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Theses/Dissertations

Electronic Theses and Dissertations

2003

Computer Science.

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Authorization-Enhanced Security Framework For Ogsa Support., Haiyan. Cheng Jan 2003

Authorization-Enhanced Security Framework For Ogsa Support., Haiyan. Cheng

Electronic Theses and Dissertations

Security plays an important role for a large distributed system in an open community. Without enough knowledge about the user, it is hard to make access decision to the local resources. Current Public Key Infrastructure (PKI) uses a trusted third party, called Certificate Authority (CA), to check the identity of the users. The assumption of PKI is that every entity trusts CA absolutely and equally. This is also a weakness of PKI. The security problem in a Single-Sign-On (SSO) environment is more difficult to manage. Most of the current SSO security approach relies heavily on the pre-established trust relationship. This ...


User Authentication In Distributed Computing Using Proactive Two-Party Signatures., Arshad Ahmed. Shaikh Jan 2003

User Authentication In Distributed Computing Using Proactive Two-Party Signatures., Arshad Ahmed. Shaikh

Electronic Theses and Dissertations

To address the challenges of user authentication in distributed systems, many protocols have been proposed. Among them is the Proactive Two-party Signatures Scheme (P2SS). P2SS has not so far been investigated in detail. Using P2SS, I have developed a system, called Proactive User-authentication in a Distributed Environment (PUDE) in which two parties (the client and server) use a 2-part signature algorithm, based on standard (one part) RSA algorithm. In this scheme the client and the server jointly produce the signatures. If the password of the user is compromised, the system can recover by changing the share of the private key ...


Correctness Of Distributed Systems With Middleware., Hanmei. Cui Jan 2003

Correctness Of Distributed Systems With Middleware., Hanmei. Cui

Electronic Theses and Dissertations

Here we present a formal verification technique for the correctness of the design models of the component-based distributed applications where the inter-process communications are realized via general middleware layers. We give a suitable extension of UML statechart diagrams. With this extension, the components and the communications among them in a middleware-based distributed application can be clearly expressed, and the software developers can actually view the middleware as a black box. We assume that the abstract behavior of the distributed application is given in such notations using any UML tool capable of saving the design in the standard XMI format. Two ...


Depth Recovery Using A Plenoptic Camera., Mohamed. Amtoun Jan 2003

Depth Recovery Using A Plenoptic Camera., Mohamed. Amtoun

Electronic Theses and Dissertations

Depth recovery is a central problem in Computer Vision. Stereopsis is one of the most extensively investigated techniques amidst the approaches addressing it. Though sufficiently accurate, stereopsis is highly dependent on the success of point correspondence, an ill-posed problem that is known to suffer from a number of underlying difficulties. Single-lens stereo systems emerged recently as an effective means to thwart some of the problems of correspondence. The plenoptic camera in particular, has a special image formation geometry that claims to resolve the correspondence ambiguities and simplify depth recovery. However, to our knowledge, prior to this work, no study has ...


Bottleneck Bandwidth Measurement Using Path Algorithm., Jun. Wei Jan 2003

Bottleneck Bandwidth Measurement Using Path Algorithm., Jun. Wei

Electronic Theses and Dissertations

Network bandwidth is an important resource in the Internet. As greater numbers of people and companies implement their businesses using the Internet, the measurement of network bandwidth, especially the bottleneck-link bandwidth, becomes a critical and challenging issue. To improve the practicability, accuracy and performance of existing network-bandwidth measurement algorithms, such as PathChar, Bprobe and Cartouche algorithm, we have developed a new method: PATH (PAcket-Train with Header) algorithm. PATH is the combination of single-packet and packet-pair algorithms. It is a sender-based algorithm that is straightforward to implement in the Internet. To verify and improve upon the PATH algorithm, we have developed ...


A Categorical Data Clustering Approach With Expectation Maximization And K-Nearest Neighbour., Yu. Liu Jan 2003

A Categorical Data Clustering Approach With Expectation Maximization And K-Nearest Neighbour., Yu. Liu

Electronic Theses and Dissertations

In data mining, clustering analysis is an important research area. The goal of clustering is to group the objects in a data set into meaningful subclasses. Many algorithms have been designed for numerical data clustering and categorical data clustering respectively. However, very few people paid attention to the clustering problem of mixed-type data set which includes data objects that are of both numerical and categorical attributes. This thesis proposes an approach to the solution of this problem. The method is called CCEM-KNN which stands for Categorical data Clustering approach with Expectation Maximization and K-Nearest Neighbour. First, we apply a categorical ...


Variation Of Bloom Filters Applied In Distributed Query Optimization., Yue (Amber). Zhang Jan 2003

Variation Of Bloom Filters Applied In Distributed Query Optimization., Yue (Amber). Zhang

Electronic Theses and Dissertations

Distributed query processing is important for Distributed Database Systems. Through the past years, the research focus in distributed query processing has been on how to realize join operations with different operators such as semi-join and Bloom Filter. Experiments show that using bloom filters, the hash-semijoin, almost always does better than semi-join for the query processing. However as long as you use bloom filter, you cannot avoid collisions. So in order to get the cheaper processing, some of the past work uses two or more bloom filters to do the hash-semijoin. However several factors still affect the cost and optimization result ...


Wavelet-Based Multiresolution Method For Surface Reconstruction., Shobha. Iyer Jan 2003

Wavelet-Based Multiresolution Method For Surface Reconstruction., Shobha. Iyer

Electronic Theses and Dissertations

One of the areas of research that has achieved tremendous importance over the recent past is the problem of reconstructing a surface of a solid polyhedral object. This problem has found vast applications in human anatomy, automobile design, medical imaging and therapy, etc. One of the foremost techniques used to solve this problem included constructing the solid from a series of slices parallel to each other. This slice data was obtained by taking horizontal cross-sections passing through the interior of the solid like slicing an apple through a number of thin horizontal planes. The piecewise linear interpolation technique was one ...


A Heuristic For Wdm Path Protection., Min. Hou Jan 2003

A Heuristic For Wdm Path Protection., Min. Hou

Electronic Theses and Dissertations

Optical fibers and Wavelength Division Multiplexing (WDM) are being researched as well as commercially deployed as technologies that can satisfy the bandwidth requirements of the Internet today and the foreseeable future. Since optical resources are expensive, we need to develop network design mechanisms, which can achieve an efficient utilization of network resources in a reasonable computational time. In WDM networks, the failure of a single fiber link may cause very large data loss if the traffic is not rerouted quickly. Therefore, the survivability of optical connections has become a very important issue for WDM network design. In this thesis, we ...


A Hybrid Load Balancing Algorithm For Coarse-Grained Applications., Xinyu. Gan Jan 2003

A Hybrid Load Balancing Algorithm For Coarse-Grained Applications., Xinyu. Gan

Electronic Theses and Dissertations

A non-preemptive hybrid load balancing algorithm is proposed for heterogeneous distributed computing environment, since no single load balancing algorithm works well for all kinds of applications and environments. The agents' computing capabilities may also change during runtime because of the background load. This algorithm makes use of the idea of several sub-algorithms. The hybrid model initially classifies the computers and jobs into different groups. Two priority queues are maintained at each worker to record the processes' estimated computing time and the real time. Based on historical experiences, a centralized scheduler can dynamically change the parameters in order to improve the ...


Computing The Minimum Perimeter Triangle Enclosing A Convex Polygon: Theory And Implementation., Anna Valentinovna. Medvedeva Jan 2003

Computing The Minimum Perimeter Triangle Enclosing A Convex Polygon: Theory And Implementation., Anna Valentinovna. Medvedeva

Electronic Theses and Dissertations

Geometric optimization, an important field of computational geometry, finds the best possible solution to a computational problem that involves geometric objects. An attractive fundamental problem in this area is one of approximating a convex n-gon with a simpler convex k-gon, where k < n, and the area or the perimeter of the approximate object is minimized. This problem arises in a wide range of applications, such as geographic information systems (GIS), spatial databases, pattern recognition, and computer graphics, to name but a few. The approximation of convex polygons with their respective enclosing triangles is a particularly interesting problem; however, finding an optimal linear time solution for computing the minimum perimeter triangle enclosing a convex polygon was a long-standing open problem, which turned out to be more difficult than determining an enclosing triangle of minimal area. In this thesis, we suggest some theoretical and practical justifications for the linear time complexity of a recently proposed optimal solution and provide an efficient and robust implementation of that solution. (Abstract shortened by UMI.) Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .M43. Source: Masters Abstracts International, Volume: 42-02, page: 0618. Adviser: Asish Mukhopadhyay. Thesis (M.Sc.)--University of Windsor (Canada), 2003.


Integrated Channel Assignment And Power Control In Wireless Mobile Networks Using Evolutionary Strategy., Geetali Dutta. Vidyarthi Jan 2003

Integrated Channel Assignment And Power Control In Wireless Mobile Networks Using Evolutionary Strategy., Geetali Dutta. Vidyarthi

Electronic Theses and Dissertations

In wireless mobile communication system, radio spectrum is a limited resource. However, efficient use of available channels has been shown to improve the system capacity. The role of a channel assignment scheme is to allocate channels to cells or mobiles in such a way as to minimize call blocking or call dropping probabilities, and also to maximize the quality of service. Channel assignment is known to be an NP-hard optimization problem. In this thesis, we have developed an Evolutionary Strategy (ES) which optimizes the channel assignment. The proposed ES approach uses an efficient problem representation as well as an appropriate ...


On Finding A Maximum Empty Rectangle Of Arbitrary Orientation: Theory And Implementation., Hongtao. Zhang Jan 2003

On Finding A Maximum Empty Rectangle Of Arbitrary Orientation: Theory And Implementation., Hongtao. Zhang

Electronic Theses and Dissertations

Geometric optimization, which has emerged as an important line of research within the field of Computational Geometry, is concerned with computational problems in which the objective is to find the best of all possible solutions. More formally, it is used to find an optimal solution with the minimum (or maximum) value in a search space which contains all the possible solutions. In this thesis, we begin with a very brief survey of the field of geometric optimization, focussing on the some of the important techniques that have been used to solve a variety of problems in this area. Then, we ...


An Efficient Shared Path Protection Based On Quality Of Service In Wdm Networks., Zhongwei. Hu Jan 2003

An Efficient Shared Path Protection Based On Quality Of Service In Wdm Networks., Zhongwei. Hu

Electronic Theses and Dissertations

With the explosive growth of the Internet in the past decade, survivability and high-bandwidth have become the most critical characteristics for networks. Determining the most efficient and reliable network configuration is a significant challenge in current optical network research. WDM (Wavelength Division Multiplexing) has become one of the most important features of optical networks because of its highly improved utilization of network capacity. The design of WDM networks can be analyzed from two perspectives: Network Design, and Routing & Wavelength Assignment (RWA). Network design includes physical topology design and configuration design. Routing and Wavelength Assignment (RWA) involves mapping lightpaths into the ...


Compression And Decompression Of Quadrilateral Meshes., Quanbin. Jing Jan 2003

Compression And Decompression Of Quadrilateral Meshes., Quanbin. Jing

Electronic Theses and Dissertations

3D Quad mesh plays an important role in various engineering fields. Due to improved design and model acquisition tools, as well as the need for higher accuracy, the number and complexity of these models are growing more rapidly than network bandwidth. Therefore, reducing the amount of transmission by compressing the 3D quad model is imperative. A mesh may be represented by its vertex data and its connectivity. Vertex data comprise coordinates of all the vertices and optionally the vertex colors and the associated normal vectors and textures. Connectivity captures the incidence relation between the quads of the mesh and their ...


Optimal Logical Topology Design With Wdm Path Protection., Hong. Guan Jan 2003

Optimal Logical Topology Design With Wdm Path Protection., Hong. Guan

Electronic Theses and Dissertations

Bandwidth usage on the Internet is doubling every six to twelve months according to some research result. The emergence of WDM technology provides more bandwidth and cost effective solution to upgrade the speed of data transmission. The future trend in backbone network design is to gradually migrate to IP over WDM network. For this next generation optical network, there is one very important issue---design of robust networks that can survive faults. Protection is a common lower layer mechanism against common faults in optical network, such as fiber cuts. There are two protection mechanisms, dedicated path protection or shared path protection ...