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Reservoir computing (RC) is a potential neuromorphic paradigm for physically realizing artificial intelligence systems in the Internet of Things society, owing to its well-known low training cost and compatibility with nonlinear devices. Micro-electro-mechanical system (MEMS) resonators exhibiting rich nonlinear dynamics and fading behaviors are promising candidates for high-performance hardware RC. Previously, we presented a non-delay-based RC using one single micromechanical resonator with hybrid nonlinear dynamics. Here, we innovatively introduce a nonlinear tuning strategy to analyze the computing properties (the processing speed and recognition accuracy) of the presented RC. Meanwhile, we numerically and experimentally analyze the influence of the hybrid nonlinear dynamics using the image classification task. Specifically, we study the transient nonlinear saturation phenomenon by fitting quality factors under different vacuums, as well as searching the optimal operating point (the edge of chaos) by the static bifurcation analysis and dynamic vibration numerical models of the Duffing nonlinearity. Our results in the optimal operation conditions experimentally achieved a high classification accuracy of (93 ± 1)% and several times faster than previous work on the handwritten digits recognition benchmark, profit from the perfect high signal-to-noise ratios (quality factor) and the nonlinearity of the dynamical variables. [ABSTRACT FROM AUTHOR]

An ion beam etching system with etching endpoint detection (EPD) capability based on optical emission spectroscopy (OES) was conceived, built, and tested. An expansion chamber was added on the right side of the etching chamber to fix the optical detector for in-situ detecting. In this system, the optical detector was mounted on a seven-shaped bracket, which was fixed by two straight guides, thus the position of the optical detector could be adjusted arbitrarily to collect the emission spectrum generated by the sample during the etching process. The signal was transmitted by optical fiber to the computer for processing, and the etching endpoint could be detected after analyzing the data. Firstly, we used simple substances (Al, Cr, Si, and Mg) to analyze the feasibility of the system and determine the best position of the optical detector. In addition, we also tested the detection limit of the system. Finally, a complex multilayer film sample with different materials was tested, and the results showed that the system could clearly detect the characteristic emission lines of different layers and had a good real-time performance and excellent endpoint detection capabilities. [ABSTRACT FROM AUTHOR]

In this paper, performance of PECVD SiO/SiN double layers electrets with different thicknesses were investigated detailedly in respect of chargeability, storage charge stability in high temperature and reliability in high humidity environment. Samples with different thicknesses of SiN and SiO were prepared on Pyrex 7740 glass substrates and characterized by isothermal and high humidity charge decay. The results of experiment approved that the PECVD SiO/SiN double layers electrets on glass substrate has as good chargeability and charge stability in high temperature and high humidity environment as thermal oxidation or APCVD/LPCVD ones on silicon substrates. The experiment results indicated that a SiN layer no less than 50 nm is necessary for good charge stability in high temperature and a SiN layer thicker than 500 nm decreases the chargeability. Even a 2 nm SiN layer is enough to significantly improve the charge stability in high humidity environment. Thick SiO layer can increase the surface potential of electrets under the same charging condition and its charge stability in high temperature. However, the electrets with high surface potential also exhibit poor uniformity of charge stability in high humidity environment. [ABSTRACT FROM AUTHOR]

Resonant accelerometers are promising because of their wide dynamic range and long-term stability. With quasi-digital frequency output, the outputs of resonant accelerometers are less vulnerable to the noise from circuits and ambience. Differential structure is usually adopted in a resonant accelerometer to achieve higher sensitivity to acceleration and to reduce common noise at the same time. Ideally, a resonant accelerometer is only sensitive to external acceleration. However, temperature has a great impact on resonant accelerometers, causing unexcepted frequency drift. In order to cancel out the frequency drift caused by temperature change, an improved temperature compensation method for differential vibrating accelerometers without additional temperature sensors is presented in this paper. Experiment results demonstrate that the temperature sensitivity of the prototype sensor is reduced from 43.16 ppm/°C to 0.83 ppm/°C within the temperature range of −10 °C to 70 °C using the proposed method. [ABSTRACT FROM AUTHOR]

Reservoir computing (RC) is an attractive paradigm of a recurrent neural network (RNN) architecture, owning to the ease of training and existing neuromorphic implementation. Its simulated performance matches other digital algorithms on a series of benchmarking tasks, such as prediction tasks and classification tasks. In this article, we propose a novel RC structure based on the coupled MEMS resonators with the enhanced dynamic richness to optimize the performance of the RC system both on the system level and data set level. Moreover, we first put forward that the dynamic richness of RC comprises linear dynamic richness and nonlinear dynamic richness, which can be enhanced by adding delayed feedbacks and nonlinear nodes, respectively. In order to set forth this point, we compare three typical RC structures, a single-nonlinearity RC structure with single-feedback, a single-nonlinearity RC structure with double-feedbacks, and the couple-nonlinearity RC structure with double-feedbacks. Specifically, four different tasks are enumerated to verify the performance of the three RC structures, and the results show the enhanced dynamic richness by adding delayed feedbacks and nonlinear nodes. These results prove that coupled MEMS resonators offer an interesting platform to implement a complex computing paradigm leveraging their rich dynamical features. [ABSTRACT FROM AUTHOR]

The emergence of Automated Guided Vehicle (AGV) has greatly increased the efficiency of the transportation industry, which put forward the urgent requirement for the accuracy and ease of use of 2D planar motion robot positioning. Multi-sensor fusion positioning has gradually become an important technical route to improve overall efficiency when dealing with AGV positioning. As a sensor directly acquiring depth, the RGB-D camera has received extensive attention in indoor positioning in recent years, while wheel odometry is the sensor that comes with most two-dimensional planar motion robots, and its parameters will not change over time. Both the RGB-D camera and the wheel odometry are commonly used sensors for indoor robot positioning, but the existing research on the fusion of RGB-D and wheel odometry is limited based on classic filtering algorithms; few fusion solutions based on optimization algorithm of them are available at present. To ensure the practicability and greatly improve the accuracy of RGB-D and odometry fusion positioning scheme, this paper proposed a tightly-coupled positioning scheme of online calibrated RGB-D camera and wheel odometry based on SE(2) plane constraints. Experiments have proved that the angle accuracy of the extrinsic parameter in the calibration part is less than 0.5 degrees, and the displacement of the extrinsic parameter reaches the millimeter level. The field-test positioning accuracy of the positioning system we proposed having reached centimeter-level on the dataset without pre-calibration, which is better than ORB-SLAM2 relying solely on RGB-D cameras. The experimental results verify the excellent performance of the frame in positioning accuracy and ease of use and prove that it can be a potential promising technical solution in the field of two-dimensional AGV positioning. [ABSTRACT FROM AUTHOR]

Wind turbines (WTs) are prone to lose the synchronization during severe grid faults due to the absence of equilibrium point. To cope with the issue, this letter proposes a power compensation control for doubly fed induction generator based WT to enhance the transient synchronization stability from the new perspective of active power balance. In the method, the active power of WT is controlled to compensate the power loss on the network. Compared with the existing methods, the proposed method has more widely application scenarios because it avoids using the frequency error as control signal. Experimental tests are performed to validate proposed method. [ABSTRACT FROM AUTHOR]

The piezoelectric cantilever resonator is used widely in many fields because of its perfect design, easy-to-control process, easy integration with the integrated circuit. The tip displacement and resonance frequency are two important characters of the piezoelectric cantilever resonator and many models are used to characterize them. However, these models are only suitable for the piezoelectric cantilever with the same width layers. To accurately characterize the piezoelectric cantilever resonators with different width layers, a novel model is proposed for predicting the tip displacement and resonance frequency. The results show that the model is in good agreement with the finite element method (FEM) simulation and experiment measurements, the tip displacement error is no more than 6%, the errors of the first, second, and third-order resonance frequency between theoretical values and measured results are 1.63%, 1.18%, and 0.51%, respectively. Finally, a discussion of the tip displacement of the piezoelectric cantilever resonator when the second layer is null, electrode, or silicon oxide (SiO2) is presented, and the utility of the model as a design tool for specifying the tip displacement and resonance frequency is demonstrated. Furthermore, this model can also be extended to characterize the piezoelectric cantilever with n-layer film or piezoelectric doubly clamped beam. [ABSTRACT FROM AUTHOR]

• The essential requirements for zero-error tracking of current loop are revealed. • The relationship between the post-fault current reference and EMF under various LVRT control strategies is obtained. • A disturbance feedforward control is proposed to accurately realize the transient control targets during LVRT. The existing low voltage ride-through (LVRT) control strategies usually modify the post-fault current reference to contain some transient and negative-sequence components, to achieve the controllable LVRT operating of type-3 wind turbine (WT) under severe grid fault. However, the modified current reference and post-fault electromotive force (EMF) disturbance behave as the multi-frequency (i.e., 0-, 50- and 100-Hz) components in the synchronous dq -frame, thus the classic PI controller-based current control cannot provide zero-error tracking of the aforesaid reference, and leading to the inaccurate implementation of transient control targets. To solve this problem, based on the relationship between the modified current reference and post-fault EMF, an improved disturbance feedforward control is proposed to simultaneously suppress EMF disturbance and improve the tracking capability of modified current reference. As a result, the transient control targets of the improved LVRT control strategies can be implemented accurately. Moreover, the method is easy to implement. Finally, the proposed method is verified by the simulations on a 1.5-MW type-3 WT. [ABSTRACT FROM AUTHOR]

MEMS-based magnetoresistive (MR) sensors have attracted considerable attention for years due to their small weight, low power consumption, and high sensitivity, whereas the 1/ $f$ noise is larger in the low-frequency region and degrades the low-frequency magnetic field detection limit. To reduce the impact of 1/ $f$ noise, MEMS resonators are utilized to modulate the low-frequency field to a high-frequency region where the 1/ $f$ noise vanishes. This article proposes a novel modulation method called synchronous motion modulation (SMM) using a comb-driven resonator and a piezoelectric cantilever resonator; meanwhile, it analyzes the relationship of modulation efficiency of SMM, vertical motion modulation (VMM), and gap change modulation (GCM) theoretically and with finite element method (FEM) simulation. It is found that the theoretical analysis is coincident with numerical simulation, and the SMM is the optimal modulation method for improving the low-frequency magnetic field detection limit due to its modulation efficiency is the sum of that of VMM and GCM. [ABSTRACT FROM AUTHOR]

TGA transcription factors belong to Group D of the bZIP transcription factors family and play vital roles in the stress response of plants. Brassica napus is an oil crop with rich economic value. However, a systematic analysis of TGA gene family members in B. napus has not yet been reported. In this study, we identified 39 full-length TGA genes in B. napus, renamed TGA1~TGA39. Thirty-nine BnTGA genes were distributed on 18 chromosomes, mainly located in the nucleus, and differences were observed in their 3D structures. Phylogenetic analysis showed that 39 BnTGA genes could be divided into five groups. The BnTGA genes in the same group had similar structure and motif compositions, and all the BnTGA genes had the same conserved bZIP and DOG1 domains. Phylogenetic and synteny analysis showed that the BnTGA genes had a close genetic relationship with the TGA genes of the Brassica juncea, and BnTGA11 and BnTGA29 may play an important role in evolution. In addition, qRT-PCR revealed that three genes (BnTGA14/17/23) showed significant changes in eight experimental materials after drought treatment. Meanwhile, it can be inferred from the results of drought treatment on different varieties of rapeseed that the stress tolerance of parental rapeseed can be transmitted to the offspring through hybridization. In short, these findings have promoted the understanding of the B. napus TGA gene family and will contribute to future research aimed at B. napus resistant breeding. [ABSTRACT FROM AUTHOR]

A periodically corrugated metal metasurface can support spoof surface plasmon polaritons (SSPPs) at lower frequencies (e.g., terahertz (THz) and microwave ranges). In this paper, we explore a multi-bands SSPPs waveguide composed of a composite periodic metal groove (CPMG) and derive the theoretical dispersion formulas by the modal expansion method (MEM) under the deep subwavelength condition. The numerical experiments and analytical calculations are used to give a general analysis about the properties of the SSPPs on the composite periodic waveguides. It is demonstrated that the SSPPs waveguides of CPMG with multi-grooves in one period give better near-field confinement benefiting from the more electromagnetic (EM) hotspots at the surface of their periodic structure. Numerical simulations are employed to verify the theoretical analysis and demonstrate good agreement with the analytical results. The calculation methodology presented in this paper can be applied to address the miniaturization, compact design aspects of THz devices and highly sensitive trace sensing fields. [ABSTRACT FROM AUTHOR]

The system inertia is gradually decreasing and frequency security issues are becoming more prominent with the increasing penetration of wind power. To ensure the safety and stability of power system, many countries have updated their grid codes to reinforce the frequency regulation requirements (FRRs) for wind power plants (WPPs). However, most review articles on grid codes cover all grid-integration metrics, while the review of FRRs is inadequate and incomplete; moreover, it shall be updated to accommodate the state-of-the-art grid codes. To cope with it, this study presents a comprehensive review of FRRs for WPPs in modern grid codes, covering 12 representative countries or organizations such as those with the highest development level, the fastest development speed, and the largest installations in wind power. The FRRs in their grid codes for wind power integration are compared and analyzed from three aspects: frequency operating range, primary frequency response and inertia response. Based on the comparative analysis, combined with relevant policy documents, some future trends related to FRRs are concluded. Furthermore, electricity generation sources in each country are analyzed to enrich the understanding of the reasons behind the differences in FRRs. The review helps the transmission system operator to compare and analyze international grid codes and optimize their own grid codes. Moreover, it enables wind turbine manufacturers to master the latest grid codes and grasp the future trends, and helps research focus on practical needs and solve the pain points of wind power development. [Display omitted] • Frequency regulation requirements for wind power integration are reinforced. • A comprehensive comparison of 12 representative grid codes is presented. • Three key aspects in frequency regulation requirements are compared and analyzed. • Future trends related to frequency regulation requirements are concluded. [ABSTRACT FROM AUTHOR]

Magnetoresistive (MR) sensors have great application prospects in the field of weak magnetic field detection due to their high sensitivity, small size, and low power consumption. However, 1/f noise greatly limits the low-frequency detectivity of MR sensors. In order to suppress 1/f noise, this paper proposes a two-dimensional synchronous motion modulation (TDSMM) structure based on microelectromechanical systems (MEMS). This structure can effectively reduce 1/f noise by modulating the frequency of the measured magnetic field in the high-frequency band. Theoretical analysis and finite element simulation were conducted on three different modulation models: TSDMM, magnetic flux concentrators motion modulation, and MR components longitudinal motion modulation. The results showed that the modulation efficiency of the TDSMM reached as high as 127%, which is currently the highest value in MR-MEMS sensors. The TDSMM MEMS structure has been successfully manufactured, and the resonant frequency of the transverse resonator is twice that of the longitudinal resonator, enabling extremely high modulation efficiency. The noise spectral density of giant-magnetoresistive components on a silicon-on-insulator substrate was tested, and the noise level in the high-frequency band was three orders of magnitude lower than that in the low-frequency band. These results position MR-MEMS sensors with TDSMM structures as highly competitive candidates in the field of ultra-weak magnetic field detection. [ABSTRACT FROM AUTHOR]