A visual attention-based keyword extraction for document classification

Multimedia Tools and Applications - Document classification plays an important role in natural language processing. Among that, keyword extraction algorithm shows its great potential in summarizing...     

Facile in-situ deposition of Pt nanoparticles on nano-pore stainless steel composite electrodes for high active hydrogen evolution reaction

Hydrogen is regarded as a clean and highly efficient renewable energy. The platinum catalytic electrode is widely used in hydrogen evolution reaction (HER), but it has affected its commercial application because of its high cost. Therefore, the study on cost-effective and high-active catalysts toward HER is required to realise large-scale hydrogen production. In this work, we present a novel Pt/NPSSF catalyst prepared by a one-step in-situ deposition of Pt precursor on a nano-porous stainless-steel film (NPSSF) substrate. The prepared catalyst was evaluated in acidic and alkaline conditions for its HER activities. The preliminary results demonstrate that the Pt/NPSSF electrodes have superior catalytic activity for HER. The hydrogen overpotential of Pt/NPSSF is ?70mV (RHE) in the alkaline solution, which is lower than the Pt electrode of ?184mV. At the same time, we also obtained ?71.2 mV of overpotential for the Pt/NPSSF electrode, which is similar to the ?73mV of Pt electrode in the acid solution. The Tafel graphs plotted from the LSV curves indicate the different HER mechanism in the alkaline and acid solution. The HER kinetics of the Pt/NPSSF were studied using EIS. Comparing Pt/NPSSF to Pt electrode, the multi-pore structures of NPSSF and the Pt nanoparticles active sites decrease the charge transfer-resistance for the HER process. The facile preparation, high efficiency and low value of the Pt/NPSSF composite electrodes demonstrate the promising applications in HER.     

La-Ca-Co-Zn 掺杂M型锶铁氧体的相变过程和磁性能研究

采用陶瓷法制备La-Ca-Co-Zn 掺杂的M型锶铁氧体Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19。使用高温X射线衍射仪、振动样品磁强计、热分析、和扫描电子显微镜等对Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 在25°C 到1450°C的相变过程进行了分析,并且讨论了其磁性能。实验结果表明：La-Ca-Co-Zn 掺杂的M型六方铁氧体的形成主要分为两个部分,在大概700℃左右,SrCO3 和Fe2O3先反应生成中间相Sr3Fe2O7-d,然后Sr3Fe2O7-d再和剩下的Fe2O3反应生成M相,并且Sr3Fe2O7-d中的Fe离子化合价与温度有关;随着温度升高,La3+, Ca2+, Co2+ 和 Zn2+开始逐渐溶入中间相或者随后生成的M相中,且在M相中分布均匀;和高温射线衍射仪检测结果不同的是在700℃左右退火时,得到了钙钛矿相;在1200℃烧结,可以得到单一程度很高的M相,但有少量的第二相存在,第二相的存在有利于提高烧结致密度;当烧结温度为1380℃时,铁氧体开始分解;Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 铁氧体粉末退磁曲线的矩形度要低于SrFeO12的退磁曲线矩形度。     

三氧化钨薄膜的光学特性和结构研究

用溶胶-凝胶法和直流反应磁控溅射法制备了表面均匀致密的三氧化钨薄膜,并用双光束紫外可见分光光度计和X衍射分别对薄膜的透光性、结构形态进行了测定;描述了退火温度对薄膜透光性和结构形态的影响,结果表明在高温(＞300℃)退火处理后薄膜的透光率下降,且退火温度越高透光率越低;在350℃以下退火处理后得到薄膜样品为非晶态,在350～400℃范围内退火处理,样品由非晶态向晶态转变.     

微乳液法制备气敏材料的技术及应用

基于微乳液纳米反应器制备气敏材料是制备纳米材料的新方法.介绍了微乳液作为纳米反应器制备气敏材料的方法及原理,重点综述了微乳液法在制备纳米气敏材料方面的研究状况,总结了微乳液法制备纳米颗粒粒径大小的影响因素,并提出了微乳液法制备纳米气敏材料今后的发展方向.     

The effect of secondary phases on electrical properties of ZnO-based ceramic films prepared by a sol–gel method

The ZnO-based ceramic films doped with Bi₂O₃, Sb₂O₃, MnO, Co₂O₃ and Cr₂O₃ were prepared for use as film varistors by a sol–gel method. The formation and the changes of the phases in the films doped with different dopants and annealed at different temperatures were investigated via X-ray diffraction analysis. Three secondary phases, i.e., Bi₂O₃, Zn₇Sb₂O₁₂ spinel and ZnCr₂O₄, were detected in the films when the annealing temperature was above 550 °C. The lattice constants of ZnO and Zn₇Sb₂O₁₂ spinel phase changed with dopants and the annealing temperature, indicating that the diffusion of the ions into the crystals of ZnO and spinel phase had taken placed. The redistribution of the ions changed the constituents of the intergranular phases and the relevant defect species in ZnO grains, and affected intensively the electrical properties of the films, which were used as film varistors. The highest nonlinear coefficient () with the lowest leakage current was achieved when the film, which was doped with Bi₂O₃, Sb₂O₃, MnO and Cr₂O₃, was annealed at 750 °C.     

药用丙烯酸树酯类薄膜材料的研究进展

综述了药物包衣的发展状况、种类,详细介绍了丙烯酸树脂类包衣材料的种类、性质等,并且阐述了丙烯酸树脂水分散体的特性、成膜机理、稳定性及不同种类丙烯酸树脂类产品的制备,最后详细给出了国内外在药物包衣用丙烯酸树脂方面的研究历程及现状.     

健美、健美操优化教学及CAI设计与应用的研究

为优化健美、健美操教学内容和方法，通过实施调查以及对收集的文献资料进行分析，并对所取的数据进行统计学处理，设计．了既简单易行，又能行之有效的教学内容。通过研制的多媒体CAI课件，优化了教学过程。教学实验结果起到了促进学生的主体教育作用，达到了提高教学效果和增强学生素质的预期效果，体现了教学内容的先进性和CAI教学课件设计的科学性。     

城市社区绿地空间研究进展

城市社区绿地空间是以社区居民为主体服务人群的绿色公共设施,是实现存量挖潜、共建共享的重要空间资源。以社区绿地空间为检索主题,对检索得到的1 190篇英文论文和618篇中文论文进行文献计量分析,阐述了该领域的研究进展,并创新性地对比分析中英文论文的研究差异及中国与其他主要发文国家的研究差异。研究发现,中国学者在中英文语境下发表的研究成果有所不同:发表的英文论文紧跟国际趋势与研究热点,在国际学界有一定的引领作用;中文论文则呈现局限于城市绿地系统框架下紧跟政策的片段式研究特征,且明显滞后于英文文献。总结得出中国城市社区绿地空间的研究趋势与不足,以期为未来城市社区绿地空间研究提供参考。