Extracting 3D mesh skeletons using antipodal points locations

Finding the skeleton of a 3D mesh is an essential task for many applications such as mesh animation, tracking, and 3D registeration. In recent years, new technologies in computer vision such as Microsoft Kinect have proven that a mesh skeleton can be useful such as in the case of human machine interactions. To calculate the 3D mesh skeleton, the mesh properties such as topology and its components relations are utilized. In this paper, we propose the usage of a novel algorithm that can efficiently calculate a vertex antipodal point. A vertex antipodal point is the diametrically opposite point that belongs to the same mesh. The set of centers of the connecting lines between each vertex and its antipodal point represents the 3D mesh desired skeleton. Post processing is completed for smoothing and fitting centers into optimized skeleton parts. The algorithm is tested on different classes of 3D objects and produced efficient results that are comparable with the literature. The algorithm has the advantages of producing high quality skeletons as it preserves details. This is suitable for applications where the mesh skeleton mapping is required to be kept as much as possible.

Towards a parameterless 3D mesh segmentation

This paper proposes a novel technique for 3D mesh segmentation using multiple 2D pose footprints. Such problem has been targeted many times in the literature, but still requires further development especially in the area of automation. The proposed algorithm applies cognition theory and provides a generic technique to form a 3D bounding contour from a seed vertex on the 3D mesh. Forming the cutlines is done in both 2D and 3D spaces to enrich the available information for the search processes. The main advantage of this technique is the possibility to operate without any object-dependent parameters. The parameters that can be used will only be related to the used cognition theory and the seeds suggestion, which is another advantage as the algorithm can be generic to more than one theory of segmentation or to different criterion. The results are competitive against other algorithms, which use object-dependent or tuning parameters. This plus the autonomy and generality features, provides an efficient and usable approach for segmenting 3D meshes and at the same time to reduce the computation load.

Matrix-based pairwise key establishment in wireless mesh networks using deployment knowledge

Due to the nature of wireless transmission, communication in wireless mesh networks (WMNs) is vulnerable to many adversarial activities including eavesdropping. Pairwise key establishment is one of the fundamental issues in securing WMNs. This paper presents a new matrix-based pairwise key establishment scheme for mesh clients. Our design is motivated by the fact that in WMNs, mesh routers are more powerful than mesh clients, both in computation and communication. By exploiting this heterogeneity, expensive operations can be delegated to mesh routers, which help alleviate the overhead of mesh clients during key establishment. The new scheme possesses two desirable features: (1) Neighbor mesh clients can directly establish pairwise keys; and (2) Communication and storage costs at mesh clients are significantly reduced.

Towards parameter-less 3D mesh segmentation

This thesis focuses on the 3D mesh segmentation process. The research demonstrated how the process can be done in a parameterless approach which allows full automation with accurate results. Applications of this research include, but not limited to, 3D search engines, 3D character animation, robotics environment recognition, and augmented reality.

Matrix-based pairwise key establishment with pre and post deployment knowledge for wireless mesh networks

The nature of wireless transmission leads to vulnerabilities to many malicious activities, and communication in wireless mesh networks (WMNs) must be protected by proper security measures. This paper focuses on symmetric pair wise key establishment and presents a new matrix-based pair wise key establishment scheme for mesh clients. In WMNs, mesh routers are much more powerful than mesh clients, both in communication and computation. By taking advantage of this heterogeneity, our new scheme delegates energy-consuming operations to mesh routers when establishing pair wise keys for mesh clients. Additionally, neighbor mesh clients in our scheme can directly establish pair wise keys with significantly reduced communication and storage costs, due to the use of both pre and post deployment knowledge.

Polynomial based key predistribution scheme in wireless mesh networks

Wireless mesh networks (WMNs) have the ability to integrate with other networks while providing a fast and cost-saving deployment. The network security is one of important challenge problems in this kind of networks. This paper is focused on key management between mesh and sensor networks. We propose an efficient key pre-distribution scheme based on two polynomials in wireless mesh networks by employing the nature of heterogeneity. Our scheme realizes the property of bloom filters, i.e., neighbor nodes can discover their shared keys but have no knowledge on the different keys possessed by the other node, without the probability of false positive. The analysis presented in this paper shows that our scheme has the ability to establish three different security level keys and achieves the property of self adaptive security for sensor networks with acceptable computation and communication consumption.

Sustainability analysis and resource management for wireless mesh networks with renewable energy supplies

 There is a growing interest in the use of renewable energy sources to power wireless networks in order to mitigate the detrimental effects of conventional energy production or to enable deployment in off-grid locations. However, renewable energy sources, such as solar and wind, are by nature unstable in their availability and capacity. The dynamics of energy supply hence impose new challenges for network planning and resource management. In this paper, the sustainable performance of a wireless mesh network powered by renewable energy sources is studied. To address the intermittently available capacity of the energy supply, adaptive resource management and admission control schemes are proposed. Specifically, the goal is to maximize the energy sustainability of the network, or equivalently, to minimize the failure probability that the mesh access points (APs) deplete their energy and go out of service due to the unreliable energy supply. To this end, the energy buffer of a mesh AP is modeled as a G/G/1(/N) queue with arbitrary patterns of energy charging and discharging. Diffusion approximation is applied to analyze the transient evolution of the queue length and the energy depletion duration. Based on the analysis, an adaptive resource management scheme is proposed to balance traffic loads across the mesh network according to the energy adequacy at different mesh APs. A distributed admission control strategy to guarantee high resource utilization and to improve energy sustainability is presented. By considering the first and second order statistics of the energy charging and discharging processes at each mesh AP, it is demonstrated that the proposed schemes outperform some existing state-of-the-art solutions.

Formative feedback through summative tutorial-based assessments: the relationship to student performance

This paper investigates the effectiveness (measured using assignment and examination performance) of an assessment design incorporating formative feedback through summative tutorial-based assessments to improve student performance, in a second-year Finance course at an Australian university. Data was collected for students who were enrolled in an undergraduate Finance course and analyzed to ascertain performance improvements. The results indicate that there is a relationship between formative feedback through the use of summative tutorial-based assessments and student performance. Our empirical evidence enriches the extant literature surrounding the effectiveness of formative feedback through summative tutorial-based assessments and fosters an interest in assessment designs that provide formative feedback.

A cross-layer key establishment scheme in wireless mesh networks

Cryptographic keys are necessary to secure communications among mesh clients in wireless mesh networks. Traditional key establishment schemes are implemented at higher layers, and the security of most such designs relies on the complexity of computational problems. Extracting cryptographic keys at the physical layer is a promising approach with information-theoretical security. But due to the nature of communications at the physical layer, none of the existing designs supports key establishment if communicating parties are out of each other's radio range, and all schemes are insecure against man-in-the-middle attacks. This paper presents a cross-layer key establishment scheme where the established key is determined by two partial keys: one extracted at the physical layer and the other generated at higher layers. The analysis shows that the proposed cross-layer key establishment scheme not only eliminates the aforementioned shortcomings of key establishment at each layer but also provides a flexible solution to the key generation rate problem. © 2014 Springer International Publishing Switzerland.

A new design concept for knitted external vein-graft support mesh

Autologous vein-graft failure significantly limits the long-term efficacy of coronary artery bypass procedures. The major cause behind this complication is biomechanical mismatch between the vein and coronary artery. The implanted vein experiences a sudden increase (10-12 fold) in luminal pressures. The resulting vein over-distension or 'ballooning' initiates wall thickening phenomenon and ultimate occlusion. Therefore, a primary goal in improving the longevity of a coronary bypass procedure is to inhibit vein over-distension using mechanical constriction. The idea of using an external vein-graft support mesh has demonstrated sustained benefits and wide acceptance in experimental studies. Nitinol based knitted structures have offered more promising mechanical features than other mesh designs owing to their unique loosely looped construction. However, the conventional plain knit construction still exhibits limitations (radial compliance, deployment ease, flexibility, and bending stresses) which limit this design from proving its real clinical advantage. The new knitted mesh design presented in this study is based on the concept of composite knitting utilising high modulus (nitinol and polyester) and low modulus (polyurethane) material components. The experimental comparison of the new design with a plain knit design demonstrated significant improvement in biomechanical (compliance, flexibility, extensibility, viscoelasticity) and procedural (deployment limit) parameters. The results are indicative of the promising role of new mesh in restoring the lost compliance and pulsatility of vein-graft at high arterial pressures. This way it can assist in controlled vein-graft remodelling and stepwise restoration of vein mechanical homoeostasis. Also, improvement in deployment limit parameter offers more flexibility for a surgeon to use a wide range of vein diameters, which may otherwise be rendered unusable for a plain knit mesh.