Low-defect graphene–polyamide-6 composites and modeling the filler–matrix interface

Low-defect graphene (G) was prepared via the thermal reduction of expanded graphite in a carbon monoxide environment. G exfoliated and suspended in p-xylene was compounded in polyamide-6 (PA6) with filler content ranging from 0.1 to 6%·w/w. Interactions between G and PA6 were characterized via Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Elastic modulus (E) had increased with increasing G content, and had exceeded idealized Halpin–Tsai predictions at 0.1–1.0%·w/w G content, indicating good dispersion and filler–matrix interactions. However, further analysis with a modified rule-of-mixtures (RoM) mathematical model indicate that the quality of filler–matrix interface had been suboptimal and had deteriorated drastically with increasing G content. The evaluation of interface quality is in agreement with observed changes in thermal behavior trends. The modified RoM can be applied as a useful tool toward interpreting the mechanical properties of graphene-reinforced composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48630.     

基于图像的介入器械前端变形建模与受力估计

目的 血管介入手术中介入器械与血管壁之间的接触力对手术安全有着重要意义,然而目前缺乏直接测量器械前端与血管壁接触力的传感器和有效手段。为解决这一难题,本文提出了一种通过图像观察器械前端变形程度从而估计器械与血管壁接触力的方法。方法 通过模拟血管介入手术过程来获取介入器械导丝的变形量和与之相对应的力,从而对介入器械前端接触力与变形量关系进行建模。将介入器械前的端接触力分为垂直于接触面方向的力和沿着接触面方向的力并分别加以处理;使用介入器械前端变形段的最大曲率变化量描述器械变形量,通过图像观察导丝变形来计算导丝的最大曲率。为求解最大曲率,使用器械上3个点构成的三角形并求其外接圆曲率来表示这3点所在段的曲率,在介入器械前端进行依次遍历求取最大值以获得最大曲率。通过实验分析验证介入器械受力与最大曲率之间的关系。结果 实验表明介入器械前端的接触力与器械前端最大曲率变化率之间存在着映射关系,且这种关系能用函数表达式准确地表达出来,通过函数式来预测受力的平均误差在10%以内。结论 研究表明,通过图像分析导丝前端的变形量、估计导丝前端接触力,进而判断血管手术过程中介入器械与血管壁的接触状态的方法是可行的,所计算的导丝前端受力能为手术过程提供参考信息。     

两套25000m~3/h空分设备的优化操作和改进

为提高25000 m3/h空分设备的运行稳定性和经济性,对空分设备的氮水预冷系统、精馏系统以及配套的液化装置实施了优化操作与改进措施。详细分析了优化操作的理论依据、具体的实施方案和效果。     

氧透进口过滤器冲破事故的原因分析

针对新钢16000 m3/h制氧机氧透发生的两起进口过滤器损坏的事故,分析了氧透控制系统中存在的隐患及其改进措施,总结了在操作中应该吸取的经验和教训。     

采用SIFT特征的空基动态视频稳定技术

当采用空基平台对道路进行交通检测时,平台沿道路飞行,空基平台姿态不易控制且控制精度较低,此外,由于风速影响和平台自身振动等因素,检测获取的视频图像存在不必要的随机摇摆和抖动,为了去除抖动,改善观测效果,需进行动态观测模式下的视频稳定处理以实现稳定观测.采用改进的SIFT算法进行特征提取,提高了SIFT特征提取的效率,并根据动态视频相邻帧匹配的实际应用,采用邻域搜索方法进行特征匹配,提高了匹配的精度.得到精确匹配的特征点对进行运动参数估计,并采用Kalman滤波对运动参数平滑后进行视频图像的校正补偿,得到稳定的视频输出.该算法精度较高,稳定效果较好,能有效地实现空基平台动态视频稳定处理,便于交通监控,为后续的目标检测与跟踪提供了便利.     

外墙渗漏的主要原因及预防措施

外墙渗漏直接影响到建筑物的使用功能,也严重影响建筑物的观感效果,是工程质量长期治理的顽症之一。文章以某学校教学楼墙面渗漏为例,全面分析了引起渗漏的原因,并提出防治墙面渗漏的具体措施。     

制约大型空分装置运行周期的因素及处理措施

通过对大型空分冷箱扒砂检修的诸多原因分析，结合多台空分冷箱的安装、检修、维护和运行的经验，对延长空分装置运行周期提出了应对措施，并在多台空分中进行了实践，效果显著。     

基于免疫机理的汽车故障检测技术研究

对基于免疫系统反面算法机理提出的反面算法进行了改进,给出了一种改进型反面选择算法.根据小波分析和人工免疫系统的原理,提出了一种基于小波变换和免疫系统的故障诊断系统.针对小波分析的特点,将其用来对非稳定信号进行分析,获取信号特征向量作为原始数据,利用改进型反面选择算法对原始数据进行己-非己分析.将此系统应用到汽车差速器故障诊断中,取得了良好的效果.     

异龙脑愈创木酚合成檀香的制备

以酸性白土为催化剂 ,进行异龙脑与愈创木酚的选择性烷基化反应 ,烷基化反应产物异龙脑基愈创木酚在雷尼镍存在下催化加氢 ,得到合成檀香异莰基环己醇混合物。该工艺所得合成檀香中主要成分含量较高 ,香气纯正 ,粘度较大 ,留香时间长 ,有一定的实用价值。     

Recycled poly(ethylene terephthalate) chain extension by a reactive extrusion process

A commercial‐scale reactive extrusion processing system for recycled poly(ethylene terephthalate) (PET) flakes with an added chain extender, pyromellitic dianhydride (PMDA), was investigated. The PMDA concentration was varied with the intention of reaching a higher recycled PET intrinsic viscosity ([η]). The effect of changing the extruder residence time on the system's stability and the recycled PET [η] was also investigated. Reactive extruded PET with a PMDA concentration up to 0.3 wt% was found to have a higher [η] and lower carboxyl content than recycled PET processed in a normal extrusion system. A shift in [η] of about 0.18 dl/g was obtained with a 0.3 wt% PMDA concentration. A PMDA concentration above 0.3 wt% produced chemical, thermal and hydrodynamic instability in the system, causing crosslinking reactions and gel formation. The reactive extrusion system was stable at low residence time (45 s) and moderate (0.15 wt%) PMDA concentration; however, using 0.2 wt% PMDA produced higher reactive extruded recycled PET [η] with lower carboxyl content than other PMDA concentration levels examined. Residence times higher than 45 s produced higher reactive extruded recycled PET [η]. Reactive extruded recycled PET was also tested for mechanical properties. Polym. Eng. Sci. 44:1579–1587, 2004. © 2004 Society of Plastics Engineers.