AbstractBackground: Duchenne muscular dystrophy (DMD) is a prevalent X-linked recessive muscle degeneration disorder that involves the gradual loss of functional muscle mass. The Phase Angle (PhA) can indicate changes in cell membrane integrity and intercellular space. It has been recognized as a valuable tool for assessing disease severity and predicting patient outcomes. However, there is limited research on the application of PhA in children with neuromuscular diseases, including DMD. Objective: More biological indicators are needed to reflect clinical progress in DMD children. We specifically examined the correlation between segmental PhAs and motor function and evaluated the effectiveness of segmental PhAs as a measure for assessing motor function in DMD children Methods:A retrospective longitudinal cohort study of 399 boys with DMD in West China Second University Hospital (2016-2023) was performed. The correlation between PhA and motor function were analyzed through spearman correlation analysis. The predictive value of PhA and PhA combining age for lower limb motor function loss was analyzed by ROC curve. Results: The time of peak of PhAs are earlier than NNSA score (peak at 6-7years old). TR-PhA reaches its peak at 6 years old, while other PhAs reaches its peak at 5-6 years old and subsequently declines over time. There was a significant correlation between PhAs and the NSAA score, with the strongest correlation observed in leg PhA (r=0.753, P<0.001). PhAs in legs demonstrate the strongest correlation and highest predictive value for lower limb motor function loss(AUC from 0.725 to 0.863). Additionally, PhAs combined with age had more excellent predictive ability for lower limb function loss than PhAs((AUC from 0.929 to 0.951). Conclusion: 1）The phase Angle increases first and then decreases with the progression of DMD disease; the phase Angle changes earlier than motor function and presents a good correlation, which is a sensitive index to predict the progression of DMD disease. PhA could serve as a simple, fast, and non-invasive marker to predict the loss of lower limb motor function in DMD children.
Icing experiments on three units of XP4-160 insulator string are conducted to reveal the influence of the crystallisation effect of conductive ions during phase transition on melting water conductivity and ice flashover voltage, and to analyse the motion of conductive ions and its spatial distribution. The influence of different parameters, such as freezing water conductivity, electric field and pollution, on crystallisation effect is examined and analysed. Results of the tests indicate that the melting water conductivity of the ice layer and icicles is considerably greater than that of freezing water, particularly for a polluted insulator, because of the crystallisation effect. The electric field has a significant influence on the crystallisation effect, that is, the melting water conductivity under a non-energised condition is higher than that under an energised condition. Finally, through 35 kV insulator flashover tests, the reason for the propagation of partial arcs over icicles is determined, and the flashover process is illustrated. The crystallisation effect during phase transition changes the ion distribution in a solid ice layer, thereby increasing water film conductivity, and is also a critical reason for the decline of ice flashover voltage.
In this paper, a model based on dynamic electric field analysis has been developed to predict the flashover voltage of the ice-covered HV insulators, under dc voltage. The potential and electric field calculation models before and after air gap breakdown are built respectively based on finite element method (FEM). The arc initiation process is determined based on the model before air gap breakdown. The critical applied voltage and leakage current to maintain an arc with certain length are obtained based on the electric field calculation model after air gap breakdown and the U-I characteristic of the arc. Moreover, the improved Hampton criterion has been employed to determine the critical flashover of the ice-covered insulator. The results obtained from the dynamic electric field analysis model have been compared with other mathematical and experimental results of other researchers and got a great agreement.
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