改进的基于动态帧时隙ALOHA防碰撞算法

在RFID系统中,存在阅读器与多个标签同时通信的碰撞问题,标签防碰撞技术是解决标签防碰撞问题和提高标签识别率的关键。在分析动态帧时隙ALOHA算法的基础之上,提出了一种改进的基于随机数重新分组的动态帧时隙ALOHA算法。该算法证明了当引入一个随机数的时候,系统的吞吐率是最大的,并且同时利用标签唯一的ID号中的第一位的取值不同,进行重新分组,从而减少了标签碰撞的次数。仿真实验结果表明,所提出的改进算法执行效率更高,碰撞次数更少,识别成功所需的时隙数更少,有效地提高了标签的识别速度。     

一种基于等区域划分的RFID防碰撞算法

针对现有算法识别效率较低的问题, 提出一种基于等区域划分的射频识别（RFID）防碰撞算法. 通过对阅读器识别范围内的标签进行均等区域划分建立一种新型的分组结构, 并在每组中分别使用动态预测权值估计标签数目, 将其与最优时隙数调整方案相结合对标签进行识别, 解决了大规模标签应用场景中由于标签增多导致的系统稳定性差和吞吐率低的问题. 仿真结果表明, 该算法能有效提高系统吞吐率, 并减少通信过程中的时隙数.     

一种基于等区域划分的RFID防碰撞算法

针对现有算法识别效率较低的问题, 提出一种基于等区域划分的射频识别（RFID）防碰撞算法. 通过对阅读器识别范围内的标签进行均等区域划分建立一种新型的分组结构, 并在每组中分别使用动态预测权值估计标签数目, 将其与最优时隙数调整方案相结合对标签进行识别, 解决了大规模标签应用场景中由于标签增多导致的系统稳定性差和吞吐率低的问题. 仿真结果表明, 该算法能有效提高系统吞吐率, 并减少通信过程中的时隙数.     

改进的二进制查询树的RFID标签防碰撞算法

在射频识别系统中,存在阅读器与多个标签同时通信的碰撞问题,标签的防碰撞算法是解决数据冲突的关键。文章详细阐述了已有的典型的二进制查询树的防碰撞算法,并在此基础上提出了一种新的防碰撞算法;该算法利用二时隙的方法,使阅读器的询问次数和标签识别所需的数据流大大减少,提高了标签的识别效率。从仿真实验中表明,该算法比已有的二进制查询树算法具有更明显的优势。     

基于贝叶斯估计的RFID帧时隙ALOHA算法

在RFID系统中帧时隙ALOHA算法的基础上,提出了一种基于贝叶斯估计的动态帧时隙ALOHA算法,与传统的算法相比,它不仅能够充分利用阅读器在当前帧收集的信息,而且将先前帧的信息保留作为当前帧的先验信息;再根据贝叶斯理论对标签个数进行估计并动态调整帧长.该算法能够更精确稳定地估计标签的个数,提高系统的吞吐率,加快标签识别速度.     

动态帧时隙算法的研究与改进

为了进一步提高防碰撞算法的性能,对随机标签防碰撞算法进行了研究,分析了随机标签防碰撞算法的优点与缺点.其中,动态帧时隙算法(DFSA)存在随着标签数目的增多,所需要的时隙数目急剧增加的缺点,针对这一问题,提出了一种动态帧时隙算法的分集改进方法.仿真结果表明,改进方案减少了系统识别标签所需要的时隙数量,提高了算法性能.     

基于动态时隙ALOHA的多标签识别防碰撞算法

对于RFID系统中多标签识别过程中的标签信息碰撞问题,分析了动态时隙ALOHA算法中的不足,提出了改进算法.改进算法通过优化冲突时隙数的变化,使得在每个标签识别周期内通信吞吐率最大,从而减小RF场内所有标签识别时间,并通过调整ACK确认命令的发送格式,在下一个单次识别周期中,集体确认已识别标签,这使得标签识别与确认分离,增加了无源标签吸收的能量,提高了通信的可靠性.仿真实验表明,改进算法在减少碰撞率方面具有良好的性能.     

基于标签信息分组的射频识别防碰撞算法

射频识别系统在读取标签时,会因碰撞问题而严重影响识别率,导致系统工作效率降低.为此,文中提出一种基于标签信息分组的射频识别防碰撞算法.该算法根据标签信息将标签划分成若干组,按分组顺序依次识别,通过减少同时响应阅读器命令的标签数量来达到降低标签碰撞概率的目的.文中还对算法中的分组效率和时隙选择问题进行了分析、证明和仿真....     

捕获效应下的标签估计算法

传统的标签估计通常要统计标签和阅读器通信中的碰撞时隙和单标签时隙的个数.然而在实际通信过程中,由于捕获效应的存在,较强信号通常会抑制掉较弱信号.这就造成了实际统计情况与事实不符的现象,进而影响标签的正确估计.由于空时隙中没有标签响应,采用统计空时隙数进行标签估计不受捕获效应影响.仿真结果表明,统计空时隙的标签估计算法在捕获效应情况下,估计精度没有变化,同时对帧时隙大小不敏感,优于其他基于统计单标签时隙数和碰撞时隙数来进行标签估计的算法.     

血液管理RFID多标签识别碰撞避免方法

EPCglobal_Class1Gen2协议标准中的动态帧时隙ALOHA标签防碰撞Q算法没有完全消除空时隙,浪费了时序资源,在血液管理这种实时性要求高、标签数量大的情况下是不能接受的。该文提出一种多标签识别碰撞避免方法,将标签识别过程分为两次时隙预分配和标签识别2个阶段,消除了Class1Gen2协议的空时隙以提高时间利用率。对血液管理应用场景进行了数值仿真分析,结果表明该方法能够显著提高标签识别效率。     

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.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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