为迎接电动垂直起降航空器的到来,降低平均无故障时间,对电动垂直起降(electric vertical takeoff and landing,eVTOL)航空器的一般运行场景和系统构成做出了分析,并从人为因素、设备因素、环境因素和其他因素中提取了可能的失效诱因;...为迎接电动垂直起降航空器的到来,降低平均无故障时间,对电动垂直起降(electric vertical takeoff and landing,eVTOL)航空器的一般运行场景和系统构成做出了分析,并从人为因素、设备因素、环境因素和其他因素中提取了可能的失效诱因;构建了失控坠地和空中碰撞的贝叶斯网络,并依据所建网络和通过不同专家得到的概率值计算控制失效情况下失控坠地和中间事件发生概率,然后进行反向推断,推演事故发生主要诱因。结果表明:电动垂直起降航空器正常运行发生事故的概率为9.648×10^(-7),其中,控制失效、飞控系统断电/故障是事故主要诱因,计算结果可为电动垂直起降航空器安全运行防控提供依据。展开更多
Reactive oxygen species （ROS） in plant cell, including superoxide （O2^-）, hydrogen peroxide （H2O2）, and malondialdehyde （MDA）, are thought to be important inducible factors of cell apoptosis if excessively acc...Reactive oxygen species （ROS） in plant cell, including superoxide （O2^-）, hydrogen peroxide （H2O2）, and malondialdehyde （MDA）, are thought to be important inducible factors of cell apoptosis if excessively accumulated in cells. To elucidate the metabolic mechanism of ROS production and scavenging in anthers of the cytoplasmic male-sterile （CMS） cotton, CMS line, maintainer, and hybrid F1 anthers, were employed for studying the relationship between CMS and metabolism of ROS, by comparing ROS changes in the sterile and fertile anthers at different developmental stages. The results showed that during the abortion preliminary stage （sporogenous cell division stage）, anthers of CMS line had higher contents of O2^-, H2O2, and MDA than those of maintainer or hybrid F1. Simultaneously, the higher activities of superoxide dismutase （SOD）, catalase （CAT）, and peroxidase （POD） in scavenging ROS were measured in the anthers of the CMS line, indicating that an increase of ROS in anthers of abortion preliminary stage had an inducible effect on the antioxidant enzymes. But during the abortion peak of CMS anther （pollen mother cell meiosis stage）, on the one hand, contents of O2^-, H2O2, and MDA were extraordinarily high in CMS anthers, on the other hand, the activities of SOD, CAT, and POD were excessively low, which disrupted the balance between the production and elimination of ROS and led to pollen mother cells apoptosis at this stage. In the following two stages （uninucleate microspore stage and mature pollen stage）, the contents of O2^- and H2O2 in the aborted anthers were approximated to contents in the fertile anthers of the maintainer and hybrid F1. However, MDA contents were continuously raised and enzymic activities of SOD, CAT, and POD were consistently decreased in sterile anthers, which indicated that ROS still had harmful effects on the anthers after the apoptosis of the male cells. Excessive accumulation of O2^-, H2O2, and MDA and significant reduction of ROS scavengingenzyme activities were coinstantaneous with male cells apoptosis in the anthers of the cotton CMS line. But when the restorer gene was transferred into the CMS line, excessive production of ROS could be eliminated in the anthers of hybrid F1.展开更多
文摘为迎接电动垂直起降航空器的到来,降低平均无故障时间,对电动垂直起降(electric vertical takeoff and landing,eVTOL)航空器的一般运行场景和系统构成做出了分析,并从人为因素、设备因素、环境因素和其他因素中提取了可能的失效诱因;构建了失控坠地和空中碰撞的贝叶斯网络,并依据所建网络和通过不同专家得到的概率值计算控制失效情况下失控坠地和中间事件发生概率,然后进行反向推断,推演事故发生主要诱因。结果表明:电动垂直起降航空器正常运行发生事故的概率为9.648×10^(-7),其中,控制失效、飞控系统断电/故障是事故主要诱因,计算结果可为电动垂直起降航空器安全运行防控提供依据。
文摘Reactive oxygen species （ROS） in plant cell, including superoxide （O2^-）, hydrogen peroxide （H2O2）, and malondialdehyde （MDA）, are thought to be important inducible factors of cell apoptosis if excessively accumulated in cells. To elucidate the metabolic mechanism of ROS production and scavenging in anthers of the cytoplasmic male-sterile （CMS） cotton, CMS line, maintainer, and hybrid F1 anthers, were employed for studying the relationship between CMS and metabolism of ROS, by comparing ROS changes in the sterile and fertile anthers at different developmental stages. The results showed that during the abortion preliminary stage （sporogenous cell division stage）, anthers of CMS line had higher contents of O2^-, H2O2, and MDA than those of maintainer or hybrid F1. Simultaneously, the higher activities of superoxide dismutase （SOD）, catalase （CAT）, and peroxidase （POD） in scavenging ROS were measured in the anthers of the CMS line, indicating that an increase of ROS in anthers of abortion preliminary stage had an inducible effect on the antioxidant enzymes. But during the abortion peak of CMS anther （pollen mother cell meiosis stage）, on the one hand, contents of O2^-, H2O2, and MDA were extraordinarily high in CMS anthers, on the other hand, the activities of SOD, CAT, and POD were excessively low, which disrupted the balance between the production and elimination of ROS and led to pollen mother cells apoptosis at this stage. In the following two stages （uninucleate microspore stage and mature pollen stage）, the contents of O2^- and H2O2 in the aborted anthers were approximated to contents in the fertile anthers of the maintainer and hybrid F1. However, MDA contents were continuously raised and enzymic activities of SOD, CAT, and POD were consistently decreased in sterile anthers, which indicated that ROS still had harmful effects on the anthers after the apoptosis of the male cells. Excessive accumulation of O2^-, H2O2, and MDA and significant reduction of ROS scavengingenzyme activities were coinstantaneous with male cells apoptosis in the anthers of the cotton CMS line. But when the restorer gene was transferred into the CMS line, excessive production of ROS could be eliminated in the anthers of hybrid F1.
