The ion thruster is an engine with high specific impulse for satellites and spacecrafts,which uses electric energy to boost the spacecraft.The ion optical system,also known as gate assemblies which consist of accelera...The ion thruster is an engine with high specific impulse for satellites and spacecrafts,which uses electric energy to boost the spacecraft.The ion optical system,also known as gate assemblies which consist of acceleration and screen grids,is the key component of the ion thruster.In this paper,the static mechanical properties of the C/C composite grids are evaluated based on the structural design.Representative volume element (RVE) is adopted to simplify the braded composite structure as a continuum material.The dynamical behavior of the 100 mm ion thruster optics in the launch environment (1000g shock-load) is numerically modeled and simulated with the half-sine pulse method.The impact response of the C/C and molybdenum gate assemblies on the stress distribution and deformation is investigated.The simulated results indicate that the magnitudes of the normal displacement of the composite grids subject to the uniformly distributed load are on the same level as molybdenum grids although the normal stiffness of the composite grids is much smaller.When subject to impact loading,the stress distribution in the C/C composite grids is similar to molybdenum grids while the stress magnitude is much smaller.This finding shows that the C/C gate assemblies outperform molybdenum grids and meet the requirement of long lifetime service in space travel.展开更多
Objective: To study the distribution of c fos oncogene expression within central nervous system (CNS) of the rat during halothane anesthesia. Methods: c-fos oncogene immunohistochemical technique (ABC method) was empl...Objective: To study the distribution of c fos oncogene expression within central nervous system (CNS) of the rat during halothane anesthesia. Methods: c-fos oncogene immunohistochemical technique (ABC method) was employed. Results: When halothane concentration was 0.75%,1.5%or2.0%, most of the Fos-like immunore- active neurons (FLNs) appeared in telencephalon, diencephalon and brain stem, including cerebral cortex, amygaloid nucleus, accumbens nucleus, lateral keptal nucleus. bed nucleus of the stria terminalis, field CA1 of Ammon’s horn, islands of Calleja, paraventricular thalamic nucleus, central medial thalamic nucleus, reuniens thalamic nucleus, rhomboid thalamic nucleus. ventral posterolateral thalamic nucleus, paraventricular hypothalamic nucleus(ventral part). periventricular hypothalamic nucleus, median preoptic nucleus, supraoptic nucleus, suprachiasmatic nucleus. medial and lateral habenular nucleus. midbrain periaqueductal gray and Edinger-Westphal nucleus.In the present stude. we have also found that the number of FLN registered stable increase along with the increaseof the concentration of halothane. Conclusion: It has been indicated that FLNs participate in the process ofhalothane anesthesia. which should necessitate and pave the way for a further study of the patterns of linkage andthe mechanism of interaction between functional nuclei.展开更多
基金Project supported by the National Key R&D Program of China(No.2018YFF01014200)the National Natural Science Foundation of China(Nos.11727804,11672347,and 51732008)
文摘The ion thruster is an engine with high specific impulse for satellites and spacecrafts,which uses electric energy to boost the spacecraft.The ion optical system,also known as gate assemblies which consist of acceleration and screen grids,is the key component of the ion thruster.In this paper,the static mechanical properties of the C/C composite grids are evaluated based on the structural design.Representative volume element (RVE) is adopted to simplify the braded composite structure as a continuum material.The dynamical behavior of the 100 mm ion thruster optics in the launch environment (1000g shock-load) is numerically modeled and simulated with the half-sine pulse method.The impact response of the C/C and molybdenum gate assemblies on the stress distribution and deformation is investigated.The simulated results indicate that the magnitudes of the normal displacement of the composite grids subject to the uniformly distributed load are on the same level as molybdenum grids although the normal stiffness of the composite grids is much smaller.When subject to impact loading,the stress distribution in the C/C composite grids is similar to molybdenum grids while the stress magnitude is much smaller.This finding shows that the C/C gate assemblies outperform molybdenum grids and meet the requirement of long lifetime service in space travel.
文摘Objective: To study the distribution of c fos oncogene expression within central nervous system (CNS) of the rat during halothane anesthesia. Methods: c-fos oncogene immunohistochemical technique (ABC method) was employed. Results: When halothane concentration was 0.75%,1.5%or2.0%, most of the Fos-like immunore- active neurons (FLNs) appeared in telencephalon, diencephalon and brain stem, including cerebral cortex, amygaloid nucleus, accumbens nucleus, lateral keptal nucleus. bed nucleus of the stria terminalis, field CA1 of Ammon’s horn, islands of Calleja, paraventricular thalamic nucleus, central medial thalamic nucleus, reuniens thalamic nucleus, rhomboid thalamic nucleus. ventral posterolateral thalamic nucleus, paraventricular hypothalamic nucleus(ventral part). periventricular hypothalamic nucleus, median preoptic nucleus, supraoptic nucleus, suprachiasmatic nucleus. medial and lateral habenular nucleus. midbrain periaqueductal gray and Edinger-Westphal nucleus.In the present stude. we have also found that the number of FLN registered stable increase along with the increaseof the concentration of halothane. Conclusion: It has been indicated that FLNs participate in the process ofhalothane anesthesia. which should necessitate and pave the way for a further study of the patterns of linkage andthe mechanism of interaction between functional nuclei.
