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Our main interest in this study is to obtain approximate time-dependent solutions of the Lotka–Volterra predator–prey model given the populations of both species at a certain time. We achieve this by considering an earlier scheme by Shinohara and Yamamoto and modifying it so as to address the initial conditions. An important feature of this scheme is that it treats the system’s period as an unknown variable, making it possible to calculate it as a side product. In this method, the Galerkin procedure is utilized to convert the problem to a system of nonlinear algebraic equations, where sine and cosine waves are chosen as the basis functions in order to ensure the periodicity of solutions. The resulting overdetermined system is then solved in a least squares sense, which yields the coefficients making up the Galerkin approximations. After a detailed presentation of the numerical scheme, we apply it to two example problems and evaluate the results according to several accuracy criteria. [ABSTRACT FROM AUTHOR]

This paper describes a mathematical model of the AC/DC converter. The analytic expressions define fundamental physical variables of the converter and their relations: phase current and voltage, shift angle between these quantities, power factor, and supply voltage UD. The mains voltage is defined as a digitalized sine wave while the current's wave takes the form of a line segment defined in an appropriate time interval. The model permits the description of two modes of operation: inverter and rectifier. The assumed control method of the converter depends on the successive switching of selected vectors. They are qualified according to the principle of the lowest error between the reference and measured phase current value. The control method is realized by using hysteresis algorithms. Five different algorithm solutions and comparative results are implemented. Several examples of current, voltage, and vectors taken during the simulation and experimental works are executed. [ABSTRACT FROM AUTHOR]

This paper presents datasets and analyses of 3D LiDAR scans capturing the rutting behavior of a rover wheel in a single-wheel terramechanics testbed. The data were acquired using a LiDAR sensor to record the terrain deformation caused by the wheel's passage through a Toyoura sandbed, which mimics lunar regolith. Vertical loads of 25 N, 40 N, and 65 N were applied to study how rutting patterns change, focusing on rut amplitude, height, and inclination. This study emphasizes the extraction and processing of terrain profiles from noisy point cloud data, using methods like curve fitting and moving averages to capture the ruts' geometric characteristics. A sine wave model, adjusted for translation, scaling, and inclination, was fitted to describe the wheel-induced wave-like patterns. It was found that the mean height of the terrain increases after the grouser wheel passes over it, forming ruts that slope downward, likely due to the transition from static to dynamic sinkage. Both the rut depth at the end of the wheel's path and the incline increased with larger loads. These findings contribute to understanding wheel–terrain interactions and provide a reference for validating and calibrating models and simulations. The dataset from this study is made available to the scientific community. [ABSTRACT FROM AUTHOR]

The development of hydrochemical passports for rivers represents a key step toward better understanding and managing water resources in Ukraine. The objective of this research is to assess the state of surface waters and forecast changes in the water area of the city of Mykolaiv. This is achieved by determining sampling points within the water area of the Buzky Estuary, the Southern Buh and Inhul rivers, and within the districts of Mykolaiv. The analysis includes examining integrated hydrochemical indicators and investigating the temporal and spatial changes in water quality. The research focuses on the regularities of changes in water quality over time and space and includes surface waters of the Buzky Estuary, the Southern Buh River, and the Inhul River within Mykolaiv. Photometric method for determining water quality indicators using the eXact Strip Micro 20 long-wave photometric system. Mathematical methods include statistical data processing, the method of average values in determining the level of surface water pollution, and graphical reflection of data for qualitative visual evaluation of results using MS Excel software. The level of mineralization varies between different observation points, but the general trends remain similar. The data indicate a significant excess of the maximum permissible concentration at all observation points, which is a serious reason not to use these waters as a source of technical and even more so drinking water supply. Alkalinity significantly exceeds the maximum permissible concentration in all months considered, which indicates a consistently high level of this indicator in water. There is an increase in alkalinity from December to March, after which there is a sharp drop in April, and in May it rises again. The regression analysis found that annual hydrochemical indicators dynamics correspond to the sine wave of long-term fluctuations. The resulting function has made it possible to predict fluctuations over 6 years of a sine wave. [ABSTRACT FROM AUTHOR]

Numerous digital communication systems, such as digital radio and modems, digital converters, computer base stations, etc., depend on numerically controlled oscillators (NCOs). NCOs are so often utilized because of the wide range of beneficial characteristics that possess. Direct digital frequency synthesizers (DDFSs) are essential elements of modern radio electronics. These signals can be generated using either analogue circuitry or digital circuitry. These signals are generated by an NCO in a digital system, and they are then converted to analogue signals by a digital-to-analog converter (DAC). This paper presents a direct digital synthesizer (DDS) of Gilbert cell using a chisel generator with NCOs. The DDS has a sine-wave generator analogue Gilbert cell, a phase accumulator, wave-correction ROM (WCR), RAM, and DACs. Two ground-signal-ground (GSG) single-ended microwave probes and two DC probes are used to test the DDS on the wafer. The results of the test demonstrate that it can create sine waves with a frequency resolution of 23.44MHz and can operate consistently at 6GHz clock frequency. [ABSTRACT FROM AUTHOR]

In this paper, the electrochemical and corrosion behavior of pure titanium (TA1) in simulated Proton Exchange Membrane Water Electrolysis (PEMWE) anodic environment was investigated. In this condition, the corrosion potential of TA1 was −689 mV, with a self-corrosion current density of 232.5 μA cm–2, and a polarization resistance of 125.9 Ω cm2. During potentiostatic polarization at 2 V, the current density was maintained at approximately 6 mA cm–2. However, the passivation process exhibited instability. Furthermore, this process has been shown to significantly facilitate the formation of surface oxides, and the passive film that formed displays the lowest bound water and OH−, and the highest content of O2–, exhibiting the highest average valence. Notably, dynamic potentials caused current transients, among which square wave potential was the most remarkable. The square wave potential shows an O2– content just below that of 2V potential polarization when fluctuating potentials are applied. The interfacial contact resistance (ICR) of 2 V potentiostatic polarization was slightly higher than that of square, sine and triangular waves. Additionally, the high temperature condition of PEMWE will aggravate the corrosion of TA1 by fluoride ions. [ABSTRACT FROM AUTHOR]

In this paper, we derive a new exponential wave integrator sine pseudo-spectral (EWI-SP) method for the higher-order Boussinesq equation involving the higher-order effects of dispersion. The method is fully-explicit and it has fourth order accuracy in time and spectral accuracy in space. We rigorously carry out error analysis and establish error bounds in the Sobolev spaces. The performance of the EWI-SP method is illustrated by examining the long-time evolution of the single solitary wave, single wave splitting, and head-on collision of solitary waves. Numerical experiments confirm the theoretical results. [ABSTRACT FROM AUTHOR]

A type of hollow concrete-filled circular steel tube connected by thread through inside lining tube is proposed. Twelve hollow concrete-filled circular steel tubular beam columns connected by thread through inside lining tube are designed and fabricated using the length of the thread along the axial direction, the working height of the thread, and the position of the thread as parameters. In addition, one nonconnected specimen and two welded specimens also are designed and fabricated to conduct controlled experimental research. The experimental phenomena and specimen failure modes, axial compressive load-longitudinal compression curve, axial compressive load-lateral deflection curve at the mid-section, and axial compressive load-strain in the steel tube curve, as well as the bearing capacity, strength reserve, deflection curve shape, lateral stiffness, ductility, and plane section assumptions, are analyzed. The research results indicate that, within the parameter range studied, the experimental phenomenon of specimens connected by thread is basically consistent with that of contrast specimens and the thread connection through inside lining tube is reliable before tripping. The axial compressive load-longitudinal compression curve and axial compressive load–mid-section lateral deflection curve of all specimens can be approximately divided into elastic stage, elasto-plastic stage, and descending stage. The peak load of all specimens is relatively close, and although specimens have undergone almost the same stress process, the strength reserve of specimens connected by thread is insufficient. The shape of the deflection curve of all specimens is close to the sine half wave curve before the load drops to about 70% peak load, and the lateral stiffness and ductility of all specimens also are relatively close. During the entire loading process, the distribution of longitudinal strain in the steel tube at the mid-section along the height of section basically conforms to the plane section assumption. Finally, the calculation method for the hollow concrete-filled circular steel tubular beam column connected by thread through inside lining tube is suggested. Based on the behavior of the hollow concrete-filled circular steel tubular beam column and considering the comprehensive cost, the hollow concrete-filled circular steel tube connected by thread through the inside lining tube has certain research and application value. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a direct amplitude (AM) demodulator using artificial neural network (ANN) on field programmable gate array (FPGA), which enables direct demodulation of modulated carriers to baseband waveforms. This direct AM demodulator introduces a novel approach by eliminating the need for intermediate frequency (IF) conversion, leveraging a neural network instead of a traditional analog local oscillator and mixer. Eliminating the IF stage allows for the use of wider bandwidth, supporting modern wideband communication systems. By omitting these conventional components, the proposed ANN-based direct AM demodulator reduces system noise, thereby enhancing fidelity. The proposed ANN-based direct AM demodulator uses a pre-processing technique to generate the carrier signal digitally at the input of the ANN enabling effective handling of high-frequency modulated signals. The implementation of the proposed ANN-based direct AM demodulator targets the XC7VX690T Virtex-7 FPGA platform, validated using Xilinx Vivado simulations. The ANN's adaptability across different carrier frequencies enhances hardware reusability and resource efficiency. The ANN-based direct AM demodulator implemented on FPGA is faster than the ANN implemented using the C++ based fast artificial neural network (FANN) library which reduces the overall processing time and allows the operation of higher carrier frequencies. Results demonstrate the demodulator's capability to process sine and square waves across a wide frequency range: modulating frequencies from 2.5 MHz to 20 MHz and carrier frequencies from 50 MHz to 200 MHz supporting a maximum bandwidth of 40 MHz. The proposed demodulator operates efficiently at a maximum carrier frequency of 200 MHz, with a sampling frequency of 1.66 GHz. Experimental results confirm the ANN's robust performance across varying signal-to-noise ratios (SNRs) from 10 dB to 100 dB, showcasing MSE values ranging from 0.06 to 0.000001. Further to add, no noise filter is required after an SNR of 30 dB. The design is achieving only 16% amplitude distortion, thus offering an acceptable fidelity. The proposed demodulator consumed only 63.25% of LUT slices for a single hidden layer and 82.36% of LUT slices for two hidden layers ANN implementations on the specified FPGA board. DSP48E1 units used are 37.71% for the single layer and 60.21% for the multi-layer. The processing speed of the ANN based direct AM demodulator implemented on FPGA is 60.125, and 44.65 at f c of 50 MHz, and 200 MHz respectively. Overall, this ANN-FPGA based approach represents a significant advancement in AM demodulation technology, offering enhanced adaptability and performance compared to traditional methods. [ABSTRACT FROM AUTHOR]

In this paper, a fast and efficient control method is proposed for a pure sine wave inverter used in an electric vehicle system, which can provide better performance under transient and steady-state conditions. The proposed control technique consists of a fast terminal attractor (FTA) and a fractional multivariable grey model (FMGM). The FTA with finite time convergence offers a faster convergence rate of the system state and a singularity-free solution. However, if the uncertain system boundaries are overestimated or underestimated, chatter/steady-state errors can occur during the FTA, which can lead to significant harmonic distortion at the output of the pure sine wave inverter. A computationally efficient FMGM is incorporated into the FTA to solve the chatter/steady-state error problem when an uncertain estimate of the system boundary cannot be satisfied. Simulation results show that the proposed control technique exhibits low total harmonic distortion. Experimental results of a prototype pure sine wave inverter are presented to support the results of the simulation and mathematical analysis. Since the proposed pure sine wave inverter outperforms the classical TA (terminal attractor)-controlled pure sine wave inverter in terms of convergence speed, computational efficiency, and harmonic distortion elimination, this paper will serve as a useful reference for electric vehicle systems. [ABSTRACT FROM AUTHOR]

This paper constructs a numerical simulation model for the deformation of droplets in a variable cross-section groove of a liquid droplet MEMS switch under different directions, amplitudes, frequencies, and waveforms of acceleration. The numerical simulation utilizes the level set method to monitor the deformation surface boundary of the metal droplets. The simulation outcomes manifest that when the negative impact acceleration on the X-axis is 12.9 m/s2, the negative impact acceleration on the Y-axis is 90 m/s2, the negative impact acceleration on the Z-axis is 34.5 m/s2, and the metal droplet interfaces with the metal electrode. The droplet deformation under the effect of a sine wave acceleration signal in the X and Y directions is lower than that under impact acceleration, while in the Z direction, the deformation is higher than that under impact acceleration. The deformation of metal droplets under square wave acceleration is more pronounced than that under sinusoidal wave acceleration. The deformation escalates with the augmentation in square wave amplitude and dwindles with the reduction in square wave acceleration frequency. Furthermore, there exists a phase difference between the deformation curve of the metal droplet and the continuous acceleration signal curve, and the phase difference is dependent of the material properties of the metal droplet. This work elucidates the deformation of the liquid-metal droplets under continuous acceleration and furnishes the foundation for the continuous operation design of MEMS droplet switches. [ABSTRACT FROM AUTHOR]

The rapidly increasing demand for heavy vehicles in the transportation sector has led to more severe road damage and significantly higher road maintenance costs. Investigation of active suspension system incorporating vehicle–road interaction (VRI) can provide effective means to reduce the road damage and improve the ride comfort of vehicles. In this paper, an active vehicle suspension controller based on the strongly stable and robust linear–quadratic regulator (LQR) principle is developed for the time-varying VRI system. The coupled system is modeled by a quarter-car traveling on the road modeled by an Euler–Bernoulli beam resting on a viscoelastic foundation. Two types of road irregularities, deterministic sine wave and random, are considered in the numerical studies. A time-frozen technique, by which the linear time-varying system is converted to a time sequence of time-invariant systems, is applied to solve for the coupled responses. Three variables, the dynamic tire load, vehicle body acceleration, and suspension relative displacement, are used to assess the effectiveness of the LQR-based controller in comparison to the passive suspension system. The performance of the active control is investigated for different vehicle speeds, vehicle loads, and road profiles. Numerical studies show that the controller can effectively reduce the road damage and improve the ride comfort, with a slight increase in the suspension relative displacement. This work lays a useful foundation in the problem formulation and system parameter influences for future vehicle suspension design and road damage mitigation including VRI. [ABSTRACT FROM AUTHOR]

As the current guidelines on myocardial revascularization recommend, transit-time flow measurement (TTFM) is increasingly used for intraoperative graft flow analysis during coronary artery bypass grafting (CABG) as a less invasive, more highly reproducible, and less time-consuming method. In addition to the morphological assessment using color Doppler, mean graft flow (Qm) > 15 ml/min, pulsatility index (PI) < 5.0, diastolic filling (DF) > 50%, and systolic reverse flow (SRF) < 4% have been reported to predict patent CABG grafts. However, it is difficult to determine the clear-cut cut-off value of these parameters, because they varies with the hemodynamic characters, including fractional flow reserve (FFR) of the target coronary artery. In addition to these parameters, we focused on fast Fourier transform (FFT) analysis, because the TTFM waveform morphology may be more important than Qm itself. FFT analysis is based on the principle that any periodic waveforms can be broken down into a series of pure sine waves or harmonics. Herein we review FFT analysis of the intraoperative TTFM waveforms for quality assessment of CABG grafts. [ABSTRACT FROM AUTHOR]

In order to improve the measurement accuracy of near-bit apparent resistivity and its measurement range, this paper excites the underground transmitting antenna by a sinusoidal pulse-width modulated (SPWM) current excitation method, which can improve the response of the receiving antenna and circuit in the resistivity measurement system under the usual square wave excitation, thus improving the measurement accuracy of near-bit apparent resistivity. In this paper, the effect of square wave, SPWM wave and sine wave excitation on resistivity measurement was studied, and the modulation algorithm and hardware control are programmed by DSP (Digital Signal Processor), and the SPWM signal is output by full-bridge inverter circuit and tuned antenna. The indoor experimental results show that the near-bit apparent resistivity measurement method based on the SPWM wave pulse excitation can achieve the measurement in the range of formation equivalent resistor value of less than 600kΩ. There is a high trend matching between near-bit apparent resistivity LWD curve and RT resistivity curve of well completion electrical logging in field tests of formation resistivity less than 2000Ω·m, which proves that the method can improve the accuracy of near-bit apparent resistivity measurement. [ABSTRACT FROM AUTHOR]

The potential for throttle control of hybrid rocket systems has long been known as a potential advantage for a variety of applications. Because only a single flow path is controlled, theoretically, hybrids should be significantly easier to throttle than bipropellant systems. Unfortunately, the slow response times and nonlinearity of traditional position-control valves have limited practical applications of hybrid throttling. This paper presents an alternative throttling system where the oxidizer flow path is broken into multiple streams, with each flow path controlled by a solenoid-operated on/off valve. The parallel paths allow significantly faster and more precise control than can be achieved using a single position-control valve. The achievable thrust levels are limited only by the size and number of components in the valve cascade. The 8-bit digital throttle system, developed by Utah State University's Propulsion Research Lab, uses commercial, off-the-shelf components. The throttle system was tested using a 200-N hybrid rocket motor, burning gaseous oxygen, and ABS plastic as propellants. The testing campaign of more than 50 hot fires has demonstrated multiple profiles, including deep throttle ramps, multistep boxcars, and sine waves at frequencies varying from 0.25 to 1-Hz. Comparisons to analytical models are also presented, showing good agreement. Fourier-transform spectra demonstrating the total-system, frequency response are also presented. [ABSTRACT FROM AUTHOR]

The output performance of piezoelectric pumps is not only affected by the structural design but is also related to the drive signal. To study the effect of different drive signals on the output performance of piezoelectric pumps, this paper takes dual-chamber serial piezoelectric pumps as the investigation object, theoretically deduces the effective value of the drive signal and the output performance of the piezoelectric pump, and tests the displacement of piezoelectric vibrator center, the output performance of the piezoelectric pump, and the operating noise within the range of 0–500 Hz, respectively, driven by square waves, sine waves, and triangular waves (the peak-to-peak values of which are all 300 V). The results show that at low frequencies, the piezoelectric vibrator's center displacement curve matches the drive signal, which is sinusoidal and decreases with frequency. Under the square drive, the piezoelectric pump has the best performance, with a flow of 147.199 mL/min and pressure of 14.42 kPa, but the noise is also the highest. The output performance of the sine wave is better than that of the triangular wave, and the flow rate of the three signals shows a trend of first increasing and then decreasing. [ABSTRACT FROM AUTHOR]

The actuator is a critical component of the micromanipulator. By utilizing the properties of expansion and contraction, the piezoelectric actuator enables the manipulator to handle and grasp miniature objects during micromanipulation. However, in piezoelectric ceramic disc actuators with conventional surface electrode configurations, the actuating force generated in the radial direction is relatively limited. When used as the actuation element of the manipulator, achieving regulation over a wide range of operating strokes becomes challenging. Therefore, altering the electrode structure is necessary to generate a greater radial force, thus enhancing the positioning and grasping capabilities of the operating arm. This paper investigates a piezoelectric actuator with interdigitated spiral electrodes, featuring a constant pitch between adjacent electrodes. The radial force was tested under mechanical clamping conditions, and the influence of the electrical signal was examined. The characteristics of the electrode structure were described, and the working principles of the piezoelectric actuators were analyzed. Theoretical equations were derived for the macroscopic characterization of the radial clamping force of the actuator, based on the piezoelectric constitutive equation, geometric principles, and Bond matrix transformation relationships. A finite element model was developed, reflecting the features of the electrode structure, and finite element simulations were employed to verify the theoretical equations for radial force. To prepare the samples, encircled interdigitated spiral electrode lines were printed on the PZT-52 piezoelectric ceramic disc using a screen printing method. The clamping force experimental platform was established, and experiments on the clamping radial force were conducted with electrical signals of varying waveforms, frequencies, and voltages. The experimental results show that the piezoelectric ceramic disc actuator with an interdigitated spiral electrode line structure, when excited by a stable sine wave operating at 200 V and 0.2 Hz, generated a peak force of 0.37 N. It was 1.76 times greater than that produced by a previously utilized piezoelectric disc with conventional electrode structures. [ABSTRACT FROM AUTHOR]

Most implicit sentiment sentences in aspect level implicit sentiment analysis lack emotional words, but there are still potential emotional clues. Current research mainly utilizes contextual information and external knowledge of text for semantic enhancement, thereby improving implicit sentiment analysis. However, in these models, the semantic correlation between words decays as the distance between the two increases, leading to weak and difficult to capture emotional cues at long distances, presenting ambiguity in emotional polarity and reducing the performance of sentiment analysis. To solve this problem, in this paper, we propose aspect-level implicit sentiment analysis model based on semantic wave and knowledge enhancement. Firstly, the semantic wave-based aspect word context information enhancement method uses the fluctuation property of semantic wave to perform weight adaptive enhancement of semantically related long-distance context information. This method essentially utilizes a sine wave function to significantly reduce the weight of words that are close but semantically unrelated, thereby allowing the weight of words that are close and semantically similar to be relatively reflected, in order to solve the problem of hiding emotional clues at long distances. Then, the implicit sentiment analysis method based on supervised contrastive pre-training is used to capture potential sentiment cues from context information and embed them into the sentence vector by weak feature learning of implicit sentiment. Finally, multi-feature interaction-based knowledge enhancement method is used to focus on the context content of sentences that are more related to background knowledge in a feature interaction way, and the information scaling factor is combined to enhance the dependency between aspect words and sentiment cues, thereby solving the problem of weak features in long-distance emotional clues and accurately identifying the emotional polarity of aspect words. The experiment shows that the model proposed in this paper has made significant improvements on the Restaurant and Laptop datasets in SemEval 2014 Task 4, with an accuracy increase of 3.38% and 4.57% in implicit emotions, respectively, achieving the best performance so far. At the same time, generalization and robustness testing experiments were conducted on the model, achieving preferable performance improvement. [ABSTRACT FROM AUTHOR]

Using gallium nitride (GaN) transistors in motor drive systems presents challenges because of their high dv/dt characteristics. Compared with silicon (Si) transistors, GaN transistors cause a higher leakage current in the bearing. This phenomenon results in a bearing corrosion problem in the motor, consequently shortening its lifespan. In response to these challenges, an output filter placed between an inverter and the motor has been studied recently. This paper compares the leakage current in a permanent magnet synchronous motor (PMSM) drive system driven by a GaN inverter without and with a sine wave filter. By modeling the impedance of the leakage current path, this paper confirms the possibility of reducing leakage current with the application of the sine wave filter. Experimental results show that using the sine wave filter reduces the leakage current by 32.24% at full load. [ABSTRACT FROM AUTHOR]

OBJECTIVES: Hyperkalemia is a common life-threatening condition causing severe electrophysiologic derangements and arrhythmias. The beneficial effects of calcium (Ca2+) treatment for hyperkalemia have been attributed to "membrane stabilization," by restoration of resting membrane potential (RMP). However, the underlying mechanisms remain poorly understood. Our objective was to investigate the mechanisms underlying adverse electrophysiologic effects of hyperkalemia and the therapeutic effects of Ca2+ treatment. DESIGN: Controlled experimental trial. SETTING: Laboratory investigation. SUBJECTS: Canine myocytes and tissue preparations. INTERVENTIONS AND MEASUREMENTS: Optical action potentials and volume averaged electrocardiograms were recorded from the transmural wall of ventricular wedge preparations (n = 7) at baseline (4 mM potassium), hyperkalemia (8-12 mM), and hyperkalemia + Ca2+ (3.6 mM). Isolated myocytes were studied during hyperkalemia (8 mM) and after Ca2+ treatment (6 mM) to determine cellular RMP. MAIN RESULTS: Hyperkalemia markedly slowed conduction velocity (CV, by 67% +/- 7%; p < 0.001) and homogeneously shortened action potential duration (APD, by 20% +/- 10%; p < 0.002). In all preparations, this resulted in QRS widening and the "sine wave" pattern observed in severe hyperkalemia. Ca2+ treatment restored CV (increase by 44% +/- 18%; p < 0.02), resulting in narrowing of the QRS and normalization of the electrocardiogram, but did not restore APD. RMP was significantly elevated by hyperkalemia; however, it was not restored with Ca2+ treatment suggesting a mechanism unrelated to "membrane stabilization." In addition, the effect of Ca2+ was attenuated during L-type Ca2+ channel blockade, suggesting a mechanism related to Ca2+-dependent (rather than normally sodium-dependent) conduction. CONCLUSIONS: These data suggest that Ca2+ treatment for hyperkalemia restores conduction through Ca2+-dependent propagation, rather than restoration of membrane potential or "membrane stabilization." Our findings provide a mechanistic rationale for Ca2+ treatment when hyperkalemia produces abnormalities of conduction (i.e. QRS prolongation). [ABSTRACT FROM AUTHOR]

The orientation of ice crystals affects their microphysical behaviour, growth, and precipitation. Orientation also affects interaction with electromagnetic radiation, and through this it influences remote sensing signals, in situ observations, and optical effects. Fall behaviours of a variety of 3D-printed plate-like ice crystal analogues in a tank of water–glycerine mixture are observed with multi-view cameras and digitally reconstructed to simulate the falling of ice crystals in the atmosphere. Four main falling regimes were observed: stable, zigzag, transitional, and spiralling. Stable motion is characterised by no resolvable fluctuations in velocity or orientation, with the maximum dimension oriented horizontally. The zigzagging regime is characterised by a back-and-forth swing in a constant vertical plane, corresponding to a time series of inclination angle approximated by a rectified sine wave. In the spiralling regime, analogues consistently incline at an angle between 7 and 28°, depending on particle shape. Transitional behaviour exhibits motion in between spiral and zigzag, similar to that of a falling spherical pendulum. The inclination angles that unstable planar ice crystals make with the horizontal plane are found to have a non-zero mode. This observed behaviour does not fit the commonly used Gaussian model of inclination angle. The typical Reynolds number when oscillations start is strongly dependent on shape: solid hexagonal plates begin to oscillate at Re =237 , whereas several dendritic shapes remain stable throughout all experiments, even at Re > 1000. These results should be considered within remote sensing applications wherein the orientation characteristics of ice crystals are used to retrieve their properties. [ABSTRACT FROM AUTHOR]

This study reports the effects of changes in the waveform and frequency of radio frequency (RF) energy on the tissue ablation range. We developed a 70-watt RFA generator that provides sine and square waves and allows frequency control between 10 Hz and 500 kHz. The changes in the ablation range according to the waveform and frequency were observed using the developed generator. In the waveform variation test, the distance between the electrodes and the electrode type were changed for both waveforms with the frequency set to 500 kHz. In the frequency variation test, the waveform and electrode type were changed with the frequency set to 10, 100, and 500 kHz, while the distance between the electrodes was set to 20 mm. A fixed 45 voltage was applied using the bipolar method. RF energy was applied for 90 s in vitro. The temperature was regulated to not exceed 70°C. The ablation range was calculated using ImageJ software. The analysis results showed that the ablation range was larger with the square wave than with the sine wave and at 10 kHz than at 500 kHz. The developed generator can advance research on ablation area and depth in RF ablation. [ABSTRACT FROM AUTHOR]

In laminar cooling, the cooling intensity is directly impacted by the heat transfer coefficient and affects the microstructure of metal materials, which in turn affects product performance. In order to determine the laminar cooling heat transfer coefficient, this study suggests a certain approach. Using the nozzle as the center, the dispersal form of coefficient of heat transfer as piecewise function formed a straight line and half sine wave was determined. It lays out the steps to take in experimental data, operating parameters, and structural parameters to get function's characteristic parameters. Experimental results confirm the method's correctness, and the effect of metal-specific characteristics on the temperature field was studied. A solid theoretical foundation for the field production process was provided by the mutual verification of the experimental and computed outcomes. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) systems or simultaneous wireless information and power transfer (SWIPT) systems support multiple charging frequency standards and usually transmit two or more frequencies simultaneously. Multi-frequency sinusoidal pulse width modulation (MF-SPWM) technology can output multiple sine wave frequencies at the same time with only one inverter, which effectively reduces the system size and improves compatibility. However, MF-SPWM and dead-time make the MF-inverter highly nonlinearized, with significant effects on the desired frequencies and the total harmonic distortion (THD) of the multi-frequency output. In this paper, a double Fourier series-based method of harmonic analysis for the dual-frequency inverter (DF-inverter) is proposed, which can accurately calculate the magnitude of each of the harmonics in the output of the DF-inverter taking into account the influence of dead-time. The calculation methods of the minimum pulse width and voltage THD of the DF-inverter are provided. An analysis shows that when the dead-time is less than the minimum pulse width, its influence is negligible. Meanwhile, when the dead-time is slightly larger than the minimum pulse width, there is a trade-off between the desired frequency component and the THD. Experimental results are given and they are consistent with the analytical results of the proposed method, and the error is within 2%. [ABSTRACT FROM AUTHOR]

This paper introduces and analyzes three innovative Linear Prediction (LP) models, consisting of two Fractional Order (FO) LP models and an integer LP model. The closed-form expressions for the proposed methods-namely, Two Parameter FO Linear Prediction (TP-FLP), FO Convex Linear Prediction (FCLP), and integer Convex Linear Prediction (CLP)-are derived for derivative order 0 ≤ α ≤ 2 . These derivations contribute to a more profound understanding of underlying mathematical principles of the proposed predictor. The foundation of our proposed methodologies is based on the presentation of the current signal sample as a linear combination of the FO derivative of two past samples, coupled with the utilization of the convex combination technique. An extensive set of experiments is conducted to compare the effectiveness of the proposed models with baseline methods involving two traditional LP models: First- and Second-order LP, along with the One Parameter FO Linear Prediction (OP-FLP) model. The performance evaluation encompasses a diverse range of signal types, including sinusoidal waves, damped sine waves, electroencephalogram (EEG), and speech signals. The simulation results demonstrate significant advancements achieved by the proposed models. Notably, the proposed FCLP exhibits a remarkable prediction gain of 24.74 dB, outperforming baseline methods such as OP-FLP, First- and Second-order LP models, that achieve prediction gains of 23.17, 23.15, and 10.14 dB, respectively. [ABSTRACT FROM AUTHOR]

This paper endeavors to tackle the issue of horizontal vibrations encountered in high-speed and ultra-high-speed elevator cabins during operation. Given the limitations of traditional passive-control guide shoes in effectively mitigating these vibrations and the complexity and cost associated with active control systems, a novel approach involving passive-control rolling guide shoes (PCRGS) integrated with hydraulic damping is explored. The PCRGS incorporates a hydraulic actuator and hydraulic damping, which can be modeled by a mechanical and hydraulic co-simulation model using AMESim2020 software. The simulation reveals a substantial reduction in cabin vibrations equipped with PCRGS. Specifically, under pulse excitation, the reduction ranges from 26.2% to 27.5%; under white noise excitation, it varies between 14.3% and 17.1%; and under sine wave excitation, the reduction spans 21.2% to 24.1%. Notably, the system meets the stringent 'Excellent' (<=0.07 m/s2) performance criteria under sine wave excitation at lower frequencies, signifying its high effectiveness. These findings not only underscore the potential of hydraulic passive-control guide shoes in mitigating elevator vibrations but also provide invaluable guidance for their further development and refinement. [ABSTRACT FROM AUTHOR]

Due to isotropic superconducting properties and the lack of breaking of inversion symmetry for conventional s‐wave superconductors, a nonreciprocal superconducting diode effect is absent. Recently, a series of superconducting structures, including superconducting superlattice, and quantum‐material‐based superconducting Josephson junction, have exhibited a superconducting diode effect in terms of polarity‐dependent critical current. However, due to complex structures, these composite systems are not able to construct large‐scale integrated superconducting circuits. Here, it is demonstrated that the minimal superconducting electric component‐superconducting nanowire‐based diode with a nonreciprocal transport effect under a perpendicular magnetic field, in which the superconducting to normal metallic phase transition relies on the polarity and amplitude of the bias current. These nanowire diodes can be reliably operated near at all temperatures below the critical temperature, and the rectification efficiency at 2 K can be more than 24%. Moreover, the superconducting nanowire diode is able to rectify both square wave and sine wave signals. Combining the superconducting nanowire‐based diodes and transistors, superconducting nanowires hold the possibility to construct novel low‐dissipation superconducting integrated circuits. [ABSTRACT FROM AUTHOR]

This article proposes a novel nonsingular fast terminal sliding mode control (N-NFTSMC) with a sliding mode disturbance observer (SDOB) for permanent magnet synchronous motor (PMSM) servo control. Firstly, to reduce the chattering issue, a new sliding mode reaching law (NSRL) is proposed for the N-NFTSMC. Secondly, to further improve the dynamic tracking accuracy, we introduce a sliding disturbance observer to estimate unknown disturbances for feedforward compensation. Comparative simulations via Matlab/Simulink 2018 are conducted using the traditional NFTSMC and N-NFTSMC; the step simulation results show that the chattering phenomenon was suppressed well via the N-NFTSMC scheme. The sine wave tracking simulation proves that the N-NFTSMC has better dynamic tracking performance when compared with traditional NFTSMC. Finally, we carry out experiments to validate that the N-NFTSMC adequately suppresses the chattering issue and possesses better anti-disturbance performance. [ABSTRACT FROM AUTHOR]

In this paper, we present a CMOS rail-to-rail second-generation voltage conveyor (VCII) suitable for low power applications, implemented in 180 nm CMOS technology with a supply voltage of ± 0.9 V. The proposed VCII consists of a current and voltage buffer operating in class AB. At the input of the voltage buffer, there is a bulk-driven differential amplifier, which provides a rail-to-rail input common-mode voltage. A common source output stage in class AB provides rail-to-rail at the output of the voltage buffer. The transistors are designed to operate in moderate inversion, achieving a relatively large current and voltage buffer bandwidth of 298.3 MHz and 173.2 MHz, respectively, with a power consumption of 157 μW. A sine wave with an amplitude of 1.5 Vpp and a frequency of 1 MHz on the output buffer has a total harmonic distortion of only 0.29%. The application of VCII in a relaxation oscillator with a frequency of up to 10 MHz is demonstrated, as well as its comparative characteristics with reference to other relevant square-wave generators published in the literature. [ABSTRACT FROM AUTHOR]

The active power losses are dependent on the flowing electric power value through overhead and cable lines. The current flow through the conductor causes negative phenomena to occur, such as released heat. The source of the current harmonics is the non-linear loads. Hence, the skin effect occurs, and the current carrying capacity of cables is reduced. This results in the increase in and uneven distribution of the temperature inside the conductor. This paper presents a comparison of the temperature distribution inside a power cable for an ideal 50 Hz sine wave and highly distorted current (T H D I = 41 %) . The calculated active power losses for the IEC 60287-1-1:2006+A1:2014 standard and the method described in the literature were used as a basis for further calculations. The obtained results revealed the problem of the uneven distribution of the conductor temperature. Considering the skin effect, increasing the temperature in the outer layers leads to severe damage and faster insulation aging. The abovementioned phenomenon is a decrease in the permissible load capacity of the conductor. The table given in the IEC 60364-5-52 standard summarizes the percentage contribution of the third harmonic to the current waveform. For percentages between 15% and 33%, the current carrying capacity is reduced by up to 86% of the full-load current rating. In addition, consideration of thermal conditions forces the use of cables with larger cross-sections. This leads to their non-optimal use and makes the investment more expensive from an economic point of view. [ABSTRACT FROM AUTHOR]

Traditional valve-controlled hydraulic cylinders are usually very inefficient due to power loss through the control valve. An efficient alternative architecture is to distribute power electrically rather than hydraulically to a group of cylinders and drive each cylinder via individual servomotor-driven pumps. This arrangement is called electrohydrostatic actuation. Such actuators are currently available for power ratings of several hundred watts or greater, but not in the sub-100 W range. This paper details the design, simulation and testing of a piezopump which is intended to address this gap. The motivation is for aerospace applications, and in particular accessory actuators used in the landing gear system. The 10–100 W range is a high-power output for a piezopump, and to achieve this a novel design using disc-style reed valves was developed to allow pumping frequencies above 1 kHz. These high frequencies necessitated the development of custom power electronics capable of delivering 950 V peak-peak sine wave excitation to a largely capacitive load. Experimental results show that the piezopump is capable of delivering over 30 W of hydraulic power, and at no-load can deliver up to 2 L/min of flow at 1250 Hz. Future development includes a transition to multi-cylinder pumps, and improved reed-valve modelling to improve the accuracy of simulated performance. [ABSTRACT FROM AUTHOR]

In the inverter circuit, the speed at which the MOSFET is impacted by the presence of a parasitic inductor within the printed circuit board (PCB) leads to a delay in the switching process. Furthermore, the parasitic inductor within the circuit can easily form an LC oscillation with the parasitic capacitor of the MOSFET. These two issues result in an inconsistency between the actual output of the MOSFET and the driving signal waveform, leading to distortion in the sinusoidal pulse width modulation (SPWM) waveform and an increase in total harmonic distortion (THD). It is a common practice to mitigate gate oscillation by introducing a resistor at the gate of the MOSFET. However, elevating the resistance leads to deceleration in the charging process of the MOSFET's parasitic capacitor, consequently causing an increase in the switching delay, and thereby increasing THD. Therefore, an effective strategy to reduce THD is proposed in this paper, while augmenting the gate resistance, computing the MOSFET switching delay, and applying corrective compensation. In this way, the inherent issues of the switch are addressed, resulting in inverter output waveforms that closely resemble sine waves and reduced THD. Through a combination of simulation and empirical experimentation, the efficacy of the proposed approach in significantly reducing THD in the inverter's output waveform has been empirically substantiated. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) concrete printing is increasingly becoming popular because it provides a powerful platform for the fabrication of structural components in freeform architectural shapes. Although manufacturing technology and material property improvement are advancing rapidly, the development of methods to predict the structural capacity of printed elements is lagging. This paper presents an experimental and numerical investigation to predict the axial load capacity of a printed concrete wall module. The module geometry contains two parallel thin wall sections connected by an internal sine wave. The thin wall section reduces the concrete consumption, and the internal sine wave provides lateral stability during printing and in the hardened state. It is a popular pattern printed by many researchers and in some real constructions. Two wall module specimens with the prescribed geometry were 3D-printed and tested under compression. The maximum loads of 2,890 and 2,924 kN were obtained for the first and second wall specimens, respectively. Additionally, samples were taken from different locations of a printed prototype to identify printed material characteristics. These experimental characteristics were then introduced to a finite-element numerical model for predicting the structural performance of the printed wall module under compression load. The results showed that the experimental maximum load and stiffness have 1% and 5% differences with numerical outputs, respectively. Based on such a validated model, the failure modes are discussed, and an analytical method is proposed for predicting the axial capacity for the prescribed geometry. [ABSTRACT FROM AUTHOR]

Snake robots have redundant kinematic structure which predetermines them for motion in rough and unstructured terrain with obstacles, narrow spaces or environments with different ground levels. Dynamic modeling of snake robots is an important element in the development of control strategies for them. This paper, deals with the dynamic model of a snake robot moving in a pipeline. The model is based on Newton's mechanics with consideration of the viscous as well as Coulomb friction model. The paper uses Hertz theory for modeling of contact between a snake robot and side walls of a pipeline. Based on optimization process results, the friction effects as well as analyses of snake robot propulsive force are investigated. The main contributions of the paper are the developed dynamic model for snake robot motion in a pipeline, open source code of the developed model in MATLAB, and analyses of individual parameters of snake robot motion. • Propulsive force of snake robot moving in a pipeline is significantly affected by friction of the side walls. • One full sine wave formed by snake robot links ensures maximum average velocity. • Considering Coulomb friction the snake robot performs more jerked motion in comparison with viscous friction. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) simulations were employed to model a novel double sine wave corrugated heat exchanger surface. The turbulent flow within the heat exchanger channels was simulated using the k - ω SST model for the corrugated cases. In contrast, a laminar model was applied to the flat plate heat exchanger without corrugations. The simulation results demonstrate that 3D-printed polymer heat exchangers are effective for heat transfer, with the double-sine wave corrugated surface outperforming the single-sine wave corrugated surface. Specifically, the double sine wave configuration achieved a 20% higher Nusselt number and a 15% lower friction factor than the single sine wave, indicating superior thermal-hydraulic performance. Optimal performance was observed with low amplitude and frequency of the sine waves, suggesting that small protrusions and wider-spaced corrugations enhance heat transfer without significantly increasing pressure drop. These findings have significant implications for the design of efficient and cost-effective heat exchangers, particularly in applications where both thermal performance and energy efficiency are critical. Further experiments with full-scale heat exchangers are necessary to validate these results and explore practical applications. [ABSTRACT FROM AUTHOR]

During the operation of combine harvesters, the cutting platform height is typically controlled using manual valve hydraulic systems, which can result in issues such as delays in adjustment and high labor intensity, affecting both the quality and efficiency of the operation. There is an urgent need to enhance the automation level. Conventional methods frequently employ single-point measurements and lack extensive area coverage, which means their results do not fully represent the terrain's variations in the area and are prone to local anomalies. Given the inherently undulating terrain of farmland during harvesting, a control strategy that does not adjust for minor undulations but only for significant ones proves to be more rational. To this end, a sine wave superposition model was established to simulate three-dimensional ground elevation changes, and an area array LiDAR was used to collect 8 × 8 data for the header height. The effects of mounds and stubble on the measurement results were analyzed, and a dynamic process simulation model for the solenoid valve core was developed to analyze the on/off delay characteristics of a three-position four-way electromagnetic directional valve. Moreover, a physical model of the hydraulic system was constructed based on the Simscape module in Simulink, and the Bang Bang switch predictive control system based on position threshold was introduced to achieve early switching of the electromagnetic directional valve circuit. In addition, an automatic control system for cutting platform height was designed based on an STM32 microcontroller. The control system was tested on the hydraulic automatic control test rig developed by Shanxi Agricultural University. The simulation and experimental results demonstrated that the control system and strategy were robust to output disturbances, effectively enhancing the intelligence and environmental adaptability of agricultural machinery operations. [ABSTRACT FROM AUTHOR]

Among many other applications, electronic converters can be used with sensors with analogue outputs (DC voltage). This article presents an analogue computation converter with two DC voltages at the inputs (one input changes the frequency of the output signal, another input changes the amplitude of the output signal) that provide a periodic sinusoidal signal (with variable frequency and amplitude) at the output. On the basis of the analogue computation converter is a nonhomogeneous second-order linear ordinary differential equation which is solved analogically. The analogue computation converter consists of analogue multipliers and operational amplifiers, composed of seven function circuits: two analogue multiplication circuits, two analogue addition circuits, one non-inverting amplifier, and two integration circuits (with RC time constants). At the output of an oscillator is a sinusoidal signal which depends on the DC voltages applied on two inputs (0 ÷ 10 V): at one input, a DC voltage is applied to linearly change the sinusoidal frequency output (up to tens of kHz, according to two time constants), and at the other input, a DC voltage is applied to linearly change the amplitude of the oscillator output signal (up to 10 V). It can be used with sensors which have a DC output voltage and must be converted to a sine wave signal with variable frequency and amplitude with the aim of transmitting information over longer distances through wires. This article presents the detailed theory of the functioning, simulations, and experiments of the analogue computation converter. [ABSTRACT FROM AUTHOR]

The study investigated the fabrication and characterization of a controllable wavy patterned mold using an ultra-precision diamond machining system. The design method of cutting tool path for controllable wavy pattern on a cylindrical surface, considering the tool radius, was discussed. The target was designed as periodic sine wave and random amplitude wave to develop components for next-generation displays. The effectiveness of the designed tool path was confirmed by comparing the machined surface profiles. The compensated tool path was able to reduce the machined shape error by approximately 50%. The optical characteristics of the machined pattern were analyzed by the luminance distribution of the transmitted laser through the replicated optical film for each machined tool path. When the compensated tool path was applied, a symmetrical distribution line with two spots of higher luminance concentration was observed. Finally, an investigation was conducted on the machinability of controllable randomness for next-generation display components, and their optical characteristics were evaluated. [ABSTRACT FROM AUTHOR]

The multi-cell tube has been widely studied and applied in vehicle collision energy absorption due to its superior energy absorption capacity compared to traditional single tubes. The origami thin-walled structure is at the forefront of research on automotive energy absorption structures, thanks to its advantages such as low initial peak force, high energy absorption efficiency, and predictable deformation. In this study, a group of biologically inspired multi-cell tubes with origami-type outer walls was designed, and three design variables including the thickness of the outer wall, the ratio of outer to inner wall thickness, and the peak value ratio of the sine wave period were optimized. The design of experiment (DOE) was used to select the sample points needed to construct the surrogate model, and then a response surface model was built based on the criteria of minimum initial peak force (PCF) and maximum specific energy absorption (SEA). Finally, the non-dominated sorting genetic algorithm (NSGA-II) was used to optimize the design variables, resulting in a series of optimal solutions. The improved algorithm was used to select the best solution according to the requirements, and the optimization results were verified for their accuracy and reliability through simulation experiments. The results show that changing the values of the three design variables of the thin-walled tube will significantly affect the initial peak force and specific energy absorption. The optimal values after optimization were found to be 109.063 KN for PCF and 25.786 J/g for SEA. [ABSTRACT FROM AUTHOR]

In a wide range of current changes, it is difficult for current transformer to carry out steady energy extraction, because the excitation characteristics of current transformer are interfered by load impedance. To solve this problem, a dynamic impedance control strategy of voltage source converter is proposed. The method dynamically and continuously adjusts the secondary impedance according to the different states of the primary current, which not only meets the requirement of load power consumption under the condition of low current, but also reduces the influence of the magnetic saturation problem of the core. The principle of energy collection is analyzed, and the equivalent model of current transformer and circuit is established. The relationship between excitation characteristics and impedance parameters is discussed empirically-, which lays a foundation for the construction of the final control strategy. The experimental results show that, first, without capacitive impedance control, the effective value of ct induced voltage is 37.313V, and the corresponding energy collection power is 1.39W. Under the capacitive impedance control, the RMS value of ct induced voltage increases to 72.868V and the energy collection power reaches 5.31W. It can be seen that when the capacitive reactance state is changed, the RMS value of induced voltage and energy collection power are significantly different. Second, the output current of the strong current generator is adjusted to 70a, and when the current increases, the system enters the magnetic saturation state. At this time, the positive and negative half waves of the voltage and current on the CT secondary side produce high amplitude spike pulse waves, which is very dangerous to the insulation of the CT winding and the safety of the load equipment. Under the same conditions, after the induction impedance control is added to the CT core, the magnetic saturation state is relieved, and the waveform changes from peak wave to sine wave, the energy taking system returns to normal working state, the DC voltage output is normal, and the system power supply is stable. Third, the output current of the strong current generator continues to increase to 80a, with the increase of the primary current, the system waveform state remains stable, and the induced voltage and DC output voltage remain constant near the preset reference value. It can be concluded that the magnetic induction intensity of the core will be positively affected by the capacitive impedance operation, and the energy supply effect of the transformer will be increased. The operating characteristics of inductance impedance can reduce the magnetic induction intensity of the iron core, thus inhibiting the saturation of the iron core under high current operating conditions and maintaining stable power output. [ABSTRACT FROM AUTHOR]

Summary A wide‐range direct digital frequency synthesizer (DDS) is considered an essential component that is used in measuring electrochemical impedance spectroscopy (EIS). Since it depends on exciting the electrochemical sensor by a pure sine wave, total harmonic distortion (THD) is considered a challenging specification for an accurate EIS measurement. This paper introduces a complete system and circuit designs of a wide range DDS with a comprehensive system model using MATLAB environment. In addition, it presents the usage of a reconfigurable digital‐to‐analog converter (DAC) on the circuit level that is used either as a 4‐bit delta‐sigma ( ΔΣ$$ \Delta \Sigma $$) DAC or an 8‐bit binary‐weighted DAC for both low‐ and high‐frequency ranges, respectively. The designed DDS generates an output frequency range from 762.933 Hz to 10 MHz using a physical 8‐bit DAC. The circuits are simulated using 0.18 μm CMOS technology. The designed DDS system achieves THD less than 0.05% with superior free dynamic range (SFDR) 66 dBc for low‐frequency range and 0.08% with SFDR 62 dBc for high‐frequency range. The DDS circuits occupy an area of 400  × 800 μm. The whole system consumes a 2.5 mW power consumption from a 1.8 V supply. [ABSTRACT FROM AUTHOR]

In order to study the dynamic characteristics and destabilisation damage mode of the accumulation body slope under the action of ground vibration, and to provide theoretical guidance and technical support for the optimization design of reinforcement of similar slopes, a large shaking table model (scale 1:16) test with a specific accumulation body slope was conducted as a prototype. The dynamic response and deformation characteristics of the model slopes were observed by inputting sine, Wolong, and EI Centro waves to the bottom of the model slopes, respectively. The test results showed that in the vertical direction and on the slope surface, the acceleration amplification factor (AAF) increased with the increasing of altitude, and presented a nonlinear change. In the horizontal direction, the AAF increased with distance from the slope surface. There was also a slope surface amplification effect with the AAF reaching its maximum at the slope shoulder. Similar laws were obtained after numerical simulation of the prototype slope by FLAC3D software. Different types of seismic waves exhibited different effects on the AAF. Sine waves showed the largest effect, followed by Wolong waves, and EI centro waves exhibited the smallest effect. The AAF of the modelled slope was different for different input wave frequencies. As the input frequency of Sine waves increased, the AAF increased first and then decreased. This change coincided with the AAF reaching its maximum value at 25–30 Hz. The AAF of the modelled slope varied when the input wave amplitude values were different. When the AAF reached its maximum value, the input amplitude was 0.4 g. By analysing the slope failure progression, it showed that the slope of an accumulation body began with local sliding at the front edge, followed by internal sliding of it, and the overall sliding. [ABSTRACT FROM AUTHOR]

Active vision systems (AVSs) have been widely used to obtain high-resolution images of objects of interest. However, tracking small objects in high-magnification scenes is challenging due to shallow depth of field (DoF) and narrow field of view (FoV). To address this, we introduce a novel high-speed AVS with a continuous autofocus (C-AF) approach based on dynamic-range focal sweep and a high-frame-rate (HFR) frame-by-frame tracking pipeline. Our AVS leverages an ultra-fast pan-tilt mechanism based on a Galvano mirror, enabling high-frequency view direction adjustment. Specifically, the proposed C-AF approach uses a 500 fps high-speed camera and a focus-tunable liquid lens operating at a sine wave, providing a 50 Hz focal sweep around the object's optimal focus. During each focal sweep, 10 images with varying focuses are captured, and the one with the highest focus value is selected, resulting in a stable output of well-focused images at 50 fps. Simultaneously, the object's depth is measured using the depth-from-focus (DFF) technique, allowing dynamic adjustment of the focal sweep range. Importantly, because the remaining images are only slightly less focused, all 500 fps images can be utilized for object tracking. The proposed tracking pipeline combines deep-learning-based object detection, K-means color clustering, and HFR tracking based on color filtering, achieving 500 fps frame-by-frame tracking. Experimental results demonstrate the effectiveness of the proposed C-AF approach and the advanced capabilities of the high-speed AVS for magnified object tracking. [ABSTRACT FROM AUTHOR]

An OFDM signal consists of a number of independently modulated SCs, which can give a large peak-to-average power (PAP) ratio when added up coherently. The peak power is defined as the power of a sine wave with amplitude equal to the maximum envelope value. Hence, an unmodulated carrier has a PAP ratio of 0 dB. An alternative measure of the envelope variation of a signal is the Crest factor, which is defined as the maximum signal value divided by the RMS signal value. For an unmodulated carrier, the Crest factor is 3 dB. This 3-dB difference between the PAP ratio and Crest factor also holds for other signals, provided that the center frequency is large in comparison with the signal bandwidth. [ABSTRACT FROM AUTHOR]

An improved combined-mode power converter (CMPC) for a solar photovoltaic (SPV) system is presented in this paper. Ten-power electronic switches are utilised for the functioning of the converter. The proposed converter has four modes of operation: buck, boost, inverter, and mixed mode. The new CMPC topology provides a unique and complex switching sequence for implementing the mixed-mode operation. This work uses a field-programmable gate array (FPGA) for mode selection and to create PWM (MS-PWM) signals. A digital MS-PWM controller is configured to switch between improved stepped perturb and observe (ISPO) maximum-power point tracking (MPPT) and sine wave PWM (SPWM). The ISPO provides the appropriate duty cycle for buck/boost operation, while the SPWM controls the inverter operation. This work's new digital PWM control algorithm supports mode selection, PWM generation, and reconfiguring PWM generation timings. The whole framework for constructing the MS-PWM controller employs a very high-speed integrated circuit hardware description language (VHDL). Simulation and experimental results are presented, proving that the digital MS-PWM controller uses fewer resources with improved accuracy. [ABSTRACT FROM AUTHOR]

This paper compares various angle-tracking algorithms to balance the performance and noise for a steering-by-wire (SBW) system. Direct and quiet steering experiences can improve drivers' acceptance of the SBW system. Linear quadratic regulator (LQR) control, robust control, and conventional cascade proportional–integral (PI) control have been developed and compared both theoretically and experimentally. To avoid the risky and time-consuming parameter-tuning process, a high-fidelity steering resistance model, which comprises a linear two-degree-of-freedom vehicle model and a dynamic LuGre friction model is established. Step and sine wave tests are simulated in a Matlab/Simulink environment to determine the reasonable parameter region for various methods. Then, the three types of algorithms are implemented on a prototype SBW vehicle and compared under the same scenarios. Finally, the simulated and experimental results are illustrated in detail. According to the indicators of control bandwidths, steady-state errors, cockpit sounds, and current waveforms, it is clear that LQR and robust control can achieve faster response and more acceptable noise, with uncertain and relatively larger tracking errors. Cascade PI control, in comparison, can realize smaller steady-state errors and gentler current waveforms, with slight noise and slower response. [ABSTRACT FROM AUTHOR]

This paper provides a comparative analysis of bipolar versus unipolar Sinusoidal Pulse Width Modulation (SPWM) in DC-AC inverters, focusing on Total Harmonic Distortion (THD) across modulation indices and the latter's effects on the R-L loads. Using the PIC18F2431 microcontroller for its efficiency, a single-phase inverter accomplished to deliver a high-fidelity sine wave. This study discovered that while both SPWM methods reduce harmonics, the unipolar approach yields more uniform THD reduction and superior performance, particularly noticeable in RL load conditions, where minimal harmonic distortion is crucial. The bipolar inverter, despite a higher initial THD, shows a considerable improvement at higher indices, significantly enhanced by an LC low-pass filter. This filter is a key component in achieving sub-1% THD levels at full modulation, ensuring optimal sine wave quality. The findings highlight the operational differences between the SPWM techniques and the importance of the LC filters in ameliorating the inverter output for various power applications. [ABSTRACT FROM AUTHOR]

The cable-stiffened single-layer latticed shell is an innovative structural design that achieves a perfect balance between lightweight and stability by combining cables and a latticed shell. However, the study on dynamic response and failure mechanism of cable-stiffened single-layer latticed shell under seismic action is still lacking. Therefore, small-scale shaking table tests of two kinds of single-layer spherical latticed shells are carried out; the dynamic response and failure mode of the two shells under sine wave earthquake are investigated by using time history analysis. The conclusions show that the introduction of the prestressed cable plays an important role in improving the seismic performance of the single-layer latticed shell, and the cable-stiffened single-layer latticed shell has better load capacity and seismic performance under earthquake action than the ordinary single-layer latticed shell structure. [ABSTRACT FROM AUTHOR]