RECURSIVENESS OF ZERO STRUCTURES FOR SYSTEM MATRICES OF INTERCONNECTED LINEAR SYSTEMS VIA MODULE THEORETIC TOOLS

The importance of the zeros of multwariable linear systems is well-knoiun in terms of measure obstructions to the controllability and the. observability. In this paper, a recursive decarnposi Am oj interconnected systems is outlined by taking into account the sequential structure of the connnections. The paper extends the, coordinate, module-theoretic studies from the elementary algebraic systems theory to include the case oj such linear interconnected systems which need not to be controllable or observable. Also, the properties of controllability and observability, the decoupling zeros and the signal Making issues are characterized.

Simulation of Structural Characteristics and Depth Filtration Elements in Interconnected Nanofibrous Membrane Based on Adaptive Image Analysis

Due to their unique structural features, electrospun membranes have gained considerable attention for use in applications where quality of depth filtration is a dominant performance factor. To elucidate the depth filtration phenomena it is important to quantify the intrinsic structural properties independent from the dynamics of transport media. Several methods have been proposed for structural characterization of such membranes. However, these methods do not meet the requirement for the quantification of intrinsic structural properties in depth filtration. This may be due to the complex influence of transport media dynamics and structural elements in the depth filtration process. In addition, the different morphological architectures of electrospun membranes present obstacles to precise quantification. This paper seeks to quantify the structural characteristics of electrospun membranes by introducing a robust image analysis technique and exploiting it to evaluate the permeation-filtration mechanism. To this end, a nanostructured fibrous network was simulated as an ideal membrane using adaptive local criteria in the image analysis. The reliability of the proposed approach was validated with measurements and comparison of structural characteristics in different morphological conditions. The results were found to be well compatible with empirical observations of perfect membrane structures. This approach, based on optimization of electrospinning parameters, may pave the way for producing optimal membrane structures for boosting the performance of electrospun membranes in end-use applications.

ROBUST STABILIZATING FOR A OLASS OF UNOERTAIN NONLINEAR INTEROONNECTED SYSTEMS USING VARIABLE STRUCTURE CONTROL

The robust stabilizating control problem for a class of uncertain nonlinear large-scale systems is discussed. Based on the theory of both input/output (I/O) linearization and decentralized variable structure control (VSC),two-level and decentralized variable structure control laws for this kind of systems are presented respectively,which achieve asymptotically stabilization despite the uncertainties and disturbances. At last,sirnulation of the disturbed two-pendulum system is given to illustrate the feasibility of proposed technique.

Decentralized Variable Structure Control of Complex Giant Singular Uncertainty Systems

This paper, at the first time, considers the problem of decentralized variable structure control of complex giant singular uncertainty systems by using the property of diagonally dominant matrix and Frobenius-Person theorem. The splendid selection of switching manifold for each subsystem makes the design relatively straightforward and can be easily realized. An illustrate example is given.

ON DECENTRALIZED STABILIZATION OF LINEAR LARGE SCALE SYSTEMS WITH SYMMETRIC CIRCULANT STRUCTURE

The decentralized stabilization of continuous and discrete linear large scale systems with symmetric circulant structure was studied.A few sufficient conditions on decentralized stabilization of such systems were proposed.For the continuous systems,by introducing a concept called the magnitude of interconnected structure,a very important property that the decentralized stabilization of such systems is fully determined by the structure of each isolated subsystem that is obtained when the magnitude of interconnected structure of the overall system is given.So the decentralized stabilization of such systems can be got by only appropriately designing or modifying the structure of each isolated subsystem,no matter how complicated the interconnected structure of the overall system is.A algorithm for obtaining decentralized state feedback to stabilize the overall system is given.The discrete systems were also discussed.The results show that there is a great dfference on decentralized stabilization between continuous case and discrete case.

Calculating the effective thermal conductivity of gray cast iron by using an interconnected graphite model

A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed,and the corresponding effective thermal conductivity was calculated using the thermal resistance network method.The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation.It is suggested that the interconnected structure significantly enhances the overall thermal conductivity.Moreover,it is shown that high anisotropy of graphite thermal conductivity,high volume fraction of graphite,and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity.Higher graphite volume fraction,lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron.This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures.

Three-dimensional-printed polycaprolactone scaffolds with interconnected hollow-pipe structures for enhanced bone regeneration

Three-dimensional(3D)-printed scaffolds are widely used in tissue engineering to help regenerate critical-sized bone defects.However,conventional scaffolds possess relatively simple porous structures that limit the delivery of oxygen and nutrients to cells,leading to insufficient bone regeneration.Accordingly,in the present study,perfusable and permeable polycaprolactone scaffolds with highly interconnected hollow-pipe structures that mimic natural micro-vascular networks are prepared by an indirect onepot 3D-printing method.In vitro experiments demonstrate that hollow-pipe-structured(HPS)scaffolds promote cell attachment,proliferation,osteogenesis and angiogenesis compared to the normal non-hollow-pipe-structured scaffolds.Furthermore,in vivo studies reveal that HPS scaffolds enhance bone regeneration and vascularization in rabbit bone defects,as observed at 8 and 12weeks,respectively.Thus,the fabricated HPS scaffolds are promising candidates for the repair of critical-sized bone defects.

某型直升机超短波电台结构设计

本文开展了适用于某型直升机平台的机载超短波电台结构设计,从结构总体设计、电气互联设计、散热设计、抗冲振性能设计、三防设计等角度,全方位的阐述了设备的结构设计过程,可为同类设备的结构设计提供借鉴。

多维光互连柔性光背板压力分布优化实验研究

【目的】文章旨在改进多层光纤布线结构,提高其抗压性能,进行压力分布优化实验研究,并提出一种多维光交叉互连柔性光背板压力分布优化结构和设计方法。【方法】文章通过改进多层光纤布线结构,利用实验分析不同光纤交叉方式,研究在相同压力下光纤排布、光纤交叉点的密度和光纤交叠层数等因素对光纤损耗的影响,由此提出一种优化光背板压力分布的双层背板理想光纤布线结构。【结果】由实验结果提出的理想双层布线结构采用双层背板和每个背板中的多层光纤优化布线,将两层柔性光背板进行上下叠加,光纤的布线方案采用光纤端口均匀分布在背板的4个边缘,且同一层级光纤紧密排布,交叠两层光纤于交叉点处。通过多层光纤交叉及错位叠加的布局,可实现多层光纤交叉互连布线优化分布,以提高光背板的抗压性能,从而提高其光传输交换的整体性能。【结论】文章所提方案光背板具有更小的体积、更好的抗压性能和更好的光信号传输损耗性能,能够实现更大面积、高密度和大容量柔性n×n光背板,具有良好的可拓展性,并使光纤布线工作更加简单和方便。

一种20GHz四通道差分传输CQFN外壳

基于高温共烧陶瓷(HTCC)技术,设计了一款适用于四通道差分信号并行传输的高密度陶瓷四边无引线扁平(CQFN)外壳。差分传输的垂直结构采用侧面城堡结构和金属化过孔相结合的设计,该结构可以在保证差分信号传输质量的同时,兼顾外壳的板级安装可靠性,同时在该结构基础上对金属化过孔直径以及多通道并行结构进行仿真和优化。测试结果表明,在DC~20 GHz频段,该CQFN外壳的单通道差分传输结构的回波损耗≤-10.00 dB,插入损耗优于-1.50 dB,验证了该外壳可以有效地保证信号的完整性。利用实测数据进行信号传输验证,结果表明四通道差分传输结构可支持20 GHz信号传输。

Ectopic osteogenesis and angiogenesis regulated by porous architecture of hydroxyapatite scaffolds with similar interconnecting structure in vivo

The macro-pore sizes of porous scaffold play a key role for regulating ectopic osteogenesis and angiogenesis but many researches ignored the influence of interconnection between macro-pores with different sizes.In order to accurately reveal the relationship between ectopic osteogenesis and macro-pore sizes in dorsal muscle and abdominal cavities of dogs,hydroxyapatite(HA)scaffolds with three different macro-pore sizes of 500–650,750–900 and 1100–1250 mm were prepared via sugar spheres-leaching process,which also had similar interconnecting structure determined by keeping the d/s ratio of interconnecting window diameter to macro-pore size constant.The permeability test showed that the seepage flow of fluid through the porous scaffolds increased with the increase of macro-pore sizes.The cell growth in three scaffolds was not affected by the macro-pore sizes.The in vivo ectopic implantation results indicated that the macro-pore sizes of HA scaffolds with the similar interconnecting structure have impact not only the speed of osteogenesis and angiogenesis but also the space distribution of newly formed bone.The scaffold with macro-pore sizes of 750–900 mm exhibited much faster angiogenesis and osteogenesis,and much more uniformly distribution of new bone than those with othermacro-pore sizes.This work illustrates the importance of a suitable macro-pore sizes in HA scaffolds with the similar interconnecting structure which provides the environment for ectopic osteogenesis and angiogenesis.

易地扶贫搬迁民族互嵌社区的空间生产与社会结构优化路径研究

易地扶贫搬迁是一种以空间换生存发展的扶贫举措。随着易地扶贫搬迁民族社区从原有的传统村落转移至新的移民集中安置点,面对与原有社区不同的新空间,社区各民族通过不断地调整与适应,逐渐改变了原有的空间结构、互动关系、社会秩序、表象认知和网络社会形态,进而再生产出一个新空间。在新的移民社区,各族群众空间上交错杂居,在日常的生产生活实践中,通过生产上的合作共事、生活中的相互往来、人际关系中的交流互动、社区公共事务的共同参与等,形成各族群众在经济、政治、社会、文化、心理等层面全方位的社区互嵌,进而在易地扶贫搬迁民族社区构建起互嵌式社会结构和社区环境。在治理实践中,社区通过合理规划经营物理空间,打造互嵌式社会结构与社区环境;积极培育型塑社会空间,促进各民族交往交流交融;着力引导构建表象空间,铸牢中华民族共同体意识;持续加强创新网络空间,建设民族社区治理共同体。

考虑故障恢复的产业互联“智造”供需网级联失效模型

大规模、数字化的产业互联“智造”供需网相比于传统供应链具有更强的响应调节能力和风险预防与恢复能力,但可能面临的风险种类更多且风险传播路径更广,导致其鲁棒性更易受到威胁,准确描述网络中故障风险的动态传播过程是提高其鲁棒性的基础.首先,构建具有多个产业社团的产业互联“智造”供需网模型;其次,结合业务节点间相对关联度,构建具有相对故障概率的风险传播模型,再根据节点重要程度,建立同时考虑恢复概率和恢复周期的故障恢复模型;最后,基于改进引力模型构建网络,以网络相对连通率R作为指标,对不同故障和恢复场景下的级联失效进行仿真分析.仿真结果表明:在4组不同故障和恢复场景下均存在临界值导致R值长期处于不稳定状态;参数η和μ对R值的影响均具有一定的边际效应;当网络故障传播能力一定时,恢复能力越弱则R值振荡越明显,网络受影响规模越大,而当恢复能力一定时,故障强度越强R值振荡越明显,网络受影响规模越大.

一种基于倒装芯片的超宽带BGA封装差分传输结构

随着高速数字电路和射频微波电路对时钟频率和带宽的要求越来越高,差分传输结构因其优良的噪声抑制和抗干扰性能而受到越来越多的重视。提出了一种基于倒装芯片的超宽带球栅阵列(BGA)封装差分传输结构。整体传输结构包括采用陶瓷材料制作的倒装芯片用基板、BGA封装焊球和印制电路板(PCB)。主要分析了差分垂直传输结构的尺寸参数对阻抗和截止频率的影响,并利用阶梯过孔减小阻抗不连续性。整体结构的传输性能通过矢量网络分析仪测试的散射参数来表征。测试与仿真结果具有较好的一致性,在DC~60 GHz频段,差分传输结构的回波损耗≤-15 dB,插入损耗优于-1 dB,为超宽带倒装芯片的封装设计提供参考。

小型化S波段瓦式有源相控阵天线系统的设计研究

基于运载火箭天基遥测传输的需求和箭载平台对重量、空间及能量消耗的严格限制,本文设计了一种小型轻量化、高集成、低能耗的S波段瓦式有源相控阵天线系统。该系统包括天线阵列模块、发射组件阵列模块、功分网络模块、波束控制器及电源单元模块。本文阐述了该系统的工作原理、组成架构,并根据要求设计了天线阵列、发射组件、高可靠电源单元以及波束控制器等几种关键电路。经暗室实测,本系统中所研制的天线系统样机其波束宽度、轴比、方位面俯仰面±60°波束扫描范围内的ERIP等指标达到设计要求,与目前市场上同频段功能相似的砖式相控阵天线系统相比,其体积减小45%,重量缩减25%,能耗降低15%,更贴合箭载相控阵天线从体积、重量、经济上的应用需求,同时也为相关领域的相控阵天线系统研制提供了指导。

多层PCB互连应力测试技术及实验验证

随着新能源汽车车载充电机效率和功率的逐步提升,对印制电路板(PCB)的可靠性提出了更高的要求。分析了测试基本原理以及目前国内外的研究现状,依据IPC-TM-6502.6.26:2014中测试方法A提出的测试标准对研制的设备进行互连应力测试(IST)。基于IST原理,分析测试中样品的失效机理,找到需要监控的主要变量。并介绍了四线制测量电路、温度校准等难点。在温度校准中,电阻温度系数会影响样品温度的准确性,因此该变量尤为重要。进行了大量测试,以验证本设备的功能完整性以及使用过程中的稳定性和安全性。此外,使用本设备与IPC标准中指定的IST设备进行了对比测试。测试结果表明,本设备在控制保护程序、数据处理及温度校准方面相比于参考设备更具优势。

温变环境下引脚互连结构长期可靠性研究及优化

基于陶瓷基板-金属管壳引脚互连结构,通过温度循环试验与有限元仿真分析,得出了互连结构在温变荷载作用下的热应力分布图,研究结果表明:在长期温度循环试验后,互连结构产生裂纹的主要原因是焊锡、引脚与陶瓷基板之间热膨胀系数不匹配导致的应力积累。给出了引脚互连结构优化设计方案,通过仿真分析与试验研究,表明优化后的互连结构具有更高的长期可靠性。

基于粒子群算法的互联电网AGC随机最优控制系统

电信号输出量变化会影响有功功率与电量总功率之间的平衡关系,从而使电网频率发生偏移。针对此问题,设计基于粒子群算法的互联电网AGC随机最优控制系统。以AGC架构为基础对预测控制器实施滚动优化与反馈校正处理,完成控制系统的功能结构分析。在此基础上建立粒子群算法模型,根据自然频率特性系数求解结果,确定区域频率偏差指标的取值范围,完善互联电网控制策略,实现互联电网AGC随机最优控制。对比实验结果显示,随着电信号输出量的增大,所设计系统的有功功率与电量总功率之间的配比始终不会小于75%,不会造成电网频率偏移情况。

高导热PVDF/Ag纤维膜的构建及其导热性能

为了提高纤维材料的导热性能,选择不同尺寸的Ag片作为导热填料,通过静电纺丝技术一步构建了具有三维互通导热网络的PVDF/Ag纤维膜,对其形貌和化学结构进行表征,研究Ag片尺寸、Ag片含量、压缩程度对其导热性能的影响,并对其实际应用能力进行评估。结果表明:加入混合尺寸Ag片,能够形成单根纤维内部连通和纤维之间外部连通的三维互通网络结构。具有该结构的PVDF/Ag纤维膜表现出优异的导热性能,导热系数达0.1038 W/(m·K),比纯PVDF纤维膜提高了61%;将其压缩处理后,导热系数进一步提升至8.693 W/(m·K),是压缩前的83.6倍。此外,三维互通网络的PVDF/Ag纤维膜还展示出优异的力学应用能力和疏水性能。研究结果对进一步开发多功能集合的纺织品及柔性材料具有重要的参考价值。