuses améliorations de la théorie et des performances ont été introduits pour étudier ce cas réel de complexité industriel. Le dernier chapitre est dédié aux comparaisons entre les données réelles et les simulations pour valider TAPYROSS et caractériser les efforts des explosionsRecently, aerospace and automotive industries are increasingly interested in virtual testing since it speeds-up the design process and reduces costs. This is particularly true in case of space industries where specimens are very costly because rockets are unique or produced in limited number. Ariane 5 (and 6 in the future) is a heavy lift launch rocket manufactured by CNES and Airbus DS. During launch the protective fairing is severed from the rocket by pyrotechnic charges once sufficient altitude is reached (typically above 100 km). Shock vibrations propagate throughout rocket shell structure to the payload which can be damaged. The HSS3+ ground full-scale test was developed by CNES and Airbus DS to investigate such eventuality. This thesis develops a software capable of simulating the HSS3+ test to characterize explosion loads and to reduce the number of future required real tests. The task is difficult since the interesting frequency band is wide (up to mid-frequency), the explosion loads are unknown, the geometry is complex, and the specimen is composed of sandwich composite shells. The software called Transient Analysis for PYROtechnic Shocks in Shells (TAPYROSS) is based on the Variational Theory of Complex Rays (VTCR) which is a Trefftz method specifically developed to analyze the mid-frequency band. Many theory and performance improvements are introduced to address this real industrial test case. At the end, comparisons between real data and simulations validate TAPYROSS and characterize explosion loads
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Chouaki, Amar. „Recalage de modèles dynamiques de structures avec amortissement“. Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0034.
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La maitrise de modèles de plus en plus complexes en mécanique est une préoccupation constante tant au niveau industriel qu'en recherche. Le problème auquel nous nous intéressons ici concerne le recalage de l'amortissement dans les modèles dynamiques de structures à partir de fonctions de réponses en fréquences. D'une manière plus générale, l'appréciation de la qualité d'un modèle est le problème central. Bien des propositions ont été faites mais peu ont une interprétation mécanique forte ; la méthode développée au LMT, depuis le début des années quatre vingt, est basée sur la notion d'erreur en relation de comportement. Après de récents développements (voir le rapport interne 150), cette approche tient compte des effets d'amortissement, et plus généralement des effets non-linéaires dus au comportement des matériaux. De plus, elle intègre tous type de résultats expérimentaux disponibles (statiques, forces et vibrations libres). L'étude présentée s'intéresse particulièrement à l'amortissement. Le recalage de l'amortissement dans le comportement dynamique des structures nécessite une représentation correcte de celui-ci. Son influence peut apparaitre tant au niveau structural qu'au niveau des liaisons entre sous-structures. La première partie de l'exposé concerne l'étude de la sensibilité de l'erreur en relation de comportement aux effets d'amortissement. Puis, dans une seconde partie, nous nous intéressons à l'influence du bruit de mesure sur le processus de recalage. Enfin, nous montrons sur différents exemples l'aptitude de la méthode à recaler l'amortissement et à l'identifier dans les liaisons entre sous-structures. Les modèles considérés sont linéaires et les résultats d'essais exploités sont de type fonctions de réponses en fréquences, incomplets et entaches de bruit de mesure.
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Schmulian, Dunay Liezel. „The prediction of hearing thresholds with dichotic multiple frequency state evoked potentials compared to an auditory brainstem response protocol“. Pretoria : [s.n.], 2002. http://upetd.up.ac.za/thesis/available/etd-10172005-155041.
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Hou, Jianlin Vispoel Walter P. „Effectiveness of the hybrid Levine equipercentile and modified frequency estimation equating methods under the common-item nonequivalent groups design“. Iowa City : University of Iowa, 2007. http://ir.uiowa.edu/etd/339.
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Gudmarsson, Anders. „Resonance Testing of Asphalt Concrete“. Doctoral thesis, KTH, Väg- och banteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155906.
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This thesis present novel non-destructive laboratory test methods to characterize asphalt concrete. The testing is based on frequency response measurements of specimens where resonance frequencies play a key role to derive material properties such as the complex modulus and complex Poisson’s ratio. These material properties are directly related to pavement quality and used in thickness design of pavements. Since conventional cyclic loading is expensive, time consuming and complicated to perform, there has been a growing interest to apply resonance and ultrasonic testing to estimate the material properties of asphalt concrete. Most of these applications have been based on analytical approximations which are limited to characterizing the complex modulus at one frequency per temperature. This is a significant limitation due to the strong frequency dependency of asphalt concrete. In this thesis, numerical methods are applied to develop a methodology based on modal testing of laboratory samples to characterize material properties over a wide frequency and temperature range (i.e. a master curve). The resonance frequency measurements are performed by exciting the specimens using an impact hammer and through a non-contact approach using a speaker. An accelerometer is used to measure the resulting vibration of the specimen. The material properties can be derived from these measurements since resonance frequencies of a solid are a function of the stiffness, mass, dimensions and boundary conditions. The methodology based on modal testing to characterize the material properties has been developed through the work presented in paper I and II, compared to conventional cyclic loading in paper III and IV and used to observe deviations from isotropic linear viscoelastic behavior in paper V. In paper VI, detailed measurements of resonance frequencies have been performed to study the possibility to detect damage and potential healing of asphalt concrete. The resonance testing are performed at low strain levels (~10^-7) which gives a direct link to surface wave testing of pavements in the field. This enables non-destructive quality control of pavements, since the field measurements are performed at approximately the same frequency range and strain level.QC 20141117
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Luo, Junxiang. „Goodness-of-fit tests for proportional odds model with GEE for ordinal categorical responses & estimating sampling frequency in pollen exposure assessment over time“. Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1150094586.
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Sousa, Murilo Hinojosa de. „Determinação de parâmetros de máquinas síncronas pelo ensaio de resposta em frequência: proposta de metodologia com inversor de frequência“. Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-27032012-120308/.
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O trabalho apresentado tem como objetivo principal propor uma metodologia para obtenção dos parâmetros da máquina síncrona, baseada em ensaio de resposta em frequência, utilizando-se de um inversor e da aplicação de técnicas numéricas de ajuste de curvas. Dedicam-se tópicos à consolidação de aspectos físicos resultantes das características construtivas das máquinas que devem ser considerados na modelagem. Também se analisam as derivações matemáticas dos modelos. Posteriormente se estudam os vários tipos de ensaios praticados para determinação dos parâmetros dos modelos apresentados. Particular ênfase é dada ao Ensaio Estático de Resposta em Frequência. São levantadas as vantagens e desvantagens da aplicação desse tipo de ensaio, suas dificuldades e limitações bem como é apresentada uma metodologia para sua execução. Por fim, o trabalho compila os resultados conseguidos com uma aplicação em bancada, onde foram utilizados equipamentos disponíveis em laboratórios didáticos de máquinas elétricas. É outro objetivo desse estudo a comparação de ensaios de resposta em frequência com ensaios tradicionais (saturação em vazio e curto-circuito permanente, curto-circuito abrupto, etc...).The presented work has as main objective to propose a methodology for obtaining the synchronous machines parameters, based on frequency response test, by means of a frequency converter and the application of numerical curve fitting routines. Topics are dedicated to the consolidation of physical aspects resulting of the machines constructive characteristics which must be considered in the modeling. Mathematical developments of the models are also studied. Thereafter, the tests that are usually performed for the determination of the synchronous machines parameters are analyzed. Particular emphasis is given to the Standstill Frequency Response Test. Positive and negative points for this specific type of test are raised. Difficulties and limitations are also defined, and a methodology for its implementation is presented. Finally, this work compiles the results achieved in a bench application, where equipment available in didactic laboratories of electric machines was used. The comparison of the Standstill Frequency Response Test with traditional tests (no-load saturation, permanent short-circuit, sudden short-circuit, etc) is also scope of this work.
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Warsido, Workamaw Paulos. „Reducing Uncertainties in Estimation of Wind Effects on Tall Buildings Using Aerodynamic Wind Tunnel Tests“. FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/939.
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Tall buildings are wind-sensitive structures and could experience high wind-induced effects. Aerodynamic boundary layer wind tunnel testing has been the most commonly used method for estimating wind effects on tall buildings. Design wind effects on tall buildings are estimated through analytical processing of the data obtained from aerodynamic wind tunnel tests. Even though it is widely agreed that the data obtained from wind tunnel testing is fairly reliable the post-test analytical procedures are still argued to have remarkable uncertainties. This research work attempted to assess the uncertainties occurring at different stages of the post-test analytical procedures in detail and suggest improved techniques for reducing the uncertainties.
Results of the study showed that traditionally used simplifying approximations, particularly in the frequency domain approach, could cause significant uncertainties in estimating aerodynamic wind-induced responses. Based on identified shortcomings, a more accurate dual aerodynamic data analysis framework which works in the frequency and time domains was developed. The comprehensive analysis framework allows estimating modal, resultant and peak values of various wind-induced responses of a tall building more accurately.
Estimating design wind effects on tall buildings also requires synthesizing the wind tunnel data with local climatological data of the study site. A novel copula based approach was developed for accurately synthesizing aerodynamic and climatological data up on investigating the causes of significant uncertainties in currently used synthesizing techniques. Improvement of the new approach over the existing techniques was also illustrated with a case study on a 50 story building.
At last, a practical dynamic optimization approach was suggested for tuning structural properties of tall buildings towards attaining optimum performance against wind loads with less number of design iterations.
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MAURI, PIERCARLO. „MODULAZIONE DELL'AROUSAL MEDIANTE LA STIMOLAZIONE ELETTRICA TRANSCRANICA A FREQUENZE RANDOM“. Doctoral thesis, Università Cattolica del Sacro Cuore, 2016. http://hdl.handle.net/10280/10724.
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Il lavoro di tesi si è focalizzato sullo studio dell’arousal come indice psicofisiologico di attivazione e sull’applicazione della metodica di stimolazione elettrica transcranica (tES) non invasiva con lo scopo di modulare tale indice. L’obiettivo è stato quello di indagare se, applicando la tES, fosse possibile migliorare la performance di soggetti giovani sani in compiti di tipo cognitivo. Il progetto di ricerca si è sviluppato in 2 studi principali per un totale di 4 esperimenti. Tali studi hanno previsto l’acquisizione e la successiva analisi sia di dati comportamentali (tempi di reazione, accuratezza), che di indici psicofisiologici (conduttanza cutanea, diametro pupillare). I risultati hanno evidenziato che è possibile modulare l’arousal con dei “bursts” di stimolazione elettrica transcranica, somministrati in concomitanza di stimoli salienti per il soggetto. Tale modulazione si è manifestata con una riduzione dei tempi di reazione ed un contemporaneo aumento della risposta di conduttanza cutanea. Questi dati supportano la possibilità di utilizzare questo protocollo in pazienti con difficoltà di attenzione o altri problemi cognitivi per aumentare l’efficacia di interventi di riabilitazione.The thesis analyzed the role of the arousal as a psychophysiological index of activation, and the application of non-invasive transcranial electrical stimulation (tES) technique with the aim to modulate this index. In this work we investigated if the application of tES could increase the performance of healthy young subjects during cognitive tasks. The thesis is based on 2 main studies for a total of 4 experiments with the recording of behavioural (reaction times, accuracy) and psychophysiological (skin conductance, pupil diameter) indeces. The results showed that it is possible to modulate arousal with bursts of tES, administered during the presentation of salient stimuli for the subject. This modulation resulted in a reduction of reaction times and an increase of the skin conductance response. These data support the possibility to use this protocol of stimulation with patients with attentional and other cognitive deficits in a rehabilitative context.
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SU, ZIH-KAI, und 蘇資凱. „Time and Frequency Response Analysis Test Platform for Woodwind Reed“. Thesis, 2015. http://ndltd.ncl.edu.tw/handle/18929362785018408531.
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碩士建國科技大學
電機工程系暨研究所
103
The work aims to reveal the design and primary test results of a time and frequency response analysis test platform for woodwind reed. Nowadays in the musical instrument market, the woodwind reed is scaled in a strength chart by testing its stiffness. In this study, a time domain and frequency response analysis test platform is presented to provide the visualized waveform and graphic spectrum of acoustic sound. The provided information can help the synthetic reed manufacturer to scrutinize the quality of a reed directly. Also, a variety of measurement data from time-domain waveform and frequency-domain response analysis can be provided to the dealers and consumers for their reference to promote reed products.
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„System Identification, Diagnosis, and Built-In Self-Test of High Switching Frequency DC-DC Converters“. Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46313.
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abstract: Complex electronic systems include multiple power domains and drastically varying dynamic power consumption patterns, requiring the use of multiple power conversion and regulation units. High frequency switching converters have been gaining prominence in the DC-DC converter market due to smaller solution size (higher power density) and higher efficiency. As the filter components become smaller in value and size, they are unfortunately also subject to higher process variations and worse degradation profiles jeopardizing stable operation of the power supply. This dissertation presents techniques to track changes in the dynamic loop characteristics of the DC-DC converters without disturbing the normal mode of operation. A digital pseudo-noise (PN) based stimulus is used to excite the DC-DC system at various circuit nodes to calculate the corresponding closed-loop impulse response. The test signal energy is spread over a wide bandwidth and the signal analysis is achieved by correlating the PN input sequence with the disturbed output generated, thereby
accumulating the desired behavior over time. A mixed-signal cross-correlation circuit is used to derive on-chip impulse responses, with smaller memory and lower computational requirement in comparison to a digital correlator approach. Model reference based parametric and non-parametric techniques are discussed to analyze the impulse response results in both time and frequency domain. The proposed techniques can extract open-loop phase margin and closed-loop unity-gain frequency within 5.2% and 4.1% error, respectively, for the load current range of 30-200mA. Converter parameters such as natural frequency (ω_n ), quality factor (Q), and center frequency (ω_c ) can be estimated within 3.6%, 4.7%, and 3.8% error respectively, over load inductance of 4.7-10.3µH, and filter capacitance of 200-400nF. A 5-MHz switching frequency, 5-8.125V input voltage range, voltage-mode controlled DC-DC buck converter is designed for the proposed built-in self-test (BIST) analysis. The converter output voltage range is 3.3-5V and the supported maximum
load current is 450mA. The peak efficiency of the converter is 87.93%. The proposed converter is fabricated on a 0.6µm 6-layer-metal Silicon-On-Insulator (SOI) technology with a die area of 9mm^2 . The area impact due to the system identification blocks including related I/O structures is 3.8% and they consume 530µA quiescent current during operation.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017
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Samarawickrama, Kasun Chamara. „Determination of impulse generator setup for transient testing of power transformers using optimization-enabled electromagnetic transient simulation“. 2014. http://hdl.handle.net/1993/23937.
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Natural lightning strikes induce impulsive overvoltages on transmission lines and its terminal equipment. These overvoltages may cause failures in insulation mechanisms of electrical devices in the power system. It is important to test the insulation strength of a device against these impulsive overvoltages. Usually, Marx generators are used to generate impulse waveforms for testing purposes. A novel approach is proposed to obtain resistor settings of a Marx generator for impulse testing of power transformers. This approach enables us to overcome most of the major challenges in the commonly used trial-and-error method, including excessive time consumption and potential damage to the transformer. The proposed approach uses the frequency response of the transformer to synthesize a circuit model. Then, a genetic algorithm based optimization-enabled electromagnetic transient simulation approach is used to obtain the resistor settings. The proposed approach is validated by a real impulse test conducted on a three phase power transformer.
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Stroebel, Deidre. „The clinical value of the auditory steady state response for early diagnosis and amplification for infants (0-8 months) with hearing loss“. Diss., 2006. http://hdl.handle.net/2263/23362.
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There has always been a need for objective tests that assess auditory function in infants, young children, and/or any patient whose development level precludes the use of behavioral audiometric techniques. Although the Auditory Brainstem Response (ABR) is seen as the ‘gold standard’ in the field of objective audiometry, it presents with its own set of limitations. The Auditory Steady State Response (ASSR) has gained considerable attention and is seen as a promising addition to the AEP ‘family’ to address some of the limitations of the ABR. The ASSR promises to estimate all categories of hearing loss (mild to profound) in a frequency specific manner. It also indicates to the possibility to validate hearing aid fittings by determining functional gain of hearing aids by determining unaided and aided ASSR thresholds. An exploratory research design was selected in order to compare unaided thresholds, obtained through the use of three different procedures – ABR, ASSR and behavioral thresholds. Aided thresholds were also obtained and compared with two procedures – the aided ASSR (measured and predicted) and aided behavioral threshold. The results indicated that both the ABR (tone burst and click) and ASSR provided a reasonable estimation of the subsequently obtained behavioral audiograms. The ASSR, however, approximated the behavioral thresholds closer than the ABR and were furthermore able to quantify hearing thresholds accurately for subjects with severe and profound hearing losses. The result indicated further that the ASSR can be instrumental in the validation process of hearing aid fittings in infants. These results demonstrated however, that the ASSR measured thresholds underestimate the aided behavioral thresholds and the aided ASSR predicted thresholds overestimate the aided behavioral thresholds. The research concluded that the ASSR is useful in estimating frequency-specific behavioral thresholds accurately in infants and validating hearing aid fittings. Until evidence is sufficient to recommend the ASSR as primary electrophysiological measure of hearing in infants, the ASSR should be used in conjunction with the ABR – following a test battery approach in the diagnostic process of hearing loss in infants. The ASSR further shows great promise in validating hearing aid fittings, but this specific application of the ASSR needs further research evidence on large groups to validate the procedure.Dissertation (Master of Communication Pathology)--University of Pretoria, 2007.
Speech-Language Pathology and Audiology
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Bosman, Riette. „Threshold estimation in normal and impaired ears using Auditory Steady State Responses“. Diss., 2003. http://hdl.handle.net/2263/29091.
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The Auditory Steady State Response (ASSR) procedure has been established as a frequency specific, objective audiologic measure, which can provide reliable thresholds to within 10 dB of the behavioral thresholds. In order for ASSR to find its place in the existing framework of audiometric procedures, the full potential of the procedure needs to be explored. The aim of this study was to determine the accuracy of monotic ASSR in estimating hearing thresholds in a group of 15 normal hearing subjects and 15 hearing-impaired subjects. A comparative research design was implemented. Indicating that results obtained in the study was compared to relevant literature where dichotic multiple ASSR was implemented. This was done in order to ascertain ASSR’s capabilities with regard to stimulus presentation methods. Monotic single ASSR predicted behavioural thresholds in the normal hearing subjects within an average of 24 dB across the frequency range (0.5, 1, 2&4 kHz). In the hearing-impaired group, ASSR thresholds more closely resembled behavioural thresholds, with an average difference of 18 dB, which is consistent with recent literature. The literature suggests that better prediction of behavioural thresholds will occur with greater degrees of hearing loss, due to recruitment. The focus in this group also centered on the accurate prediction of the configuration of the hearing loss. It was found that ASSR could reasonably accurately predict the configuration of the hearing loss. In the last instance, monotic single and dichotic multiple ASSR were compared with regard to threshold estimation and prediction of configuration of the hearing loss in the hearing-impaired group. Little difference was reported between the two techniques with regard to the estimation of thresholds in both the normal hearing and hearing impaired groups. In conclusion it was established that monotic ASSR could predict behavioural thresholds of varying degrees and configurations of hearing loss in normal and hearing-impaired subjects with a reasonable amount of accuracy. At this stage, however, more research is required to establish the clinical validity of the procedure, before it is routinely included within an objective test battery.Dissertation (M (Communication Pathology))--University of Pretoria, 2005.
Speech-Language Pathology and Audiology
Unrestricted
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Swanepoel, De Wet. „Estimating pure tone behavioural thresholds with the dichotic multiple frequency auditory steady state response compared to an auditory brainstem reponse protocol in normal hearing adults“. Diss., 2002. http://hdl.handle.net/2263/30001.
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Audiologists are reliant on objective audiometric procedures to predict auditory sensitivity in difficult-to-test populations. A technique to estimate frequency-specific hearing thresholds in a time-efficient way for difficult-to-test populations, who are unable to provide behavioural responses, has long been the hope of audiologists. The auditory brainstem response (ABR) has dominated the field of objective electrophysiological audiometry for the past three decades. Although it provides a useful method of estimating auditory sensitivity, it presents with its own set of limitations. Recently the auditory steady state response (ASSR) has demonstrated promise of addressing the limitations of the ABR as it is an evoked response uniquely suited to frequency-specific measurement. An optimised version of the ASSR, the dichotic multiple frequency (MF) ASSR, has been proposed as a time-efficient way of evaluating different frequencies simultaneously in both ears. The aim of this study was to evaluate the clinical usefulness of the dichotic MF ASSR technique for estimating pure tone behavioural thresholds at 0.5, 1, 2, and 4 kHz, compared to a 0.5 kHz tone burst and broadband click ABR protocol in a sample of normal hearing adults (56 ears). A comparative experimental research design was selected in order to compare thresholds obtained with the different procedures. The results indicated that both the dichotic MF ASSR and a 0.5 kHz tone burst and broadband click ABR protocol provided a reasonable estimation of PT behavioural thresholds in a time-efficient manner for a group of normal hearing subjects. The click ABR did, however, present with 1, 2, and 4 kHz PT threshold estimations that were almost 50 % closer than that of the dichotic MF ASSR according to the mean and normal deviation. This increased accuracy and reliability of the click ABR is however compromised by its lack of frequency-specificity. In the low frequency region of 0.5 kHz, the tone burst ABR and dichotic MF ASSR evidenced estimations of the pure tone threshold that were, on average, very similar. The tone burst ABR, however, presented with a mean threshold slightly (3 dB) closer to the pure tone threshold than the dichotic MF ASSR. The 0.5 kHz dichotic MF ASSR presented with a smaller range of normal deviation in the estimation of pure tone thresholds which suggested a more reliable measure than the 0.5 kHz tone burst ABR. The dichotic MF ASSR evaluation provided eight thresholds (4/ear) in 23 minutes on average compared to 25 minutes on average required by the ABR protocol to evaluate 4 thresholds (2/ear). This research concluded that the dichotic MF ASSR is useful for estimating frequency-specific pure tone thresholds reasonably well in a time-efficient manner but that this technique should be used in a test-battery alongside the ABR. Both the dichotic MF ASSR and the ABR comprise unique qualities that can be combined in a cross-check principle approach in order to provide complementary information that will verify results obtained with each procedure.Dissertation (MA (Communication Pathology))--University of Pretoria, 2006.
Speech-Language Pathology and Audiology
Unrestricted
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Pereira, Daniel José Ribeiro. „Análise Simulada do Impacto da Disseminação de Geração Baseada em Fontes de Energia Renovável Variável na Resposta Inercial de um Sistemas de Energia Elétrica de Teste“. Master's thesis, 2020. http://hdl.handle.net/10316/93961.
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Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e TecnologiaA estabilidade dos sistemas de energia elétrica é um dos requisitos fundamentais para o seu funcionamento fiável, eficiente e económico. Os sistemas de energia convencionais evoluíram para sistemas de grandes dimensões e altamente interligados, com maior produção de energia baseada em fontes de energia renovável e dispositivos de eletrónica de potência cada vez mais complexos, tendo um funcionamento de constante mudança. Apesar das fontes de energia renovável contribuírem para a redução da poluição a nível global, a sua disseminação cada vez mais elevada, tem criado obstáculos para o adequado comportamento dos sistemas, alguns dos quais serão abordados ao longo deste documento. Como é sabido, a inércia e a resposta inercial dos sistemas são duas componentes essenciais para o bom funcionamento dos sistemas, em termos de estabilidade de frequência, na ocorrência de eventos diversos. No entanto, o aumento de fontes baseadas em energia renovável, eólica e solar fotovoltaica, tem criado alguma preocupação aos operadores de sistema uma vez que têm menor inercia, disponibilizando, desta forma, menor resposta inercial, comparando com geradores convencionais (baseados em máquinas síncronas). Pretendeu-se com este trabalho, primeiramente analisar o impacto da disseminação das fontes de energia renováveis com baixa inercia (eólica e solar fotovoltaica) na resposta do sistema, perante eventos que causem desequilíbrios entre geração e procura (perda de geração, curto-circuitos em barramentos/linhas, perda de carga). Segundamente, utilizando as contribuições das diferentes tecnologias de geração (eólica, solar e síncrona) verificadas em 2020 e previstas para 2030 no sistema de energia elétrico português, procurou-se replicar o sistema. Desta forma, avaliou-se a sua resposta e tentou-se perceber até que ponto, o sistema atual está preparado para lidar com as alterações que vão existir com a entrada das novas normas de ligação à rede das fontes de energia renovável variável. Para tal, após ser caraterizado detalhadamente, no estado de arte, o tipo de tecnologias e requisitos regulatórios, recorreu-se à ferramenta de simulação PowerWorld para avaliar o impacto que as novas normas podem ter para o futuro do sistema. Este trabalho permitiu concluir que, apesar dos elevados níveis de disseminação de fontes de energia renovável e consequente diminuição de inércia no sistema, é possível que o sistema apresente respostas adequadas perante diversos eventos. Para além disso, também se concluiu que, apesar da inércia ser um fator importante para a estabilidade do sistema, existem outros fatores que têm de se ter em conta. Por fim, foram realizadas ações de gestão da procura para tentar melhorar a resposta do sistema perante diversos eventos.
The stability of electrical power systems is one of the fundamental requirements for their reliable, efficient and economic operation. Conventional power systems have evolved into large, highly interconnected systems, with increased energy production based on renewable energy sources and increasingly complex power electronics devices, with constantly changing operation. Although renewable energy sources contribute to the reduction of global pollution, their increasing dissemination has created obstacles to the proper behavior of systems, some of which will be discussed in this document.As it is well known, inertia and the inertial response of the systems are two essential components for its proper functioning, in terms of frequency stability, in the occurrence of diverse events. However, the increase in sources based on renewable energy, for example wind and solar photovoltaic, has created some concern for system operators since they have less inertia, thus providing less inertial response to the system, compared to conventional generators (based on synchronous machines). The purpose of this work is first, to analyze the impact of the dissemination of renewable energy sources with low inertia (wind and solar photovoltaic) in the system response to events that cause imbalances between generation and demand (loss of generation, short circuits in buss/lines, loss of load). Secondly, using the contributions of different generation technologies (wind, solar and synchronous) verified in 2020 and expected for 2030 in the Portuguese electrical power system, we tried to replicate the system. Evaluating its response and trying to understand to what extent the current system is prepared to deal with the changes that will exist with the entry of new standards for grid connection of variable renewable energy sources. To this end, after being characterized in detail, in the state of the art, the type of technologies and regulatory requirements, the PowerWorld simulation tool was used to assess the impact that the new standards may have for the future of the system. This work allowed us to conclude that, despite the high levels of dissemination of renewable energy sources and consequent decrease of inertia in the system, it is possible that the system presents adequate responses to various events. In addition, it was also demonstrated that, although inertia is an important factor for the stability of the system, there are other factors that must be considered. Finally, demand management actions were carried out to try to improve the system's response to various events.