Synthesis of RGO/Cu8S5/PPy Composite Nanosheets with Enhanced Peroxidase‐Like Activity for Sensitive Colorimetric Detection of H2O2 and Phenol

In this paper, a novel strategy for the fabrication of reduced graphene oxide (rGO)/Cu₈S₅/polypyrrole (PPy) composite nanosheets with Cu₈S₅ nanoparticles and PPy layer anchored on the surface of rGO as peroxidase‐like nanocatalyst is reported. During the synthesis, graphene oxide (GO)/CuO composite nanosheets are prepared first and used as templates, then the sulfuration of CuO and polymerization of pyrrole are accompanied with the reduction of GO, resulting in ternary rGO/Cu₈S₅/PPy composite nanosheets. The synthesized Cu₈S₅ nanoparticles with a diameter in the range from tens to hundreds of nanometers are dispersed within PPy decorated rGO nanosheets. The resultant ternary rGO/Cu₈S₅/PPy composite nanosheets exhibit a higher peroxidase‐like catalytic activity toward the oxidation of 3,3′,5,5′‐tetramethylbenzidine in the presence of H₂O₂ than GO/CuO and rGO/CuS composite nanosheets, revealing a synergistic effect on their activity. The as‐prepared rGO/Cu₈S₅/PPy platform provides a simple colorimetric approach for the detection of H₂O₂ and phenol with a high sensitivity. This work offers a new way for the fabrication of rGO‐based nanocomposite with superior enzyme‐like activity, which displays great potential applications in biocatalysis and environmental monitoring.     

液体火箭发动机中声腔抑制不稳定燃烧的声学分析

发展了声腔的分析和数值模型,对液体火箭发动机不稳定燃烧的抑制作用进行了评定,通过迭代计算研究了二维流动和温度分布变化对声腔调 谐和稳定性能的影响,对不同的声腔几何尺寸和温度梯度的稳定性计算结果表明,燃烧带有较大开口面积的声腔会更大程度地改变振荡的空间分布,这种改变而且影响了驱动和抑制燃烧的机理,讨论了在声腔设计安排中正确选择声腔的几何尺寸,且比较了不同长度和不同直径声腔的阻尼特性,通过考察声吸收系统的方法来最优化系统的阻尼,得到了可供设计参考的结论。     

Characterisation of precipitate phases in magnesium alloys using electron microdiffraction

Recent results of the characterisation of the structure, morphology and orientation of fine-scale, strengthening precipitate phases in selected magnesium alloys using transmission electron microscopy and microdiffraction are reviewed. The strengthening precipitate phases in Mg–Y–Nd alloys, aged to maximum hardness at 250°C, have been found to include two metastable precipitate phases β′ and β₁, and the equilibrium precipitate β. The β′ phase has a globular form, a base-centred orthorhombic structure (potential point group of mmm), and an orientation relationship such that (100)_β′//(1 10)_α, [001]_β′//[0001]_α. The β₁ phase has an f.c.c. structure (space group and an orientation relationship that may be described by (100)_β1//[0001]_α, and forms as plates parallel to The β phase has an f.c.c. structure (space group ) and also forms as plates on with an orientation relationship with the matrix phase that is identical to that observed for β₁ phase. Precipitates in Mg–Al alloys, aged isothermally at 200°C, invariably have the b.c.c. structure of the equilibrium precipitate phase β (Mg₁₇Al₁₂). Three orientation relationships have been observed between β and the matrix phase. Most precipitates have an irrational orientation relationship that approximates to the Burger's relationship, (001)_β//(0001)_α, and a faceted lath morphology with habit plane parallel to (0001)_α. A minor fraction of precipitates posses an orientation relationship that is of the form

Full-size image

and have a prismatic rod morphology. The long axes of these rods are parallel to [0001]_α, and their faceted surfaces are parallel to A few precipitates are observed to have an orientation relationship such that

Full-size image

and a rod shape, with their long axes apparently inclined with respect to [0001]_α.     

C60醛类衍生物非线性光学特性研究

研究了加合不同取代基团的C60醛类衍生物的光学非线性性质。利用简并四波混频（DFMW）方法获得了C60醛类各衍生物的三阶光学非线性超级化率γ^(3)及相应的三阶光学非线性系数χ^(3)值。同时也研究了它们各自的光限幅特性。结果表明：不同的取代基对C60醛类衍生物三阶光学非线性及光限幅特性的影响不同。     

Upconversion luminescence of Er/Yb-codoped natrium-germanium-bismuth glasses

The absorption and upconversion fluorescence spectra of a series of Er³⁺/Yb³⁺-codoped natrium-germanium-bismuth glasses have been studied. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er³⁺ based on the Judd-Ofelt theory. At room temperature, an upconversion efficiency of 6.1×10⁻² has been obtained for the green emission from the glass with 0.5 wt% Er₂O₃ and 3.0 wt% Yb₂O₃ pumped by 980 nm radiation with an intensity of 270 W/cm². And the “standardized” efficiency for green upconversion light is higher than that reported in lead-germanate, lead-tellurite-germanate, and silicate glasses. The results indicate that the Er³⁺/Yb³⁺-codoped natrium-germanium-bismuth oxide glass may be a potential material for developing upconversion optic devices.     

倒V形四能级亚飞秒极化拍的三光子吸收和色散

基于孪生色锁噪声场的互相关效应,从理论上研究了倒V形(RV)四能级飞秒量级差频极化拍与极化拍中五阶非线性极化率,并提出了用一种相位敏感的方法来研究多能级原子相干造成的三光子六波混频过程.在抽泵光束为窄带末端情况下,场关联对信号和极化率的影响都很弱,在非窄带情况下,场关联会使极化强度自相干信号和极化拍信号产生关于零延时的不对称性和时域扫描上的辐射与物质失谐阻尼振荡(RDO),而极化率会产生频域扫描上的RDO振荡.参考光信号是一路传播方向和六波混频信号稍有区别的双光于非简并四波混频信号.五阶非线性响应则由享生 关键词： 外差法 吸收 色散 非线性极化     

基于非线性偏振旋转效应的多波长光纤激光器

多波长光纤激光器是未来波分复用光通信系统的理想光源,提出和展示了一个基于非线性偏振旋转效应的多波长光纤激光器,非线性偏振旋转诱导的强度相关非均匀损耗能有效地抑制均匀加宽增益介质掺铒光纤中的模式竞争,从而使光纤激光器在室温下产生稳定的多波长输出,实验实现了最多18个波长的多波长输出.另外,此激光器没有使用传统的滤波器,而是在激光腔内插入一段保偏光纤,保偏光纤与偏振相关隔离器构成一等效Lyot双折射光纤周期性滤波器.利用这种在线型的双折射光纤滤波器简化了光纤激光器的结构,使它更易于集成.还实验研究了多波长输出随抽运功率的演化,发现抽运功率对多波长的均匀性影响很大.     

单光子纠缠态的纠缠转移和量子隐形传态

使用光学分束器和单光子源,利用单光子态和真空态制备出了纠缠单光子态.利用光学分束器作用和单光子探测,实现了三个通讯伙伴之间的纠缠转移.提出了一个关于纠缠单光子态的量子隐形传态方案.在这个方案中,被传送的是一个未知的单光子纠缠态.通讯双方使用的量子信道是两个单光子纠缠态.通过使用分束器作用和对输出态进行光子测量以及在经典信息的帮助下,纠缠转移和量子隐形传态的过程被完成.     

Computational insight into asymmetric uranyl‐salophen coordinated with α, β‐unsaturated aldehydes and ketones

The study of the catalytic activity and activation mechanism of asymmetric uranyl‐salophens with α, β‐unsaturated aldehydes or α, β‐unsaturated ketones, is a research hotspot. In this paper, the complexes of the uranyl–salophen(U‐S) modified by unilateral benzene, coordinated with cyclohexenone, cyclopentenone and acrolein, were investigated using density functional theory calculations at the level of B3LYP/6‐311G(d, p) basis set. The results showed that the uranyl‐salophen(U‐S) weakened the large π bond between C = C and C = O of the α, β‐unsaturated aldehydes and ketones, making the unsaturated aldehydes and ketones activated. In addition, the molecular‐recognition selectivity of the asymmetrical uranyl‐salophen for cyclohexenone and cyclopentenone were much higher than for acrolein.     

Novel identification approach for nonlinear systems with hysteresis

Nonlinear Dynamics - A new identification approach for a nonlinear system with hysteresis, namely a cascading Bouc–Wen hysteresis model with linear dynamics, is proposed in this study. The...