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With the increasingly fierce competition in international competitive sports, the momentum of special training has increased. Sports injuries are becoming more and more serious, which restricts the further improvement of the level of athletes. How to solve the problem of prevention, treatment, and rehabilitation of sports injuries, so as to ensure the normal training and competition of athletes, is an important part of sports work. Machine learning can solve large-scale data problems that cannot be solved by human beings at present and has strong self-learning ability, self-optimization ability, and strong generalization ability. Therefore, the purpose of this study is to understand the characteristics of rhythmic gymnastics injuries and analyze their causes by investigating the injury status of elite rhythmic gymnasts. According to the characteristics of the project, the injury characteristics of the athletes themselves, and other factors, using scientific qualitative and quantitative indicators, the injury risk of key athletes in rhythmic gymnastics was evaluated. It also provides theoretical and practical references for preventing sports injuries, formulating and implementing sports injury rehabilitation programs. The experimental results show that the female vaulting risk in the five risk categories fluctuates from 179.62 to 365.8, ranking the first in the risk of acute sports injury. [ABSTRACT FROM AUTHOR]

Perfect vortex (PV) beams possess a radial intensity profile independent of their topological charges, overcoming the defects of the regular vortex beams. However, the bulky optical elements used in conventional methods for generation of PV beams limit their potential applications. Metasurfaces are ultra-thin version of metamaterials with the flexible ability of controlling electromagnetic waves, promising great potential applications in many optical fields. Here, an all-dielectric metasurface based on a geometrical phase is demonstrated, featuring broadband and high efficiency in manipulation of circularly polarized light. We numerically simulate the performance of the unit-cell and metasurface for generating PV beams carrying integer and fractional topological charges. We hope the designed metasurface will provide an ultra-compact way for generation of high-quality PV beams. [ABSTRACT FROM AUTHOR]

Aiming at the problems of severe vibration of switched reluctance motor (SRM) and the transfer of the peak vibration caused by newly produced radial magnetic force under static eccentricity (SE), this study proposes a vibration reduction method for SE. First, the analytical relationship between the radial magnetic force harmonics and the current harmonics is derived. 2D Fourier decomposition is used to analyse the temporal–spatial characteristics of force harmonics and the vibration response under SE. Then the expression of the force harmonic, which causes the peak vibration, is used as the optimisation function of current harmonics. According to the analyses in this study, it is difficult to consider vibration reduction and torque simultaneously by single‐order current harmonic optimisation and the unreasonable optimisation range of current will seriously affect the output performance. Therefore, a reasonable optimisation range is set based on the above conclusions and the first five order current harmonics are optimised to improve the effect of vibration suppression further. The results of the finite element simulation verify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

Aiming at the problem of severe unbalanced magnetic force (UMF) of the switched reluctance motors (SRMs) caused by eccentricity, this paper analyses the radial electromagnetic force's spatial distribution and frequencies under eccentricity and conduct a compensation method for the UMF. Firstly, the expression of the radial electromagnetic force under eccentricity is derived by using the method of magnetomotive force multiplying permeance, combining with the modification of the permeance. Secondly, the UMF is reduced by applying compensation current to the two stator poles of the permeance-descending phase. The selection of the stator poles and the calculation of the compensation current are decided according to the direction and the value of the unbalanced flux density. Dynamic eccentricity (DE) will produce new frequencies and spatial orders of the radial electromagnetic force, and the static eccentricity (SE) only produces the new spatial orders. The results obtained by the finite element model prove that this method can effectively reduce the UMF without sacrificing the output torque performance. [ABSTRACT FROM AUTHOR]

The stability problem of a three‐phase voltage source PWM AC–DC converter is addressed through an improved adaptive backstepping method, which combines the following contents: input–output linearisation, adaptive backstepping method, error compensation and sliding mode control. The state equation of the three phase system is obtained by the power balance relationship between the input current and the output voltage, and then the coordinate conversion is carried out in order to design the controller. When the input–output linearisation method transfers the system model to a strict‐feedback form, an improved adaptive backstepping control approach is given to stabilise the converter. Finally, the simulation results show that the improved method has three benefits: retain a faster stability of rectifier, reduce overshoot of DC voltage and bring about a real‐time parameter estimation. [ABSTRACT FROM AUTHOR]

• We proposed the high-performance dynamic beam all-direlectric coding metasurface converter based on phase change materials of GST in optical communication band. • We found the theoretical support for optimizing geometric parameters by multipole decomposition and field diagram characterization of amorphous and crystalline elements. The optimized units can achieve ultra-high transmittance and 2π phase coverage in amorphous state. • The large contrast in transmittance and phase between the two states enables us to switch the beam deflection without changing the structure. And further applied it to the design of beam focusing and holographic reconstruction. • We arrayed the units into coding metasurface, and with the help of Fourier method, we realized the beam deflection at any angle in the working band of 1.119um. Phase change materials, especially Ge 2 Sb 2 Te 5 (GST), play an important role in the design of dynamic all-dielectric metasurface due to its flexibility and adjustability. And its non-volatility makes it possible to form dynamic metasurfaces with complex functions. In this paper, we propose a cross-shaped all-dielectric metasurface based on GST interlayer, which can achieve ultra-high transmittance and complete 2π phase coverage in the near-infrared band when the interlayer material is in amorphous state. Through multipole decomposition and field distribution characterization, we have revealed the regulation principles of the unit cell before and after the switching. And thus, we designed the arrays of metasurface with switchable beam deflection, arbitrary coding and focusing functions. Holographic reconstruction based on GS algorithm is discussed and extended to independent control of the RGB channels in imaging applications. Our research can provide a reference for the design of compact multifunctional optical elements, optical encryption and dynamic metasurfaces. [ABSTRACT FROM AUTHOR]

Figures 4(d)-4(f) show the simulated intensity profile of the elliptical PV beams at the focal plane ( I z i = 14 HT ht m) with I l i = 1, 2, and 3. Publisher's Note: "Generation of integer and fractional perfect vortex beams using all-dielectric geometrical phase metasurfaces" [Appl. Phys. Also on page 4, the last paragraph, the first sentence has been corrected as "To generate an elliptical PV beam, we set ellipticity I e i as 0.7 and use 830 nm incidence in the simulation. [Extracted from the article]

In this paper, we demonstrate an adjustable trifunctional absorber that can achieve the conversion of broadband, narrowband and superimposed absorption based on the phase transition material vanadium dioxide (VO2) in the mid-infrared domain. The absorber can achieve the switching of multiple absorption modes by modulating the temperature to regulate the conductivity of VO2. When the VO2 film is adjusted to the metallic state, the absorber serves as a bidirectional perfect absorber with switching capability of wideband and narrowband absorption. The superposed absorptance can be generated while the VO2 layer is converted to the insulating state. Then, we introduced the impedance matching principle to explain the inner mechanism of the absorber. Our designed metamaterial system with a phase transition material is promising for sensing, radiation thermometer and switching devices. [ABSTRACT FROM AUTHOR]

By integrating advanced deep learning and specific energy domain knowledge, Chen et al. develop a novel deep learning-based image recognition to assist energy saving and emission reduction for industrial energy systems, which greatly increases the recognition accuracy by 18.3% and decreases the energy consumption by 34.5%. [Display omitted] • A novel energy knowledge-integrated image recognition technology was applied to assist energy savings. • Non-physical image information was combined with specific energy domain knowledge for the first time. • The proposed image recognition model enables both high recognition accuracy and strong generalization ability. • The energy consumption reduces by 34.5% through adopting image recognition-based control optimization method. • The proposed control optimization method can be easily extended to general energy systems. Image recognition technology has immense potential to be applied in industrial energy systems for energy conservation. However, the low recognition accuracy and generalization ability under actual operation conditions limit its commercial application. To improve the recognition accuracy and generalization ability, a novel image recognition method integrating deep learning and domain knowledge was applied to assist energy saving and emission reduction for industrial energy systems. As a typical industrial scenario, the defrosting control in the refrigeration system was selected as the specific optimization object. By combining deep learning algorithm with domain knowledge, a residual-based convolutional neural network model (RCNN) was proposed specifically for frosty state recognition, which features the residual input and average pooling output. Based on the real-time recognition of frosty levels, a defrosting control optimization method was proposed to initiate and terminate the defrosting operation on demand. By combining the advanced image recognition technique with specific energy domain knowledge, the proposed RCNN enables both high recognition accuracy and strong generalization ability. The recognition accuracy of RCNN reached 95.06% for the trained objects and 93.67% for non-trained objects while that of only 75.86% for the conventional CNN. By adopting the presented system optimization method assisted by RCNN, the defrosting frequency, accumulated time and energy consumption were 53.8%, 57.02% and 34.5% less than the original control method. Furthermore, the environmental and cost analysis illustrated that the annual reduction in CO 2 emissions is 2145.21 to 3412.84 kg and the payback time was less than 2.5 years which was far below the service life. The technical feasibility and significant energy-saving benefits of deep learning-based image recognition method were demonstrated through the field experiment. Our study shows the great application potential of image recognition technology and promotes carbon neutrality in industrial energy systems. [ABSTRACT FROM AUTHOR]

Vortex beams have been adopted as optical communications tools to improve the information capacity of free-space communication. Topological charge (TC) is a key parameter for analyzing vortex beams, specifically when defining wavelength division multiplexing and information coding capabilities. TC is typically proportional to the radial intensity profile and orbital angular momentum. The radial intensity profile of perfect vortex (PV) beams is TC-independent, thereby improving the efficiency of image processing and optical fiber transmission; however, PV beams generated in traditional ways are restricted in their degree of freedom for multiplexing and it can be difficult to distinguish PV beams with different TCs. Herein, we numerically simulate a single all-dielectric geometric metasurface to generate PV beams with intensity patterns corresponding to the TC. We increase the types of intensity modes by superposing specific polarization states of Laguerre–Gaussian beams, creating many options for optical communication transmission purposes. • We incorporated the superposition theory of Laguerre–Gaussian beams into the phase superposition formula of PV beams, and theoretically created a superposed PV beam. • The superposed PV beam has a great degree of freedom, and the superposition of different topological charges is reflected in the different number of light spots in the pattern. • We have designed a single geometric metasurface to simulate a four channel superposed PV beam, the metasurface can directly convert a common Gaussian beam into four different superposed PV beams. [ABSTRACT FROM AUTHOR]

A liquid surface deformation sensor with high sensitivity based on a Mach–Zehnder interferometer (MZI) was demonstrated. The MZI was constructed by cascading two Bowknot Type Tapers (BTTs) with an interval of 1.0 cm. As the liquid surface changes gradually from the position higher than the optical fibre to a position lower than the optical fibre, the external environment of the optical fibre changes gradually from the liquid to air, this will result in a change of the interference of the MZI. By measuring the intensity variations of the resonant wavelength, the liquid surface deformation in the range from 0 to 5.22 mm can be determined with a high sensitivity of 0.99 dB/mm. [ABSTRACT FROM AUTHOR]

• A waveguide chip that disperses light and focuses it directly onto a camera without any free-space elements. • Fine spectral resolution (0.42nm) and a large focal depth (>4mm) for precise spectral analysis with relaxed system alignment. • No need for customized detectors and electronic circuits. • The chip can be easily mounted to any commercial camera for fiber spectrum analysis. We propose and experimentally demonstrate a fiber spectrum analyzer based on a planar waveguide chip butt-coupled with an input fiber and aligned to a standard camera without any free-space optical elements. The chip consists of a single-mode waveguide to connect with the fiber, a beam broadening area, and a waveguide array in which the lengths of the waveguides are designed for both wavelength separation and beam focusing. The facet of the chip is diced open so that the outputs of the array form a near-field emitter. The far field are calculated by the Rayleigh-Sommerfeld diffraction integral. We show that the chip can provide a focal depth on the millimeter scale, allowing relaxed alignment to the camera without any fine-positioning stage. Two devices with 120 and 220 waveguides are fabricated on the polymer waveguide platform. The measured spectral width are 0.63 nm and 0.42 nm, respectively. This simple and practical approach may lead to the development of a spectrum analyzer for fiber that is easily mountable to any commercial camera, thereby avoiding the complication for customized detectors as well as electronic circuits afterwards. [ABSTRACT FROM AUTHOR]

• Cascaded Bowknot-type taper based Mach–Zehnder interferometer (MZI) could be used for microfluidic flow rate detection. • The proposed sensor is suitable for liquids with refractive indexes ranging from 1.33 to 1.43. • The detectable water flow rate ranges from 0.66 mm/s to 10.6 mm/s. In microfluidic chip applications, the flow rate plays an important role. Here we proposed a simple liquid flow rate sensor by using two cascaded bowknot-type tapers (BTTs) to form a Mach–Zehnder interferometer (MZI) as the sensing element. As the water flows in the vicinity of the BTT, the cascaded BTTs based MZI's interference spectrum changes due to its contact with water. By comparing the time-swept spectra of the cascaded BTTs MZI from the state of one BTT in water to that of another BTT in water as the water flowing over it, the flow rate can be detected. The proposed sensor has a detectable range from 0.66 mm/s to 10.6 mm/s. [ABSTRACT FROM AUTHOR]

Aim: Reactive oxygen species (ROS) plays important roles in aging. However, the specific mechanisms for intracellular ROS accumulation, especially during aging, remain elusive. Results: We have reported that Fas-associated protein with death domain (FADD) phosphorylation abolishes the recruitment of phosphatase type 2A C subunit (PP2Ac) to protein kinase C (PKC)βII, which specifically regulates mitochondrial ROS generation by p66shc. Here, we have studied the role of FADD phosphorylation in an FADD constitutive-phosphorylation mutation (FADD-D) mouse model. In FADD-D mice, the constitutive FADD phosphorylation led to ROS accumulation (hydrogen peroxide [H2O2]), in a process that was dependent on PKCβ and accompanied by increased PKCβ and p66shc phosphorylation, impaired mitochondrial integrity, and enhanced sensitivity to oxidative stress-mediated apoptosis. Moreover, FADD-D mice exhibited premature aging-like phenotypes, including DNA damage, cellular senescence, and shortened lifespan. In addition, we demonstrate that FADD phosphorylation and the recruitment of PP2A and FADD to PKCβ are induced responses to oxidative stress, and that the extent of FADD phosphorylation in wild-type mice was augmented during aging, accompanied by impairment of the interaction between PKCβ and PP2A. Innovation: The present study first addresses the role of FADD phosphorylation in aging through controlling mitochondrial ROS specifically generated by PKCβ. Conclusion: These data identify that FADD phosphorylation is critical for the PKCβ-p66shc signaling route to generate H2O2 and to implicate enhanced FADD phosphorylation as a primary cause of ROS accumulation during aging. Antioxid. Redox Signal. 21, 33-45. [ABSTRACT FROM AUTHOR]

In this paper, the radial electromagnetic force and vibroacoustic behaviour of a switched reluctance motor (SRM) are predicted and analysed in detail. First, the radial force with the spatial–temporal distribution characteristics is derived analytically and verified by the 2D Fourier transform. Second, a multiphysics model, which not only includes the electromagnetic field, the mechanical field, and the acoustic field, but also takes into account the structural orthotropy and the non-uniformly distributed electromagnetic force, is established to predict the electromagnetic vibration and noise of a SRM. Third, based on the spatial and temporal orders of the force harmonics, the vibroacoustic mechanism of a SRM is revealed. Finally, the electromagnetic force and vibration under two control strategies, which include the angle position control (APC) and the current chopping control (CCC), are compared and analysed, respectively. The results show that the electromagnetic vibration and noise of a three-phase 12/8 SRM are mainly caused by the force harmonics with the spatial order of 4 and the temporal orders of 3 N 0 ± 1 (N 0 = 0, 1, 2···). Besides, under the two control strategies, the orders of the electromagnetic force and vibration are the same, but the amplitudes are different. [ABSTRACT FROM AUTHOR]