The Influence of Network Structural Properties on Information Dissemination Power in Microblogging Systems

The potential of microblogging networks to spread information, ideas, and influence via social links has been recognized. Individuals at central or critical positions in the microblogging networks are expected to play an important role in spreading information, but this belief must be tested with empirical investigations in actual information dissemination. Furthermore, it is possible that individuals with different types of structural importance influence the information dissemination in different ways. This article examines the impact of five structural properties (degree, betweenness, closeness, tie strength, and k-value) on information dissemination capabilities by tracking the dissemination of 150 messages in Sina Weibo. The results highlight the importance of betweenness centrality, which best explains the influence on information dissemination distance and coverage size. It also best predicts the information dissemination efficiency. Degree centrality is found to be a strong predictor of one’s influence among immediate followers. Tie strength negatively correlates with influence on the information dissemination distance and coverage size. These structural properties address different aspects of the information dissemination power and should be used in a complementary way when planning information dissemination strategies in microblogging systems.     

Fabrication and Microstructure Characterization of Ti3SiC2 Synthesized from Ti/Si/2TiC Powders Using the Pulse Discharge Sintering (PDS) Technique

Ti/Si/2TiC powders were prepared using a mixture method (M) and a mechanical alloying (MA) method to fabricate Ti₃SiC₂ at 1200°–1400°C using a pulse discharge sintering (PDS) technique. The results showed that the Ti₃SiC₂ samples with <5 wt% TiC could be rapidly synthesized from the M powders; however, the TiC content was always >18 wt% in the MA samples. Further sintering of the M powder showed that the purity of Ti₃SiC₂ could be improved to >97 wt% at 1250°–1300°C, which is ∼200°–300°C lower than that of sintered Ti/Si/C and Ti/SiC/C powders using the hot isostatic pressing (HIPing) technique. The microstructure of Ti₃SiC₂ also could be controlled using three types of powders, i.e., fine, coarse, or duplex-grained, within the sintering temperature range. In comparison with Ti/Si/C and Ti/SiC/C mixture powders, it has been suggested that high-purity Ti₃SiC₂ could be rapidly synthesized by sintering the Ti/Si/TiC powder mixture at relatively lower temperature using the PDS technique.     

湿浸法制备活性组分非均匀分布负载型催化剂过程的计算机模拟

对活性组分非均匀分布的负载型催化剂的湿浸法制备过程进行了计算机模拟,其模拟程度可适用于任意多个活性组分的浸渍。发现单组分浸渍时,通过控制浸渍时间可获得活性组分由薄到厚的蛋壳型分布和均匀分布,但通过预浸渍吸附至一定分布后,再在空白溶液中浸渍洗脱,控制洗脱条件也可获得蛋黄、蛋白型的分布;加入竞争吸附剂,进行双组分及多组分浸渍,通过控制浸渍溶液性质及浸渍时间可获得各种类型的活性组分分布,诸如蛋壳型、蛋白型、蛋黄型和均匀型。通过对制备过程参数(如竞争吸附剂的选择、各组分有效扩散系数、初始浓度、吸脱附速率常数等)与活性组分分布形式之间关系的分析,可实现对任一分布形式的催化剂的制备过程参数的优化。这对实际制备催化剂具有指导意义。     

Observer‐based H ∞ control for networked systems with bounded random delays and consecutive packet dropouts

This paper is concerned with the H _∞ control problem for a class of systems with bounded random delays and consecutive packet dropouts that exist in both sensor‐to‐controller channel and controller‐to‐actuator channel during data transmission. A new model is developed to describe possible random delays and packet dropouts by two groups of Bernoulli distributed stochastic variables. To avoid the state augmentation, a full‐order observer‐based feedback controller is designed via LMI approach. Based on the Lyapunov theory, a sufficient condition is provided to guarantee the closed‐loop networked system to be asymptotically mean‐square stable and achieve the prescribed H _∞ disturbance‐rejection‐attenuation level. The simulation examples illustrate the effectiveness of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

一种通过USB接口的可靠固件升级技术

本文提出一种可靠固件升级的技术。该技术采用外部主晶振,工作异常时自动切换到校准后的内部晶振,还使用了DFU检测序列、看门狗等方法。相对于传统的固件升级技术,该技术具有抗干扰能力强、可靠、易于使用等优点。     

Spartan6芯片μC/OS-Ⅱ的可抢占式嵌套中断控制方法

介绍了Spartan6芯片搭载MicroBlaze软核的硬件平台,以及集成了μC/OS-Ⅱ操作系统的软件平台;给出了在此软硬件平台上的可抢占、可嵌套的中断机制的实现方法;灵活地运用面向底层硬件代码与操作系统代码之间的参数传递,协调了中断处理与任务调度之间的关系。阐述了方案的原理,给出了程序流程图;通过试验,验证了可抢占、可嵌套的中断机制的正确性与可行性。     

关于．Net中内存泄露的探讨

一直以来内存泄露都是程序员们非常关心的一个大问题,通过借助一些工具,程序员可以查找到程序中存在的内存泄露的问题。内存溢出的出现会给程序员带来很多的烦恼。本文针对．NET环境中的内存泄露问题进行分析并指出应如何正确使用c#的垃圾回收机制。     

多媒体技术在高校教学中的应用

多媒体技术运用在高校音乐教学课堂中,不仅能为高校学生们营造一个生动的学习环境,吸引学生的兴趣,还能让学生直观地欣赏音乐,从而在在轻松的氛围中学习音乐知识,提高自己的音乐鉴赏水平。本文主要研究多媒体技术在高校音乐教学中的作用以及多媒体技术在高校音乐教学中的具体应用。     

成核剂对不同特性粘数PET结晶性能的影响

研究了新型复合成核剂水滑石(HT)／离聚物(Surlyn8920)／聚乙二醇(PEG)对不同特性粘数聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过差示扫描量热仪测试了PET的结晶峰温度T_(mc)和熔融峰温度(T_m)。结果表明,复合成核剂各组分及PET的质量比为0.5:3.0:3.0:100.0时,各种PET的过冷度(T_m-T_(mc))均显著减少．半结晶时间(1gt_(1／2))也明显降低。而且,复合成核剂对不同特性粘数PET结晶性能的改善是一致的。     

Crystal lattice deformation and the mesophase in poly(ethylene terephthalate) uniaxially drawn by solid-state coextrusion

The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio (EDR) up to 4.4 and at an extrusion temperature (ET) above T_g, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the T_g of PET differ markedly from those made above T_g. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below T_g) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase.