Analysis for Transmission of Composite Structure with Graphene Using Equivalent Circuit Model

A simple analytical method is presented to analyze the transmission of electromagnetic plane waves through multilayer stacked composite two-dimensional （2D） structures at microwave frequencies. Unlike the traditional structure, high impedance surface with graphene sheet is proposed. The structure includes graphene and thin metal patches and meshes. Simple analytical formulas are introduced for the surface impedance of graphene and for the grid impedance of electrically dense arrays of metal square patches or strips. The result of transmission proper- ties is based on the dynamic tunable model of the high impedance surface, which considers the surface conductivity of graphene layer. The transmission coefficient obtained by using the equivalent circuit method is validated against full-wave numerical simulations. The considered equivalent circuit method can be useful in the design of graphene tunable planar devices.     

Lawrence-Gurney模型对于激光驱动飞片的适用性分析

Lawrence-Gurney模型给出了求解激光驱动飞片速度的方程组。文章从理论和试验两个方面对Lawrence-Gurney模型的适用性进行了分析,发现该模型不能较好地描述厚度为10μm以下飞片的驱动过程。主要原因是Lawrence-Gurney模型对激光与飞片的具体相互作用过程进行了简化假设,依据能量守恒和动量守恒定律建立数学方程组,而这些假设条件和近似求解条件对于厚度小于10μm的飞片均不能很好地成立,导致对飞片速度、能量耦合效率、冲量耦合系数和飞片烧蚀深度随激光能量变化的理论预估结果与试验结果偏差较大,需要进行修正。     

新型高压大功率开关功率放大器的研制

文章针对大型电动振动台的需求,提出了一种新型高压大功率开关功率放大器的设计方法,采用绝缘栅双极性晶体管（IGBT）全桥逆变电路和脉宽调制（PWM）集成控制电路来实现,研制出的样机调试取得良好效果。文中还对大功率IGBT驱动电路、单极性倍频PWM调制和输出滤波器进行了详细的讨论。     

微波散射计数字接收机DDC的设计与实现

微波散射计是一种用于测量目标后向散射系数的有源微波遥感器。文章介绍了作为微波散射计重要部件之一的数字化中频接收机,指出数字下变频在微波散射计数字化中频接收机的数字化和软件化过程的作用。根据微波散射计数字化中频接收机工作机理与数字下变频原理,结合Matlab算法仿真技术,设计并实现了基于FPGAIP核的数字下变频。仿真与实测结果表明：基于FPGAIP核设计实现的数字下变频能够满足微波散射计数字化中频接收机性能指标要求,并且具有灵活性、通用性、修改参数方便等特点。     

尾缘吹气式火焰稳定器试验研究

本文提出了一种新型火焰稳定器—尾缘吹气式火焰稳定器,它具有流线形头部,槽宽小,尾缘吹气并供油,不加力时流阻很小,加力时吹气扩大回流区,是一种机械与气动稳定结合的稳定器。对该稳定器进行了试验研究,得到流阻损失、贫熄边界、燃烧效率等性能的初步结果,表明该稳定器具有优越性,并有希望用于加力燃烧室。     

用螺桨-吊舱相关法设计和分析桨扇

本文用螺桨-吊舱相关分析法对桨扇进行设计和分析。用曲线升力线代表桨叶,并且考虑吊舱存在的影响;方法采用尾迹位于流面上的假定。对叶尖段进行跨音修正,对根部应用叶栅最佳损失攻角加以考虑。设计和分析的结果与文献〔2〕的计算和试验结果作部分比较,证明了本法的合理性和有效性,可以应用于桨扇的初步设计和性能分析中。     

30Cr Mn Si Ni 2A钢在飞机环境下的腐蚀疲劳裂纹扩展研究

 <正> 1.引言 飞机结构的许多部位同时受交变循环应力和环境介质的作用,腐蚀介质对疲劳裂纹     

涡轮盘材料低周叠加高周复合疲劳断裂特性研究

航空发动机的载荷谱,包含起飞和着陆间的各种巡航状态,可简化为梯形波表示。在涡轮盘和压气机盘的关键区域,如连接叶片的盘缘,离心力和热应力的变化,以起动——停车作为一个工作循环,称为主循环,是低周疲劳的主要损伤源。在载荷保持期间(巡航状态),局部高应力区可能产生蠕变或应力松弛,实际上还会有低幅值高周振动(称为次循环)应力叠加在主循环上,简化载荷谱如图1所示。这种状态除航空发动机外,在多数动力机械如原子能装置、内燃机等都可能发生。在评定承受低周叠加高周复合作用的构件及材料疲劳断裂性能时,应该考虑高周损伤的重要作用。本文介绍近年来所作初步研究的部分结果。      

具有电磁约束阻尼层梁的振动主动控制研究计算(英文)

This paper investigates vibration control of beam through electro-magnetic constrained layer damping （EMCLD） which consists of electromagnet layer, permanent magnet layer and viscoelastic damping layer. When the coil of the electromagnet is electrified with proper control strategy, the electromagnet can exert magnetic force opposite to the direction of structural deformation so that the structural vibration is attenuated. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the system are obtained using Hamilton＇s Principle and then reduced with the assumed-mode method. A simulation on vibration control of a cantilever beam is conducted under the velocity proportional feedback to demonstrate the energy dissipation capability of EMCLD, and the beam system with the same parameter is experimented. The results of experiment and simulation are compared and the results show that the EMCLD is an effective means for suppressing modal vibration. The results also indicate that the beam system has better control performance for larger control current. The EMCLD method presented in this paper provides an applicable and efficient tool for the vibration control of structures.