Investigation of improved dielectric and thermal properties of ternary nanocomposite PMMA/MXene/ZnO fabricated by in-situ bulk polymerization

Electric power system applications demand for high-temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in-situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14 times by causing the reduction of thermal resistance, which is actually responsible for the poor thermal conductivity of amorphous pure PMMA polymer. More importantly, hybrid PMMA/4:2 wt% MXene:ZnO nanocomposite leads to an excellent thermal stability. Moreover, further characterization of the synthesized nanocomposites by FTIR, SEM and XRD leads to the evaluation of strong interaction of ternary components with PMMA matrix.     

The Fifth WS/DGAT Enzyme of the Bacterium Marinobacter aquaeolei VT8

Wax esters (WE) belong to the class of neutral lipids. They are formed by an esterification of a fatty alcohol and an activated fatty acid. Dependent on the chain length and desaturation degree of the fatty acid and the fatty alcohol moiety, WE can have diverse physicochemical properties. WE derived from monounsaturated long-chain acyl moieties are of industrial interest due to their very good lubrication properties. Whereas WE were obtained in the past from spermaceti organs of the sperm whale, industrial WE are nowadays mostly produced chemically from fossil fuels. In order to produce WE more sustainably, attempts to produce industrial WE in transgenic plants are steadily increasing. To achieve this, different combinations of WE producing enzymes are expressed in developing Arabidopsis thaliana or Camelina sativa seeds. Here we report the identification and characterization of a fifth wax synthase from the organism Marinobacter aquaeolei VT8, MaWSD5. It belongs to the class of bifunctional wax synthase/acyl-CoA:diacylglycerol O-acyltransferases (WSD). The protein was purified to homogeneity. In vivo and in vitro substrate analyses revealed that MaWSD5 is able to synthesize WE but no triacylglycerols. The protein produces WE from saturated and monounsaturated mid- and long-chain substrates. Arabidopsis thaliana seeds expressing a fatty acid reductase from Marinobacter aquaeolei VT8 and MaWSD5 produce WE. Main WE synthesized are 20:1/18:1 and 20:1/20:1. This makes MaWSD5 a suitable candidate for industrial WE production in planta.     

轨道式垃圾回收机器人设计与分析

针对高速公路高峰期拥挤产生的垃圾等问题,设计一种轨道式垃圾回收机器人,由光伏发电装置、机器人壳体、末端手爪、关节臂以及控制系统等组成,主体结构采用双臂三关节结构,采用西门子PLC控制系统,通过控制关节臂的旋转以及偏转、末端手爪的旋转及开合等动作来实现工作的目的。结合外场作业的特殊性,采用光伏能源装置,对其结构及控制系统进行设计,通过对机器人进行三维建模、运动和控制仿真分析,验证系统的可行性及有效性。     

基于RSI的工业机器人开放式控制系统设计

为提高工业机器人的柔性化及智能化水平,同时满足数据的实时共享、监控,使控制系统具有可扩展性与可移植性,设计了一种基于x86平台和RSI的工业机器人开放式控制系统。引入RSI后可载入应用程序包,实现PC工控机与KUKA机器人系统的实时性数据交换。运用模块化设计思路,针对硬件系统,制定软件系统平台的各功能模块,配合Windows操作系统的数据处理能力,在保证工业机器人实时性的前提下,实现了功能的扩展性和增减性。该系统在KUKA工业机器人力反馈实验平台上进行了可行性验证,试验表明,此开放式控制系统的实时响应性良好,满足预期控制要求。     

北方干鲜果害鼠绿色防控技术

文章介绍了北方干鲜果各种不同为害方式害鼠的相应的绿色防控技术,树根和树干害鼠中华鼢鼠、棕色田鼠宜采用银恒快速捕鼠器捕杀;果实害鼠岩松鼠、花鼠、北社鼠防治时等应采用坚果注射杀鼠剂精准灭鼠技术;果园地面害鼠大仓鼠、长尾仓鼠、黑线姬鼠等可采用TBS技术绿色防控;果实贮藏害鼠褐家鼠、黄胸鼠、小家鼠采用粘鼠板消灭。各类绿色灭鼠技术可为干鲜果害鼠的防控提供参考。     

The influence of processing conditions on the mechanical properties of poly(aryl-ether-ketone)/polybenzimidazole blends

Interest in developing high-performance blends for niche applications has grown significantly in efforts to meet ever-increasing harsh environment demands. In this work, four model poly(aryl-ether-ketone)/polybenzimidazole (PAEK/PBI) blends were chosen to study the influence of premixing methods, processing, and matrix polymers, on their mechanical properties. Among the model poly(ether ether ketone) (PEEK) and PBI blends, mechanical properties are greatly enhanced by melt premixing. The molding process mainly affects the matrix crystallinity, which in turn greatly influences fracture toughness of the blend. Poly(ether ketone ketone) (PEKK) and PBI blend exhibits a slightly lower tensile strength and fracture toughness than PEEK/PBI due to the differences in inherent properties of PEEK and PEKK matrices and their interfacial interaction with PBI. The processing−structure–property relationship of PAEK/PBI blends is established to help guide optimal design of high-performance polymer blends for structural applications. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48966.     

QC小组活动原因分析要点

在开展问题解决型质量管理小组活动中,原因分析不可或缺。要分析到问题的末端原因,须展示问题的全貌,从人、机、料、法、环、测,从全面到重点,从综合到局部,分析到可以直接采取对策的因素为止。掌握原因分析的技巧和要点,有效采取头脑风暴法、5why分析法、5M1E分析环节,正确使用因果图、系统图、关联图,一定能够达到事半功倍的效果。     

Poly(lactic acid)/pulp fiber composites: The effect of fiber surface modification and hydrothermal aging on viscoelastic and strength properties

Poly(lactic acid) (PLA)/kraft pulp fiber (30 wt%) composites were prepared with and without a coupling agent (epoxidized linseed oil, ELO, 1.5 wt%) by injection molding. The non-annealed composite samples, along with lean PLA, were exposed to two hydro-thermal conditions: cyclic 50% RH/90% RH at 23 and 50°C, both up to 42 days. The aging effects were observed by size exclusion chromatography, differential scanning calorimetry, dynamic and tensile mechanical analysis, and fracture surface imaging. ELO temporarily accelerated the material's internal transition from viscous to an increasingly elastic response during the aging at 50°C. ELO also slowed down the tensile strength reduction of the composites at 50°C. These observations were explained with the hydrophobic ELO molecules' coupling and plasticizing effects at fiber/matrix interfaces. No effects were observed at 23°C.     

爆破作用下预制共线裂纹的扩展机理研究

为了研究爆破作用下裂纹的扩展规律,从而进一步指导裂隙发育岩体爆破设计。试验运用深部岩石三轴动静载荷实验系统对含有预制裂纹的混凝土试件逐一加载,得到混凝土试件抗压强度;并采用高速摄像机对试件中裂纹起裂拓展过程进行全程拍摄,与加载曲线对照,得到裂纹起裂时垂向初始压力。研究表明:在一定范围内,试件所受围压越大,其裂纹起裂时所需压力越大;次裂纹的存在会使得主裂纹端部更容易在外力作用下起裂,且主裂纹内侧端部所受影响要大于外侧端部,这种影响程度的大小与次裂纹长度、裂纹间距等因素有关;围压越小、裂纹夹角越大、次裂纹长度越大、裂纹间距越小,主裂纹端部越容易起裂。     

Comparative study of gasoline,diesel and biodiesel autothermal reforming over Rh-based FeCrAl-supported composite catalyst

Catalytic autothermal reforming (ATR) of a number of hydrocarbon fuels was studied over composite RhCZ-S catalyst (0.24 wt% Rh supported on structured Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl carrier). Iso-octane and n-hexadecane as model compounds of gasoline and diesel fuel, respectively, showed similar properties in ATR process, indicating weak influence of molecular weight and branching degree of liquid alkanes on catalyst performance. Biodiesel ATR characteristics were similar to those of n-hexadecane ATR, as the utilized biodiesel predominantly contained alkanes, being products of fatty acid tail fragments hydrogenation. Even in the case of gasoline ATR, sufficient amount of monoaromatics did not influence a lot on the catalyst performance. Diesel ATR showed rather different situation: the catalyst tended to lose activity due to coking, and incomplete fuel conversion was observed. Analysis of unreacted fuel revealed bi- and polyaromatic compounds (mainly naphtalenes and antracenes) were difficult to convert.