Search

In 1873, J. C. Maxwell derived relations for current density and current in a solitary long cylindrical conductor supplied with variable current. According to Maxwell, the current density in a conductor increases towards the conductor surface. This phenomenon is called the skin effect. The skin effect affects in particular the inductance of a line formed by one or several long parallel conductors. A number of papers have been published regarding the skin effect and its effect on inductance. Another phenomenon, closely related to the skin effect, is the proximity effect, which refers to the dependence of the current density in a conductor on the proximity of other conductors through which a time-variable current is flowing. Many published papers deal with the calculation of current density in two conductors, using the method for calculating current density in a solitary conductor. All the phenomena given above can be analysed and quantitatively described based on the knowledge of current density in conductors, and therefore the method for calculating current density in a group of conductors is of fundamental significance. It follows form the analysis performed that the skin effect is not a general characteristic of current density in long conductors, except for in the solitary conductor. This conclusion affects the knowledge of the phenomena associated with the skin effect., V roce 1873 J. C. Maxwell odvodil vzorce pro proudovou hustotu a proud v osamělém dlouhém válcovém vodiči napájeném proměnným proudem. Podle Maxwella se proudová hustota zvětšuje směrem k povrchu vodiče. Tento jev se nazývá povrchový jev. Povrchový jev ovlivňuje zejména indukčnost vedení tvořeného dvěma dlouhými rovnoběžnými vodiči. Dalším jevem, těsně spjatým s povrchovým jevem je jev blízkosti, který označuje závislost proudové hustoty ve vodiči na blízkosti jiných vodičů jimiž prochází proud závislý na čase. Mnoho publikovaných článků pojednává o výpočtu proudové hustoty ve dvou vodičích pomocí metody výpočtu proudové hustoty v osamělém vodiči. Všechny tyto výše uvedené jevy mohou být analyzovány a kvantitativně popsány pomocí znalosti proudové hustoty ve vodičích a proto má zásadní význam metoda výpočtu proudové hustoty ve skupině vodičů. Z provedené analýzy plyne, že povrchový jev není obecnou charakteristikou proudové hustoty v dlouhých vodičích, s výjimkou osamělého vodiče. Tento závěr ovlivňuje poznatky o jevech spojených s povrchovým jevem.

This paper demonstrates an equivalent circuit model for large scale WPT system with multiple receivers. Manyarticles have shown the method for determining optimum load impedance at receiver and power distribution in multiplereceiverenvironment. These analysis indicate requirement of an equivalent circuit when a transmitter side and receiver sidesare coupled. This paper newly assumes that transmitter side is large scale so that equivalent circuit have to be combinationof concentrated/distributed constant. Proposed model is experimentally investigated under the assumption that single parallelline feeder coupled with multiple receiver with different location., 2019 Asian Wireless Power Transfer Workshop

This paper aims at a new assessment to investigate the effect of a test setup on the input impedance of cables. The test setup includes a vertical reference plane connected to a horizontal ground plane. A connector is screwed into the vertical plane. The connector from one side is connected to a measurement device and from another side, it is connected to a cable. To assess the effect of the setup on connectors, the SMA connector and the end-launch connector are connected to the setup separately and the input impedance of the setup is measured. The results suggest that the vertical plane and the connectors have a significant impact on the test setup up to 6 GHz. This impact can be observed even by adding a 1m wire to the test setup.

Drude's description of the response of low-temperature gallium arsenide to optical pulse excitation is used to evaluate the components of a time-domain Norton equivalent circuit of a photoconductive antenna (PCA) source. The saturation of the terahertz (THz) radiated power occurring at large optical excitation levels was previously associated by the scientific community to radiation and charge screening of the bias. With the present circuit, we are able to model accurately the measured saturation as only due to the EM feedback from the antenna to the bias. The predicted THz radiated power is shown to match very accurately the measurements when the circuit is combined with an accurate description of the experimental conditions and the modeling of the THz quasi-optical (QO) channel., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Tera-Hertz Sensing, EKL Processing, Electronics

From the aspect of corrosion stability, aluminum alloys can be divided into corrosion stable and corrosion unstable alloys. However, it should be emphasized that the corrosion properties themselves are not the only relevant factor for their use, because the use is also influenced by mechanical characteristics. In general, these properties are greatly influenced by the chemical composition, which affects the structure, and the main factor that influences the corrosion stability is presence and concentration of alloying elements. The aim of this work was to show the corrosion characteristics of alloys of the Al-Mg system, which is a continuation of previous work of the authors that was conducted in this area. Corrosion characteristics of aluminum were examined using electrochemical impedance spectroscopy during exposure in an aqueous solution of 3 wt. % NaCl. The obtained data were analyzed by equivalent electrical circuits of different configurations with a special discussion related to the appearance and type of oxide layer that is formed due to the effect of the corrosive environment on the sample and the behavior of the samples in the corrosive environment. Equivalent circuits describe the impedance responses well, and the values of the circuit parameters correspond to the proposed model of physical-chemical changes during the corrosion process of the investigated systems. EIS data indicated considerably greater corrosion resistance aluminum with higher Mg content. The corrosion processes on Al alloys with higher Mg content are subjected to more pronounced diffusion limitations in comparison to the processes below the passive oxide film, as a consequence of the formation of a highly compact protective coating. The results show that the addition of Mg is an effective way to improve corrosion resistance for aluminum.

This article presents a solution methodology for the estimation of parameters of single-phase transformers considering the measurements of voltage and current, for which a non-linear optimization model is used. This model is based on minimizing the mean square error between the measured and calculated voltage and current variables. This nonlinear programming model is solved by implementing the Salp swarm optimization algorithm. The results obtained show that the proposed optimization method allows reducing the error between the estimation of the measured and calculated variables; in addition, the proposed optimization method improves the results presented by other optimization methods reported in the specialized literature. All the simulations were performed in the MATLAB programming environment., En este artículo se presenta una metodología de solución para la estimación de parámetros de transformadores monofásicos considerando las mediciones de tensión y corriente; para ello se emplea un modelo de optimización no lineal. Este modelo se basa en minimizar el error cuadrático medio entre las variables de tensión y corriente medidas y calculadas. Este modelo de programación no lineal se resuelve mediante la implementación del algoritmo de optimización de las salpas. Los resultados obtenidos demuestran que el método de optimización propuesto permite reducir el error entre la estimación de las variables medidas y calculadas; además, el método de optimización propuesto mejora los resultados presentados por otros métodos de optimización reportados en la literatura especializada. Todas las simulaciones se realizaron en el entorno de programación MATLAB.

The fifth generation of mobile communication poses challenges in the form of increased data volume, network scalability and efficient network operation. An important part in meeting these requirements is the use of the mm-wave frequency range, enabling the use of a wide bandwidth and therefore the desired high-data rates. However, a challenging aspect of mm-wave communication lies in the efficient generation of RF power. In fact, currently reported power amplifiers are unable to reach the required output power for commercial applications. A typical way to increase the available power is to combine the signal from multiple sources using a power combiner. Power combiners in the mm-wave frequency range have been investigated for many years, but typical problems that occur are area occupation and insertion losses that grow directly with the number of inputs...., Tera-Hertz Sensing

This thesis outlines the development and application of a battery management system for a small electric vehicle, and the hardware required to test and validate these systems. The project applies state-of-the-art methods for estimating the remaining charge of a battery pack in a real-world environment. In doing so, the limitations of existing estimation methods are identified and addressed.

We present a general analysis to describe nonsquare artificial dielectric layers (ADLs). Closed-form expressions for the equivalent layer impedance are given for generic plane-wave incidence, assuming that the ADLs have different geometrical parameters in the {x}-and {y}-directions. The analytical expressions account for the interaction between the layers due to higher order Floquet modes, thus remain valid for arbitrarily small electrical distance between layers. Such nonsquare geometries allow the design of artificial anisotropic slabs with azimuth-dependent effective refractive index. As an example for an application, the equivalent model is used to design the superstrate of a double-slot antenna, with independent pattern shaping in the two main planes., Accepted author manuscript, Tera-Hertz Sensing

Precision design of narrow-beam or shaped-beam slot arrays in reduced-height, dielectric-filled or substrate-integrated waveguide demands accurate control over the excitation of individual elements. Conventional design methods are restricted by assumptions pertaining to the symmetry of slot fields and the simplified shunt-element equivalent circuit for slots. In this paper, we present a detailed formulation of a design technique that accommodates asymmetric slots fields and uses the full T-network equivalent circuit for each slot. The method is efficient and capable of rapid design of arrays of arbitrary dimension.

Self-crosslinking Water-based acrylic resins are currently widely used in the formulation of paints for the protection of materials exposed to atmospheric corrosion. These resins, given their "selfcrosslinking" designation, initiate their crosslinking process once they are applied on a previously prepared surface. It is expected that with time they will increase their protection, due to their continuing self-crosslinking mechanism. In this work, metallic plates coated with these resins were evaluated under simulated salt neutral spray (ASTM B117). The coating degradation processes were monitored by Electrochemical Página 3 de 15 Impedance Spectroscopy (EIS) and visual inspection, according to ASTM D610 and ASTM D714, aiming to identify and quantify the appearance of blistering and corrosion products. The results revealed rapid drops in pore resistance (Rpo) for systems exposed to neutral salt spray (NSS), salineacidic or acidified conditions, which coincided with the formation of blisters. On the contrary, the systems in the wet chamber showed an increase in the Rpo, which evidences from an electrical point of view a greater opposition to the passage of current. Notwithstanding, still the appearance of blisters on the coated surfaces was observed., Las resinas acrílicas base agua del tipo autoreticulables son usadas actualmente en la formulación de pinturas usadas para la protección de materiales expuestos a la corrosión atmosférica. Estas resinas, dada su denominación de “autoreticulables”, inician su proceso de “entrecruzamiento”, una vez son aplicadas sobre la superficie previamente preparada. Se espera que con el tiempo incrementen su protección, debido a su mecanismo de curado (autoreticulación) Láminas metálicas recubiertas con estas resinas fueron sometidas a la evaluación bajo condiciones simuladas de Niebla Salina Neutra (ASTM B117), Niebla Salino Ácida (ASTM G85 A1) y Cámara Húmeda (ASTM D4585). Los procesos de degradación del recubrimiento fueron monitoreados mediante pruebas de Espectroscopia de Impedancia Electroquímica (EIS) y, asimismo, se realizaron observaciones visuales, de acuerdo con las normas ASTM D714 y ASTM D610, buscando identificar y cuantificar la aparición de ampollas y productos de corrosión, correspondientemente. Los resultados revelaron que, para la evaluación en cámara salina estándar (NSS) y salino-ácida o acidulada, las rápidas caídas de resistencia de poros (Rpo) para el sistema de recubrimientos eran coincidentes con la formación de ampollas. Contrario a lo anterior, los resultados en la cámara húmeda mostraron incrementos en la Rpo, lo que evidencia desde el punto de vista eléctrico una mayor oposición al paso de corrientes, no obstante, se observó la aparición efectiva de ampollas sobre la superficie recubierta.

The extent of the cell voltage hysteresis observed in polarization curves of PEM fuel cells and the origins causing this effect are investigated by performing experimental polarization curves with different dwell times for a 50 cm2 PEM fuel cell. Electrochemical Impedance Spectroscopy measurements are carried out in order to determine the relative contributions of the different polarizations (ohmic, activation, and concentration polarization). Equivalent circuits were obtained from the impedance spectra, where the interpretation of the circuit parameters enabled the analysis of the origin and extent of the cell voltage hysteresis. It was identified that the cause of the cell voltage hysteresis is actually dominated by the changes in the concentration polarization at low current densities, and by the changes in the activation polarization at high current densities. The cell ohmic resistance (and consequently the membrane hydration) presents a minor effect on the cell voltage hysteresis. The effect of the dwell time in the cell voltage hysteresis (with values ranging from 15 to 25 mV) presents a mixed trend, with an initial decrease for increasing dwell times from 120 to 600 s, and a later increase and a final almost constant hysteresis for longer dwell times.

Continuous quantitative monitoring of the change in mineral content during the bone healing process is crucial for efficient clinical treatment. Current radiography-based modalities, however, pose various technological, medical, and economical challenges such as low sensitivity, radiation exposure risk, and high cost/instrument accessibility. In this regard, an analytical approach utilizing electrochemical impedance spectroscopy (EIS) assisted by machine learning algorithms is developed to quantitatively characterize the physico-electrochemical properties of the bone, in response to the changes in the bone mineral contents. The system is designed and validated following the process of impedance data measurement, equivalent circuit model designing, machine learning algorithm optimization, and data training and testing. Overall, the systematic machine learning-based classification utilizing the combination of EIS measurements and electrical circuit modeling offers a means to accurately monitor the status of the bone healing process.

publisher

The time evolution of voltages and currents in a pulsed photo conductive antenna (PCA) source is evaluated resorting to a rigorous procedure that stems from semiconductor physics first, to define the phenomena involved in the generation of the photocurrent, and then relies on an equivalent circuit in time domain, providing a direct estimation of the power generated by the PCA as well as its spectral distribution. The circuit model is validated via a campaign of measurements of standard PC antenna sources. The saturation phenomena in the THz radiated power occurring at large optical excitation levels, previously observed by the scientific community and associated to different phenomena, are accurately predicted by the present method, which ascribe their main cause to the feedback from the antenna: indeed, the electromagnetic field generated by the device tend to reduce the strength of the forcing field used to accelerate the photo-carriers., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Tera-Hertz Sensing, EKL Processing, Electronics

This work shows the results obtained from studying the influence of equivalent circuit resistances on three-phase induction motors. The stator resistance, rotor resistance, and iron losses resistance affect the different motor operating variables (output power, current, speed, power factor, starting ratios, and maximum torque). These influences have been quantified, paying particular attention to the losses affected and their impact on efficiency. The study carried out does not apply optimization techniques. It evaluates the different influences of the equivalent circuit’s different resistances on its operation by evaluating applicable constructive modifications concerning available motors. The work has been limited to three-phase induction motors up to 50 kW and low voltage, with the nominal powers of the selected motors being 0.25 kW, 1.5 kW, 7.5 kW, 22 kW, and 45 kW. The tools used to carry out the study are analyzing the equivalent circuit and the simulation of the electromagnetic structure using a finite-element program. The variations proposed in each resistance for all the motors studied is not purely theoretical, as it is based on applying feasible constructive modifications, appropriately analyzed and simulated. These modifications are the variation of the conductor diameter in the stator coils, the change of the section of the rotor cage, and the selection of different ferromagnetic steel types. © 2021 by the authors. Licensee MDPI, Basel, Switzerland, Peer Reviewed, Postprint (published version)

We present here the first impedance-based characterization of the differentiation process of two human mesencephalic fetal neural stem lines. The two dopaminergic neural stem cell lines used in this study, Lund human mesencephalic (LUHMES) and human ventral mesencephalic (hVM1 Bcl-XL), have been developed for the study of Parkinsonian pathogenesis and its treatment using cell replacement therapy. We show that if only relying on impedance magnitude analysis, which is by far the most usual approach in, e.g., cytotoxicity evaluation and drug screening applications, one may not be able to distinguish whether the neural stem cells in a population are proliferating or differentiating. However, the presented results highlight that equivalent circuit analysis can provide detailed information on cellular behavior, e.g. simultaneous changes in cell morphology, cell-cell contacts, and cell adhesion during formation of neural projections, which are the fundamental behavioral differences between proliferating and differentiating neural stem cells. Moreover, our work also demonstrates the sensitivity of impedance-based monitoring with capability to provide information on changes in cellular behavior in relation to proliferation and differentiation. For both of the studied cell lines, in already two days (one day after induction of differentiation) equivalent circuit analysis was able to show distinction between proliferation and differentiation conditions, which is significantly earlier than by microscopic imaging. This study demonstrates the potential of impedance-based monitoring as a technique of choice in the study of stem cell behavior, laying the foundation for screening assays to characterize stem cell lines and testing the efficacy epigenetic control.

Electrical and Telecommunication Engineering is nowadays playing a fundamental role in biomedical research and its applications. Microwave and Antenna Group at EPFL are working resolutely to help in this vital field for society, as it has been unfortunately proven once again during the sanitary crisis caused by the COVID-19 outbreak in the last months. With this final degree thesis, I have tried to make my humble contribution to this broad topic, focusing on the field of Radio Frequency Identification (RFID). To do so, the main objective of this work was to study the frequency splitting phenomenon and verify whether it is plausible to identify a 2mm electrically small passive loop antenna using another active antenna of the same characteristics. It has been found that for close distances with no dielectric boundaries (up to 2.5mm for this configuration), analysing the frequency splitting phenomenon is an effective way to correctly confirm the presence of the passive antenna (or transponder), and it is even possible to determine its distance relative to the active antenna (or reader). When a dielectric environment is added, frequency splitting can be detected as well. However, in this case, the detectable distance range decreases due to the high relative permittivity conditions. These findings lead to a feasible way to implement a low-complexity 1-bit transponder for short-range applications., La Ingeniería Eléctrica y de Telecomunicaciones tiene actualmente un papel fundamental en la investigación biomédica y sus aplicaciones. El Grupo de Microondas y Antenas de la EPFL trabaja decididamente para ayudar en este campo vital para la sociedad, como ha sido lamentablemente demostrado una vez más durante la crisis sanitaria provocada por la pandemia de COVID-19 en los últimos meses. Con esta tesis de fin de grado, he tratado de hacer mi humilde aportación a este amplio tema, centrándome en el campo de la Identificación por Radiofrecuencia (RFID). Para ello, el objetivo principal de este trabajo ha sido estudiar el fenómeno de división frecuencial (conocido en inglés como frequency splitting) y verificar si es posible identificar una antena pasiva eléctricamente pequeña del tipo espira elemental de 2 mm utilizando otra antena activa de las mismas características. Se ha encontrado que para distancias cortas sin condiciones de dieléctrico (hasta 2.5 mm para esta configuración), analizar el fenómeno de división frecuencial es una forma efectiva de confirmar correctamente la presencia de la antena pasiva (o transpondedor), e incluso es posible determinar su distancia relativa a la antena activa (o lector). Cuando se añade un entorno dieléctrico, también se puede detectar la división frecuencial, pero en distancias más limitadas para condiciones de permitividad relativa alta. Estos hallazgos conducen a una forma viable de implementar un transpondedor de 1 bit de baja complejidad para aplicaciones de corto alcance., L'Enginyeria Elèctrica i de Telecomunicacions té actualment un paper fonamental en la recerca biomèdica i les seves aplicacions. El Grup de Microones i Antenes (MAG) de l'EPFL treballa decididament per tal d'ajudar en aquesta àrea vital per al conjunt de la societat, com ha estat malauradament demostrat una vegada més durant la crisi sanitària derivada de la pandèmia causada pel COVID-19 els darrers mesos. Amb aquest treball de fi de grau, he intentat fer la meva modesta aportació a aquest ampli tema, centrant-me en el camp de la Identificació per Ràdio Freqüència (RFID). A tal efecte, el principal objectiu d'aquest treball ha estat estudiar el fenomen de la divisió freqüencial (conegut en anglès com frequency splitting) i verificar si és possible identificar una antena elèctricament petita passiva del tipus espira elemental de 2mm de diàmetre mitjançant una altra antena activa de les mateixes característiques. S'ha comprovat que per a distàncies properes sense condicions de dielèctric (fins a 2,5mm en aquesta configuració), analitzar el fenomen de divisió freqüencial és una manera eficaç de confirmar correctament la presència de l'antena passiva (o transponedor), i és fins i tot possible determinar-ne la distància respecte a l'antena activa (o lector). Quan s'hi afegeix un entorn dielèctric, el fenomen de la divisió freqüencial pot ser detectat també, encara que en distàncies més limitades en condicions de permitivitats relatives elevades. Aquests resultats porten a una implementació viable d'un detector d'un bit de baixa complexitat per a aplicacions de curt abast.

We present here the first impedance-based characterization of the differentiation process of two human mesencephalic fetal neural stem lines. The two dopaminergic neural stem cell lines used in this study, Lund human mesencephalic (LUHMES) and human ventral mesencephalic (hVM1 Bcl-XL), have been developed for the study of Parkinsonian pathogenesis and its treatment using cell replacement therapy. We show that if only relying on impedance magnitude analysis, which is by far the most usual approach in, e.g., cytotoxicity evaluation and drug screening applications, one may not be able to distinguish whether the neural stem cells in a population are proliferating or differentiating. However, the presented results highlight that equivalent circuit analysis can provide detailed information on cellular behavior, e.g. simultaneous changes in cell morphology, cell-cell contacts, and cell adhesion during formation of neural projections, which are the fundamental behavioral differences between proliferating and differentiating neural stem cells. Moreover, our work also demonstrates the sensitivity of impedance-based monitoring with capability to provide information on changes in cellular behavior in relation to proliferation and differentiation. For both of the studied cell lines, in already two days (one day after induction of differentiation) equivalent circuit analysis was able to show distinction between proliferation and differentiation conditions, which is significantly earlier than by microscopic imaging. This study demonstrates the potential of impedance-based monitoring as a technique of choice in the study of stem cell behavior, laying the foundation for screening assays to characterize stem cell lines and testing the efficacy epigenetic control.

An air-core transformer is a suitable device for megahertz-class power converters. This letter presents an equivalent circuit of a fabricated interleaved air-core toroidal transformer. In order to determine the modeling parameter of the transformer, the electrical characteristics are discussed on the basis of the frequency responses measured from 0.1 to 110MHz. As a result, it is found that the fabricated transformer is dominated by the mutual capacitance in addition to the self- and mutual inductance. The proposed equivalent circuit is distributed parameter model. This is derived from analogy with the coupled transmission lines. The equivalent circuit shows an excellent agreement with the experiment. These results conclude that the importance of the mutual capacitance to be implemented as a distributed parameter.

Este artículo propone un nuevo circuito equivalente para modelar supercondensadores. El circuito propuesto es un arreglo de circuitos RC serie descritos por ecuaciones diferenciales fraccionarias conformables. Se implementa un algoritmo de identificación de parámetros del circuito equivalente, que utiliza como entrada datos experimentales. Los resultados de validación obtenidos muestran que un circuito equivalente que emplea el operador conformable puede ser utilizado para modelar el comportamiento real del supercondensador., This paper proposes a new equivalent circuit to model supercapacitors. The proposed circuit is an array of RC branches described by differential conformable fractional derivative equations. A parameter identification algorithm based on experimental data is implemented. Validation results using experimental data show that the proposed equivalent circuit can be used to model the real behavior of the supercapacitors.

Применение объемных полосково-щелевых переходов для реализации устройств бесконтактной частотно-селективной передачи СВЧ-сигнала является актуальным. Это обусловлено компактностью объемных полосково-щелевых (далее – ОПЩ) переходов, достигаемой многослойным размещением функциональных частей, а также частотно-селективными характеристиками их электрических параметров. При этом объемно-модульный принцип реализации конструкции ОПЩ переходов позволяет обеспечить замену отдельных компонентов, что в свою очередь обеспечивает высокую функциональную гибкость устройства. Уменьшение габаритов ОПЩ перехода при сохранении его электрических характеристик возможно за счет хорошо известных методов, используемых в СВЧ-технике: 1) применение плат с большим значением относительной диэлектрической проницаемости; 2) за счет перехода в более высокочастотные диапазоны. Авторами данной работы рассмотрен третий метод уменьшения габаритов ОПЩ перехода за счет использования П-образного щелевого резонатора. Представлены разработка эквивалентной схемы ОПЩ перехода и расчет всех ее элементов. Проведено лабораторное исследование макета ОПЩ перехода., The application of volumetric strip-slot transition for the implementation of wireless devices with contactless frequency-selective transmission of microwave signals is relevant. This is due to the compactness of volumetric strip-slot transition achieved by the multilayer arrangement of its functional parts and of its electrical frequency-selective characteristics. At the same time the volumetric-modular design allows the replacement of its individual components which provides high functional flexibility of the device. Reducing of weight and dimensions of the volumetric strip-slot transition while maintaining its electrical characteristics is possible due to well-known methods used in microwave technology: 1) using of substrates with a high value of the relative permittivity, 2) due to the transition to higher frequency ranges. The authors of this paper present the third method for reducing of weight and dimensions of the volumetric stripslot transition by using a U-shaped slot resonator. The development of the equivalent circuit of the volumetric strip-slot transition and calculation of all its lumped elements are also presented. The values of such lumped elements as linear capacitance of the strip line, linear inductance of the strip line, characteristic impedance of the slot transmission line were determined. The value of the inductive inhomogeneity occurred when the slot resonator bends by 90 degrees was calculated and its S-parameters in the frequency range were simulated. Numerical electrodynamics simulation was performed to confirm the validity of the results of circuit simulation. Then the experiment research of the sample of the volumetric strip-slot transition with the U-shaped slot resonator was carried out. The theoretical and experimental results of the conducted researches of volumetric strip-slot transition with the U-shaped slot resonator are in good qualitative and numerical agreement with each other. The use of the U-shaped slot resonator provides

Магістерська дисертація складається з пояснювальної записки та графічної частини. Пояснювальна записка виконана на 71 сторінці формату А4, яка включає в себе 15 рисунків, 24 таблиць, 25 джерел використаної літератури. Графічна частина містить 6 аркушів технічних креслень форматом А1. В магістерський дисертації розглядається питання дослідження ризику виникнення аварійної ситуації при відмові трансформатора власних потреб теплоелектроцентралі. За вхідні данні приймаються параметри які характеризують технічний стан трансформатора. Використовуючи імовірнісно-статистичний метод за допомогою генератора випадкових чисел проведено 50 ітерацій розрахунків для розрахунку імовірності виникнення аварії. Актуальність роботи. Аналіз економічних показників сумарних збитків і доходів при виробництві електроенергії на теплоелектроцентралях показує що більшу частину збитків приносить недовідпуск енергії по причині виникнення аварій, адже в результаті такого роду аварій можуть постраждати сотні підприємств і виробник електроенергії зобов'язаний відшкодовувати недовідпущену електроенергію по відповідному тарифу. Дослідження ризику виникнення аварійної ситуації дозволяє проаналізувати можливі збитки від такого роду відключень. Таким чином у випадках коли при аналізі виявиться що ризик виникнення аварії порівняно високий то підприємство по виробництву електроенергії може прийняти рішення про проведення заходів з зменшення такого роду ризиків Метою магістерської дисертації є визначення ризику виникнення аварійної ситуації при відмові трансформатора Основним завдання після отримання різних варіантів розвитку ситуації та оцінки реального технічного стану трансформатора є визначення ризику виникнення аварійної ситуації при відмові обладнання. Об’єкт дослідження: система власних потреб теплоелектроцентралі Предмет дослідження: дослідження ризику виникнення аварійної ситуації при відмові трансформатора власних потреб теплоелектроцентралі Методи дослідження. На основі спостережень по вимірювал, The master's thesis consists of an explanatory note and a graphic part. The explanatory note is made on 86 pages of A4 format, which includes 18 figures, 24 tables, 25 sources of references. The graphic part contains 6 sheets of technical drawings in A1 format. The thesis deals with the research of emergency situation occurrence risk taking into account failure of the own needs transformer. Parameters characterizing the technical condition of the transformer are taken as input data. Using the probability-statistical method and a random number generator, 50 iterations of calculations were performed to calculate the probability of an accident. Relevance of work. Analysis of total losses economic indicators and revenues from electricity production at power plants shows that most of the losses are caused by energy shortages due to accidents, because as a result of such accidents hundreds of enterprises may suffer and the electricity producer is obliged to reimburse unauthorized electricity according to tariffs. The study of the emergency situation occurrence risks allows to analyze the possible losses from such outages. Thus, in cases where the analysis reveals that the risk of an accident is relatively high, the electricity company may decide to take measures to reduce such risks The purpose of the master's thethis is to determine the risk of an emergency situation in the event of a transformer failure The main task after receiving various options for the development of the situation and assessment of the actual technical condition of the transformer is to determine the risk of an emergency in case of equipment failure. Object of research: system of own needs of thermal power plant Subject of research: research of emergency situation occurrence risk at failure of the own needs transformer of the thermal power plant Research methods. On the basis of observations on measuring, diagnostic devices, life history, inspection of the object, the presence of signs that characte, Магистерская диссертация состоит из пояснительной записки и графической части. Пояснительная записка выполнена на 71 странице формата А4, которая включает в себя 15 рисунков, 24 таблиц, 25 источников литературы. Графическая часть содержит 6 листов технических чертежей форматом А1. В магистерский диссертации рассматривается вопрос исследования риска возникновения аварийной ситуации при отказе трансформатора собственных нужд теплоэлектроцентрали. За входящие данные принимаются параметры характеризующие техническое состояние трансформатора. Используя вероятностно-статистический метод с помощью генератора случайных чисел проведено 50 итераций расчетов для расчета вероятности возникновения аварии. Актуальность работы. Анализ экономических показателей суммарных убытков и доходов при производстве электроэнергии на теплоэлектроцентралях показывает, что большую часть убытков приносит недоотпуск энергии по причине возникновения аварий, ведь в результате такого рода аварий могут пострадать сотни предприятий и производитель электроэнергии обязан возмещать недоотпущенной электроэнергию по соответствующему тарифу. Исследования риска возникновения аварийной ситуации позволяет проанализировать возможные убытки от такого рода отключений. Таким образом в случаях, когда при анализе окажется что риск возникновения аварии сравнительно высокий то предприятие по производству электроэнергии может принять решение о проведении мероприятий по уменьшению такого рода рисков Целью магистерской диссертации является определение риска возникновения аварийной ситуации при отказе трансформатора Основной задачей после получения различных вариантов развития ситуации и оценки реального технического состояния трансформатора является определение риска возникновения аварийной ситуации при отказе оборудования. Объект исследования: система собственных нужд теплоэлектроцентрали Предмет исследования: исследование риска возникновения аварийной ситуации при отказе трансформатора собственных нужд теплоэлектроцент

The observable field is defined as the portion of the incident field that can contribute to the power received by an antenna. Recently, the observable field was estimated for a plane wave incidence. Here, the procedure is extended to a general incident field expressed as a superposition of homogeneous plane waves. The observable field concept provides a methodology to evaluate the maximum power that could be received by an ideal terminal antenna. In particular, it emerges that to maximize the received power, the pattern in transmission of the antenna should be synthesized to reproduce the angular pattern of the observable field. This is specifically relevant in cases of non-line of sight (NLOS) at high frequencies, where the power received can drop by orders of magnitude. As a case study, we consider a communication scenario which involves a base station and distributed receivers embedded in a complex scattering environment., Tera-Hertz Sensing

This letter aims at investigating the impact of the gate width on the microwave field effect transistor (FET) performance, focusing on the GaAs high-electron-mobility transistor (HEMT) technology as a case study. To accomplish this complex task, the small-signal equivalent-circuit elements together with the major RF figures of merit are thoroughly analyzed for seven HEMTs based on an interdigitated layout. The gate-width impact on the device performance is quantitatively and exhaustively estimated using a mathematical and systematical approach.

Вступ. У сучасній техніці при реєстрації сейсмічних сигналів у якості давача найбільше поширення отримали індуктивні сейсмоприймачі (геофони). При розробці апаратури прийому сейсмічних сигналів найбільшу увагу приділяють вхідним підсилювачам, до яких безпосередньо підключається геофон. Так як, в залежності від типу сейсмічного дослідження необхідно виділяти певні діапазони вхідних частот до геофонів додаються ланки фільтрації і корекції форми АЧХ та ФЧХ геофону. Тому робота геофону повинна розглядатися в комплексі з вхідними каскадами приймача сейсмічних хвиль. Основна частина. Було проаналізовано основні параметри геофонів, що наводяться у документації на виріб, виділенні основні параметри, за якими буде оцінюватися адекватність створеної моделі. Аналіз проводився на прикладі моделі GS-ONE виробництва компанії Geospace (USA). Розглянуто будовугеофона та принцип електромеханічних аналогій для створення схеми заміщення. Приведена схема заміщення з урахуванням паразитних параметрів та методика вимірювання і розрахунку елементів схеми. Розглянуто вплив шунтуючого опору, підключеного до вихідних клем геофона, на роботу геофона. Проведено розрахунок елементів схеми по наведеній методиці на прикладі геофона GS-ONE, представлено графіки АЧХ та ФЧХ, отриманні в результаті моделювання у пакеті NI Multisim. Оцінено результати моделювання за їх відповідністю до аналогічних, наведених у документації на геофон. Висновки. У даній моделі підвищена точність у порівнянні з відомими моделями[1,2] завдяки врахуванню наявності вихідної ланки геофона увигляді котушки індуктивності та її паразитних параметрів. Розроблена методика може застосовуватися для розрахунку параметрів схеми заміщення геофона та використання в пакетах моделювання електронних схем. Модель не враховує абсолютно усіх процесів, що проходять у геофоні, що призводить до відхилення в показниках амплітуди у АЧХ перетворювача до 8% а відхилення ФЧХ до 2х градусів. Проте подальше доповнення моделі ускладнить її використання

Предмет изучавања ове дисертациjе су структуре за вођење електромагнетних таласа на бази метаматериjала, коjе представљаjу водове или таласоводе периодично оптерећене подталасним резонаторима..., The topic of this thesis are guided-wave structures based on metamaterials, which represent transmission lines or waveguides periodically loaded with sub-wavelength resonators...

This article belongs to the Section Electric Vehicles., Electric vehicles (EVs) are a promising technology to reduce emissions, but its development enormously depends on the technology used in batteries. Nowadays, batteries based on lithium-ion (Li-Ion) seems to be the most suitable for traction, especially nickel-manganese-cobalt (NMC) and nickel-cobalt-aluminum (NCA). An appropriate model of these batteries is fundamental for the simulation of several processes inside an EV, such as the state of charge (SoC) estimation, capacity and power fade analysis, lifetime calculus, or for developing control and optimization strategies. There are different models in the current literature, among which the electric equivalent circuits stand out, being the most appropriate model when performing real-time simulations. However, impedance models for battery diagnosis are considered very attractive. In this context, this paper compares and contrasts the different electrical equivalent circuit models, impedance models, and runtime models for battery-based EV applications, addressing their characteristics, advantages, disadvantages, and usual applications in the field of electromobility. In this sense, this paper serves as a reference for the scientific community focused on the development of control and optimization strategies in the field of electric vehicles, since it facilitates the choice of the model that best suits the needs required.

Equivalent circuit model of a coaxial probe-fed quasi-lumped element resonator antenna is proposed. The proposed resonator is a periodic interdigital lumped element structure whose resonance does not depend on the electrical length but instead on some intrinsic circuit components, with attendant small size as a premium. The derived equivalent circuit components are extracted using the Agilent Advance Design System (ADS) software. The equivalent circuit model of the coaxial-feed probe is derived based on the simplest uniform-current model of a coaxial probe based on assumption that 1) all the higher-order evanescent have been included analytically in the parasitic circuit elements, and 2) only the propagating modes needs to be considered. The entire structure is further investigated using numerical EM solver such as finite integration technique (FIT) method in order to further compare the level of agreement. The derived equivalent circuit model has been validated by analytical formulae, numerical simulations, and measurement-based method.

This paper introduces a new method for fast computing of the iron and copper losses in electromagnetic systems. In the method, the finite element equation is reduced to the equivalent Cauer circuit via model order reduction. The nonlinear property due to core saturation is pre-computed and included in the Cauer circuit. While the copper loss is computed as the Jule loss in the circuit, the iron loss is computed in the post process by restoring the field distribution from the solution to the circuit equation with aid of the proper orthogonal decomposition.

Planar slot arrays can be fed via a main feed line with resonant centred-inclined coupling slots in its broad wall. The inclined slots couple power into radiating branches, arranged side-by-side and orthogonal to the feed waveguide. The conventional design procedure for the feed is based on the assumption that all scattering parameters of coupling junctions are either in-phase or out-of-phase at resonance. This assumption becomes invalid for small tilt angles and wide slots. The conventional design method also ignores internal higher-order mode coupling between the slots of the feed network. This paper presents an improved model that takes phase discrepancies and higher-order coupling into account. The benefits of the new model are demonstrated using a design example.

We propose a systematic approach to describe planar slot antennas, embedded in generic stratified media. An equivalent transmission line model for the slot is proposed, based on a spectral domain analysis. First, we introduce a method of moments solution to model semi-infinite slots, fed by a deltagap excitation. The solution entails only two basis functions, one located at the feed and the other at the termination. The latter basis function is chosen to properly account for the field diffractive behavior at the antenna end point. An approximate circuit model is then introduced, which describes the main mode propagating along the slot as an equivalent transmission line. Lumped impedances are extracted to accurately describe the source and the end point. This procedure can be used to derive the input impedance of planar antennas with arbitrary length in generic layered media or the interaction between multiple feeds within the same slot., Tera-Hertz Sensing

We propose a systematic approach to describe pla- nar slot antennas, embedded in generic stratified media. An equivalent transmission line model for the slot is proposed, based on a spectral domain analysis. First, we introduce a method of moments solution to model semi-infinite or finite slots, fed by a delta-gap excitation. The solution entails only two basis functions, one located at the feed and the other at the terminations. The latter basis function is chosen to properly account for the field diffractive behavior at the antenna end points. An approximate circuit model is then introduced, which describes the main mode propagating along the slot as an equivalent transmission line. Lumped impedances are extracted to accurately describe the source and the end points: the reactances account for the reactive nature of the feed and the termination, while the resistances represent the radiated space waves, emerging from both the feed and the end points. This procedure can be used to derive the input impedance of planar antennas with arbitrary length in generic layered media or the interaction between multiple feeds within the same slot., Tera-Hertz Sensing

We propose a systematic approach to describe planar slot antennas, embedded in generic stratified media. An equivalent transmission line model for the slot is proposed, based on a spectral domain analysis. First, we introduce a method of moments solution to model semi-infinite slots, fed by a deltagap excitation. The solution entails only two basis functions, one located at the feed and the other at the termination. The latter basis function is chosen to properly account for the field diffractive behavior at the antenna end point. An approximate circuit model is then introduced, which describes the main mode propagating along the slot as an equivalent transmission line. Lumped impedances are extracted to accurately describe the source and the end point. This procedure can be used to derive the input impedance of planar antennas with arbitrary length in generic layered media or the interaction between multiple feeds within the same slot., Tera-Hertz Sensing

Photoconductive antennas (PCAs) have been extensively utilized for the generation of broadband pulses over very large bandwidths. PCAs rely on a semiconductor (e.g. LT- GaAs) gap pumped by a laser and coupled to a passive structure biased at a certain voltage level. When the laser impinges on the semiconductor gap with an appropriate carrier frequency, enough energy is provided such that free electron-hole pairs are generated from the electrons that move from the valence band to the conduction band. As a result, the resistivity of the material decreases to a few ohms which in turns allows a time-varying current to flow across the gap. In recent year different hybrid equivalent circuits [1], [2], [3] have been developed in order to take into account all these complex phenomena although none of these models account for the frequency dependence of the impedance of the antenna, being formulated in the time domain. This approximation works for non-dispersive antennas such as the bow-tie, but fails in the characterization of more diverse and complex structures. The Norton equivalent circuit’s aim proposed in [4] was to fill the aforementioned gap by introducing an analytical model completely in frequency domain, although the difficulty in the characterization of the generator impedance obstructed the way for a wide acceptance in the community. In this thesis a novel approach based on a commercially available electromagnetic simulator [5] to characterise the biasing of the passive structure, the optical laser excitation and the impulse response of the photoconductor is proposed. The accuracy of the model is verified by calculating the average power radiated by a bow-tie and the results are compared to the measurements in [6]. Moreover, a revised version of the Norton equivalent circuit [4] which describes more accurately the effective generator impedance is presented. While the computer-aided model offers great introspection in the characterisation of voltages and currents, Electrical Engineering

We use simulations to optimize perovskite/silicon tandem solar cells in a novel three-terminal configuration, with one terminal at the front and two at the rear. We consider configurations in which the top cell has either the inverted or the same polarity as the bottom cell. Our goal is to minimize the optical losses, to compare the performance of both configurations and to determine the realistically achievable efficiency. Optical simulations show that if the hole-transporting material is in front of the perovskite, it gives rise to parasitic absorption losses. If it is behind the perovskite, these losses are avoided, however, at the cost of increased reflection losses. We systematically minimize these reflection losses. This increases the tandem's total implied photocurrent density from 34.4 to 41.1 mA/cm 2 . To determine the corresponding power conversion efficiency of these three-terminal tandems, electrical circuit simulations are performed based on existing 22.7% efficient perovskite and 24.9% efficient silicon cells. These simulations show that tandem efficiencies up to 32.0% can be obtained., Accepted author manuscript, Photovoltaic Materials and Devices, Electrical Sustainable Energy

We present a general analysis to describe non-periodic artificial dielectric layers (ADLs). Closed-form expressions for the equivalent layer impedance are given for generic plane-wave incidence, assuming that each individual layer can differ from the others in terms of geometrical parameters. By dropping the assumption of identical layers, the given formulas are of more general applicability for flexible designs artificial dielectric slabs that are not uniform along the stratification. The analytical expressions account for the interaction between layers due to higher-order Floquet modes, thus remain valid for arbitrarily small electrical distance between layers., Tera-Hertz Sensing

This research study reports the assessment of complementary split ring resonators based on Gielis transformation as basic elements for the design of high-performance microwave components in printed technology. From the electromagnetic simulation of said structures, suitable equivalent circuit models are extracted and analyzed. Physical prototypes are fabricated and tested for design validation. The obtained results confirm that the adoption of supershaped geometries enables the synthesis of very compact scalable microwave filters.

A new approach based on the incorporation of Z-shaped defected ground structure (DGS) in microstrip antenna (MSA) for improving impedance matching and cross polarization (XP) performances is proposed in this paper. Through detail analysis of the surface current densities, and input impedance, the proposed DGS is integrated into a rectangular MSA (RMSA) to realize flat relative XP reduction of 22 dB in the H-plane around broadside angular range of ±60 degrees. Further, an equivalent circuit model (ECM) for the proposed antenna is introduced by considering the mutual coupling in between the DGS and patch and the model is verified using circuit-system-EM co-simulation software, Advanced Design System (ADS). A prototype has been fabricated and tested for the validation of simulated results and it shows good agreement with each other. The antenna operates over 2.32-2.58 GHz with good far-field radiation characteristics and a peak gain of 2.8 dBi at the resonating frequency 2.4 GHz. Hence, the proposed design can be useful for the IEEE 802.11b applications.

A new approach based on the incorporation of Z-shaped defected ground structure (DGS) in microstrip antenna (MSA) for improving impedance matching and cross polarization (XP) performances is proposed in this paper. Through detail analysis of the surface current densities, and input impedance, the proposed DGS is integrated into a rectangular MSA (RMSA) to realize flat relative XP reduction of 22 dB in the H-plane around broadside angular range of ±60 degrees. Further, an equivalent circuit model (ECM) for the proposed antenna is introduced by considering the mutual coupling in between the DGS and patch and the model is verified using circuit-system-EM co-simulation software, Advanced Design System (ADS). A prototype has been fabricated and tested for the validation of simulated results and it shows good agreement with each other. The antenna operates over 2.32-2.58 GHz with good far-field radiation characteristics and a peak gain of 2.8 dBi at the resonating frequency 2.4 GHz. Hence, the proposed design can be useful for the IEEE 802.11b applications.

The laser-induced current carrier generation and transport under large biasing voltages in photoconductive materials located in electrode gap region of photoconductive antennas is a complex process involving many different phenomena that interact with each other in intricate ways. Given the large biasing voltages employed, a simple model that assumes that the carriers travel along the biasing field lines allows to retain the basic features of the photocarrier generation process. The model is presented in detail and results for a typical interdigitated electrode are shown to well agree with measures found in the literature., This work was supported in part by the Spanish Inter-Ministerial Commission on Science and Technology (CICYT) under projects TEC201678028-C3-1 and, by FEDER and the Unidad de Excelencia Maria de Maeztu MDM-2016-0600, which is financed by the Agencia Estatal de Investigacion, Spain, and by Catalan Research Group 2017 SGR219., Peer Reviewed, Postprint (published version)

This paper demonstrates an equivalent circuit model for large scale WPT system with multiple receivers. Manyarticles have shown the method for determining optimum load impedance at receiver and power distribution in multiplereceiverenvironment. These analysis indicate requirement of an equivalent circuit when a transmitter side and receiver sidesare coupled. This paper newly assumes that transmitter side is large scale so that equivalent circuit have to be combinationof concentrated/distributed constant. Proposed model is experimentally investigated under the assumption that single parallelline feeder coupled with multiple receiver with different location.

A new approach based on the incorporation of Z-shaped defected ground structure (DGS) in microstrip antenna (MSA) for improving impedance matching and cross polarization (XP) performances is proposed in this paper. Through detail analysis of the surface current densities, and input impedance, the proposed DGS is integrated into a rectangular MSA (RMSA) to realize flat relative XP reduction of 22 dB in the H-plane around broadside angular range of ±60 degrees. Further, an equivalent circuit model (ECM) for the proposed antenna is introduced by considering the mutual coupling in between the DGS and patch and the model is verified using circuit-system-EM co-simulation software, Advanced Design System (ADS). A prototype has been fabricated and tested for the validation of simulated results and it shows good agreement with each other. The antenna operates over 2.32-2.58 GHz with good far-field radiation characteristics and a peak gain of 2.8 dBi at the resonating frequency 2.4 GHz. Hence, the proposed design can be useful for the IEEE 802.11b applications.