各向异性材料包层光纤Bragg光栅的反射谱

应用数值解法对包层为单轴晶体材料且其光轴平行于光纤轴的光纤功率限制因子进行了理论模拟,并从模式特性出发解释了kcl对该类光纤Bragg光栅的反射率的影响.计算结果表明:对于HE11模,各向同性材料包层光纤中的能量比单轴晶体材料包层光纤中的能量更容易集中在纤芯中传输,而且集中程度与kcl的取值有关;各向异性材料包层比各向同性材料包层的光纤Bragg光栅的反射率要高;此类光纤Bragg光栅的反射率主要是由光纤纤芯和包层中能量分布决定的.     

酸侵蚀区白砂岩冻融损伤的影响因素研究

通过循环冻融试验,探究酸侵蚀地区白砂岩冻融损伤的影响因素。研究对三组白砂岩分别作不浸泡、水浸泡、酸浸泡的处理后进行不同次数的冻融循环,再进行单轴压缩试验。并从纵波波速、峰值应力、应力-应变曲线、相对杨氏模量、损伤变量等方面分析不同处理方式的影响。研究表明:水的浸泡是白砂岩冻融损伤的主要原因,酸侵蚀能在一定程度上加快白砂岩的冻融损伤,但本实验中影响不大。研究成果对寒区及酸侵蚀区的建设及工程具有一定的参考价值。     

单轴压应变量子阱红外探测器吸收波长的研究

研究了单轴压应力对GaAs/AlGaAs/GaAs量子阱红外探测器(QWIP)吸收波长的影响。以量子阱电子干涉方法以及单轴压应力作用下量子阱应变理论为基础,分析了GaAs/AlGaAs/GaAs量子阱导带中子能级与应变的关系。理论上计算了单轴应力下四个QWIP吸收波长与应变的关系。结果表明,E1与E<1>能级之间的吸收波长和E(1)与EF能级之间的吸收波长随应变的增大而减小的幅度比E1与EF能级之间的吸收波长和E(0)与E1能级之间吸收波长随应变的增大减小的幅度大。     

[110]/(001)单轴应力对硅价带结构及空穴有效质量的影响

采用K.P微扰法研究了当硅在[110]/(001)方向受一单轴应力作用时, 应力对硅价带结构及有效质量的影响。结果表明：硅在压应力作用下的价带分裂能要大于同样大小的张应力作用下的价带分裂能;在常见的几种晶向中,有效质量沿[110]晶向是最小的。从抑制带间散射,减小有效质量增强迁移率的角度考虑,沿应力方向的[110]晶向最适宜作为载流子的输运方向。所获得的结论可为单轴应变硅器件应力及导电沟道方向的选择设计提供理论参考。     

GaAs结构在单轴加压下的光致发光特性测试

研究了一种GaAs层结构在[110]方向外部单轴应力下基于光致发光(PL)谱的测试方法.层结构的应力由螺旋测微器施加,可以产生平面内的压(拉)应力和应变,大小可以由胡克定律算出.随着应力的增大,观察到了谱峰明显的蓝移.在一系列的加压后,在 1.432 eV,有一个新的峰出现在原有的峰的肩部附近,随着压力增加,两个峰逐渐分开.同时 PL 峰的半峰宽随着应力增加而逐渐加大.最后,本文根据实验结果分析了静水和单轴应力的不同.     

镭射BOPP基膜循环拉伸力学性能的试验研究

目的 为研究双向拉伸聚丙烯（Biaxially Oriented Polypropylene,BOPP）薄膜在重复拉伸使用后的弹性模量变化以及应变变化趋势。方法 以26μm BOPP薄膜为研究对象,以1、1.5、2、2.5、3、3.5、4N为最大加载力分别进行加载周期为15次的单轴循环拉伸试验,总结对比循环次数以及加载力对弹性模量及棘轮应变的影响,分析薄膜性能变化趋势。结果 通过对比同一加载应力不同循环下的弹性模量以及棘轮应变,发现在预设加载力下随着循环次数增加,薄膜弹性模量呈增大趋势,且增大幅度逐渐减小,其棘轮应变与弹性模量变化趋势一致;通过取均值对比不同加载力下的弹性模量以及棘轮应变变化,发现薄膜弹性模量随加载力增大而先增大后减小,最大应变以及最小应变均随加载力的增加而增大。结论 通过试验研究得出了BOPP薄膜在循环拉伸中弹性模量及棘轮应变随加载力、循环次数增大的变化趋势;对薄膜性能变化有了一定的预测,并为实际加工中的张力选择提供了指导性建议。     

Numerical analysis and differential push-flow structure optimization of vacuum disc drying process

The drying characteristics of sludge in a uniaxial vacuum disc dryer are numerically studied in the present study, and the results showed that the drying process of sludge includes three stages: the viscous stage, the sticky stage, and the granular stage. The influence of main parameters such as sludge feeding rate, heat source temperature, and rotating speed of the shaft on the drying process of sludge in the uniaxial vacuum disc dryer is analyzed. In order to optimize the drying efficiency of the dryer, a differential push-flow structure is proposed in this study, which provides different propulsion effects for the sludge in different drying stages. The differential push-flow is achieved by changing the number and angle of the push-flow blades on the discs. Compared with the dryer before optimization, the dryer with optimized differential push-flow structure has better performance.     

Structural development in cycloolefin copolymers under uniaxial elongational flow

Development of structures in new cycloolefin copolymers (COCs) of ethylene–norbornene (E–NB) and ethylene–tetracyclododecene (E–TD) of different NB/TD compositions were investigated under uniaxial elongational flow. For E–NB copolymer, which has multiblock sequences, a shoulder in WAXD at 0.76 nm was evident besides its amorphous halo, and the relative intensity of the peak increased with increasing comonomer content (NB). The appearance of a new peak for E–TD copolymer, and a relatively higher intense peak for E–NB copolymer at the same position of 0.76 nm, indicated that local ordering of the segments occurred when the COC was subjected to uniaxial flow. A lower comonomer composition of elongated COC, at a constant Hencky strain rate, exhibited two T_g values, whereas a higher composition showed a single T_g. Both local ordering and segmentization occurred in low comonomer content COCs but only local ordering occurred in higher comonomer content COCs. Both the shear viscosity and roll processing experiments exhibited similar phenomena of segregation. A model is proposed to illustrate the structure of COC after uniaxial elongation/deformation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3421–3427, 2004     

Viscoelasticity in Polymer Films on Rigid Substrates

The viscoelasticity of two thermally crosslinked polymer coatings was examined in terms of relaxation of the applied stress after a sudden strain. Two different transient methods were utilized: flat‐ended cylindrical indentation testing of a polymer film on a rigid substrate and tensile testing of a corresponding free‐standing polymer film. The correlation between tensile and indentation tests was studied. The mechanical response of a viscoelastic layer deposited on a rigid substrate was investigated as a function of indentation depth. There was good agreement between the results of the tensile and indentation tests for thick film layers at moderate indentation depths. The findings indicate that the substrate influences the coating performance by reducing the viscous contribution to the stress response and amplifying the magnitude of the equilibrium modulus for large indentation depths. The indentation method utilized here was shown to be a potentially suitable tool for the determination of Poisson's ratio of polymer films.