多重数字签名技术在办公自动化系统中的应用

随着电子商务的发展,应用需求的复杂化,数字签名技术得到广泛应用,该文介绍了公开密钥加密体制,数字签名技术原理和功能,以及多重数字签名技术,并探讨多重数字签名技术在办公自动化系统中的应用的安全解决方案.     

Topologies for the digital spaces and

We show that there are only two topologies in and five topologies in whose connected sets are connected in the intuitive sense. Both topologies for are well known (e.g., one is presented in D. Marcus, F. Wyse et al., Amer. Math. Monthly 77 (1979) 1119, and the second in E. Khalimsky et al., Topology and its Applications 36 (1990) 1) and found applications in computer graphics and computer vision (e.g., A. Rosenfeld, Amer. Math. Monthly 77 (1979) pp. 621, and T.Y. Kong et al., Amer. Math. Monthly 98 (1991) 901). Two of the five topologies for are products of the topologies known from and . The remaining three topologies for are also generated from the two topologies for , however, they are not product topologies.     

Digital learners and the overlapping of their personal and educational digital engagement

Current K-12 students are considered digital learners because technology is as pervasive in their academic world as in their personal lives. Technology enthusiasts argue that these learners are the “digital natives” having sophisticated technology knowledge and skills that can be potentially harnessed for better learning engagement inside the classroom. This phenomenological study investigates how some current high school students as the digital learners engage with technology at home and school; and how these two types of engagement overlap in their learning inside the classroom. Data were gathered from phenomenological three series in-depth interviews with five participants and also field observation. Findings show that the overlap between the personal and educational digital engagement(s) of these students was not necessarily positive as portrayed by the prevalent discourses of technology enthusiasts. The overlapping had mixed roles – facilitative as well as obstructive. Pedagogical and future research implications are discussed.     

数字摄影测量技术与数字地球空间数据框架的建设

数字地球的构建与数字摄影测量、遥感、全球定位系统、地理信息系统、计算机、宽带网络、多维虚拟现实等新技术有着紧密的联系,数字摄影测量已成为构建数字地球提供空间数据框架的一种不可或缺的技术手段。基于数字地球的发展需求,结合数字摄影测量技术优势和最新发展,着重阐述了数字摄影测量在数字地球空间框架的建设中的作用。随着数字地球发展的深化,数字摄影测量将显示着愈来愈重要的作用。
     

OpenDLib: an infrastructure for new generation digital libraries

This paper presents OpenDLib, a digital library infrastructure that provides capabilities for new-generation digital libraries. In particular, the paper introduces a document model that can be used to represent a wide variety of document types and describes the open architectural infrastructure that allows for the expansion of the digital library through the dynamic plugin of new services.     

在VC++中用CryptoAPI保证安全数据通信

Microsoft的加密应用程序接口CryptoAPI使开发人员可以在应用程序中加入强大的保证数据通信安全性的功能。本文研究了在VC 应用程序中利用CryptoAPI实现数字签名和验证、数据加密和解密等安全数据通信的关键技术,并给出了实现的方法。     

高精度正弦波数字合成技术

以数字合成技术为基础。采用数字调幅、数字变频、数字移相技术，提出了一种高精度正弦波发生电路的实现方法。可实现全范围的高精度调幅调频调相。     

数字图像认证技术

1 引言在当今信息时代,以Internet为先锋的网络化浪潮正日益将人们的工作、生活和娱乐涌入全球一体化的数字世界。快捷廉价的数字传输手段为人们获取和交流信息带来了极大便利,然而,网络信息的全透明性和易操作性,却又使得恶意攻击者可以轻易地对其进行篡改或伪造,由此可能造成极为严     

PKI框架下的SET购物流程

随着因特网、计算机技术、信息技术的迅速发展 ,电子商务已深入到社会生活的各个方面。基于卡业务的SET协议 ,已经成为电子商务中网上购物的一种主要模式 ,它通过采用基于PKI的数字证书技术 ,实现了电子商务中信息的机密性、真实性、完整性和不可否认性     

基于数字签名的数字水印系统

数字水印技术是解决数字作品版权保护问题的一个有力的武器。本文结合密码学理论和技术,提出了一种结合数字水印和数字签名的安全保障机制。结合数字签名技术把原始图像所有者有关信息通过认证中心进行认证签名,从而能够保证了水印的安全性。     

基于信息集成技术的数字矿区研究

本文简要回顾了数字地球基本理论和基本信息集成技术，讨论了在数字地球和信息集成技术基础上实现数字矿区的方法，并讨论了数字矿区的结构模型。     

Self-efficacy and anxiety of digital natives in face of compulsory computer-mediated tasks: A study about digital capabilities and limitations

Digital limitations (or, conversely, digital capabilities) are a new way to frame the digital divide discourse in three dimensions: access, cognition and behavior. Digital limitations address an individual's barriers to properly access the information and communication technologies (ICTs), as well as his/her cognitive disabilities and negative behaviors towards ICT use effectiveness. In a survey with 174 undergraduate students in a traditional state university in underdeveloped Northeastern Brazil who compulsorily use an institutional ICT-based academic system, we investigated the factorial structure and the relationship of two constructs that pertain to the cognitive dimension of digital limitations – computer self-efficacy and anxiety. Our findings address the negative correlation between the two constructs and the unanticipated proposition that both low and high levels of self-efficacy and anxiety do not signal per se the presence of cognitive digital limitations or capabilities.     

单相功率因数校正的改进预测控制算法研究

随着数字控制技术的不断发展,在电源变换领域涌现出许多全新的控制策略来弥补模拟控制的不足.文中采用改进的预测控制算法,不仅解决了数字控制系统难于实现高频化的问题,而且消除了输出电压纹波对控制系统性能的影响,使得系统的功率因数得到了进一步改善,采用这种控制策略,还可令系统的输出电压基本不受到负载变化的影响,输出电压的稳定性更好.使用Matlab/simulink仿真软件对整体控制系统进行了数字仿真实验,并取得了比较理想的控制效果.     

Digital boundary tracking

In many three-dimensional imaging applications, the three-dimensional space is represented by an array of cubical volume elements (voxels) and a subset of the voxels is specified by some property. Objects in the scene are then recognised by being components of the specified set and individual boundaries are recognised as sets of voxel faces separating objects from components in the complement of the specified set. This paper deals with the problem of algorithmic tracking of such a boundary specified by one of the voxel faces lying in it. The paper is expository in that all ideas are carefully motivated and introduced. Its original contribution is the investigation of the question of whether the use of a queue (of loose ends in the tracking process which are to be picked up again to complete the tracking) is necessary for an algorithmic tracker of boundaries in three-dimensional space. Such a queue is not needed for two-dimensional boundary tracking, but published three-dimensional boundary trackers all make use of such a thing. We prove that this is not accidental: under some mild assumptions, a boundary tracker without a queue will fail its task on some three-dimensional boundaries.     

数字直扩接收机中同步环路设计与仿真

同步是扩频通信系统中的一个重要问题。该文详细介绍了直接序列扩频（DSSS）通信系统中，数字科斯塔斯（Costas）环、数字延迟锁定环（DLL）的工作原理和环路中二阶环路滤波器的设计方法，并根据该原理提出了一种新的码环实现方案。使用Matlab对数字直扩接收机进行了仿真。不同环路滤波器参数下环路捕获性能的仿真结果及系统解调误码率证明了该环路滤波器在Costas环和DLL环中的正确性和实用性。其较好地解决了直扩系统中载波和伪码精确同步的问题。该文所设计的数字直扩接收机可有效地应用于CDMA及GPS等系统之中。     

基于彩色静止数字图像的信息隐藏技术研究

数字图像的信息隐蔽技术是数字图像处理领域中最具挑战性、最为活跃的研究课题之一。本文概述了数字图像的信息隐蔽技术，并给出了一个新的基于彩色静止数字图像的信息隐蔽算法。     

基于数字水印技术的安全电子合同系统

本文就电子合同的易仿造和易篡改提出了一种新的解决方案——采用数字水印技术来保证电子合同的完整性和不可否认性。本方案以在某企业的具体应用为背景实现了一套对电子合同进行散列、数字签名,然后通过水印技术将信息隐藏入合同的安全电子合同系统。     

用CAPICOM组件实现应用系统安全性的方法

介绍了基于公钥基础结构PKI的保证网络数据安全性的主要技术以及微软的高性能加密应用程序接口组件CAPICOM，并通过实例说明了利用CAPICOM实现应用系统数据安全性的方法。     

一种新型的数码防伪系统

数码防伪是一种综合利用先进的数字编码、加密、数据库、计算机网络、交互式语音处理（IRV）等技术的新型高科技防伪技术，是当前国内最为流行的防伪技术之一。文章首先分析、借鉴了当前几种主要的数码防伪技术及其安全性；在此基础上进行创新，提出了一种新型的数码防伪系统；另外，还列举了两个应用实例进行检验。     

认证系统中的消息数字证书方案

数字证书是认证系统中的核心,随着公共密钥基础设施(PKI)的建立和认证中心(CA)的建设,用于身份认证和实体鉴别的身份证书已形成了完备的体系。X.509中对身份数字证书的结构、申请、使用、废止等进行了详细的描述,X.509数字身份证书已成为事实上的标准,国内外的CA建设方案大都采用了该证书标准。事实上,认证系统要解决的问题除了身份认证外,另一类重要的应用在于对消息完整性的鉴别,而目前在消息完整性认证理论中却没有提出相应的理论和标准,文章在研究了消息认证的基础上提出了消息数字证书的概念,设计了一类数字消息证书,并对这类数字消息证书的应用与实现中的相关问题进行了探讨。