772 research outputs found

    Analytic Modeling, Simulation and Interpretation of Broadband Beam Coupling Impedance Bench Measurements

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    In the first part of the paper a generalized theoretical approach towards beam coupling impedances and stretched-wire measurements is introduced. Applied to a circular symmetric setup, this approach allows to estimate the systematic measurement error due to the presence of the wire. Further, the interaction of the beam or the TEM wave, respectively, with dispersive material such as ferrite is discussed. The dependence of the obtained impedances on the relativistic velocity β\beta is investigated and found as material property dependent. The conversion formulas for the TEM scattering parameters from measurements to impedances are compared with each other and the analytical impedance solution. In the second part of the paper the measurements are compared to numerical simulations of wakefields and scattering parameters. In practice, the measurements have been performed for the circularly symmetric example setup. The optimization of the measurement process is discussed. The paper concludes with a summary of systematic and statistic error sources for impedance bench measurements and their diminishment strategy

    Electrical Conductivity of Brain Cortex Slices in Seizing and Non-seizing States

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    The electrical conductivity of thin living slices of mouse cerebral cortex is measured. Two only out of fifteen different attempting ways were effective. I have successfully measured the electrical conductivity of mouse brain cortex in seizing and non-seizing conditions. The first successful approach is called the van der Pauw method, where four silver-silver chloride cylindrical wire electrodes were immersed in full length at the corners of the sample. The second is a one-dimensional technique where two flat electrodes were placed on either face of the 400 micrometer thick samples. In both methods the electrodes were connected to an Agilent E4980A impedance monitor. The conductivity at 10 kHz of each sample was calculated based on measurements of injected current and potential difference between electrodes. Both approaches were validated by measuring electrical conductivities of known solutions. There were two main challenges: the small size of the sample and keeping it alive. I overcame these challenges by suitable electrodes and fast measuring equipment (Agilent E4980A LCR meter). For the one-dimensional technique I also measured the conductivity across the frequency range 20 Hz to 2 MHz. The results consistently show the mean conductivity of seizing brain tissue is significantly lower than that of non-seizing tissue at 10 kHz. Also, the conductivity of seizing slices is lower than the conductivity of non-seizing slices over the frequency range 20 Hz to 2 MHz. These results suggest a link between electrical conductivity and seizure activity. I have not investigated the causes of these differences but explanations consistent with the literature are a change in chemical environment during seizure or a reduction in gap junction connectivity

    Usporedba električkih nadomjesnih shema ljudskog zuba korištenih za mjerenje duljine korijenskog kanala

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    An accurate determination of the root canal length, which is the most critical procedure in the endodontic treatment of a tooth, is commonly performed nowadays by electronic apex locators which are based on electrical impedance measurements. In this paper tooth impedances were measured in vitro on extracted tooth in alginate material using HP 4284A LCR meter and a specially designed stalk with a micrometer for precise file positioning. In order to develop a more accurate measurement procedure human tooth was modeled by electrical equivalent circuit. Four new equivalent circuits comprising of resistors, capacitors and constant-phase elements were proposed in this paper and compared with four previously suggested circuits. Elements of equivalent circuits were determined by complex nonlinear least squares fitting using LEVM software. Different quality factors were defined to describe the fit quality of a certain equivalent circuit at each file position. The overall fitting efficiency in the region of file positions of interest was calculated as well. A detailed discussion was given on equivalent circuit parameters that can be used to measure the root canal length. Upon these results the most appropriate equivalent circuit was selected and a new measurement procedure was proposed.Točno određivanje duljine korijenskog kanala zuba, što je najkritičniji postupak u endodontskom tretmanu, se uobičajeno danas provodi elektroničkim detektorima apeksa koji se temelje na mjerenju električne impedancije. U ovoj studiji su impedancije zuba izmjerene in vitro na izvađenom zubu uronjenom u alginat. Korišten je HP 4284A LCR metar i posebno izrađeni stalak s mikrometrom za precizno pozicioniranje endodontskog instrumenta u kanalu. U svrhu razvoja točnije mjerne metode ljudski je zub modeliran električkom nadomjesnom shemom. Četiri nove nadomjesne sheme sastavljene od otpora, kapaciteta i elemenata s konstantnom fazom su predložene u ovom radu i uspoređene s četiri ranije predložene nadomjesne sheme. Elementi nadomjesnih shema su izračunati metodom kompleksnih nelinearnih najmanjih kvadrata korištenjem programa LEVM. Definirano je više faktora kvalitete kako bi se usporedilo svojstvo nadomjesnih shema da modeliraju izmjerenu impedanciju na pojedinim položajima endodontskog instrumenta u kanalu. Izračunati su i faktori kojima se uspoređuje sveukupna efikasnost nadomjesne sheme. Detaljno su objašnjeni parametri nadomjesnih shema koji se mogu koristiti za mjerenje duljine korijenskog kanala. Temeljem dobivenih rezultata odabrana je najpogodnija nadomjesna shema te je predložen novi mjerni postupak

    Usporedba električkih nadomjesnih shema ljudskog zuba korištenih za mjerenje duljine korijenskog kanala

    Get PDF
    An accurate determination of the root canal length, which is the most critical procedure in the endodontic treatment of a tooth, is commonly performed nowadays by electronic apex locators which are based on electrical impedance measurements. In this paper tooth impedances were measured in vitro on extracted tooth in alginate material using HP 4284A LCR meter and a specially designed stalk with a micrometer for precise file positioning. In order to develop a more accurate measurement procedure human tooth was modeled by electrical equivalent circuit. Four new equivalent circuits comprising of resistors, capacitors and constant-phase elements were proposed in this paper and compared with four previously suggested circuits. Elements of equivalent circuits were determined by complex nonlinear least squares fitting using LEVM software. Different quality factors were defined to describe the fit quality of a certain equivalent circuit at each file position. The overall fitting efficiency in the region of file positions of interest was calculated as well. A detailed discussion was given on equivalent circuit parameters that can be used to measure the root canal length. Upon these results the most appropriate equivalent circuit was selected and a new measurement procedure was proposed.Točno određivanje duljine korijenskog kanala zuba, što je najkritičniji postupak u endodontskom tretmanu, se uobičajeno danas provodi elektroničkim detektorima apeksa koji se temelje na mjerenju električne impedancije. U ovoj studiji su impedancije zuba izmjerene in vitro na izvađenom zubu uronjenom u alginat. Korišten je HP 4284A LCR metar i posebno izrađeni stalak s mikrometrom za precizno pozicioniranje endodontskog instrumenta u kanalu. U svrhu razvoja točnije mjerne metode ljudski je zub modeliran električkom nadomjesnom shemom. Četiri nove nadomjesne sheme sastavljene od otpora, kapaciteta i elemenata s konstantnom fazom su predložene u ovom radu i uspoređene s četiri ranije predložene nadomjesne sheme. Elementi nadomjesnih shema su izračunati metodom kompleksnih nelinearnih najmanjih kvadrata korištenjem programa LEVM. Definirano je više faktora kvalitete kako bi se usporedilo svojstvo nadomjesnih shema da modeliraju izmjerenu impedanciju na pojedinim položajima endodontskog instrumenta u kanalu. Izračunati su i faktori kojima se uspoređuje sveukupna efikasnost nadomjesne sheme. Detaljno su objašnjeni parametri nadomjesnih shema koji se mogu koristiti za mjerenje duljine korijenskog kanala. Temeljem dobivenih rezultata odabrana je najpogodnija nadomjesna shema te je predložen novi mjerni postupak

    Design Evaluation of a High Voltage High Frequency Pulse Transformer

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    Unlike commonly used regular transformers, high voltage, high frequency, pulsed transformers are generally represented in special purpose applications. This often means that these electrical devices must be tailored in accordance with the specic requirements of the project. The pulse transformer under analysis in this thesis is a prototype machine variation of which will serve as an essential part of klystron feeder system at the European Spallation Source. In the given application hundreds of pulse transformers will be required in order to supply power for the particle accelerator. The devices will be be integrated into high voltage, high frequency, pulsed power modules. The importance of careful analysis of the prototype system can therefore not be stressed enough. Throughout this thesis work the reliability and functionality of the prototype pulse transformer are examined closely with help of analytic methods, computer aided simulation and laboratory analysis. The design is evaluated in terms of several important qualities such as low voltage drop, sucient rise times and ability to operate without occurrence of unwanted high voltage phenomena. Both electromagnetic and mechanic aspects are included into the study. As the result of the performed work, an evaluation conclusion is presented together with possible improvements of the current design. Aim of the study is to provide a verication as well as present possible alternatives for the transformer system design

    ELECTRICAL IMPEDANCE SPECTROSCOPY AND TOMOGRAPHY: APPLICATIONS ON PLANT CHARACTERIZATION

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    World population will grow to 9.6 billion by 2050 and global food production needs to be increased by 70% to feed the increased population. Hence, better insight into plant physiology can impart better quality in fruits, vegetables, and crops, and eventually contribute to food security and sustainability. In this direction, this thesis utilizes electrical sensing technology, electrical impedance spectroscopy (EIS) and tomography (EIT), for better understanding and characterization of a number of physiological and structural aspects of the plant. It investigates the dehydration process in onion and ripening process in avocado by EIS, and perform 3D structural imaging of root by EIT. The thesis tracks and analyzes the dynamics of natural dehydration in onion and also assesses its moisture content using EIS. The work develops an equivalent electrical circuit that simulates the response of the onion undergoing natural drying for a duration of three weeks. The developed electrical model shows better congruence with the experimental data when compared to other conventional models for plant tissue with a mean absolute error of 0.42% and root mean squared error of 0.55%. Moreover, the study attempts to find a correlation between the measured impedance data and the actual moisture content of the onions under test (measured by weighing) and develops a simple mathematical model. This model provides an alternative tool for assessing the moisture content of onion nondestructively. The model shows excellent correlation with the ground truth data with a deterministic coefficient of 0.977, root mean square error of 0.030 and sum of squared error of 0.013. Next, the thesis presents an approach that will integrate EIS and machine learning technique that allows us to monitor ripening degree of avocado. It is evident from this study that the impedance absolute magnitude of avocado gradually decreases as the ripening stages (firm, breaking, ripe and overripe) proceed at a particular frequency. In addition, Principal component analysis shows that impedance magnitude (two principal components combined explain 99.95% variation) has better discrimination capabilities for ripening degrees compared to impedance phase angle, impedance real part, and impedance imaginary part. The developed classifier utilizes two principal component features over 100 EIS responses and demonstrate classification over firm, breaking, ripe and overripe stages with an accuracy of 90%, precision of 93%, recall of 90%, f1-score of 90% and an area under ROC curve (AUC) of 88%. Later on, this thesis presents the design, development, and implementation of a low-cost EIT system and analyzes root imaging as well. The designed prototype consists of an electrode array system, an Impedance analyzer board, 2 multiplexer units, and an Arduino. The Eval-Ad5933-EBZ is used for measuring the bio-impedance of the root, and two CD74HC4067 Multiplexers are used as electrode switching unit. Measuring and data collecting are controlled by the Arduino, and data storage is performed in a PC. By performing Finite Element Analysis and solving forward and inverse problem, the tomographic image of the root is reconstructed. The system is able to localize and build 2D and 3D tomographic image of root in a liquid medium. This proposed low-cost and easy-to-access system enables the users to capture the repetitive, noninvasive and non-destructive image of a plant root. Furthermore, the study proposes a simple mathematical model, based on ridge regression, which can predict root biomass from EIT data nondestructively with an accuracy of more than 93%. Thus, this study offers plant scientists and crop consultants the ability to better understand plant physiology nondestructively and noninvasively

    ELECTRICAL IMPEDANCE SPECTROSCOPY AND TOMOGRAPHY: APPLICATIONS ON PLANT CHARACTERIZATION

    Get PDF
    World population will grow to 9.6 billion by 2050 and global food production needs to be increased by 70% to feed the increased population. Hence, better insight into plant physiology can impart better quality in fruits, vegetables, and crops, and eventually contribute to food security and sustainability. In this direction, this thesis utilizes electrical sensing technology, electrical impedance spectroscopy (EIS) and tomography (EIT), for better understanding and characterization of a number of physiological and structural aspects of the plant. It investigates the dehydration process in onion and ripening process in avocado by EIS, and perform 3D structural imaging of root by EIT. The thesis tracks and analyzes the dynamics of natural dehydration in onion and also assesses its moisture content using EIS. The work develops an equivalent electrical circuit that simulates the response of the onion undergoing natural drying for a duration of three weeks. The developed electrical model shows better congruence with the experimental data when compared to other conventional models for plant tissue with a mean absolute error of 0.42% and root mean squared error of 0.55%. Moreover, the study attempts to find a correlation between the measured impedance data and the actual moisture content of the onions under test (measured by weighing) and develops a simple mathematical model. This model provides an alternative tool for assessing the moisture content of onion nondestructively. The model shows excellent correlation with the ground truth data with a deterministic coefficient of 0.977, root mean square error of 0.030 and sum of squared error of 0.013. Next, the thesis presents an approach that will integrate EIS and machine learning technique that allows us to monitor ripening degree of avocado. It is evident from this study that the impedance absolute magnitude of avocado gradually decreases as the ripening stages (firm, breaking, ripe and overripe) proceed at a particular frequency. In addition, Principal component analysis shows that impedance magnitude (two principal components combined explain 99.95% variation) has better discrimination capabilities for ripening degrees compared to impedance phase angle, impedance real part, and impedance imaginary part. The developed classifier utilizes two principal component features over 100 EIS responses and demonstrate classification over firm, breaking, ripe and overripe stages with an accuracy of 90%, precision of 93%, recall of 90%, f1-score of 90% and an area under ROC curve (AUC) of 88%. Later on, this thesis presents the design, development, and implementation of a low-cost EIT system and analyzes root imaging as well. The designed prototype consists of an electrode array system, an Impedance analyzer board, 2 multiplexer units, and an Arduino. The Eval-Ad5933-EBZ is used for measuring the bio-impedance of the root, and two CD74HC4067 Multiplexers are used as electrode switching unit. Measuring and data collecting are controlled by the Arduino, and data storage is performed in a PC. By performing Finite Element Analysis and solving forward and inverse problem, the tomographic image of the root is reconstructed. The system is able to localize and build 2D and 3D tomographic image of root in a liquid medium. This proposed low-cost and easy-to-access system enables the users to capture the repetitive, noninvasive and non-destructive image of a plant root. Furthermore, the study proposes a simple mathematical model, based on ridge regression, which can predict root biomass from EIT data nondestructively with an accuracy of more than 93%. Thus, this study offers plant scientists and crop consultants the ability to better understand plant physiology nondestructively and noninvasively

    Nonlinear electronic conductivity in lithium niobate domain walls

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    Applying ferroelectric materials for nanoelectronic circuits opens, next to exploiting completely new functionalities, the possibility of improving resource efficiency in electronic circuits. Due to its defined and easy-to-manipulate domain structure, lithium niobate (LiNbO3, LNO) is a promising candidate to realize such circuits. As a prerequisite, a detailed understanding of the underlying conduction mechanisms is required for a future large scale application. The main field of attention of this thesis is the domain wall conductivity in lithium niobate, investigated with temperature-dependent dc conductivity measurements as well as higher-harmonic current analysis under alternating-voltage excitation. Thereby the parameters of the electric field are of special interest, comprising the static dc field and both the amplitude and the frequency of the ac excitation voltage. Prior to the analysis of the experimental results, the setups are characterized in depth and a theoretical framework to calculate higher-harmonic current contributions generated by non-ohmic conduction models is derived. In case of high static offset voltages, an ohmic-like conductance is observed, which is ascribed to the intrinsic conductivity of the domain wall. For lower static offset fields, a diode-like current-voltage characteristic is found, originating from the junction of the domain wall and the metallic contact electrode. The results are compared to measurements at an industrial Schottky diode taken under the same conditions. Based on the theory of metal-semiconductor junctions, the effective donor density within the conducting domain wall is estimated to be of the order of 1019/cm3, which agrees well with theoretical calculations in the literature. An equivalent circuit based on two diodes and two resistors is proposed to model the observed nonohmic conductance. For all experimental techniques, a good agreement between this model and the experimental data is observed, proving especially the non-ohmic conductivity to be of Schottky-type

    On Mechanical and Electrical Coupling Determination at Piezoelectric Harvester by Customized Algorithm Modeling and Measurable Properties

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    Piezoelectric harvesters use the actuation potential of the piezoelectric material to transform mechanical and vibrational energies into electrical power, scavenging energy from their environment. Few research has been focused on the development and understanding of the piezoelectric harvesters from the material themselves and the real piezoelectric and mechanical properties of the harvester. In the present work, the authors propose a behavior real model based on the experimentally measured electromechanical parameters of a homemade PZT bimorph harvester with the aim to predict its Vrms output. To adjust the harvester behavior, an iterative customized algorithm has been developed in order to adapt the electromechanical coupling coefficient, finding the relationship between the harvester actuator and generator behavior. It has been demonstrated that the harvester adapts its elongation and its piezoelectric coefficients combining the effect of the applied mechanical strain and the electrical behavior as a more realistic behavior due to the electromechanical nature of the material. The complex rms voltage output of the homemade bimorph harvester in the frequency domain has been successfully reproduced by the proposed model. The Behavior Real Model, BRM, developed could become a powerful tool for the design and manufacturing of a piezoelectric harvester based on its customized dimensions, configuration, and the piezoelectric properties of the smart materials.This research was funded by the Basque Government, grant number KK-2021/00082-µ4IIoT, and by the European Commission, grant number 869884- RECLAIM

    A Model for Axial Magnetic Bearings Including Eddy Currents

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    This paper presents an analytical method of modelling eddy currents inside axial bearings. The problem is solved by dividing an axial bearing into elementary geometric forms, solving the Maxwell equations for these simplified geometries, defining boundary conditions and combining the geometries. The final result is an analytical solution for the flux, from which the impedance and the force of an axial bearing can be derived. Several impedance measurements have shown that the analytical solution can fit the measured data with a precision of approximately 5%
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