A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on ...A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on feedback and feed-forward channels simultaneously with limited resource.The attacker aims at degrading the UAV CPS's estimation performance to the max while keeping stealthiness characterized by the Kullback-Leibler(K-L)divergence.The attacker is resource limited which can only attack part of sensors,and the attacked sensor as well as specific forms of attack signals at each instant should be considered by the attacker.Also,the sensor selection principle is investigated with respect to time invariant attack covariances.Additionally,the optimal switching attack strategies in regard to time variant attack covariances are modeled as a multi-agent Markov decision process(MDP)with hybrid discrete-continuous action space.Then,the multi-agent MDP is solved by utilizing the deep Multi-agent parameterized Q-networks(MAPQN)method.Ultimately,a quadrotor near hover system is used to validate the effectiveness of the results in the simulation section.展开更多
The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle ho...The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle hole were analyzed.Results show that the inner conicity of nozzle hole inhibits the development of cavitation phenomena,and increases the injection rate.While the outer conicity of nozzle hole promotes the diffusion of cavita-tion,leading to reductions of the liquid volume fraction of the nozzle outlet and the local flow resistance of the nozzle hole.The sensitivity of cycle fuel mass to inner-cone nozzle hole is stronger than that of the outer-cone noz-zle,especially at the smaller hole conicity.The increase of injection pressure enhances the sensitivity of the injection characteristics to the nozzle hole structure,in which inner-cone nozzle has higher sensitivity coefficient than the outer-cone nozzle hole.However,the increase of injection pressure aggravates the offset of liquid jet to the nozzle axis of the outer-cone nozzle hole.With the increase of the inner conicity of nozzle,the sensitivity of the injection characteristics to the entrance radius of the hole decreases.With the increase of the outer conicity of nozzle hole,the sensitivity of the injection characteristics to the entrance radius of the hole increases.展开更多
目的:展现注射用益气复脉治疗心力衰竭领域证据分布情况。方法:检索CBM、CNKI、万方、VIP、Cochrane Library、PubMed、Embase及Web of Science等相关数据库,并查询中国临床试验注册中心、ClinicalTrials.gov,收集注射用益气复脉治疗心...目的:展现注射用益气复脉治疗心力衰竭领域证据分布情况。方法:检索CBM、CNKI、万方、VIP、Cochrane Library、PubMed、Embase及Web of Science等相关数据库,并查询中国临床试验注册中心、ClinicalTrials.gov,收集注射用益气复脉治疗心力衰竭疾病相关的临床研究、系统评价和指南共识,通过证据图谱研究方法采用表格展示文献占比、样本量、合并病症及系统评价的质量评价等数据,饼状图展示研究类型比例分布,折线图描述发表趋势,气泡图展现证据分布情况。结果:注射用益气复脉治疗心力衰竭发文量整体处于稳步发展阶段,目前的临床研究以小样本、单中心、短时程的随机对照试验(RCT)为主要研究对象,样本量多为60~100人,干预时长大多为14 d,基础疾病以冠心病为主。临床研究证据倾向于支持注射用益气复脉联合常规西药治疗心力衰竭在改善患者心功能和生活质量方面发挥疗效,但也存在研究整体质量较低,临床试验设计不合理、样本量较小、结局指标选择不完善、某些结局指标国际认可度较低、缺乏对长期结局的报告、随机对照试验和系统评价的方法学整体质量偏低等问题。结论:未来应开展更多大样本、多中心临床随机对照试验研究,获得更高级别的循证医学证据,充分展示中医治疗优势,推动中医心病学和循证医学的共同发展。展开更多
文摘A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on feedback and feed-forward channels simultaneously with limited resource.The attacker aims at degrading the UAV CPS's estimation performance to the max while keeping stealthiness characterized by the Kullback-Leibler(K-L)divergence.The attacker is resource limited which can only attack part of sensors,and the attacked sensor as well as specific forms of attack signals at each instant should be considered by the attacker.Also,the sensor selection principle is investigated with respect to time invariant attack covariances.Additionally,the optimal switching attack strategies in regard to time variant attack covariances are modeled as a multi-agent Markov decision process(MDP)with hybrid discrete-continuous action space.Then,the multi-agent MDP is solved by utilizing the deep Multi-agent parameterized Q-networks(MAPQN)method.Ultimately,a quadrotor near hover system is used to validate the effectiveness of the results in the simulation section.
文摘The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle hole were analyzed.Results show that the inner conicity of nozzle hole inhibits the development of cavitation phenomena,and increases the injection rate.While the outer conicity of nozzle hole promotes the diffusion of cavita-tion,leading to reductions of the liquid volume fraction of the nozzle outlet and the local flow resistance of the nozzle hole.The sensitivity of cycle fuel mass to inner-cone nozzle hole is stronger than that of the outer-cone noz-zle,especially at the smaller hole conicity.The increase of injection pressure enhances the sensitivity of the injection characteristics to the nozzle hole structure,in which inner-cone nozzle has higher sensitivity coefficient than the outer-cone nozzle hole.However,the increase of injection pressure aggravates the offset of liquid jet to the nozzle axis of the outer-cone nozzle hole.With the increase of the inner conicity of nozzle,the sensitivity of the injection characteristics to the entrance radius of the hole decreases.With the increase of the outer conicity of nozzle hole,the sensitivity of the injection characteristics to the entrance radius of the hole increases.
文摘目的:展现注射用益气复脉治疗心力衰竭领域证据分布情况。方法:检索CBM、CNKI、万方、VIP、Cochrane Library、PubMed、Embase及Web of Science等相关数据库,并查询中国临床试验注册中心、ClinicalTrials.gov,收集注射用益气复脉治疗心力衰竭疾病相关的临床研究、系统评价和指南共识,通过证据图谱研究方法采用表格展示文献占比、样本量、合并病症及系统评价的质量评价等数据,饼状图展示研究类型比例分布,折线图描述发表趋势,气泡图展现证据分布情况。结果:注射用益气复脉治疗心力衰竭发文量整体处于稳步发展阶段,目前的临床研究以小样本、单中心、短时程的随机对照试验(RCT)为主要研究对象,样本量多为60~100人,干预时长大多为14 d,基础疾病以冠心病为主。临床研究证据倾向于支持注射用益气复脉联合常规西药治疗心力衰竭在改善患者心功能和生活质量方面发挥疗效,但也存在研究整体质量较低,临床试验设计不合理、样本量较小、结局指标选择不完善、某些结局指标国际认可度较低、缺乏对长期结局的报告、随机对照试验和系统评价的方法学整体质量偏低等问题。结论:未来应开展更多大样本、多中心临床随机对照试验研究,获得更高级别的循证医学证据,充分展示中医治疗优势,推动中医心病学和循证医学的共同发展。
