Sawtooth Waveform Research Articles

Photonic Generation of Arbitrary Microwave Waveforms with Anti-Dispersion Transmission Capability

We propose and demonstrate a photonic-assisted approach for generating arbitrary microwave waveforms based on a dual-polarization dual-parallel Mach–Zehnder modulator, offering significant advantages in terms of tunability of repetition rates and anti-dispersion capability. In order to generate diverse microwave waveforms, two sinusoidal radio frequency signals with distinct frequency relationships are applied to the dual-polarization dual-parallel Mach–Zehnder modulator. By adjusting the power of the applied sinusoidal radio frequency signal, the power ratio between these orthogonal polarized optical sidebands can be changed, and thereby desired radio frequency waveforms can be obtained after photoelectric conversion. In our proof-of-concept experiment, we systematically varied the repetition rate of triangular, rectangular and sawtooth waveforms. Meanwhile, we calculated the Root Mean Square Error (RMSE) to assess the approximation error in each waveform. The RMSEs are 0.1089, 0.2182 and 0.1185 for the triangular, rectangular and sawtooth microwave waveforms with repetition rate of 8 GHz, respectively. Furthermore, after passing through 25 km single mode fiber, the optical power decreased by approximately 5.6 dB, which verifies the anti-dispersion transmission capability of our signal generator.

Preparation and optical characterization of 3D-TiO2 thin films with brilliant colors

In this paper, three-dimensional titanium dioxide (3D-TiO2) thin films with periodic structure were obtained by periodic pulse anodization of high-purity titanium wafers under specific alternating voltage (AV) using asymmetric sawtooth waveforms. The effect of voltage amplitude and electrolyte concentration on the structural color of the 3D-TiO2 thin films were investigated. It is shown that the nanotubes grown by asymmetric sawtooth wave at a specific AV have a “bamboo” shape, and the cycle length, as well as the inner and outer tube diameters of the nanotubes are closely related to the AV. The structural color of the samples was different at varying voltages and electrolyte concentrations for the same oxidation cycle time. The structural color of films grown under low voltage is analyzed to be related to the scattering and absorption of light on their surfaces. The thickness of the film grown under high voltage satisfies the conditions for light interference. The maximum reflected wavelength is red-shifted and then blue-shifted as the electrolyte concentration decreases. The study shows that the microstructure is the main influence on the color change of 3D-TiO2 thin films.

Effect of induced electric field parameters on physiochemical characteristics and microorganism of orange juice

AbstractThe induced electric field (IEF) was produced via an oscillating magnetic field, for direct heating of orange juice within a winding coil. During the process, the applied magnetic field was at the range from 0.07 to 1.43 T with 50 kHz. Then, the numerical relationships between excitation voltage, magnetic field, IEF, induced current density, magnetomotive force and energy efficiency were investigated. Since a rectangular wave of excitation voltage was applied, the sawtooth waveform of induced voltage or IEF loaded on the juice was observed. As the magnetic field increased, outlet temperature and induced current density in the juice was improved, the maximum values were 99.5°C and 0.50 A/cm2, respectively, at a conductivity 4.53 mS/cm for the residence time of 4.5 min. However, the efficiency of the process exhibited a negative correlation with the escalation of excitation voltage. At initial colony count about 4.50 log colony‐forming units/mL, the IEF pasteurization reduced all the aerobic microorganisms, molds, and yeasts in the juice, which were evaluated at detectable limits below 1 log colony‐forming units/mL. Moreover, all treatments had no significant effects on pH, total soluble solids and titratable acidity of the juice (p > 0.05). In particular, there was also no significant change in color parameters after IEF pasteurization (p > 0.05). It indicated a significant decrease in vitamin C and total phenolic content of the control groups (p > 0.05), but no significant change in carotenoid content was observed in all treated juice (p > 0.05). heating technology using IEF has the potential to the pasteurization of fruit juice.Practical applicationsInduction electric field technology has progressed rapidly in the past 2 years, it can use oscillating alternating magnetic field to realize the direct heating of liquid food. The process has thermal and non‐thermal effects, at 65–70°C, within 15–30 s to achieve the commercial asepsis of acidic liquid food. After the pasteurization, it can better maintain the color and flavor of the juice. We have assembled a laboratory prototype for testing in the early stage, the processing capacity is at the range of 0–10 L/h. Currently, the system has been able to reach the pilot production scale with the processing capacity of 100–500 L/h. Through the use of highly permeable magnetic materials, the energy consumption per ton of juice processing is controlled at 120 k·Wh level for the pasteurization and is expected to achieve a larger processing capacity in the future.

Influence of Loading Waveform on the Fatigue Life of 34CrNi3MoVA Steel

Mechanical components often experience fatigue loading from various waveform conditions during their operational lifespan. However, the underlying mechanisms through which variations in loading waveform affect the fatigue life of components remain unclear. Thus, this study conducted tension–compression fatigue experiments on 34CrNi3MoVA steel specimens under the same stress amplitude with different waveforms (cosine, triangular, sawtooth, and reverse sawtooth) to investigate the effects of loading waveform variations on the cyclic strain hardening behaviors, the fatigue fracture failure, and the fatigue life. The results indicated that specimens under different waveforms all exhibited cyclic strain hardening. The fatigue cyclic hardening level progressively increased in the order of cosine, triangular, and sawtooth waveforms, resulting in a continuous increase in cyclic saturation strain amplitude. The analysis of fatigue fractures demonstrated a consistent increase in both the initiation and propagation zone areas in the order of cosine, triangular, and sawtooth waveforms, and the boundary between the propagation and final fracture zones gradually shifted from a straight to a curved shape. The influence mechanisms of cyclic loading waveforms on the fatigue life of specimens were analyzed based on the energy dissipation, leading to the development of a universal fatigue life prediction model applicable to different waveform conditions, the model was then verified with the reverse sawtooth wave specimens and resulted in a prediction error less than 15%. The study is expected to serve as a significant guide for predicting and evaluating the fatigue life of mechanical components under various fatigue loading conditions.

Memristive properties and synaptic plasticity in substituted pyridinium iodobismuthates.

This study explores the impact of organic cations in bismuth iodide complexes on their memristive behavior in metal-insulator-metal (MIM) type thin-layer devices. The presence of electron-donating and electron withdrawing functional groups (-CN, -CH3, -NH2, and -N(CH3)2) on pyridinium cations induces morphological alterations in crystals, thus influencing the electronic or ionic conductivity of devices comprising sandwiched thin layers (thickness = 200 nm ± 50) between glass/ITO as bottom electrode (∼110 nm) and copper (∼80 nm) as the top electrode. It was found that the current-voltage (I-V) scans of the devices reveal characteristic pinched hysteresis loops, a distinct signature of memristors. The working voltage windows are significantly influenced by both the types of cation and the dimensionality of ionic fragments (0D or 1D) in the solid-state form. Additionally, the temperature alters the surface area of the I-V loops by affecting resistive switching mechanisms, corresponding log-log plots at three temperatures (-30 °C, room temperature and 150 °C) are fully studied. Given that a memristor can operate as a single synapse without the need for programming, aligning with the requirements of neuromorphic computing, the study investigates long-term depression, potentiation, and spike-time-dependent plasticity-a specific form of the Hebbian learning rule-to mimic biologically synaptic plasticity. Different polar pulses, such as triangle, sawtooth, and square waveforms were employed to generate Hebbian learning rules. The research demonstrates how the shape of the applied pulse series, achieved by overlapping pre- and post-pulses at different time scales, in association with the composition and dimensionality of ionic fragments, lead to changes in the synaptic weight percentages of the devices.

Speed of Pitch Change in People with Parkinson’s Disease: A Pilot Study

Objective. To examine laryngeal maximum performance through a novel pitch diadochokinetic (DDK) task in people with Parkinson’s disease (PD) and healthy controls. Methods. This exploratory pilot study included a total of eight people with PD (seven male and one female) and eight healthy controls. Participants were instructed to rapidly transition or alternate between a chosen comfortable low and high pitch and were instructed to complete the task as a pitch glide. An Auditory Sawtooth Waveform Inspired Pitch Estimator-Prime model was used to first extract the pitch contour and then a customized MATLAB algorithm was used to compute and derive measures of pitch range and pitch slope. Results. Pitch range and slope were reduced in some participants with PD. Effects of age and disease duration were observed in people with PD: reductions in both pitch measures with increase in age and disease duration. Conclusions. A novel pitch DDK task may supplement the conventional laryngeal DDK task in the evaluation and treatment of motor speech and voice disorders. Individual variability analysis may provide specific diagnostic and therapeutic insights for people with PD.

Rod-Shaped Linear Inertial Type Piezoelectric Actuator

This article presents a numerical and experimental investigation of a novel rod-shaped linear piezoelectric actuator that consists of a square cross-section-shaped rod with eight piezo ceramic plates and a cylindrical guidance rail. The rod has a hollow cut made with an offset from the longitudinal axis of the symmetry. A cylindrical guidance rail is placed on one side of the rod, while T-shaped clamping is formed on the opposite side. The slider is mounted on the rail and is moved along it. The actuator is compact, making it possible to mount it directly on a printed circuit board (PCB) or in another device with limited mounting space, restricted mass, or actuator footprint. The operation of the actuator is based on the excitation of the first longitudinal vibration mode of the rod that induces in-plane bending vibration of the nodal zone of the rod due to a hollowed cut asymmetrically placed in the central part of the actuator. The actuator is driven by two sawtooth waveform electric signals with the phase difference of π that allows exciting longitudinal deformations of the rod and controls the reverse motion of the slider. The results of numerical investigations confirmed the operation principle of the actuator at the frequency of 59.72 kHz. The maximum displacement amplitude of the guidance rail in the longitudinal direction reaches up to 152.9 μm while the voltage of 200 Vp-p was applied. An experimental investigation of the actuator was made, and a maximum linear speed of 45.6 mm/s and thrust force of 115.4 mN was achieved.

Improving auditory-perceptual evaluation of disordered voice quality using a novel three-dimensional matching task

Current methods of auditory-perceptual evaluation of disordered voice quality using ordinal or interval scales have limited reliability and precision to quantify the magnitude of change in response to disorder progression or treatment. Matching tasks with synthetic comparison sounds have emerged as a more effective alternative, reducing biases and providing adjustable comparative values to represent perceived magnitude of change in quality. Previous studies have focused on the individual dimensions of breathiness, roughness, and strain separately and indicate covarying voice qualities may impact listener judgments. Here we investigate a three-dimensional matching (3-DMA) task where three variables, each representing a major quality dimension, can be adjusted concurrently. The comparison sound was a low-pass filtered sawtooth waveform (f o = 151 Hz) mixed with noise. Independent variables for matching were the signal-to-noise ratio for breathiness, amplitude modulation depth for roughness, and bandpass filter gain for strain. Listeners used sliders to adjust each variable, matching all three dimensions of 26 natural voice samples, selected to contain wide variation in all three dimensions. Preliminary results from five listeners demonstrated good reliability, similar to that observed in previous single-variable matching tasks for individual voice qualities. The results support the feasibility of the 3-DMA task. [Work supported by NIH R01DC009029.]

Spatial flux and energy asymmetry in a low pressure capacitively coupled plasma discharge excited by sawtooth waveform: A harmonic study

Plasma asymmetry generation in capacitively coupled plasma (CCP) discharges provides control over vital parameters that are useful in many plasma processing applications. In this article, using the particle-in-cell simulation technique, we investigated the spatial plasma asymmetry creation by a temporally asymmetric (sawtooth) waveform by varying its number of harmonics (N). The simulation results predict a non-linear increase in the plasma density and ion flux with an increase in N, i.e., it first decreases, reaching to a minimum value for a critical value of N and then increases almost linearly with a further rise in N. The ionization asymmetry increases with N, and higher harmonics on the instantaneous sheath position are observed for higher values of N. These higher harmonics generate multiple ionization beams that are generated near the expanding sheath edge and are responsible for an enhanced plasma density. The ion energy distribution function (IEDF) depicts a bi-modal shape for different values of N. DC self-bias is observed on the powered electrode, its magnitude with respect to the plasma potential decreases with increasing N, and therefore, the corresponding ion energy on the powered electrode decreases. The results conclude that by changing N of a sawtooth waveform in a collisionless CCP system, the ion flux asymmetry is not altered, whereas sheath symmetry could be significantly affected causing a systematic variation in the ion energy asymmetry. Due to an increase in the higher harmonic contents in the sawtooth waveform, a transition from broad bi-modal to narrow-shaped IEDFs is found.

Multi-target two-photon dual-comb LiDAR.

By substituting two-photon cross-correlation in a wide-bandgap photodiode for the coherent gating conventionally used in dual-comb ranging, two-photon dual-comb LiDAR exchanges data-intensive interferometric acquisition for a single time-stamp from which an absolute distance can be inferred. Here, we report the application of two-photon dual-comb LiDAR to obtain real-time ranging to three independent targets with only a single silicon-photodiode detector. We show precisions of 197-255 nm (2 seconds averaging time) for static targets, and real-time simultaneous ranging to three dynamic targets driven by independent sinusoidal, saw-tooth and square waveforms. Finally, we demonstrate multi-target ranging to three points on a rigid body to provide simultaneous pitch and yaw angular measurements with precisions of 27.1 arcsec (130 µrad) on a 25 mm baseline.

Research on Distributed Measurement and Control System Based on FlexRay Bus

With the purpose of the design problem of electromagnetic launch distributed measurement and control system, this paper proposes a design method of scalable large-scale distributed interconnected measurement and control system based on FlexRay bus. The task execution time deviation of each node in the distributed system, including phase deviation and frequency deviation, is reduced by using the macro tick generation process and clock synchronization process to achieve task synchronization in the distributed system. The synchronization of timing generation is realized based on the universal clock technology. When the timing interval is zero, the pulse power units are guaranteed to be close to the ideal full synchronization, thus ensuring that the released energy during transmission is close to the design value. In the state of adjustable timing, when the pulse power supply module conducts pulse discharge, the trigger discharge times of the modules are set according to the load needs. The flat top, sawtooth, and other characteristic current waveforms are adjusted accurately. At the same time, a combined multi-level protection structure based on hardware and software is realized. The verification results show that the distributed electromagnetic launch measurement and control system implemented in this paper can meet the high efficiency, fast and continuous launch target.

Individual Effect of Spatially Periodic Vertical Surface Temperatures and Nanoparticles on Natural Convection in Water

Abstract This paper considers the thermo-convective boundary-layer flow (BLF) of a water–copper mono-nanofluid over a flat vertical surface which is subjected to three types of periodic temperature variations described by the sinusoidal, sawtooth, and triangular waveforms. The temperature of the fluid at the flat surface is greater than the surrounding ambient temperature. The governing equations describing the BLF have been reduced to a non-similar form using an appropriate stream function formulation. The Keller-Box method is used to obtain numerical solution of the boundary-value problem. The effect of the pertinent parameters on the nature of the flow and the heat transfer has been discussed using actual thermophysical data. The results about the shear–stress and heat transfer rate at the surface are presented as well. To study the nature of BLF, the velocity and thermal boundary-layers, the streamline and isotherm plots have been considered, which reveal that the nanoparticle volume-fraction, amplitude of surface temperature variations, and the Grashof number play a pivotal role in enhancing/diminishing heat transfer. The final outcome reveals that the heat transfer is highest for the sinusoidal waveform, followed by that of the triangular and then, the sawtooth. An important inference is that a symmetric periodic temperature distribution at the surface enhances heat transfer more than that of a constant surface-temperature.

Thermo-Convective Flows of Mono- and Hybrid-Nanofluids Over Horizontal Undulated Surfaces in a Porous Medium

This paper presents a comparative study between the thermo-convective flows of two mono- and one hybrid-nanofluid over three uniformly heated undulated surfaces (described by sinusoidal, sawtooth or triangular waveforms) embedded in a porous medium. The base fluid for each nanofluid is water, and the nanoparticles are copper, alumina or a copper-alumina mixture. Two different types of materials of the porous medium have been considered: aluminum foam and glass balls. This problem is governed by a system of nonlinear, coupled partial differential equations, which is solved using the Keller-Box method. The influences of each porous medium and the pertinent parameters on the nanofluid flows and heat transfer have been explored. It is seen that secondary flow occurs at large amplitudes of the surface undulations for the sinusoidal and triangular waveforms, but no such flow is observed in the case of the sawtooth waveform and the flat surface. To assess the heat transfer properties, the mean Nusselt number has been calculated. It is observed that the mean Nusselt number is higher in the porous medium of glass balls than aluminum foam. The heat transfer on the undulated surfaces is the highest in the case of a hybrid-nanofluid and the least for water-alumina.

A Photonics Approach for Microwave Waveform Generation Based on PM-IM Conversions Using Two Dual-Output Sagnac Interferometers

A photonics-assisted scheme for generating various microwave waveforms has been investigated in this paper. In the proposed scheme, two phase modulation to intensity modulation (PM-IM) conversions are realized using two cascaded Sagnac interferometers (SIs) to manipulate light in the optical domain. From the first SI, by adjusting the amplitude of the microwave signal and time delay of the tunable optical delay line (TODL), both half duty cycle square and full duty cycle triangular waveforms can be generated from the photodetector (PD) and balanced photodetection (BPD). Using the second SI and applying microwave signals with appropriate amplitudes and phases, as well as the BPD process, results in full duty cycle sawtooth and reversed sawtooth waveforms. Detailed theoretical analyses are presented and results are verified by simulations. In the simulations, square-, triangular- and sawtooth-shaped (or reversed sawtooth-shaped) waveforms are obtained successfully. To complete the simulation results, the effects of non-ideal microwave hybrid coupler and optical couplers on the performances of the proposed scheme have been studied and no destructive effects were observed. The proposed structure does not include any optical or electrical filters which result in a wide operational bandwidth.

Development and Validation of a Single-Variable Comparison Stimulus for Matching Strained Voice Quality Using a Psychoacoustic Framework.

Acoustic and perceptual quantification of vocal strain has been a vexing problem for years. To increase measurement rigor, a suitable single-variable matching stimulus for strain was developed and validated, based on the matching stimulus used previously for breathy and rough voice qualities. A set of 21 comparison stimuli for a single-variable matching task (SVMT) was synthesized based on a speech-shaped sawtooth waveform mixed with speech-shaped noise. Variable bandpass filter gain in mid-to-high frequencies achieved a wide range of computed sharpness (in constant sharpness steps) and served as the independent variable for the SVMT. Ten natural /ɑ/ stimuli with a wide range of the primary voice quality of strain and a minimum of breathiness or roughness were selected and assessed using the SVMT. Natural voice samples and synthetic comparison stimuli were also assessed using a perceptual magnitude estimation (ME) task. ME data validated the correspondence of the set of comparison stimuli to varying perceived strain. Perceived strain magnitudes of the comparison stimuli increased significantly and linearly with computed sharpness (r 2 = .99). A linear regression revealed that strain matching values were significantly predicted by computed sharpness (r 2 = .96) and perceived strain magnitudes (r 2 = .95) of the natural voice stimuli. The perception of vocal strain is strongly associated with computed sharpness and is captured accurately and precisely using an SVMT, in which the independent variable is the bandpass filter gain (in steps of equal sharpness) applied to the comparison stimuli.

Effect of the high voltage waveform on the ionic wind produced by a needle-to-plate dielectric barrier discharge

Although corona discharges are used in many industrial applications because of their ability to produce chemical species, the ionic wind they induce is less known and often ignored. Therefore, the present study aims at investigating the ionic wind produced by a corona discharge ignited between a high voltage needle and a grounded plate electrode covered by a dielectric material. More specifically, the work focuses on the influence of the high voltage waveform on the temporal behavior of the ionic wind. The results highlight that the high voltage waveform plays a key role on the dynamics of the flow produced inside the discharge. On the one hand, for the sine, triangle and sawtooth waveforms, there is a flow acceleration during both the positive and the negative half-cycles, the positive discharge being more effective in velocity production. On the other hand, for the square waveform, the increase in velocity occurs during the rises and falls of the voltage, because of the strengthening of the electric field due to the ions remaining from the previous half-cycle at the wall of the dielectric material.

94 GHz 수신 4채널, 송신 1채널 FMCW 레이다 시스템

This paper describes a 94 GHz FMCW radar system for unmanned vehicles using 94 GHz 1 Tx and 4 RX chips designed in a 65-nm CMOS process. The measured output power of the transmitter and the conversion gain of the receiver were 9.77 dBm and 26 dB, respectively. The simulated noise figure of the receiver chip was 8 dB. The Tx and Rx antennas were microstrip patch antennas with a gain of 11 dBi on a Duroid substrate. The chirp period of the sawtooth FMCW waveform was 50 μs. The baseband signal was bandpass-filtered with a passband gain of 26 dB and sampled at a rate of 50 MSPS with a 14-bit ADC. The output of the ADC was acquired using an FPGA. The distance and angle information of the target were calculated using the FFT-based algorithm. The processed results closely matched the calculated results based on the specifications of TRx chips and processing gain, which confirmed the validity of the developed radar system.

Flexible Microwave Waveforms Synthesis Based on Wavelength Sensitive Bias Shift of a Mach–Zehnder Modulator

A new scheme of arbitrary microwave waveform generation based on one single-drive Mach–Zehnder modulator (MZM) is proposed. Due to the characteristic of the wavelength-dependent bias shift in a MZM, two light fields with different wavelength can carry two sets of modulation components and contribute the desired waveforms through both of the Fourier synthesis and time-domain synthesis. Thanks to plentiful and controllable harmonics generation, some challenging waveforms generation, such as parabolic waveform, sawtooth waveform and frequency doubling triangular waveform, can be achieved, which are verified by the theoretical analysis and experimental results. This method exhibits not only more flexible waveform generation ability, but also the advantages of simple configuration, easy operation and high efficiency of bandwidth utilization.

Trigonometric Cosine, Square, Sawtooth and Triangular Waveforms of Internal Heating Modulations for Three-Component Convection in a Couple Stress Liquid: A Detailed Analysis

Trigonometric Cosine, Square, Sawtooth and Triangular Waveforms of Internal Heating Modulations for Three-Component Convection in a Couple Stress Liquid: A Detailed Analysis

Improvement of a capacitive UV-sensor by porous silicon powders embedded in epoxy on porous silicon film

A high-sensitivity porous silicon (PS) powder-based capacitive UV-sensor is developed on the PS-film structure. To the best of our knowledge, this is the first report on PS powder-based capacitive UV-sensors. An anodization etching approach based on a sawtooth waveform electrolytic voltage is adopted to get sufficient PS-powders. The collected PS-powders are embedded on the PS-film and covered with epoxy to improve the UV sensitivity. The results show that the increase of UV sensitivity on capacitive characteristics is almost linearly related to the PS powder mass embedded inside. The proposed method is suitable for fine-tuning and improving the equivalent permittivity of the capacitive UV-sensor without changing the device geometry design, which can be compatibly applied to Si-VLSI technology.