无重叠生成文法的一义可解析性及图林等价性

为了实现有效的文法解析，定义了一种生成规则受限的短语结构文法，称为无重叠生成文法。证明了该类文法的任何语言句子都可以被无回朔无失败地解析。尽管该类文法的生成规则受到很大的限制．但这种文法的生成能力仍然和图灵机等同。     

结合二叉判决图和布尔可满足性的等价性验证算法

本文提出了一种结合二叉判决图BDD和布尔可满足性SAT的新颖组合电路等价性验证技术.算法是在与/非图AIG中进行推理,并交替使用BDD扩展和基于电路SAT解算器简化电路.如尚未解决,将用基于合取范式SAT解算器进行推理.与已有算法相比主要有如下改进:在AIG中结合多种引擎进行简化,不存在误判可能;充分利用了基于电路解算器和基于合取范式解算器各自优点,减小了SAT推理的搜索空间.实验结果表明了本算法的有效性.     

固定单站对三维运动辐射源无源定位算法及可观测性分析

实现固定单站对运动辐射源无源定位,传统的方法是测量TOA和DOA。本文将方位角变化率测量信息也引入该定位问题,提出了基于MGEKF(修正增益扩展卡尔曼滤波),对三维运动辐射源的无源定位跟踪算法。通过推导伪线性测量方程,本文进行了测量TOA和DOA对三维运动目标无源定位的可观测性分析。最后给出了计算机仿真结果。     

无源双基地雷达目标运动分析的可观测性

本文研究利用外辐射源的单站无源定位和跟踪技术的可观测性问题。引入相容目标轨迹的概念,分析了三维N阶运动目标在不同观测信息条件下的相容轨迹的几何分布,并证明多普勒和到达时差观测是等价观测量。     

DOA和TOA的单站无源定位可观测性分析

在现有单站无源定位技术的基础上,介绍了新的基于机动辐射源目标的DOA和TOA测量信息的单站无源定位的可观测性分析.此分析直接应用非线性系统的可观测性分析原理,得到了基于DOA和TOA测量信息的单站无源定位的可观测性条件,并对其进行了计算机仿真.与文献[1-2]相比,此可观测性分析更直观更简明.     

The vocabulary and grammar of color patterns

We determine the basic categories and the hierarchy of rules used by humans in judging similarity and matching of color patterns. The categories are: (1) overall color; (2) directionality and orientation; (3) regularity and placement; (4) color purity; (5) complexity and heaviness. These categories form the pattern vocabulary which is governed by the grammar rules. Both the vocabulary and the grammar were obtained as a result of a subjective experiment. Experimental data were interpreted using multidimensional scaling techniques yielding the vocabulary and the hierarchical clustering analysis, yielding the grammar rules. Finally, we give a short overview of the existing techniques that can be used to extract and measure the elements of the vocabulary.     

The universality of multidimensional switching networks

Multidimensional switching networks are networks that utilize more than one degree of freedom (e.g., space, wavelength, time, code). The main idea is to use several dimensions of practical size in hierarchical multiplexing to overcome the physical constraints present when using only one dimension of large size. We generalize the case of one-dimensional switching networks to k-dimensional switching networks. Such networks have high degree of connectivity (≫1000) and reduced complexity compared to one-dimensional networks. We introduce a technology-independent universal theory discussing two models, one of multidimensional selective switching, and the other of multidimensional broadcasting, concentrating on complexity and channel assignment. The required size of each dimension, hardware complexities, channel assignment, and corresponding routing algorithms and their time complexities are discussed. It is shown with examples bow the complexity of these networks can be reduced to a minimum by optimal allocation of the complexity in each dimension. Several realizations of three-dimensional wavelength-time-space networks using different technologies (e.g., fiber optics, acousto-optics, free-space and photonic switching) are described for both models     

砂轮激光修整设备及参量选择的研究

为了选择合适的激光设备及参量,以便提高激光修整砂轮效率和精度,采用300W氙灯抽运YAG普通脉冲激光器、80W声光调Q YAG脉冲激光器对青铜金刚石砂轮进行了单脉冲和连续脉冲烧蚀试验,借助于显微镜分析了激光作用后砂轮表面的微观形貌,并通过理论推导,得出一组公式,在考虑砂轮修整精度和效率的前提下,有效地缩小激光器及参量的选择范围,有助于针对不同的砂轮选择更为合适的激光参量进行更有效的修整。结果表明,声光调Q YAG脉冲激光器比氙灯抽运普通YAG脉冲激光器单脉冲能量小、脉冲频率高、脉宽窄、峰值功率高,更适合用于砂轮的高精度、高效率修整。     

On the universality of Burnashev's error exponent

We consider communication over a time-invariant discrete memoryless channel (DMC) with noiseless and instantaneous feedback. We assume that the transmitter and the receiver are not aware of the underlying channel, however, they know that it belongs to some specific family of DMCs. Recent results show that for certain families (e.g., binary-symmetric channels and Z channels) there exist coding schemes that universally achieve any rate below capacity while attaining Burnashev's error exponent. We show that this is not the case in general by deriving an upper bound to the universally achievable error exponent.     

On the universality of the LZ-based decoding algorithm

A universal decoder for a family of channels is a decoder that can be designed without prior knowledge of the particular channel in the family over which transmission takes place, and it yet attains the same random-coding error exponent as the optimal decoder tuned to the channel in use. We study Ziv's (1985) decoding algorithm, which is based on Lempel-Ziv (1978) incremental string parsing, and demonstrate that while it was originally proposed as a universal decoder for the family of finite-state channels with deterministic (but unknown) transitions, it is in fact universal for the broader class of all finite-state channels. We also demonstrate that the generalized likelihood decoder may not be universal even for finite families for which a universal decoder always exists     

An experimental study on the universality of visual vocabularies

Bag-of-visual-words has been shown to be a powerful image representation and attained success in many computer vision and pattern recognition applications. Usually for a given classification task, researchers choose to build a specific visual vocabulary, and the problem of building a universal visual vocabulary is rarely addressed. In this paper we conduct extensive classification experiments with three features on four image datasets and show that the visual vocabularies built from different datasets can be exchanged without apparent performance loss. Furthermore, we investigate the correlation between the visual vocabularies built from different datasets and find that they are nearly identical, which explains why they are universal across classification tasks. We believe that this work reveals what is behind the universality of visual vocabularies and narrows the gap between bag-of-visual-words and bag-of-words in text domain.