Capacitive Reactance Research Articles

Inhibition Performance of Cetyltrimethylammonium Bromide Against Reinforcing Steel Corrosion in Simulated Concrete Pore Solutions

Reinforcing steel corrosion in concrete is a main reason for the deterioration of durability of reinforced concrete structures. The widespread corrosion of reinforcing steel caused by chloride ions is a common and serious problem all over the world. Obviously, corrosion protection of reinforcing steel in concrete has become an urgent and important task. The use of corrosion inhibitors is one of the promising protection methods for controlling steel corrosion in concrete because of their low cost and easy application. The development and application of surfactant corrosion inhibitors have drawn special attention. Many surfactants have inviting application prospects for the corrosion protection of metals. Cetyltrimethylammonium bromide (CTMAB), a cationic surface active agent, has been studied for metal corrosion protection due to its main advantages of non-toxicity and a popular price. Nevertheless, there is little information on CTMAB as a corrosion inhibitor for steel in concrete. In this work, the surfactant CTMAB was employed as a corrosion inhibitor and its inhibition performance against reinforcing steel corrosion in the simulated concrete pore solutions was studied by electrochemical measurements and surface analyses. The cylindrical specimens with Ø11.2 mm × 4 mm were cut from a Q235 reinforcing steel bar. The specimen mounted in epoxy resin was used as the working electrode with an exposed area of 1.00 cm2during electrochemical measurements, and a platinum sheet and a saturated calomel electrode (SEC) served as the auxiliary electrode and the reference electrode, respectively. The compositions of the specimens were analyzed by X-ray energy dispersive spectroscopy (EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), and their morphologies were observed by scanning electron microscopy (SEM). A saturated Ca(OH)2 solution with pH about 12.50 was selected as a simulated concrete pore solution. After the solution was adjusted to pH 11.00 with a 0.8 mol/L NaHCO3solution and 0.5 M NaCl was added, it served as a simulated polluted concrete pore (SPCP) solution, namely a test solution. Then different concentrations of CTMAB were added to the SPCP solution to investigate the corrosion inhibition effect of CTMAB on the reinforcing steel. The EIS analysis of the steel in the SPCP solution showed the capacitive reactance arc size increased gradually while the CTMAB concentration was increased from 0 to 0.005 M, then decreased with the increasing of the CTMAB concentration from 0.005 to 0.1 M. When the CTMAB concentration was 0.005 M, the interfacial charge transfer resistance (R ct) of the steel reached a maximum of 41.17 kΩ cm2, and the inhibition efficiency of CTMAB was 79.9%. The inhibition efficiency of CTMAB determined from the polarization curve of the steel in the SPCP solution with 0.005 M CTMAB reached 87.6%, indicating that the CTMAB could inhibit corrosion of reinforcing steel effectively. For the SPCP solution without CTMAB there was not a passive region on the potentiodynamic anodic polarization curve of the steel, indicating that the steel corrosion took place. However, the steel was in a passive state for the solution with 0.005 M CTMAB. The SEM results also indicated that CTMAB could protect the steel from corrosion. XPS and Raman results proved that CTMAB was an adsorption type corrosion inhibitor. The adsorbed CTMAB resulted in the formation of a protective film on the steel surface to protect the steel from corrosion.

Minimizing harmonic distortion in power system with optimal design of hybrid active power filter using differential evolution

Hybrid active power filter (HAPF) is an advanced form of harmonic filter combining advantages of both active and passive filters. In HAPF, selection of active filter gain, passive inductive and capacitive reactances, while satisfying system constraints on individual and overall voltage and current harmonic distortion levels, is the main challenge. To optimize HAPF parameters, this paper proposes an approach based on differential evolution (DE) algorithm called L-SHADE. SHADE is the success history based parameter adaptation technique of DE optimization process for a constrained, multimodal non-linear objective function. L-SHADE improves the performance of SHADE with linearly reducing the population size in successive generations. The study herein considers two frequently used topologies of HAPF for parameter estimation. A single objective function consisting of both total voltage harmonic distortion (VTHD) and total current harmonic distortion (ITHD) is formulated and finally harmonic pollution (HP) is minimized in a system comprising of both non-linear source and non-linear loads. Several case studies of a selected industrial plant are performed. The output results of L-SHADE algorithm are compared with a similar past study and also with other well-known evolutionary algorithms.

Development of a dimensionless parameter for characterization of dielectric barrier discharge devices with respect to geometrical features

Non-thermal plasma (NTP) devices produce excited and radical species that have higher energy levels than their ground state and are utilized for various applications. There are various types of NTP devices, with dielectric barrier discharge (DBD) reactors being widely used. These DBD devices vary in geometrical configuration and operating parameters, making a comparison of their performance in terms of discharge power characteristics difficult. Therefore, this study proposes a dimensionless parameter that is related to the geometrical features, and is a function of the discharge power with respect to the frequency, voltage, and capacitance of a DBD. The dimensionless parameter, in the form of a ratio of the discharge energy per cycle to the gap capacitive energy, will be useful for engineers and designers to compare the energy characteristics of devices systematically, and could also be used for scaling up DBD devices. From the results in this experiment and from the literature, different DBD devices are categorized into three separate groups according to different levels of the energy ratio. The larger DBD devices have lower energy ratios due to their lower estimated surface discharge areas and capacitive reactance. Therefore, the devices can be categorized according to the energy ratio due to the effects of the geometrical features of the DBD devices, since it affects the surface discharge area and capacitance of the DBD. The DBD devices are also categorized into three separate groups using the Kriegseis factor, but the categorization is different from that of the energy ratio.

Multifrequency time difference EIT imaging of cardiac activities

Abstract It has been proven that EIT can distinguish respiration and cardiac activities. However, the quality of EIT images of cardiac activities is poor because the induced/sensed impedance signal from the heart is much weaker than the ventilation signal. For EIT imaging of cardiac activities, induced voltages should differ at different excitation frequencies, owing to the cardiac capacitive reactance. At the same time, there are only few existing EIT systems designed for cardiac imaging. Based on these reasons, we present herein a preliminary study on the frequency response of cardiac activities. Three aspects have been improved in the designed system: i) The designed dual-band belt is shown to maintain good body contact for more than four hours of testing, ii) the recovery time of channel switching was quantified, and the signal recovery time is estimated to be approximately 23 us in the final system, and iii) the electrode belt and the load value were taken into consideration for system correction. The corrected system has an SNR greater than 80 dB for excitation frequencies up to 1 MHz. Five healthy male volunteers were tested in the siting position, and the results showed that the frequency response amplitudes reach maximum values when the excitation frequency is 50 kHz. Therefore, it is possible to conduct a preliminary qualitative analysis of cardiac function using impedance spectroscopy. At the same time, additional details on the impedance of cardiac activities can be obtained using a lower excitation frequency.

Electrical Dielectric Authorship of Polyvinyl-Acetate and Toluene Diisocyanate (PVA-TDI) with Manufactured Sulfonated Phenol-formaldehyde (SPF) Viscous Mass Material Composite

The electrical insulation of the manufacture sulfonated phenol-formaldehyde viscous material (product) has been studied with Polyvinyl-acetate (PVA) and toluene diisocyanate (TDI) blend has been prepared by fixing percentage by weight 3:1 and mixed with different percentages by weight of the product sulfonated phenol formaldehyde viscous mass (SPF). The Fourier transform infrared (FTIR) spectroscopy is done on (SPF) resin powder and prepared film of PVA-TDI-SPF viscous mass. The quality factor (Q), dissipation factor (D), parallel resistance (Rp), series resistance (Rs), parallel capacitance (Cp), series capacitance (Cs) and phase shift (?) are measured. The calculated maximum dielectric constant (??) is 3.49x107 at sample (1) wt.1% SPF viscous mass to the weight of (PVA-TDI), the minimum dielectric constant is 1.12x106 at sample (3) wt.3% of SPF viscous mass to PVA-TDI weight. The maximum dielectric loss factor (??) is 3.68x107 at sample (1) and the minimum dielectric loss is 2.04x106 for sample (3). The maximum conductance is 1.06x10-4 S at sample (1) and minimum conductance is 6.64x10-6 at sample (3). The maximum frequency dependent ac. conductivity (?ac) is 2.048 S m-1 for sample (1) and the minimum is 0.113 S m-1 at sample (3). The maximum total conductivity (?t) is 126.2 S m-1 for sample (1) and minimum (?t) is 1.129 S m-1 for sample (3). The maximum independent conductivity (?dc) is 124 S m-1 for sample (1) and minimum value is 1.015 S m-1 for sample (3). The maximum capacitive reactance (Xs) is 0.83 M? at sample (5) wt.5% SPF viscous mass to PVA-TDI weight and the minimum is 0.14 M? for sample (3).

A Miniaturized CPW-Fed Spiral Ring Resonator Loaded Slot Antenna for Wireless Application

A simple and novel approach of size reduction of a slot antenna loaded with spiral ring resonator (SRR) on the patch surface is highlighted. The antenna resonates at 4.5 GHz when a half wavelength slot section is fed by the coplanar waveguide line. The fundamental resonant frequency is lowered by 2.05 GHz when the slot antenna is loaded with a pair of SRR at the end of the half wavelength slot section. The additional inductive and capacitive reactance of the resonator enables the patch to resonate at lower frequency (2.45 GHz). The proposed antenna structure reduces the resonant frequency with respect to the reference antenna (slot antenna without SRR) by 45.5%, causing the patch to almost reach an electrically small size. Finally, asymmetrical slot has been used and a wide band antenna of band width 900 MHz has been achieved. Despite the loaded patch touching the electrically small limit, the antenna needs no matching networks, offers high efficiency and exhibits a bandwidth better than the unperturbed patch. The radiation pattern is also seen to be unaffected by the presence of the SRR.

Influence of capacitive no-load current component in large power transformers

No load current of large power transformers consists of active and reactive component. Active component covers hysteresis and eddy current losses in the core. Reactive component (usually called magnetizing current) creates magnetic field / magnetic flux and lags the voltage by 90°. In most models these two components are enough to describe no-load current in large power transformer at power grid frequency (50 or 60 Hz). Due to the low frequency modeling the winding capacitance are usually neglected. For higher frequencies and/or transients, ground capacitive reactances and capacitive reactances between winding turns and windings are significant and they need to be modeled and, therefore, capacitive current component occurs [1]. If capacitances can be neglected, reactive component of no load current consists only of magnetizing part and depends only on magnetic steel properties, following its B-H curve.In this paper the presence of capacitive component of large power transformer no-load current is presented when powered by 50 Hz sinusoidal voltage. Capacitive component exist mainly as sum of the capacitive component of supplied windings and transferred currents from other windings [2], [3] Its influence on the no-load characteristic and an approach for determination of the inductive component in the no-load current based on the no-load current measurement is explained. Equivalent capacitance is compared with capacitance measurements in test field.

Electrical Dielectric Authorship of Polyvinyl-Acetate and Toluene Diisocyanate (PVA-TDI) with Manufactured Sulfonated Phenol-formaldehyde (SPF) Viscous Mass Material Composite

The electrical insulation of the manufacture sulfonated phenol-formaldehyde viscous material (product) has been studied with Polyvinyl-acetate (PVA) and toluene diisocyanate (TDI) blend has been prepared by fixing percentage by weight 3:1 and mixed with different percentages by weight of the product sulfonated phenol formaldehyde viscous mass (SPF). The Fourier transform infrared (FTIR) spectroscopy is done on (SPF) resin powder and prepared film of PVA-TDI-SPF viscous mass. The quality factor (Q), dissipation factor (D), parallel resistance (Rp), series resistance (Rs), parallel capacitance (Cp), series capacitance (Cs) and phase shift (?) are measured. The calculated maximum dielectric constant (??) is 3.49x107 at sample (1) wt.1% SPF viscous mass to the weight of (PVA-TDI), the minimum dielectric constant is 1.12x106 at sample (3) wt.3% of SPF viscous mass to PVA-TDI weight. The maximum dielectric loss factor (??) is 3.68x107 at sample (1) and the minimum dielectric loss is 2.04x106 for sample (3). The maximum conductance is 1.06x10-4 S at sample (1) and minimum conductance is 6.64x10-6 at sample (3). The maximum frequency dependent ac. conductivity (?ac) is 2.048 S m-1 for sample (1) and the minimum is 0.113 S m-1 at sample (3). The maximum total conductivity (?t) is 126.2 S m-1 for sample (1) and minimum (?t) is 1.129 S m-1 for sample (3). The maximum independent conductivity (?dc) is 124 S m-1 for sample (1) and minimum value is 1.015 S m-1 for sample (3). The maximum capacitive reactance (Xs) is 0.83 M? at sample (5) wt.5% SPF viscous mass to PVA-TDI weight and the minimum is 0.14 M? for sample (3).

넓은 범위의 선형 출력 제어를 위한 5kW 플라즈마 전원장치 설계 및 반응기 커패시턴스 추정 알고리즘의 관한 연구

넓은 범위의 선형 출력 제어를 위한 5kW 플라즈마 전원장치 설계 및 반응기 커패시턴스 추정 알고리즘의 관한 연구

Improving the pollutant removal efficiency of packed-bed plasma reactors incorporating ferroelectric components

In this work we have studied the plasma removal of air contaminants such as methane, chloroform, toluene and acetone in two parallel plate packed-bed dielectric barrier discharge (DBD) reactors of different sizes. Removal and energy efficiencies have been determined as a function of the residence time of the contaminated air within the reactor, the kind of packed-bed material (ferroelectrics or classical dielectric materials), the frequency and the incorporation of a ferroelectric plate onto the active electrode together with the inter-electrode ferroelectric pellets filling the gap. Results at low frequency with the small reactor and the ferroelectric plate showed an enhancement in energy efficiency (e.g., it was multiplied by a factor of six and three for toluene and chloroform, respectively) and in removal yield (e.g., it increased from 22% to 52% for chloroform and from 15% to 21% for methane). Such enhancements have been attributed to the higher energy of plasma electrons and a lower reactor capacitance found for this plate-modified configuration. A careful analysis of reaction efficiencies and electron energy distributions for the different investigated conditions and the simulation of the electric field at the necks between ferroelectric/dielectric pellets complete the present study. Overall, the obtained results prove the critical role of the barrier architecture and operating conditions for an enhanced performance of pollution removal processes using DBD systems.

A new contactless impedance sensor for void fraction measurement of gas–liquid two-phase flow

With impedance elimination principle and phase sensitive demodulation (PSD) technique, this work aims to develop a new contactless impedance sensor, which is suitable for the void fraction measurement of gas–liquid two-phase flow. The impedance elimination principle is used to overcome the unfavorable influences of the coupling capacitances, i.e. the capacitive reactances of the coupling capacitances are eliminated by the inductive reactance of an introduced inductor. PSD technique is used to implement the impedance measurement. Unlike the conventional conductance/impedance sensors which use the equivalent conductance (the real part of the impedance) or the amplitude of the impedance of gas–liquid two-phase flow, the new contactless impedance sensor makes full use of the total impedance information of gas–liquid two-phase flow (including the amplitude, the real part and the imaginary part of the impedance, especially the imaginary part) to implement the void fraction measurement. As a preliminary study, to verify the effectiveness of the new contactless impedance sensor, two prototypes (with different inner diameters of 17.0 mm and 22.0 mm) are developed and experiments are carried out. Two typical flow patterns (bubble flow and stratified flow) of gas–liquid two-phase flow are investigated. The experimental results show that the new contactless impedance sensor is successful and effective. Compared with the conventional conductance/impedance sensors, the new contactless impedance sensor can avoid polarization effect and electrochemical erosion effect. The total impedance information is used and the void fraction measurement performance of the new sensor is satisfactory. The experimental results also indicate that the imaginary part of the impedance of gas–liquid two-phase flow is very useful for the void fraction measurement. Making full use of the total impedance information of gas–liquid two-phase flow can effectively improve the void fraction measurement accuracy.

Instrumentación de un impulsor para lámpara de LED

This article describes the implementation of an LED lamp driver. It seeks to control the brightness of the LED lamp through PWM technique, RC and MOSFET circuits. An electrical instrumentation proposal is made by using the concept of capacitive reactance to limit the input current mains AC.

Design of low‐profile broadband capacitive circuit absorber

A low-profile broadband capacitive circuit absorber has been demonstrated both numerically and experimentally. The design consists of square loop resonators and lumped resistors periodically arranged on the top of grounded dielectric substrate. The novelty of the design lies in its capacitive reactance due to square loop geometry, which reduces the electrical thickness of the structure compared with the earlier broadband absorbers. The simulated results show that the structure exhibits reflectance below −10 dB from 1.91 to 5.75 GHz with the thickness of only 0.07λl at the lowest operating frequency. Furthermore, the proposed structure is polarisation insensitive as well as angularly stable. The structure has also been fabricated, whose measured result is in good agreement with the simulated response.

Integrated Inverse Class-F Silicon Power Amplifiers for High Power Efficiency at Microwave and mm-Wave

This paper presents two 2-stage inverse class-F power amplifiers (PAs) at 24 GHz and 38 GHz, integrated in $0.13~\mu \text {m}$ SiGe BiCMOS technology. The PAs are composed of an inverse class-F output stage proceeded by a class-AB driving amplifier. An inter-stage matching network between the driver and output stage delivers an optimal inter-stage power to the output stage with a maximum PAE in the driver amplifier. The output stage’s load network based on multi-resonance LC resonators terminates harmonic impedance explicitly up to the third of the fundamental signal. By leveraging a native low capacitive reactance, the class- $\text {F}^{\mathrm {-1}}$ load network shapes a quasi-rectangular current waveform that effectively contains up to the fifth harmonic spectral component. A high impedance control is limited up to the second harmonic, shaping a half-sinusoid voltage peaking induced by DC, fundamental, and the second harmonic voltage spectra. The 24 GHz PA achieves 50% peak PAE, 16 dBm $\text {OP}_{\mathrm {-1dB}}$ , 18 dBm $\text {P}_{\mathrm {sat}}$ , and 19 dB saturated power gain with 2.3 V supply voltage at 24 GHz. The 24 GHz PA can maintain >45% PAE over 23.5–25.5 GHz and 1.5–2.4 V supply voltage range, manifesting a PAE robustness to the frequency and supply variations. For 38 GHz PA, measurements show 38.5% peak PAE, 15 dBm $\text {OP}_{\mathrm {-1dB}}$ , 17 dBm $\text {P}_{\mathrm {sat}}$ with 15 dB of saturated power gain at the $\text {OP}_{\mathrm {-1dB}}$ point when 2.4 V supply voltage is applied. The 38 GHz PA can sustain >35% PAE over 36–39 GHz and 1.5–2.5 V supply variation. The PAs also are tested under the input of band-limited signals modulated by various modulation schemes including 8-PSK, QAM, 16-QAM, 64-QAM, and 128-QAM, and test results are presented in this paper. The chip size is $0.95\times 0.6$ mm2 for 24 GHz PA and $0.93\times 0.55$ mm2 for 38 GHz PA, including all pads.

Three-Phase Self-Excited Induction Generator for Wind Energy Analytical Techniques and Experimental Results

This paper considers the use of induction motor as an induction generator when the wind energy is considered as input mechanical power. Moreover, it describes the behavior of the terminal voltage and frequency under variable load conditions. To determine the critical capacitance value for self-excitation a set of curves was plotted. This paper proposes a new method based on the calculation of magnetizing reactance and capacitance reactance. Experimental results show the dependence of voltage level, power output, frequency, and load current on the right selected capacitance.

Capacitive/inductive compensation factor in coupled lines wilkinson power divider design

ABSTRACTIn this article, two coupled line sections are taken place transmission lines for miniaturization in Wilkinson power divider. A general compensation factor is shunted in the middle of two coupled line sections to compensate the different input impedances between even‐ and odd‐mode, where, the factor could be capacitive or inductive reactance, and its value is determined by effective dielectric constants of substrate, coupling strength and its physical lengths of two coupled line sections. Compared with the function of compensated capacitor, the similar results are newly summarized in this article: compensated inductor could also be used to compensate different characteristic impedances in stripline structure (homogeneous medium), and compensate the difference of phase velocities microstrip line structure (inhomogeneous medium). Design charts and calculated bandwidths are discussed for both different structures. One experimental circuit was fabricated in microstrip line structure, and the measurement results showed good agreement with theoretical results © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2940–2944, 2016

Wide‐band frequency agile MIMO antenna system with wide tunability range

ABSTRACTIn this work, a 4‐element wide band frequency agile multiple‐input‐multiple‐output (MIMO) antenna system is presented. Frequency agility is achieved by loading the antenna elements with capacitive reactance using varactor diodes. The proposed MIMO antenna is a wide band antenna with very wide tunability range between 1610 and 2710 MHz, thus covering several well‐known wireless standards. Each tuned band has at least 470 MHz bandwidth. The proposed design is simple in structure with low profile antenna elements. The design is fabricated on an FR4 substrate with single element dimensions of 7.9 × 26.9 mm2 on a single board of dimensions 60 × 100 × 0.8 mm3. The proposed MIMO antenna system is highly suitable to be used in wireless handheld devices and mobile terminals within a cognitive radio platform. The antenna system is also characterized for MIMO performance metrics. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2276–2280, 2016

OPTIMIZATION OFSPIRAL INDUCTOR WITH DIFFERENT INNER DIAMETERS

A scalable and highly accurate RF/Microwave symmetricalinductor has been designed using microstrip line. The 18 circular and 18 square structures are optimized with 600MHz operating frequency. The characteristic interest on high frequency operating circuits is inductance value and quality factor of the spiral inductor. The value of the spiral inductor is depends on conductor width (W) space between the conductor (S), turns (n) outer diameter and inner diameter of the spiral inductor. In this design change the distribution of an inner diameter from 5mil to 10milfor 3 to 5 turns of spiral inductors. The optimization of inner diameter distribution is done by keeping space (1mil)between the conductor and width (2mil) of the conductor as constant. The changing inner diameter will effect to change in magnitude of the inductance and quality factor due passive capacitive and inductive reactance effect. These spiral inductors are designed using aluminum (Al) substrate material with 15mil height from the ground plane. The cupper material is used as a conductor of thickness 0.302mm. The aim of this paper is to compare the electromagnetic simulated results with simple equations of modified wheeler (MW), current sheet Approximation (CSA) and monomial equation (ME). The passive component effect the spiral inductor is examines the variation of inductance and quality factor. The observed electromagnetic field simulated results gives better agreement with standard simple mentioned equations with 600MHz operating frequency. The validation of spiral inductor is done with different inner diameter (5mil to 10mil) and number of turns (3turns to 5 turns) of the spiral inductor.

OHM'S LAW IS THE GENERAL LAW OF EXACT SCIENCES

Ponte Academic JournalJul 2016, Volume 72, Issue 7 OHM'S LAW IS THE GENERAL LAW OF EXACT SCIENCESAuthor(s): Alexander Alexandrovich AntonovJ. Ponte - Jul 2016 - Volume 72 - Issue 7 doi: 10.21506/j.ponte.2016.7.9 Abstract:It is shown that Ohm�s law in the interpretation of Steinmetz and special theory of relativity are antagonists in solving the problem of physical reality of concrete imaginary numbers, since Ohm's law has solved this problem successfully, whereas special theory of relativity has postulated impossibility of its solving. Therefore, being influenced by the special theory of relativity the problem has not been solved in the theory of electrical circuits, and the question of physical reality of imaginary reactance of capacitors and inductors has been left open. The paper proves physical reality of imaginary numbers. Physical reality of capacitive and inductive reactances is proved, including by Ohm's law. And thereby it proves the fallacy of the current version of the special theory of relativity. The paper presents the adjusted version of the special theory of relativity, which enables to develop a hypothesis of the hidden Multiverse. Parallel universes of such a Multiverse are mutually invisible in relation to each other, as they are in different dimensions. The hypothesis is confirmed by the data obtained by WMAP and Planck spacecrafts. It also explains the astrophysical phenomenon of dark matter and dark energy, which, in turn, is an experimental confirmation of existence of the hidden Multiverse. Download full text:Check if you have access through your login credentials or your institution Username Password

Análise do caminho de retorno de uma corrente elétrica em um plano terra

Considerando uma abordagem estática, a corrente elétrica em um material condutor flui pelo caminho que apresenta a menor resistência. Já na abordagem dinâmica (corrente alternada), este caminho é definido pela menor impedância, que depende não somente da resistência, mas das reatâncias indutiva e capacitiva. Dessa forma, a variação da frequência dessa corrente pode alterar o caminho que ela percorre em um plano condutor, uma vez que as reatâncias serão importantes no caminho de menor impedância. Esse efeito é bem conhecido e muito utilizado para a construção de filtros e osciladores. Neste trabalho este efeito será analisado através de simulações eletromagnéticas e também experimentalmente, com o auxílio de um modelo didático de fácil construção.