Triangular Wave Research Articles

Pulse electroosmotic flow of Newtonian fluids in parallel plate microchannels under triangular and half-sinusoidal pulse electric fields

Unlike the conventional electroosmotic flow (EOF) driven by direct current and alternating current electric fields, this study investigates the pulse EOF of Newtonian fluids through a parallel plate microchannel actuated by pulse electric fields. Specifically, the pulses considered encompass triangular and half-sinusoidal pulse waves. By applying the Laplace transform method and the residual theorem, the analytical solutions for the velocity and volumetric flow rate of the pulse EOF associated with these two pulse waves are derived, respectively. The influence of pulse width a¯ and electrokinetic width K on velocity is further considered, while the volumetric flow rate as a function of time t¯ and electrokinetic width K is examined separately. A comparison of the volumetric flow rates related to these two pulse waves under varying parameters is also conducted. The research findings indicate that irrespective of the pulse wave, a broader pulse width results in a prolonged period and increased amplitude of the velocity profile. Elevating the electrokinetic width yields higher near-wall velocities, with negligible effect on near-center velocities. It is noteworthy that regardless of the electrokinetic width, the near-wall velocity exceeds that of the near-center during the first half-cycle, while the situation reverses during the second half-cycle. The volumetric flow rate varies periodically with time, initially surging rapidly with electrokinetic width before gradually stabilizing at a constant level. More interestingly, independent of pulse width and electrokinetic width, the volumetric flow rates linked to the half-sinusoidal pulse wave consistently surpass those of the triangular pulse wave. For any pulse width, the volumetric flow rates corresponding to the two pulse waves grow with higher electrokinetic widths, especially prominent at alternating intervals of the two half-cycles within a complete cycle. These findings have important implications for improving the design and optimization of microfluidic devices in engineering and biomedical applications utilizing pulse EOF.

Improved adaptive robust control of direct-drive pump-valve cooperative brake-by-wire unit with disturbance compensation

Abstract Aiming at the needs of high-level autonomous driving, a direct-drive pump-valve coordinated brake-by-wire unit was designed. To improve the response speed, control accuracy, and robustness of the brake-by-wire unit, an improved adaptive integral robust control method (AIRC-AD) based on a novel adaptive law and disturbance compensation was proposed. By integrating pressure tracking error information and overall parameter estimation error information, a novel parameter adaptive law with fast convergence speed was designed. A finite-time disturbance observer was designed to observe the overall system disturbance, improving the system’s anti-disturbance performance. Finally, the stability of the control method was proven using the Lyapunov stability proof method. The results show that under step target signals, sinusoidal target signals and triangular wave target signals, AIRC-AD has better response speed and control accuracy. In conditions such as increased permanent magnet temperature, increased coil resistance, or reduced flow area due to hydraulic pipeline blockage, AIRC-AD has better adaptability. The unit and the method can meet the demand for precise braking force control in high-level autonomous driving.

Dynamic modelling and mechanical analysis of an inertial linear piezoelectric actuator with double stators

Abstract To achieve higher output performance in precision applications, and in order to gain deeper insight into operation principle, a dynamic model is established including the transmission relationship between the stators, the driving shaft, and the mover based on a slip-slip type inertial linear piezoelectric actuator with double stators. The influence of stator material and symmetry ratio of the excitation signal on the vibration characteristics of the stator and the output performance are investigated. This study reveals the relationship between these factors through a combination of simulations and experiments. Prototypes using several materials are machined and assembled, and the vibration characteristics and output performance are rigorously tested. The results obtained from the experimental measurements are consistent with the simulation results, confirming the validity and rationality of the dynamic model. The experimental results of the stator, as well as the actuator, are analyzed. It can be concluded that the actuator is able to output a larger effective displacement in one motion period with the increased symmetry ratio of the triangular wave signal, applied with a higher operating frequency, resulting in a higher output velocity of 42 mm/s and a larger load of 300 g with the steel stator, and a higher displacement resolution of 18 nm can be achieved using the AL alloy stator. This research not only provides an effective method for enhancing and selecting the desired output performance for the researched actuator but also can be extended to other slip-slip type inertial linear piezoelectric actuators.

A new processing method of ground acceleration data for fast and accurate evaluation of maximum seismic structural response

AbstractA new processing method of ground acceleration data is proposed for the fast and accurate evaluation of the maximum seismic structural responses. The proposed method consists of a trimming method and a down‐sampling method. The proposed trimming method is based on ground acceleration power and contains compensation procedures for the trimmed ground acceleration. The proposed down‐sampling method effectively uses FIR filter, whose weight coefficients are derived from the correspondence between the responses under a triangular wave and the equivalent impulse input. It is demonstrated through numerical examples for response spectrums and a full‐scale high‐rise building model that the proposed method enables fast and accurate evaluation of the maximum seismic structural responses.

The Effect of Drive Signals on Output Performance of Piezoelectric Pumps

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.

Model-based estimation of heart movements using microwave Doppler radar sensor.

Heart rate is one of the most crucial vital signs and can be measured remotely using microwave Doppler radar. As the distance between the body and the Doppler radar sensor increases, the output signal weakens, making it difficult to extract heartbeat waveforms. In this study, we propose a new template-matching method that addresses this issue by simulating Doppler radar signals. This method extracts the heartbeat waveform with higher accuracy while the participant is naturally sitting in a chair. An extended triangular wave model was created as a mathematical representation of cardiac physiology, taking into account heart movements. The Doppler radar output signal was then simulated based on this model to automatically obtain a template for one cycle. The validity of the proposed method was confirmed by calculating the PPIs using the template and comparing their accuracy to the R-R intervals (RRIs) of the electrocardiogram for five participants and by analyzing the signals of eight participants in their natural state using the mathematical model of heart movements. All measurements were conducted from a distance of 500 mm. The correlation coefficients between the RRIs of the electrocardiogram and the PPIs using the proposed method were examined for five participants. The correlation coefficients were 0.93 without breathing and 0.70 with breathing. This demonstrates a higher correlation considering the long distance of 500 mm, and the fact that body movements were not specifically restricted, suggesting that the proposed method can successfully estimate RRI. The average correlation coefficients, calculated between the Doppler output signals and the templates for each of the eight participants, exceeded 0.95. Overall, the proposed method showed higher correlation coefficients than those reported in previous studies, indicating that our method performed well in extracting heartbeat waveforms. Our results indicate that the proposed method of remote heart monitoring using microwave Doppler radar demonstrates higher accuracy in estimating the RRI of the electrocardiogram while at rest sitting in a chair, and the ability to extract the heartbeat waveforms from the measured Doppler output signal, eliminating the need to create templates in advance as required by conventional template matching methods. This approach offers more flexibility in the measurement environment than conventional methods.

Adaptive control of an amplified piezoelectric-driven micropositioning stage based on notch filter structure inspiration and neural network online tuning

Abstract Piezoelectric-driven flexure micro/nanopositioning stages often exhibit a low-damping resonance mode, which can easily excite mechanical resonance during high-speed movement, and significantly impact the control system's stability, control bandwidth, and trajectory tracking accuracy. To mitigate the reliance on the precise modeling of stage dynamics inherent in current resonant controllers, an adaptive control method based on a back propagation (BP) neural network was designed to suppress resonance in real-time. First, a piezoelectric-driven flexure micro/nanopositioning stage system was constructed. Next, a feedback controller similar to a notch filter was designed, with bilinear transformation applied based on the system's inherent parameters to determine the initial values. Finally, the designed adaptive control method was tested through trajectory tracking experiments using a triangular wave signal. The experimental results showed that, when tracking the triangular wave signal, the maximum tracking error was reduced by 72.66% compared to proportional-integral (PI) control alone and by 68.66% compared to proportional integral control combined with a traditional notch filter. The tracking results demonstrate a significant improvement in the stage's stability and tracking accuracy.

Design and Application Prototype of soft starting Three-Phase AC Motor by Using Analog Electronics Control for Teaching Aids of Power Electronics Practice

In general, palm oil processing factories, from fresh fruit bunches to Crude Palm Oil, require three-phase electric motors to drive or rotate it. The problems that often arise when using three-phase electric motors simultaneously in large numbers will result in very large surges in the electric current, which can affect the performance of electronic devices. To overcome this problem, a prototype of a three-phase AC voltage regulator circuit was made by adjusting the SCR triggering delay angle using an analog electronics equipment control that can be used for three-phase motor soft start applications in a palm oil factory. This prototype will be used as a learning tool for the practical for Aceh Polytechnic students for power electronics courses. This system is built with a method where the three-phase source is first lowered using a transformer arranged in a star on the primary and secondary sides, then each voltage is compared to the ground using an IC LM324, which aims to produce pulses wave. This pulse then connected to a triangular wave generator circuit, this triangular wave is then compared with the DC source voltage from the potentiometer, which aims to regulate the SCR triggering angle of SCR via MOC3063 driver, where the load used is resistive and connected in a star. The measurement using an oscilloscope and observing the change of triggering angle for several variations of each phase, the different Vrms voltage between measurements compared to mathematical analysis influenced by several factors, including, the transformer is made of three transformers that not identically, the electronic components used are not in ideal condition, and observations on the oscilloscope are carried out visually using the eye and manually adjusting the potentiometer rotation so that the level of measurement accuracy between one person and another will produce different values.

A photonic integrated chip for distinguishing the optical wave packets based on a neural-network

In this work, we use an optical-neural network to recognize a series of optical triangular and square wave packets. This chip is designed based on the reservoir computing, consisting of the directional couplers, phase shifters, Mach-Zehnder modulators, spiral waveguide and grating couplers. The non-linear activation function is obtained by the directional couplers. The optimization of the optical reservoir computing system is performed by tuning the voltage on the phase shifters to obtain the largest extinction ratio of the output signals for different input wave packets. The photonic integrated chip is fabricated on silicon-on-insulator and is characterized at an operation frequency of 3 GHz. The results demonstrate that the photonic integrated chip can efficiently distinguish between optical triangular and square wave packets.

Coexisting Charge Density Waves in Twisted Bilayer NbSe2.

Twisted bilayers of 2D materials have emerged as a tunable platform for studying broken symmetry phases. While most interest has been focused toward emergent states in systems whose constituent monolayers do not feature broken symmetry states, assembling monolayers that exhibit ordered states into twisted bilayers can also give rise to interesting phenomena. Here, we use first-principles density-functional theory calculations to study the atomic structure of twisted bilayer NbSe2 whose constituent monolayers feature a charge density wave. We find that different charge density wave states coexist in the ground state of the twisted bilayer: monolayer-like 3 × 3 triangular and hexagonal charge density waves are observed in low-energy stacking regions, while stripe charge density waves are found in the domain walls surrounding the low-energy stacking regions. These predictions, which can be tested by scanning tunneling microscopy experiments, highlight the potential to create complex charge density wave ground states in twisted bilayer systems.

Research on Outlier Detection Methods for Dam Monitoring Data Based on Post-Data Classification

Safety monitoring of hydraulic structures is a critical task in the field of hydraulic engineering construction. This study developed a method for preprocessing and classifying monitoring data for the identification of gross errors in hydraulic structures. By utilizing linear regression and wavelet analysis techniques, it effectively differentiated various waveform characteristics in data sets, such as Sinusoidal Wave Cyclical, Triangular Wave Cyclical, Seasonal Cyclical, and Weakly Cyclical growth types. In the experiments for gross error identification, the 3σ algorithm, K-medoids algorithm, and Isolation Forest algorithm were applied to test the data. The results showed that the K-medoids algorithm excelled in processing Sinusoidal Wave Cyclical Data Sets; the 3σ algorithm adapted better to Triangular Wave Cyclical Data Sets; the Isolation Forest algorithm performed well in handling data sets with significant anomalies or atypical fluctuations and excelled in scenarios with strong seasonality and large data fluctuations; and for complex Weakly Cyclical Growth Data Sets, all three algorithms were less effective, indicating the potential need for more advanced analysis methods or a combination of multiple techniques. Testing on actual engineering data further confirmed the importance of using specific gross error identification techniques for special data types after data set pre-classification, providing a more effective technical solution for the safety monitoring of hydraulic structures.

A method for evaluating the design scheme of continuous measuring bridge of the instrumented wheelset

This paper proposes a method for evaluating the design scheme of continuous measuring bridge of the instrumented wheelset, based on the theory of continuous measurement of wheel-rail forces, Finite Element Analysis, and Levenberg-Marquardt algorithm. The elastic strain at each placement point of the strain gauge on the web surface of the wheel is expanded into Fourier series, and the general mathematical expressions of the output signals for each symmetric component, each bridge, and the synthesized bridge are provided. Nine typical measuring bridge schemes of strain gauge arrangement on the wheel web surface and seven typical measuring bridge schemes of strain gauge arrangement inside the measuring holes are given. The finite element model of the wheel is established using software ABAQUS, and the moving force is applied to the rolling surface of the wheel for simulation calculations. The output signals of 16 typical measuring bridges are then obtained. By utilizing the mathematical formulas of the bridge outputs and the simulation results, a matrix expression describing the relationship between amplitudes of all harmonics and the bridge output is given, and the amplitudes of all the former 20 orders harmonics of the bridge signal are obtained by applying Levenberg-Marquardt algorithm. Based on the analysis results of the harmonic amplitudes, a method is proposed to quantitatively evaluate the output signals of a single bridge (which can be either harmonic or triangular wave) and the synthesized bridge. The mathematical expressions of the evaluation indicators are provided within the range of 0 to 1. Finally, the analysis results of the evaluation indicators for 16 typical measuring bridges are presented and compared. The proposed method is not only applicable to the bridge design of the instrumented wheelset but also to the evaluation of signals from channels of the data collector when the instrumented wheelset is being calibrated on the test rig.

Analysis of CFRP inter‐laminar cracking location under laser impacts

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

Mathematical modeling of creeping electromagnetohydrodynamic peristaltic propulsion in an annular gap between sinusoidally deforming permeable and impermeable curved tubes

The present work investigates the creeping peristaltic propulsion of viscid fluid in an annular gap between sinusoidally deforming permeable and impermeable curved tubes of similar shape under the influence of an externally imposed electric and magnetic field. In this model, the outer tube with a permeable wall surface is supposed to satisfy the Saffman slip condition. The flow equations are simplified by the estimation of a large wavelength in comparison with the radius of the external tube. An analytical solution for the axial velocity is obtained in the computational software MATHEMATICA. Graphical analyses are conducted to explore the variations in wall shear stress, velocity, pressure rise, frictional force, and stream function with respect to different emergent parameters, providing insight into the underlying physics of the flow phenomena. An investigation of the effects of the Hartmann number and electric field strength on the flow through a gap between deformable tubes with curved structures has important implications for a variety of engineering applications, including mechanical and biomedical engineering. The streamlines are plotted to discuss fluid trapping and visualize the flow pattern of the viscid fluid inside the curved annular domain. A comparative analysis of fluid transport induced by sinusoidal, triangular, trapezoidal, and square wave shapes is encountered with the help of streamlined contour diagrams. The comparison of pressure gradients in three different models is also discussed to gain insight due to fluid–structure interaction. A gap in the body of recently published literature is filled by the results discussed in this paper.

An image encryption scheme without additional key transmission based on an N-dimensional closed-loop coupled triangular wave model

Currently, many image encryption schemes either require additional secure channels for key transmission or employ a key that exhibits a lack of correlation with the plaintext, thereby reducing the security of the algorithm. This study proposes a novel image encryption scheme to address this issue. A new N-dimensional closed-loop coupled triangular wave model is developed to overcome the limitations of the sine function in chaotic systems while reducing the difficulty of the chaotic system design. Experimental analysis demonstrates that the generated chaotic systems exhibit complex chaotic behaviors and outperform other chaotic systems designed using the sine function. Specifically, we utilize difference extension technology to embed key information into the plaintext image and design a scrambling and diffusion algorithm based on Latin rectangles to encrypt the remaining pixel matrix without key information. Finally, the pixel matrix containing the key information is concealed to obtain the final ciphertext image. Simulation analysis and security evaluation demonstrate that the proposed algorithm outperforms the encryption performance and security of several advanced image encryption algorithms.

Study on physiological injuries of occupants under vertical impact loads

Under vertical impact loads, such as explosions, serious compressive deformation occurs in the pelvic bones and lumbar vertebrae of the human body leading to injuries or fatalities for occupants. This study focuses on the occupant-seat model in military vehicles, establishes a biomechanical model of the human spine, and establishes the relationship between vertical impact loads and human injuries. Subsequently, a C-shaped energy-absorbing cushioning structure is designed for application at the bottom support of the seat. Using a peak value of 50 g explosion-simulated triangular wave loading, the study compares the attenuation effects of different structural characteristics of cushioning energy-absorbing structures on impact loads. The results indicate that a 50 g peak vertical impact load can cause significant human injuries. The designed energy-absorbing cushioning structure can greatly reduce human response, but both excessively soft and rigid energy-absorbing cushioning structures fail to achieve effective impact attenuation.

Electronic Delocalization Engineering of β‐AsP Enabled High‐Efficient Multisource Logic Nanodevices

AbstractDelocalized electron and phonon structures are directives for rationally tuning the intrinsic physicochemical properties of 2D materials by redistributing electronic density. However, it is still challenging to accurately manipulate the delocalized electron and systematically study the relationships between physiochemical properties and practical nanodevices. Herein, the effects of delocalized electrons engineering on blue‐arsenic‐phosphorus (β‐AsP)‐based practical devices are systematically investigated via implementing vacancies or heteroatom doping. A tendency of carrier conductivity property from “half‐metal” to “metal” is initially found when tuning the electronic structure of β‐AsP with adjustable vacancy concentrations below 2 at% or above 3 at%, which can be ascribed to the introduction of delocalized electrons that cause asymmetric contributions to the electronic states near the implementation site. In optical logic device simulations, broadband response, triangular wave circuit system signal, and reverse polarization anisotropy are achieved by adjusting the vacancy concentration, while extinction ratios are as high as 1561. The electric and thermic‐logic devices realize the highest available reported giant magnetoresistance (MR) up to 1013% and 1039% at vacancy concentrations of 1.67% and 0.89%, respectively, which is significantly superior to the reports. The results shed light on the electronic delocalization strategy of regulating internal structures to achieve highly efficient nanodevices.

Feature-invariant processing of spatial segregation based on temporal asynchrony.

Temporal asynchrony is a cue for the perceptual segregation of spatial regions. Past research found attribute invariance of this phenomenon such that asynchrony induces perceptual segmentation regardless of the changing attribute type, and it does so even when asynchrony occurs between different attributes. To test the generality of this finding and obtain insights into the underlying computational mechanism, we compared the segmentation performance for changes in luminance, color, motion direction, and their combinations. Our task was to detect the target quadrant in which a periodic alternation in attribute was phase-delayed compared to the remaining quadrants. When stimulus elements made a square-wave attribute change, target detection was not clearly attribute invariant, being more difficult for motion direction change than for luminance or color changes and nearly impossible for the combination of motion direction and luminance or color. We suspect that waveform mismatch might cause anomalous behavior of motion direction since a square-wave change in motion direction is a triangular-wave change in the spatial phase (i.e., a second-order change in the direction of the spatial phase change). In agreement with this idea, we found that the segregation performance was strongly affected by the waveform type (square wave, triangular wave, or their combination), and when this factor was controlled, the performance was nearly, though not perfectly, invariant against attribute type. The results were discussed with a model in which different visual attributes share a common asynchrony-based segmentation mechanism.

Development of 3D printed tissue-mimicking materials: Combining fiber reinforcement and fluid content for improved surgical rehearsal

The prevalence of medical errors during surgical procedures has led to a higher emphasis on improving surgical outcomes, by improving surgical planning and training. Anatomical models have become valuable tools for pre-operative planning and current 3D printed models strive to better match real soft biological tissues. This study aimed to develop novel 3D printed material composites with controllable mechanical properties that mimic soft tissue. Concepts of microstructuring, fiber reinforcement and fluid infill in extrusion-based 3D printing are combined to design tunable materials towards target tissues of porcine muscle and liver. Material characterization was performed in triangular wave cyclic experiments under uniaxial tension with increasing displacements. Hereby, initial EI and final EII elastic moduli were evaluated. Further, the viscous response was characterized by the dissipated energy ratio UD and suture retention strength (SRS) was determined by single tensile pull-out tests Elastic moduli of printed materials were successfully tuned to 510 ± 10 kPa, closely resembling porcine muscle with 580 ± 150 kPa. The dissipated energy ratio UD of the silicone was increased from 0.09 ± 0.01 to 0.46 ± 0.17 by addition of gyroid infill and viscous fluid. Suture retention strength (SRS) for porcine liver tissue was 1.64 ± 0.42 N, while that of 3D printed silicone showed a mean SRS of 5.1 ± 0.6 N. Although the exact properties of porcine muscle and liver tissue require finer tuning, this study established techniques for refinement of 3D printed tissue-mimicking materials, ultimately enabling more accurate models for surgical rehearsal.

Robust low-noise 795-nm single-frequency fiber laser with continuous frequency tuning

This study presents a highly efficient and low-noise all-fiber single-frequency (SF) 795-nm laser system realized using a simple and robust single-pass frequency-doubling configuration. The foundation of the system is a 1590-nm erbium-doped fiber amplifier operating in a master oscillator power amplifier configuration seeded by a distributed feedback semiconductor laser at 1590.52 nm. The main amplifier exhibits an exceptional amplification efficiency of 30.5 %. By utilizing a periodically poled lithium niobate waveguide, the 795-nm laser is frequency-doubled with an output power reaching 2.3 W, corresponding to an optical efficiency of 44 % of the fundamental laser. Crucial to its application in precision measurements and quantum technologies, the SF 795-nm laser exhibits a relative intensity noise close to −150 dBc/Hz in the frequency range of 0.1 to 10 MHz. Additionally, a continuous frequency-tuning range of 11.7 GHz is achieved by modulating the current with a 2.5-mA 1-Hz triangular wave. Notably, this is the first report on an all-fiber SF 795-nm laser system.