面向分布式搜索引擎的索引库动态维护算法

分布式搜索引擎在实际运行中存在大量的用户,同时索引更新频繁,而索引更新过程的复杂度使得用户的检索请求响应出现较大的延迟。本文提出一种基于内存映射表的索引库动态维护算法,按照一定时间粒度组织索引库,在内存中维护一个当前可用的子索引库列表,实现索引的透明更新。实验表明,该算法能够保证及时地对新数据建立索引,同时有效降低用户检索请求的响应时间。     

基于同态哈希函数和虚拟索引的动态云审计方案

为更好地实现云存储的数据完整性验证，解决云数据安全更新效率低的问题，提出一种基于同态哈希函数和虚拟索引的动态审计方案。首先对上传云服务器的数据进行盲化，以保护原始数据在云中的隐私；接着利用同态哈希算法对盲化后的数据进行签名，以便签名聚合的计算；然后利用虚拟索引实现对特定数据块快速查找和更新的同时，不对其他数据造成影响；最后，将提出的动态云审计方案扩展为批量验证方案，从而提高多用户场景下完整性验证的效率。理论分析表明，该方案是安全高效的。     

一种JPEG2000算术编码器的优化算法与实现

通过对索引表和概率间隔区间更新条件的分析,提出了一种JPEG2000算术编码器的部分并行优化算法.在连续编码两个数据对时,通过预测间隔区间的变化,可以一次完成索引表和间隔区间的更新,从而减小了编码数据的关联性,实现了算术编码器的部分并行编码.设计了基于3级流水线的JPEG2000算术编码器,并通过了FPGA验证.试验结果表明,该算法平均每个时钟编码1.58对数据,比每个时钟编码1对数据的普通算法,编码效率提高了58%.     

一种信息审计系统中的多关键字匹配算法

针对审计系统中搜索大量审计数据的需要,设计了一种基于哈希表机制的多关键字匹配算法.该算法把关键字集合储存到哈希表中,并为关键字集合建立了两个过滤表和一个关键字长度类型表.在查找过程中,对未经过滤表验证的字符串不再进行匹配查找,同时,关键字长度类型表的使用减少了循环的次数.测试结果表明,该算法在速度和精度上都优于BM和mgrep算法.     

GBLHT: a GPU-Accelerated Linear Hash Table with Batch Insertion

为改善线性哈希表这一有效索引结构的插入性能,在分析现有方法的基础上,结合CUDA并行编程模型,设计并实现了一种基于GPU的批量插入线性哈希表GBLHT;借助原子函数atomicAdd,GBLHT可以充分利用GPU强大的并行吞吐量来实现大规模记录的无锁批量插入；通过实验对比传统串行插入方法、CPU批量插入方法以及GBLHT的插入性能,发现在不同参数设置条件下,GBLHT的插入性能比传统串行方式提升了7～14倍,与4线程的CPU批量插入方法相比则提升了3～6倍.     

基于三维分档布鲁姆过滤器的Top-k查询算法

针对NRA算法和BPA算法查询效率不高、重复访问数据的问题,提出了一种基于三维分档布鲁姆过滤器表(TF)的Top-k查询算法(TKBFP).该算法使用TF对数据进行处理,以较低的误判率获得较高的访问效率并降低了内存消耗,利用最优位置索引策略,避免重复访问数据对象.对TKBFP算法进行了严格的语义定义,推导出每一维BF中需要的哈希函数个数;以自主开发的Java程序为仿真平台,对TKBFP算法进行了试验,并对算法执行效率和存储性能进行评价.试验结果表明,该算法能够避免重复访问数据对象,并能以较低的误判率实现大规模数据的高效查询处理.与NRA和BPA相比,当属性列表超过4个时,开销明显降低,适合面向大规模数据的查询处理应用.     

基于声母和深度哈希的密文语音全文检索方法

为了实现基于内容的语音全文检索,提高语音检索性能,以及保障云端语音数据的隐私安全,提出了一种基于声母和深度哈希的密文语音全文检索方法.该方法将提出的基于汉语声母和元音的双向循环递归神经网络(RNN)-长短时记忆(LSTM)深度学习模型与语音感知哈希相结合,分别将加密语音和生成的哈希码上传至云端密文语音库和全文哈希索引表,并建立一一映射关系.查询时提取待查询语音的哈希码,并与云端的全文哈希索引表进行阶段式匹配检索.实验结果表明:该方法既能保障语音隐私安全,又能获得较高的检索精确度与可观的召回率(当精确度为97.68％时召回率可达47.60％),并在一定程度上减弱了说话人声音特征对全文检索的不利影响.     

XML文档结构索引的更新维护

xml作为一种数据表示方式,越来越为人们所接受.最近,基于xml/半结构化数据的索引的查询引起了人们的广泛关注.有人提出来用结构索引来支持基于xml/半结构化数据的查询.由于xml/半结构化数据的结构不严格、不规则,结构索引会随着数据的增加或删除而变化,维护结构索引就成了首要问题.本文研究了在xml文档集合上增加多个文档和删除一个文档时结构索引的更新,提出了在这两种情况下的索引维护算法,这两种算法比现在已知的其它算法的性能要更优秀.     

基于动态获取高频率键的MapReduce性能优化算法

在云计算技术领域中,MapReduce能够帮助人们快速处理海量数据,因此在学术界以及工业界越来越受到重视。但是MapReduce在处理以文本为中心的应用时,中间结果中数据重复较多。针对该情况,已有的高频率缓冲(frequency buffering,FB)算法提出在环形内存缓冲之前添加哈希表,并将高频率键存储在哈希表中。该算法通过采样来实现,有额外开销并且统计出的高频率键并不一定准确。该文提出一种基于动态获取高频率键的MapReduce性能优化算法,通过在环形内存缓冲之前增加计数Bloom过滤器(counting Bloom filter,CBF)和哈希表,将高频率键动态地存储在哈希表中。该算法获得的高频率键更准确,同时大大减少了数据排序和磁盘I/O的开销。实际测试结果表明:该算法明显提高了作业的执行速度,比原始MapReduce提高17.04%,比FB算法提高9.31%。     

图形处理器上CSB~+-树索引的并行构建算法

为提高缓存敏感CSB+-树索引的操作效率,在图形处理器(GPU)上研究CSB+-树的并行构建和查询性能.通过分析索引树内部节点的每一键与对应叶子节点的映射关系,提出了一种一次性并行构建CSB+-树所有内部节点键值的无锁并行算法,以最大并行度来快速构建索引树.该算法通过设计GPU平台上支持CSB+-树的索引数据任意伸缩的动态数组来解决GPU上不能动态分配显存空间的问题,通过在索引内部节点的边界增加填充位来减少线程块的线程分支数,从而提高CSB+-树的查询效率.实验结果表明,文中所提算法的运行时间比基于单个节点和基于树层的并行算法分别提高了31.0和1.4倍.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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