Amplitude Errors Research Articles

Seismic performance evaluation of a five-story column-and-beam glulam frame with steel-timber buckling restrained braces

This paper summarizes the results of numerical simulation and fragility analysis of a five-story column-and-beam glulam frame with chevron steel-timber buckling restrained braces (BRBs). Key parameters of the rotational behavior of the bolted beam-to-column connections and column base connections were modeled and calibrated using shaking table test results. Prediction methods of the stiffness and capacity of the steel-timber BRBs were proposed and validated with the test results. An FEM model of the glulam frame with steel-timber BRBs was developed to capture the frame seismic response and validated using shaking table test results. The FEM model which considered damping change and damage accumulation achieved good agreement with shaking table test results, with the modelling errors of displacement amplitude for most conditions less than 15 %. Fragility analysis of the frame was conducted based on the validated FEM model. The probability of exceeding the collapse prevention limit state under the VII-rare earthquake excitations was reduced to close to zero when steel-timber BRBs were used. This study demonstrates the potential for using glulam frames with steel-timber BRBs in Chinese VII seismic regions.

Bayesian deep neural networks for spatio-temporal probabilistic optimal power flow with multi-source renewable energy

Probabilistic optimal power flow (POPF) plays a crucial role in ensuring the economic and secure operation of power systems with multiple fluctuating loads and renewable energy power generations. However, the practical application of POPF faces challenges because of the lack of accurate input scenarios and the heavy computational burden. With the increasing power system uncertainties and frequent changes in topologies, the existing POPF analysis methods struggle to achieve both high precision and efficient training. To address these issues, firstly, this work decomposes the POPF into three stages: 1) the generation of source-load random scenarios; 2) the non-linear mapping derived from the Karush-Kuhn-Tucker conditions; and 3) the non-linear mapping derived from the power flow equations. Secondly, this work proposes two Bayesian deep neural networks to separately solve each stage of the POPF. Multi-collinearity reduction conditional variational autoencoder can generate source-load random scenarios while consistency condition guided Bayesian deep neural network can predict POPF calculation results. The work further conducts numerical simulations on four IEEE benchmark power systems with multiple renewable energy sources, using uncertainty data collected from the Belgian wind power generation, photovoltaic power generation and load dataset. The simulation results demonstrate that: 1) the precision in generating source-load random scenarios has been enhanced, leading to a reduction of up to 128% in the distribution statistical quantities of the accuracy measures; and 2) the mean absolute error of active power injections, and voltage angles as well as the mean absolute percentage error of the voltage amplitudes in the benchmark systems are reduced by at least 0.7% compared to deterministic neural networks.

Non-contact voltage measurement of residential cables based on internal parameter conversion and centering probe assistance

Existing non-contact voltage measurement technology cannot be applied to residential cables containing neutral wire and earth wire in addition to live wire. A non-contact voltage measurement method of residential cables is introduced in this article. First, an equivalent circuit model of the residential cable measurement based on capacitive coupling is established. In order to solve the problem of uncertain coupling capacitance, which leading to the inability to accurately obtain the voltage amplitude, a calibration method based on internal parameter conversion and centering probe assistance is proposed. This method calibrates the cable voltage through different transfer relationships and sensor outputs, and no known reference excitation is required during calibration. Subsequently, the impact of internal parameters on measurement accuracy are analyzed and selection principles are provided. Through finite element simulation, the influence of metal spring for centering on voltage measurement is analyzed, and the measurement error of non-ideal cables (with eccentricity or ovality) is quantified. A prototype probe and internal parameter conversion circuit have been developed, and parasitic capacitance compensation have been completed. The measurement accuracy of 50 Hz voltage in a certain range (100–300 V) was tested in the laboratory, the maximum relative error of amplitude is −0.89%, and the relative error of phase is 0.68%. Four specifications of residential cables testing were completed, with a maximum relative error of −1.35%. Long- term testing was conducted on the actual field (output voltage of the distribution box), the test results showed that the output was linear, and the relative error were kept around 0.65% after primary calibration.

Direction-of-arrival estimation for a nested array with gain-phase error and impulse noise

To solve direction-finding problems for nested arrays under conditions of impulse noise and gain–phase errors, this paper proposes a direction-of-arrival (DOA) estimation method. First, a correntropy with an adaptive kernel length combined with an infinite norm of a variable weight value is proposed to suppress impulse noise. Then, the auxiliary array elements are used to realize the initial calibration of the amplitude and phase errors. On this basis, a DOA estimation method without a spectral peak search is proposed; this method is robust for arrays that still have residual gain–phase errors after calibration. Our method overcomes the difficulties of DOA estimation for nested arrays under conditions of gain–phase errors and impulse noise. Compared with traditional methods, the proposed method does not require prior knowledge, does not require a spectral peak search and has high superiority and robustness; a series of experiments have verified its superiority. In addition, a Cramér‒Rao bound (CRB) for angle estimation under conditions of gain–phase errors and impulse noise is proposed in this paper.

An adaptive time stepping stiffness confinement method for solving reactor dynamics equations

The stiffness confinement method (SCM) is frequently employed to solve the reactor dynamics equations because it confines the stiffness of the problem by frequency transformation. However, the balance between the error and efficiency of the SCM has not been well studied. This paper reports the error analysis of the SCM. The error by SCM is derived mathematically and written as integral error, driven by the integral of the frequency interpolation function. An easy-to-implement adaptive time-stepping (ATS) algorithm is proposed based on the error analysis by controlling the neutron flux amplitude error. First, a fine-step PKE is leveraged to estimate the second-order derivative of the flux amplitude-frequency, which is used to predict the error of the neutron flux amplitude. The low cost of solving the PKE incurs a negligible effect on the algorithm’s efficiency. Second, based on the error analysis, an error estimator proposed to determine an optimal time-step size for the neutron temporal-spatial equation. With a pre-set error tolerance, the ATS algorithm is exempted from the empirical selection of the time-step size in transient simulations. Numerical tests with TWIGL and modified 2D LMW benchmark problems show that the optimal time-step size effectively confines the local truncation error of the flux amplitude within the pre-set tolerance. The ATS algorithm yields a higher accuracy at a commensurate computational cost than calculations with fixed time-steps.

Quasistatic deflection analysis of slender ball-end milling cutter

In this study, a quasistatic force-deflection interaction model considering cutting and elastic force was proposed to analyze and compensate for the quasistatic deflection of slender ball-end milling cutter. The theoretical waveforms and peaks of cutting force considering the force-deflection interactions were consistent with the experimental results. The deflection of slender ball-end milling cutter significantly reduces the cutting force, and the Pearson's correlation coefficient between the difference in the peak cutting force and maximum deflection in radial is larger than that of in feed directions. An analysis of the machining error of a cylindrical surface revealed that the deflection of slender ball-end milling cutter had a considerable effect on the machining error, and the compensation of slender cutter deflection effectively reduced the amplitude and fluctuation of the machining error. This work can provide a useful guidance for machining error control in the ball-end milling process of mold surfaces with deep cavities.

High-resolution acoustic beamforming based on genetic algorithms

A beamforming technique based on the genetic algorithm is proposed in this paper. This method reconstructs acoustic sources by exploiting the sparsity. To reduce the computational cost and speed up the implementation, a highly efficient algorithm is further developed by narrowing down the search domain for the genetic algorithm. The performance is numerically investigated through a quantitative analysis of the position and amplitude error of the recovered source, and experimentally demonstrated in acoustic imaging. For this newly established approach, the results indicate a higher resolution capability than the conventional beamforming, and better accuracy and robustness than the compressive sensing beamforming. Overall, the present work can enrich existing high-resolution beamforming methods and benefit relevant acoustic testing applications.

Исследование амплитудной и фазовой ошибок датчика-опоры при ультразвуковой сварке пластмасс

The paper presents a technique making it possible to evaluate amplitude and phase errors of the magnetoelastic support sensor used in the plastics ultrasonic welding. Measurement of the support sensor vibration amplitude allows monitoring alterations in the basic physical properties of the polymer being welded, i.e. its temperature and thickness. The support sensor operation dynamic mode is described. It is established that evaluating measurement errors with the proposed method in manufacture of any support sensor of different design makes it possible to accurately determine its performance with parameters of the polymer material ultrasonic welding process. The problem of evaluating accuracy of the magnetoelastic support sensor operation used in the welding process was considered. The support sensor amplitude and phase errors during ultrasonic welding were studied. A magnetoelastic sensor was designed and developed ensuring improved accuracy in measuring the support vibrations amplitude during the polymer material ultrasonic welding. The experiments carried out confirmed clear relationship between the support vibrations amplitude and heating of the welded samples, their thickness and properties during the ultrasonic welding.

A 29–31-GHz, 0.4-dB Amplitude Error and 1° Phase Error Beamforming IC and 20-dB Dynamic Range Power Detector for SatCom Phased Arrays

A 29–31-GHz, 0.4-dB Amplitude Error and 1° Phase Error Beamforming IC and 20-dB Dynamic Range Power Detector for SatCom Phased Arrays

Multivariate Time Series Prediction Based on Temporal Change Information Learning Method.

In the multivariate time series prediction tasks, the impact information of all nonpredictive time series on the predictive target series is difficult to be extracted at different time stages. Through the emphasis on optimal-related sequences in the target series, the deep learning model with the attention mechanism achieves a good predictive performance. However, temporal change information in the objective function and optimization algorithm is completely ignored in these models. To this end, a temporal change information learning (CIL) method is proposed in this article. First, mean absolute error (MAE) and mean squared error (MSE) losses are contained in the objective function to evaluate different amplitude errors. Meanwhile, the second-order difference technology is used in the correlation terms of the objective function to adaptively capture the impact of the abrupt and slow change information in each series on the target series. Second, the long short-term memory (LSTM) network with the transformation mechanism is used in the method so that temporal dependence information can be fully extracted (i.e., avoiding the supersaturation region). Third, to effectively obtain the optimal model parameters, the current and historical moment estimation information is adaptively memorized without the introduction of additional hyperparameters, and therefore, the acquisition ability of temporal change information in the error gradient flow is greatly enhanced by the proposed optimization algorithm. Finally, three datasets with different scales are used to verify the advantages of the CIL method in computational overhead and prediction effect.

Respiratory Motion Compensation Using Xsight Diaphragm Tracking for Liver Tumor in CK Synchrony Treatment: A Feasibility Study

This study investigates the feasibility of using Xsight Diaphragm Tracking (XDT) for liver tumors located near or in the diaphragm during CyberKnife Synchrony Treatment. Eight patients (46 fractions) with liver tumors located near or in the diaphragm were reviewed retrospectively. Prior to motion data analysis, baselines were flattened to remove the portions with significant changes and improve accuracy. To reduce the uncertainty about sudden irregular breathing, respiratory data were calculated as a rolling average. The overall tracking accuracy based on the patient-specific respiratory curve was evaluated using E2E testing with CIRS (18023-A) dynamic phantom. Three main trajectories were observed in this work: Linearity (1/8), Linear radial type (6/8) and Hysteresis (1/1). The mean amplitude was 8.56±4.54 mm, 2.77±2.83 mm, and 4.23±3.92 mm for S-I, L-R, and A-P components. The linear trajectory patient had a more concentrated amplitude distribution. The baseline shifts were 5.88 mm (S-I), 2.53 mm (L-R), and 3.48 mm (A-P). Except for patient 2, all standard deviations of the center phase shift were less than 1 mm. The values of XDT correlation and prediction errors were 1.38±0.65 mm vs. 0.65±0.16 mm (S-I), 1.28±0.48 mm vs. 0.34±0.10 mm (L-R), and 0.96±0.32 mm vs. 0.22±0.072 mm (A-P), respectively. The strong positive correlations were amplitude vs. prediction error, SD of center phase vs. prediction error, and SD of center phase vs. amplitude. The median patient curve-based targeting accuracy was less than 1mm. Additionally, the mean target coverage for all patients with a 3 mm margin was 98.03±1.54%. This study proved that the diaphragm could be used as a tracking surrogate for liver tumors located in or near the diaphragm instead of placing golden fiducial markers. A reduction in motion amplitude and respiration training were necessary during liver SABR treatment, along with respiration control and evaluation.

An ease-off tooth surface redesign for spiral bevel gears considering misalignment under actual working conditions

To improve the loaded performance of spiral bevel gears, a novel tooth surface redesign method considering misalignment is proposed based on ease-off. First, the digital features of the contact pattern were extracted, and the equivalent misalignment was obtained by an optimal method according to the minimum deviation of the contact path. Second, a pinion target surface whose performance under misalignment was consistent with the original gear in standard position was built, and a pinion surface with good meshing performance under misalignment was redesigned with equivalent misalignment. Third, the flank modification was carried out to cut down on the loaded transmission error of gear under misalignment. Through simulations, it is found the transmission error and the contact path of redesign gear considering misalignment were the same as original gear in standard position. The loaded transmission error amplitude of original gear under misalignment was 43.91% higher than original gear in standard position, and the loaded transmission error amplitude of redesign gear after optimization under misalignment was 44.73% lower than original gear in standard position and 61.60% lower than original gear under misalignment. The tooth surface stress of redesigned gear after optimization under misalignment was also significantly improved. This proposed redesign method, which considers misalignment on the basis of ease-off, can greatly improve the loaded meshing quality of gear under actual working conditions.

Amplitude Control Loop to Compensate for I/Q Mismatch in an Accurate Quadrature LC Oscillator

In this paper, a novel parallel-coupled quadrature LC oscillator (PC-QO) is presented that can automatically eliminate imbalances of output phase and amplitude resulting from mismatches in the LC tanks. The method of using unequal coupling factors in a parallel-coupled quadrature oscillator is the base of this design; canceling the phase and amplitude errors takes place by tuning the imbalanced coupling factor using tuneable tail currents. First, the proposed circuit senses the amplitude error and then adjusts the coupling factors according to the situation. We show that using the inversely proportional coupling factors can eliminate the phase and amplitude error simultaneously. In other words, this design uses the amplitude control loop to cancel the phase and amplitude error. The circuit has been simulated using TSMC 0.18 CMOS practical model to confirm the high accuracy of the analysis and capability of the canceling [Formula: see text]/[Formula: see text] mismatch technique. The simulation results show that the phase noise of the proposed quadrature voltage controlled oscillator (QVCO) is −123.9 dBc/Hz at 1[Formula: see text]MHz offset from 4.4[Formula: see text]GHz operation frequency. The total power consumption of the QVCO is 3.4[Formula: see text]mW.

Dynamic Analysis of Non-Uniform Functionally Graded Beams on Inhomogeneous Foundations Subjected to Moving Distributed Loads

Inhomogeneous materials, variable foundations, non-uniform cross-sections, and non-uniformly distributed loads are common in engineering structures and typically complicate their mechanical analysis considerably. This paper presents an accurate and efficient numerical method for the dynamic analysis of non-uniform functionally graded beams resting on inhomogeneous viscoelastic foundations subjected to non-uniformly distributed moving load and investigates the effects of non-uniformities and inhomogeneities on material, foundation, and load. Based on the Timoshenko beam theory and a Chebyshev spectral method, a consistent discrete dynamic model is derived, which can deal with all axially varying properties. A series of numerical experiments are carried out to validate the convergence and accuracy of the proposed method. The results are compared with those obtained through finite element analysis or in the literature, and excellent agreement is observed. Then, the dynamic response of an axially functionally graded beam resting on an inhomogeneous viscoelastic foundation and subjected to a non-uniformly distributed moving load is investigated. The results show that the material gradient and the inhomogeneous foundation can alter the vibration amplitudes and critical speeds of the beam significantly. Compared with more realistic non-uniformly distributed moving load models, idealized concentrated and uniformly distributed moving load models produce apparent computation errors in vibration amplitudes.

Investigating the technical feasibility of magnetoencephalography during transcranial direct current stimulation.

Magnetoencephalography (MEG) can measure weak magnetic fields produced by electrical brain activity. Transcranial direct current stimulation (tDCS) can affect such brain activities. The concurrent application of both, however, is challenging because tDCS presents artifacts on the MEG signal. If brain activity during tDCS can be elucidated by MEG, mechanisms of plasticity-inducing and other effects of tDCS would be more comprehensively understood. We tested the technical feasibility of MEG during tDCS using a phantom that produces an artificial current dipole simulating focal brain activity. An earlier study investigated estimation of a single oscillating phantom dipole during tDCS, and we systematically tested multiple dipole locations with a different MEG device. A phantom provided by the manufacturer was used to produce current dipoles from 32 locations. For the 32 dipoles, MEG was recorded with and without tDCS. Temporally extended signal space separation (tSSS) was applied for artifact rejection. Current dipole sources were estimated as equivalent current dipoles (ECDs). The ECD modeling quality was assessed using localization error, amplitude error, and goodness of fit (GOF). The ECD modeling performance with and without tDCS, and with and without tSSS was assessed. Mean localization errors of the 32 dipoles were 1.70 ± 0.72 mm (tDCS off, tSSS off, mean ± standard deviation), 6.13 ± 3.32 mm (tDCS on, tSSS off), 1.78 ± 0.83 mm (tDCS off, tSSS on), and 5.73 ± 1.60 mm (tDCS on, tSSS on). Mean GOF findings were, respectively, 92.3, 87.4, 97.5, and 96.7%. Modeling was affected by tDCS and restored by tSSS, but improvement of the localization error was marginal, even with tSSS. Also, the quality was dependent on the dipole location. Concurrent tDCS-MEG recording is feasible, especially when tSSS is applied for artifact rejection and when the assumed location of the source of activity is favorable for modeling. More technical studies must be conducted to confirm its feasibility with different source modeling methods and stimulation protocols. Recovery of single-trial activity under tDCS warrants further research.

A Numerical Gear Rolling Test Method for Face-Hobbed Hypoid Gears

A numerical gear rolling test (NGRT) method for actual tooth surfaces was proposed. The non-uniform rational B-spline (NURBS) fitting method was adapted to reconstruct the actual tooth surface, and the instant meshing point as well as the transmission error of two meshing gears were solved. The instant contact ellipse boundary of each meshing point can be accurately searched, and then the contact pattern formed by a series of contact ellipses on the actual tooth surface can be obtained. Finally, the rolling test experiment for a pair of hypoid gears was conducted to verify the feasibility of the proposed method. The result shows that the contact pattern obtained is consistent with the actual rolling test result, the relative errors of the transmission error amplitudes were only 4.5% and 5.3% for the drive and coast sides, respectively, and the contact ellipse of the actual tooth surface is not necessarily a standard ellipse and the instant contact path is not necessarily a straight line. This NGRT method helps to reduce equipment and time costs in closed-loop gear manufacturing, which is of great significance for mass production.

Leader-follower formation control of Euler-Lagrange systems with limited field-of-view and saturating actuators: A case study for tractor-trailer wheeled mobile robots

In this paper, an adaptive-neural constrained controller is proposed for a group of Tractor-trailer wheeled mobile robots with limited field-of-view (FOV) constraints and saturating actuators. With an effective combination of the asymmetric Barrier Lyapunov function based control design and dynamic surface control in the proposed constrained controller, the limited FOV constraints are not transgressed the predefined and limited bounds. The risk of the actuators saturation is extremely decreased through restricting amplitudes of the output states errors. It is proved that all the output states in the closed-loop system are semi-globally uniformly ultimately bounded and the relative distance and orientation angles errors are converged in the limited and preassigned boundaries. Compared with the existing results, the proposed constrained controller not only assures that these states errors between consecutive TTWMRs are bounded, but also all the output states errors converge to a small region around zero in a fixed-time that this issue accelerates the convergence speed rate and improves the transient response performance of the perfect tracking control for all TTWMRs.

Parameter identification method of nonuniform and under-sampled blade tip timing based on extended DFT and compressed sensing

Vibration amplitude and frequency are the two most important indicators that characterize the health status of high-speed rotating blades, but the signal obtained by blade tip timing (BTT) technology, one of the best rotating blade vibration monitoring methods, is seriously nonuniform and under-sampled, which makes these two indicators difficult to identify. In view of this problem, the paper proposes a parameter identification method for the nonuniform and under-sampled BTT signal based on extended Discrete Fourier transform and compressed sensing (CS), with the Fourier integral transformation as the goal. It realizes the frequency analysis of nonuniform under-sampled signals by constructing and optimizing the transformation basis function instead of the exponential basis in the traditional FFT transformation in the extended frequency range, and then constructs a CS model through the obtained blade vibration frequency. The complete waveform of the blade vibration is restored by using a small number of under-sampled signals, thus obtaining the blade vibration amplitude and vibration frequency. On the one hand, the method proposed in this paper breaks through the limitation of Nyquist’s sampling theorem, and the number of analytical spectral lines is no longer limited to the number of sampling points, which improves the frequency resolution. On the other hand, only a small number of measurement signals can be reconstructed to achieve a complete vibration signal. The feasibility and reliability of the proposed method are verified by mathematical modeling, simulation analysis, and experimental testing. The results indicate that when the number of sensors is greater than or equal to four, the time domain and frequency domain signals of blade vibration can be accurately analyzed based on the proposed method, the vibration amplitude error is less than 0.01 mm, the frequency error is less than 0.1 Hz, and it has good anti-interference performance.

A DC-87.8-GHz Switched-Type Attenuator With Switched Capacitor Branch in 40-nm CMOS

This paper presents a 5-bit switched-type attenuator (STA) working from DC to 87.8 GHz. In addition to T-type and Π-type attenuation cells with capacitive compensation technique in shunt branch, a new Π-type-based compensation method with switched capacitor branch is proposed, which effectively reduces phase errors at high frequencies without compromising the amplitude errors. The STA in this work is fabricated in 40-nm CMOS technology and the active core area is 0.019 mm, which demonstrates 15.5-dB attenuation range with 0.5-dB tuning step. Across the operational band, the insertion loss of reference state is 1.4-5.3 dB and the return loss is better than 9 dB for all states. From DC to 87.8 GHz, the RMS amplitude and phase errors are below 0.5 dB and 5.4∘ respectively.

A novel method for studying fluid-solid interaction problems of the rotor system in air bearings with manufacturing errors

A novel method for studying fluid–solid interaction problems of the rotor system in air bearings is proposed. The overall transfer equation of the rotor system is established based on the new version of transfer matrix method for multibody systems (NV-MSTMM), coupling with the extended transient Reynold equation, which achieves the two-way fluid–solid interaction analysis of the rotor system. The transfer matrix of the spatial flexible Timoshenko beam is first derived based on NV-MSTMM. The accuracy of the proposed approach is verified by an experiment and published literature. The influence of manufacturing errors including roundness, convexity, concavity and tapers on the dynamic performance of the rotor system is investigated comprehensively. The results show that the types and amplitude of manufacturing errors have complex effects on dynamic performance. Roundness with spatial numbers of 3 to 6, concavity and taper1 errors decrease the error motion amplitude, while convexity and taper2 errors increase it. Especially, roundness errors with spatial numbers of 1 and 2 notably increase the error motion amplitude, which should be avoided strictly.