Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Three high-performance continuous fibers PBO, Armos and Twaron were on-line modified by atmospheric air dielectric barrier discharge (DBD) plasma. Then the modified fibers were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), measurements of single fiber tensile strength (SFTS) and interlaminar shear strength (ILSS) in terms of their surface chemical composition, morphology, roughness and tensile strength, as well as interfacial adhesion properties of fiber reinforced composites respectively. Results showed that the oxygen and nitrogen content, and the roughness of fiber surface after DBD plasma modification with PBO, Armos and Twaron were all increased, and the ILSS of their composites were enhanced by 18.6%, 10.2% and 24.8%, respectively. However, it is important to note that there were significant differences in the increment of oxygen and nitrogen content as well as the etching effect of the surface for the three modified fibers, which might be related to the difference of their molecular structures and thermal performances. Apparently, the atmospheric air dielectric barrier discharge (DBD) plasma treatment is proved to be an effective means to improve the surface performance of the fibers while no harm to their SFTS and thereby the ILSS of the composite composed of a resin with the three fibers may obviously be enhanced.
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-10 Cooperative journals: 《干旱区研究》
Abstract：借助观测资料与FNL全球分析资料，对比研究2017年与2014年西安高温天气基本特征与有利环流形势，结果表明：① 2 a西安均发生了40 ℃以上的长时间持续高温天气，其中2014年属于常规高温年份，而2017年西安高温则提前1个月发生，高温的提前发生主要是因为南亚高压强于正常年份同期强度；② 不同于我国南方地区的闷湿高温，西安高温属于干性高温，且昼夜温差较小，由此造成24 h对人体的不适；③ 详细描述了西安高温发生的典型环流特征，即南亚高压与西太平洋副热带高压（简称副高）同时增强，并在对流层中高层相互贯通；④ 南亚高压是影响我国西北地区的主要热源基地，在较大经向度的有利环流背景下，强风速可将热气团向南向东深度输送至下游地区（即西安）；⑤ 在“上辐合、下辐散”的散度场配置下，西安500 hPa以下高空维持明显的下沉气流，加之有利的局部要素相配合，最终造成该地区高温天气的发生。
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