试验优化设计Er3+-Yb3+共掺杂Gd2Ti2O7上转换发光特性

采用溶胶-凝胶（Sol-gel）法制备了Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇纳米晶粉末,通过试验优化设计的理论建立了Er³⁺-Yb³⁺掺杂浓度与发光强度的回归方程,利用遗传算法优化计算出方程的最优解Er³⁺、Yb³⁺掺杂浓度分别为5.60%（物质的量分数）和13.43%。Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇纳米晶粉末为单一面心立方Gd₂Ti₂O₇相结构,随Yb³⁺共掺杂浓度增加,X射线衍射峰逐渐向高角偏移。在976 nm激光激发下,Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇获得了分别对应于Er³⁺的²H_11/2/⁴S_3/2→⁴I_15/2和⁴F_9/2→⁴I_15/2跃迁的绿色和红色上转换发光,且绿色和红色发光均为双光子吸收过程。研究了最优样品上转换发光与温度之间的关系,发现绿色上转换发光具有优良的温度传感特性,对红色上转换发光的温度猝灭进行了解释。     

A New Nano Design for Implementation of a Digital Comparator Based on Quantum-Dot Cellular Automata

International Journal of Theoretical Physics - Quantum-dot is the result of elastic relaxation which has a straight relationship with the optical and electronic aspects of the quantum-dot-based...     

Ionic liquid-assisted hydrothermal synthesis of dendrite-like NaY(MoO4)2:Tb phosphor

Micro-sized NaY(MoO₄)₂:Tb³⁺ phosphors with dendritic morphology was synthesized by a ionic liquid-assisted hydrothermal process. X-ray diffraction (XRD) indicated that the as-prepared product is pure tetragonal phase of NaY(MoO₄)₂. Field emission scanning electron microscopy (FE-SEM) images showed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors have dendritic morphology. The photoluminescent (PL) spectra displayed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors show a stronger green emission with main emission wavelength 545 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺ ion, and the optimal Tb³⁺ doping concentration for obtaining maximum emission intensity was confirmed to be 10 mol%. Based on Van Uitert's and Dexter's models the electric dipole–dipole (D–D) interaction was confirmed to be responsible for the concentration quenching of ⁵D₄ fluorescence of Tb³⁺ in the NaY(MoO₄)₂:Tb³⁺ phosphors. The intrinsic radiative transition lifetime of ⁵D₄ level is found to be 0.703 ms.     

Sonication-assisted preparation of a nanocomposite consisting of reduced graphene oxide and CdSe quantum dots,and its application to simultaneous voltammetric determination of ascorbic acid,dopamine and uric acid

Microchimica Acta - Accurate detection of temperature and oxygen concentration at the cellular level is important in tumor diagnosis. Multifunctional nanocomposites are described that consist of...     

SnS2/GCP(石墨烯复合粉末)微米复合材料作为锂离子电池负极材料的电化学性能

以石墨烯复合粉末为添加剂,采用一步水热法制备了一种SnS₂/GCP微米复合材料。在所得到的复合材料中,SnS₂纳米片相互缠绕组成多孔球状SnS₂颗粒,石墨烯复合粉末均匀的包裹在球状SnS₂颗粒表面。将所制备的SnS₂/GCP微米复合材料用作锂离子电池负极材料测其电化学性能。结果显示,在0.1 A·g^-1的电流密度下可逆比容量为795.6 mAh·g^-1,循环100次后比容量损失不到1%。相比于SnS₂其比容量和循环稳定性得到了明显改善,主要是由于石墨烯复合粉末的加入,不仅缓解了SnS₂颗粒在充放电过程中的团聚和体积膨胀,而且还提高了SnS₂颗粒的电导率。     

Calcination temperature optimization,energy transfer mechanism and fluorescence temperature dependence of KLa(MoO4)2:Eu3+ phosphors

The optimum calcination temperature for KLa(MoO₄)₂:Eu³⁺ phosphor was confirmed to be 1000 °C via checking the XRD patterns, SEM images and fluorescence spectra for the samples derived from solid state reaction. The energy transfer behavior between Eu³⁺ ions was studied. It was found that electric dipole–dipole interaction is responsible for the fluorescence quenching of ⁵D₂ and ⁵D₁ levels, but exchange interaction is in charge of ⁵D₀ fluorescence quenching. It was also observed that color coordinates of the studied phosphor can be tuned when the doping concentration is relatively low. The fluorescence thermal quenching process was investigated. It was found the thermal quenching followed well crossover model. Judd–Ofelt parameters of Eu³⁺ in KLa(MoO₄)₂ were obtained, and the optical transition properties were further discussed.     

Treatment of Red Tide in Ocean Using Non-Thermal Plasma Based Advanced Oxidation Technology*

A Pilot-scale experiment for the treatment of red tide in the enclosure was done in sea area of Shandong Province, P.R. China on Aug. 25, 2002. With the method of micro-gap discharge, O₂ in air and H₂O in seawater are ionized and dissociated into large numbers of OH^• radicals, and then dissolved into a part of seawater to form OH^• solution of high concentration. With OH^• concentration of 0.68 mg/L, the kill efficiencies of 29 kinds of red tide organisms such as Chaetoceros lorenzianus and so on reached 99.89%, in which bacterium and vibrio were reduced below the detection limit, also Gonyaulax cysts and Prei. Cysts with the crust were done the lowest limit of test. At the same time, the content of chlorophyll-a was decreased below the detection limit. DO (dissolved oxygen) saturation of seawater was greatly increased to 100% because the residual OH^• radical was decomposed into H₂O and O₂ after 20 min. Therefore the treatment of red tide using OH^• radicals is a kind of advanced oxidation technology, which realizes zero pollution, zero emission and zero residual in the process of the production of OH^• radicals and the treatment of red tide.*Key project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900); key project of National Natural Science Foundation of China (NSFC; 60031001).     

Growth and characterization of ZnO (microdisks)/W18O49 (nanorods) heterostructures

ZnO (microdisks)/W₁₈O₄₉ (nanorods) heterostructures were grown on a Si(111) substrate using a thermal evaporation method. X-ray diffraction of the products indicated two separate phases belong to monoclinic W₁₈O₄₉ and hexagonal ZnO structures. Field emission scanning electron microscope (FESEM) images showed W₁₈O₄₉ nanorods with approximately uniform diameters (∼20 nm) on ZnO microdisk. Field emission Auger electron spectroscopy (FEAES) also confirmed two separate elemental characteristics of W₁₈O₄₉ and ZnO. The Raman and photoluminescence (PL) studies demonstrated that the ZnO microdisks have a good crystallinity with excellent optical properties. The Raman results of the ZnO(microdisks)/W₁₈O₄₉(nanorods) heterostructures indicated only W₁₈O₄₉ structure and the PL results of the heterostructures showed two peaks, one in the ultraviolet region at 374 nm and another in the visible region at 500 nm, which both belong to W₁₈O₄₉ nanorods.     

Herz型空间上的分数次Hardy算子的交换子(英文)

本文主要对分数次Hardy算子和Lipschitz函数产生的交换子进行研究,得到了它在一类Herz型和Morrey-Herz型空间上的有界性.进一步还讨论了高阶交换子在这类空间上的有界性.     

Adaptive fuzzy output feedback control for a single-link flexible robot manipulator driven DC motor via backstepping

In this paper, an adaptive fuzzy output feedback approach is proposed for a single-link robotic manipulator coupled to a brushed direct current (DC) motor with a nonrigid joint. The controller is designed to compensate for the nonlinear dynamics associated with the mechanical subsystem and the electrical subsystems while only requiring the measurements of link position. Using fuzzy logic systems to approximate the unknown nonlinearities, an adaptive fuzzy filter observer is designed to estimate the immeasurable states. By combining the adaptive backstepping and dynamic surface control (DSC) techniques, an adaptive fuzzy output feedback control approach is developed. Stability proof of the overall closed-loop system is given via the Lyapunov direct method. Three key advantages of our scheme are as follows: (i) the proposed adaptive fuzzy control approach does not require that all the states of the system be measured directly, (ii) the proposed control approach can solve the control problem of robotic manipulators with unknown nonlinear uncertainties, and (iii) the problem of “explosion of complexity” existing in the conventional backstepping control methods is avoided. The detailed simulation results are provided to demonstrate the effectiveness of the proposed controller.