Marlio Bonfim
Universidade Federal do Paraná, Engenharia Eletrica, Faculty Member
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signals buried in noise as well as real and imaginary parts of a complex quantity. They are based on the technique of synchronous detection, where... more
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signals buried in noise as well as real and imaginary parts of a complex quantity. They are based on the technique of synchronous detection, where the signal of interest is modulated into a desired frequency, sent to the medium or device to be analyzed, and captured by a detector. The detector scheme relies on the concept of phase-sensitive detection, generally resulting in two components: in-phase and quadrature. This article shows a very simple and low computational-cost way to implement a dual-phase LIA, using readily available microcontrollers, running a simple and fast algorithm. Three examples of signal detection are presented (sound wave signal, impedance meter, and weak signal recovery) to point out the flexibility and capabilities of the proposed methodology.
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High performance permanent magnets are key components in the development of more efficient electrical motors for electric and hybrid cars as well as gearless wind turbines.
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Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signals buried in noise as well as real and imaginary parts of a complex quantity. They are based on the technique of synchronous detection, where... more
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signals buried in noise as well as real and imaginary parts of a complex quantity. They are based on the technique of synchronous detection, where the signal of interest is modulated into a desired frequency, sent to the medium or device to be analyzed, and captured by a detector. The detector scheme relies on the concept of phase-sensitive detection, generally resulting in two components: in-phase and quadrature. This article shows a very simple and low computational-cost way to implement a dual-phase LIA, using readily available microcontrollers, running a simple and fast algorithm. Three examples of signal detection are presented (sound wave signal, impedance meter, and weak signal recovery) to point out the flexibility and capabilities of the proposed methodology.
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Spiking neural networks (SNNs) first came to the attention of scientists due to the search for a structure capable of emulating more closely the behavior of the human brain. The biological nervous system has some characteristics that... more
Spiking neural networks (SNNs) first came to the attention of scientists due to the search for a structure capable of emulating more closely the behavior of the human brain. The biological nervous system has some characteristics that allow it to process a large amount of data very quickly. It is also a fault-tolerant system, with a high level of parallelism. Low power consumption is another feature of the human brain that is desirable for electronic circuits. In this context, several models of artificial spiking neurons were developed, aiming to construct networks able to combine the best characteristics of the human brain. Most of these models, however, lack validation in larger networks. This paper proposes the implementation of an SNN based on a nanoelectronic spiking neuron model developed in previous works. To validate the behavior of an isolated neuron in a network, logic gates (NOT, OR, AND, and XOR) are used as a benchmark. The goal of this paper is to present a feasibility study on the possibility of implementing such nanoelectronic spiking neuron networks based on this spiking neuron model. Nanoelectronics represents an appealing implementation due to the gains regarding occupied area and power consumption, which are inherent characteristics of this technology. The neuron model was modified for simulation at room temperature. An information code based on the amplitude of the pulses presented at the output of the neuron was developed. During deployment of this approach, some limitations regarding the neuron model were detected; some possible solutions are proposed as future work.
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This paper presents a new approach to the classical design and implementation of a Lock-In Amplifier (LIA) applied to impedance measurement of interdigital capacitive sensors in order to evaluate water polution. It is based on a... more
This paper presents a new approach to the classical design and implementation of a Lock-In Amplifier (LIA) applied to impedance measurement of interdigital capacitive sensors in order to evaluate water polution. It is based on a general-purpose microcontroller and an active band-pass filter. The design uses a wave generator (AD9833) as source for the reference signal and an Analog to Digital Converter (ADC) from the microcontroller to sample the device under test (DUT) signal. In the particular context of this study, the sensor responses are evaluated by conductance, impedance and capacitance measurements on water-chlorine and water-salt solutions.
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Research Interests: Physics, Materials Science, X ray absorption spectroscopy, Synchrotron Radiation, Magnetic field, and 11 moreMagnetization Reversal, Thin Film, Physical sciences, Magnetic Properties, Time Resolved, CHEMICAL SCIENCES, Magnetization dynamics, Magnetization, Magnetic Circular Dichroism, x-ray magnetic circular dichroism (XMCD), and Springer Ebooks
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Soil nailing system is widely used along highways in Brazil. Non-destructive techniques have been used to estimate the length of installed soil nails. Sonic Echo and Impulse Response techniques evaluate the bar length using sonic wave... more
Soil nailing system is widely used along highways in Brazil. Non-destructive techniques have been used to estimate the length of installed soil nails. Sonic Echo and Impulse Response techniques evaluate the bar length using sonic wave propagation. The methods are similar and consists in generate an impact with a hammer. Results may be affected by this non-standard procedure. This paper aims to propose an automated sound wave generation in order to carried out tests quickly, with reproducibility and without operator dependence. An electromagnetic launching system was developed, which uses a projectile in place of the hammer, and the electromagnetic force instead of human force. The sound data was received by a microphone and sent to the computer by a microcontroller, making the system compact and portable. Projectile output speed optimization and impact reproducibility were analyzed. Nails length were obtained by both time and frequency domain data analysis. Results showed high reproducibility under the same initial condition. Propagation velocity presented a relative error less than 1% for steel bar with length of 1 m.
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High magnetic fields are required for the study of hard magnetic materials and, in many cases, the reversal of these fields is essential. This paper describes a portable pulse generator capable of producing bipolar magnetic fields up to... more
High magnetic fields are required for the study of hard magnetic materials and, in many cases, the reversal of these fields is essential. This paper describes a portable pulse generator capable of producing bipolar magnetic fields up to 20 T into a copper coil. The peak current around 7 kA is achieved by discharging two capacitor banks through a combination of thyristors and fast diodes. Each pulse polarity has a semisinusoidal shape with 18 μs base width. Pulse triggering is computer controlled and magnetic measurements are done by an induction coil or Kerr effect acquired by a sampling oscilloscope. The whole apparatus weighs less than 2 kg. Hysteresis loops of NdFeB magnets were done to demonstrate the viability of the system.
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In this article we present three techniques developed by our group for probing magnetization dynamics in the nanosecond time scale. All these techniques are based on the magneto-optical interaction of materials with polarized light.... more
In this article we present three techniques developed by our group for probing magnetization dynamics in the nanosecond time scale. All these techniques are based on the magneto-optical interaction of materials with polarized light. Magnetic excitation is provided by microcoils able to generate field pulses of some teslas within a few nanoseconds. Standard Kerr/Faraday dynamic measurements and imaging can be performed as well as time-resolved x-ray magnetic circular dichroism where chemical selectivity can be achieved.
Research Interests: Engineering, Physics, Applied Physics, Ultrafast Optics, Optical Spectroscopy, and 14 moreMagnetic field, Mathematical Sciences, Magnetization Reversal, Physical sciences, Time Resolved, Magnetization dynamics, Magnetization, Magnetic Circular Dichroism, X ray Absorption, x-ray magnetic circular dichroism (XMCD), Polarized Light Microscopy, Faraday Effect, Faraday Cage, and Excitation
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It is shown in this work that a synchronous measurement setup is able to conveniently and accurately retrieve ferromagnetic resonance's (FMR) main physical properties from a permalloy sample. The apparatus used comprises a vector... more
It is shown in this work that a synchronous measurement setup is able to conveniently and accurately retrieve ferromagnetic resonance's (FMR) main physical properties from a permalloy sample. The apparatus used comprises a vector network analyzer (VNA), coupled with external DC coils, driven by a controllable power supply. A permalloy thin film sample was subjected to a microwave signal through a grounded coplanar waveguide. A square wave signal generated by an Arduino microcontroller drives the coils to a triangular, 65.4 ms period magnetic field. This field’s half-cycle is synchronized to match a zero-span sampling time at the VNA. The system has the advantage of fast results, as the typical FMR lorentzian curve is completed in a few seconds and shown immediately on the VNA’s scattering parameter S21 trace graph. The system showed an improved signal-to-noise ratio of 51.7 at 10 GHz over 24.3 for the 100 nm thick permalloy- sample used in this work. A magnetic field resonance p...
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We have studied the effect of He+ irradiation on the dynamics of chiral domain walls in Pt/Co/AlOx trilayers in the creep regime. Irradiation leads to a strong decrease in the depinning field and a non-monotonous change of the effective... more
We have studied the effect of He+ irradiation on the dynamics of chiral domain walls in Pt/Co/AlOx trilayers in the creep regime. Irradiation leads to a strong decrease in the depinning field and a non-monotonous change of the effective pinning barriers. The variations of domain wall dynamics result essentially from the strong decrease in the effective anisotropy constant, which increases the domain wall width. The latter is found to present a perfect scaling with the length-scale of the interaction between domain wall and disorder, ξ. On the other hand, the strength of the domain wall–disorder interaction, fpin, is weakly impacted by the irradiation, suggesting that the length-scales of the disorder fluctuation remain smaller than the domain wall width.
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This paper presents a new approach to the classical design and implementation of a Lock-In Amplifier (LIA) applied to impedance measurement of resistances, capacitances, inductors and their arrangements. It is based on a general-purpose... more
This paper presents a new approach to the classical design and implementation of a Lock-In Amplifier (LIA) applied to impedance measurement of resistances, capacitances, inductors and their arrangements. It is based on a general-purpose microcontroller and an active band-pass filter. Instead of using a phase sensitive detector (PSD), the proposed LIA uses subtraction between samples to recover in-phase and in-quadrature. The design uses a low frequency Pulse Width Modulation (PWM) as source for the reference signal and an Analog to Digital Converter (ADC) from the microcontroller to sample the device under test (DUT) signal. In the particular context of this study, the results are limited to discrete components with relative error around 10%, which rises with higher impedance magnitudes. The measurement error pattern observed in RC, RL and LCR is also presented in this paper in order to emulate practical applications.
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Ampacity is defined as the maximum current carrying capacity of an electrical conductor without compromising its physical integrity. A possible methodology for the monitoring of this parameter in transmission lines consists in the... more
Ampacity is defined as the maximum current carrying capacity of an electrical conductor without compromising its physical integrity. A possible methodology for the monitoring of this parameter in transmission lines consists in the distribution of punctual temperature sensors along the line. This paper presents the development of electronic instrumentation for a current and temperature monitoring equipment to be applied in 230 kV power transmission lines. The chosen current transducer is the Rogowski Coil because of its linear response and decoupling between the measurement and power circuits, while the chosen temperature transducer is the NTC (Negative Temperature Coefficient) thermistor because of its low cost and high sensitivity. The developed prototype dos not use batteries or solar panels as power supply, as it is energized by the voltage induced in a secondary coil coupled to the transmission line. In order to increase the signal-to-noise ratio (SNR) and ensure electromagnetic compatibility (EMC), the hardware was developed and validated through numeric simulations and experimental measurements. Furthermore, digital noise reduction techniques such as oversampling and waveform averaging algorithms were implemented in the system. The developed equipment is theoretically able to measure electrical currents up to 1650 A, and was validated for currents up to 500 A and temperatures up to 90 °C. All collected data is transmitted to a computer for further analysis via wireless communication.
Research Interests: Ampacity()
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The objective of this work was to design a automate system for microalgae cultivation on a continuous modes in laboratory scale and allow its remote monitoring and control. For this, a sensor were developed is able to measure biomass... more
The objective of this work was to design a automate system for microalgae cultivation on a continuous modes in laboratory scale and allow its remote monitoring and control. For this, a sensor were developed is able to measure biomass concentration. The concentration sensor used the principle of light scattering, that is, by measuring the turbidity of the culture medium by the use of a set of phototransistor and green led. It presented an mean absolute percentage error of 8.46% during the experiment. A pH, temperature and light sensor were also installed. The control of all the sensors was accomplished by means of an microcontroller. For remote control and monitoring of the controller, a database was designed and implemented on a Raspberry Pi connected to the network. The graphics and data collected are available on an HTML page that allows changes in the control mode of the photobioreactor, for example by changing the dilution rates. The controller was able to operate the photobiore...
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The domain wall dynamics driven by an out of plane magnetic field was measured for a series of magnetic trilayers with different strengths of the interfacial Dzyaloshinskii-Moriya interaction (DMI). The features of the field-driven domain... more
The domain wall dynamics driven by an out of plane magnetic field was measured for a series of magnetic trilayers with different strengths of the interfacial Dzyaloshinskii-Moriya interaction (DMI). The features of the field-driven domain wall velocity curves strongly depend on the amplitude of the HD field stabilising chiral Neel walls. The measured Walker velocity, which in systems with large DMI is maintained after the Walker field giving rise to a velocity plateau up to the Slonczewski field HS, can be easily related to the DMI strength. Yet, when the DMI field HD and the domain wall demagnetising field HDW have comparable values, a careful analysis needs to be done in order to evaluate the impact of the DMI on the domain wall velocity. By means of a one-dimensional model and 2D simulations, we successfully extend this method to explain experimental results to cases where HD and HDW are comparable.
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The influence of magnetic anisotropy on nanosecond magnetization reversal in coupled FeNi/Cu/Co trilayers was studied using a photoelectron emission microscope combined with x-ray magnetic circular dicroism. In quasi-isotropic samples the... more
The influence of magnetic anisotropy on nanosecond magnetization reversal in coupled FeNi/Cu/Co trilayers was studied using a photoelectron emission microscope combined with x-ray magnetic circular dicroism. In quasi-isotropic samples the reversal of the soft FeNi layer is determined by domain wall pinning that leads to the formation of small and irregular domains. In samples with uniaxial magnetic anisotropy, the domains are larger and the influence of local interlayer coupling dominates the domain structure and the reversal of the FeNi layer.
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The installed length of nails and ground anchors widely used in retaining structures should be known in order to verify design and to ensure slope stability. Non-destructive techniques have been used to evaluate retaining wall buried... more
The installed length of nails and ground anchors widely used in retaining structures should be known in order to verify design and to ensure slope stability. Non-destructive techniques have been used to evaluate retaining wall buried steel bars. Sonic Echo and Impulse Response techniques evaluate the bar length using sonic wave propagation through an impact performed by the test operator with a hammer. Results may be affected by this non-standard procedure. This paper aims to propose an automated sonic wave generation in order to carried out quick test with reproducibility and without operator dependence. An electromagnetic launching system was developed, which uses a projectile in place of the hammer and the electromagnetic force instead of human force. The system details are presented in this study and the projectile output speed optimization and impact reproducibility are analyzed. The sonic data was received by a microphone, which was digitized and sent to the computer by a micr...
Dans cette these nous avons developpe trois techniques de mesures dynamiques du renversement de l'aimantation a l'echelle de la nanoseconde en utilisant des micro bobines comme source de champ pulse. Le comportement dynamique de... more
Dans cette these nous avons developpe trois techniques de mesures dynamiques du renversement de l'aimantation a l'echelle de la nanoseconde en utilisant des micro bobines comme source de champ pulse. Le comportement dynamique de plusieurs systemes magnetiques sous la forme de couches minces a ete etudie. Avec la technique de Dichroisme Circulaire Magnetique de Rayons X (XMCD) resolu en temps developpee a l'ESRF on obtient la selectivite en espece chimique outre a une resolution temporelle de 100 ps. Cela nous a permis d'effectuer des etudes du renversement de l'aimantation et du couplage dynamique dans des structures du type vanne de spins et jonctions tunnel. Dans certaines conditions de champ pulse le temps de renversement de l'aimantation de la couche libre (FeNi) est de l'ordre de la nanoseconde. Dans ces structures, suivant l'epaisseur de la couche non magnetique, le couplage dynamique entre les couches libre et dure peut etre tres different de c...
Remote control of the interaction of magnetic nanoparticles with cells is fundamental to any potential downstream applications of magnetic nanoparticles such as gene and drug delivery vehicles and magnetic cell labeling. Thus, approaches... more
Remote control of the interaction of magnetic nanoparticles with cells is fundamental to any potential downstream applications of magnetic nanoparticles such as gene and drug delivery vehicles and magnetic cell labeling. Thus, approaches based on the application of external magnetic fields to increase the efficiency of magnetic cell labeling are desirable. Here, we report a simple approach that enhances magnetic cell labeling using pulsed magnetic fields. The rate of uptake of superparamagnetic iron oxide nanoparticles (SPIONs) and transport across the cell membrane were enhanced upon application of a high intensity (7 T) short pulse width (∼15 μs) magnetic field. We present a quantitative analysis and mechanistic explanation of how a pulsed magnetic field influences the uptake of SPIONs by cells. Our findings offer insights into the mechanics of how pulsed magnetic fields can be effectively used to optimize magnetic cell labeling, which can provide a basis for better controlled biomedical applications of...
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Lysosome-activated apoptosis represents an alternative method of overcoming tumor resistance compared to traditional forms of treatment. Pulsed magnetic fields open a new avenue for controlled and targeted initiation of lysosomal... more
Lysosome-activated apoptosis represents an alternative method of overcoming tumor resistance compared to traditional forms of treatment. Pulsed magnetic fields open a new avenue for controlled and targeted initiation of lysosomal permeabilization in cancer cells via mechanical actuation of magnetic nanomaterials. In this study we used a noninvasive tool; namely, a benchtop pulsed magnetic system, which enabled remote activation of apoptosis in liver cancer cells. The magnetic system we designed represents a platform that can be used in a wide range of biomedical applications. We show that liver cancer cells can be loaded with superparamagnetic iron oxide nanoparticles (SPIONs). SPIONs retained in lysosomal compartments can be effectively actuated with a high intensity (up to 8 T), short pulse width (~15 µs), pulsed magnetic field (PMF), resulting in lysosomal membrane permeabilization (LMP) in cancer cells. We revealed that SPION-loaded lysosomes undergo LMP by assessing an increase...
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A ressonância magnética nuclear (RMN) encontra inúmeras aplicações em Física, Química, Engenharia e Medicina. Ela é utilizada sobretudo na análise de composição e estrutura de materiais, tanto sólidos quanto líquidos, e na realização de... more
A ressonância magnética nuclear (RMN) encontra inúmeras aplicações em Física, Química, Engenharia e Medicina. Ela é utilizada sobretudo na análise de composição e estrutura de materiais, tanto sólidos quanto líquidos, e na realização de imagens tomográficas, na área médica, sem a necessidade de submeter o paciente à qualquer tipo de radiação ionizante. O objetivo do presente trabalho é apresentar para estudantes de Física, Química e Engenharia os conceitos físicos básicos da ressonância magnética nuclear, utilizando a mecânica quântica para deduzir as equações de Bloch e apresentar suas soluções em regime de alto campo magnetostático. As condições necessárias para possibilitar o emprego dessa técnica na prática, utilizando a ressonância do próton, serão discutidas em linhas gerais.
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An approach to incorporate the nonlinear equivalent circuit model of a Schottky diode in finite element time domain simulations is proposed. The approach consists in decoupling the linear system of equations resulting from the finite... more
An approach to incorporate the nonlinear equivalent circuit model of a Schottky diode in finite element time domain simulations is proposed. The approach consists in decoupling the linear system of equations resulting from the finite element method and the nonlinear equations of the diode model. It is shown by numerical experiments that the approach is valid for practical diode parameters.