预处理对聚吡咯/羊毛复合导电纱线性能的影响

为了改善聚吡咯/羊毛复合导电纱线的导电性,采用化学原位聚合的方法,以纯羊毛纱线为基材,以吡咯为单体,三氯化铁为氧化剂,十六烷基三甲基溴化铵为掺杂剂,制备了聚吡咯/羊毛复合导电纱线。根据羊毛纤维湿热条件的拉伸特性,采用机械拉伸和机械/化学试剂共同作用的方法,改变羊毛纤维的鳞片结构和表面性质,增加吡咯与羊毛纤维的反应位点。为了进一步提高复合导电纱线的导电性,采用多次负载的方法,增加聚吡咯在羊毛纱线上的负载。实验结果表明:经过预处理后的聚吡咯/羊毛复合导电纱线具有较高的强力和较低的初始模量,其导电性能大大提升,电阻值由未经处理的730Ω/cm下降到34.83Ω/cm。     

机会网络中的数据转发机制分析

机会网络作为一种新兴移动无线自组织网络,在军事及民用领域展现出广泛的应用前景,数据转发机制是其核心问题。论文针对机会网络中的数据转发机制展开讨论,首先对机会网络数据转发机制与传统路由机制进行综合比较,在此基础上介绍数据转发机制面临的问题和性能评估标准,并根据数据转发机制主要特点对其进行了分类,最后对机会网络中的典型数据转发机制进行归纳。     

An image information hiding algorithm based on grey system theory

On the basis of grey system theory, an image information hiding algorithm is proposed in this paper. First, to choose the blocks of rich texture, a method based on two‐dimensional grey relational analysis is designed; making use of the improved GM(1,1) prediction model, the secret image is compressed losslessly, and then scrambled by means of time‐division multiplexing method in communication theory. Block discrete cosine transform is applied to the chosen blocks, and coefficients of mid frequencies are chosen as the embedded data, whereas the embedding intensity is determined on the basis of human visual system, and the embedding capacity of sub‐blocks can be controlled by its two‐dimensional grey relational grade adaptively. The experiment results show that the algorithm cannot only achieve satisfactory invisibility and robustness, but also improve the payload of the cover image, and meanwhile solve the problem that the small capacity of traditional algorithms in transform domain efficiently. Copyright © 2013 John Wiley & Sons, Ltd.     

一种网格资源信息真实性的验证方案

资源管理是网格应用的基础,资源信息的真实性直接影响网格资源发现、分配、作业调度,从而影响网格应用的效率。目前研究的热点倾向于网格资源使用者的身份和权限的确认,文章提出一种网格资源信息真实性的验证方案,介绍了方案的部件,分析其可行性,重点对其中的关键技术进行了阐述。     

融合信道分配的无线Mesh网络多目标网关部署

信道分配和网关部署是无线Mesh网络规划面临的重要挑战,作为影响网络性能的关键问题,传统上针对它们的研究都是独立的.为了有效结合二者规划网络,提升网络性能,提出了一种无线Mesh网络联合信道分配和网关部署策略,综合考虑了最小化链路冲突量和网关部署代价,在部署网关过程中有效地分配信道以消减无线链路间干扰.利用链路冲突量衡量网关附近节点流量聚集的特征,使用基于多目标粒子群算法来优化信道分配和选择部署网关,在信道分配和网关选择已定的情况下构建了负载均衡的转发树.仿真结果表明,相对于基于平面网络的均衡信道分配网关部署算法,该算法可以有效降低网络干扰、优化网络性能、减少节点路径长度,实现了网关间的负载均衡.     

一种带轻便控制引擎的无线传感器网络节点设计

介绍了一种以低功耗单片机ATmega128L为核心的无线传感器网络节点的设计方案。所实现的无线传感器网络硬件平台由一个轻便的控制引擎支持,以开放、模块化控制架构来适应具有高度分布性的应用环境,在降低无线传感器网络硬件系统的价格和能耗的同时,提高了系统的开放性、灵活性和可扩展性。     

基于IP协议的卫星组网通信关键技术研究

早期卫星组网一般采用地球同步卫星(GEO)作为中继器，而现在的卫星宽带信息网则是通过星间链路(ISL)实现相邻卫星之间直接通信，研究宽带卫星组网技术对于加快我国信息基础设施建设具有极其重要的作用。本首先介绍卫星通过星间链路组网通信的系统模型，然后分析卫星网络IP系统的协议堆栈，并对卫星网络TCP/IP协议各层采用的接口和协议、基本功能、工作方式等进行详细研究，最后对卫星组网通信中涉及的物理层、数据链路层和网络层的关键技术逐一进行了探讨。     

“Nano‐Fishnet” Structure Making Silk Fibers Tougher

Based on the combined technologies of atomic force microscopy, X‐ray diffraction/scattering, Fourier transform infrared spectra analysis, etc., it is demonstrated that the nano‐fishnet‐like networks, one of the most flexible but toughest structures, turn out to be the basic structure of silk filaments. The force patterns of pulling individual fibrils allow the identification of the pathways of unfolding protein segments in stacking β‐crystallites, which reveal the fishnet‐like topology. The calculation shows that the β‐crystallites in silk nanofibrils are the cross‐linking points of the nano‐fishnets, which may enhance the toughness of silk filaments up to 1000 times, compared with amyloid‐like and unlinked string structures. It follows that the strong β‐sheet–β‐sheet interaction, a high degree of ordering, and a high density of β‐crystallites in silk fibers toughen the fishnet structure, then strengthen silk filaments, in consistency with the experiments for both spider and silkworm silks. The knowledge on the fishnet structure of silk fibers sheds light on the design and synthesis of either protein or synthetic fibers of ultraperformance in a more generic way.     

Graft mechanism of acrylonitrile onto starch by potassium permanganate

The graft mechanism of acrylonitrile (AN) onto starch under the initiation of potassium permanganate was investigated. The relationships of the grafting rate and the concentrations of potassium permanganate, AN, and backbone starch, as well as the reaction temperature, were established. On this basis, the equation for the rate of the graft copolymerization was derived, and the apparent activation energy for the graft copolymerization was obtained. Through the study of the oxidation reaction of starch with manganic ions, the valence changes of manganic ions during the graft copolymerization, and the grafting ability of different starch derivatives, together with electron spin resonance analysis, the grafting mechanism for the graft copolymerization of AN onto starch under the initiation of potassium permanganate was determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 146–152, 2003     

Carburization of 310 stainless steel exposed at 800-1100 °C in 2%CH4/H2 gas mixture

Carburization of 310 stainless steel has been investigated after cyclic exposures at high temperatures 800-1100 °C in a 2%CH₄/H₂ carburizing gas mixture for 500 h duration. A thermodynamic analysis indicates that 1000 °C is an approximate boundary temperature, below which the environment should result in mixed oxidizing/carburizing behavior, while above this temperature reducing/carburizing behavior should occur. The experimental results agree well with the thermodynamic analysis. Below 1000 °C, 310SS suffered external carburization, oxidation, and internal carburization. In excess of 1000 °C, extensive external carburization occurred and internal Cr-carbides disappeared. Cr segregation is proposed to interpret the effect of temperature on the continuity of an external scale layer and carburization behavior.