生太网络的结构和动力学特征

生态学家一直以来都在研究物种之间的相互作用.然而,几乎所有这些工作都只关注于单一类型的相互作用网络.例如,生态学家已经研究了对立关系,比如食物链上的捕食关系;

高效高带宽利用率的太赫兹无线网络定向MAC协议

现有太赫兹无线定向网络中,随着网络规模的扩大,用于节点接入网络的Beacon帧长度不断变长,导致过多的控制开销;同时,由于定向天线的使用,中心控制节点需要在全方向各个扇区发送多个Beacon帧,随着扇区数目的增加,Beacon时段的长度和在整个超帧中的占比也会随着增加,由于超帧的长度是固定的,Beacon时段过长的时隙占用会导致更少的时隙用于传输数据,浪费信道资源.针对上述问题,本文提出一种高效高带宽利用率的太赫兹无线网络定向MAC协议—HEBU-MAC.本协议采用基于常短帧精简Beacon帧机制减少了Beacon帧的长度,采用基于常短时隙压缩基本时隙机制压缩基本时隙的长度,减少了Beacon时段的时隙占用,从而极大地降低了控制开销,提高了信道利用率.

高效低碰撞的太赫兹无线定向MAC协议

针对网络中节点在争用访问时期发送消息碰撞、时隙分配机制低效和空闲时隙浪费等问题,提出了一种高效低碰撞的太赫兹无线定向MAC协议.文中提出了3种新机制,分别是基于缓存权重的分组机制、复用竞争机制以及时隙分配机制.首先,在微网控制器(Piconet Coordinator,PNC)中生成缓存映射表记录节点的缓存情况;然后,根据缓存映射表为节点分组,节点在分组对应的时隙中进行时隙请求,PNC根据节点缓存为节点分配时隙;最后,未申请到时隙的节点利用剩余时隙进行复用竞争操作.仿真结果表明,所提出的方案有效地提高了网络的吞吐量,减少了消息碰撞率并降低了平均时延.

太赫兹网络中基于中继协作转发的高效双信道MAC协议

针对现有多输入多输出(Multiple-Input Multiple-Output,MIMO)太赫兹通信网络双信道MAC协议存在波束重叠干扰和冗余控制开销等问题,提出了一种太赫兹网络中基于中继协作转发的双信道MAC协议(High Efficiency Dual channel MAC Protocol Based on Relay Cooperative Forwarding in Terahertz Networks,HE-RCFMAC)。HE-RCFMAC协议包含动态帧聚合、基于位置信息自适应协作转发和精简RTS(Request To Send)/CTS(Clear To Send)帧三种机制。经三种机制处理后,可有效提升信道利用率,同时减小控制开销,提高数据传输成功率和整体网络吞吐量。仿真结果表明,所提协议与现有的MIMO太赫兹双信道MAC协议相比,MAC层吞吐量、数据传输成功率和信道利用率分别提升了12.82%、12.28%和8.73%,证明了所提协议的有效性。

动态多太比特核心光网络技术浅析

随着信息产业的大数据业务发展,传统的网络资源已经不能满足人们的要求,新一代网络体系必将发生变革并产生新一代网络(NGN),动态多太比特核心光网络(CORONET)计划是由美国提出来的新的一代网络计划,主要是寻求高度动态、多太比特核心光网络体系结构、协议、控制和管理的方案。利用波分复用(WDM)带宽资源和强大的波长路由能力,构造一个全球范围的核心光网络,即连接全球范围内主要站点的大容量、长距离基础设施。将IP over WDM的全光交换技术应用到CORONET网络系统中,采用的三次握手分布信号协议方法(3WHS)通过动态链接可以达到百毫秒级的快速建立时间并极大提高网络安全。最后,借鉴该网络计划的发展情况阐述对我们国家光网络发展所带来的启示。

太赫兹超高速无线网络路由协议研究综述

太赫兹波是一种位于毫米波和红外光波之间的电磁波;有较宽的未被分配的频带且可支持Gbps以上的无线数据传输速率;因此近年来太赫兹通信技术成为各国研究的热点。首先简介了太赫兹超高速无线网络;然后叙述太赫兹超高速无线网络的拓扑结构;接着着重描述了现有的太赫兹超高速无线网络路由协议,并对协议进行分析介绍。

四川省通信行业圆满完成党的十九大网络与信息安全保障工作

10月18—24日，中国其产党第十九次全国代表大会在北京胜利召开。在工业和信息化部、四川省委省政府的坚强领导和统一部署下，四川省通信行业以高度的政治责任感和使命感，充分发扬吃苦耐劳、勇于拼搏、连续奋战的优良作风，圆满完成了党的十九大网络与信息安全保障任务。

盛大网络与阶梯数码结成战略合作伙伴关系

3月27日盛大网络与阶梯数码科技有限公司．宣布结成战略合作伙伴关系。双方将面向广大的中国家庭用户需求，以数字内容为核心，联合推广集娱乐．求知和生活功能于一身的新一代数字家庭娱乐中心。

2005中国互联网大会将由两岸三地合作举办

互联网新一轮发展机遇期来临之际，两岸三地互联网人首度合作举办2005(第四届)中国互联网大会(www．internetdigital．org)。亚太网络精英即将汇聚在此，携手把握商业、技术、应用创新浪潮带来的新商机。2005中国互联网大会有以下六个特点：

PREPARATION AND PROPERTIES OF GEL POLYMER ELECTROLYTE BASED ON PVDF/ACRYLATE INTERPENETRATING POLYMER NETWORK FOR DYE-SENSITIZED SOLAR CELL

The gel polymer electrolytes（GPEs）based on poly（vinylidence fluoride）（PVDF）/acrylate interpenetrating polymer network（IPN）are prepared.The micro-phase separation type GPEs are characterized by Fourier transform infrared（FTIR）spectroscopy,scanning electron microscope（SEM）,respectively.Moreover,the conductivity and the voltage-current curves of the electrolytes are measured by electrochemical workstation.The higher porosity and electrolyte uptake are observed in the membranes prepared at lower crosslinker concentration.The suitable cross-linking acrylate monomer improves the porosity and the electrochemical behavior of GPE.A dye-sensitized solar cell（DSSC）employing PGE based on PVDF/poly（ethylene glycol dimethacrylate）（PEGDMA）IPN yields an open-circuit voltage of 0.674 V,short-circuit current of 8.476 mA·cm-2and the conversion efficiency of 2.710% under 100 mW·cm-2illumination.

热烈庆祝“中国模标网”开通

中国的模具标准件市场广阔，但举步艰难，行业标准参差不齐，发展更是良莠不齐，如何规范行业是一个很大的话题，为此，由昆太网络承接构建的中国模标网的产生，给解决这个问题提供了一个互动的平台。也给了模标行业一个交流的天地，通过这个网站，行业企业可以在逐渐的交流中达到共识的目的，为现有的行业标准做出更好的参与交流，最终形成一个规范的国内行业标准，各企业之问可以通过这个网站达到相互认识、交流的日的。

“中国模标网”开通

中国的模具标准件虽然市场广阔，但却发展缓慢，这是因为模具行业标准不统一所导致的后果，如何规范行业标准是当务之急，为此，由昆太网络承接构建的中国模标网的产生，为解决这个问题提供了一个良好的互动平台。也为模具标准件行业的信息快速交流提供了一片天地，通过这个网站，企业可以在逐渐增多的交流中达成共识。为现有行业标准的进一步完善提供切实可行的意见，最终形成一个规范的国内模具行业标准。

Modeling for Ethernet passive optical network receiver

A behavior model for the receiver of the Ethernet passive optical network（EPON） is presented. The model consists of a fiber, a photodetector, a transimpedance amplifier （TIA） followed by a limiting amplifier and a clock and data recovery＇ circuit （CDR）. Each sub-model is constructed based on the architecture of a circuit. The noise and jitter in each block such as shot noise, thermal noise, deterministic and random jitter are also considered. The performance of the whole receiver can be evaluated by the simulation of the behavior model, which is faster than the ordinary circuit model and more accurate than the analytical model. The whole model is implemented with C ＋＋ and simulated in Microsoft Visual C ＋＋ 6. 0. Using the Monte Carlo method, the EPON receiver is simulated. The simulation results show a good agreement with experimental ones.

Using CSMA/CD for Ethernet Passive Optical Network (EPON)

Using CSMA/CD for EPON can eliminate the augmentations, such as multi-point control protocol and point-to-point emulation, added to the existing 802.3 architecture due to the incompatibility of PON to Ethernet. Both full-duplex EPON system and half-duplex EPON system using CSMA/CD were proposed. In the full-duplex EPON, CSMA/CD is used as the upstream MAC protocol. In the half-duplex EPON system, both upstream and downstream traffic contend for the optical channel through CSMA/CD protocol. The upstream lightwave redirection and collision detection techniques were given. By the analysis and simulation, the throughput performance of the half-duplex EPON system is proven to be as well as that of the existing high speed half-duplex Ethernet LAN.

Relationship Between Changes of River-lake Networks and Water Levels in Typical Regions of Taihu Lake Basin,China

The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.

宽带光纤接入网的发展趋势

宽带光纤接入网的推进速度有多快,取决于多种因素,包括市场的需求、竞争的需要、应用的刺激、技术的进步,成本的下降和配套运维系统的开发等等。以下就从统技术的角度来分析几种主要的宽带光纤接入技术的特征、问题和发展趋势。

Beyond 100 Gb/s Optical OFDM Transmitted in Optical Long-Haul System

100 G Ethernet is considered to become the next generation Ethernet standard for IP networks.Typical 100 Gb/s transmission systems and their performance are presented.Comparision and analysis for 100 Gb/s transmission systems have been discussed.It is demonstrated that optical OFDM can be used in future 100 Gb/s/ch and long-haul system.

Research on Intelligent Transportation System and Its Key Technology based on IOT

This paper presents a design scheme of intelligent transportation system based on the Internet of things. First, the paper elaborated the related technical and functional demand of intelligent traffic system, designed the gateway level model and the overall project. Then, we design gateway hardware circuit according to the overall plan, and design the gateway application software according to the functional requirements. Through the experiment and simulation results show that, the intelligent transportation system gateway based on Internet of things is ability to create ZigBee network through the way of wireless access, GPRS network, Ethernet access based on the wired way, to realizes multimode access, multi-protocol conversion gateway, ad hoc network functions.