基于正则表达式的日志解析系统构建研究

针对日志格式异构造成的日志解析局限性问题,文章介绍了一种基于正则表达式日志数据分组提取的方法,采用日志格式描述与日志内容解析相分离的策略,使用XML语言编写日志格式描述和日志数据项说明的脚本文档,该脚本文档与日志类别相对应,与具体的解析程序分离,提高了日志解析系统的灵活性和扩展性。     

一种基于查询事件的域名服务器日志模型

提出了一种基于查询事件的日志模型,采用查询/应答日志匹配的方法完整的记录了一次查询事件,利用内存数据结构提高了海量数据写入的I/O效率;在日志分析过程中对日志文件建立二维哈希索引,利用布隆过滤器减少磁盘I/O次数,提高了分析效率.     

正则表达式在填空题答案设计及评分中的应用

在设计填空题答案的过程中,存在着试题答案不完整的问题,这会影响到考试的信度.正则表达式是一种描述字符串结构模式的形式化表达方法,在字符串处理上有着强大的功能.利用正则表达式,可以判断一个字符序列(答题结果)是否与一个模式(试题答案)相匹配.在填空题试题答案设计和计算机自动评分过程中,运用正则表达式实现填空题的计算机自动评分,取得了理想的结果.     

基于数据仓库审计信息安全的方法

采用Syslog标准协议及基于正则表达式的模式匹配方法实时收集日志信息,借助于数据仓库采用信息安全多维模型的建模方法,对各个审计分析主题通过共同的分析维进行关联;通过数据仓库中的多维模型,采用联机在线分析处理方法、数据挖掘方法进行多维分析、挖掘,发现网络中潜在的安全漏洞和问题,根据分析结果生成审计分析报表,进而提高审计系统的扩展性、开放性以及审计分析的效率。     

Oracle数据库重做日志文件的分析及其应用

日志是数据库管理系统中必不可少的一个组成部分，保存着数据库的操作历史数据。因此对数据库的恢复有着很重要的作用。通过对Oracle日志文件的研究，以及对其转储文件的分析，讨论了基于日志转储文件的数据库数据恢复方法。     

正则表达式在Oracle中的应用与实现

首先介绍Oracle 10g中增加的新功能及正则表达式的发展,给出了正则表达式的定义以及其用途,分析了Oracle中各个字符元的含义,并结合具体的查询实例详细说明了正则表达式在Oracle中的应用。     

LSM树中基于热度预测的异构布隆过滤器方案

日志结构合并(Log-Structured-Merge,LSM)树中常使用布隆过滤器减少无效磁盘I/O.但是用户无法无限制地细化布隆过滤器的粒度,原因是在一些数据量庞大而数据项较小的工作流中,这些元数据需要占用大量存储空间.其次在一些内存受限的环境下,内存缓冲区无法容纳更多的过滤器数据,造成缓冲区与磁盘的频繁数据交换.针对上述问题本文提出LSM树中的异构布隆过滤器方案,在LSM树的每一层维护热度预测模型,新生成的SSTable通过预测的热度来分配不同粒度的布隆过滤器,然后使用特定缓存管理方案来维护缓存中的过滤器数据并处理工作流热度发生改变的情况.实验证明,本文的方案在保持相同外存占用与内存消耗的情况下,读取吞吐量比采用原始LSM树结构的LevelDB提升22％～53％.     

基于hadoop的大规模查询日志分析模型设计

日志分析对于在用户搜索领域有着很重要的意义,目前的日志分析系统有着不少弊端,比如：海量数据无法处理、离线处理模式、处理时延长等。对日志数据采用分级归档,可以实现大数据的分级优化处理。本文通过提出在一种基于Hadoop的大数据日志分析模型,并对其业务处理流程以及功能架构进行深入分析,实验结果反映出该系统扩展性强、海量数据处理能力卓越、满足在线处理等,具有良好的可行性和有效性。     

Web日志挖掘中预处理过程的具体研究

Web日志的数据预处理是Web日志挖掘过程中基础而关键的一步,对之后的模式识别和模式分析有着很大的影响。为了达到有效处理数据的目的,针对此预处理过程中的5个步骤逐一进行分析,并在事务识别这一步骤中,比较了常用的两种算法。最后,基于这些算法思想,在Windows平台下,采用Java语言实现了Web日志预处理。实验结果表明是有效的。     

OpenFlow网络测量分析系统的设计实现

OpenFlow网络目前缺少支持定量测量分析各种创新应用或机制的有效手段。以升级OpenFlow网络设备为具有本地日志功能的OpenFlow测量实体为基础,设计了一种基于集中式服务器控制测量实体进行分布式测量的机制,制定了其间的通信规程OpenFlow测量控制协议(OMCP),同时基于正则表达式、散列技术和可扩展的统计函数库等方式设计了一种分析测量日志的功能。原型系统的实验表明,OpenTrace服务器能够灵活部署和控制分布式测量任务,OpenTrace系统不仅能够定量地重现数据平面的数据流传输过程而且能够重现控制平面的控制事件交互过程,从而可为量化分析OpenFlow网络应用和新型机制提供广泛的性能数据。     

具有宽调谐范围的低电压对数域二阶低通滤波器

提出了一个由BiCMOS构成的对数域二阶低通滤波器,并采用跨导线性原理分析得到其传递函数。分析了晶体管的寄生电容对此滤波器频率特性的影响。PSpice仿真结果表明,该对数域低通二阶节的实际频率特性和理想特性基本一致。且具有宽频率调谐范围、低工作电压和低失真等特点,可用于对数域高阶滤波器的设计。     

The impact of distortions of phase-shift keyed signals with gradual phase change in the receiver input circuits on the signal detection characteristics during the signal reception against the background of noise

This study examines the impact of an input band-pass filter on the reception of phase-shift keyed signals (PSKS) with gradual phase change against the background of noises. In the case under investigation PSKS are received by a correlation receiver during the radar detection of targets. Analytical expressions of the target detection characteristics were obtained for PSKS with random initial phase and the amplitude containing regular and fluctuating components. This study also examines the relationships of the detection characteristics as a function of the input filter band-pass and the interval duration of gradual phase change.     

Log filtering using gyrators

A general realisation for gyrators applicable to log filters, and ESS filters in general, is proposed. An implementation based on the `E-cells' is given. Its large signal behaviour is shown to be linear by embedding the proposed topology into a first order log filter circuit used to produce a first order highpass filter function in an equivalent way to an R-L filter     

基于雷米兹交换算法设计线性相位对数FIR滤波器

根据线性相位对数FIR滤波器幅度响应与线性相位FIR滤波器幅度响应的关系 ,将线性相位对数滤波器设计转换为线性相位FIR滤波器设计。该方法直接采用雷米兹交换算法即可获得线性相位对数滤波器通带和阻带的等纹波特性。另外 ,该方法既可基于频域均匀采样也可基于频域非均匀采样 ,具有一定的通用性和灵活性     

Analytical design of 3-D wavelet filter banks using themultivariate Bernstein polynomial

The design of 3-D multirate filter banks where the downsampling/upsampling is on the FCO (face centred orthorhombic) lattice is addressed. With such a sampling lattice, the ideal 3-D sub-band of the low-pass filter is of the TRO (truncated octahedron) shape. The transformation of variables has been shown previously to be an effective technique for designing M-D (multidimensional) filter banks. A design technique is presented for the transformation function using the multivariate Bernstein polynomial which provides a good approximation to the TRO sub-band shape. The method is analytically based and does not require any optimisation procedure. Closed form expressions are obtained for the filters of any order. Another advantage of this technique is that it yields filters with a flat frequency response at the aliasing frequency (ω₁, ω₂ , ω₃)=(π, π, π). This flatness is important for giving regular discrete wavelet transform systems     

Log-domain filtering by simulating the topology of passive prototypes

A systematic method for designing log-domain filter structures that simulate the topology of the corresponding passive prototypes is introduced in this paper. This has been achieved by transposing the i-/spl upsi/ characteristic equation of each passive element in the linear domain, to the corresponding one in the log domain. The transposition has been done in such a way that, the current that flows through the terminals of the passive element in the linear domain sustains its value in the corresponding log-domain configuration. In this way the linear operation of the whole filter is preserved. With regard to the voltage at each terminal of the passive prototype, this is logarithmically compressed in order to achieve filtering in the log domain. Following the above considerations, the log-domain equivalents of all passive elements of the prototype filter were derived. Having established the equivalents, the procedure for designing high-order log-domain filters is quite facilitated. The validity of the proposed technique is demonstrated through simulation results for a fifth-order elliptic low-pass filter.     

Log domain filtering for RF applications

A new second-order log filter topology, which is particularly useful for RF signal processing, is introduced with a discussion of how its features meet the needs of RF design. The design concept behind log filters is reviewed. Simulation and experimental results on a test IC are presented for an electronically tunable filter which operates beyond 400 MHz, with Q's in excess of 60, using the AT&T CBIC-V2 process     

一种基于平衡式对数域积分器的高阶滤波器

提出了一个新的工作在甲乙类状态的平衡式对数域积分器 ,用跨导线性原理分析得到其传递函数。基于该积分器电路 ,采用无源网络模拟法设计出一个 1 d B波纹的五阶切比雪夫对数域低通滤波器。PSpice仿真结果表明 ,这种新型对数域滤波器能在低电压条件下工作 ,并具有高频、宽调谐范围和低失真等特点。     

On Crossbar Switching Networks

For networks that exhibit neither concentration nor expansion, the well-known probabilistic model of C. Y. Lee is refined so as to take account of the dependence of events in different stages. For series-parallel networks, the refined model yields exact expressions for the point-to-point blocking probability. These expressions bear the same relationship to the refined model as the KittredgeMolina expressions do to Lee's model. Comparison between the two sets of expressions shows that Lee's model tends to overestimate the blocking probability. Asymptotic analysis of the new expressions leads to improved upper bounds on the cost: it is shown that a network that carriesNerlangs with a blocking probability at mostepsilon > 0can be built with6N log_{2} N + O(N log log 1/epsilon)contacts.     

系统安全中Linux日志的实用研究

日志对于系统安全极为重要。日志是系统运行的历史记录，通过它可以方便地查找由系统错误或受到的入侵，在Linux系统安全的实际应用中，首先要对日志配置文件进行合理设置，并建立起日志服务器．确保日志文件的安全。在可靠的日志基础上，使用Swatch等日志工具过滤出有用的日志信息，并及时进行处理分析．加强对系统的安全保护。