新型地锚张弦梁式泥石流格栅坝构件受力的简化计算方法

针对常见泥石流防治结构被冲击破坏的问题，基于“柔性消能”理念，结合张弦梁结构和竖向预应力锚杆技术，提出一种既能改善结构受力性能、增加结构整体抗冲击能力、保证结构安全可靠，又能减小结构构件截面尺寸、节约成本、便于现场施工组装和后期运营维护的新型地锚张弦梁式泥石流格栅坝，并阐述其技术原理。根据泥石流荷载分布和新型地锚张弦梁式泥石流格栅坝的受力特征，给出其简化的内力计算方法；并利用SAP2000建立新结构有限元模型，分析了结构的整体受力，验证了构件简化计算方法的合理性；结合Python语言和Qt De? signer软件开发了相应的设计计算软件，对新型地锚张弦梁式泥石流格栅坝的内力进行求解。结果表明：提出的新结构抗冲击性能好，构件受力均匀；以后设计中应关注竖杆的剪切脆性破坏和立柱偏心受力情况，保证结构安全；变形协调仅使底层张弦梁与竖杆内力偏大，实际工程应用时，应着重验算底层构件，防止其破坏；文中提出的简化计算方法能较准确的反映结构的受力特性，具有一定的合理性，研究可为新型地锚张弦梁式泥石流格栅坝的设计计算和推广应用提供理论依据和技术支持。     

45 t门座起重机顶升方案设计

针对国内45 t门座起重机大车行走机构平衡梁裂缝问题。分析平衡梁裂缝产生原因并提出相应的维修方案,并对维修关键技术中的顶升方案设计,采用Ansys软件对其强度进行了有限元分析,同时对维修前后的平衡梁进行分析并对比。将维修方案应用于实际工程,取得了较好效果。该顶升机构修复方案设计符合工程实际,对工程实践具有一定的指导意义。     

100 MeV质子回旋加速器二期辐照效应管道设计

针对中国原子能科学研究院100 MeV质子回旋加速器上的单粒子效应辐照装置进行了二期管道设计，采用八极磁铁校正法对束流进行了扩束及均匀化，最终在靶上得到了一个30 cm×30 cm、均匀性好于92%的均匀分布的束斑，满足了单粒子效应实验的需求。为降低靶站处的束流能散及中子本底，采用两级降能的方案，在偏转磁铁前放置1个降能片，将能量分为100 MeV和40 MeV两档，并分别针对这两个能量点进行方案设计，束流利用率均在42%以上。公差分析结果表明，四极磁铁对靶上束斑均匀性的影响大于八极磁铁，安装过程中应优先保证四极磁铁的安装公差。     

High-resolution FIB-TEM-STEM structural characterization of grain boundaries in the high dielectric constant perovskite CaCu3Ti4O12

In this work, the grain boundaries composition of the polycrystalline CaCu₃Ti₄O₁₂ (CCTO) was investigated. A Focused Ion Beam (FIB)/lift-out technique was used to prepare site-specific thin samples of the grain boundaries interface of CCTO ceramics. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectrometry (EDXS) and Electron Energy Loss Spectroscopy (EELS) systems were used to characterize the composition and nanostructure of the grain and grain boundaries region. It is known that during conventional sintering, discontinuous grain growth occurs and a Cu-rich phase appears at grain boundaries. This Cu-rich phase may affect the final dielectric properties of CCTO but its structure and chemical composition remained unknown. For the first time, this high-resolution FIB-TEM-STEM study of CCTO interfacial region highlights the composition of the phases segregated at grain boundaries namely CuO, Cu₂O and the metastable phase Cu₃TiO_4.     

All-printed and highly stable organic resistive switching device based on graphene quantum dots and polyvinylpyrrolidone composite

We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope.     

Bipolar resistive switching behavior and conduction mechanisms of composite nanostructured TiO2/ZrO2 thin film

In this work, TiO₂/ZrO₂ bilayer thin film was prepared on fluorine doped tin oxide (FTO)/glass substrates by using a simple and low-cost chemical solution deposition method. Reproducible bipolar resistive switching (RS) characteristics in Au/TiO₂/ZrO₂/FTO/glass devices are reported in this work. TiO₂/ZrO₂ bilayer thin films prepared in this work shows reversible bipolar resistive switching and unidirectional conduction performances under applying voltage and these special performances of TiO₂/ZrO₂ bilayer thin films was first reported. Obvious resistive switching performance can be observed after setting a compliance current, the ratio of high/low resistance reached about 100 at a read voltage of +0.1V and −0.1V and the RS properties showed no obvious degradation after 100 successive cycles tests. The resistive switching characteristics of Au/TiO₂/ZrO₂/FTO/glass device can be explained by electron trapping/detrapping related with the vacancy oxygen defects in TiO₂/ZrO₂ bilayer thin film layer. According to slope fitting, the main conduction mechanisms of the sample are Ohmic and Space charge limited current mechanism.     

Controllability and observability of multi-agent systems with heterogeneous and switching topologies

ABSTRACT

This paper focuses on controllability and observability of multi-agent systems with heterogeneous and switching topologies, where the first- and the second-order information interaction topologies are different and switching. First, based on the controllable state set, a controllability criterion is obtained in terms of the controllability matrix corresponding to the switching sequence. Next, by virtue of the subspace sequence, two necessary and sufficient algebraic conditions are established for controllability in terms of the system matrices corresponding to all the possible topologies. Furthermore, controllability is considered from the graphic perspective. It is proved that the system is controllable if the union graph of all the possible topologies is controllable. With respect to observability, two sufficient and necessary conditions are derived by taking advantage of the system matrices and the corresponding invariant subspace, respectively. Finally, some simulation examples are worked out to illustrate the theoretical results.     

靶面激光光斑尺寸原位测量的研究

提供了一种简便易行的靶面激光光斑尺寸原位测量的方法。从高斯光束的横向光强分布特性出发,建立了激光烧蚀斑半径与辐照激光能量、光斑尺寸、烧蚀阈值间的关系式,模拟分析发现辐照激光光斑尺寸对烧蚀斑半径随辐照能量变化曲线有较大影响。对于脉宽为2 ms,波长为1064 nm的激光,实验测量了不同能量激光辐照下相纸烧蚀斑半径,并用推导出的关系式拟合测量数据,获得了靶面处光斑尺寸和样品烧蚀阈值。同时,也测量了不同位置处的光斑尺寸和样品烧蚀阈值,对高斯光束束腰位置和样品烧蚀阈值的光斑尺寸效应进行了验证。研究结果表明该技术结果可靠,简单高效。该技术可以为高能激光与固体物质相互作用的基础研究和激光加工等应用领域中实现简单方便地测量靶面光斑尺寸提供帮助。     

Influence of domain switching process on the electrical fatigue behavior of ferroelectrics

We report an experimental approach, designed based on the recent findings that domain switching in ferroelectric ceramics can be separated into three regimes during antiparallel electric field loading, to investigate the influence of domain switching process on the electrical fatigue behavior of ferroelectrics. Uniaxial compressive stress (−2 MPã -100 MPa) and thermal loading (20 °C–150 °C) were used to tune the domain switching process. Under the same loading condition, the bipolar electrical fatigue behavior of soft lead zirconate titanate ceramics was systematically characterized. The amplitude and frequency of the applied electric field are 2 kV/mm and 10 Hz, respectively. By analyzing the evolution of the domain switching process, combined with the measured polarization and strain response, as well as the cracks observed on the surface of the specimen, it is found that the fatigue of ferroelectric ceramics was mainly related to the domain switching process near the coercive electric field: the regime 2 defined in this paper. The underlying mechanism was further discussed by considering the interplay between the domain switching process with the main factors affecting the electrical fatigue of ferroelectrics, namely defect redistribution, charge carrier injection, and crack initiation.