electrical circuit
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Abstract In floating catalyst chemical vapor deposition (FCCVD), when a carbon nanotube (CNT) network film is produced by filter collection, the film thickness is adjusted by controlling the collection time. However, even with consistent synthesis parameters, the synthesis condition in FCCVD changes constantly depending on the carbon and catalyst adhesion to the inner wall of the reaction tube. Thus, the rate of synthesis changes, making it difficult to obtain the target film thickness repeatedly and stably. We propose a method of monitoring CNT film thickness and percolation threshold by the in situ measurement of the electrical impedance during the deposition. The time evolution of the measured impedance is reproducible by an equivalent electrical circuit simulation.

Abstract At present, the machining performance of the existing EDM technology depends upon the commonly used pulsed power supply and gap control mechanism. The complexity and the higher cost of the above said vital components, reflected in the product cost. A simple electrical circuit has been applied to control the voltage and the electric magnet so that the tool electrode can levitate over the workpiece at the desired distance (electrode gap). A prototype is fabricated with the DC power supply and the maglev levitation mechanism. To evaluate novel maglev EDM technology with the existing EDM technology, experiments were conducted on Ti-6Al-4V alloy with a brass tool. The discharge waveform of maglev EDM has shown the discharge voltage and current and the absence of short-circuit at high duty factor. A predictive model is formulated by dimensional analysis based on MRR and average surface roughness. The experimental result of conventional EDM from the literature were used to prepare the model. The maglev EDM is showing higher MRR and surface roughness than the prediction. Surface morphology showed similar surfaces as formed in EDM. The specific energy analysis showed that the developed maglev EDM performs in reported data range. It is noted that the proposed technology is in its early stage and the performance is significantly comparable with the existing technology. Therefore, it is expected that the research in this area may help to develop an economically sustainable alternative to the existing costly and complex EDM technology.

Piezoelectric material has the ability to convert mechanical energy to electrical energy and vice versa, making it suitable for use as an actuator and sensor. When used as a controller in sensor mode, the piezoelectric transducer is connected to an external electrical circuit where the converted electrical energy will be dissipated through Joule heat; also known as piezoelectric shunt damper (PSD). In this work, a PSD is used to dampen the first resonance of a cantilever beam by connecting its terminal to an RL shunt circuit configured in series. The optimal resistance and inductance values for maximum energy dissipation are determined by matching the parameters to the first resonant frequency of the cantilever beam, where R = 78.28 k? and L = 2.9 kH are found to be the optimal values. To realize the large inductance value, a synthetic inductor is utilized and here, the design is enhanced by introducing a polarized capacitor to avoid impedance mismatch. The mathematical modelling of a cantilever beam attached with a PSD is derived and simulated where 70% vibration reduction is seen in COMSOL. From experimental study, the vibration reduction obtained when using the piezoelectric shunt circuit with enhanced synthetic inductor is found to be 67.4% at 15.2 Hz. Results from this study can be used to improve PSD design for structural vibration control at targeted resonance with obvious peaks. ABSTRAK: Material piezoelektrik mempunyai keupayaan mengubah tenaga mekanikal kepada tenaga elektrik dan sebaliknya, di mana ia sesuai digunakan sebagai penggerak dan pengesan. Apabila digunakan sebagai alat kawalan dalam mod pengesan, piezoelektrik disambung kepada litar elektrik luaran di mana tenaga elektrik yang ditukarkan akan dibebaskan sebagai haba Joule; turut dikenali sebagai peredam alihan piezoelektrik (PSD). Kajian ini menggunakan PSD sebagai peredam resonan pertama pada palang kantilever dengan menyambungkan terminal kepada litar peredam RL bersiri. Rintangan optimal dan nilai aruhan bagi tenaga maksimum yang dibebaskan terhasil dengan membuat padanan parameter pada frekuensi resonan pertama palang kantilever, di mana R = 78.28 k? dan L = 2.9 kH adalah nilai optimum. Bagi merealisasikan nilai aruhan besar, peraruh buatan telah digunakan dan di sini, rekaan ini ditambah baik dengan memperkenalkan peraruh polaris bagi mengelak ketidakpadanan impedans. Model matematik palang kantilever yang bersambung pada PSD telah diterbit dan disimulasi, di mana 70% getaran berkurang pada COMSOL. Hasil dapatan eksperimen ini menunjukkan pengurangan getaran yang terhasil menggunakan litar peredam piezoelektrik bersama peraruh buatan menghasilkan 67.4% pada 15.2 Hz. Hasil dapatan kajian ini dapat digunakan bagi membaiki rekaan PSD berstruktur kawalan getaran iaitu pada resonan tumpuan di puncak ketara.

The article is devoted to the development of the methodology for the controlled synthesis of protective coatings by the micro-arc oxidation method in order to improve the efficiency of this technology and the quality of the obtained oxide layers. Methodology includes a mathematical model of a galvanic cell based on an equivalent electrical circuit, as well as a model of the interconnections between the technological parameters of the micro-arc oxidation (MAO) process and the properties of the obtained oxide layers based on graph theory. The indicated dependences are formalized using methods of regression and correlation analysis of experimental data. A technique for the controlled synthesis of MAO coatings using the obtained regression equations is proposed. The structure and functioning algorithm of an intelligent automated system for the controlled synthesis of MAO coatings are developed. A prototype of this system was used to obtain experimental dependences of reaction parameters on the influence parameters of the micro-arc oxidation process.

With the recent increase in the use of augmented reality (AR) in educational laboratory settings, there is a need for new intelligent sensor systems capturing all aspects of the real environment. We present a smart sensor system meeting these requirements for STEM (science, technology, engineering, and mathematics) experiments in electrical circuits. The system consists of custom experiment boxes and cables combined with an application for the Microsoft HoloLens 2, which creates an AR experiment environment. The boxes combine sensors for measuring the electrical voltage and current at the integrated electrical components as well as a reconstruction of the currently constructed electrical circuit and the position of the sensor box on a table. Combing these data, the AR application visualizes the measurement data spatially and temporally coherent to the real experiment boxes, thus fulfilling demands derived from traditional multimedia learning theory. Following an evaluation of the accuracy and precision of the presented sensors, the usability of the system was evaluated with n=20 pupils in a German high school. In this evaluation, the usability of the system was rated with a system usability score of 94 out of 100.

This paper describes the output voltage regulation control for an interleaved connected to a direct current (DC) microgrid considering bidirectional current flows. The proposed controller is based on an interconnection and damping passivity-based control (IDA-PBC) approach with integral action that regulates the output voltage profile at its assigned reference. This approach designs a control law via nonlinear feedback that ensures asymptotic stability in a closed-loop in the sense of Lyapunov. Moreover, the IDA-PBC design adds an integral gain to eliminate the possible tracking errors in steady-state conditions. Numerical simulations in the Piecewise Linear Electrical Circuit Simulation (PLECS) package for MATLAB/Simulink demonstrate that the effectiveness of the proposed controller is assessed and compared with a conventional proportional-integral controller under different scenarios considering strong variations in the current injected/absorbed by the DC microgrid.

Ultrasound based haptic feedback is a potential technology for human-computer interaction (HCI) with the advantages of low cost, low power consumption and controlled force. In this paper, the phase optimization for multipoint haptic feedback based on ultrasound array is investigated and the corresponding experimental verification is provided. A mathematical model of acoustic pressure is established for the ultrasound array and then a phase optimization model for an ultrasound transducer is constructed. We propose a pseudo-inverse (PINV) algorithm to accurately determine the phase contribution of each transducer in the ultrasound array. By controlling the phase difference of the ultrasound array, the multipoint focusing forces are formed leading to various shapes such as geometries and letters that can be visualized. Because the unconstrained PINV solution results in unequal amplitudes for each transducer, a weighted amplitude iterative optimization is deployed to further optimize the phase solution, by which the uniform amplitude distributions of each transducer are obtained. For the purpose of experimental verifications, a platform of ultrasound haptic feedback consisting of a Field Programmable Gate Array (FPGA), an electrical circuit and an ultrasound transducer array is prototyped. The haptic performances of single point, multiple points and dynamic trajectory were verified by controlling the ultrasound force exerted on the liquid surface. The experimental results demonstrate that the proposed phase optimization model and theoretical results are effective and feasible, and the acoustic pressure distribution is consistent with the simulation results.

High sensitive (S = 11.2 ± 1.8 mV/V/kPa with nonlinearity error 2KNL = 0.15 ± 0.09%/FS) small-sized (4.00x4.00 mm2) silicon pressure sensor chip utilizing new electrical circuit for microelectromechanical systems (MEMS) in the form of differential amplifier with negative feedback loop (PDA-NFL) for 5 kPa differential was developed. The advantages are demonstrated in the array of output characteristics, which prove the relevance of the presented development, relative to modern developments of pressure sensors with Wheatstone bridge electrical circuit for 5 kPa range.