The effects of migratory bird population in a nonautonomous eco-epidemiological model

In ecology the disease in the rare migratory bird population plays an important role in controlling the dynamical behavior of system. In this paper, we investigate a nonautonomous two species (migratory bird population and economical bird population) competitive model with saturation incidence and artificially harvesting and study the dynamical changes that take place due to the introduction of a disease by migratory birds. Under the reasonable assumptions, sufficient conditions for the permanence and extinction of the disease are obtained. Moreover, the global attractivity of the model is discussed by constructing a Liapunov function. To substantiate our theoretical results, extensive numerical simulations are performed for a hypothetical set of parameter values.     

Quercetin and Rutin as Modifiers of Aphid Probing Behavior

Rutin and its aglycone quercetin occur in the fruits, leaves, seeds, and grains of many plant species and are involved in plant herbivore interactions. We studied the effect of the exogenous application of rutin and quercetin on the probing behavior (= stylet penetration activities in plant tissues) of Acyrthosiphon pisum on Pisum sativum, Myzus persicae on Brassica rapa ssp. pekinensis, and Rhopalosiphum padi on Avena sativa using the electrical penetration graph technique (EPG = electropenetrography). The reaction of aphids to quercetin and rutin and the potency of the effect depended on aphid species, the flavonol, and flavonol concentration. Quercetin promoted probing activities of A. pisum within non-phloem and phloem tissues, which was demonstrated in the longer duration of probes and a trend toward longer duration of sap ingestion, respectively. M. persicae reached phloem in a shorter time on quercetin-treated B. rapa than on the control. Rutin caused a delay in reaching sieve elements by A. pisum and deterred probing activities of M. persicae within non-phloem tissues. Probing of R. padi was not affected by quercetin or rutin. The potency of behavioral effects increased as the applied concentrations of flavonols increased. The prospects of using quercetin and rutin in plant protection are discussed.     

基于神经网络方法的鸟撞飞机风挡冲击载荷反演

以鸟撞实验中传感器实测信号为基础,结合有限元正问题计算方法与神经网络理论,构造小波动态延时反馈神经网络,并详细分析了该网络的结构参数、对比了网络单点应变输入法、两点应变输入法以及三点(多点)应变输入法的训练效率与反演精度．构造的神经网络可以高精度地反演出鸟撞飞机风挡过程中冲击载荷时间历程,同时具有较高的抗干扰能力,且训练过程平稳、训练效率高．根据已有的研究成果,提出了鸟撞实验应变传感器建议布置,可以在满足实验测量要求的基础上简化实验过程,提高实验效率．     

鸟体姿态对结构抗鸟撞性能的影响

低于现行标准规定能量的大量鸟撞事故中,航空结构仍然发生实质性破坏的情况,说明只考虑鸟体的质量和速度不足以保证飞机安全。本文中针对弹性平板、雷达罩及机翼前缘等飞机典型结构,开展了不同姿态鸟体的鸟撞分析研究。分析结果发现,鸟体姿态对结构的抗鸟撞性能有比较显著的影响,不同的结构特点反映的响应规律也不同:对吸能结构,姿态角越大,吸收的能量越多,被保护的结构就越安全;而对承力结构,姿态角越大,高应力区域越大,结构就越危险。因此,在结构的抗鸟撞安全性评估中,除了完成特定姿态鸟体的鸟撞实验,针对危险工况还应通过数值分析评估不同鸟体姿态的结构撞击响应,进一步确保结构的抗鸟撞能力。