Endurance-test and theoretical prediction of a rare earth nanocathode for the applied field magnetoplasmadynamic thruster

The erosion loss of cathode is essential for the lifetime of magnetoplasmadynamic thruster(MPDT).In this work,an endurance test system for MPDT cathodes was designed and developed,and the erosion characteristics,erosion rate and erosion mechanism of the cathode were studied using the system under vacuum condition.The WCe20 hollow cathode was selected to carry out the long-term erosion of 540 h with the argon propellant supply flow rate of40 ml min^(-1),the input current of 25 A,and the central magnetic field intensity of 96 Gs.In order to predict the theoretical service life of cathode,a steady state erosion numerical model was established.The calculation results show that the total erosion rate of sputtering and evaporation is 11.58 mg h^(-1),which is slightly smaller than the test data of the average cathode corrosion rate of 12.70 mg h^(-1) in the experiment,because the experimental value includes start-up erosion rate.

脑弓形虫病一例

1病例报告患者男,59岁。主因＂发热、头痛2周,言语不清2d＂入院。2周前出现发热,体温波动于37.2~37.5℃,未予治疗,后出现右侧颞枕部发作性胀痛,每次发作持续约20min,每天发作次数不定,伴视物模糊,偶有视物成双及耳鸣。入院2d前出现言语含糊不清及音调减低。既往体健。