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991.
Dr. Qing Zhang Dr. Alvaro Mayoral Junyan Li Dr. Juanfang Ruan Prof. Viveka Alfredsson Dr. Yanhang Ma Prof. Jihong Yu Prof. Osamu Terasaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19571-19581
Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra-framework cations and surface terminations. 相似文献
992.
Weidong Ruan Yinqiu Cui Feng Lin Tieli Zhou Ge Hui Ye Wang Yufeng Chen Fei Lu Jie Guo Bing Zhao 《Journal of Raman spectroscopy : JRS》2015,46(11):1117-1123
The Ag–Au compound nanostructure films with controllable patterns of Ag nanoparticle (NP) aggregates were fabricated. A strategy of two‐step synthesis was employed toward the target products. Firstly, the precursor Au NP (17 nm) films were synthesized as templates. Secondly, the Ag NPs (45 nm) were deposited on the precursor films. Three types of Ag NP aggregates were obtained including discrete Ag NPs (discrete type), necklace‐like Ag NP aggregates (necklace type), and huddle‐like Ag NP aggregates (huddle type). The surface‐enhanced Raman scattering (SERS) property was studied on these nanostructures by using the probing molecule of rhodamine 6G under the excitation laser of 514.5 nm. Interestingly, the different types of samples showed different enhancement abilities. A statistical method was employed to assess the enhancement. The relative enhancement factor for each Ag NP was estimated quantitatively under the ratio of 1 : 25 : 18 for the discrete‐type, necklace‐type, and huddle‐type samples at the given concentration of 10−8 mol/l. This research shows that the enhancement ability of each Ag NP is dependent on the aggregate morphology. Moreover, the different enhancement abilities displayed different limit detection concentrations up to 10−8, 10−11, and 10−9 mol/l, separately. The understanding of the relationship between the defined nanostructures and the SERS enhancement is very meaningful for the design of new SERS substrates with better performance. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
993.
Incremental learning optimization on knowledge discovery in dynamic business intelligent systems 总被引:1,自引:0,他引:1
As business information quickly varies with time, the extraction of knowledge from the related dynamically changing database is vital for business decision making. For an incremental learning optimization on knowledge discovery, a new incremental matrix describes the changes of the system. An optimization incremental algorithm induces interesting knowledge when the object set varies over time. Experimental results validate the feasibility of the incremental learning optimization. 相似文献
994.
Recently, a special class of neural dynamics has been proposed by Zhang et al. for online solution of time-varying and/or
static nonlinear equations. Different from eliminating a square-based positive error-function associated with gradient-based
dynamics (GD), the design method of Zhang dynamics (ZD) is based on the elimination of an indefinite (unbounded) error-function.
In this paper, for the purpose of online solution of time-varying 4th root, both continuous-time ZD (CTZD) and discrete-time ZD (DTZD) models are developed and investigated. In addition, power-sigmoid
activation function is exploited in Zhang dynamics, which makes ZD models possess the property of superior convergence and
better accuracy. To summarize generalization for possible widespread application, such approach is further extended to general
time-varying nonlinear equations solving. Computer-simulation results demonstrate the efficacy of the ZD models for finding
online time-varying 4th root and solving general time-varying equations. 相似文献
995.
Li-juan Ruan 《Frontiers of Physics in China》2010,5(2):205-214
The results from data taken during the last several years at the Relativistic Heavy-Ion Collider (RHIC) will be reviewed in
the paper. Several selected topics that further our understanding of constituent quark scaling, jet quenching and color screening
effect of heavy quarkonia in the hot dense medium will be presented. Detector upgrades will further probe the properties of
Quark Gluon Plasma. Future measurements with upgraded detectors will be presented. The discovery perspectives from future
measurements will also be discussed. 相似文献
996.
Hui Fang Pi Zhi Hong Zhong Han Li Ruan Peng Zhang Yong Hui Zhang Ji Zhou Wu 《中国化学快报》2008,19(7):835-836
A new hopane triterpenoid, hopane 22, 29-diol-29-formate (1), has been isolated from the whole herbs of Saxiglossum angustissimum (Cries.) Ching and its structure has been successfully determined on the basis of spectroscopic evidences. 相似文献
997.
提出了第三代同步辐射光源中的低温超导电流扭摆器和室温水冷电流扭摆器的物理设计方案。文中还讨论了电流扭摆器内腔中的磁场的分布特性,测量方法和电流扭摆器的制造技术的可行性。 相似文献
998.
999.
Shujuan Guo Jiong Ruan Lijuan Li Aifen Fang 《Communications in Nonlinear Science & Numerical Simulation》1998,3(4):248-251
We establish sufficient conditions for asymptotical stability of some nonlinear systems with delay which include populations systems by using Lyapunov functional. Furthermore, we get the results of global stability of these systems when the delays are less than the critical values. 相似文献
1000.
低重复率的Ti:Al2O3飞秒激光放大器研究 总被引:5,自引:1,他引:4
本文报道了重复频率为10Hz的Ti:Al2O3飞秒激光放大器的研究.基于脉冲啁啾放大技术和采用再生/多通放大装置,得到了能量为8mJ的放大光脉冲,在该放大系统中,激光脉冲获M净增益约8×107. 相似文献