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Aiming at the voltage fluctuation problem caused by indirectness and uncertainty in new energy power generation system, the backstepping control strategy is firstly applied in electric spring (ES) system, and an ES backstepping control strategy with command filtering is proposed. According to the mathematical model of ES, the controller is designed by backstepping method and command filter is added to solve the computational inflation problem in ES backstepping control. Meanwhile, the error compensation signal is designed, and the stability of the system is verified by the Lyapunov stability theory. The effect of ES on critical load (CL) voltage stabilization is simulated when the grid-side voltage of the new energy power generation system fluctuates, and the sensitivity analysis of different system parameters to the control strategy is discussed in this paper. Compared with traditional proportional integral (PI) control, the dynamic response speed of CL voltage is improved by 0.07 s, while the CL voltage distortion rate is reduced by 31%. In parameter sensitivity analysis, the maximum deviation rate of CL voltage is 0.318%. Meanwhile, the maximum voltage amplitude fluctuation range that it can withstand is increased by 52.9 V. It is verified that the control strategy proposed in this paper has the advantages of fast response, low harmonic content and strong anti-interference ability.

Aiming at the accurate speed tracking control of electric vehicles (EV) driven by permanent magnet synchronous motors (PMSM) under external load torque disturbances, this paper proposes an approach for prescribed performance back-stepping control based on a disturbance observer. Firstly, a controller was designed using the back-stepping technique, and a second-order sliding mode differentiator was introduced to approximate the derivative of the virtual control law, which can solve the "differential explosion" problem in traditional back-stepping control techniques. Secondly, in order to reduce the influence of motor load disturbances in the driving process of EV, a novel disturbance observer was proposed, bolstering the anti-interference capability of system. In addition, to achieve the preset high transient and steady-state speed tracking performance, a prescribed performance control strategy was incorporated to guarantee tracking errors within predefined boundaries. Finally, the Lyapunov function was utilized to verify the system stability. The simulation results showed that, compared with traditional PI control, the designed controller significantly increased motor speed tracking precision by more than 5 times, demonstrating a superior speed tracking performance and enhanced anti-interference capability.

The upper airway cough syndrome (UACS) is a common chronic cough in children, and it has gradually increased in recent years. Chinese medicine believes that the main location of the disease is nasopharynx, which is closely related to the spleen and kidney. The most common pathological factor is wind, phlegm, deficiency and stasis, and the basic pathogenesis is upward inversion of lung Qi. Chinese medicine treatment mainly focuses on the combination of disease and syndrome differentiation, the combination of body and syndrome differentiation, staged Chinese medicine differentiation and treatment, cold and heat syndrome differentiation, viscera syndrome differentiation, Chinese medicine external treatment and combination of Chinese medicine and western medicine in order to regulate lung Qi. This article mainly elaborates on the differentiation and treatment of Chinese medicine for pediatric UACS, as well as its clinical treatment effects to provide some reference for further research on the treatment of pediatric UACS with Chinese medicine.

Highlights In the fiber winding process, the maximum static friction coefficient significantly influences the designable range of non‐geodesic winding trajectories and the behavior of fiber stacking and sliding. To accurately and conveniently measure the maximum static friction coefficient for fiber winding, a method based on semi‐geodesic trajectories was proposed. This method assesses the maximum static friction coefficient between fibers and mandrels, as well as between fibers, without requiring additional component fabrication. Its effectiveness was investigated, and two methods for determining fiber yarn slip were proposed. Additionally, measurement errors and variations in the slip coefficient before and after fiber yarn slip were examined. The research results indicate that the proposed measurement method has an error margin of approximately ±6%. After fiber yarn slip, the slip coefficient gradually decreases along the winding trajectory. The maximum static friction coefficient is independent of both winding speed and winding tension. A method for measuring the maximum static friction coefficient was proposed. Two methods were proposed for determining the slip of fiber yarn. The method allows for direct measurement using the mandrel to be wound. The maximum static friction coefficient between fibers can be measured. [ABSTRACT FROM AUTHOR]

[Objective] Vehicle detection is critical for urban intelligent transportation. Focusing on small target problems, high-density problems, and motion attribute problems, this study takes traffic surveillance images as input and aims to detect moving vehicles. [Method] Based on the anchor-free CenteNet, a detection method of multi-scale features and dual-source motion perception was proposed. Firstly, coordinate attention was introduced to the multi-scale and global context features of the network's abstraction layer, so as to supplement information in multiple stages and at multiple levels and improve the model's understanding of vehicles and scenes. Secondly, through fuzzy textures representing actual motion features of vehicles and optical flow knowledge representing general motion features of vehicles, the model's perception ability of moving vehicles was constructed. [Result] The experimental data came from the public dataset UA-DETRAC. The mean average precision (mAP) and frames per second (FPS) were used as the evaluation metrics of accuracy and speed. Experiment results show that the mAP and FPS of the proposed method are 70% and 30 frame/s respectively, which have the best balance between speed and accuracy among other compared methods. [Conclusion] It maintains that the proposed method is competent in the task of moving vehicle detection. [ABSTRACT FROM AUTHOR]

Salix sand barriers have been widely used in arid and semi‐arid regions of northern China as an environmentally friendly approach to control wind erosion. However, the inherent variability in length and thickness of Salix branches complicates achieving the desired fence porosity, typically resulting in an error of approximately 10% or more. This defect affects the fence's wind protection, thereby limiting their broader application. To address these challenges, we conducted a field experiment in the Hobq Desert, where we established Salix fences with porosities of 23%, 37%, and 44%, and measured the airflow velocities around these fences. The results indicated that the fence with 37% porosity exhibited the most effective sheltering effect, providing a protection distance up to 7.14 times of the fence height. A total of 44% porosity fences are also reasonably effective for practical purposes. On the other end of the spectrum, fences with 23% porosity demonstrated a better sediment interception than its high porosity peers, achieving an interception rate of 81.46%. Therefore, we conclude that organic fences made from Salix branches can serve as efficient windbreaks. Our findings provide foundational data for the application of organic fences in arid and semi‐arid regions of northern China, and potentially similar environments globally. [ABSTRACT FROM AUTHOR]

Current research on engine transient performance primarily focuses on the variation of key aerothermodynamic parameters in specific sections, neglecting the comprehensive understanding of the engine's inner flow field during transient operations. To address this gap, this paper proposes a two-dimensional transient simulation method that effectively captures the evolution of the flow field in the meridional plane. The approach involves deriving circumferential averaging equations in a rotating coordinate system with variable angular velocity, considering angular acceleration source terms. The engine components, including the compressor, combustion chamber, turbine, and rotating shaft, are individually modeled. The newly derived governing equations are solved using a dual-time-step approach, where an inner-iteration ensures mass flow conservation, and an outer-iteration updates the rotational speed. Using a real turbojet engine as a case study, transient examinations comprising acceleration and deceleration are performed. A comparative analysis of experimental and simulation results is conducted, revealing an average error of 0.9% in shaft speed, 7.8% in engine thrust, 1.7% in engine exhaust temperature, and 5.1% in compressor outlet pressure. Additionally, the study analyzes and compares the internal flow fields during the transient process, contributing to a deeper understanding of the engine's dynamic behavior. The research effort establishes a practical methodology and technology for conducting comprehensive two-dimensional engine transient cycle analyses within reasonable computational resources and timeframes. [ABSTRACT FROM AUTHOR]

An integral sliding mode observer-based fixed-time multi-faults estimation method is proposed to solve the problem of fast fault estimation for a class of nonlinear systems with multiple types of faults simultaneously. First, a class of nonlinear systems with actuator and sensor faults is considered, and the original system is transformed into two subsystems through coordinate transformation to decouple the actuator and sensor faults. Then, intermediate variables are introduced to transform sensor faults into actuator faults of the augmented systems. For the transformed system, a fixed-time fault observer based on integral sliding mode is designed to realize the fast estimation of unknown terms, and the fixed-time convergence performance is proved. Moreover, based on the output of the fault observer, the actuator and sensor faults in the original system are reconstructed. Finally, the fault model of the permanent magnet synchronous motor is established in the hardware-in-the-loop platform, and the effectiveness of the designed fault estimation method is verified. [ABSTRACT FROM AUTHOR]

As topological charge constitutes an infinite‐dimensional Hilbert space, vortex beam has numerous applications in optical communications and other fields where signal capacity is a vital requirement. Multifunctional vortex beams, showing up to different controllable responses subjected to separate combinations of polarization states, have significantly exhibited improved capacity of signal transport. Relying on prior physical knowledge, complex requirement brings tremendous challenge to the design of multifunctional vortex beams. Here, a deep‐learning‐based platform for designing metasurfaces is proposed, which can intelligently generate predesigned multifunctional vortex beams. Employing the proposed strategy, the demonstrations of bifunctional and trifunctional vortex beams are consistent with the design targets. Three samples are fabricated and measured by a Michelson interferometer. Clear observed interference patterns revealed the topological nature of the generated vortex beams, unambiguously justifying the design platform. This intelligent design strategy, which may inspire new ideas in other scientific fields, lays a solid foundation for the high‐performance application of multifunctional vortex beams. This work fully exploits the potential of vortex beams for large‐scale dense data communication and quantum optics with high quantum numbers, which may further promote the development of the integrated photonic chip. [ABSTRACT FROM AUTHOR]

The quality of urban living environments has become a focal point for local governments and citizens. By conducting a thorough analysis of the human settlement environment, the study can not only gain an intuitive insight into the quality of life of residents but also propose forward-thinking and sustainable suggestions for areas of improvement. This study optimizes and analyzes open platform data closely related to residents and assesses the suitability of different areas for living from diverse perspectives and methodologies. This study has chosen Beijing and Xi'an as the primary case studies. The local living environment is categorized into residential, living, recreational environment, transportation convenience, and safety. Our evaluation combines subjective and objective analysis methods and considers hotspot and cold spot analyses. This study employs the Analytic Hierarchy Process (AHP) as a subjective analysis method and the entropy method for objective analysis. By integrating both methods, it assesses the living environment conditions of Beijing and Xi'an. Furthermore, using GIS software, hotspot analysis is conducted for both cities, identifying areas of high and low quality. Detailed analysis is subsequently carried out for the low-quality clusters. Ultimately, this study, grounded in the theory of Transit-Oriented Development (TOD), presents recommendations for sustainable development aimed at representative rural towns and streets. City centers in Beijing and Xi'an have high-quality environments, while the outskirts show declining quality. Xi'an has uneven resource distribution, while Beijing is more balanced, with hotspot analyses indicating specific high- and low-quality cluster locations in both cities. These disparities and characteristics of the low-quality clusters offer insights for future urban development. [ABSTRACT FROM AUTHOR]

Smith–Purcell radiation (SPR) with broadly tunable spectra has attracted attention in light emission, and this free‐electron‐driven source shows great potential in illumination fields, such as terahertz sources, ultra‐compact light sources, free‐electron lasers, etc. However, it remains difficult to control the polarization properties of SPR and realize a free‐electron chiral light source. In this work, the chiral SPR with the maximum chirality (>40%) is acquired in a periodic stacked nanosquare light‐well, and the radiation chirality is manipulated by variations of the designed electron beam excitation positions. Furthermore, this work reveals that the chiroptical effect originates in the superposition of SPRs with different phases and polarization, which are derived from adjacent sidewalls. This work may deepen the comprehension of electron‐matter interaction and facilitate the development of compact electron‐driven chirality‐tunable source‐on‐chip, highlighting potential applications in photonic integration and binary data processing. [ABSTRACT FROM AUTHOR]

Core–shell particles are micro- or nanoparticles with solid, liquid, or gas cores encapsulated by protective solid shells. The unique composition of core and shell materials imparts smart properties on the particles. Core–shell particles are gaining increasing attention as tuneable and versatile carriers for pharmaceutical and biomedical applications including targeted drug delivery, controlled drug release, and biosensing. This review provides an overview of fabrication methods for core–shell particles followed by a brief discussion of their application and a detailed analysis of their manipulation including assembly, sorting, and triggered release. We compile current methodologies employed for manipulation of core–shell particles and demonstrate how existing methods of assembly and sorting micro/nanospheres can be adopted or modified for core–shell particles. Various triggered release approaches for diagnostics and drug delivery are also discussed in detail. [ABSTRACT FROM AUTHOR]

The errors contained in slant total electron content (STEC) have a strong impact on the image generated by ionosphere tomography. This paper presents a method that rejects abnormal corrections and rays (RACR) in the multiplicative algebraic reconstruction technique (MART) algorithm by applying a correction threshold and a rejecting ratio threshold. The RACR algorithm was validated using ionosonde observations, Swarm satellite measurements, independent STEC observations and a vertical total electron content (TEC) map. Its performance was compared with the MART algorithm on both geomagnetically quiet days and disturbed days. The results show that the RACA algorithm is able to capture the main phase and the recovery phase of a storm and outperforms the MART algorithm under both geomagnetic conditions. The average improvements over the MART algorithm are 36.01%, 36.56%, 6.18%, 22.10% and 6.03% in the validation tests of the peak density of F2 layer, peak height of F2 layer, the electron density of the topside ionosphere, STEC and VTEC, respectively. The quality of the image produced by the RACR algorithm was controlled by the correction threshold and the rejection threshold. Smaller threshold values tend to make the image smoother. The RACR algorithm provides not only a way to produce a better tomographic image but also a means to detect abnormal rays. [ABSTRACT FROM AUTHOR]

We investigated experimentally, analytically, and numerically the formation process of double emulsion formations under a dripping regime in a tri-axial co-flow capillary device. The results show that mismatches of core and shell droplets under a given flow condition can be captured both experimentally and numerically. We propose a semi-analytical model using the match ratio between the pinch-off length of the shell droplet and the product of the core growth rate and its pinch-off time. The mismatch issue can be avoided if the match ratio is lower than unity. We considered a model with the wall effect to predict the size of the matched double emulsion. The model shows slight deviations with experimental data if the Reynolds number of the continuous phase is lower than 0.06 but asymptotically approaches good agreement if the Reynolds number increases from 0.06 to 0.14. The numerical simulation generally agrees with the experiments under various flow conditions. [ABSTRACT FROM AUTHOR]

Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron‐ or/and photon‐based elements and devices. In combination with the advantages of emerging twistronics and valleytronics, the atomically thin transition metal dichalcogenide semiconductors open up new opportunities for pursuing practical excitonic devices, where the strong exciton binding energy enables operating exciton at room temperature. The essential and foremost step toward exciton devices is the control of spatiotemporal exciton flux, which is density‐dependent and affected by the complex many‐body interactions. It can be effectively controlled by the strain, electric field, electron‐doping, and local dielectric environment. Intriguingly, exotic phenomena such as exciton condensation, electron‐hole liquid, exciton Hall effects, and exciton halo effects can be occurred in 2D exciton system, providing new possibilities for excitonic devices. Up to now, the proof‐of‐principle of room temperature exciton devices, including excitonic switching and transistor, exciton guides, and excitonic nanolaser, have been realized. Here the authors review the recent advances in molding 2D exciton flux from basic principle, manipulation, exotic phenomena to promising applications and discuss the opportunities and challenges in pushing the frontiers of room temperature excitonic devices. [ABSTRACT FROM AUTHOR]

Inertial microfluidics functions solely based on the fluid dynamics at relatively high flow speed. Thus, channel geometry is the critical design parameter that contributes to the performance of the device. Four basic channel geometries (i.e., straight, expansion-contraction, spiral and serpentine) have been proposed and extensively studied. To further enhance the performance, innovative channel design through combining two or more geometries is promising. This work explores embedding periodic concave and convex obstacle microstructures in sinusoidal channels and investigates their influence on particle inertial focusing and separation. The concave obstacles could significantly enhance the Dean flow and tune the flow range for particle inertial focusing and separation. Based on this finding, we propose a cascaded device by connecting two sinusoidal channels consecutively for rare cell separation. The concave obstacles are embedded in the second channel to adapt its operational flow rates and enable the functional operation of both channels. Polystyrene beads and breast cancer cells (T47D) spiking in the blood were respectively processed by the proposed device. The results indicate an outstanding separation performance, with 3 to 4 orders of magnitude enhancement in purity for samples with a primary cancer cells ratio of 0.01% and 0.001%, respectively. Embedding microstructures as obstacles brings more flexibility to the design of inertial microfluidic devices, offering a feasible new way to combine two or more serial processing units for high-performance separation. [ABSTRACT FROM AUTHOR]

In the failure analysis of composite materials, the damage of fiber and matrix is always noticed rather than the debonding of interface which is responsible for transferring the load between matrix and fiber. The stress amplification factors of fiber, matrix, and interface were extracted by establishing representative volume element model with interface and the strength of corresponding constituent is calculated in our work. Micro mechanics of failure served as the initial failure criterion of material components, and user-material subroutine (UMAT) was applied to realize progressive damage analysis of fiber metal laminate (FML) under different loading angles. The analysis results show that it is not strictly correct to directly use the stress on the matrix to calculate interface stress, and the damage trend of interface is consistent with that of fiber. The strain hardening phenomenon of FML decreases with larger loading angle, and the mechanical response of FML is about 45° symmetric due to its structure symmetry. The simulation results are in good agreement with the experiment results. [ABSTRACT FROM AUTHOR]

The change of the blade tip clearance size has an important impact on the performance of the compressor. Considering that the performance curve of the compressor is often limited by surge and stall boundaries, this paper used the numerical simulation method to investigate the influence mechanism of the blade tip clearance size change on the stall margin of transonic axial flow compressor rotor. By mathematically decomposing the calculation formula of the stall margin of rotor, the approximate calculation formula of the change of rotor's stall margin was obtained. Then, the detailed quantitative analysis of the factors that affect the rotor's stall margin was carried out, the influence weights of various factors on the rotor's stall margin was also obtained. Finally, the physical mechanism of the change of the rotor's performance parameters was obtained by the analysis of rotor tip flow field after the blade tip clearance size change. [ABSTRACT FROM AUTHOR]