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Triangle meshes can provide an effective geometric representation of images. Although many mesh generation methods have been proposed to date, many of them do not explicitly take image discontinuities into consideration. In this thesis, a new mesh model for images, which explicitly represents discontinuities (i.e., image edges), is proposed along with two corresponding mesh-generation methods that determine the mesh-model parameters for a given input image. The mesh model is based on constrained Delaunay triangulations (DTs), where the constrained edges correspond to image edges. One of the proposed methods is named explicitly-represented discontinuities-with error diffusion (ERDED), and is fast and easy to implement. In the ERDED method, the error diffusion (ED) scheme is employed to select a subset of sample points that are not on the constrained edges. The other proposed method is called ERDGPI. In the ERDGPI method, a constrained DT is first constructed with a set of prespecified constrained edges. Then, the greedy point insertion (GPI) scheme is employed to insert one point into the constrained DT in each iteration until a certain number of points is reached. The ERDED and ERDGPI methods involve several parameters which must be provided as input. These parameters can affect the quality of the resulting image approximations, and are discussed in detail. We also evaluate the performance of our proposed ERDED and ERDGPI methods by comparing them with the highly effective ED and GPI schemes. Our proposed methods are demonstrated to be capable of producing image approximations of higher quality both in terms of PSNR and subjective quality than those generated by other schemes. For example, the reconstructed images produced by the proposed ERDED method are often about 3.77 dB higher in PSNR than those produced by the ED scheme, and our proposed ERDGPI scheme produces image approximations of about 1.08 dB higher PSNR than those generated by the GPI approach. / Graduate

In recent years, wireless mesh networking has attracted a growing interest due to its inherent flexibility, scalability, and reliability. The IEEE 802.16 standard, commonly known as worldwide interoperability for microwave access (WiMAX), is the latest technology that enables broadband wireless access over long distances. WiMAX, which emerges as a wireless alternative to cable and digital subscriber line (DSL), is an ideal candidate to serve as the infrastructure for large scale wireless mesh networks. This thesis focuses on the quality of service (QoS) provisioning techniques in WiMAX-based metropolitan area mesh networks. We study the connection admission control (CAC) and routing issues in the design and operation of wireless multihop mesh networks. We propose a joint CAC and routing scheme for multiple service classes with the objective to maximize the overall revenue from all carried connections. Connection-level QoS constraints such as handoff connection dropping probability can be guaranteed within a threshold. Multiple service classes can be prioritized by imposing different reward rates. We apply optimization techniques to obtain the optimal CAC policies. The optimality criterion is the long-run average reward. We demonstrate that the proposed scheme can the maximum revenue obtainable by the system under QoS constraints. We show that the optimal joint policy is a randomized policy, i.e., connections are admitted to the system with some probabilities when the system is in certain states. Simulation results illustrate that the proposed scheme meets our design goals and outperforms the existing scheme.

Meshes and hypercubes are two most important communication and computation structures used in parallel computing. Network embedding problems for meshes and hypercubes on traditional network architectures have been intensively studied during the past years. With the emergence of new network architectures, the traditional network embedding results are not enough to solve the new requirements. The main objective of this thesis is to design efficient network embedding schemes for realizing meshes and hypercubes on a group of future network architectures. This thesis is organized into two parts. The first part focuses on embedding meshes/tori on a group of double-loop networks by evaluating the traditional embedding metrics, since double-loop networks have been intensively studied and proven to have many desirable properties for future network architecture. We propose a novel tessellation approach to partition the geometric plane of double-loop networks into a set of parallelogram tiles, called P-shape. Based on the characteristics of P-shape, we design a simple embedding scheme, namely P-shape embedding, that embeds arbitrary-shape meshes and tori on double-loop networks in a systematic way. A main merit of P-shape embedding is that a large fraction of embedded mesh/torus edges have edge dilation 1, resulting in a low average dilation. These are the first results, to our knowledge, on embedding meshes and tori on general doubleloop networks which is of great significance due to the popularity of these architectures. Our P-shape construction bridges between regular graphs and double-loop networks, and provides a powerful tool for studying the topological properties of double-loop networks. In the second part, we study efficient embedding schemes for realizing hypercubes on a group of array-basedWDMoptical networks by analyzing the new embedding metric of wavelength requirement, as WDM optical networking is becoming a promising technology for deployment in many applications in advanced telecommunication and parallel computing. We first design routing and wavelength assignments of both bidirectional and unidirectional hypercubes on WDM optical linear arrays, rings, meshes and tori with the consideration of communication directions. For each case, we identify a lower bound on the number of wavelengths required, and design the embedding scheme and wavelength assignment algorithm that uses a provably near-optimal number of wavelengths. To further reduce the wavelength requirement, we extend the results to WDM ring networks with additional links, namely WDM chordal rings. Based on our proposed embedding schemes, we provide the analysis of chord length with optimal number of wavelengths to realize hypercubes on 3-degree and 4-degree WDM chordal rings. Furthermore, we propose an embedding scheme for realizing dimensional hypercubes on WDM optical arrays by considering the hypercubes dimension by dimension, called lattice embedding, instead of embedding hypercubes with all dimensions. Based on lattice embedding, the number of wavelengths required to realize dimensional hypercube on WDM arrays can been significantly reduced compared to the previous results. By our embedding schemes, many communications and computations, originally designed based on hypercubes, can be directly implemented in WDM optical networks, and the wavelength requirements can be easily derived using our obtained results. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1345349 / Thesis (Ph.D.) - University of Adelaide, School of Computer Science, 2008

Network security is an important domain in the field of computer engineering. Sensitive information flowing across computer networks is vulnerable to potential threats, therefore it is important to ensure their security. Wireless Mesh Networks (WMNs) are self-organized networks deployed in small proximity which have an wireless ad-hoc mesh topology. While they are cost effective and easy to deploy, they are extremely vulnerable to network intrusions due to no central switch or router. However, they can be secured using cryptographic techniques, firewalls or Demilitarized Zones (DMZs). Intrusion Detection Systems (IDSs) are used as a secondary line-of-defence in computer networks from possible intrusions. This thesis proposes a framework for a Hybrid Intrusion Detection System (HIDS) for WMN. / Graduate

With wireless signals, it is possible to send all kind of data through a communication system. Many companies today having problems implementing wireless communication system because of big areas and many obstacles that blocks the wireless signals. Recent releases of mesh network standards that has the main objective to provide a network over a large area. Toyota Material Handling Europe (TMHE) that develops and produce trucks is one company that wants to use this new network topology to get to the next level of communication. TMHE is developing a new communication system between their trucks and the goal is to be independent of Wi-Fi and fixed structures in an industry. The aim is to establish communication through Bluetooth and create a mesh network between the trucks at a site. This kind of communication can create many new possibilities for new features, which can make the daily work easier. The problem with obstacles and interferences is still a problem and TMHE created a thesis to research Bluetooth mesh networks to see if this kind of implementation is suitable for the environments that exists in an industry. This thesis research the architecture of a Bluetooth mesh network and different setups of a network and tests how it stands in an industry with many different surrounding.

>Magister Scientiae - MSc / This thesis deals with the design of a business model for rural telephony based on a wireless mesh network for a rural community, the Mankosi community, located in the Eastern Cape Province of South Africa. Its aim is to understand the social, economic and technical issues that are involved in the adoption of information and communication technologies for development and how they relates to trust in e-services. Externally funded projects tend to be expensive and are often unsustainable once the external funding ceases. The cost of a mesh network (once implemented) is almost negligible, apart from its maintenance. The pillars of the project are sustainability and community ownership, and the aim was to design the wireless mesh network, provide telephony service to the community and use solar power to charge mobile phones. The community leaders of Mankosi indicated that they do not want the service to be completely free, but would charge a small fee for each call in order to generate the funds needed for the maintenance of the system. In order to do so, a prototype billing system was configured and adapted to the needs and expectations of the community. The principles and steps of soft systems methodology were used to manage the research process of this case study. This methodology was a powerful tool to carry out the research and address the research problem in a participative way with the stakeholders. The participatory design process used in the design phase of the project had the added advantage that the community understood the purpose of the network, and since they contributed to its design, they felt that they owned it and could trust its billing system. A further benefit was that a core group of participants were committed to the project and felt that the overall quality of community members' lives would be improved by it and similar projects. The process contributed to the personal development of the participants by giving the community a voice and sense of power – the ability to change things – and it vastly expanded community members’ vision of what they are capable of. It was found that the current means of communication, i.e. using mobile phones, is expensive for local users in relation to their average income. The proposed billing system – designed with the help of the community – will be trusted by the community and provide Mankosi with a low-cost communication system by making use of the existing experimental mesh network. The community will be able to sustain their network with the income generated. The network will in future provide access to the Internet and will be able to handle breakout calls to external networks.

>Magister Scientiae - MSc / This thesis validates that packet aggregation is a viable technique to increase call capacity for Voice over Internet Protocol over wireless mesh networks. Wireless mesh networks are attractive ways to provide voice services to rural communities. Due to the ad-hoc routing nature of mesh networks, packet loss and delay can reduce voice quality. Even on non-mesh networks, voice quality is reduced by high overhead, associated with the transmission of multiple small packets. Packet aggregation techniques are proven to increase VoIP performance and thus can be deployed in wireless mesh networks. Kernel level packet aggregation was initially implemented and tested on a small mesh network of PCs running Linux, and standard baseline vs. aggregation tests were conducted with a realistic voice traffic profile in hop-to-hop mode. Modifications of the kernel were then transferred to either end of a nine node 'mesh potato' network and those tests were conducted with only the end nodes modified to perform aggregation duties. Packet aggregation increased call capacity expectedly, while quality of service was maintained in both instances, and hop-to-hop aggregation outperformed the end-to-end configuration 4:1. However, implementing hop-to-hop in a scalable fashion is prohibitive, due to the extensive kernel level debugging that must be done to achieve the call capacity increase. Therefore, end-to-end call capacity increase is an acceptable compromise for eventual scalable deployment of voice over wireless mesh networks.

In this dissertation, we study the triangular mesh simplification process, describing its main characteristics. We discuss an adaptation for triangular meshes of a mesh simplification process based on Voronoi coverage proposed by Peixoto [2002]. Moreover, we use Fast Marching Method as a distance function over the mesh and some different strategies for simplified mesh vertices selection, like curvature based selection. The simplification process is done by constructing an intrinsic Voronoi diagram over the original mesh. We discuss some necessary conditions to obtain a mesh, as Voronoi dual, without any singularities and topologically equivalent to the original mesh. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta dissertação, estudaremos o processo de simplificaçãoo de malhas triangulares, caracterizando-o com suas particularidades. Discutiremos uma adaptação para superfícies triangulares do método de simplificação baseado em uma cobertura de Voronoi proposto por Peixoto [2002]. Além disso, utilizaremos o método Fast Marching como uma nova métrica e diferentes estratégias para seleção de vértices da malha simplificada, como a seleção por curvatura. A simplificação ocorre a partir de um diagrama de Voronoi intrínseco à malha. Discutiremos algumas condições necessárias para que a partir do dual desse diagrama, obtenha-se uma malha sem singularidades que seja equivalente a malha original.

Orientadores: Rogerio de Fraga, Paulo Cesar Rodrigues Palma / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-12T22:24:52Z (GMT). No. of bitstreams: 1 Cardia_FishilerPimentelZitenfeld_M.pdf: 1370656 bytes, checksum: 9c1061423f4725bab06c637f1e6c0958 (MD5) Previous issue date: 2009 / Resumo: A crescente utilização de telas de polipropileno em cirurgia pélvica reconstrutiva levou ao aparecimento de complicações inerentes ao uso dos materiais sintéticos, tais como retração, exposição e infecção. Com o objetivo de avaliar a retração de telas de polipropileno de media gramatura e melhorar a incorporação da mesma através de orifícios de 5 mm de diâmetro, realizamos um estudo experimental "in vivo". Método: No presente estudo, avalia a morfologia e a densidade volumétrica das fibras de colágeno em malhas com e sem orifícios padronizados, bem como; a retração das mesmas, por meio de mensuração radiográfica e direta da tela. A amostra consistiu de 14 ratas fêmeas da raça Wistar, que foram sacrificadas 90 dias após o implante. O abdômen foi ressecado e radiografado antes de ser preparado o estudo histológico e estereológico. A distribuição do colágeno foi avaliada por estereologia nos três compartimentos: pele, fascia de Colles e na região do implante da Tela entre a fascia de Colles e a aponeurose dos músculos retos abdominais. Resultados: Não houve retração das telas de polipropileno nas aferições radiográficas e medidas diretas. A estereologia evidenciou deposição de fibras de colágenos organizadas nos orifícios. Ao contrário nas telas sem orifícios, a deposição de colágeno foi maior e desorganizada, com cistos de inclusão. Outro dado relevante foi que a estrutura das fibras de colágeno apresentou-se morfologicamente normal nos animais de tela com orifício, e houve uma maior proximidade entre a pele e a musculatura no local do orifício. Conclusões: A análise histológica revelou menor reação inflamatória nas telas com macro orifícios. A avaliação estereológica da densidade volumétrica das fibras de colágeno nas telas com e sem orifícios, permitiu observar que os macro orifícios agiram como fator facilitador da integração do enxerto e que poderá representar implicações na parte clinica médica. Palavras chaves: Polipropileno; Telas cirúrgicas / Abstract: The meshes in reconstructive pelvic surgery have led to complications inherent to the use of synthetic materials, such as retraction, exposure and infection. In order to improve mesh integration we created standardized orifices, 5 mm in diameter of monofilament polypropylene mesh and compared local tissue reaction with regular meshes in an animal study. Method: We evaluated the morphology and volumetric density of collagen fibers in meshes with and without standardized orifices, as well as its retraction through radiographic and direct measurement of the meshes. The sample consisted of 15 female Wistar rats, which were sacrificed 90 days after the implant. The abdominal wall was removed and x-ray was taked before its preparation for histological and stereological study (estimate the density of an element of a homogeneous area). The volumetric density of the collagen fibers was calculated by stereological tool in three compartments: skin, Colles' fascia and mesh, the latter located between the Colles' fascia and the aponeurosis of the rectus abdominalis muscles. Results: There was no retraction of the polypropylene meshes. The histological and stereological analysis disclosed organized collagen fiber deposition in the orifices and less inflammatory reaction than the control meshes with no orifices. Conclusions: There was no mesh retraction in both groups. The histological and stereological results suggest that the standardized orifices facilitated tissue integration and may have clinical application. Keywords: Polypropylene; Surgical meshes / Mestrado / Cirurgia / Mestre em Cirurgia