Amplitude Pulse Research Articles

Overcoming Printed Circuit Board Limitations in an Energy Harvester with Amplitude Shift Keying and Pulse Width Modulation Communication Decoder Using Practical Design Solutions

This paper presents PCB design solutions for implementing a radiative-field RF energy harvester with an ASK-PWM decoding communication scheme using available commercial components. The paper provides the design approach and tackles key challenges such as the impact of inductive parasitic effects at the output of the harvester, how to maintain the PCE at a constant value regardless of the time constant at the output of the communication path’s rectifier, and the difficulty of changing the aspect ratio of the discrete inverter used for PWM decoding. These challenges are addressed by using multiple capacitors connected in parallel at the output of the rectifier to reduce inductive parasitic effects, adding a series resistor in the communication path’s rectifier to isolate its loading from impacting the PCE, and utilizing a potentiometer in the inverter to realize PWM decoding on PCB. The system was manufactured using FR-4 substrate material with a size of 5 cm × 4 cm × 0.6 cm, harvesting energy at the ISM frequency of 924 MHz with a PCE of 42.12% at a bit rate of 15 Kbps. Moreover, the system consumes only 355 μW of power and maintains correct harvesting and decoding operation in the antenna separation range of 6–12 cm. This work aims to provide an alternative to IC realization by implementing the system entirely using commercial discrete components, reducing costs, adding flexibility, reducing development time, and allowing for simple debugging.

Extraction of chontaduro oil (Bactris gasipaes) for the synthesis of isopropyl esters through transesterification reactions assisted by ultrasound using green solvents

An experimental design study, using the Box-Behnken method with response surface methodologies (RSM), was conducted to evaluate the extraction process of chontaduro pulp (Bactris gasipaes) oil and its potential application in obtaining isopropyl esters through a transesterification process. The extraction of chontaduro oil and the transesterification reactions of the fatty esters were assisted by ultrasound techniques using n-hexane and isopropanol as environmentally friendly solvents. During the extraction process, the parameters evaluated were the sample to solvent ratio (w/w), power amplitude (%), and ultrasound pulse times (s). For the transesterification process, the parameters evaluated were ultrasound amplitude, ultrasound pulse time, and the amount of isopropanol (mol). The optimal conditions for the extraction process were found to be a sample to n-hexane ratio of 1:10 (w/w) and an ultrasound amplitude of 30%, with the pulse time not significantly affecting the oil yield of 15.02% achieved in a total time of 30 min. The predominant fatty acids in chontaduro oil were C18:1 cis oleic acid (54.31%) and C16:0 palmitic acid (20.40%). To synthesize isopropyl esters, we found that the ideal conditions are an ultrasound amplitude of 50%, an ultrasound pulse time of 20 s, and 0.4 moles of isopropanol. These conditions resulted in complete conversion within 45 min. The use of ultrasound radiation proved to be an alternative method to conventional techniques, reducing extraction and transesterification times, minimizing energy consumption, and increasing percentage yield. This contributes to green chemistry and the production of value-added products, potentially useful in the cosmetics industry.

Review on peak detect and hold circuits and their applicability in partial discharge detection

Abstract This article reviews various designs of electrical peak detect and hold circuits and tests their applicability for the detection of partial discharge pulses. Since partial discharges are very short pulses in the nanosecond range, the peak detector circuit must be very fast and thus work precisely over a wide bandwidth up to the GHz range. The article begins with a comprehensive literature review and gives an overview of the state of the art of peak detector circuits. As a result of the literature research, four different peak detector designs are identified that appear suitable for measuring partial discharges. These four circuits are then simulatively tested for their performance in measuring the pulse height of various partial discharge pulses. It turns out that two of the identified circuits are able to measure nanosecond pulses of small amplitude. These two circuits must be further optimized for partial discharge detection in the future. In addition, the circuit should be tested prototypically with real partial discharge pulses.

Optical Energy Increasing in a Synchronized Motif-Ring Array of Autonomous Erbium-Doped Fiber Lasers

This work investigates the enhancement of optical energy in the synchronized dynamics of three erbium-doped fiber lasers (EDFLs) that are diffusively coupled in a unidirectional ring configuration without the need for external pump modulation. Before the system shows stable high-energy pulses, different dynamic behaviors can be observed in the dynamics of the coupled lasers. The evolution of the studied system was analyzed using different techniques for different values of coupling strength. The system shows the well-known dynamic behavior towards chaos at weak coupling, starting with a fixed point at low coupling and passing through Hopf and torus bifurcations as the coupling strength increases. An interesting finding emerged at high coupling strengths, where phase locking occurs between the frequencies of the three lasers of the system. This phase-locking leads to a significant increase in the peak energy of the EDFL pulses, effectively converting the emission into short, high amplitude pulses. With this method, it is possible to significantly increase the peak energy of the laser compared to a continuous EDFL single pulse.

Primary silicon formation in hypereutectic alloy Al – 16.5% wt. Si treated in the liquid state by a changing unipolar pulsed electric current

Structure formation during the crystallization of a melt Al – 16.5% wt. Si treated with packages of unipolar electrical pulses of various frequencies and amplitudes have been studied. Grinding of primary silicon crystals was observed, the size and morphology of which depend on the electric current density. DTA showed a significant change in the parameters of both melting and solidification processes. X-ray diffraction studies have established the formation of additional silicon phases: polytype silicon, and silicon with tetragonal and bcc structures. The results obtained are explained by the transformation of the structure and a decrease in the degree of micro inhomogeneity of the Al-Si melt a change in the short-range order of Si-Si atoms.

Evaluation of DSRD-based pulsers for a Dielectric Wall Accelerator

Silicon (Si) drift step recovery diodes (DSRD) are opening switches that form the basis for nanosecond-scale high voltage (HV) pulsers. These pulsers are crucial to the operation of a dielectric wall accelerator (DWA), a compact particle accelerator design for proton beam radiation therapy. For the DWA to operate properly, the pulser must generate HV pulses with fast rise times and widths on the order of 1 ns at an operating frequency above 1 kHz. Several pulser designs are available that can optimally drive DSRDs. The purpose of this study is to investigate the capabilities of two DSRD-based pulsers in the context of the DWA and the required pulse parameters. The first pulser is based on a magnetic saturation transformer (MST) and a DRSD. The second pulser considered is a multi-module MOSFET-DSRD-based pulser. Additionally, Sentaurus TCAD simulations are used to study the influence of the Si DSRD doping profile on the output pulse shape. The MST-DSRD-based pulser is able to generate higher amplitude pulses than the MOSFET-DSRD-based pulser with a single module (9645 V and 1807 V, respectively). However, the multi-module MOSFET-DSRD-based pulser achieves the maximum pulse amplitude (10.9 kV) compared to MST-DSRD-based pulser (9645 V). The MOSFET-DSRD-based pulser also generates pulses with shorter pulse widths compared to the MST-DSRD-based pulser (minimum of 3 ns vs. minimum of 8.36 ns, respectively). With no compression stage, the MOSFET-DSRD-based pulser (with more than one module) generates pulses with consistently faster rise times (≤3.06 ns) compared to the MST-DSRD-based pulser (≤4.31 ns). With a compression stage, the rise times were comparable between the two pulsers (MOSFET-DSRD: 1.66 ns and MST-DSRD: 1.48 ns). Both pulsers are able to operate at 1 kHz and the MOSFET-DSRD-based pulser up to 10 kHz. Parasitic capacitance and coupling between modules of the MOSFET-DSRD-based pulser affect the pulse through their influence on the forward and reverse pumping duration. Simulations show that the p region of the DSRD should be larger than the n doped region. Simulations including a parasitic capacitance, modelling the electrical connections to the DSRD, reduce the pulse amplitude. Simulations of the pulsers incorporating SiC DSRDs show a reduction in the pulse amplitude and a widening of the pulse width in comparison to the Si DSRDs.

Development of a Semi-Autonomous Pulse and Receive Concrete Inspection System

Concrete structures are being subjected to increasing loads and used beyond their intended lifespan. When combined with operators shrinking maintenance budgets it is imperative structures are monitored for damage. Acoustic Emission (AE) and AE Tomography offer a method for damage detection and characterisation. However, they are encumbered by their equipment and setup requirements, and best used on areas where damage is already known to have occurred. An autonomous pulse catch system could be used to identify these areas. To explore the potential of such a system, seven concrete beams differentiated by their aggregate size were tested using an automated pulse and receive system. The effect of aggregate size, and pulse frequency on attenuation and wavespeed are investigated. The pulse regime consisted of narrowband pulses ranging from 30 kHz to 500 kHz. The results show that high frequency pulses experienced greater attenuation than low frequency pulses. Whilst a link appears between the size of the aggregate and the rate of attenuation of high frequency signals. A strong negative correlation between amplitude loss and pulse frequency was observed. For the specimen containing coarse aggregate, pulse velocity was constant between 100 kHz and 500 kHz, whereas specimens containing coarse aggregate experienced frequency dependant attenuation. This testing shows the significant potential for an automated pulse and receive system, which could lead to the development of an autonomous health monitoring system. In addition, the approach can be instrumental in developing large data sets, that can be used in Machine Learning processes, to develop a deeper understanding of AE signal propagation in concrete materials.

In situ characterization of qubit-drive phase distortions

Reducing errors in quantum gates is critical to the development of quantum computers. To do so, any distortions in the control signals should be identified; however, conventional tools are not always applicable when part of the system is under high vacuum, cryogenic, or microscopic. Here, we demonstrate a method to detect and compensate for amplitude-dependent phase changes, using the qubit itself as a probe. The technique is implemented using a microwave-driven trapped-ion qubit, where correcting phase distortions leads to a threefold improvement in the error of single-qubit gates implemented with pulses of different amplitudes, to attain state-of-the-art performance benchmarked at 1.6(4)×10−6 error per Clifford gate. Published by the American Physical Society 2024

Analysis of CFRP inter‐laminar cracking location under laser impacts

AbstractIn this study, a combination of theoretical analysis and experimental verification was used to investigate the effects of laser parameters and shock wave shape on the location of layer cracks in carbon fiber‐reinforced plastics specimens. Firstly, the propagation coupling process of trapezoidal, rectangular, and triangular pulses in the material was investigated based on the one‐dimensional stress wave propagation theory. The study analyzed the effects of shock wave pressure amplitude, pulse width, and other factors on the location of layer cracks in the material. Subsequently, laser impact experiments with varying energies and pulse widths were conducted on specimens of different thicknesses to investigate the impact of shock wave pressure amplitude and laser pulse width on the location of layer cracking. The results show that the theoretical analysis of triangular shock waves has broader applicability and can serve as a representative analytical model to describe single‐layer crack damage.Highlights Laser impact experiments with various specimen thicknesses. Laser pulse width determines the initial location of inter‐laminar cracking. The applicability of the triangular pulsed layer cracking formula. The effect of laser energy on pulse amplitude.

Association of Aortic Stiffness and Pressure Pulsatility With Noninvasive Estimates of Hepatic Steatosis and Fibrosis: The Framingham Heart Study.

Arterial stiffening may contribute to the pathogenesis of metabolic dysfunction-associated steatotic liver disease. We aimed to assess relations of vascular hemodynamic measures with measures of hepatic steatosis and fibrosis in the community. Our sample was drawn from the Framingham Offspring, New Offspring Spouse, Third Generation, Omni-1, and Omni-2 cohorts (N=3875; mean age, 56 years; 54% women). We used vibration-controlled transient elastography to assess controlled attenuation parameter and liver stiffness measurements as measures of liver steatosis and liver fibrosis, respectively. We assessed noninvasive vascular hemodynamics using arterial tonometry. We assessed cross-sectional relations of vascular hemodynamic measures with continuous and dichotomous measures of hepatic steatosis and fibrosis using multivariable linear and logistic regression. In multivariable models adjusting for cardiometabolic risk factors, higher carotid-femoral pulse wave velocity (estimated β per SD, 0.05 [95% CI, 0.01-0.09]; P=0.003), but not forward pressure wave amplitude and central pulse pressure, was associated with more liver steatosis (higher controlled attenuation parameter). Additionally, higher carotid-femoral pulse wave velocity (β=0.11 [95% CI, 0.07-0.15]; P<0.001), forward pressure wave amplitude (β=0.05 [95% CI, 0.01-0.09]; P=0.01), and central pulse pressure (β=0.05 [95% CI, 0.01-0.09]; P=0.01) were associated with more hepatic fibrosis (higher liver stiffness measurement). Associations were more prominent among men and among participants with obesity, diabetes, and metabolic syndrome (interaction P values, <0.001-0.04). Higher carotid-femoral pulse wave velocity, but not forward pressure wave amplitude and central pulse pressure, was associated with higher odds of hepatic steatosis (odds ratio, 1.16 [95% CI, 1.02-1.31]; P=0.02) and fibrosis (odds ratio, 1.40 [95% CI, 1.19-1.64]; P<0.001). Elevated aortic stiffness and pressure pulsatility may contribute to hepatic steatosis and fibrosis.

An Efficient Pulse Circuit Design for Magnetic Stimulation with Diversified Waveforms and Adjustable Parameters.

As a noninvasive neuromodulation technique, transcranial magnetic stimulation (TMS) has important applications both in the exploration of mental disorder causes and the treatment of mental disorders. During the stimulation, the TMS system generates the intracranial time-varying induced E-field (E-field), which alters the membrane potential of neurons and subsequently exerts neural regulatory effects. The temporal waveform of the induced E-fields is directly related to the stimulation effect. To meet the needs of scientific research on diversified stimulation waveforms and flexible adjustable stimulation parameters, a novel efficient pulse magnetic stimulation circuit (the EPMS circuit) design based on asymmetric cascaded multilevel technology is proposed in this paper. Based on the transient analysis of the discharge circuit, this circuit makes it possible to convert the physical quantity (the intracranial induced E-field) that needs to be measured after magnetic stimulation into easily analyzable electrical signals (the discharge voltage at both ends of the stimulation coil in the TMS circuit). This EPMS circuit can not only realize monophasic and biphasic cosine-shaped intracranial induced E-fields, which are widely used in the market, but also realize three types of new intracranial induced E-field stimulation waveform with optional amplitude and adjustable pulse width, including monophasic near-rectangular, biphasic near-rectangular and monophasic/biphasic ladder-shaped stimulation waveform, which breaks through the limitation of the stimulation waveform of traditional TMS systems. Among the new waveforms produced by the EPMS circuit, further research was conducted on the dynamic response characteristics of neurons under the stimulation of the biphasic four-level waveform (the BFL waveform) with controllable parameters. The relationship between TMS circuit parameters (discharge voltage level and duration) and corresponding neural response characteristics (neuron membrane potential change and neuronal polarizability ratio) was explained from a microscopic perspective. Accordingly, the biological physical quantities (neuronal membrane potential) that are difficult to measure can be transformed into easily analyzable electrical signals (the discharge voltage level and duration). Results showed that compared with monophasic and biphasic cosine induced E-fields with the same energy loss, the neuron polarization ratio is decreased by 54.5% and 87.5%, respectively, under the stimulation of BFL waveform, which could effectively enhance the neuromodulation effect and improve the stimulation selectivity.

Weak signal detection based on pulse width counting method for underwater wireless optical communication with an analog mode PMT detector.

This work proposes a weak signal detection method based on pulse width counting (PWC) for the on-off keying (OOK) underwater wireless optical communication (UWOC) system with an analog mode photomultiplier tube (PMT) detector. The signal output model of the analog mode PMT in weak light communication and the influence of pulse overlap are investigated. We experimentally evaluate the proposed algorithm under different sampling rates, detection thresholds, data rates as well as received optical powers (ROPs), and compare the performance of the proposed approach with that of pulse amplitude detection and pulse peak counting. A 10-Mbps OOK UWOC link is realized with a sensitivity of -71.5 dBm in a 7-meter tank, which is 1.1-dB and 3.8-dB lower than that of pulse peak counting (PPC) and pulse amplitude detection (PAD) methods, respectively, and the total link attenuation is 94.8 dB. This system utilizes the analog mode PMT with larger dynamic range than photon-counting mode PMT to achieve weak light signal detection, which benefits design long-range UWOC systems.

Deep brain stimulation pulse sequences to optimally modulate frequency-specific neural activity

Objective. Precise neuromodulation systems are needed to identify the role of neural oscillatory dynamics in brain function and to advance the development of brain stimulation therapies tailored to each patient’s signature of brain dysfunction. Low-frequency, local field potentials (LFPs) are of increasing interest for the development of these systems because they can reflect the synaptic inputs to a recorded neuronal population and can be chronically recorded in humans. In this computational study, we aim to identify stimulation pulse patterns needed to optimally maximize the suppression or amplification of frequency-specific neural activity. Approach. We derived DBS pulse patterns to minimize or maximize the 2-norm of frequency-specific neural oscillations using a generalized mathematical model of spontaneous and stimulation-evoked LFP activity, and a subject-specific model of neural dynamics in the pallidum of a Parkinson’s disease patient. We leveraged convex and mixed-integer optimization tools to identify these pulse patterns, and employed constraints on the pulse frequency and amplitude that are required to keep electrical stimulation within its safety envelope. Main results. Our analysis revealed that a combination of phase, amplitude, and frequency pulse modulation is needed to attain optimal suppression or amplification of the targeted oscillations. Phase modulation is sufficient to modulate oscillations with a constant amplitude envelope. To attain optimal modulation for oscillations with a time-varying envelope, a trade-off between frequency and amplitude pulse modulation is needed. The optimized pulse sequences were invariant to changes in the dynamics of stimulation-evoked neural activity, including changes in damping and natural frequency or complexity (i.e. generalized vs. patient-specific model). Significance. Our results provide insight into the structure of pulse patterns for future closed-loop brain stimulation strategies aimed at controlling neural activity precisely and in real-time.

A driving method for gray scale multiplication of electrowetting display based on hybrid modulation

In order to solve the problem of low gray level due to the few driving chips developed based on the photoelectric characteristics of electrowetting display, a driving method based on modulation is proposed to double the gray level of electrowetting display. In this method, the driving waveform based on pulse amplitude modulation and pulse width modulation hybrid modulation is designed, and the gray level–luminance curve of the electrowetting display is measured and analyzed. On this basis, the luminance nonlinear correction is carried out, and the improvement of 64 Gy levels to 127 Gy levels is realized by the principle of human visual persistence phenomenon. The experimental results show that the proposed driving scheme can break through the limitation of the driving chip and realize the multiplication of gray levels, in which 96% gray levels increase steadily with an average luminance difference of 0.07, and at the same time enhance the contrast and improve the display effect.

Large eddy simulation of pulsating film cooling on turbine vane

In this study, the large eddy simulation (LES) was employed to investigate the interaction mechanism between pulse jet and mainstream flow in turbine vanes, with a focus on assessing the impact of pulse frequency and amplitude on film cooling heat transfer. The results indicate that on the pressure surface, introducing pulsating coolant under high blowing ratio can effectively reduce the wall temperature, especially when using high amplitude pulse. Pulse excitation significantly affects the velocity distribution in the near-wall region of the pressure surface, while the velocity distribution on the suction surface shows less sensitivity to pulse excitation. Compared with the continuous condition, introducing pulsating coolant increases the turbulent kinetic energy (TKE). Higher pulsating amplitudes lead to a more pronounced enhancement of TKE, particularly on the pressure surface. Transient studies demonstrate the absence of starting vortices on both the pressure and suction surfaces during sinusoidal pulsation excitation. Although the evolution process of the turbulent structure of the two surfaces is completely different, the pulsating coolant under sinusoidal excitation can make the flow field have obvious periodicity. Analysis of the Power Spectral Density (PSD) reveals that coolant pulsation markedly affects the energy distribution of small-scale vortices.

Gradient-based surface nuclear magnetic resonance for groundwater investigation

In medical magnetic resonance imaging, spatial localization (imaging) is based upon the application of controlled magnetic field gradients on top of the main magnetic field to spatially modulate the frequency and/or phase of the nuclear magnetic resonance (NMR) signal across the volume of investigation. In this work, we have applied similar physical principles to produce controlled magnetic field gradients during surface NMR-based groundwater investigations. In this approach, a gradient pulse of variable amplitude or duration is applied immediately after the excitation pulse to cause predictable phase encoding of the NMR signal as a function of depth. This approach is also applicable to emerging surface NMR detection methods that use a prepolarization field with fast nonadiabatic turn-off to generate detectable NMR signals from the shallow subsurface. In this case, the gradient pulse is applied after terminating the prepolarization field and provides a heretofore unavailable means of localizing the NMR response as a function of depth. The application of gradients can also be combined with tip-angle-based modulation to yield higher imaging resolution than can be achieved through either gradient- or tip-angle-based imaging alone. We implemented this new gradient-based capability into a surface NMR gradient generation accessory that is compatible with the GMR-Flex instrument and developed surface NMR-specific forward modeling and linear inverse models. We validated the accuracy of this novel gradient-based sNMR technology using computer simulations, experiments using a small pool filled with a discrete layer of bulk water, and field experiments at well-characterized groundwater test sites along Ebey Island, WA, and Larned, KS. The gradient-based sNMR imaging observations were compared with high-resolution direct push NMR results observed at these sites. The results of computer simulations and field experiments indicate improvements in both the detection (signal-to-noise ratio) and spatial resolution of shallow subsurface water content using gradient-based surface NMR, compared with traditional surface NMR imaging methods.

Impact of the Higher-Order Reactive Nonlinearity on High-Amplitude Dissipative Solitons

In this work, the impact of the higher-order reactive nonlinearity on very high-amplitude solitons of the cubic–quintic complex Ginzburg–Landau equation is investigated. These high amplitude pulses were found in a previous work in the normal and anomalous dispersion regimes, starting from a singularity found by Akhmediev et al. We focus mainly in the normal dispersion regime, where the energy of such pulses is particularly high. In the presence of the higher-order reactive nonlinearity effect, pulse formation are observed for much higher absolute values of dispersion. Under such effect, the amplitude and the energy of the VHA pulses decrease, while their spectral range shrinks. Numerical computations are in good agreement with the predictions based on the method of moments, in the absence of the higher-order reactive nonlinearity effect. However, in the presence of this effect such agreement becomes mainly qualitative. A region of existence of the very high-amplitude pulses was found in the semi-plane defined by the normal dispersion and nonlinear gain.

Across-dimensional optical constellation de-aggregations from QAMs to PAMs in optical transparent networks

In this paper, an across-dimensional optical constellation de-aggregation scheme is proposed and verified. This de-aggregation scheme builds flexible optical connections between core and edge networks and fills the lack of the conversions between quadrature amplitude modulation (QAM) and pulse amplitude modulation (PAM) formats. 10G Baud quadrature phase shift keying/9QAM/16QAM-to-2×on off keying (OOK)/PAM3/PAM4 constellation de-aggregations are achieved. The enabled constellation manipulations contain polarization-assisted quadrature de-multiplexing and bi-directional vector moving. The key research status of QAM/PAM de-aggregations and adopted theoretical derivations are analyzed and expressed in detail. The signal spectrum, constellations, eye diagrams, transfer characteristics curves, error vector magnitudes and bit error ratios (BERs) during the de-aggregation process are calculated to measure the system performances. With the input optical signal-to-noise ratio (OSNR) of 10 dB/15 dB/20 dB, the de-aggregated OOK/PAM3/PAM4 signals show the receiver OSNR of 19.1 dB/21.9 dB/31.2 dB, respectively, at the BER of 10−3. The proposed scheme presents excellent format scalability and has potential applications in flexible all-optical connections, across-dimensional optical transmissions, and optical transparent networks.

Analysis of a Real-Time FSO System Utilizing Xia and SRRC Pulses in Multi-Band Carrier-Less Amplitude and Phase Modulation

Analysis of a Real-Time FSO System Utilizing Xia and SRRC Pulses in Multi-Band Carrier-Less Amplitude and Phase Modulation

Dissipative light bullets in a doped and weakly nonlocal optical fiber

The letter introduces an extended (3+1)-dimensional [(3+1)D] nonlocal cubic complex Ginzburg-Landau equation describing the dynamics of dissipative light bullets in optical fiber amplifiers under the interplay between dopants and a spatially nonlocal nonlinear response. The model equation includes the effects of fiber dispersion, linear gain, nonlinear loss, fiber nonlinearity, atomic detuning, linear and nonlinear diffractive transverse effects, and nonlocal nonlinear response. A system of coupled ordinary differential equations for the amplitude, temporal, and spatial pulse widths and position of the pulse maximum, unequal wavefront curvatures, chirp parameters, and phase shift is derived using the variational technique. A stability criterion is established, where a domain of dissipative parameters for stable steady-state solutions is found. Direct integration of the proposed nonlocal evolution equation is performed, which allows us to investigate the evolution of the Gaussian beam along a doped nonlocal optical fiber, showing stable self-organized dissipative spatiotemporal light bullets.