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壳层可控导电聚吡咯/聚苯乙烯复合微球及聚吡咯中空微胶囊的制备 总被引:1,自引:0,他引:1
在导电聚合物含量较小时,含核壳结构的导电聚合物复合粒子就可以具有和本体相当的导电率,且加工性好,近年来这种核壳结构微粒的制备已引起了科学家们的广泛关注.Armes等[制备了导电聚吡咯、导电聚苯胺包覆聚苯乙烯的核壳结构胶体粒子及聚苯胺和二氧化硅的纳米复合物.刘正平等用改进的方法在粒径为116nm的单分散聚苯乙烯乳胶粒子上包覆聚吡咯, 相似文献
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研究函数型Probit模型的sieve极大似然估计的渐近性质.在一定的条件下,证明了估计的强相合性和渐近正态性以及该估计的非参数部分达到最优收敛速度.最后给出了一个模拟研究,表明sieve极大似然估计有较好的有限样本性质. 相似文献
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Properties of all-solid square-lattice photonic bandgap fibres are studied for the first time to the best of our knowledge. Using the plane-wave expansion method and finite element method, we investigate the mode, effective area, confinement loss and dispersion of such fibres. The simulation results demonstrate that the proposed effective mode area of all-solid square-lattice photonic bandgap fibres is 1.25 times larger than triangular-lattice ones and the confinement loss of the fibres is no more than 0.1 dB/m within the bandgap. 相似文献
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Radial imaging techniques, such as projection-reconstruction (PR), are used in magnetic resonance imaging (MRI) for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function (PSF). In this paper, a shaking projection (SP) k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. ASP trajectory has the same aliasing character when using half sampling frequency (or half data) for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling recon- struction. Furthermore, this method can be applied to three-dimensional (3D) hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts. 相似文献
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为改善环氧树脂(EP)材料的力学性能, 采用次序模板法合成了TiO2中空多壳层结构(HoMS)材料, 利用偶联剂对获得的TiO2 HoMSs进行接枝改性后填充到EP中, 制备了TiO2 HoMSs/EP复合材料; 并与单壳层TiO2中空结构进行比较, 研究了壳层数和偶联剂改性对复合材料力学性能的影响规律. 结果表明, 随着壳层数的增加, 复合材料的力学性能增强, 并且偶联剂改性的TiO2 HoMSs可进一步提高复合材料的力学性能. 在该体系中, 经硅烷偶联剂KH-560改性后的三壳层TiO2 HoMSs(3S-TiO2 HoMSs)/EP复合材料的拉伸强度、 断裂伸长率和冲击强度可分别达到71.66 MPa, 7.4%和35.81 kJ/m2. 扫描电子显微镜(SEM)断面形貌表征结果显示, 相较于纯EP材料, TiO2 HoMSs/EP复合材料的断面更加粗糙, 说明TiO2 HoMSs材料起到了吸收外界应力和阻碍裂纹扩展的作用, 提高了复合材料的韧性, 提升了复合材料的冲击性能. 相似文献