Synthesis and characterization of monomer‐casting polyamide 6/polymethacrylic ionomer blends

Monomer‐casting polyamide 6 (MCPA6)/polymethacrylic ionomer blends were synthesized by the in situ anionic ring‐opening polymerization of ?‐caprolactam. The polymethacrylic ionomer used in this study was a copolymer of methyl methacrylate and sodium or zinc methacrylate. Because the polymethacrylic ionomer strongly interacted with polyamide 6 (PA6) chains, it influenced the alignment of the polyamide chains. The change in the degree of the order of hydrogen bonding in MCPA6 caused by the addition of the polymethacrylic ionomer was studied with Fourier transform infrared. The change in the interaction between PA6 chains was studied with rheological measurements. The influence of the polymethacrylic ionomer on the crystallization behavior of MCPA6 was also studied with differential scanning calorimetry. The isothermal crystallization and subsequent melting behavior were investigated at the designated temperature. The commonly used Avrami equation was used to fit the primary stage of the isothermal crystallization. The Avrami exponent (n) values were evaluated to be 2 < n < 3 for the neat MCPA6 and MCPA6/polymethacrylic ionomer blends. The polymethacrylic ionomer, acting as a stumbling‐block agent in the blends, decelerated the crystallization rate with the half‐time of crystallization increasing. The polymethacrylic ionomer made the molecular chains of MCPA6 more difficult to crystallize during the isothermal crystallization process. More less perfect crystals formed in the MCPA6/polymethacrylic ionomer blends because of the interaction between the MCPA6 molecular chains and polymethacrylic ionomer. The crystallinity of the blends was depressed by the addition of the polymethacrylic ionomer. The thermal stability was also studied with thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheological and mechanical properties of dynamic covalent polymers based on imine bond

Dynamic covalent polymers based on imine bond (FPIs), which are capable of reorganizing their constitution on the molecular level, are prepared from bio-based dimer fatty acids. The irregular structure of carbon chains in dimer fatty acids leads to the amorphous nature of FPIs. The effect of imine bond on the glass transition temperature of FPIs is studied by differential scanning calorimetry. The linear viscoelasticity of FPIs is investigated by small amplitude oscillatory shear tests and analyzed by using the Likhtman-McLeish theory. It is found that the rheological behavior of FPIs is similar with that of static, linear entangled polymers predicted by Likhtman-McLeish theory, when the dynamic chain arrangements caused by imine-bond exchange is not active enough. For FPIs, the temperature variation of viscosity is still following the Arrhenius law with an activation energy of ~50 kJ mol⁻¹. Owing to the thermal adaptability, FPIs demonstrate great malleability, self-healing capability and processing stability at elevated temperatures.     

Balancing Damage via Non-Photochemical Quenching,Phenolic Compounds and Photorespiration in Ulva prolifera Induced by Low-Dose and Short-Term UV-B Radiation

The Yellow Sea green tide (YSGT) is the world’s largest transregional macroalgal blooms, and the causative species Ulva prolifera (U. prolifera) suffers from ultraviolet-b radiation (UVBR) during the floating migration process. Previous study confirmed that U. prolifera displayed a wide variety of physiological responses characterized as acclimation to UVBR, while the response mechanisms against low-dose and short-term radiation (LDSTR) are not clear. A study with photosynthetically active radiation (PAR) and UVBR was designed: normal light (NL: 72 μmol photons m⁻² s⁻¹), NL+0.3 (UVBR: 0.3 W·m⁻²), and NL+1.6 (UVBR: 1.6 W·m⁻²). The results showed that high-dose UVBR inhibited photosynthesis in thalli, especially under long-term exposure, while a variety of physiological responses were observed under LDSTR. The inhibition of photosynthesis appeared to be ameliorated by the algae under LDSTR. Further analysis showed that U. prolifera achieved balancing damage by means of non-photochemical quenching (NPQ), accumulation of phenolic compounds coupled with the ASA-GSH cycle involved in the antioxidant process and enhanced photorespiratory metabolism under LDSTR. This study provides new insights into the balancing damage mechanisms of U. prolifera under LDSTR, enabling the thalli to adapt to the light conditions during the long duration and distance involved in floating migration.     

基于改进粒子群算法的有轨电车交叉道口信号控制研究

有轨电车易受到道路环境的影响,而交叉道口作为城市道路通行能力的瓶颈,制约着整个路网的通行效率.建立最优化问题模型,分析改进粒子群算法,利用基于灾变自适应的粒子群算法对有轨电车介入的交叉道口信号配时进行分析.以上海市松江区有轨电车实际单点交叉道口为研究对象,通过模拟仿真,获得该交叉道口的最优信号相位分配方案,该方案能够降低有轨电车对道路拥堵的影响值.     

食品级丁香酚微乳液相行为及其抑菌性

为提高丁香酚的亲水性和抑菌效果,以吐温为表面活性剂,乳酸为助表面活性剂,构建可无限稀释的丁香酚微乳液,并探究微乳化前后丁香酚抑制大肠杆菌和金黄色葡萄球菌的效果。拟三元相图的分析结果表明,与吐温-40和吐温-60相比,吐温-80更能有效增加微乳液单相区面积;乳酸的增溶效果随着乳酸添加量的增加而提高,当丁香酚与乳酸质量比为1∶3时,丁香酚微乳液单相区面积扩大至78.8%。抑菌特性研究结果显示:在一定范围内,随着吐温-80比例的降低,乳酸比例的增加,丁香酚微乳液的抑菌效果增强;当微乳液组分中丁香酚、乳酸与吐温-80的质量比为1∶3∶6时,质量分数0.05%的丁香酚可完全抑制2种受试细菌的生长,同时,该复合微乳液的抑菌活性显著高于不含乳酸的单一丁香酚微乳。研究开发的微乳液旨在为实现丁香酚的增溶增效提供可行的剂型,并有望用于食品防腐保鲜领域。     

一起开关柜带电测试异常分析与处理

随着带电检测技术的发展,通过暂态地电压及特高频检测可以及早发现并处理开关柜运行过程中的绝缘缺陷,确保设备安全运行。介绍一起开关柜带电测试异常,并针对异常情况进行分析,查找异常原因,描述处理过程,为今后异常情况的发现及消除提供参考。     

基于超声和无线组网的超高树障在线监测装置

设计了一种基于超声波技术和无线网络技术的输电线走廊超高树障的在线监控报警装置.该装置的超声测距传感器悬挂在输电线上,使用40 kHz的超声波探测输电线区域内超高树障等异物的距离;依靠互感方式将输电线周围的电磁能量转换为电能实现供电;监控现场划分为多个小区,小区内各探测点利用ZigBee进行自组网,小区与远程控制中心的信息交换依靠通用分组无线业务(GPRS)完成,各小区的地理位置和时间信息取自全球定位系统(GPS).为得到输电线与树木之间距离的准确估计值,利用统计方法对测距值进行了去噪处理,给出了置信度为95％的估计结果.样机的相关实验表明,设计的在线监测装置达到了预期效果.     

Energy conversion in magneto-rheological elastomers

Abstract

Magneto-rheological (MR) elastomers contain micro-/nano-sized ferromagnetic particles dispersed in a soft elastomer matrix, and their rheological properties (storage and loss moduli) exhibit a significant dependence on the application of a magnetic field (namely MR effect). Conversely, it is reported in this work that this multiphysics coupling is associated with an inverse effect (i.e. the dependence of the magnetic properties on mechanical strain), denoted as the pseudo-Villari effect. MR elastomers based on soft and hard silicone rubber matrices and carbonyl iron particles were fabricated and characterized. The pseudo-Villari effect was experimentally quantified: a shear strain of 50 % induces magnetic induction field variations up to 10 mT on anisotropic MR elastomer samples, when placed in a 0.2 T applied field, which might theoretically lead to potential energy conversion density in the mJ cm^-3 order of magnitude. In case of anisotropic MR elastomers, the absolute variation of stiffness as a function of applied magnetic field is rather independent of matrix properties. Similarly, the pseudo-Villari effect is found to be independent to the stiffness, thus broadening the adaptability of the materials to sensing and energy harvesting target applications. The potential of the pseudo-Villari effect for energy harvesting applications is finally briefly discussed.     

彩南油田常温集输一体化技术研究及应用

彩南油田采用单井、计量站两级加热进站集输模式,系统冬季运行能耗高,同时伴随管线结垢、腐蚀、穿孔等现象的发生。为了从根本上解决系统能耗大的问题,油田历时四年开展常温集输一体化研究,建立了采出液常温集输判断方法和一体化实施流程,实现单井温度降低约15℃,计量站停炉期间温度降低6~8℃;节约用电量1 312×10~4kWh/a,节约天然气耗气总量222×10~4m^3/a,年创经济效益1 340万元,为油田节能降耗发挥了重要作用,同时为油田的常温集输提供了技术保障。另外,多效药剂的研发为扩大常温集输实施范围提供了技术支撑,单井加热控制方式的改进在节能降耗最大化的同时,为常温集输井提供了安全保障。     

什么是出行即服务(MaaS)

随着通信技术、计算机技术、车辆技术的快速发展,物联网、互联网、车联网逐步形成并广泛应用,乘客、驾驶员、调度员、车辆、道路、出行环境及云端得以高效联通,智能网联、自动驾驶等新兴技术得到蓬勃发展,巨量时空大数据随之产生与获取,城市交通的发展进入了新技术时代.同时,在可持续发展目标的引领下,出行即服务、共享出行等新兴理念伴随着新兴技术的发展正逐步颠覆现有的城市交通运行场景与运营管理模式,相关理论研究与实践探讨将是未来一段时间内城市交通管理与服务领域的发展方向与研究重点.在总结城市交通发展机遇与挑战的基础上,首先分析了新技术时代解决城市交通管理与服务问题的新思路.随后,分别从交通大数据、共享出行、网联自动驾驶3个方面对城市交通管理与服务领域最新研究成果进行了全面的总结与综述.最后,梳理了新技术时代城市交通管理与服务的相关研究方向.