网络安全评估的研究

目前,网络已经给人们的生活、工作和学习带来了巨大的转变,人们在享受由网络带来的便利的同时,也受到了安全问题的影响。由于网络具有资源共享、分布广泛和开放性等特点,给网络犯罪分子有了可趁之机,给社会和个人带来了不可估量的危害。网络黑客对网络的攻击主要是利用网络管理和技术方面的漏洞,所以,对所在的网络进行安全评估,有针对性地对网络进行修补工作,可以从根本上解决网络的安全问题,将隐患杜绝于外。在现有应用水平基础之上,建立和完善网络安全评估系统,对于网络的正常、安全和平稳运行是具有重大的实际应用价值。     

ARP攻击防范策略的研究

网络监听,不仅给网络管理监控带来了方便,也给黑客留下了空间,ARP欺骗攻击就是其中之一。本文阐述了网络监听的由来,简述了网络寻址的原理和网络信息访问的具体过程。在分析了ARP协议存在的安全问题后,针对协议设计上不足,提出防范ARP攻击的策略。     

计算机网络安全技术及其发展趋势

随着计算机网络技术的飞速发展,网络技术给我们的工作和生活带来了前所未有的方便,我们在享受网络给我们带来方便的同时,网络的安全问题也日益突出。本文从网络安全面临的危险入手重点介绍了防火墙技术,入侵检测系统,讨论了它们的局限性,最后介绍了计算机网络安全技术的发展趋势。     

打击网络犯罪与相关对策分析

网络给人们带来了惊喜和方便,同时犯罪分子也利用它给人类社会带来危害。近年来,网络犯罪案件呈现出逐渐上升趋势。它不仅严重危害计算机及网络数据和信息安全,而且给社会造成了巨大的经济损失和危害。本文分析了网络犯罪现状和特点,探讨了网络犯罪的手法及打击犯罪的相应对策。     

巧用SANGFOR轻松管理学校网络中心

网络技术的飞速发展给学校的教育教学带来了划时代的意义,教育教学信息化、网络化已经成为时代发展的趋势。正所谓"成也网络,忧也网络",网络在给我们带来巨大益处的同时,也给我们学校网络管理人员带来了许多问题与困惑。一些师生利用学校公共网络资源,在论坛上发表不负责任的言论,肆意攻击社会;还有少数人不断访问成人、色情网站,导致病毒泛滥,阻塞网络。过去由于技术、管理等多方面的原因,出现了师生上网"管不住"、"查不到"的尴尬局面。     

网络信息安全问题的法律探析

网络技术的发展以及应用深刻地影响着人类社会,在给人类带来巨大便利的同时也带来了诸如网络信息安全问题等隐患,这不仅在技术层面给我们提出新的问题,在法律层面也提出了更高的要求。本文介绍了对网络信息安全问题进行法理探讨的背景,并且在分析了国内外研究现状的基础上提出在法律层面解决网络信息安全问题的初步构想。     

信息时代下网络技术安全与网络防御探究

互联网的普及以及计算机的发展,给人们的生活带来了极大的方便,许多的商业活动都是通过网络进行,与此同时网络技术的安全也越来越受到人们的关注,在信息时代下网络技术的开放性和共享性给其带来了巨大的安全威胁,必须要进行全面的网络防御。本文分析了信息时代下保障网络信息安全的重要性,探讨了网络技术安全面临的威胁,并且探究了信息时代下计算机网络防御策略。     

一种遏制网络蠕虫传播的方案

当今是网络技术普及化的时代．但网络技术和计算机技术的发展给网络带来的负面影响也是明显的。目前对网络威胁最大的是木马和蠕虫。蠕虫的攻击给网络用户带来了巨大损失,也给他们留下了深刻印象。因此,蠕虫对网络的破坏性,引起安全人员的重视,安全人员对防治蠕虫提出了各种算法。在查阅相关蠕虫文献后,提出了一种遏制网络蠕虫传播的思路。简述了蠕虫的传播方式和途径,病毒传染机理和病毒破坏机理,提出了如何从寄生于蠕虫的程序,有效防止蠕虫的传播和减小蠕虫的传播范围。     

基于IPv6网络的流量控制策略

随着IPv6技术的日益成熟及IPv6网络建设规模的不断扩大,基于IPv6的应用也愈来愈多。IPv6网络在给网络用户提供很大的便利的同时,也给网络体系结构和网络性能与网络的安全等带来一定程度上的挑战。本文通过对网络流量的分析和研究,提出了一些这方面的控制策略。     

计算机通信网可靠性设计研究

随着社会经济的大繁荣、大发展,计算机通信在人们经济生活中的运用越来越多,计算机通信网络在给人们带来便利的同时,其通信网络可靠性漏洞也给企业和个人带来了巨大损失,本文从通信网络可靠性的角度出发,结合计算机通信网络设计过程中的实际,对计算机通信网络可靠性设计进行深入的研究和探讨。     

基于COM技术的油料自动计量控制管理系统

针对油库自动化管理的高效、安全、准确性等方面的迫切需求,利用COM技术对所采用的组态软件的结构进行了一定的抽象,提出逻辑三层结构,建立了基于COM技术的实用数据总线,实现了系统的扩展功能;把系统的所有功能均组件化,提高了系统的稳定性;结合机场油库的工作流程进行了管理软件的组态设计,实现了预定的目标;COM技术的应用为组态软件的开发提供了一种新的思路,并提供了一个可以运行的组态软件雏形。     

Computation of Approximate Polynomial GCDs and an Extension

Computation of approximate polynomial greatest common divisors (GCDs) is important both theoretically and due to its applications to control linear systems, network theory, and computer-aided design. We study two approaches to the solution so far omitted by the researchers, despite intensive recent work in this area. Correlation to numerical Padé approximation enabled us to improve computations for both problems (GCDs and Padé). Reduction to the approximation of polynomial zeros enabled us to obtain a new insight into the GCD problem and to devise effective solution algorithms. In particular, unlike the known algorithms, we estimate the degree of approximate GCDs at a low computational cost, and this enables us to obtain certified correct solution for a large class of input polynomials. We also restate the problem in terms of the norm of the perturbation of the zeros (rather than the coefficients) of the input polynomials, which leads us to the fast certified solution for any pair of input polynomials via the computation of their roots and the maximum matchings or connected components in the associated bipartite graph.     

Algebraic Composition of Function Tables

In general, a program is composed of smaller program segments using composition, conditional constructs or loop constructs. We present a theory which enables us to algebraically define and compute the composition of conditional expressions. The conditional expressions are represented using tabular notation. The formal definition of the composition allows us to compute the close form representation of the composition of tabular expressions. The presented approach is based on a many sorted algebra containing information preserving composition. This formal definition of composition is then “lifted” to an extended algebra containing tabular expressions. The presented theory provides very compact algorithms and proofs. Received July 1998 / Accepted in revised form January 2000     

Interactive Modeling of City Layouts using Layers of Procedural Content

In this paper, we present new solutions for the interactive modeling of city layouts that combine the power of procedural modeling with the flexibility of manual modeling. Procedural modeling enables us to quickly generate large city layouts, while manual modeling allows us to hand‐craft every aspect of a city. We introduce transformation and merging operators for both topology preserving and topology changing transformations based on graph cuts. In combination with a layering system, this allows intuitive manipulation of urban layouts using operations such as drag and drop, translation, rotation etc. In contrast to previous work, these operations always generate valid, i.e., intersection‐free layouts. Furthermore, we introduce anchored assignments to make sure that modifications are persistent even if the whole urban layout is regenerated.     

Trace and Testing Equivalence on Asynchronous Processes

We study trace and may-testing equivalences in the asynchronous versions of CCS and π-calculus. We start from the operational definition of the may-testing preorder and provide finitary and fully abstract trace-based characterizations for it, along with a complete in-equational proof system. We also touch upon two variants of this theory by first considering a more demanding equivalence notion (must-testing) and then a richer version of asynchronous CCS. The results throw light on the difference between synchronous and asynchronous communication and on the weaker testing power of asynchronous observations.     

Environmental Objects for Authoring Procedural Scenes

We propose a novel approach for authoring large scenes with automatic enhancement of objects to create geometric decoration details such as snow cover, icicles, fallen leaves, grass tufts or even trash. We introduce environmental objects that extend an input object geometry with a set of procedural effects that defines how the object reacts to the environment, and by a set of scalar fields that defines the influence of the object over of the environment. The user controls the scene by modifying environmental variables, such as temperature or humidity fields. The scene definition is hierarchical: objects can be grouped and their behaviours can be set at each level of the hierarchy. Our per object definition allows us to optimize and accelerate the effects computation, which also enables us to generate large scenes with many geometric details at a very high level of detail. In our implementation, a complex urban scene of 10 000 m², represented with details of less than 1 cm, can be locally modified and entirely regenerated in a few seconds.     

Extraction Of Feature Lines On Surface Meshes Based On Discrete Morse Theory

We present an approach for extracting extremal feature lines of scalar indicators on surface meshes, based on discrete Morse Theory. By computing initial Morse‐Smale complexes of the scalar indicators of the mesh, we obtain a candidate set of extremal feature lines of the surface. A hierarchy of Morse‐Smale complexes is computed by prioritizing feature lines according to a novel criterion and applying a cancellation procedure that allows us to select the most significant lines. Given the scalar indicators on the vertices of the mesh, the presented feature line extraction scheme is interpolation free and needs no derivative estimates. The technique is insensitive to noise and depends only on one parameter: the feature significance. We use the technique to extract surface features yielding impressive, non photorealistic images.     

Energy-Based Image Deformation

We present a general approach to shape deformation based on energy minimization, and applications of this approach to the problems of image resizing and 2D shape deformation. Our deformation energy generalizes that found in the prior art, while still admitting an efficient algorithm for its optimization. The key advantage of our energy function is the flexibility with which the set of "legal transformations" may be expressed; these transformations are the ones which are not considered to be distorting. This flexibility allows us to pose the problems of image resizing and 2D shape deformation in a natural way and generate minimally distorted results. It also allows us to strongly reduce undesirable foldovers or self-intersections. Results of both algorithms demonstrate the effectiveness of our approach.     

Topological Features in 2D Symmetric Higher‐Order Tensor Fields

The topological structure of scalar, vector, and second‐order tensor fields provides an important mathematical basis for data analysis and visualization. In this paper, we extend this framework towards higher‐order tensors. First, we establish formal uniqueness properties for a geometrically constrained tensor decomposition. This allows us to define and visualize topological structures in symmetric tensor fields of orders three and four. We clarify that in 2D, degeneracies occur at isolated points, regardless of tensor order. However, for orders higher than two, they are no longer equivalent to isotropic tensors, and their fractional Poincaré index prevents us from deriving continuous vector fields from the tensor decomposition. Instead, sorting the terms by magnitude leads to a new type of feature, lines along which the resulting vector fields are discontinuous. We propose algorithms to extract these features and present results on higher‐order derivatives and higher‐order structure tensors.     

Shape Matching via Quotient Spaces

We introduce a novel method for non‐rigid shape matching, designed to address the symmetric ambiguity problem present when matching shapes with intrinsic symmetries. Unlike the majority of existing methods which try to overcome this ambiguity by sampling a set of landmark correspondences, we address this problem directly by performing shape matching in an appropriate quotient space, where the symmetry has been identified and factored out. This allows us to both simplify the shape matching problem by matching between subspaces, and to return multiple solutions with equally good dense correspondences. Remarkably, both symmetry detection and shape matching are done without establishing any landmark correspondences between either points or parts of the shapes. This allows us to avoid an expensive combinatorial search present in most intrinsic symmetry detection and shape matching methods. We compare our technique with state‐of‐the‐art methods and show that superior performance can be achieved both when the symmetry on each shape is known and when it needs to be estimated.