变质心自旋弹头的建模及自适应滑模控制

对自旋弹头实现末端机动的变质心控制系统进行了研究.为了明确表示自旋弹头的运动参数与质量块运动参数之间的关系,采用牛顿力学方法建立自旋弹头的姿态运动模型.模型包括质量块运动方程、姿态运动的运动学方程和动力学方程.考虑到俯仰和偏航通道的动力学特性为非线性的、铰链耦合的,采用自适应滑模控制方法设计了变质心控制系统,对系统中的不确定项进行估计和补偿,保证系统的跟踪误差收敛到零.变质心控制系统通过对质量块的偏移运动进行控制,进而准确地控制自旋弹头的姿态运动.为了检验所设计的变质心控制系统的控制性能,利用MATLAB/Simulink软件构建系统的仿真模型,进行仿真研究.仿真结果表明:所设计的变质心控制系统具有较高的快速性和控制精度,实现了对自旋弹头姿态角的准确控制.     

网眼罗拉型集聚纺集聚区须条集聚机理分析

为深入研究网眼罗拉型集聚纺系统中纤维须条在流场作用下的运动规律,建立了集聚区域的计算流体动力学(CFD)模型,并运用Fluent软件对该区域的流场进行数值计算,然后建立了纤维微元在气流场中的动力学模型,利用自编的Matlab程序对其进行求解,最后获得了纤维在集聚区的运动轨迹.研究结果表明不同初始位置的纤维运动轨迹能够反映须条的集聚规律;气流的横向作用力能够使须条在集聚方向上发生集聚;上层纤维较网眼罗拉表面的纤维集聚速度快;y轴向气流力使须条贴伏在网眼罗拉表面.     

基于磁/惯性传感器旋转弹体定姿的Kalman滤波器设计

微惯性传感器精度较低,其漂移会引起很大的姿态误差,不能提供长时间稳定姿态;磁传感器组合的姿态角误差不随时间累积但姿态角更新速度慢。针对这一问题提出了利用磁/惯性传感器构建低成本姿态探测系统的方案,设计了Kalman滤波器融合二者信息——以磁传感器解算的姿态角和等效旋转矢量法解算的姿态角之差作为观测量,以惯性传感器的漂移和姿态误差角作为状态变量,整个解算过程无需使用地磁场强度。仿真结果表明了该算法的有效性,二者组合定姿可实现高精度的姿态测量。     

Spinning solitons in cubic-quintic nonlinear media

We review recent theoretical results concerning the existence, stability and unique features of families of bright vortex solitons (doughnuts, or ‘spinning’ solitons) in both conservative and dissipative cubic-quintic nonlinear media.     

充液旋压内螺旋翅片铜管的表面加工质量

对内螺旋翅片铜管的高速充液旋压成形加工进行了系统研究,着重分析了充液旋压过程中对加工质量影响最大的两个因素－－旋压量及润滑状况。通过金相显微观察,对不同旋压量及润滑状况下加工的内螺旋翅片铜管旋压区塑性变形的特点作出了分析。     

A Rapid Process for Producing Cellulose Multi‐Filament Fibers from a NaOH/Thiourea Solvent System

Summary: Cellulose was dissolved rapidly in 9.5 wt.‐% NaOH and 4.5 wt.‐% thiourea aqueous solution pre‐cooled to −5 °C to prepare a transparent solution. Novel cellulose multi‐filament fibers were spun successfully, for the first time, from the cellulose dope on an extended laboratory scale. The results from ¹³C NMR, scanning electron microscopy and wide angle X‐ray diffraction (WAXD) patterns indicated that the fibers exhibited cellulose II character and possessed a circular cross‐section and smooth surface. The tensile strength of the novel fibers reached 1.9–2.2 cN · dtex⁻¹. 2D WAXD and SAXS patterns revealed that, with a drawing progress, the orientation factor increased and mechanical properties were improved.

SEM micrographs of the novel multi‐filament fibers spun from cellulose solution in a NaOH/thiourea aqueous system pre‐cooled to −5 °C on an extended laboratory scale.     

Poly(ethylene terephthalate) Nanofibers Made by Sea–Island‐Type Conjugated Melt Spinning and Laser‐Heated Flow Drawing

Nylon‐6/poly(ethylene terephthalate) (PET) ultra‐multi‐island sea–island conjugated melt‐spun fibers are flow‐drawn at a draw ratio of 174 with heating by CO₂ laser irradiation. Continuous PET nanofibers that have a diameter of 39 nm could be obtained from the flow‐drawn fiber with further drawing and removal of the sea component. In addition, the drawn fiber has a strength of 0.54 GPa. This result shows that a PET nanofiber having a strength almost equal to that of a conventional PET fiber can be obtained by the combination of conjugate‐melt‐spinning and laser‐heated flow‐drawing.

     

Necking Point in PET High-speed Fiber Spinning

Cross-over method is established to predict necking point for PET high-speed fiber spuming. Even slowly crystallizing polymers such as PET can crystallize on the spinline at sufficiently high spinning speed. The development of running velocity, temperature, crystallinity and rheological force is investigated for the take-up velocity over a range of 6 000 - 10 000 m/min. The pos-ition of necking point, temperature rise and abrupt increase of crystallinity move closer to the spinneret with the increase of take-up velocity.     

Properties and Processing of the Pineapple Leaf Fiber

The properties and constituent of pineapple fiber were tested, and on the base of that, chemical treatment was used to improve the spinnability of the fiber, and the pure and blended yarn of pineapple fiber were produced in worsted and cotton spinning system.     

高炉熔渣直接纤维化制备矿渣棉

通过利用喷吹法和四辊离心法制备矿渣棉,研究在不同制备方法条件下,矿渣棉其化学稳定性、表观特征、含水率及渣球含量与酸度系数之间的关系。结果表明:在满足成纤要求的前提下,高炉渣酸度系数应控制在1.2~1.4;利用喷吹工艺制备的矿渣棉直径较细,含水率较低,成纤率较低,渣球含量较高纤维质量较差;相对于喷吹工艺,离心法制备的矿渣棉直径相对较粗,含水率大,渣球含量较少,成纤率较高,纤维质量较好。