The aim of this paper is to compare the mechanical property and machinability of Polyetheretherketone (PEEK) and 30 wt% carbon-fibers reinforced Polyetheretherketone (PEEK CF 30). The method of nano-indentation is used to investigate the microscopic mechanical property. The evolution of load with displacement, Young’s modulus curves and hardness curves are analyzed. The results illustrate that the load-displacement curves of PEEK present better uniformity, and the variation of Young’s modulus and hardness of PEEK both change smaller at the experimental depth. The machinability between PEEK and PEEK CF 30 are also compared by the method of single-point diamond turning (SPDT), and the peak-to-valley value (PV) and surface roughness (Ra) are obtained to evaluate machinability of the materials after machining. The machining results show that PEEK has smaller PV and Ra, which means PEEK has superior machinability.

In order to solve the problem of the traditional iterative closest point algorithm (ICPA), which requires a high initial position of point cloud and improves the speed and accuracy of point cloud registration, a new registration method is proposed in this paper. Firstly, the rough registration method is optimized. As for the extraction of the feature points, a new method of feature point extraction is adopted, which can better keep the features of the original point cloud. At the same time, the traditional point cloud filtering method is improved, and a voxel idea is introduced to filter the point cloud. The edge length data of the voxels is determined by the density, and the experimentally verified noise removal rates for the 3D cloud data are 95.3%, 98.6%, and 93.5%, respectively. Secondly, a precise registration method that combines the curvature feature and fast point feature histogram (FPFH) is proposed in the precise registration stage, and the algorithm is analyzed experimentally. Finally, the two point cloud data sets Stanford bunny and free-form surface are analyzed and verified, and it is concluded that this method can reduce the error by about 40.16% and 36.27%, respectively, and improve the iteration times by about 42.9% and 37.14%, respectively.

An optically transparent metamaterial absorber with polarization insensitivity and wide-angle absorption is proposed. The absorber, which consists of an indium tin oxide resistive film and a low-loss substrate, is optically transparent and conformal. By tuning the reflection response of the frequency-selective surface and the thickness of the spacer layer, the whole structure achieves an absorption of more than 97% in the range of 6.54–18.66 GHz. Numerical simulation results show that the absorber can still maintain an absorption rate of more than 85% in a wide range of oblique incidence angles from 0° to 60°. In addition, the intrinsic physical mechanism of the absorber is elucidated using the impedance matching theory and the distribution of surface currents. The ratio of dielectric loss and ohmic loss is also quantitatively analyzed. Finally, the reflection and transmission coefficients of the sample were measured in a microwave anechoic chamber, which showed a good agreement with the simulation results. This design uses a low-resistivity resistive film as a frequency-selective surface, which was rarely involved in previous studies, and provides a new idea for future design and application.

The burst motion as a potential motion is discovered in recent years and has important effects on the output performance of the piezoelectric actuator. How to induce the burst motion has become a research hotspot and a current challenge in the field of the piezoelectric actuator. To eliminate the backward motion and induce significant burst motion, an epicycloid induction principle (EIP) was proposed in this article. Correspondingly, a stick–slip piezoelectric actuator with a special dual feet compliant mechanism was designed, and the corresponding prototype was fabricated to verify the EIP. Under the excitation of square wave signals, the driving and clamping feet alternately pushed the bearing, and the epicycloid motion of the bearing induced the burst motion of the slider. The threshold voltage about the clamping foot of the prototype with no backward motion was set through the pre-experiment. At this voltage, the displacement–time curves in one period showed three consecutive steps, which confirmed the feasibility of the EIP. In addition, the prototype has a resolution of 160 nm and the vertical loading capacity greater than 5 N. The proposed EIP is effective for inducing significant burst motion and offers a novel idea for the structure design of the stick–slip actuators.