溶剂对PET纤维聚集态结构的影响

用密度法、DSC,偏光显微镜(PLM)和测定收缩率研究了1,2-二氯乙烷对不同纺速PET纤维聚集态结构的影响。结果表明,纺速不同,溶剂诱导结晶(SINC)及其动力学过程不同。高速纺纤维系取向晶态结构,对溶剂扩散有抑制作用。低、中速纺纤维基本为非晶态结构,SINC过程易于进行,但中速纺纤维取向非晶态含量高,溶胀度和收缩率较小。从而印证了关于不同纺速PET纤维结构特征的结论。     

Numerical study of particle dispersion in the wake of gas-particle flows past a circular cylinder using discrete vortex method

A numerical investigation on the particle dispersion in the wake of particle-laden gas flows past a circular cylinder at Reynolds number of 10⁵ is presented. In the numerical method, the Discrete Vortex Method with the diffusion velocity model is employed to calculate the unsteady gas flow fields and a Lagrangian approach is applied to track individual particles. A dispersion function is defined to represent the dispersion scale of the particle. The distributions of gas velocities and vortex blobs, the trajectories and dispersion functions as well as distributions for particles with various Stokes numbers ranging from 0.01 to 1000 are obtained. The numerical results show that: (1) very small sized particles with St = 0.01 can distribute both in the vortex core and around the vortex periphery, whereas intermediate sized particles with St = 1.0, 10 are distributed around the vortex periphery, and very large sized particles with St = 1000 do not feel the gas flow; (2) only at small Stokes number (St = 0.01, 0.1) the particles do not impact with the cylinder; (3) the particle's dispersion intensity decreases precipitously as St is increased from 0.01 to 10.     

Thermoplastic extrusion—the mechanism of the formation of extrudate structure and properties

Systems processed by thermoplastic extrusion can be regarded as heterophase polymer melts of incompatible water-plasticized biopolymers. In the process of thermoplastic extrusion, proteins and polysaccharides are melted at high pressure and temperature below the temperature region of their thermal decomposition. Dispersed particles of these systems can be deformed in flow. The mixed-melt anisotropic structure, formed in flow, is fixed by rapid conversion of the melt jet that lets the extruder die from a viscous state to a rubber-like state and then to a glassy state caused by cooling and drying. Incompatibility of proteins and polysaccharides in their water-plasticized melt mixtures impacts on structure formation and texturization during thermoplastic extrusion. Presented at the 20th ISF World Congress and 83rd AOCS Annual Meeting and Expo, May 10–14, 1992, Toronto, Ontario, Canada.     

强旋湍流气-固两相流动和煤粉燃烧数学模型及其在涡旋燃烧炉的应用(Ⅰ)——模型

结合新型燃煤涡旋燃烧炉的研制和冷、热态实验,建立并发展了二维强旋湍流气固两相流动和煤粉燃烧的数学模型,以此作为对涡旋燃烧炉内多相流动。传热和燃烧过程进行数值模拟和分析的基础。     

用CS－1高效催化剂生产聚丙烯树脂的纺丝试验

研究了用ＣＳ－１高效催化剂生产聚丙烯树脂的纺丝性能，得出采用该催化剂并结合分子量调节剂可以得到熔融指数较大，分子量分布较窄的聚丙烯树脂，其纺丝及力学性能都比较好。     

MCU平台的嵌入式系统软件设计研究

嵌入式系统的运行需要可靠性和实时性的保证,因此良好的可靠性和实时性是嵌入式系统软件设计的重要标准。同时为了使软件系统的鲁棒性更强,嵌入式系统的设计需要一个非常好的软件架构。这里介绍了一种基于MCU平台的嵌入式系统软件架构方法。在这个方法中,事件驱动机制的引入满足了对软件架构的要求,主程序中不仅采用了优先调度机制,同时也加入了软件抗干扰措施,这些都使系统的实时性和可靠性得到了明显的提高。设计实验比较由该方法得到的软件架构与原始软件架构的实时性,得出由该方法优化后的软件架构确实具有更好的性能。     

直纺熔体输送管道的设计

介绍了熔体管道设计中管道壁厚选择、熔体流量、熔体管道流动压力降和熔体流速等计算方法和设计要点。     

Higher order structures and mechanical properties of bacterial homo poly(3-hydroxybutyrate) fibers prepared by cold-drawing and annealing processes

Pure bacterial homo poly(3-hydroxybutyrate) (PHB) fibers were prepared by melt spinning, followed by cold-drawing in an amorphous state at a temperature just above its glass transition temperature. Cold drawn fibers obtained were further drawn at higher temperatures, followed by annealing at various temperatures under tension. Relations among the processing conditions, higher order structures and mechanical properties were investigated using wide- and small-angle X-ray diffractions (WAXD and SAXD, respectively), birefringence, differential scanning calorimetry (DSC), and tensile measurements. PHB has two different crystalline forms, 2₁ helix conformation (α-form) and planar zigzag conformation (β-form). A single broad reflection of β-form was detected even in a PHB fiber drawn once at a temperature just above its T_g immediately after quenching and it tended to be stronger after 2nd drawing at higher temperatures. Annealing under low temperature and high tension facilitates the occurrence of β-form. It is suggested that the β-form crystal is formed not only from the tie chains between α-form lamella, but also from completely free amorphous chains. Changes in the amount of two types of crystals were analyzed using the WAXD integrated intensity. Birefringence of these fibers shows negative and positive values, depending on process conditions. Changes in higher order structure on the mechanical properties are also discussed.     

特种竹节纱的生产实践

通过改造传统的FA506细纱机,并调整纺纱工艺,纺出了在一根纱线上有2种颜色变化的特种竹节纱.传统的生产竹节纱的方法是用一根粗纱纺制,而本文中的纺制方法是将两根由不同原料制成的粗纱同时喂入,通过后续的染整加工整理,达到在一根纱上出现2个甚至更多颜色变化的效果.     

基于FFT与STM32 MCU的涡街信号处理系统设计

该文针对涡街传感器输出信号的特点和低流速时涡街流量计测量精度受限的问题,设计了一种基于STM32芯片的数字涡街信号处理方法与系统,将涡街传感器输出信号通过低噪声前置放大电路,可采集低流速下的涡街信号,再通过频谱分析法FFT准确计算出涡街信号频率,有效提高了测量精度。