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Objective Aviation tubes have been widely used in various systems of aerospace equipment owing to their excellent physical and chemical properties. It is important to ensure the manufacturing quality of aviation tubes for the safety of aircraft. Aviation tubes are manufactured by bending straight tubes. Under the action of the bending moment, the inner side of the tube is wrinkled and deformed owing to compressive instability. Although numerous researchers have investigated various manufacturing methods in the past few decades, wrinkle deformation is still unavoidable. The wrinkle degree of the tube is a key indicator of tube deformation, with the key geometric parameter being the wrinkle depth. Conventional manual inspection methods cannot guarantee the measurement efficiency and reliability of measurement results. Using a digital 3D measurement method can effectively avoid these shortcomings. Such methods quickly capture the surface shape data of the target object and have been widely used in welding seam detection and contour deformation detection.
Objective Aviation tubes have been widely used in various systems of aerospace equipment owing to their excellent physical and chemical properties. It is important to ensure the manufacturing quality of aviation tubes for the safety of aircraft. Aviation tubes are manufactured by bending straight tubes. Under the action of the bending moment, the inner side of the tube is wrinkled and deformed owing to compressive instability. Although numerous researchers have investigated various manufacturing methods in the past few decades, wrinkle deformation is still unavoidable. The wrinkle degree of the tube is a key indicator of tube deformation, with the key geometric parameter being the wrinkle depth. Conventional manual inspection methods cannot guarantee the measurement efficiency and reliability of measurement results. Using a digital 3D measurement method can effectively avoid these shortcomings. Such methods quickly capture the surface shape data of the target object and have been widely used in welding seam detection and contour deformation detection.
Microirregular components manufactured via rolling, extrusion, and drawing have complex shapes with irregular processing sections. This structural element is widely utilized in devices such as highend clocks, electronics, and medical appliances. Currently, the geometric dimension measurements of microirregular components are realized by using a microscope during the manufacturing process. However, this method is labor intensive with low production efficiency and unstable measurement accuracy. Therefore, a linestructured light based microirregular component geometric dimension measurement method is proposed in this study. First, the internal and external parameters as well as the distortion coefficients of the industrial camera are obtained by implementing the calibration method by Zhang Zhengyou, while the linestructured light plane is calibrated using the Steger thinning method and least squares method. Second, a microirregular component geometric dimension measurement program is developed using Microsoft Foundation Classes and OpenCV. Finally, the measurement accuracy and repeatability of the method are evaluated by using the standard gauge block and the geometric dimension measurement test of three kinds of microirregular component. The results reveal that the overall measurement errors of this method are less than 0. 1 mm in both width and height, achieving high measurement accuracy to meet the needs of actual production.
<b>Objective</b> Digitally coded hypersurfaces show great potential in the field of electromagnetic wave modulation. Coded hypersurfaces are mainly used to encode different bits through the phase difference between unit structures. Currently, the coded hypersurfaces in terahertz band are mainly classified into two types: structure coded and controlled material coded. Once a structure-encoded hypersurface is fabricated, its function is fixed, which makes it difficult to adapt to changing application requirements. In contrast, the controllable material-encoded hypersurfaces can realise dynamic regulation and multifunctional switching of terahertz beams by changing the external excitation, showing good reconfigurability. To address this challenge, a coded hypersurface based on Dirac semimetal is proposed in this paper. Dirac semimetals have unique physical properties, such as insensitivity to changes in dielectric constant, which give them significant advantages in hypersurface design. By adjusting the external excitation, e.g., changing the bias voltage, the Fermi energy level of the Dirac semimetal can be changed, and thus its relative dielectric constant can be dynamically adjusted. This property can be exploited to obtain 2-bit coding units, endowing the hypersurface with multifunctional reconfigurable capabilities. Traditionally, the gradient-phase method encodes arrays by periodically arranging the cell structure, but there are limitations in the flexibility and accuracy of beam modulation. In order to break through these limitations, genetic algorithms are employed in this study for the inverse design of hypersurface coding arrays, which effectively improves the initiative and flexibility of beam modulation. Combined with the application of the controllable material Dirac semimetal, the hypersurface design in this study not only realises the diversity of functions, but also possesses a high degree of reconfigurability, which meets the needs of complex application scenarios. <b>Methods</b> Firstly, a three-layer cell structure is designed with a Dirac semimetal top layer consisting of a "back" patch layer, a polyimide dielectric layer in the middle, and a gold backing layer at the bottom, and the final cell structure is obtained by scanning and optimising the structural parameters. The Fermi energy level of the Dirac semimetal is then scanned to obtain a hypersurface coding unit with a 90° phase difference. Thus, 2bit coding is achieved. After the coding unit is determined, according to the far-field scattering principle, the array coding of the hypersurface is reverse-designed according to the target function using genetic algorithms, so that the coded hypersurface is equipped with three functions that can be switched, including beam fouling, vortex beam generation, and RCS reduction. <b>Results and Discussions</b> The cell structure obtained after parameter scanning is shown in Fig. 1, and the reflection amplitude and phase curves of the hypersurface coding cell are shown in Fig. 6 when the Fermi energy levels are 0.01eV, 0.05eV, 0.09eV, 0.55eV, and the reflection amplitudes of the hypersurface coding cell are all near 0.67 at 1.95 THz, and the phase difference of the neighbours of the four states is about 90°. Therefore, 2-bit coding can be achieved at 1.95 THz when the Fermi energy levels are 0.01 eV, 0.05 eV, 0.09 eV, and 0.55 eV. Based on the designed hypersurface coding unit, full-wave simulation of the coding sequence is performed.The results show that, for beam assignment, single-beam and multibeam reflections with pitch angle within 40° and azimuth angle within 360° can be realised at 1.95 THz, and the pitch angle and azimuth angle of each beam in the multibeam can be individually regulated, which improves the flexibility of terahertz beam regulation; for vortex beams, the topology charge numbers of l=±1, l For vortex beams, single vortex beams with topological charges of l=±1, l=±2 can be generated, and single vortex beams and multiple vortex beams can be regulated at any angle within the range of pitch angle of 30° and azimuth angle of 360°. In addition, a radar scattering cross-section reduction of more than 10 dB can be achieved within the range of 1.72 THz-2.51 THz. <b>Conclusions</b> In this study, we present an innovative multifunctional coded hypersurface that is based on a Dirac semimetal and designed using a genetic algorithm for reverse array coding. This design endows the hypersurface with several functions such as beam fouling, vortex beam generation and radar scattering cross-section (RCS) reduction, demonstrating its multifunctional reconfigurability.Compared with conventional beam dynamics tuning methods that rely on feeder-compensated phasing or complex-coded addition theorems, our design scheme not only improves the design efficiency, but also adapts to diverse application scenarios. The results confirm the performance of the hypersurface at 1.95 THz: in beam fouling, it is capable of precise tuning of single and multiple beams (dual- to five-beam) at arbitrary angles within 40° of pitch angle and 360° of azimuth; in vortex beam generation, it is capable of generating single-vortex beams with topological charges ±1 and ±2, with mode purity exceeding 60%, and achieving single-vortex, dual-vortex and five-beam dynamic tuning through vortex phase In terms of RCS reduction, the hypersurface is capable of achieving more than 10 dB of RCS reduction in the frequency range from 1.72 THz to 2.51 THz, especially in the frequency range of 1.82 THz, the maximum reduction value can be up to 27.5 dB. In summary, the proposed Dirac semi-metallic-based coded hypersurface not only possesses versatile reconfigurable properties, but also exhibits excellent performance. These features foretell a broad application potential of the hypersurface in the fields of communication networks, antenna design, and radar systems.
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