Search

This paper presents novel cascaded channel estimation techniques for an intelligent reflecting surface-aided multiple-input multiple-output system. Motivated by the channel angular sparsity at higher frequency bands, the channel estimation problem is formulated as a sparse vector recovery problem with an inherent Kronecker structure. We solve the problem using the sparse Bayesian learning framework which leads to a non-convex optimization problem. We offer two solution techniques to the problem based on alternating minimization and singular value decomposition. Our simulation results illustrate the superior performance of our methods in terms of accuracy and run time compared with the existing works.

Objective To analyze the influencing factors for tracheostomy decannulation in patients with prolonged disorders of consciousness. Methods Clinical data of 59 cases with prolonged disorders of consciousness and having undergone tracheotomy in Guangdong Provincial Work Injury Rehabilitation Hospital from January 2019 to October 2020 were collected and retrospectively analyzed in this study. The patients were divided into extubation group (n=30) and non-extubation group (n=29). Age, cause of disease, duration of diseases (time from onset to extubation), duration of tracheostomy, total score and scores of functional mobility and language in Coma Recovery Scale-Revised (CRS-R), airway clearance by coughing, amount of expectation (evaluated by bronchofiberscopy), laryngeal edema and tracheal stenosis were analyzed to assess their relationships with tracheostomy decannulation. Results There were no statistical differences in age, gender, cause of disease, duration of diseases and average duration of tracheal intubation between the 2 groups. The extubation group had significantly higher total score of CRS-R, larger proportions of those with the score of functional mobility ≥3 and that of language ≥1, better airway clearance by coughing, milder laryngeal edema, lower proportion of residual expectation grade ≤l, and lower incidence of tracheal stenosis when compared with the non-exubation group (all P < 0.05). Logistic regression analysis showed that tracheal obstruction (P=0.001), abnormal salivary secretion (P=0.001) and CRSR-R score (P=0.036) were significant factors influencing extubation. Conclusion Tracheostomy decannulation is closely related to duration of disease, conscious status, cough reaction, laryngeal edema, amount of phlegm, and airway stenosis

We systematically investigate the influence of annealing effect on terahertz (THz) generation from CoFeB based magnetic nanofilms driven by femtosecond laser pulses. Three times enhancement of THz yields are achieved in W/CoFeB through annealing effect, and double boosting is obtained in Pt/CoFeB. The mechanism of annealing effect originates from the increase of hot electron mean free path induced by crystallization, which is experimentally corroborated by THz transmission measurement on time-domain spectroscopy. Comparison studies of the thickness dependent THz efficiency after annealing are also implemented, and we eventually conclude that annealing and thickness optimization are of importance for scaling up THz intensity. Our observations not only deepen understanding of the spintronic THz radiation mechanism but also provide normal platform for high speed spintronic opto-electronic devices., Comment: 14 pages, 4 figures