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Abstract Face recognition systems have been widely applied in various scenarios in people's daily lives. The recognition rate and speed of face recognition systems have always been the two key technical factors that researchers focus on. Many excellent recognition algorithms achieve high recognition rates or good recognition speeds. However, more research is needed to develop algorithms that can effectively balance these two indicators. In this study, we introduce an improved particle swarm optimization algorithm into a face recognition algorithm based on image feature compensation techniques. This allows the system to achieve high recognition rates while simultaneously enhancing the recognition efficiency, aiming to strike a balance between the two aspects. This approach provides a new perspective for the application of image feature compensation techniques in face recognition systems. It helps achieve a broader range of applications for face recognition technology by reducing the recognition speed as much as possible while maintaining a satisfactory recognition rate. Ultimately, this leads to an improved user experience.

The triboelectric nanogenerator (TENG), as a novel energy harvesting technology, has garnered widespread attention. As a relatively young field in nanogenerator research, investigations into various aspects of the TENG are still ongoing. This review summarizes the development and dissemination of the fundamental principles of triboelectricity generation. It outlines the evolution of triboelectricity principles, ranging from the fabrication of the first TENG to the selection of triboelectric materials and the confirmation of the electron cloud overlapping model. Furthermore, recent advancements in TENG application scenarios are discussed from four perspectives, along with the research progress in performance optimization through three primary approaches, highlighting their respective strengths and limitations. Finally, the paper addresses the major challenges hindering the practical application and widespread adoption of TENGs, while also providing insights into future developments. With continued research on the TENG, it is expected that these challenges can be overcome, paving the way for its extensive utilization in various real-world scenarios. [ABSTRACT FROM AUTHOR]

The reclosing action of the distribution network may cause multi-stage voltage sag in the grid nodes, which leads to more serious losses for sensitive users. In order to more reasonably characterize the disturbance degree of multi-stage voltage sag on sensitive equipment, a frequency evaluation method based on process immune time (PIT) and improved analytic hierarchy process is proposed. Firstly, multi-stage voltage sag waveforms caused by the reclosing corresponding action under transient fault and permanent fault are analyzed, and the PIT characteristic curve of sensitive equipment under multi-stage voltage sag is characterized. Secondly, the weight function method is used to calculate the influence degree of each stage sag. The analytic hierarchy process is improved by utilizing the correlation and influence degree of each stage sag. The weight of each stage sag is determined, and then the amplitude of the multi-stage voltage sag is calculated equivalently. The multi-stage voltage sag frequency evaluation method is proposed in the distribution network. Finally, the IEEE 30-bus system is used for simulation verification. The results show that the proposed method is more accurate and reasonable for the evaluation of multi-stage voltage sag frequency. This method provides a basis for the frequency evaluation and governance of multi-stage voltage sag. [ABSTRACT FROM AUTHOR]

This paper focuses on the prediction of piezoelectric coefficients, Young's moduli and shear moduli of unidirectional piezoelectric fiber/carbon nanotube (CNT)/graphene nanoplatelet (GNP)-reinforced polymer composites using a novel micromechanics modeling technique. The multiphase composite configuration is that piezoelectric fibers are embedded within a polymer matrix filled by CNT/GNP hybrids. Agglomeration of hybrid nanofillers as a significant factor is identified and incorporated in the micromechanical calculation. Parametric studies are carried out to understand the effect of volume fraction, size and dispersion type of carbonous nanofillers as well as the piezoelectric fiber volume fraction on the effective material constants of multiphase composites. It is found that in comparison with the piezoelectric fibrous composite, the piezoelectric fiber multiphase composite containing CNT/GNP hybrids shows better elastic and piezoelectric properties. Also, further improvement in effective properties can be obtained by increasing the length and percentage of CNTs and GNPs. But, degradation in the elastic and piezoelectric constants is observed by the agglomeration of CNT/GNP hybrids. The current results are found to be in close proximity with the experimental data and other numerical results available in the literature. [ABSTRACT FROM AUTHOR]

A compact impact two-degree-of-freedom linear-rotary piezoelectric motor is proposed using a single actuator. The proposed piezoelectric actuator has a pair of deformation counteracting helical interdigitated electrodes on its outside surface, which can be divided into two parts. When the two parts of the piezoelectric actuator are driving under the same driving voltage signals, the motor can realize independent linear motion. When the two parts of the piezoelectric actuator are driving under the driving voltage signals with opposite duty cycles, the motor can realize independent rotary motion. The fabricated piezoelectric motor can produce a maximum average linear velocity of 1.9 and −2.3 mm/s with a saw-shaped driving signal of 400 Vp-p (peak-to-peak driving voltage) at 9 kHz. Experiments also show that the fabricated piezoelectric motor can realize a maximum average rotary velocity of 2440 and −2235 mrad/s with a driving signal of 400 Vp-p at 9 kHz. The maximum load force and torque of the prototype are about 0.4 N and 1.5 mN m, respectively. The proposed motor provides a wide driving frequency and realizes high velocity in both linear and rotary motions. [ABSTRACT FROM AUTHOR]

In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatelet (GPL)-reinforced composite multilayer cylindrical shell panel is studied for the first time. The shell is stiffened by both stringers and rings. Additionally, the effect of reinforcing the shell panel, ring and stinger with GPLs is independently studied. Halpin–Tsai relations are employed to evaluate the mechanical properties of the shell panel, rings and stringers. The first-order shear deformation shell theory, accompanied by the Lekhnitsky smeared stiffener model, using the numerical finite element method and Hamilton principle, is employed to develop the governing motion equations of the shell panel. Four different types of GPL patterns, including FG-A, FG-X, FG-O and UD, are assumed across the thickness of the shell panel, rings and stringers. The effects of different factors, including various weight fractions and patterns of GPLs nanofillers, the geometry of the shell panel and stiffeners and two displacement boundary conditions, on the natural frequencies of the shell panel, have been studied. [ABSTRACT FROM AUTHOR]

In order to improve the recognition rate and operational efficiency of the system, a method in which the image features compensation coefficients are optimized by using an improved simulated annealing algorithm is proposed. Firstly, eight computational factors with low computational complexity are given, which can be used to compensate image features. Secondly, the design flow of face recognition algorithm is presented. Thirdly, an improved simulated annealing algorithm is designed to solve the optimal combination of feature compensation coefficients in the face recognition system. Fourthly, the results of the feature compensation coefficients recommended by the improved simulated annealing algorithm are applied to the Efficient Face Recognition Algorithm (EFRA) in this paper, and verified on the simulation platform. Experiments show that the recognition rate can reach 100% when the training images are 6 in ORL. The proposed algorithm also performs well in MU_PIE dataset. [ABSTRACT FROM AUTHOR]

Friction drive and wear control is a tough issue for linear standing-wave ultrasonic motors with intermittent contact and impact friction. For the widely recognized reduction of friction/wear, minimum quantity lubrication was adopted to improve the output performances and services for motors through friction regulation. Given different preload and driving voltages, the mechanical characteristics of motors with minimal quantity lubrication were investigated using a homemade test rig. Results show that output performances and driving efficiency under film lubrication differ from those of dry friction. The optimized driving voltage was reduced by 31.5% and the minimum startup voltage was reduced by 41.67% using film lubrication. Additionally, the output speed increased by 26.29%, and thrust decreased by 41.26% under uniform exciting conditions (e.g., 150 V at 39.14 kHz). The existence of film lubrication broadens the effective frictional contact boundary, and effective friction contribution enhances the driving efficiency (the maximum efficiency of motors increased by 14%). Furthermore, the singularity of the effect of preload is significantly improved after lubrication, and the friction interface of the stator/slider becomes more controllable. Suitable lubrication is critical to the improvement of startup performance and prone to realize low-voltage driving, and the combination of lubrication regulation and wear inhibition is conducive to the durability and reliability of motors. This study provides an additional alternative for performance improvement of linear standing-wave motors apart from frictional materials. [ABSTRACT FROM AUTHOR]

A novel Ti–2Al–1.3V (wt.%) alloy was prepared by thermomechanical consolidation of a composite powder produced by high-energy ball milling of a mixture of TiH2 granules with a low oxygen content (0.1wt.%) and Ti–6Al–4V machining chips with a high oxygen content (0.8wt.%) at a mass ratio of 2:1. The microstructures and mechanical properties of the alloy in as-extruded state and after different heat treatments were investigated. The as-extruded alloy exhibits a martensite microstructure consisting of ultrafine and nanometer sized α' laths and aciculae and domains of layered structure containing δ(TiH) layers. The alloy in this state is brittle and fractures prematurely before yielding due to the ultrafine martensitic microstructure and hydrogen embrittlement associated with the high hydrogen content of the alloy. After vacuum annealing at 700°C for 6 h followed by furnace cooling, the alloy is further dehydrogenated with the hydrogen content being reduced to 0.008wt.%, the microstructure of the alloy changes into a full α/β lamellar microstructure with the continuous and discontinuous β layers being only 80–90 nm thick and the lamellar colony sizes being 10–30μm. The fine structured alloy in this heat treatment condition shows an excellent combination of high tensile yield strength of 996 MPa and ductility of 13.9%. After a further heat treatment of 980°C for 1 h followed by air cooling, the microstructure of the alloy consists of equiaxed α grains and α/βt lamellar structured domains (βt = β transformed structure), and unfortunately, this microstructure leads to a significant decrease of both the tensile yield strength (to 876 MPa) and the tensile ductility (to 7.4%). The fracture behavior of the alloy in different states is also studied, and the correlation between the microstructure and mechanical properties is discussed. [ABSTRACT FROM AUTHOR]

The contact process of stator and slider described by the Coulomb friction model is basically in a pure sliding friction state, and a mechanical model based on the Dahl friction theory was proposed to describe the contact process between stator and slider of V-shape linear ultrasonic motor. With consideration for the tangential compliance of stator and slider, the dynamic contact and friction processes of stator and slider were addressed in stages. The simulation results show that the ratio of the friction positive work decreases with the increase of the preload, and the vibration amplitude of the stator increases the proportion of positive work of the friction force. Improving the contact stiffness of the stator and slider is conducive to improving the output performance of the ultrasonic motor. The asymmetry of the left and right performance of the V-shaped vibrator will cause a difference in the left and right running speeds of the ultrasonic motor. The improved Dahl friction-driving model makes up for the discontinuity of tangential contact force calculated by the Coulomb friction model. This study demonstrates that the friction-driving model based on the Dahl theory is reliable and reasonable for linear ultrasonic motors according to the experimental results. [ABSTRACT FROM AUTHOR]

Fluoroalkyl(hetero)arylation of allylic alcohols with perfluoroalkyl iodide or difluoroacetic acid as fluoroalkyl source was developed herein, delivering functionalized ketones containing an α‐quaternary center. Formation of the fluoroalkyl radical was followed by its intermolecular addition to alkenes and the migration of a (hetero)aryl group with the concomitant generation of a ketone group to finish the domino sequence. Mechanistic studies indicated that the aryl migration proceeded through neophyl rearrangement in a radical pathway. Moreover, preliminary antifungal evaluation against Magnaporthe grisea is also described for the first time. [ABSTRACT FROM AUTHOR]

Fe-based Fischer–Tropsch synthesis (FTS) catalysts, promoted by graphitic carbon (GC) and potassium, were directly prepared by a novel modified sol–gel method without further reduction. The effects of the GC promoter and K contents on the catalyst structures and FTS performance were systematically studied. The significant improvement of FTS performance was attributed to GC, which acted as a reductant for synthesizing metallic Fe0 from Fe3+ in the chelating complexes, and effectively enhanced the strength of SiO2 channels. Meanwhile, an appropriate amount of K ions promoted CO chemisorption and inhibited H2 chemisorption by affecting the electronic properties of iron, resulting in a lower hydrogenation capacity and a higher olefin selectivity. Transmission electron microscopy and CO-TPD characterization proved that FeK@SiO2-GC catalysts had well-defined core–shell structures and higher CO chemisorption. The FTS results indicated that the introduction of a small amount of GC and K (K/Fe/GC, 1.5/100/100) improved the reduction and dispersion of iron during the calcination process, and significantly enhanced the FTS activity. The CO conversion and C2–C4 olefin selectivity of the catalyst increased rapidly from 21.1% and 23.7% to 53.5% and 41.3% after GC and K promotion. The GC and K promoted Fe-based catalysts prepared by a modified sol–gel method, which omits the complex and high energy consumption reduction process, can be used directly for highly efficient FTS and thus will be more promising in the future. [ABSTRACT FROM AUTHOR]