一种综合空域和时频域的数字水印算法

提出一种空域和时频域相结合的多分辨率灰度图像水印算法。该算法对原始载体图像进行离散小波分解,并对灰度水印图像先进行拉普拉斯金字塔分解再进行位平面分解。将水印图像位平面分解系数嵌入到原始图像的水平和垂直分量上,水印嵌入小波系数的位置由具有混沌特性的Arnold映射确定,从而实现水印的盲提取。实验结果证明,该算法对图像的普通处理,如噪声、滤波、剪切、JPEG压缩和旋转等,均具有较好的鲁棒性。     

基于双线性对的无证书签名与群签名方案

传统数字签名方案的证书存储和管理开销较大,基于身份的数字签名方案无法解决其固有的密钥托管问题,而无证书签名方案无需使用公钥证书,且没有密钥托管问题。为此,提出一个基于双线性映射的无证书签名方案,并在随机预言机模型下证明其安全性。在此基础上设计一个无证书群签名方案,其安全性建立在计算Diffie-Hellman问题的困难性假设上。性能分析表明,2种签名方案在保证安全性的前提下,具有较高的执行效率。     

基于双曲线映射签名的高效可分电子现金系统

基于双曲线映射的签名设计了一种新型可分电子现金方案,方案中有效地加入了压缩支付和批处理支付,计算时间复杂度较小,从而使得系统的整体效率较高。另外,方案中无需可信第三方(TTP)的参与,因而系统的整体开销较小。方案的安全性基于q-SDK假设、计算离散对数困难性假设以及单向散列函数存在性假设。     

基于模式映射的GML文档存储

随着地理信息系统GIS(Geography Markup Language)的广泛应用,GML己经成为事实上的空间数据编码、传输、共享和发布的一种国际标准。近年来,大量GML数据以文档形式出现,对如何高效地存储和管理GML数据提出了新的挑战。根据GML文档的特点,提出了一种基于模式映射的存储方法。首先,根据映射规则将GML模式生成对象-关系数据库模式;其次,解析GML文档并根据映射信息构造相应的SQL语句,将数据存储于数据库。实验表明,提出的存储方法是可行、高效的。     

C-AMTE: A location mechanism for flexible cache management in chip multiprocessors

This paper describes Constrained Associative-Mapping-of-Tracking-Entries (C-AMTE), a scalable mechanism to facilitate flexible and efficient distributed cache management in large-scale chip multiprocessors (CMPs). C-AMTE enables fast locating of cache blocks in CMP cache schemes that employ one-to-one or one-to-many associative mappings. C-AMTE stores in per-core data structures tracking entries to avoid on-chip interconnect traffic outburst or long distance directory lookups. Simulation results using a full system simulator demonstrate that C-AMTE achieves improvement in cache access latency by up to 34.4%, close to that of a perfect location strategy.     

CAFES: A framework for intrachip application modeling and communication architecture design

This paper describes CAFES, an extensible, open-source framework supporting several tasks related to high-level modeling and design of applications employing complex intrachip communication infrastructures. CAFES comprises several built-in models, including application, communication architecture, energy consumption and timing models. It also includes a set of generic and specific algorithms and additional supporting tools, which jointly with the cited models allow the designer to describe and evaluate applications requirements and constraints on specified communication architectures. Several examples of the use of CAFES underline the usefulness of the framework. Some of these are approached in this paper: (i) a realistic application captured at high-level that has its computation time estimated after mapping at the clock cycle level; (ii) a multi-application system that is automatically mapped to a large intrachip network with related tasks occupying contiguous areas in the chip layout; (iii) a set of mapping algorithms explored to define trade-offs between run time and energy savings for small to large intrachip communication architectures.     

On the generalized Hyers-Ulam stability of multi-quadratic mappings

A mapping f:Vⁿ?W, where V is a commutative group, W is a linear space, and n≥2 is an integer, is called multi-quadratic if it is quadratic in each variable. In this paper, we prove the generalized Hyers-Ulam stability of multi-quadratic mappings in Banach spaces and complete non-Archimedean spaces.     

Halpern-type iterations for strongly relatively nonexpansive mappings in Banach spaces

In this paper, we note that the main convergence theorem in Zhang et al. (2011) [21] is incorrect and we prove a correction. We also modify Halpern’s iteration for finding a fixed point of a strongly relatively nonexpansive mapping in a Banach space. Consequently, two strong convergence theorems for a relatively nonexpansive mapping and for a mapping of firmly nonexpansive type are deduced. Using the concept of duality theorems, we obtain analogue results for strongly generalized nonexpansive mappings and for mappings of firmly generalized nonexpansive type. In addition, we study two strong convergence theorems concerning two types of resolvents of a maximal monotone operator in a Banach space.     

Soft groups and normalistic soft groups

Soft set theory, proposed by Molodtsov, has been regarded as an effective mathematical tool to deal with uncertainties. In this paper, first we correct some of the problematic cases in a previous paper by Akta? and Çag˜man [H. Akta?, N. Çag˜man, Soft sets and soft groups, Inf. Sci. 177 (2007) 2726-2735]. Moreover, we introduce the concepts of normalistic soft group and normalistic soft group homomorphism, study their several related properties, and investigate some structures that are preserved under normalistic soft group homomorphisms.     

PIRF-Nav 2.0: Fast and online incremental appearance-based loop-closure detection in an indoor environment

This paper presents a fast and online incremental solution for an appearance-based loop-closure detection problem in a dynamic indoor environment. Closing the loop in a dynamic environment has been an important topic in robotics for decades. Recently, PIRF-Nav has been reported as being successful in achieving high recall rate at precision 1. However, PIRF-Nav has three main disadvantages: (i) the computational expense of PIRF-Nav is beyond real-time, (ii) it utilizes a large amount of memory in the redundant process of keeping signatures of places, and (iii) it is ill-suited to an indoor environment. These factors hinder the use of PIRF-Nav in a general environment for long-term, high-speed mobile robotic applications. Therefore, this paper proposes two techniques: (i) new modified PIRF extraction that makes the system more suitable for an indoor environment and (ii) new dictionary management that can eliminate redundant searching and conserve memory consumption. The results show that our proposed method can complete tasks up to 12 times faster than PIRF-Nav with only a slight percentage decline in recall. In addition, we collected additional data from a university canteen crowded during lunch time. Even in this crowded indoor environment, our proposed method has better real-time processing performance compared with other methods.