X频段八波束接收组件的设计与实现

针对X频段多波束有源相控阵系统的高集成、小型化、多波束等需求,设计了一款高集成、小型化的瓦片式八波束接收组件,该组件基于多层印制板技术,纵向实现了众多有源器件以及八套波束合路网络高密度布局,实现了组件的高集成化;针对组件的八波束合成需求,基于Wilkinson功分器的形式设计了一款小型化的高效合路网络,在7.5-9 GHz范围内,其插入损耗小于13 dB,端口间隔离度小于-20 dB,输出驻波比小于1.2,通道间幅相一致性良好;为降低组件内部信号的传输损耗,对组件内部的垂直互联结构进行了建模分析,得到不同结构参数对其传输性能的影响,通过优化结构参数的方法实现信号的低损耗传输。在此基础上对组件进行了加工实现,经测试,在7.5-9 GHz范围内,组件输出通道增益大于18 dB,输出驻波比小于1.5,通道间相位一致性小于±5°,尺寸仅有80 mm × 80 mm × 7.66 mm。     

多层斜网成形器的分类与选用

多层斜网成形器主要用于抄造分层结构特种纸,也适用于高定量及难脱水纤维纸品生产,并可作为合理用料、节约资源的纸品成形设备。     

Evolutions of stress and microstructure in multilayer ferroelectric actuators under different temperature environments

The multilayer ferroelectric actuator (MFA) with electrodes is an important smart structure and it has found wide application in engineering. Under the applied electric–elastic loads, the local stress concentration will be intensified near the tips of electrodes, and it finally may lead to the failure of the MFA. On the other hand, the temperature-dependent behavior of ferroelectrics results in the novel evolutions of local stresses and microstructure in the MFA under different temperature environments. In this work, the different temperature-induced nonlinear behavior and electroelastic field concentration around the electrode tip in the MFA is studied based on a phase-field approach containing the time-dependent Ginzburg–Landau equation. Using three-dimensional nonlinear finite element method, the temperature-induced domain switching behavior of the MFA and the evolution of the local stress near the electrode tips are simulated under different loadings and temperatures. It is found that the maximum tensile stress ahead of the electrode tip increases as the temperature increases from room temperature to a critical temperature. However, over the critical temperature, the stress decreases significantly due to the ferroelectric–paraelectric phase transition, which implies that by optimizing the environmental temperature, the local stress concentrations can be controlled.     

多层叠合医用非织造布透气性的理论研究

根据均匀多孔介质中的层流运动理论 ,推导出多层不同特性叠合非织造布透气性与单层非织造布透气性的关系 ,相对于此前的文献结论具有更广的适用性 ,将有助于新型医用非织造布的研制以及多层不同特性叠合非织造布在过滤功能方面的应用。     

偏压下弛豫型铁电陶瓷有效介电系数稳定方法的研究

本研究利用调整有效介电常数的互补公式     

AlN/W多层体共烧过程中的应力

研究了１８５０℃高温烧结ＡｌＮ／Ｗ多层体烧结应力状态和产生原因,结果表明ＡｌＮ与Ｗ在１８５０℃共烧时,不同阶段烧结应力状态有所不同,在升温阶段,Ｗ层受平面拉应力作用,Ｗ层烧结速率降低,导致表面Ｗ膜内存在的大量空洞,而内部Ｗ布线受到径向拉应力的作用,在保温阶段,与表面Ｗ焊盘接触的ＡｌＮ受到拉应力的作用,与内部Ｗ线接触的ＡｌＮ受到环向拉应力的作用,由于环向拉应力的存在,导致ＡｌＮ的烧结速度帮烧结密度显     

铜/钴纳米多层膜的电化学制备及表征

纳米金属多层膜由于其巨磁电阻性能而受到人们的重视。采用双脉冲控电位技术在单晶硅上沉积铜／钴纳米多层膜。测量了电沉积过程中的阴极极化曲线及电流－时间曲线，确定了沉积电位；利用扫描电子显微技术及X射线衍射技术观察了沉积层的断面形貌及晶体结构。结果表明，沉积层结构清晰、连续，各子层厚度均匀。     

Chaotic mixing behavior of non-Newtonian fluid intensified by multilayer rigid-flexible impeller induced flow field interface instability

The traditional multilayer rigid impeller has large dead zone for the mixing of pseudoplastic non-Newtonian fluid, stable flow field interface and low mixing efficiency. A method for enhancing the chaotic mixing of non-Newtonian fluid by multilayer rigid-flexible impeller induced flow field interface instability was proposed. In the experiment, sodium carboxymethylcellulose was used as the non-Newtonian fluid system. The power characteristics were measured by the torque sensor. The mixing time was determined by the acid-base neutralization and decolorization method. The largest Lyapunov exponents were calculated by using Matlab software programming. The chaotic characteristics and mixing performance in the mixing process are analyzed. The results show that when the combination mode was RF-(PBTD+PBTD+DT), the impeller arrangement mode θ=60°, and the flexible sheet length installation ratio r=0.8, 1.2, the degree of chaos was higher and the mixing performance was better. Multilayer rigid-flexible impeller can generate multiple spiral flows, and realize the flow field interface instability under the disturbance frequency difference of the flexible sheet between the layers, the stirring dead zone was reduced, and the system enters a chaotic state at a lower speed (when the multilayer rigid-flexible impeller system N>88 r/min, LLE>0; when the multilayer rigid impeller system N>125 r/min, LLE>0). At the same speed, the mixing rate and power per unit volume of the multilayer rigid-flexible combined impeller are higher than that of the multilayer rigid impeller, but the mixing energy per unit volume is approximately the same.     

Analytical solution for transient temperature and thermal stresses within convective multilayer disks with time-dependent internal heat generation,Part II: Applications

This work investigates the analytical solution for transient temperature and thermal stresses within three circular geometries. First, the transient temperature and thermal stresses within a composite disk are addressed. Then, two examples regarding transient temperature and thermal stresses throughout circular heaters are analyzed. Pulsed and sinusoidal internal heat generations are incorporated into the second and third examples, respectively. For the composite hollow-disk example, merely the separation of variables method (SVM) is used to overcome the energy partial differential equation. For the other two examples, the combination of the SVM and Duhamel's theorem are adopted to solve the partial differential equations. Accordingly, assuming plane stress formulation, the transient thermal stresses within structures are obtained.     

Melt processing and characterization of polyvinyl alcohol and polyhydroxyalkanoate multilayer films

Multilayer films for food packaging applications composed of polyvinyl alcohol (PVOH) as the core layer and polyhydroxyalkanoate (PHA) as the outer skin layers were produced by the co‐extrusion process. Rheological properties of PVOH and PHA were performed and analyzed before co‐extruding into a cast film. Analysis of the rheological data indicated the processing temperatures and grades of the PVOH and PHA polymers that would produce similar viscosity and melt flow properties. To improve adhesion of the layers, PHA was grafted with maleic anhydride using a dicumyl peroxide initiator to provide a tie layer material, which improved the peel strength of the PHA and PVOH layers by over 2×. Oxygen transmission rate (OTR) testing showed that the multilayer sample provided an OTR of 27 cc/m²‐day at 0% relative humidity (RH) and rates of 41 and 52 cc/m²‐day at relative humidity values of 60% and 90% RH, respectively. This indicates significant barrier performance enhancement over monolayer PVOH that provided an OTR of 60 cc/m²‐day at 0% RH and 999 cc/m²‐day at 60% RH. Biodegradation testing of the films in the marine environment showed that both the unmodified and maleated PHA polymers displayed high levels of mineralization, whereas the PVOH material did not. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013