One‐Pot Synthesis of Algae‐Like MoS2/PPy Nanocomposite: A Synergistic Catalyst with Superior Peroxidase‐Like Catalytic Activity for H2O2 Detection

A facile one‐pot synthetic route is reported to prepare algae‐like molybdenum disulfide/polypyrrole (MoS₂/PPy) nanocomposite through a redox reaction between ammonium tetrathiomolybdate and pyrrole monomer under a hydrothermal condition without any other templates. The as‐prepared unique algae‐like MoS₂/PPy nanocomposites are composed of few layer MoS₂ nanosheets, which are covered with PPy. Structural and morphological characterizations of this unique nanocomposite are investigated by Fourier‐transform infrared spectra, Raman spectra, X‐ray diffraction pattern, X‐ray photoelectron spectra, energy‐dispersive X‐ray spectroscopy, and transmission electron microscopy. The as‐prepared MoS₂/PPy nanocomposites exhibit an excellent peroxidase‐like catalytic activity toward the oxidation of 3,3,5,5‐tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂) in acetate buffer solution (pH 4.0), which provides a facile strategy for the colorimetric detection of H₂O₂ with a high sensitivity.     

一种基于BLT方程的孔缝箱体屏蔽效能计算方法

本文基于等效电路法, 提出一种通过BLT方程计算带孔缝箱体屏蔽效能的方法, 可以快速准确计算任意入射、极化平面波照射箱体以及任意位置开孔和双面开孔箱体的屏蔽效能. 根据等效电路法求解出孔缝散射矩阵, 依据信号流图建立传播关系和散射关系方程, 并推导出包含孔缝耦合效应的广义BLT方程. 将BLT方程计算结果与等效电路法计算结果以及CST仿真做对比, 验证了方法的正确性. 与等效电路法相比, 在同一孔阻抗下, 孔缝散射矩阵包含箱体内外能量之间的相互耦合作用, 本方法计算结果精度更高, 能预测更多箱体谐振模式; 与CST仿真相比, 本方法占用时间和资源少, 可以对箱体参数进行规律性研究.     

PM2.5大气污染对自由空间量子通信性能的影响

近年来, PM2.5大气污染日益严重, 不仅影响空气质量与大气能见度, 而且还会对自由空间量子光信号的传输造成影响. 然而, 有关PM2.5与自由空间量子通信信道参数关系的研究, 迄今尚未展开. 本文根据PM2.5粒度谱分布函数及其化学成分的消光份额, 提出了PM2.5指数、大气湿度与自由空间量子信道衰减的关系; 针对幅值阻尼信道和退极化信道, 分别建立了PM2.5污染程度与信道容量、信道平均保真度、信道误码率的定量关系. 仿真结果表明, 当大气湿度为30%, PM2.5指数分别为50和300时, 自由空间量子通信信道容量、信道平均保真度、信道误码率分别依次为0.83和0.21, 0.91和0.56, 0.0048和0.0192. 由此可见, PM2.5污染程度对自由空间量子通信性能有显著的影响. 因此, 为了提高自由空间量子通信的可靠性, 应根据PM2.5大气污染状况, 自适应调整系统的各项参数.     

Ge-Se基硫系玻璃在通信波段的三阶非线性与光谱特性研究

在Ge-Se二元体系中引入相同摩尔比的Ga, Sn, Sb, Te四种元素, 使用熔融淬冷法制备了一系列硫系玻璃. 利用吸收光谱获得了不同元素引入下硫系玻璃能带结构的变化, 并结合拉曼光谱详细研究了产生光学特性变化的微观表征. 使用Z扫描方法测试了各个硫系玻璃样品在1550 nm波长下的三阶非线性参数, 发现加入Sn的玻璃的三阶非线性折射率n₂最大, 达到了6.36×10^-17 m²/W, 且其品质因子大于23, 表明Sn引入能够增强硫系玻璃在通信波段的三阶非线性, 这一研究结果为以后的高性能红外器件的设计及制备提供了一种环保且性能优良的候选材料.     

基于分组交换的量子通信网络传输协议及性能分析

量子纠缠交换能够建立可靠的量子远程传输信道, 实现量子态的远程传输. 然而, 基于纠缠交换的量子信道要求网络高度稳定, 否则会浪费大量纠缠资源. 为节省纠缠资源, 本文根据隐形传态理论, 提出了一种基于分组交换的量子通信网络传输协议, 建立了发送量子态所需的纠缠数目与所经过的路由器数、链路错误率的定量关系, 并与纠缠交换传输协议进行了比较. 仿真结果表明, 在链路错误率为0.1% 时, 分组传输协议所使用的纠缠数目少于纠缠交换的数目, 另外, 随着错误率的升高, 分组传输协议所需的纠缠数比纠缠交换协议明显减少. 由此可见, 基于分组交换的量子通信网络传输协议在网络不稳定时, 能够节省大量纠缠资源, 适用于链路不稳定的量子通信网络.     

近地面大气湍流平均动能耗散率测量与分析

用三维超声风速计测量了合肥地区风速脉动和温度脉动数据,并用二阶和三阶径向风速结构函数以及相似理论估算了湍流动能耗散率,估算结果基本一致.其与稳定度相关性分析表明.在大气处于中性条件下,湍流动能耗散率最大,并随|z/L|值增大而下降;Kolmogorov耗散尺度η与ε1/4成反比,其与稳定度z/L的变化趋势与ε随z/L的变化趋势正好相反;C2n在大气处于中性条件下最小,并随|z/L|值的增大而增大,但在不稳定条件下C2n增大得更快.热力湍流内尺度不能用湍流动能耗散率ε进行计算,而应引入与温度θ梯度有关的耗散率εθ.     

在质量块冲击作用下刚架大挠度响应的实验研究

本文报道刚架跨中受到以不同速度运动的质量块冲击时动态大挠度响应的实验研究工作,实验测取了冲击点位移、速度随时间变化的曲线及某些关键点的动态应变历史,由此描述了在响应过程中,质量块与刚架间动量动能的传递过程,找出了塑性区域形成和扩展的规律。研究表明:初始撞击接近于理想非弹性,动态荷载不宜简化为瞬时冲量,此时初始冲击动能与刚架所能吸收的最大弹性能之比即便很大,响应中弹性成分仍占有很大的比例,能量比率作为判断是否宜于采用刚塑性解答的条件已不再充分;刚架在初始撞击中吸收的能量和冲量与初始动能和动量之比,仅与刚架承受初始撞击的相当质量和冲击物质量之比有关,而与冲击速度无关,文中给出了二者的关系式。     

Finding optimal hyperpaths in large transit networks with realistic headway distributions

This paper implements and tests a label-setting algorithm for finding optimal hyperpaths in large transit networks with realistic headway distributions. It has been commonly assumed in the literature that headway is exponentially distributed. To validate this assumption, the empirical headway data archived by Chicago Transit Agency are fitted into various probabilistic distributions. The results suggest that the headway data fit much better with Loglogistic, Gamma and Erlang distributions than with the exponential distribution. Accordingly, we propose to model headway using the Erlang distribution in the proposed algorithm, because it best balances realism and tractability. When headway is not exponentially distributed, finding optimal hyperpaths may require enumerating all possible line combinations at each transfer stop, which is tractable only for a small number of alternative lines. To overcome this difficulty, a greedy method is implemented as a heuristic and compared to the brute-force enumeration method. The proposed algorithm is tested on a large scale CTA bus network that has over 10,000 stops. The results show that (1) the assumption of exponentially distributed headway may lead to sub-optimal route choices and (2) the heuristic greedy method provides near optimal solutions in all tested cases.     

Blaschke isoparametric hypersurfaces in the conformal space ℚ 1 n+1 , I

Let x : M → Q₁ⁿ⁺¹ be a regular hypersurface in the conformal space Q₁ⁿ⁺¹. We classify all the space-like Blaschke isoparametric hypersurfaces with two distinct Blaschke eigenvalues in the conformal space up to the conformal equivalence.     

Identification of the Active Sites for Low Temperature CO Oxidation over Nanocrystalline Co3O4 Catalysts

The microstructural properties of dry‐grinding derived Co₃O₄ catalysts pretreated under different atmospheres, in relation to the activities on CO oxidation were investigated. The Co₃O₄ synthesized by soft reactive grinding and pretreated with O₂ resulted in the best activity, with 100% conversion of CO at ?52 °C, superior to that of Co₃O₄ pretreated with He. To find out the active sites on Co₃O₄ for low temperature CO oxidation, the characterizations of the cobalt oxides had been investigated by means of N₂ physisorption, XRD, TEM, H₂‐TPR, CO‐titration, XPS and O₂‐TPD technologies. XPS of Co2p results show that it is difficult to ascribe the difference in catalytic performance to the surface concentration of active Co³⁺ sites. A correlation between the activity and the CO‐titration and O₂‐TPD results for Co₃O₄ reveals that a high abundance of readily accessible superficial electrophilic oxygen (O^?) species is important for achieving a high activity. Therefore, CO oxidation takes place on the surface active oxygen sites in Co₃O₄ crystallites via the suprafacial mechanism.