SDH设备应用的优势

本文介绍了SDH发展的历程,以及它的基本原理和作为SDH基础设备的功能和特点,介绍了SDH设备定时同步特点,着重介绍了SDH设备在实际应用中作为分/插复器及在自愈环中的应用,预测了今后的发展方向.     

无线传感器网络节点定位的移动信标节点路径规划

为了进一步提高无线传感器网络节点定位精度和覆盖率,本文在采用移动信标节点来对未知节点进行定位方面,提出了信标节点向最大覆盖未定位节点方向移动的路径规划算法,解决了信标节点的移动路径规划问题.仿真实验表明,和信标节点随机方向移动算法相比,该算法具有较好的定位性能,能很好地适应大规模随机不均匀撒布节点的应用需求.     

一种密集部署传感器网络的分簇算法

针对分簇算法中的重新分簇所带来的高负载问题,提出了一种基于完全图的能量有效的分簇算法(CGCA),系统启动时刻,CGCA把网络划分成多个完全图,每个完全图独立成簇.CGCA利用完全图中节点之间是等价的性质,只是在系统启动的时刻执行分簇算法,而在以后的重新选举簇头阶段,簇头只需要在每个簇的内部节点间进行轮换,而不是像以前的分簇算法需要进行全局性的触发来选举簇头,这使得CGCA的通信和计算负载可以大量减少,它在单个节点的处理复杂度和消息复杂度均为O(1).另外,通过优先选择距离簇头近的节点加入簇内,CGCA不仅减少了簇头和簇内成员的簇内通信能量,而且使得簇头比较均匀地分布在部署区域.仿真实验表明:在节点密集部署的情况下,CGCA产生的消息交换个数远小于HEED分簇算法,最后在簇头均匀分布方面,CGCA也明显优于LEACH分簇算法.     

基于容量约束的WSANs路由算法的研究

在无线传感反应网络通过引入具有丰富资源、甚至可以移动的反应节点,极大地增强了现有的无线传感器网络的功能和应用范围.针对距离反应节点越近传感节点能量消耗越快的问题,研究了基于容量约束的最大跳数最小化的问题,并在此基础上提出了一种全局近似算法.仿真实验表明,该算法能通过设置节点的容量约束,限制节点每轮转发某个事件的最大报文数,以降低单个节点的最大能耗,达到延长网络生存时间的目的.     

基于用户聚类的播客节目推荐

许多播客推荐机制一般根据整体点击次数来向用户推荐节目,但是一些点击次数很高的节目未必就是某类用户所喜欢的,因而推荐的节目对用户的喜好针对性不是很强.为了提高推荐节目对用户喜好特点的针对性,提出基于用户聚类的节目推荐.对用户在播客平台上的采集数据进行聚类分析后,把用户归为某一类型,并把该类型的所有节目根据点击次数多少存放入相应的推荐表.在用户下次登录时,根据其所属用户类型从推荐表中选出其最可能观看的尚未浏览的节目.试验结果证明,该播客推荐系统能很好地根据用户的喜好特点来进行针对性节目推荐.     

基于JNI的MATLAB图形显示在船舶数字化平台的应用

二维图形的显示是船舶数字化平台中一个重要的功能,采用纯粹的JAVA画图方式效果比较差,有些船舶专用的一些符号难以显示,并且图像不是很清晰,还涉及到相当复杂的编程,给整个船舶数字化平台带来很多的不便,而利用JAVA通过VC+ +实现MATLAB 的二维图形处理和显示,实现了船舶数字化平台的性能可视化和船型可视化,图像比较清晰,并且可以达到开发的需要,取得了良好的效果.     

如何提高VB课堂教学效果

在VB程序设计语言课程教学中,教师怎样解决程序设计的“难学难教”问题,并提高课堂教学效果,是目前亟需解决的问题,本文就此在教学中做了一些探索。     

Tailoring of Photoluminescence Properties in All-Vacuum Deposited Perovskite via Ruddlesden–Popper Faults

Ruddlesden–Popper (RP) faults are well known in oxide perovskites, and are also observed in promising metal halide perovskites. However, the effect of RP faults on optical properties of perovskite has not been systematically investigated. In this study, it is found that RP faults are common planar faults in all-vacuum deposited CsPbBr₃-based perovskite polycrystal thin films, and the density of RP planar faults can be greatly increased by non-stoichiometric composition (Cs-rich) as well as reduced dimensionality (quasi-2D) strategies. The photoluminescence (PL) measurement reveals monotonically increasing peak intensities with higher densities of RP planar faults from Cs-rich, quasi-2D to Cs-rich & quasi-2D samples. The corresponding atomic-scale differential phase contrast maps indicate strongly confined charges within the RP planar fault network, which explains well the relationship between PL enhancement and the density of RP planar faults, and offers an alternative pathway for tailoring the optoelectronic properties of perovskite.     

Exploring a Stable and Dense 3D Lead Chloride Hybrid with Emission of Self-Trapped Excitons toward X-Ray Scintillation

The exceptional photophysical properties of 3D organic–inorganic lead halide hybrids (OILHs) endow their significant potential for usage in optoelectronics, which has sparked intense research on novel 3D OILHs and associated applications. However, constructing new 3D OILHs based on large organic cations suffers from tough challenges due to the limitation of the Goldschmidt tolerance factor rule, let alone further explorations of their practical applications. Herein, a brand-new 3D lead chloride hybrid, (1MPZ)Pb₄Cl₁₀·H₂O ( 1 , 1MPZ = 1-methylpiperazine) is reported, featuring a dense 3D lead chloride framework made of the corner-, edge-, and face-shared lead chloride polyhedra. 1 presents a broadband white light emission with a large Stokes shift and a nanosecond photoluminescence lifetime, which originates from radiative recombination of self-trapped excitons (STEs) induced by the highly distorted structure. Such a reabsorption-free and fast-decayed STEs emission coupling with the dense 3D architecture further enables 1 with effective X-ray scintillation with good sensitivity. Impressively, 1 also shows superior environmental and radiation stability. This study provides a new 3D OILH with appealing luminescence, not only expanding the 3D OILH family but also inspiring the exploitation of their optoelectronic applications.     

Indirect Exciton–Phonon Dynamics in MoS2 Revealed by Ultrafast Electron Diffraction

Transition metal dichalcogenides layered nano-crystals are emerging as promising candidates for next-generation optoelectronic and quantum devices. In such systems, the interaction between excitonic states and atomic vibrations is crucial for many fundamental properties, such as carrier mobilities, quantum coherence loss, and heat dissipation. In particular, to fully exploit their valley-selective excitations, one has to understand the many-body exciton physics of zone-edge states. So far, theoretical and experimental studies have mainly focused on the exciton–phonon dynamics in high-energy direct excitons involving zone-center phonons. Here, ultrafast electron diffraction and ab initio calculations are used to investigate the many-body structural dynamics following nearly- resonant excitation of low-energy indirect excitons in MoS₂. By exploiting the large momentum carried by scattered electrons, the excitation of in-plane K- and Q- phonon modes are identified with 𝑬^′ symmetry as key for the stabilization of indirect excitons generated via near-infrared light at 1.55 eV, and light is shed on the role of phonon anharmonicity and the ensuing structural evolution of the MoS₂ crystal lattice. The results highlight the strong selectivity of phononic excitations directly associated with the specific indirect- exciton nature of the wavelength-dependent electronic transitions triggered in the system.