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Radar enables a convenient, contactless way for gait analysis in daily scenarios, such as in‐home health monitoring. However, the overlapping of human limb components could occur in both range and velocity dimensions of the radar echo, which makes it difficult to distinguish the limbs. In this study, a trajectory tracking and recombination method based on range‐Doppler‐time data is proposed for gait feature estimation under insufficient radar resolution. In the trajectory tracking step, the scattering amplitude is included for Kalman filtering, and the weighted joint nearest neighbour algorithm is proposed for data association. Then, the trajectories are recombined to construct the limb tracks based on the relative range‐Doppler angles. Finally, the limb tracks are used to estimate the spatial‐temporal and kinematic gait features. In our simulation, the trajectory tracking accuracies range from 98.2% to 99.6%. The gait feature estimation accuracies for simulation and measurement are no less than 91.9% and 93.8% respectively. [ABSTRACT FROM AUTHOR]

Due to the high‐speed rotors and overlapped propellers, it is still a challenge to extract the micro‐motion parameters of the quadcopter. In this work, the authors establish a radar backscattering model of the quadcopter based on the flight control theory and radar backscattering characteristics. Then, the improved template matching method and peak grouping method are proposed to capture the periodic information for overlapped propellers on a range‐time profile and extract the rotation speeds of rotors. By simulating the nine types of quadcopter movements, the relative error of the rotation speeds is estimated to be lower than 1.4% for each rotor with a signal‐to‐noise ratio of 15 dB. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) including Stereolithography (SLA) and more recent 3D printing derivatives is an innovative manufacturing technology, where objects can be manufactured by accumulation of successive layers of materials. Such technology enables the fabrication of highly customized radar absorbing materials (RAM) and novel RAM structures. The microwave absorption, printability, complex electromagnetic parameters were measured, acrylic ester photopolymer with carbon nanotubes (CNTs) content ranging from 0.5% to 1.5% prepared with digital masking AM technology. Good dispersion and the content of CNTs have major influences on the successful preparation. The printability limit of multiwalled CNT is found to be 1.6%.The maximum absorption of 6 mm‐thick composites is measured to be −15.98 dB with 1.5% CNT content. The real part ( ε ′) of permittivity increases from 2.5 to 7 and the imaginary part ( ε ″) of permittivity increases from 0.2 to 1.0 with the increasing content of CNTs. Frequencies, thickness, uniformly distribution of CNT and CNT content are the main factors affecting the RAM properties. The calculated reflection loss, for 12 mm‐thick composites, are −7 dB, −26 dB, and −34 dB for 0.5%, 1%, and 1.5% of CNT contents, respectively, and the matching frequency shifts to lower frequencies with the increase of thickness or CNT content, which is in agreement with electromagetic theory and experiment results. POLYM. COMPOS., 39:E671–E676, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]