Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signa... 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.
High performance permanent magnets are key components in the development of more efficient electr... more 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.
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signa... 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.
Spiking neural networks (SNNs) first came to the attention of scientists due to the search for a ... 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.
This paper presents a new approach to the classical design and implementation of a Lock-In Amplif... 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.
Soil nailing system is widely used along highways in Brazil. Non-destructive techniques have been... 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.
High magnetic fields are required for the study of hard magnetic materials and, in many cases, th... 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.
In this article we present three techniques developed by our group for probing magnetization dyna... 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.
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signa... 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.
High performance permanent magnets are key components in the development of more efficient electr... more 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.
Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signa... 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.
Spiking neural networks (SNNs) first came to the attention of scientists due to the search for a ... 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.
This paper presents a new approach to the classical design and implementation of a Lock-In Amplif... 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.
Soil nailing system is widely used along highways in Brazil. Non-destructive techniques have been... 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.
High magnetic fields are required for the study of hard magnetic materials and, in many cases, th... 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.
In this article we present three techniques developed by our group for probing magnetization dyna... 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.
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Papers by Marlio Bonfim