不同变截面桩竖向承载特性的数值分析

基于现场试验,采用Abaqus有限元软件对等截面桩及变截面桩单桩竖向承载力测试实验过程进行数值模拟。结果表明:弹性变形阶段,竖向荷载-沉降曲线呈线性变化趋势,等截面桩比变截面桩桩身沉降较小;塑性屈服阶段,等截面桩与变截面桩单桩承载力几乎一致。变截面位置对桩侧摩阻力沿深度的分布有一定影响,最大侧摩阻力位置根据变截面的位置而变化。变截面桩的平均侧摩阻力较等截面桩的平均侧摩阻力大,变截面桩侧摩阻力效果较等截面桩更有优势。在相同承载力条件下,变截面桩所耗费的材料较等截面少,对于竖向承载特性,变截面桩与等截面桩表现基本一致,因此使用变截面桩能节约工程成本。     

片状变燃速发射药燃烧性能的数值计算

为研究包覆方式对片状发射药燃烧性能的影响,建立了不同包覆方式下多层片状发射药的物理模型,并推导了形状函数和燃气生成猛度表达式,利用Matlab软件对不同的宽厚比、长厚比及多层结构的片状发射药进行了数值计算;制备了不同长厚比的片状变燃速发射药,并进行了密闭爆发器实验。结果表明,四面包覆和全包覆可以很好地消除临界宽厚比对片状发射药燃烧性能的影响;与两面包覆的片状发射药相比,四面包覆和全包覆的片状发射药能够延缓内层药减面燃烧的时间,其燃气生成猛度的阶跃程度分别提高了1.17%和1.23%,呈现出良好的燃烧渐增性。     

变频调速传动系统的电磁兼容分析

在变频调速传动系统中,变频器会产生和受到各种电磁干扰。本文分析了变频调速传动系统的主要电磁干扰源和耦合途径,并阐述了抑制其电磁干扰的措施。     

ANN valuation model of material LCIA profile

Weighting model is the only valuation model of life cycle impact assessment(LCIA) profile now. It simplifies evaluation function into linear function, and makes the determination of weighting factor complicated. Therefore the valuation of LCIA profile is the most critical and controversial step in life cycle assessment(LCA). Development on valuation models, which are understood easily and accepted widely, is urgently needed in the field of LCA.The modeling approaches for the linear evaluation function were summed up. The modeling approaches for the nonlinear evaluation function were set up by function approximation theory, which include choosing preference products, forming preference data, establishing artificial neural network(ANN) and training ANN by preference data.By selecting 7 material products as preference product, experience was done with modeling approaches of the nonlinear evaluation function. The results show that the modeling approaches and valuation model of the nonlinear evaluation function are more practical than the weighting model.     

镍系聚丁二烯橡胶生产技术进展

介绍了近几年国内外镍系顺丁橡胶生产技术的进展情况，内容涉及分子量调节技术、催化剂配置技术、节能降耗的气相聚合、本体聚合工艺及橡胶后处理过程中使用的热泵技术、螺杆挤压工艺，同时也对国内外顺丁橡胶新型防老剂的使用情况及其新品种的开发进行了简要介绍。     

高性能纤维的弯曲疲劳断裂研究

在自制弯曲疲劳装置上 ,对 3种高强对位芳纶及超高相对分子质量聚乙烯纤维 (Dyneema SK65 )进行双面弯曲疲劳试验。结果表明 ,Twaron 2 0 0 0弯曲疲劳寿命的自然对数与预加应力、弯曲角度呈线性关系 ,Dyneema SK65弯曲疲劳寿命明显长于对位芳纶 ,Twaron 2 0 0 0 ,Kevlar 12 9相近 ,都比Kevlar 2 9略长 ;高强型对位芳纶的弯曲疲劳断裂断口芯层呈现出“毛笔头”或“拔丝形”原纤化分裂形态 ,超高相对分子质量聚乙烯纤维弯曲疲劳断裂断口有明显的脆性折断形态 ,无原纤出现。     

聚酯的摩尔质量与机械性能研究——Ⅰ.动态力学性能

应用粘弹谱仪考察了不同摩尔质量的聚酯(PET、PBT、PBT/PET)的动态力学性能,结果表明摩尔质量增大将提高其模量,但亦导致结晶速度变慢,使测得的模量反而比摩尔质量较低的试样小.     

低截留分子质量新型聚芳醚腈酮超滤膜的研制

以新型聚芳醚腈酮为膜材料 ,以N -甲基 - 2 -吡咯烷酮 (NMP)为溶剂 ,研究了聚合物浓度、添加剂种类及含量、凝胶浴温度等对超滤膜性能的影响。结果表明 ,聚合物质量分数以 1 2 %～ 1 3 %为合适的制膜浓度 ,以聚乙二醇PEG - 4 0 0为添加剂时获得了高截留率和高水通量的超滤膜。随着凝胶浴温度的升高 ,水通量明显增大 ,而截留率有所下降 ,而共聚物的浓度增加则有相反的效果。制得的超滤膜具有较低的截留分子量 (PEG- 2 0 0 0 ) ,将制得的超滤膜用于达旦黄、黄X-G等染料的分离 ,截留率均达 90 %以上     

Adhesion Mechanisms of Polyurethanes to Glass Surfaces I. Structure-Property Relationships in Polyurethanes and Their Effects on Adhesion to Glass

Polyurethanes were prepared from toluene diisocyanate (TDI), 1-4-butane diol (BDO) and polycaprolactone-based triols with varying molecular weights. Among each molecular weight triol-based urethane, hard segment content was varied from 20% to 70%. Differential scanning calorimetry, tensile testing, and Iosipescu shear testing were done on all the various urethanes prepared. Thermal characterization data revealed the dependence of phase separation on hard segment content as well as on the triol molecular weight. Tensile data and Iosipescu shear data further confirmed the observations made from the DSC data. The data further indicated that phase separation can greatly improve the modulus of cross-linked segmented urethanes. Adhesion of these urethanes to glass surface was evaluated using soda-lime float glass plate. Urethane samples were cast on the air side of the glass plates and adhesion was measured in shear mode. Adhesion data indicated that in addition to hard segment content, modulus, cross-link density, and molecular weight of the triols, phase separation seems to be a major factor in controlling adhesion. Surfaces of the failed adhesion samples were also analyzed and the failure mode was found to be cohesive, in varying degree, with the different urethane systems.     

采矿法方案优选指标权数的动态分析

在采矿方案优选的研究中，其决策的正确与否，取决于参与计算的采矿法的定量、定性指标个数以及这些指标的权数。本文通过实例分析了指标权数的波动对采矿方案优劣排序的影响，以减小决策的风险。