No abstract

The nanosecond pulsed discharge in a gas–liquid mixture of a Venturi tube with the injection of oxygen was numerically and experimentally investigated. It was found that the density of the gas–liquid mixture close to the electrode at the water inlet is significantly lower than that at the water outlet. The lowest void fraction close to the water outlet is higher than 50%. When the oxygen flow rises from 0.5 SLPM to 3 SLPM, the flow mode changes from the bubble flow to the annular flow. If the applied voltage is kept at 45 kV in amplitude, the probability of the breakdown increases with the water flow and it reaches 100% as the water flow rises to 9.5 L/min. Since the pulsed breakdown voltage changes from shot to shot under the same experimental conditions, the distribution of 200 breakdown voltages was measured and the median in the distribution of the probability density, defined as U50, was determined. The curve of the U50 as a function of the oxygen flow takes the shape of “V,” similar to that of the Paschen curve obtained from the gas breakdown. An abnormal polarity effect in the breakdown voltage was observed, and the reason was given. By combining the results from the experiment with the numerical simulation, the spatial distribution of the reduced field at the time of breakdown was determined. The oxygen flows not higher than 0.5 SLPM are the better choice for getting a reduced field higher than 500 Td.

Background: Stroke survivors often experience abnormal posture control, which affects balance and locomotion. The ankle strategy is important in maintaining static balance. Prolonged spasticity may result in biomechanical changes at the ankle joint, which may cause balance disorders. The intelligent stretching device may decrease the stiffness of the ankle and improve balance. The purpose of this study was to investigate the effects of robot-aided ankle rehabilitation of stroke survivors with ankle spasticity and the correlations between biomechanical properties and balance in these patients. Methods: Twenty inpatients post stroke with ankle spasticity performed 20 minutes of stretching treatment for 2 weeks. The study group used a rehabilitation robot to stretch the spastic ankle plantar flexors under intelligent control and the control group received manual stretching. Outcome measures included biomechanical, clinical evaluations and Pro-Kin balance test. Results: After training, significant improvements were found in both groups in the active range of motion, muscle strength, Berg Balance Scale, Fugl-Meyer Motor Assessment of Lower Extremity, Postural Assessment Scale for Stroke Patients, 6-minute walk test, and Modified Barthel Index (P<0.05); significant decreases were found in the study group in dorsiflexion stiffness, Modified Ashworth Scale, trajectory lengths, elliptical trajectory, standard deviation medial/lateral, average speed forward/backward with eyes closed, and standard deviation forward/backward with eyes open (P=0.001, P=0.037, P=0.028, P=0.019, P=0.016, P=0.001, and P=0.033, respectively); dorsiflexion stiffness was positively correlated with the Pro-Kin balance test outcomes: ellipse area, trajectory length, average speed forward/backward, average speed medial/lateral with eyes open ( =0.352, P=0.026; =0.522, P=0.001; =0.045, P=0.004; =0.433, P=0.005, respectively); dorsiflexion stiffness was correlated with the Modified Ashworth Scale ( =0.265, P=0.041); the study group improved significantly more than the control group in the activities of daily living after training (P =0 .017). Conclusions: The results suggested that robot-aided ankle rehabilitation had a positive effect on the biomechanical properties of the spastic ankle, and it may be feasible to improve balance post-stroke. Ankle dorsiflexion stiffness affected balance poststroke significantly; it may be a sensitive indicator for evaluating balance. Trial registration: www.chictr.org.cn ChiCTR1900022128. Registered 21 February 2020. Retrospectively registered.

No abstract

Background: Stroke survivors often experience abnormal posture control, which affects balance and locomotion. The ankle strategy is important in maintaining static balance. Prolonged spasticity may result in biomechanical changes at the ankle joint, which may cause balance disorders. The intelligent stretching device may decrease the stiffness of the ankle and improve balance. The purpose of this study was to investigate the effects of robot-aided ankle rehabilitation of stroke survivors with ankle spasticity and the correlations between biomechanical properties and balance in these patients. Methods: Twenty inpatients post stroke with ankle spasticity performed 20 minutes of stretching treatment for 2 weeks. The study group used a rehabilitation robot to stretch the spastic ankle plantar flexors under intelligent control and the control group received manual stretching. Outcome measures included biomechanical, clinical evaluations and Pro-Kin balance test. Results: After training, significant improvements were found in both groups in the active range of motion, muscle strength, Berg Balance Scale, Fugl-Meyer Motor Assessment of Lower Extremity, Postural Assessment Scale for Stroke Patients, 6-minute walk test, and Modified Barthel Index (P<0.05); significant decreases were found in the study group in dorsiflexion stiffness, Modified Ashworth Scale, trajectory lengths, elliptical trajectory, standard deviation medial/lateral, average speed forward/backward with eyes closed, and standard deviation forward/backward with eyes open (P=0.001, P=0.037, P=0.028, P=0.019, P=0.016, P=0.001, and P=0.033, respectively); dorsiflexion stiffness was positively correlated with the Pro-Kin balance test outcomes: ellipse area, trajectory length, average speed forward/backward, average speed medial/lateral with eyes open ( =0.352, P=0.026; =0.522, P=0.001; =0.045, P=0.004; =0.433, P=0.005, respectively); dorsiflexion stiffness was correlated with the Modified Ashworth Scale ( =0.265, P=0.041); the study group improved significantly more than the control group in the activities of daily living after training (P =0 .017). Conclusions: The results suggested that robot-aided ankle rehabilitation had a positive effect on the biomechanical properties of the spastic ankle, and it may be feasible to improve balance post-stroke. Ankle dorsiflexion stiffness affected balance poststroke significantly; it may be a sensitive indicator for evaluating balance. Trial registration: www.chictr.org.cn ChiCTR1900022128. Registered 21 February 2020. Retrospectively registered.