移动Ad hoc网络基于干扰和连通度的路由协议

移动Ad hoc网络中,节点随机移动会引起通信链路频繁断开,从而导致路由失效,带来大量的路由重建与路由发现,耗费了有限的网络资源。传统按需路由中,采用简单的洪泛进行路由发现,路由请求包的盲目转发会带来大量不必要的冗余转发,造成广播风暴问题。此外,大量的数据包同时发送也会对彼此的传输造成干扰,增加数据包冲突概率。针对这种情况,本文提出一种基于干扰和连通度的路由协议,该协议结合节点的连通度和潜在干扰设计转发概率,不仅减少了路由请求包的传播范围,还减少了路由请求包的冲突概率,提高了传输成功率。仿真结果表明,本文设计的方案在减少路由开销的同时,有效提高了数据包投递率,从而提高了路由性能。     

微电铸技术及其工艺优化进展研究

随着微机电系统(MEMS)和微影微电铸微模铸(LIGA)两种技术的发展,微电铸工艺正逐渐展现着其独特的魅力和发展潜力。然而,现有工艺中存在的缺陷也严重阻碍了其进一步发展。因此,对微电铸工艺进行深入研究,突破其工艺瓶颈,将对微加工工艺的应用和推广起着重要作用。着眼于目前微电铸工艺中存在的不足,从工艺缺陷的理论形成机理出发,总结了近期微电铸领域在工艺缺陷的改进方面所做出的努力及成果,并对微电铸工艺未来的发展趋势提出了一些看法。     

SWAN模型速率控制模块性能分析及改进

SWAN是Ad Hoe网络中的一种无状态网络协议,利用分布式控制算法来传递分类服务。这种QoS模型把数据业务分为两类进行不同处理,即对尽力而为的UDP和TCP业务采用速率控制的策略而对实时的UDP业务采用基于源节点的接纳控制策略。本文修改了SWAN模型的速率控制模块,引入队列调度机制,对从上层来的尽力而为数据包进行排队、调度,使其尽可能公平地占用新到资源。在分析中具体给出了修改后速率控制模块的实现过程。通过仿真分析了AIMD算法的参数对修改后速率控制模块性能的影响。     

一款高效率频率选择表面圆-线极化转换器

为了实现圆极化波到线极化波的高效率转换,提出了一种由两种圆极化波调制模块构成的复合结构单元频率选择表面圆-线极化转换器。采用天线-馈线-天线结构设计了左-左旋和左-右旋两种圆极化调制模,并将二者组合形成具有左旋圆极化波接收、左旋和右旋圆极化波同幅同相辐射功能的圆-线极化转换器。仿真与测试结果表明,该极化转换器能够将入射左旋极化波转换成线极化波,3 dB传输系数相对带宽大于19.8%,工作带宽内的圆-线极化转换率大于0.99。该极化转换器具有插入损耗低、设计原理易于推广等优势。     

Remarkable Antibacterial Activity of Reduced Graphene Oxide Functionalized by Copper Ions

Despite long-term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two-orders-of-magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm ). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu²⁺ into Cu⁺, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells.     

频率选择表面在节能玻璃中的应用研究

在现代建筑设计中,节能玻璃得到了越来越广泛的应用。节能玻璃表面镀上了一层阻性金属氧化物,这层金属氧化物能有效地屏蔽射向室内的红外线,同时将室内物体所辐射的长波保留在室内,能够起到很好的隔热作用并提高能量利用率,从而使建筑物冬暖夏凉。需要指出的是,阻性金属氧化物表面对移动信号、GPS等电磁波的衰减高达30dB。通过将金属氧化物层刻蚀出具有带通特性的频率选择表面（Frequency Selective Surface,FSS）单元,可以保证在阻隔红外线能量的情况下大大提高微波射频信号的透波率。本文在节能玻璃上设计了3种不同的带通FSS,与以往文献提出的十字形FSS相比,能够在保证900～2000MHz频段信号同等透波率的情况下,隔热效果更好。     

Improving satellite services with cooperative communications

This paper proposes new transmission schemes for the delivery of satellite services. In the proposed scenarios, mobile terminals are allowed to forward the signal received from the satellite. This scheme provides spatial diversity just like MIMO transmission schemes. Moreover, the coverage area is extended because masked terminals have an additional opportunity to get the service from neighboring terminals. We use the paradigm of cooperative communications to compare the advantages and limitations of several scenarios in hybrid terrestrial/satellite systems. In particular, we study the following basic transmission scheme: in a first time slot, the satellite sends its signal and, in a second time slot, mobile terrestrial terminals are relaying the satellite signal. An analysis framework is proposed and applied to this cooperation scenario at the destination terminal. The framework is modeling the cooperation process and clearly separates the control part from the data user part. The paper outlines the importance of the control part by evaluating the relay selection policy on a basic hybrid satellite/ad hoc system. Copyright © 2011 John Wiley & Sons, Ltd.     

Detecting unauthorized and compromised nodes in mobile ad hoc networks

Security of mobile ad hoc networks (MANET) has become a more sophisticated problem than security in other networks, due to the open nature and the lack of infrastructure of such networks. In this paper, the security challenges in intrusion detection and authentication are identified and the different types of attacks are discussed. We propose a two-phase detection procedure of nodes that are not authorized for specific services and nodes that have been compromised during their operation in MANET. The detection framework is enabled with the main operations of ad hoc networking, which are found at the link and network layers. The proposed framework is based on zero knowledge techniques, which are presented through proofs.     

无人机自组网技术综述与发展展望

无人机自组网(Unmanned Aerial Vehicle Ad Hoc Network,UAVANET)主要应用于现代数字科技战场,具备传统无线自组织网络的快速组网、多跳传输和多任务协作等特点,同时拥有更高的抗毁性.无人机自组网能确保网络运行的灵活性和顽健性,但是在实际组网过程中,网络结构和组网方式的不同对作战能力...     

A Novel Routing Protocol for Supporting QoS for Ad Hoc Mobile Wireless Networks

The main purposes of this article are to lessen the influence of the fastchanging network topology, rapidly varying bandwidth information, and the increasing size of routing tables onquality of service routing. Based on DSDV (Destination-Sequenced Distance-Vector) routing protocol formaintaining up-to-date routing information, the related research has to update routing tables when networktopology changes; moreover, the routing tables must be updated periodically even though the networktopology has not changed. To put emphasis on QoS routing, they also have to exchange routing tables by thetime of bandwidth information changes. Furthermore, the size of routing tables increases with the numberof mobile nodes; therefore, the precious wireless bandwidth is wasted on transmitting the large-scalerouting tables. In this article, we propose an on-demand-based QoS routing protocol to mitigate theseproblems and to achieve the QoS requirement. The goal of this article is to discover an optimal routewith minimum time delay for transmitting real-time data from a source node hop by hop to adestination node under some predefined constraints. Our contributions are as follows: our researchprovides a rigorous bandwidth definition and bandwidth application, a broad view of bandwidth calculationand reservation, minimizing the size of control packets and the number of control packet transmissions,and an efficient QoS routing protocol.