Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Poly(methyl methacrylate) (PMMA) spheres were firstly prepared through dispersion polymerization, then with which as sacrifice template, PMMA/Y(OH)CO3 composite microspheres were prepared by homogeneous precipitation technique. Thirdly, Y2O3 hollow spheres were obtained by calcination of PMMA/Y(OH)CO3 at elevated temperature, and finally Y2O3 hollow shperes reinforced butyl rubber composites were fabricated. The structure and morphology of the Y2O3 hollow nanospheres were characterized by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD) and thermogravimetry (TG). The results show that hollow spheres composed of Y2O3 particles of face-centered cubic crystallorgraphic structure, and their diameter is about 1 μm with a thin shell thickness about 80 nm. The hollow microspheres and powders of Y2O3 as filler were added respectively into butyl rubber to prepare butyl rubber composites. It follows that the butyl rubber composites with addition of Y2O3 hollow spheres rather than that of Y2O3 powders exhibited better damping properties with larger loss factors by frequencies such as 8, 18, 28, 50, 65 and 90 Hz.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2022-05-10 Cooperative journals: 《计算机应用研究》
Abstract： Social account credibility evaluation is an important link to ensure the benign development of network social ecology. Aiming at the problems of multi-dimensional credibility evaluation indexes and various data information uncertainty, this paper proposed a credibility evaluation method based on the improved hierarchical belief rule base. Firstly, this paper constructed a hierarchical structure by analyzing the relationship between the indicators of credibility evaluation from three perspectives: account attribute, communication attribute, and content attribute. Secondly, this paper introduced an adaptive coefficient into the information transformation function to better deal with the characteristic differences between indicators. Finally, to make up for the model error caused by the limitation of expert knowledge, this paper used the covariance matrix adaption evolution strategy with projection to optimize the adaptive coefficients and model parameters. Taking Sina Weibo account as the experimental object, the results show that this method can obtain higher accuracy when the data samples are limited.
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区地理》
Abstract：过去植被覆盖度重建在长尺度气候模拟和陆地生态环境演变机制研究等方面具有重要意义。基于现代过程的孢粉—植被覆盖度转换函数研究，可为利用孢粉地层数据重建过去植被覆盖度变化提供一条新的途径。以内蒙古高原等地39个湖泊和7个水库中心的表层沉积物孢粉组合与归一化植被指数（NDVI）为研究对象，利用加权平均偏最小二乘法（WA-PLS）、局部加权加权平均法（LWWA）和最佳类比法（MAT）分别建立了孢粉—NDVI转换函数；通过留一交叉检验法、自助法和空间自相关性等检验，筛选出最优模型并应用于古地层孢粉数据，实现定量重建过去植被覆盖度变化。结果表明：MAT和WA-PLS模型均受到空间自相关性的显著影响，而LWWA模型则是建立孢粉—NDVI转换函数的最优模型。与已有类似转换函数表现能力的对比表明，本研究建立的转换函数具有较强的可靠性和应用潜力。基于本研究转换函数重建的内蒙古辉腾锡勒（HTL）区域全新世植被覆盖变化与孢粉重建的植被变化具有很好的一致性，进一步印证了本研究转换函数的较强潜力，均表现出对降水变化的响应更为显著。
Subjects: Astronomy >> Astrophysical processes submitted time 2018-05-29 Cooperative journals: 《天文研究与技术》
Abstract： FocusGEO是上海天文台自行研制的新一代地球同步轨道动态监视系统，与大部分商用成熟的天文望远镜相比缺乏标准的硬件底层驱动，同时受到运行环境限制，无法设计开发基于Linux的RTS2或基于Windows的ASCOM的全自动化软件系统。研究团队针对FocusGEO的特殊需求，自行设计开发了一套基于Windows的软件系统，可实现望远镜自动观测、资料实时处理、数据传输与数据管理等过程。介绍了软件系统的实现框架、整体流程和数据并行处理的原理，并重点讨论图像实时转换与传输和数据实时处理与入库的实现方法。长时间的观测运行表明，软件系统工作稳定可靠，可为非通用望远镜系统的自动控制软件开发提供借鉴。
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