3G无线网络中自适应QoS的多媒体传输

探讨自适应QoS支持的多媒体(如视频、音频、电子邮件和web流量)在3G无线信道传输时资源的分配。对不同类型媒体．结合链路层和应用层的自适应QoS．给出一种端到端的结构。估计变化的信道并进行动态分配资源。     

MPEG-4视频无线传输的自适应QoS控制

自适应QoS控制机制由优化模式选择和固定时延的混合自动请求重传组成，优化模式选择在压缩 层提供QoS支持，固定时延的混合自动请求重传在链路层提供QoS支持。仿真结果显示给出的自适应QoS 控制对MPEG-4视频在动态的无线信道上传输达到了满意的质量，并有效地利用了网络资源。     

一种基于QoS的星座通信系统跨层资源分配算法

针对目前星座通信系统星地链路资源分配不灵活、缺乏有效服务质量(QoS)保障机制等问题,提出一种基于QoS的星座通信系统跨层资源分配算法.利用自适应编码调制(ACM)技术,通过定义用户信道质量评估算法、可调公平性调度算法、业务QoS分类调度算法及用户业务分配权重函数,为终端用户指定工作频率、时隙、编码方式、调制方式等物理层工作参数,实现根据业务QoS保障要求灵活分配物理层信道资源,达到提高系统资源利用率与满足业务QoS保障需求的平衡.仿真实例验证该算法可以实现星座通信系统根据业务QoS和用户信道质量对星地链路资源的合理分配和调度.     

MPEG—4视频无线传输的自适应QoS控制

自适应QoS控制机制由优化模式选择和固定时延的混合自动请求重传组成，优化模式选择在压缩层提供QoS支持，固定时延的混合自动请求重传在链路层提供QoS支持。仿真结果显示给出的自适应QoS控制对MPEG—4视频在动态的无线信道上传输达到了满意的质量，并有效地利用了网络资源。     

一种基于天线选择的比特功率分配算法

链路自适应技术根据信道环境的变化自适应地调整发射功率、调制方式等,以最大化地利用无线信道资源．为了适应3G对可变数据速率和灵活QoS的要求,结合天线选择技术、比特分配和功率分配技术的优点给出一种基于天线选择的比特和功率分配算法,基于天线选择的比特和功率分配算法在BER受限的情况下最大化数据传输速率．仿真结果表明,该算法比原算法能有效地提高数据传输速率．     

用于移动多媒体通信的双重自适应Turbo编码调制技术

给出了一种应用于移动多媒体通信的跨层的双重自适应编码调制技术.该技术采用Turbo码,并同时自适应于时变的信道特征和不同媒体业务的服务质量(QoS),以充分提高系统的平均吞吐量.首先给出经优化设计的实用信道自适应Turbo编码调制方案,该方案距Shannon极限仅2.5 dB;然后将一个QoS自适应方案加载其上,构成跨层的双重自适应结构.仿真结果表明,在假设所有媒体业务以等概率出现、业务持续时间服从指数分布时,该新颖的双重自适应技术可达到距衰落信道容量2 dB的优异性能.     

无线局域网中一种提供服务质量的自适应算法

IEEE802.11e在信道负载增加和信道性能恶化的情况下为优先级流提供QoS时,系统性能存在不稳定性.针对该问题提出一种新的自适应MAC算法(MEDCF),站点根据网络中的负载情况和信道的误码率自动调整竞争窗口大小、退避时间及数据帧长度.使信道在不同的负载和变化的信道特性下都能够在稳定系统吞吐量的同时,保证不同优先级数据流对QoS的需求.仿真结果验证了算法的有效性.     

跨层自适应无线资源分配方案

提出了一种新的跨层自适应资源分配方案,该方案不仅考虑了业务数据到达的随机特性、数据缓存队列状态、业务时延等MAC层的QoS要求,还考虑了无线信道的时变特性和功率限制,并通过自适应技术实现了系统性能的优化.仿真结果显示,该方案提高了系统频谱效率、功率效率和系统容量,可以满足多用户实时业务的QoS要求,是一种适用于时变选择性衰落信道的资源分配方案.     

基于QoS保证的自适应跨层调度算法

针对无线多媒体通信网络,提出一种基于业务和信道信息的自适应跨层调度算法(TCAS).引入调度概率作为决策因子,利用业务流量和信道状态等跨层信息,设计出基于决策因子的预分配和实时调度相结合的资源分配方法.仿真结果表明,该算法与比例公平调度(PFS)算法和基于信道和队列信息的调度策略(CASTI)算法等经典算法相比,在无线多媒体应用环境中具有更强的适应性和稳定性,可提供多样服务质量(QoS)保证,并显著提高了资源利用率.     

带有时间约束的机载自组网自适应退避算法

针对传统媒质接入控制(MAC)层退避算法无法满足机载自组网中高优先级业务高可靠、低时延的QoS传输需求,以及重负载时算法性能下降严重的问题,提出一种带有时间约束的多优先级自适应退避算法。首先,针对不同优先级业务的QoS需求,建立相应的时间约束机制和竞争窗口自适应调整机制,当网络处于重负载时,通过限制低优先级业务接入信道来保证高优先级业务的传输;其次采用三维马尔科夫链对多优先级自适应退避算法进行建模,求解不同网络负载时各优先级分组受时间约束条件下的退避状态转移概率,理论推导出网络吞吐量和平均MAC时延的数学表达式。仿真结果表明,该算法在重负载时能够有效保障高优先级业务低时延(2ms)、高可靠(99%)的QoS需求,相比增强型分布式信道接入访问和区分企业优先级的自适应退避算法,当网络负载大于9 000包/s时,吞吐量分别提升了33.4%和21.5%。     

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