Voltage Amplitude Research Articles

Investigation on optical and electrical properties of soil discharge under pulse voltage

Many researchers have studied the application of low temperature plasma in soil remediation, but most focus on the degradation efficiency of a specific pollutant, and less attention is paid to the development and evolution process of plasma behind the soil remediation. In this paper, the possible mechanism behind soil discharge under pulse voltage is studied from the perspectives of electricity and optics. The electrical and optical analyses show that the soil discharge under pulse voltage mainly exists at the rising stage of pulse voltage, and the existence time is related with the pulse voltage amplitude. At the same time, the relative intensity of active substances (•OH, H, O Ⅱ and N Ⅰ), vibration temperature and rotational temperature are obtained by using the emission spectrum, which demonstrate that high pulse voltage can increase the concentration of active substances, vibration temperature and rotational temperature.

Experimental investigation of the radially-dependent ignition process in a pulsed capacitively coupled RF discharge: Effects of pressure, voltage and afterglow duration

The effects of the gas pressure, the voltage amplitude and the afterglow duration on the ignition process over 300 mm-diameter in a pulse-modulated capacitively coupled radio-frequency argon discharge are experimentally investigated. A home-made optical probe is used to measure the optical emission intensity (OEI) as a function of time since the beginning of each pulse at various radial positions. A voltage and a current probe are used to measure the voltage and current waveforms at the power feeding point and then the time-dependent power deposition is also obtained. It was found that the radial profile of the OEI exhibits complex evolution when changing these external conditions. At lower pressures, the ignition occurs earlier, and the radial-integral OEI and the power deposition overshoot more slightly during the ignition. By increasing the pressure, these two quantities overshoot more significantly, and the OEI gradually evolves from an edge-peaked radial profile to a center-high radial profile for a given time when the OEI increases rapidly during the ignition. When increasing the voltage amplitude, the ignition tends to occur earlier, featuring a more significant overshoot of the OEI and power deposition at a higher voltage. Compared to that at high voltage, the OEI exhibits a significant center-high radial profile at low voltage amplitude during the ignition. By increasing the afterglow duration, T off, the ignition is delayed and the overshoot becomes more significant, due to a lower initial electron density when each pulse is turned on. During the phase when the growth rate of the OEI versus time is maximum, the OEI exhibits different radial distributions, i.e., it appears a center-high profile at short T off, an edge-peaked profile at intermediate T off, and a center-high profile at relatively long T off.

Study on the measurement method of polyimide electrical properties for flexible solar wing

AbstractFlexible solar wings with high energy density, lightweight, small size and large deployment area are one of the first choices for next‐generation spacecraft. However, the flexible solar wings are subjected to irradiation in space and tensile mechanical stress, which produce the charge accumulation effect and result in electrostatic discharge. It is necessary to establish a test method for the conductivity and space charge behaviour of polyimide under tensile stress. The stress–strain characteristics of polyimide under different tensile stresses are studied by the authors. The longitudinal length‐strain characteristics and transverse thickness evolution characteristics under different stresses are also obtained. The results show that the variation of film thickness with tensile force is only about 1% before the yield point. The polyimide films from 50 to 200 μm thick have similar yield and tensile strengths. The ultimate stress of the specimen decreases from approximately 126 to 103 MPa with increasing thickness. The thickness model of polyimide under tensile stress were obtained, which could accurately calculate the voltage amplitude applied on the specimens for measuring the conductivity under different tensile stresses. A basis for investigating the stress–strain characteristics of polyimide films under different tensile stresses are provided, which will facilitate the formulation selection and performance improvement of polyimide for flexible solar wings of spacecraft.

A New Method in Applying the Universal Wave Equation to Measure the Speed of Sound in Water as a Function of Temperature with Low Frequency Ultrasound

A new methodology was used to determine the speed of sound in water by using low frequency ultrasound over the temperature range 20 to 95° C. The initial procedure was developed based on finding the resonant locations over variable pathlengths in an acoustic tube and calculating their separation distances through the water, yielding the wavelength (λ) measurement. An in-house gain detector was employed to detect the resonant points, through detection of the amplitude voltage peaks in response to the displacement of the moving transmitter. The λ was calculated as 53 mm for water at 20° C with the fixed frequency of 28 kHz. As a result, using the universal wave equation, the speed of sound was estimated to be 1484 m/s with an accuracy of 99.89% compared to the references. The methodology was then followed through the second procedure to measure the sound speeds at temperatures higher than 20 °C, using coincidence frequency determination over different temperatures. In a fixed acoustic pathlength equal to the calculated λ at 20° C, the initial frequency, 28 kHz, was linearly swept to track the coincidence frequency corresponding to certain temperatures. The gain detector was used to obtain the coincidence frequencies, wherein the amplitude voltage peaks were recorded during the frequency adjustment. The simultaneous monitoring with an oscilloscope consolidated data when the phase differences between radiated and received waves were eliminated at the coincidence frequencies. The measured coincidence frequencies were then directly used to determine the speed of sound in water as function of temperature. The third order curve fitted to the results yielded an R2 equal to 0.9856, representing excellent agreement with the reference data.

A novel method for measuring body bioimpedance and its FPGA implementation

One of the most promising methods for assessing human tissue and diagnosing diseases is to measure the bioimpedance of the body. They have been various methods presented for achieving this goal. The most important point is measuring the phase along with the amplitude. On this basis, a field-programmable gate array (FPGA) is used in this study to measure the accuracy in amplitude and phase. At the first, a frequency spectrum is applied to the body model, then an algorithm in the VHDL compiler determines the amplitude of the output voltage. The phase change is measured by using direct digital measurement (DDM), and the product displayed in degrees or radian units. Subsequently, an FPGA model of the body has been simulated by using a lookup table (LUT) and various dependent circuits. FPGA-based hardware implementation is conducted by using Xilinx ISE 14.7 software, in which the chip selected for implementation is xc7z0203clg484. In this regard, the phase has detected. It's using an XOR gate, which consumes less power and hardware compared to flip-flop detectors. This novel phase measurement technique eliminates that needs for an exact adjustment of the clock, which increases measurement accuracy and reduces error. In the analysis of simulation results and theoretical values, the amount of the error has been calculated and plotted. As a result, the advantages of this method include being highly accurate, requiring little hardware, being flexible when changing the circuit, and consuming very little power.

Cycling Waveform Dependent Wake-Up and ON/OFF Ratio in Al2O3/Hf0.5Zr0.5O2 Ferroelectric Tunnel Junction Devices.

The wake-up behavior and ON/OFF current ratio of TiN-Al2O3-Hf0.5Zr0.5O2-W ferroelectric tunnel junction (FTJ) devices were investigated for different wake-up voltage waveforms. We studied triangular and square waves, as well as square pulse trains of equal or unequal voltage amplitudes for positive and negative polarities. We find that the wake-up behavior in these FTJ stacks is highly influenced by the field cycling waveform. A square waveform is observed to provide wake-up with the lowest number of cycles, concomitantly resulting in higher remnant polarization and a higher ON/OFF ratio in the devices, compared to a triangular waveform. We further show that wake-up is dependent on the number of cycles rather than the total time of the applied electric field during cycling. We also demonstrate that different voltage magnitudes are necessary for positive and negative polarities during field cycling for efficient wake-up. Utilizing an optimized waveform with unequal magnitudes for the two polarities during field cycling, we achieve a reduction in wake-up cycles and a large enhancement of the ON/OFF ratio from ∼5 to ∼35 in our ferroelectric tunnel junctions.

Synergistic effect of multi-parameters on NO density of a helium atmospheric pressure plasma jet in contact with skin

Nitric oxide (NO) is a crucial molecule for living organisms, which acts as a messenger in most mammalian organs. Fortunately, plasma jet can generate an abundant amount of NO. In this paper, the NO generated by a helium plasma jet when it is interacting with pig skin is diagnosed using laser-induced fluorescence (LIF) method. The multi-parameters’ effect of the distance between the nozzle and the skin surface (distance d), the gas parameters (gas flow rate, O2 and H2O percentage) and the applied voltage parameters (the amplitude and frequency of the voltage) on the NO density is explored. The results show that the NO density increases and then decreases as the gas flow rate increases. The gas flow rate corresponding to the maximum NO density is positively correlated with the distance d. In the case of high gas flow rate or small distance d, premixing a small amount of O2 or H2O content lead to higher NO density. Higher voltage amplitude and frequency can increase NO density, but high voltage amplitude at high flow rate and small distance d lead to a decrease in NO density. The generation pathway of NO is mainly affected by N2(A), N, O2, O, OH, H and NO2, and the consumption pathway is closely related to the particles N, O, OH, O3 and HO2. Among them, N and O atoms participate in both generation and consumption. Therefore, the synergistic effect of multi-parameters, the emergence of different effects is closely related to the synergistic effect of these two particles.

A novel CVD graphene-based synaptic transistors with ionic liquid gate

The synaptic devices based on various electronic materials have been widely investigated to realize functions of artificial information processing with low power consumption. In this work, a novel CVD graphene field-effect transistor is fabricated with ionic liquid gate to study the synaptic behaviors based on the electrical-double-layer mechanism. It is found that the excitative current is enhanced with the pulse width, voltage amplitude and frequency. With different situations of the applied pulse voltage, the inhibitory and excitatory behaviors are successfully simulated, at the same time the short-term memory is also realized. The corresponding ions migration and charge density variation are analyzed in the different time segments. This work provides the guidance for the design of artificial synaptic electronics with ionic liquid gate for low-power computing application.

A New Approach for Long-Term Stability Estimation Based on Voltage Profile Assessment for a Power Grid

Load flow solutions refer to the steady-state stability of power systems and have a crucial role in the design and planning of slow-changing elements; e.g., in online tab changing actions, automatic generation control, over-excitation limiters and the power recovery characteristics of a load. Therefore, the purpose of this work was to show the connectivity between load flow analysis and long-term voltage stability using a generator model by introducing a novel voltage stability assessment based on the multi-machine dynamic model along with the load flow study for a power grid. The Euclidean distance (ED) was used to introduce a new voltage stability index based on the voltage phasor profile for real-time monitoring purposes. The effects of reactive power compensation, in addition to load-generation patterns and network topology changes in the system behavior, could be seen clearly on the voltage profiles of the buses. Thus, the increased values for the EDs of the buses’ voltage amplitudes—from 0 to around 1.5 (p.u.)—implied that the system was approaching the voltage collapse point, corresponding to the Jacobian matrix singularity of the load flow equation. Moreover, the weakest load bus with respect to any system change was also identified. Indeed, the criticality of any network interruption was in direct proportion to this voltage stability index. The proposed method was validated using the IEEE 118-bus test system.

A new modulation strategy on isolated battery charger with wide input and output voltage range

AbstractA new wide voltage operation range isolated battery charger, which is composed of an asymmetric T‐type AC–DC power rectifier and a modified re‐configurable half bridge DC–DC power converter, is proposed in this paper. The asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages for increasing power conversion efficiency. As the isolated DC–DC power stage, a modified re‐configurable half bridge converter applies a three‐winding transformer to achieve a wide output operation range. The proposed battery charger operates over a wide AC input voltage range and wide DC output voltage range. A 3.2 kW hardware battery charger prototype is built to adapt AC voltage between 85 and 265 V. Both constant current and constant voltage modes are implemented experimentally to charge the battery up to 6.5 A from 50 to 500 V. The experimental results prove that the proposed asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages can increase the power conversion efficiency, the proposed DC–DC converter can output the DC voltage from 50 to 500 V and the proposed battery charger can achieve around 94% efficiency.

О возможности реализации нелинейного радиолокатора с обработкой на частоте зондирующего сигнала

The conditions for the implementation of a nonlinear radar using a probing signal having a form as a periodic sequence of pairs of radio pulses with different amplitudes and equal energies, are considered. The energies of the reflected pulses are compared in the locator receiver for each pair, which makes it possible to detect reflections from nonlinear devices at the probing signal frequency by violating the equality of these energies. A numerical experiment was performed to evaluate the dependence of the current form through germanium and silicon diodes and their amplitude parameters at the frequency of the acting sinusoidal voltage with variable amplitude. As a result, it was found that the amplitude nonlinearity can be detected before the diode is completely "opened" if the two voltage amplitudes on the diode differ from each other by at least one and a half to two times. Since the pulse energies are proportional to their powers, and the pulse durations are unchanged, it should be possible to detect non-linearity by determination of a ratio between the radar cross-sections of non-linear objects for different pulse amplitudes. To obtain quantitative estimates, a simulation of the incidence of a flat, linearly polarized wave on a half-wavelength dipole and a half-wavelength folded dipole loaded with a diode was performed. It was found that the model type and parameters significantly affect both the values of the radar cross-sections and the degree of influence of nonlinearity on these values, so that the detection of non-linearity requires significantly higher power levels of the probing signal than the theory predicts.

Simulation Research of three phase bridge PWM Inverter based on MATLAB

The sole method available to humans for precise control of power energy is power electronic technology, which is also a key trend in developing the future power system and the entire energy structure. PWM control technology regulates the pulse signal’s width, and this circuit can alter the fundamental amplitude and form of the input voltage. This study will evaluate the three-phase inverter circuit’s operating principle, develop its control strategy, create a SIMULINK simulation model, and do a rough analysis using an LC filter.

Exploring the mechanisms leading to diffuse and filamentary modes in dielectric barrier discharges in N_2 with N_2O admixtures

The effects of nitrous oxide (N_2O) in nitrogen (N_2) on the development and morphology of sine-driven dielectric barrier discharges in a single-filament arrangement were studied. Detailed insight in the characteristics of the discharge and its development were obtained from electrical measurements combined with ICCD and streak camera recordings as well as numerical modelling. A miniaturised atmospheric pressure Townsend discharge (APTD) could be generated for admixtures up to 5 vol% N_2O in N_2 although N_2O is an efficient collisional quencher of metastable nitrogen molecules. Increasing the high voltage amplitude led to a transition into a hybrid mode with the generation of an intermediate filament in addition to the diffuse, non-constricted APTD. A time-dependent, spatially one-dimensional fluid model was applied in order to study the underlying mechanisms causing the diffuse discharge characteristics. It was found that even for small N_2O admixtures, the associative ionisation of atomic nitrogen and oxygen (O + N(^2P) rightarrow NO^+ + e) is the major electron source sustaining the volume memory effect and is therefore the reason for the formation of a diffuse APTD.Graphical abstract

Dual, Three-Level, Quasi-Z-Source, Indirect Matrix Converter for Motors With Open-Ended Windings

In this paper, a novel variable-voltage, variable-frequency, dual, three-level, quasi-Z-source, indirect matrix converter topology is proposed, including a detailed description of a modulation method and a control strategy for three-phase motors with open-ended windings. The proposed power drive system (PDS) supports bidirectional power flow and has a combined control of DC-link voltage and output AC voltage frequency. Experimentally validation was performed on a 4-kW PDS. For a given supply voltage amplitude and the same power switch voltage rating in the DC/AC converter, the proposed PDS can double the voltage output gain, thus being an interesting solution for high-power applications with motors designed for higher voltages. The proposed PDS topology, modulation method and motor control strategy can reduce the common-mode component, low-order harmonic content, peak values and d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> of the motor phase voltage, ultimately leading to lower winding insulation voltage stress at low-speed, low-voltage operation, lower harmonic losses in the motor, and ride-through capability over voltage sags in the mains, which are important advantages.

Dynamic Direct Voltage MTPA Current Sensorless Drives for Interior PMSM-Based Electric Vehicles

This research presents a current sensorless dynamic direct voltage method based on the maximum torque per ampere (MTPA) technique to control the rotor speed of interior permanent magnet synchronous motors (IPMSMs) for electric vehicle (EV) applications. It considers the dynamic model of the machine and generates a particular pair of voltage amplitude and its angle to track the speed profile of the driving cycle. The proposed control strategy contributes by eliminating the need for a current sensor, avoiding cascaded PI controllers, and overcoming the limitations of transient states. Consequently, the measurement noise and equipment failure do not affect the control loop, the tuning of a single PI controller becomes much simpler than two cascaded PI controllers, and the absence of MTPA tracking and current or voltage overshooting at transient states cannot limit the performance of the control technique. Additionally, the aforementioned modifications improve the response time of the proposed strategy and make it nimble enough for EV applications. A comparative analysis is carried out on the proposed current sensorless dynamic direct voltage MTPA control, simplified dynamic direct voltage control (S-DDVC), and the field oriented control (FOC) models. The outcomes confirm that the introduced model substantially reduces the inrush current and voltage. Experimental results with quantitative tracking and energy consumption assessments reveal that the proposed method demands 9.7% lower energy than the FOC counterpart in urban driving plans by operating IPMSM in high efficiency region.

Discharge in air in contact with water: influence of electrical conductivity on the characteristics and the propagation dynamics of the discharge

Due to the high reactivity and the non-thermal properties of streamer discharges, they are applied in various fields, such as water treatment and medicine. Streamer discharges are usually produced in the gas phase before interacting with a liquid or solid surface. Although the dynamics of a streamer discharge in gases is well described, its propagation at liquid surfaces remains poorly understood. In this study, we investigate the influence of water electrical conductivity (σ), between 2 and 1000 µS cm−1, on the characteristics and propagation dynamics of pulsed positive DC nanosecond discharges with the solution serving as a cathode. σ strongly influences τ r (the dielectric relaxation time), and two discharge modes may be obtained, depending on whether τ r is shorter or longer than the delay to achieve breakdown (τ pulse). This latter can be indirectly modified by adjusting the voltage amplitude (V a). In the case of V a = 14 kV, the breakdown voltage (V bd) at low σ is lower than that measured at high σ, probably because τ pulse < τ r and > τ r, respectively. In the case of V a = 20 kV, V bd decreases slightly with σ, probably because of the decrease of the resistivity of the global electrical circuit as τ pulse ∼ τ r for high σ. In addition to the electrical characterization, the dynamics of the discharge at the solution’s surface is investigated using 1 ns-time-resolved imaging. Its morphology was found to evolve from a disc to a ring before it splits into highly organized plasma dots (streamers’ head). The number (N dots) and propagation velocity of plasma dots are determined as a function of σ. At V a = 14 kV, N dots does not vary significantly with σ despite the increase of V bd; this latter likely compensates the neutralization of charge accumulated at the surface by ions in solution. In the case of V a = 20 kV, N dots decreases with σ, and it can be related to a decrease of accumulated charge at the water surface. Finally, based on the electrical measurements, we found that the charge per plasma dot (Q dot) increases with σ, which does not correlate with the imaging results that show a short length of propagation at high σ. Then, considering the plasma dot mobility at low σ and the instantaneous propagation velocities at high σ, a more realistic Q dot is measured.

Artificial TMAP Signal Generator Based on One-Bit Sigma Delta Modulator for MEC Test

The current study proposes three electrode-channels with time delay of artificial nerve signals generator utilized with only a active low pass filter and a Field Programmable Gate Array (FPGA). The XC3S100E FPGA board adopted to design a novel and real-time artificial transmembrane action potential (TMAP). The implementation of one bit Sigma Delta Modulation (SDM) method with linearized technique could be very expensive and complicated products with other technologies option currently available such as a microcontroller due to the fabrication requirements. This technique could employ in many biomedical applications and testing efficiently, especially, in evaluating the multi-electrode cuff system without requiring use of real nerves spike from animal models and saving time and effort, and cost. Moreover, this approach is adopted for further improvement to the signal performances such as resolution, accuracy, differential linearity monotonic DAC, and settling time of the signal waveform without extra hardware or cost required. In addition, the design included three channels of white Gaussian noise uncorrelated for each TMAP signal to simulate the real nerve noise environment, which surrounds the electrode cuff in experimental cases. A noise channels with adjustment level is added to the nerve spike using three sets of taps are employed to provide three channels of noise sources. The Xilinx ISE platform and Mentor Graphics ModelSim tool are used to simulate and implement this, and the results produced are compared. The power consumption of conventional technology is 31 mW, which is significantly higher than the power consumed (21mW) in modern technology. Furthermore, as compared to the usual way, the proposed solution conserved around 10% of the FPGA resources. This technique offers reuse in other applications where delay time, low amplitude voltage signals, and multichannel generator is needed. Moreover, this system offers adjustable waveform signal, noise level, conduction velocity and time delay easily to adequate different applications and tests.

Grid-Forming Converter Overcurrent Limiting Strategy Based on Additional Current Loop

Compared with current source converters, voltage source converters (grid-forming converters) have better frequency support capabilities, voltage support capabilities, and regulation performance, thus they have broad application prospects. However, the grid-forming (GFM) converter has insufficient current control ability, and it easily causes problems such as overcurrent issues when a fault occurs. Thus, this insufficiency is one of the most important challenges the GFM converter is faced with. Aiming to solve the problems mentioned above, this paper proposes a control method of a GFM converter achieved with a low-pass filter structure and an additional current loop. The additional current loop controls the dq-axis current components by acting on the outer loop to generate appropriate phase and voltage amplitude reference. The low-pass filter structure is used to solve the system frequency stability problem caused by the inclusion of the additional current loop. On the premise of ensuring that the system frequency meets the grid-connection requirements, the proposed strategy rapidly limits the output current within the allowable range and guarantees expected voltage source characteristics of the converter during the fault period. Finally, the effectiveness and superiority of the proposed control strategy are verified by MATLAB/Simulink simulations.

Analysis of the working mechanism and detection sensitivity of a flash detector

Abstract Flash detectors are mainly used to detect the brief light flashing when projectiles are launched or exploded in the air. They can output trigger pulse signals in real time to start a test instrument and carry out data collection. Because flash detectors cannot work reliably under strong background light radiation, this work studied the flash detector mechanism. The influence of background light radiance, lens aperture, and detection distance on the effective signal was analyzed, a mathematical model of detection sensitivity based on the background radiation brightness control was proposed, a mathematical formula of the detection distance of the flash detector was deduced, and the optimal working conditions were obtained. The researched model was verified by simulation analysis and actual test experiments, in the same external circumstances, the limit detection distance of the optimal aperture compared to the maximum aperture increased by 20%, and the effective signal voltage amplitude was twice the amplitude at the maximum aperture, and the results showed the correctness of the analysis. The proposed detection sensitivity model can be applied for a dynamic photoelectric detection instrument, which broadens its potential application in the engineering field.

Energy harvesting of nanofluid-conveying axially moving cylindrical composite nanoshells of integrated CNT and piezoelectric layers with magnetorheological elastomer core under external fluid vortex-induced vibration

This paper deals with the renewable energy that can be harvested as electrical voltage due to the vibrations of an axially moving composite nanoshell conveying nanofluid. The significance of the study and its main innovation is the investigation of the possibility of yielding electrical energy caused by natural mechanical vibrations in a smart dynamic composite nanostructure, which can have potential applications in the nano industry. To this end, oscillations of nanocomposite interacting with the internal nanofluids are investigated under both non-periodic and the harmonic excitations of an external vortex fluid flow colliding with the outer layer, as a natural phenomenon. The considered composite nanoshell consists of three integrated layers of piezoelectric, magnetorheological elastomer, and carbon nanotube. As a theoretical methodology, using the Navier-Stokes equations and energy method, the governing coupled mechanical–electrical equations of dynamic composite nanoshells are derived based on the Euler-Bernoulli beam theory applying nonlocal-piezo-elasticity theory utilizing the van der Pol equation for the external vortex shedding flow. The vortex fluid flow leads to the appearance of the added mass and damping terms in the motion equations. The effects of velocities of moving nanocomposite, passing internal nanofluid, and external vortex fluid, the effects of nano-scale structure and aspect ratio, the effect of applied magnetic field intensity on the smart middle layer, the internal and external fluid densities effects (gas/liquid), and the effect of electrical resistive load on the frequency response and the output voltage amplitude of the dynamic nanosystem are also studied. As one of the significant obtained results, it is revealed that the output voltage due to the vortex-induced vibration (VIV) of the nanosystem will significantly increase as the densities of both internal fluid flow and external vortex fluid flow decrease. In addition, the extractable voltage can be increased or decreased by controlling the intensity of the magnetic field through its effect on the magnetorheological layer.