Weighted symbol-flipping decoding algorithm for nonbinary LDPC codes with flipping patterns

A novel low-complexity weighted symbol-flipping algorithm with flipping patterns to decode nonbinary low-density parity-check codes is proposed. The proposed decoding procedure updates the hard-decision received symbol vector iteratively in search of a valid codeword in the symbol vector space. Only one symbol is flipped in each iteration, and symbol flipping function, which is employed as the symbol flipping metric, combines the number of failed checks and the reliabilities of the received bits and calculated symbols. A scheme to avoid infinite loops and select one symbol to flip in high order Galois field search is also proposed. The design of flipping pattern＇s order and depth, which is dependent of the computational requirement and error performance, is also proposed and exemplified. Simulation results show that the algorithm achieves an appealing tradeoff between performance and computational requirement over relatively low Galois field for short to medium code length.

The Symbolic Significance of Holy Grail in The Da Vinci Code

Dan Brown's best-seller, The Da Vinci Code is a classical union of thriller and intelligence, and he has a good command of the knowledge on cryptology, mathematics, religion, culture and art. In addition, he organized his work fully with a large amount of information the public concerned and well-arranged them into the wonderful story.The protagonists of the book, Robert Langdon, the symbologist from Harvard and Sophie Neveu, the decode expert (The curator's granddaughter) have to solve the complicated secret by gradually investigating the strange codes and meet a series of dangerous situations. They find that what they're looking for may be a shocking secret while they solve the codes progressively during the fierce struggle with the mystery manipulator. The secret is the Holy Grail, which the Church tends to hide forever because it will destroy the faith.Therefore, this thesis will analyze the symbolic significance of Holy Grail in the book and the arguments on it against the author's viewpoint by observing related religious figures, religious phenomenon and religious organizations.

一类新的MDS symbol-pair码

为了对抗符号对(symbol-pair)读取信道中的符号对错误,符号对码应运而生。与经典纠错码类似,极小对距离越大,符号对码的纠错能力越强,因此,构造具有较大极小符号对距离的符号对码至关重要。根据多项式重根的判别方法,通过分析有限域F p上线性方程组的解,得到了一类最大距离可分的符号对(MDS symbol-pair)码,其长度为4 p,极小符号对距离为10。结果表明,在同样码长的情况下,新构造的MDS符号对码具有较大的极小符号对距离。

Joint channel estimation and symbol detection for space-time block code

The simplified joint channel estimation and symbol detection based on the EM (expectation-maximization) algorithm for space-time block code (STBC) are proposed. By assuming channel to be invariant within only one STBC word and utilizing the orthogonal structure of STBC, the computational complexity and cost of this algorithm are both very low, so it is very suitable to implementation in real systems.

基于符号执行优化的PDF恶意指标提取技术

恶意PDF文档是APT组织常用的攻击方法,提取分析其内嵌JavaScript代码指标是判定文档恶意性的重要手段,然而攻击者可以采取高度混淆、虚拟机与沙箱检测等逃逸方法。因此,文中创新性地将符号执行方法用于PDF指标提取,提出了一种基于符号执行优化的PDF恶意指标提取技术,并实现了由代码解析、符号执行和指标提取3个模块组成的指标提取系统SYMBPDF。在代码解析模块中实现内嵌JavaScript代码提取与重组。在符号执行模块中设计代码改写方法,通过强制分支转移提高符号执行的代码覆盖率;设计并发策略和两种约束求解优化方法,以提高系统执行效率。在指标提取模块中实现恶意指标整合与记录。对1 271个恶意样本进行了指标提取与评估,指标提取成功率为92.2%,有效性为91.7%,代码覆盖率较优化前提升8.5%,系统性能较优化前提升32.3%。

基于Q-Coder算术编码器的IP核设计

设计了一种实现算术编码的集成电路IP核,可用于下一代静止图像压缩标准JPEG2000编码系统中。采取易于硬件实现的二进制算术编码算法,分析了该IP核的各个模块和时序,在ModelSim软件中进行了功能仿真,在QuartusⅡ软件中完成了综合以及布局布线,并在自行设计的一块FPGA的PCI开发板上进行了验证和性能分析。实验结果表明,对相同的图像进行编码,该IP核的处理时间仅为软件处理时间的41%。该文的研究对于JPEG2000在实际中的应用有着重要的意义。

基于ARcode的移动增强现实系统研究

为解决移动设备多用户、大数据量目标的识别和跟踪问题,提出一种基于改进二维码的新型移动增强现实系统。通过C/S框架保证模型的更新,在客户端分离出识别和渲染过程,分析基于快速响应矩阵码的跟踪注册方法,针对其存在的跟踪范围小、跟踪不稳定的问题给出解决方案,从而完善系统。实验结果表明,与基于常规标志点和利用自然特征的方法相比,该系统方便实用、便于推广,且条码容易被手机使用,能识别出更多的信息。

2*2MIMO系统模型搭建及误码率分析

针对普通单天线收发系统无法满足现有互联网通信容量日益增大的问题,提出了一种多天线技术MIMO(Multiple Input Multiple Output)。首先搭建了2*2MIMO通信系统,其中发送端包括QPSK映射模块和Alamouti编码模块,信道为瑞利衰落信道,接收端包括最大比合并模块;然后对所设计的系统用Matlab软件进行了仿真;最后通过仿真对2*2MIMO系统的误码率性能进行了分析。仿真结果表明,2*2MIMO系统比2*1MIMO系统在相同信噪比的情况下误符号率性能更好,证实了2*2MIMO系统可增大信道的容量并提高系统的可靠性。

Code Component Reuse Supporting Environment (CCRSE) and Its Design Strategy

Code Component Reuse Supporting Environment (CCRSE), which has been developed by us, is an integrated development environment. CCRSE can provide comprehensive supports for the whole process of reusing code component in the manner of dynamic composition. The architecture and functionality of CCRSE are introduced. The key achievement is giving the three strategies that are vital to successfully design CCRSE. The three strategies include: (1) according to the three pivotal technologies (encapsulation, composition and management) for supporting composition reuse of code component, design three tools respectively. (2) keep tool for supporting code component development independent of tool for supporting code component composition. (3) strictly restrict code component specification, provide the strong plug and play support for code component composition reuse, and furthest provide transparence to strictly restricted specification of code component in development of component itself.

Admissibility Conditions for Symbolic Sequences in Dynamics of Digital Filter with Two's Complement Arithmetic

In this paper, we discuss a class of piecewise linear hyperbolic maps on the 2-torus. These maps arise in the second-order digital fdter with two＇ s complement arithmetic. By introducing codings underlying the map operations, we give some admissibility conditions for symbolic sequences and find some periodic properties of these symbolic sequences. Then we use these conditions to check the admissibility of periodic symbol sequences.

An Adaptive Joint Source/Channel Coding Using Error Correcting Arithmetic Codes

An approximately optimal adaptive arithmetic coding (AC) system using a forbidden symbol (FS) over noisy channels was proposed which allows one to jointly and adaptively design the source decoding and channel correcting in a single process, with superior performance compared with traditional separated techniques. The concept of adaptiveness is applied not only to the source model but also to the amount of coding redundancy. In addition, an improved branch metric computing algorithm and a faster sequential searching algorithm compared with the system proposed by Grangetto were proposed. The proposed system is tested in the case of image transmission over the AWGN channel, and compared with traditional separated system in terms of packet error rate and complexity. Both hard and soft decoding were taken into account.

基于地域文化符号的列车涂装设计研究

目的探究基于地域文化符号的列车涂装设计方法与理论。方法对列车涂装设计概念,列车涂装设计与地域文化的关联、地域文化符号的构成、罗兰·巴特文化符码理论、杨裕富设计文化符码说进行了分析和探讨;提出了列车涂装设计三层次结构模型、设计文化符码转换及应用思路;设计实验了基于地域文化符号的宁波市域列车涂装设计方案。结果验证了设计文化符码三层次模型、设计文化符码转换及应用思路对地域文化符号在列车涂装设计中的应用有效性和可行性。结论地域文化符号融入列车涂装设计中,可以体现地域文化特色,传达地域文化内涵、塑造地域文化意象;通过设计文化符码三层次结构模型能够为列车涂装设计提供分析工具和设计方法,实现列车涂装的创意定位、意义传达和设计表现。

Phase-domain blind estimation of symbol duration based on Haar wavelet transform

A phase-domain blind estimator of symbol duration based on Haar wavelet transform（HWT） is proposed.It can estimate the symbol duration of phase modulated signals,such as M-ary phase-shift keying（MPSK） signals and polyphase coded signals.The closed form of the spectrum of HWT is derived.Theoretical analysis shows the frequency of the first spectral peak is equal to the symbol rate,which is the reciprocal of symbol duration.Thus the symbol duration can be extracted from the spectrum.Subsequently,the optimum wavelet scale is determined according to the maximum output signal to noise ratio（OSNR） criterion.MAT-LAB simulations show that this algorithm can blindly estimate the symbol duration without any prior knowledge.This estimator need not estimate the carrier frequency and has the characteristics of low computation complexity and high accuracy.

无尺寸约束的不透明谓词构建算法

结合不透明谓词,控制流混淆可以进行语义保持的变换,从而达到代码保护的目的。然而,现有的不透明谓词容易遭受符号执行攻击且存在小符号变量问题。为了解决上述问题,结合符号变量和数组利用单数组元素嵌套和符号变量模加运算设计不等条件表达式,并提出无尺寸约束的不透明谓词构建算法。基于该算法构建的不透明谓词混淆可以令攻击者错误地将不透明谓词识别为普通谓词或者将普通谓词识别为不透明谓词,从而有效抵御符号执行攻击。此外,利用不透明谓词检测以及虚假控制流去除等测试程序,对应用了无尺寸约束的不透明谓词混淆后程序的强度、弹性及开销进行实验测试分析。测试结果表明,基于所提算法实现的不透明谓词混淆不仅具有高强度和低开销,而且在新测试环境下仍然具有较高的抗反混淆弹性。

基于预测的多符号翻转多元LDPC译码算法

针对基于汉明距离和预测的符号翻转多元低密度奇偶校验码译码算法具有复杂度低、硬件实现简单等优势,但其性能有限且译码收敛速度较慢的问题,本文提出一种基于多符号翻转多元LDPC译码算法。首先,对用于翻转的度量值进行修改。在迭代过程中,计算基于目标函数得到的翻转度量值以及前一次相应的度量值进行累积处理后,得到新的翻转度量值,并用于对下一个符号的预测;其次,相比于单符号翻转的原算法,本算法引入多符号翻转策略,在迭代过程中翻转多个满足翻转阈值条件的变量节点。仿真和数值结果表明:与原算法相比,本文算法在性能上可获得约0.4 dB的增益。此外,该算法具有更少的平均迭代次数,因此译码收敛速度更快。

博物馆观众留言的分析策略与研究路径——以中国人民革命军事博物馆抗美援朝展留言簿文本为例

博物馆观众留言簿是重要的观众反馈方式,是博物馆最常使用的意见征集和观众交流手段。以符号编码的方式对中国人民革命军事博物馆《铭记伟大胜利捍卫和平正义--纪念中国人民志愿军抗美援朝出国作战70周年主题展览》观众留言簿文本分析表明,“情感表达”是贯穿该留言簿文本内容的主线与核心类属。该展览观众留言簿成为了观众与自身和外界进行情感表达与交流的媒介,这一特性也使博物馆观众留言簿在博物馆实务工作和观众研究工作中的应用成为可能。

河套文化的影像传播实践

河套文化融合黄河文化、草原文化、农耕文化和边塞文化等多种文化形态,包容性和共生性是河套文化的重要特征。通过影像的手段对河套文化进行记录、保存、阐释和传播是地域文化生长的必要过程,挖掘、利用和激活已有文化资源的过程需要融入时代语境。优化影像传播策略需要挖掘地域文化内涵以重塑文化自信。文化符号编码融合大众文化、流行文化等多种文化元素,在乡村振兴背景下重估农耕文化本土叙事价值。

作战标号颜色与几何视觉编码融合显示技术

针对作战装备及野外战场环境的信息呈现,基于作战标号颜色与几何视觉编码的融合显示技术,提出一种对颜色军事语义通过几何辅助进行强化表征的方法,采用贝塞尔曲线对作战标号进行视觉优化处理;设计了“矩形+贝赛尔曲线”的融合显示样式,对作战标号的可视化方式进行研究,使显示样式具有较好的光滑性、视觉分离等效果;增强了作战标号的军事表达能力与人机交互功能,该设计能较好地提升战场态势的信息呈现水平。

网络蠕虫研究与进展

随着网络系统应用及复杂性的增加,网络蠕虫成为网络系统安全的重要威胁.在网络环境下,多样化的传播途径和复杂的应用环境使网络蠕虫的发生频率增高、潜伏性变强、覆盖面更广,网络蠕虫成为恶意代码研究中的首要课题.首先综合论述网络蠕虫的研究概况,然后剖析网络蠕虫的基本定义、功能结构和工作原理,讨论网络蠕虫的扫描策略和传播模型,归纳总结目前防范网络蠕虫的最新技术.

基于代码注入的反模糊测试技术

现代灰盒模糊测试器可以通过从程序内部获取信息反馈,可以在短时间内发现大量漏洞。但是如果这项技术被滥用,将对企业和用户造成极大的伤害。为了避免软件程序被随意分析,反模糊测试技术应运而生。然而,现有的反模糊测试技术存在效率低、开销大、效果不理想、使用困难等问题。为了解决此类问题,本文提出了一种基于代码注入的新型反模糊测试技术。本文方法主要针对现代模糊测试器常用的插桩技术,利用插桩技术的局限,使用代码注入的方式绕过模糊测试器的信息检测,从而干扰模糊测试器分析目标程序,最终达到阻止模糊测试器工作的目的。为验证这种新型反模糊测试技术的有效性与处理性能,本文将该方法与当前最先进的反模糊测试技术作用于同一程序并进行比较。结果表明,本方法可以以更小的程序体积和更低程序运行开销来阻止不同的模糊测试器对目标程序进行模糊测试。