基于蚁群算法的无线多媒体传感器网络路由研究

通过对蚁群算法(ACO)的研究,设计了一种适合无线多媒体传感器网络的路由协议.该算法模拟自然界蚂蚁群体在寻找路径的方式,在节点发送数据包时,以该路径之前发送数据包的频率以及通过该路径的代价为参数,计算选择该节点为下一跳的转发概率.仿真结果表明,采用该算法时,节点的平均寿命要比采用传统的定向投递算法时的节点寿命高20%,数据包成功发送速度也远远高于传统算法.     

基于友好社区的容迟网络路由算法

在容迟网络(delay tolerant networks,DTNs)中,由于节点间端到端连接的不稳定性,传统路由算法不再适合容迟网络。文章根据节点访问社区的历史信息定义节点的友好社区,并提出了一种基于友好社区的路由算法(friend community-based routing algorithm,FCR)。在该算法中,源节点首先将数据包传递给自身的友好社区访问接入点(access point,AP),然后源节点的友好社区AP选择本社区中与目的节点友好社区AP接触次数最多的节点作为中继点。从而数据包被快速地传递到目的节点的友好社区,并最终由目的节点的友好社区AP将数据包传递到目的节点。仿真实验结果表明,与著名的Epidemic、Label和SGBR算法相比,该算法在保证接近Epidemic算法达到最大传递率的情况下,仍然可以明显地节约网络拷贝数。     

一种基于网络坐标的低成本WSN绿色位置路由

现有无线传感器网络的绿色位置路由在实际部署中通常存在两大问题:一是利用GPS来获得节点位置信息的成本较高;二是没有评估定位误差对路由性能和节能效果的影响。鉴于此,提出一种定位误差条件下的低成本绿色位置路由算法。其主要思路是:该算法采用分布式网络坐标算法获取节点间相对位置信息,以此节省成本;提出数据收集环机制以缩小邻居候选节点集来降低选择最优中继/转发节点时的能耗,并且采用自适应传输机制扩大节点无线收发范围以提高数据包投递率。仿真结果表明,该算法的定位误差明显低于MDS和MDS-MAP,而其路径能量消耗和数据包投递率较LED算法相比分别降低43%和提高55%左右。     

DTN中基于二分图的路由选择

由于DTN(delay tolerant networks)缺乏稳定的端到端传输路径,为了提高其路由协议的传输效率,减少网络延迟和开销,主要采用增加冗余数据包副本的办法.而传统的DTN路由协议往往无法有效地控制数据包副本的数量,最终导致路由性能下降.由于DTN网络中的节点具有社会属性这一特点,使得节点的移动具有一定的规律性和稳定性.首先分析了节点之间信息交换关系,证明DTN中存在二分图的性质.其次提出DTN网络中基于二分图的路由选择和具有时间因素的最优路由算法,最后给出了模拟仿真实验结果.     

最小能量节点不相交多路径的自组网路由算法

为减轻节点不相交多路径路由负载和解决路径间的耦合问题,提出了一种基于定向天线的最小能量节点不相交多路径自组网路由算法(RMENDMRDA).初始时该算法应用优化波宽选择算法确定定向天线的最小扇形覆盖区域,从而节省能量消耗,在选择累计能量最小的节点不相交多路径时采用链路可靠性选择算法,以满足链路的可靠性要求.分析及模拟结果表明,该算法路由负载更小、路由发现频率更低.与源传输能量选择路由算法和节点不相交多路径路由算法相比,RMENDMRDA的数据包投递率提高了18%,路由负载降低了24%,节省能量约8%.     

基于跨层设计与优化的无线传感网络数据传输算法

针对无线传感网络(wireless sensor networks,WSNs)的多对一通信,提出了路由和媒体接入协议(medium access control,MAC)的跨层设计与优化的数据传输算法,记为J-R-MAC(joint routing and medium access control),进而减少传输时延。JR-MAC算法引用新的周期结构,此周期结构允许k个节点在同一个周期内安排数据包传输;并给节点提供k次机会传输数据包。同时,J-R-MAC算法将网络内所有节点划分k个不相交集;进而减少节点的空闲监听时间。此外,J-R-MAC引用特殊序列作为地址,减少控制包尺寸;进而降低能耗。仿真数据表明,与同类的协议相比,提出的J-R-MAC算法有效地降低了端到端传输时延;并提高了数据包传递率。     

一种新的无线mesh网络编码算法

针对网络编码可以在很大程度上提高网络吞吐量,但会增加网络的复杂性这一问题,构造了一个特殊的无线mesh网络拓扑结构,提出一个新的编码算法。该算法通过构造一个虚拟源节点,利用在无线组播网络中,仅需对进入中继节点的链路进行编码,进入目标节点的链路,直接路由选择就能达到网络编码所能够达到的容量。从而允许与目的节点相连接的中继节点收到数据包后直接路由选择。与传统的基于机会的网络编码COPE算法相比,该算法有效地减少了原始数据包传输的次数,从而提高了以网络编码增益来衡量的网络吞吐量。仿真试验验证了该算法的有效性。     

一种新的无线mesh网络编码算法

针对网络编码可以在很大程度上提高网络吞吐量,但会增加网络的复杂性这一问题,构造了一个特殊的无线mesh网络拓扑结构,提出一个新的编码算法.该算法通过构造一个虚拟源节点,利用在无线组播网络中,仅需对进入中继节点的链路进行编码,进入目标节点的链路,直接路由选择就能达到网络编码所能够达到的容量.从而允许与目的节点相连接的中继节点收到数据包后直接路由选择.与传统的基于机会的网络编码COPE算法相比,该算法有效地减少了原始数据包传输的次数,从而提高了以网络编码增益来衡量的网络吞吐量.仿真试验验证了该算法的有效性.     

面向低功耗的片上网络虚通道分配算法

为了更加合理地分配片上网络中虚通道资源并降低系统总功耗,提出了一种基于功耗优化的虚通道分配算法.该算法通过建立2D mesh结构片上网络通信数学模型,来估算网络中数据包的平均传输延时.然后,以此为约束条件,采用模拟退火算法实现虚通道分配,并通过减少虚通道总数,达到功耗优化的目标.在热点通信流量下,根据优化分配算法和平均分配算法的结果进行仿真测试.通过改变节点数据包的注入率,测出传输延时和功耗,以验证优化分配算法的有效性.实验结果表明,使用该算法可在满足传输延时约束条件的同时,更加合理地分配虚通道,有效降低了网络功耗.相比于平均分配算法,该算法可降低功耗2.3%～14.9%.     

面向VANETs改进的GPSR路由算法

针对车载网络GPSR的路由空洞问题,分析了现有策略的不足。为此,提出改进的GPSR。在改进的GPSR中,当节点已达到局部优化,即贪婪算法无法传递数据包,就利用邻居节点竞争方式转发数据包,并基于邻居节点的权值,选取最优的下一跳节点。仿真结果表明,改进的GPSR在数据传输率、端到端传输时延、路由长度方面均有较好的性能。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that