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Gait impairment in Parkinson’s Disease (PD) is quantitatively assessed using the Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), a well-established clinical tool. Objective and efficient PD gait assessment is crucial for developing interventions to slow or halt its advancement. Skeleton-based PD gait MDS-UPDRS score estimation has attracted increasing interest in improving diagnostic efficiency and objectivity. However, previous works ignore the important cross-spacetime dependencies between joints in PD gait. Moreover, existing PD gait skeleton datasets are very small, which is a big issue in deep learning-based gait studies. In this work, we collect a sizable PD gait skeleton dataset by multi-view Azure Kinect sensors. The collected dataset contains 102 PD patients and 30 healthy older adults. In addition, gait data from 16 young adults (aged 24–50 years) are collected to further examine the effect of age on PD gait assessment. For skeleton-based automatic PD gait analysis, we propose a novel cross-spatiotemporal graph convolution network (CST-GCN) to learn complex features of gait patterns. Specifically, a gait graph labeling strategy is designed to assemble and group cross-spacetime neighbors of the root node according to the spatiotemporal semantics of the gait skeleton. Based on this strategy, the CST-GCN module explicitly models the cross-spacetime dependencies among joints. Finally, a dual-path model is presented to realize the modeling and fusion of spatial, temporal, and cross-spacetime gait features. Extensive experiments validate the effectiveness of our method on the collected dataset.

A method of designing and fabricating substrate-free Au/SiNx/Au metafilms as the terahertz (THz) absorber of metamaterial focal plane arrays (MFPA) is reported. The absorption was investigated by the finite integration method simulation and new explicit functions. The substrate-free structure was well fabricated by microelectromechanical system (MEMS) technology. The frequency-dependent absorption of MFPA was measured by THz time-domain spectroscopy (THz-TDS) system. It exhibits an extremely high absorptance of 98.7% at 1.36 THz. The absorption characteristic shows an asymmetric profile, which is well fitted with an Asymmetric Double Sigmoidal (Asym2sig) model. Our results show that the Au/SiNx/Au metafilms have potential in optical readout THz real-time imaging, and highly sensitive sensing applications.

A broadly tunable erbium-doped fiber ring laser is proposed and demonstrated based on the tapered polarization maintaining fiber (PMF) Sagnac interferometer, in which the Sagnac and intermodal interferences are superimposed to generate one localized peak over a wide wavelength range in its transmission spectrum. By heating the tapered PMF, the localized peak may be discretely tuned with the temperature at the step, depending on the intermodal interference. Tunability may become continuous when additional stress is exerted longitudinally on the tapered PMF. The tapered PMF Sagnac interferometer is inserted into the laser cavity to achieve broadly and continuously tunable output. Specifically, by optimizing the PMF length and its tapering section to obtain proper channel intervals of the Sagnac and intermodal interference, the lasing wavelength is continuously tuned over 60 nm covering from 1565.1 nm to 1625.2 nm with sidemode suppression ratio higher than 50 dB and power uniformity better than 1 dB. The tuning responses to temperature and axial stress are both linear with sensitivity of −1.1 nm/°C and −29.4 pm/μϵ. Most importantly, the temperature and axial stress affect the Sagnac and intermodal interferences, respectively, which makes it convenient to set the lasing wavelength beforehand during operation.

To improve the performance of infrared (IR) detectors, a novel air Fabry-Perot (FP) microcavity with high IR absorption has been studied. Based on the theory of FP cavity, the model of air FP microcavity has been proposed. Its materials have been selected through optical simulation and experimental verification. Then, the optical property and structural stress of the FP cavity have been simulated by finite difference time domain method and finite-element method. In the experiment, the test structure of air FP cavity is fabricated to verify the theoretical results. According to the experimental results, the IR absorption of this structure can reach to 85%. In addition, the application of the air FP microcavity can improve the performance of IR detector obviously. [ABSTRACT FROM PUBLISHER]