线上社交网络访问控制模型综述

就线上社交网络访问控制模型的研究现状进行了分析、总结,指出当前研究中存在的关键问题和面临的挑战,并对此类模型的发展趋势和未来研究方向做出预测. 线上社交网络方兴未艾,数据共享、隐私保护等问题日渐引起公众注意. 作为信息安全手段,传统访问控制模型已不适应线上社交网络复杂环境下的安全需求. 近年来针对线上社交网络访问控制模型的研究正成为热点问题,多个研究小组均从不同角度提出了新的访问控制模型.     

面向社交网络的访问控制模型和策略研究进展

作为信息保护有效手段之一的访问控制技术,可以保障信息仅能被合法用户访问,防止信息的泄露,势必成为在线社交网络中信息保护方法的重要组成部分。通过分析在线社交网络的特点,从访问控制模型与访问控制策略2个角度出发,对目前在线社交网络中的访问控制研究进行深入探讨,并对相关研究进行整理与分析。     

在物联网中基于社交网络方法的用户生成业务框架研究

用户生成业务(简称UGS),意为普通用户不用编程仅通过简单操作便可自己创建个性化业务。目前该技术在互联网中得到了一定的应用。社交网络的风靡给人与人之间的联系提供了丰富的数据,基于这些数据可以分析用户间的相似度,从而为相似的用户推荐业务。本文研究了传统基于社交网络的用户生成业务框架和应用在物联网环境时传统框架的不足。提出了一个基于动态社交网络的动态社交网络用户生成业务系统框架,提升了用户生成业务系统在物联网业务环境中的性能。     

社交网络中具有可传递性的细粒度访问控制方案

针对社交网络中隐私保护的需求,基于属性基加密(ABE)算法,提出了一种权限可传递性的细粒度访问控制方案。在方案中通过属性的设置实现了社交网络成员不同粒度的刻画,为细粒度加密和访问提供了基础;同时在方案中引入了代理服务器,对非授权成员与授权成员之间的关系进行分析,从而判定非授权成员的访问权限。若该成员可以获得访问权限,密钥生成中心依据授权成员的属性为其生成解密密钥,进而实现访问权限的传递性。与其他基于访问控制或加密技术的隐私保护方案相比,所提方案将对数据的访问控制和加密保护相统一,在实现数据加密的同时,提供细粒度的访问控制;并结合社交网络的特点实现了访问权限的传递性。     

一种面向社交网络的细粒度密文访问控制方案

针对社交网络的隐私保护问题,采用属性基加密算法,提出一种安全、高效、细粒度的社交网络访问控制方案,并建立社交网络体系结构。通过引入线性秘密共享方案构造访问控制策略,实现灵活的访问控制结构,利用重加密技术,将部分重加密工作转移给社交网络平台执行,在保证用户数据安全的前提下,降低用户的计算代价,通过分析非授权成员与授权成员之间的关系,判定非授权成员的访问权限,进而实现访问权限的传递,并分析方案的安全性和有效性。分析结果表明,与现有基于加密技术的隐私保护方案相比,该方案能提高访问结构的表达能力和解密效率。     

基于博弈论的社交网络的控制方法

社交网络虽然实现了网络化的人际信息交流和交友．但同时也存在着大量的例如个人隐私信息泄露等问题。面对这种情况,计算机学术界提出一种基于博弈论的能够避免泄露用户隐私信息的新型的社交网络的访问控制方法。就这一基于博弈论的社交网络控制方法进行相关的简述和分析,以便于人们了解和认识这种社交网络的博弈论控制方法。     

网络疑似入侵环境下的最优接口访问控制模型仿真

在网络疑似入侵环境下通过最优接口访问控制实现网络入侵的可靠性拦截,保障网络安全。传统方法采用自由链路分散控制模型进行网络入侵检测和接口访问控制,在受到较大的特征干扰下,入侵访问控制和拦截性能不好。提出一种基于自适应循环堆栈接口调度的网络疑似入侵环境下的最优接口访问控制模型。进行接口访问控制模型总体设计及组件模块分析,接口访问控制系统包括通信库、协议库、核心控制库和资源库,采用小波包自适应波束调制方法进行入侵检测算法设计,作为接口访问控制系统软件核心。通过SDICmdCon寄存器设置网络疑似入侵环境下的最优接口的内核,在嵌入式Linux环境下通过自适应循环堆栈接口调度实现接口访问控制的软件开发。仿真结果表明,采用该模型进行网络入侵检测,准确检测性能较好,通过最优接口访问控制,实现对网络入侵数据的准确识别和拦截。     

对等网络环境下的构件查询访问控制框架

阐述对等网络环境下的构件查询访问控制框架及其策略与机制.首先,简要介绍当前应用较多的传统访问控制模型及其机制;接着,分析对等网络环境下构件查询访问控制的特点;最后,针对构件查询访问控制的特点,提出并详细阐述一种基于信任的构件查询访问控制框架.     

无线ATM网介质访问控制协议的研究

近年来无线ATM网络得到广泛研究,扩展ATM网络的宽带业务至无线环境面临许多方面的问题。介质访问控制(MAC)方法是无线ATM网的关键技术之一。MAC层协议的好坏直接影响系统性能和移动终端的复杂性。文中综合分析目前已有的无线ATM介质访问控制协议及方法,指出设计无线ATM网MAC层协议的三条原则,提出下一步研究方向。     

云环境下SNS隐私保护方案

社交网络存储的数据实际都是外包给并不完全可信的云服务商。针对社交网络隐私安全和属性更新问题,提出一种云环境中具有策略隐藏和属性撤销的属性基加密方案。通过分解密钥产生方式降低用户端的计算量,引入合数阶的双线性群实现访问策略隐藏,并利用令牌树和陷门机制灵活且高效地完成属性撤销。而且,该方案在标准假设下可被证明是安全的。因此,将该方案运用于社交网络,将数据加密存储于云服务端是安全可行的。与其他方案相比,该方案既保护了访问策略的隐私,又具有多样的访问控制功能,在计算和存储等方面更有优势。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).