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排序方式: 共有2998条查询结果,搜索用时 15 毫秒
31.
Zi Yang Qiang Li Yuanyuan Li Shaofeng Zhang Lin Wang 《Journal of Materials Science》2012,47(23):8007-8012
Single crystals of Pb0.97La0.02(Zr0.66Sn0.27Ti0.07)O3 (PLZST) with the composition near the morphotropic phase boundary were grown by the flux method. The PbO–PbF2–B2O3 system was used as a solvent. PLZST single crystals with the size of 4–6 mm are obtained and these crystals are slightly translucent after polishing. The splitting of (200) reflection peak indicates that the obtained crystals are of a single phase with tetragonal perovskite structure. The element contents of the grown crystals were measured by inductively coupled plasma atomic emission spectrometry. The chemical composition of the crystals is Pb0.979La0.014(Zr0.666Sn0.285Ti0.049)O3. Thermal properties and dielectric properties of PLZST single crystals were studied. The results show that flux-grown PLZST single crystals exhibit obvious endothermic processes and relaxor behaviors near the phase transition temperatures. 相似文献
32.
针对金刚石膜微波介电损耗低、厚度薄带来的微波介电性能测试难点, 研制了一台分体圆柱谐振腔式微波介电性能测试装置。利用不同直径的蓝宝石单晶样品, 用上述装置对低损耗薄膜类样品微波介电性能的测试能力及样品直径对测试结果的影响进行了实验研究。在此基础上, 使用分体圆柱谐振腔式微波介电性能测试装置对微波等离子体化学气相沉积法和直流电弧等离子体喷射法制备的高品质金刚石膜在Ka波段的微波介电性能进行了测试比较。测试结果表明, 由Raman光谱、紫外-可见光谱等分析证明品质较优的微波等离子体化学气相沉积法制备的金刚石膜具有更高的微波介电性能, 其相对介电常数和微波介电损耗值均低于直流电弧等离子体喷射法制备的金刚石膜。 相似文献
33.
Piezo‐Phototronic Effect on Selective Electron or Hole Transport through Depletion Region of Vis–NIR Broadband Photodiode 下载免费PDF全文
Haiyang Zou Xiaogan Li Wenbo Peng Wenzhuo Wu Ruomeng Yu Changsheng Wu Wenbo Ding Fei Hu Ruiyuan Liu Yunlong Zi Zhong Lin Wang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(29)
Silicon underpins nearly all microelectronics today and will continue to do so for some decades to come. However, for silicon photonics, the indirect band gap of silicon and lack of adjustability severely limit its use in applications such as broadband photodiodes. Here, a high‐performance p‐Si/n‐ZnO broadband photodiode working in a wide wavelength range from visible to near‐infrared light with high sensitivity, fast response, and good stability is reported. The absorption of near‐infrared wavelength light is significantly enhanced due to the nanostructured/textured top surface. The general performance of the broadband photodiodes can be further improved by the piezo‐phototronic effect. The enhancement of responsivity can reach a maximum of 78% to 442 nm illumination, the linearity and saturation limit to 1060 nm light are also significantly increased by applying external strains. The photodiode is illuminated with different wavelength lights to selectively choose the photogenerated charge carriers (either electrons or holes) passing through the depletion region, to investigate the piezo‐phototronic effect on electron or hole transport separately for the first time. This is essential for studying the basic principles in order to develop a full understanding about piezotronics and it also enables the development of the better performance of optoelectronics. 相似文献
34.
Jing Fan Shin‐Hyun Kim Zi Chen Shaobing Zhou Esther Amstad Tina Lin David A. Weitz 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(31)
Compressed monodisperse emulsions in confined space exhibit highly ordered structures. The influence of the volume fraction and the confinement geometry on the organized structures is investigated and the mechanism by which structural transition occurs is studied. Based on the understanding of ordering behavior of compressed emulsions, a simple and high‐throughput method to fabricate monodisperse polyhedral microgels using the emulsions as the template is developed. By controlling the geometry of the confined spaces, a variety of shapes such as hexagonal prism, Fejes Toth honeycomb prism, truncated octahedron, pyritohedron, and truncated hexagonal trapezohedron are implemented. Moreover, the edge sharpness of each shape is controllable by adjusting the drop volume fraction. This design principle can be readily extended to other shapes and materials, and therefore provides a useful means to create polyhedral microparticles for both fundamental study and practical applications. 相似文献
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37.
针对K-means算法全局搜索能力的不足,提出了基于模拟谐振子的优化K-means聚类算法(SHO-KM),该算法克服了K-means聚类算法对初始聚类中心选择敏感问题,能够获得全局最优的聚类划分。为了提高聚类划分质量,在聚类过程中采用基于Fisher分值的属性加权的实体之间距离计算方法,使用属性加权距离计算方法进行聚类划分时,无论是球形数据还是椭球形数据都能够获得较好的聚类划分结果。对KDD-99数据集的仿真实验结果表明,该算法在入侵检测中获得了理想的检测率和误报率。 相似文献
38.
Robust fusion time‐varying Kalman estimators for multisensor networked systems with mixed uncertainties 下载免费PDF全文
This paper addresses the problem of designing robust fusion time‐varying Kalman estimators for a class of multisensor networked systems with mixed uncertainties including multiplicative noises, missing measurements, packet dropouts, and uncertain‐variance linearly correlated measurement and process white noises. By the augmented approach, the original system is converted into a stochastic parameter system with uncertain noise variances. Furthermore, applying the fictitious noise approach, the original system is converted into one with constant parameters and uncertain noise variances. According to the minimax robust estimation principle, based on the worst‐case system with the conservative upper bounds of the noise variances, the five robust fusion time‐varying Kalman estimators (predictor, filter, and smoother) are presented by using a unified design approach that the robust filter and smoother are designed based on the robust Kalman predictor, which include three robust weighted state fusion estimators with matrix weights, diagonal matrix weights, and scalar weights, a modified robust covariance intersection fusion estimator, and robust centralized fusion estimator. Their robustness is proved by using a combination method, which consists of Lyapunov equation approach, augmented noise approach, and decomposition approach of nonnegative definite matrix, such that their actual estimation error variances are guaranteed to have the corresponding minimal upper bounds for all admissible uncertainties. The accuracy relations among the robust local and fused time‐varying Kalman estimators are proved. A simulation example is shown with application to the continuous stirred tank reactor system to show the effectiveness and correctness of the proposed results. 相似文献
39.
Web上分布式领域组件的框架表示 总被引:1,自引:0,他引:1
文章采用知识表示中的框架表示法,结合谓词产生式,语义网络等手段,提出了一个具有网络分布式及Web化构造特性的领域构架及组件的表示方法FRDDC。应用FRDDC实现的AND-CASE模型表现了FRDDC的自然性,结构性,Web可操作性,容纳柔性及知识表达能力。 相似文献
40.