Multi-layer structure formation of relativistic electron beams in plasmas

A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam tail.Meanwhile,the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase space.The influences of beam parameters(beam radius and transverse density profile)on the formation of the multi-layer structure and collective stopping in background plasmas are also considered.

Modeling Locking Angle of the Multi-layered Biaxial Weft Knitted Fabric in Shear Deformation

This paper introduces the construction of the multi-layered biaxial weft knitted fabric （MBWK fabric） and studies the locking angle of this kind of fabric. Moreover, a locking angle model of the MBWK fabric is established for the first time according to its unique construction. Two kinds of locking angles are considered under different restraint conditions: the locking angle θ1 controlled by the inserting yarns and the locking angle θ2 controlled by the stitch yarns. It is concluded that the ultimate value of the locking angle θ is the larger one of the two angles.

Micrometer-sized ferrosilicon composites wrapped with multi-layered carbon nanosheets as industrialized anodes for high energy lithium-ion batteries

Various nanostructured architectures have been demonstrated to be effective to address the issues of high capacity Si anodes. However, the scale-up of these nano-Si materials is still a critical obstacle for commercialization. Herein, we use industrial ferrosilicon as low-cost Si source and introduce a facile and scalable method to fabricate a micrometer-sized ferrosilicon/C composite anode, in which ferrosilicon microparticles are wrapped with multi-layered carbon nanosheets. The multi-layered carbon nanosheets could effectively buffer the volume variation of Si as well as create an abundant and reliable conductivity framework, ensuring fast transport of electrons. As a result, the micrometer-sized ferrosilicon/C anode achieves a stable cycling with 805.9 m Ah g-1 over 200 cycles at 500 mA g-1 and a good rate capability of455.6 mAh g-1 at 10 A g-1. Therefore, our approach based on ferrosilicon provides a new opportunity in fabricating cost-effective, pollution-free, and large-scale Si electrode materials for high energy lithium-ion batteries.

Defect feature recognition method of glass fibre-reinforced structure based on visual image analysis

Glass fibre-reinforced(GFR)structure is extensively used in radome,spoiler and some other equipment.In engineering practice,due to the influence of wear,aging,impact,chemical corrosion of surface structure and other factors,the internal structure of this kind of structure gradually evolves into a defect state and expands to form defects such as bubbles,scratches,shorts,cracks,cavitation erosion,stains and other defects.These defects have posed a serious threat to the quality and performance of GFR structure.From the propagation process of GFR structure defects,its duration is random and may be very short.Therefore,designing a scientific micro defect intelligent detection system for GFR structure to enhance the maintainability of GFR structure will not only help to reduce emergencies,but also have positive theoretical significance and application value to ensure safe production and operation.Firstly,the defect detection mechanism of GFR structure is discussed,and the defect detection principle and defect area identification method are analyzed.Secondly,the processing process of defect edge signal is discussed,a classifier based on MLP is established,and the algorithm of the classifier is designed.Finally,the effectiveness of this method is proved by real-time monitoring and defect diagnosis of a typical GFR structure.The experimental results show that this method improves the efficiency of defect detection and has high defect feature recognition accuracy,which provides a new idea for the on-line detection of GFR structure defects.

Influencing factors on elastic-plastic deformation of multi-layered surfaces under sliding contact

Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness,layer number and elastic modulus ratio of layer to the substrate. A model of multi-layered surface contact with rough slider was studied. The effect of the surface structure parameters on the elastic-plastic deformation was analyzed.

A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings

A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a high-index ring in the low-index background for this fibre, rather than the whole cladding periodic structure based on Bloch＇s theorem to find the bandgap. Its accuracy is proved by comparing its results with the results obtained by using the accurate full-vector plane-wave method. High speed in computation is its great advantage over the other exact methods, because it only needs to find the roots of one-dimensional analytical expressions. And the results of this model, mode plots, offer an ideal environment to explore the basic properties of photonie bandgap clearly.

Basic Concepts of Graph Theory as the Instruments of Mathematical Formalization of Woven Structures

The paper presents the prerequisites of involving of topological elements and graph theory as an instrument of mathematical formalization of woven structures and technology of textile fabrics. Present research is based on analysis and comparison of the main concepts and conditions of textile technology and graph theory.

含镍铬合金丝纬编电热层复合材料的拉伸性能

为开发一种航空飞行器防冰用电热复合材料,选取3种细度的镍铬合金丝,基于平针、罗纹和双罗纹3种纬编结构,优选了6种镍铬合金丝纬编电加热织物,以镍铬合金丝纬编织物为电热层,制备玻璃/环氧电热复合材料,并采用实验方法研究了镍铬合金丝细度和纬编结构对电加热织物及其复合材料的电热性能和对复合材料拉伸性能的影响。结果表明:同种纬编结构,镍铬合金丝细度较大,织物电热转换效率较低,电加热织物及其复合材料表面最高平衡温度较高,电热复合材料拉伸强度较小;同种镍铬合金丝细度,在11 V直流电压30 s下,平针组织电加热织物为电热层的复合材料表面温度由室温升高到74.1℃,升温速率达1.63℃/s,较罗纹和双罗纹组织升温速率分别高154.69%和33.61%;平针组织电加热织物为电热层的复合材料的拉伸强度为450.2 MPa,较罗纹和双罗纹组织拉伸强度分别高3.68%和4.53%。初步工作表明,含镍铬合金丝纬编电热层复合材料有望满足航空飞行器防冰用电热复合材料的需求。

纬编双面移圈织物多层弹簧-质点结构模型构建与实现

纬编双面移圈织物工艺结构复杂多变,现有系统在进行设计开发时难以直观地展示出织物的组织结构特点。为实现纬编双面移圈织物的组织结构模拟,本文提出了一种纬编双面移圈织物多层弹簧-质点结构模型。首先建立了成圈、集圈、移圈线圈几何结构模型,接着分析了纬编双面移圈织物结构特征,并在传统弹簧-质点模型的基础上构建了多层弹簧-质点模型,然后采用牛顿第二定律和Velocity-Verlet数值积分法求解了多层弹簧-质点模型的最终位置,最终提出了一种纬编双面移圈织物结构模拟的算法流程。本文建立的多层弹簧-质点结构模型能够反映纬编双面移圈织物的组织结构,具有较好的结构模拟效果。

Multi-layer hierarchical cellulose nanofibers/carbon nanotubes/vinasse activated carbon composite materials for supercapacitors and electromagnetic interference shielding

Developing porous self-supporting electrodes with excellent conductivity,good mechanical properties,and high electrochemical activity is crucial for constructing electrode materials with lightweight,ultra-thin,flexible,and high capacitance performance.In this work,we prepared a cellulose nanofibers(CNFs)/carbon nanotubes(CNTs)/vinasse activated carbon(VAC)(CCV)composite material with a multi-layer hierarchical conductive structure through simple vacuum filtration and freeze-drying.In this composite material,the self-assembly of CNF provides the main skeleton structure of a multi-layer hierarchical structure.CNT provides a fast path for the rapid transfer of electrons and is beneficial for the loss of electromagnetic waves.VAC provides sufficient double layer performance.The synergistic effect of the above three endows CCV composite materials with excellent energy storage performance and electromagnetic interference(EMI)shielding performance.In addition,we endowed the CCV composite with a certain shape and performance by introducing a vitrimer polymer with a dynamic cross-linked network structure.In summary,thanks to the synergistic effect of various components in the multi-layer hierarchical structure,CCV composite materials exhibit excellent integration performance,especially stable energy storage performance and EMI shielding performance.These significant properties make CCV composite materials have great application prospects in the fields of energy storage and intelligent EMI shielding.

基于双扎口的纬编管状无缝织物三维仿真

为在设计过程中能够实时查看纬编管状无缝织物不同部位的线圈结构与织物的三维效果,避免反复打样,缩短设计流程,通过分析扎口特殊结构的编织原理,分别建立下扎口、衣身和上扎口编织图模型。结合线圈几何模型和织物实际测量的参数,分别建立上下扎口、衣身和扎口线线圈网格模型。将无缝管状产品的不同组织结构数字化存储为编织图,判断其中编织动作对应的线圈网格类型,代入线圈型值点与线圈网格点间的数学关系式,求得线圈型值点的三维坐标;结合穿纱模型中设计的对应纱线参数,采用WebGL技术渲染线圈型值点路径,实现纬编管状无缝织物的三维仿真。将扎口部位的仿真结果与实际织物对比,结果表明:将线圈分方向建模的方法对实现双扎口结构的仿真是科学可行的,以典型无缝抹胸为例,可对简单的纬编管状无缝产品进行三维平面、筒状和曲面仿真,为进一步研究复杂的纬编无缝产品仿真奠定基础。

防暴雨面料的基材制备及其无氟防水整理工艺研究

为进一步提高户外面料的防暴雨性能,通过分析防暴雨面料基材结构对户外面料防暴雨性能的影响,优化无氟防水整理工艺,测试面料的防暴雨性能,确定防暴雨面料基材结构及无氟防水整理工艺。结果表明:在确定面料基材其他结构参数的情况下,无弹和机械纬弹面料的防暴雨性能相较于机械四面弹更优异;防暴雨性能随着纱线纤度和面料经纬密的增加而增加,面料组织结构对防暴雨性能影响较小。选定机械纬弹、纱线纤度为167 dtex、经纬密度为376×300根/(10 cm)的平纹面料作为防暴雨面料基材,对其进行防水整理,整理工艺为无氟防水剂R3质量浓度40 g/L、交联剂TF-569P质量浓度12 g/L、带液率60%,一浸一轧,焙烘温度170℃,焙烘时间90 s。经防水整理后,洗前防泼水评分为100分,耐水洗测试20次后防泼水评分仍然可保持在95分,进一步对单布进行邦迪斯门防暴雨测试,测试10 min时的防水等级可达3~4级,吸水率为12.5%,透水量为10 mL。该研究结果可为防暴雨户外运动面料的制备提供参考。

高温超导磁悬浮引纬结构悬浮稳定性分析

针对现有电磁投梭技术能量利用率低、引纬幅宽提升有限等问题,提出了一种基于超导磁悬浮的引纬方式,基于高温超导体的迈斯纳效应高温超导片梭能实现其自稳定悬浮,再通过设计的电磁线圈轨道产生行波磁场驱动片梭,从而实现增加片梭织机引纬幅度。由于引纬结构中永磁轨道间磁场存在相互干扰使轨道产生的磁场非对称分布,导致超导片梭两侧超导体悬浮力不相同,超导片梭不能稳定悬浮在轨道上方,后续引纬过程不能进行。为了保证引纬前片梭悬浮稳定性,通过有限元仿真软件分析超导片梭受到的悬浮力,并通过数值计算对永磁轨道磁场进行求解,从而研究磁场分布与超导片梭悬浮稳定性之间的影响。研究表明,轨道上方磁场分布对称性越高,超导片梭悬浮稳定性越高。通过数值计算方法确定了永磁轨道之间的距离为30-40 mm,即永磁轨道之间磁场发生干扰的临界距离,磁场分布具有很强对称性,超导片梭能够稳定悬浮于永磁轨道上方,并且能使超导片梭尺寸最小。

Synergistically biomimetic platform that enables droplets to be self-propelled

Droplet transport still faces numerous challenges,such as a limited transport distance,large volume loss,and liquid contamination.Inspired by the principle of‘synergistic biomimetics’,we propose a design for a platform that enables droplets to be self-propelled.The orchid leaf-like three-dimensional driving structure provides driving forces for the liquid droplets,whereas the lotus leaf-like superhydrophobic surface prevents liquid adhesion,and the bamboo-like nodes enable long-distance transport.During droplet transport,no external energy input is required,no fluid adhesion or residue is induced,and no contamination or mass loss of the fluid is caused.We explore the influence of various types and parameters of wedge structures on droplet transportation,the deceleration of droplet speed at nodal points,and the distribution of internal pressure.The results indicate that the transport platform exhibits insensitivity to pH value and temperature.It allows droplets to be transported with varying curvatures in a spatial environment,making it applicable in tasks like target collection,as well as load,fused,anti-gravity,and long-distance transport.The maximum droplet transport speed reached(58±5)mm·s^(−1),whereas the transport distance extended to(136±4)mm.The developed platform holds significant application prospects in the fields of biomedicine and chemistry,such as high-throughput screening of drugs,genomic bioanalysis,microfluidic chip technology for drug delivery,and analysis of biological samples.

基于ESO的气流引纬滑模分数阶反步控制

针对气流引纬纱线在飞行过程中存在不确定时变因素和未建模问题,提出了一种基于有限时间扩张状态观测器的神经积分滑模分数阶反步控制器。通过对纬纱在气流引纬过程的动力学分析,得到系统的状态方程,引入有限时间扩张状态观测器,对复合扰动问题进行有效估计降低跟踪误差,设计非线性积分滑模面,采用RBF神经网络对滑模面系数进行补偿修正,并融合到反步控制中保证了算法有限时间收敛和稳定性,在虚拟控制律中加入了分数阶理论,进一步提升了系统的稳定性和抗干扰能力。最后,为了使得引纬完成的时间更接近设定值,在筘幅中间额外增加了4个探纬器,并对纱线的运动状态做出调整。研究设计的控制器和改善的引纬结构使得引纬完成的时间更接近设定值,研究验证了所设计方案的有效性。

Simulation study of multi-layer titanium nitride nanodisk broadband solar absorber and thermal emitter

Solar energy has always been a kind of energy with large reserves and wide application.It is well utilized through solar absorbers.In our study,the finite difference time domain method(FDTD)is used to simulate the absorber composed of refractory metal materials,and its absorption performance and thermal emission performance are obtained.The ultra-wide band of 200 nm-3000 nm reaches 95.93%absorption efficiency,of which the bandwidth absorption efficiency of2533 nm(200 nm-2733 nm)is greater than 90%.The absorption efficiency in the whole spectrum range(200 nm-2733 nm)is 97.17%on average.The multilayer nanodisk structure of the absorber allows it to undergo strong surface plasmon resonance and near-field coupling when irradiated by incident light.The thermal emission performance of the absorber enables it to also be applied to the thermal emitter.The thermal emission efficiency of 95.37%can be achieved at a high temperature of up to 1500 K.Moreover,the changes of polarization and incident angle do not cause significant changes in absorption.Under the gradual change of polarization angle(0°-90°),the absorption spectrum maintains a high degree of consistency.As the incident angle increases from 0°to 60°,there is still 85%absorption efficiency.The high absorption efficiency and excellent thermal radiation intensity of ultra-wideband enable it to be deeply used in energy absorption and conversion applications.

电加热机织物的发热性能及发热均匀性探讨

以发热功率密度和温度均匀系数为指标,基于正交试验方案,探讨以不锈钢纤维纱为电加热元件的电加热机织物制备工艺。并基于九宫格取点法,优化温度均匀系数测试方法。研究发现:本研究中,温度测点取81点是可信的均匀度评价方案。电加热机织物的纬纱排列规律为1根不锈钢纤维纱+3根黏胶纱、纬纱密度为10.5根/cm、组织结构为经二重1/7时,织物具有较为优异的发热性能,发热功率密度为857.23 W/m^(2);电加热机织物的纬纱排列规律为1根不锈钢纤维纱+5根黏胶纱、纬纱密度为6.5根/cm、组织结构为经二重1/3时,电加热机织物具有较为优异的发热均匀性。

收纳用横编V形折叠结构织物设计

为探究节约储物收纳空间的柔性针织织物组织与结构创新可行性,以易收纳横编V形折叠结构包为开发对象,展开结构建模、组织设计与试样开发。首先分析折叠结构原理、V形折叠的分类与折痕线类型,在此基础上对横编V形多循环折叠织物进行工艺结构建模,以M1 PLUS软件与STOLL电脑横机作为开发工具,选取76.9 tex再生涤纶竹节纱与12.2 tex/(48 f)热熔涤纶长丝为原料,采用罗纹、双反面、吊针、凸条和浮线组织进行折痕线的结构设计与样品制备。结果表明:折叠结构织物在最大程度缩小自身体积的同时具备大容量可扩展柔性储物收纳的优点,结合材料搭配、上机试样、参数调节与定形工序等建立V形折叠包结构模型与折痕线组织设计实现了可扩容易收纳且环保的横编V形折叠结构织物的快速生产,为横编三维立体折叠结构织物的设计与开发提供了工艺方法与开发实例。

纬编针织物弹伸性成因及预估模型

根据纬编针织物结构与特点,分析织物受力后线圈部段转移的基本特征和弹伸性的成因,并就4大纬编基本组织的弹伸性构成进行描述。组织结构复合是产品设计的重要手段,为分析复合结构织物的弹伸性,提出以串联、并联及其复合模型来预测织物弹伸性的方法。以具体织物结构为例,使用串并联模型分析方法分析织物弹伸性,为预测各种纬编结构针织物的弹伸性提供可行方法与依据。

基于交织点改进弹簧-质点模型的纬编针织物动态变形模拟

为了对不同线圈单元组成的纬编针织物进行动态变形模拟,从而预设织物结构形态和加速面料设计流程。首先通过建立三维结构模型,获得了线圈中心线型值点和交织点之间的关系,并基于交织点改进传统弹簧-质点模型,得到了与纬编针织物适配度更高的变形模型,然后以交织点为桥梁关联结构模型和变形模型,通过NURBS曲线反算原理绘制线圈中心线路径,采用力学求解方法不断更新织物形态变化,使用计算机工具展现了关联模型的动态模拟过程,并举例展示了不同织物组织的变形模拟效果。模拟效果表明,建立的三维结构模型具有合理性与真实性,改进的弹簧-质点模型具有极高的适配性,基于交织点关联两者为后续模拟提供了支撑,采用NURBS曲线并通过力学求解等方法实现纬编针织物的三维动态模拟具有可行性。