The accuracy of a fluid flow simulation depends not only on the numerical method used for discretizing the governing equations, but also on the distribution and topology of the mesh elements. Mesh adaptation is a technique for automatically modifying the mesh in order to improve the simulation accuracy in an attempt to reduce the manual work required for mesh generation. The conventional approach to mesh adaptation is based on a feature-based criterion that identifies the distinctive features in the flow field such as shock waves and boundary layers. Although this approach has proved to be simple and effective in many CFD applications, its implementation may require a lot of trial and error for determining the appropriate criterion in certain applications. An alternative approach to mesh adaptation is the residual-based approach in which the discretization error of the fluid flow quantities across the mesh faces is used to construct an adaptation criterion. Although this approach provides a general framework for developing robust mesh adaptation criteria, its incorporation leads to significant computational overhead. The main objective of the thesis is to present a methodology for developing an appropriate mesh adaptation criterion for fluid flow problems that offers the simplicity of a feature-based criterion and the robustness of a residual-based criterion. This methodology is demonstrated in the context of a second-order accurate cell-centred finite volume method for simulating laminar steady incompressible flows of constant property fluids. In this methodology, the error of mass and momentum flows across the faces of each control volume are estimated with a Taylor series analysis. Then these face flow errors are used to construct the desired adaptation criteria for triangular isotropic meshes and quadrilateral anisotropic meshes. The adaptation results for the lid-driven cavity flow show that the solution error on the resulting adapted meshes is 80 to 90 percent lower than that of a uniform mesh with the same number of control volumes. The advantage of the proposed mesh adaptation method is the capability to produce meshes that lead to more accurate solutions compared to those of the conventional methods with approximately the same amount of computational effort.

Heterogeneous wireless networks will be dominant in the next-generation wireless networks with the integration of various wireless access networks. Wireless mesh networks will become to a key technology as an economically viable solution for wide deployment of high speed, scalable and ubiquitous wireless Internet services. In this thesis, we consider an interworking architecture of wireless mesh backbone and propose an effective vertical handoff scheme between 802.11 and 802.16 wireless access networks. The proposed vertical handoff scheme aims at reducing handoff signaling overhead on the wireless backbone and providing a low handoff delay to mobile nodes. The handoff signaling procedure in different scenarios is discussed. Together with call admission control, the vertical handoff scheme directs a new call request in the 802.11 network to the 802.16 network, if the admission of the new call in the 802.11 network can degrade quality-of-service (QoS) of the existing real-time traffic flows. Simulation results demonstrate the performance of the handoff scheme with respect to signaling cost, handoff delay, and QoS support.

The use of wireless radio technology is well established for narrowband access systems, but its use for broadband access is relatively new. Wireless mesh architecture is a first step towards providing high-bandwidth wireless network coverage, spectral efficiency, and economic advantage. However, the widespread adoption and use of Wireless Mesh Networks (WMN) as a backbone for large wireless access networks and for last-mile subscriber access is heavily dependent on the technology’s ease of deployment. In order for WMNs to be regarded as mainstream technology, it needs to gain a competitive edge compared to wireline technologies such as DSL and cable. To achieve this, a broadband wireless network must be self-configuring, self-healing and self-organizing. In this thesis, we address these challenges. First, we propose a four-stage scheme (power-up, bootstrapping, network registration, and network optimization). We develop algorithms for each of these stages, taking advantage of the inherent properties of WMNs to determine the network’s topology. The novel part of our scheme is in the de-coupling of the subscriber’s credentials from the network hardware. This is a key part of our architecture as it helps ensure quick network enrolment, management and portability. It also helps, in our opinion, make the concept of widespread deployment using commodity hardware feasible.

This thesis proposes a potential solution for future ubiquitous broadband wireless access networks, called a cellular wireless mesh network (CMESH), and investigates a number of its performance issues. A CMESH is organized in multi-radio, multi-channel, multi-rate and multi-hop radio cells. It can operate on abundant high radio frequencies, such as 5-50 GHz, and thus may satisfy the bandwidth requirements of future ubiquitous wireless applications.<p> Each CMESH cell has a single Internet-connected gateway and serves up to hundreds of mesh nodes within its coverage area. This thesis studies performance issues in a CMESH, focusing on cell capacity, expressed in terms of the max-min throughput. In addition to introducing the concept of a CMESH, this thesis makes the following contributions.<p> The first contribution is a new method for analyzing theoretical cell capacity. This new method is based on a new concept called Channel Transport Capacity (CTC), and derives new analytic expressions for capacity bounds for carrier-sense-based CMESH cells.<p> The second contribution is a new algorithm called the Maximum Channel Collision Time (MCCT) algorithm and an expression for the nominal capacity of CMESH cells. This thesis proves that the nominal cell capacity is achievable and is the exact cell capacity for small cells within the abstract models.<p> Finally, based on the MCCT algorithm, this thesis proposes a series of greedy algorithms for channel assignment and routing in CMESH cells. Simulation results show that these greedy algorithms can significantly improve the capacity of CMESH cells, compared with algorithms proposed by other researchers.

Current advancements in nuclear reactor core design are pushing reactor cores towards greater heterogeneity in an attempt to make nuclear power more sustainable in terms of fuel utilization and long-term disposal needs. These new designs are now being limited by the accuracy of the core simulators/methods. Increasing attention has been given to full core transport as the flux module in future core simulators. However, the current transport methods, due to their significant memory and computational time requirements, are not practical for whole core calculations. While most researchers are working on developing new acceleration and phase space parallelization techniques for the current fine mesh transport methods, this dissertation focuses on the development of a practical heterogeneous coarse mesh transport method. In this thesis, a heterogeneous coarse mesh transport method is extended from two to three dimensions in Cartesian geometry and new techniques are developed to reduce the strain on computational resources. The high efficiency of the method is achieved by decoupling the problem into a series of fixed source calculations in smaller sub-volume elements (e.g. coarse meshes). This decoupling lead to shifting the computation time to a priori calculations of response functions in unique sub-volumes in the system. Therefore, the method is well suited for large problems with repeated geometry such as those found in nuclear reactor cores. Even though the response functions can be generated with any available existing fine-mesh (deterministic or stochastic) code, a stochastic method was selected in this dissertation. Previous work in two dimensions used discrete polynomial expansions that are better suited for treating discrete variables found in pure deterministic transport methods. The amount of data needed to represent very heterogeneous problems accurately became quite large making the three dimensional extension impractical. The deterministic method was thus replaced by a stochastic response function generator making the transition to continuous variables fairly simple. This choice also improves the geometry handling capability of the coarse mesh method.

With the wireless mesh network in the embedded systems related applications booming in recent years, the demand of enhancing the overall end to end network traffic and ensuring a stable connection is growing. We proposed a Dynamic Multi-channel Multi-path Routing Protocol (DMMR Protocol) to decompose contending traffics over different channel, different time and different paths to enhance the end to end network traffic. Choosing channel dynamically according to the channel usage around node in the process of finding paths can avoid inter-flow and intra-flow channel competition. We tend to choose paths with less intersection nodes to reduce the probability of multiple paths are broken at same time when a single node cannot work. We can enhance end to end network traffic further by using multiple interfaces at one node. We use NS2 to test DMMR Protocol, and analyzing the overall end to end traffic when multiple connections are setting up in the network. If the network can accept a new connection, the increment of end to end traffic is same as the traffic of the new connection. In connection robust test, a single path broken will not affect other flows in same connection and the end to end traffic in the connection will recovery immediately when the broken path is repaired.

In recent years, the applications of wireless mesh network in the embedded systems have become more widely. It's an important issue that how to consume lower energy and transfer data stably based on energy considerations. The embedded systems must have the appropriate routing protocol for low power consumption and stable long-distance data transmission. In this paper, a routing protocol is proposed with sequential repair and backup routing protocol(Ad Hoc On-Demand Distance Vector Routing-Sequential Repair and Backup Routing Protocol, AODV-SRBR Protocol), that can reduce the number of transceivers and have a stable connection. In the proposed routing protocol, the node of network can create multi-route message through decoding the path information of packets. Using a complete routing information can reduce the number of route request packets efficiently. when the link is broken, the proposed protocol can repair the data transmission by sequential repair or select backup routing. In this paper, we implement the routing protocol to verify a multi-hop connection and data transfer in the general environment. The performance of AODV-SRBR and AODV is compared and simulated by NS2. The proposed routing protocol can achieve same transmission efficiency in the fewer route request packets, fewer maintance packets and fewer transmit and receive times according to the simulation result. By stable connection¡Blow power consumption and multi-hop data transfer, we expect that the proposed routing protocol on the embedded systems platform can be extended in large sensor mesh network.

An insulation technique has been developed which contains a single or combination of materials to help minimize heat loss in actual industrial applications. For the petroleum industry, insulation for deep sea piping is one of the greatest challenges which would prevent the industry from meeting the high demand for oil through exploration into deeper ocean environments. At current seafloor depths (5,000~10,000ft), pipeline insulation is essential in preventing pipeline blockage resulting from the solidification of paraffin waxes and / or hydrate formation which exist in crude oil. To maintain crude oil temperatures above the paraffin solidification point (68°C or 155°F), new and better insulation techniques are essential to minimize pipeline heat loss and maintain crude oil temperatures. Therefore, the objective of this investigation was to determine whether or not the thermal resistance of a new insulation concept, which involves IIT (Interstitial Insulation Technology) with screen wire, was greater than existing readily available commercial products through analytical modeling and experimentation. The model takes into account both conforming and nonconforming interfaces at the wire screen contacts within the interstitial space between coaxial pipes. In addition, confirmation was needed to determine whether or not laboratory testing of simulated coupons translate to thermal performance for a prototype pipe segment that fabricated with two layers of low conductivity wire-screen (stainless steel) as the interstitial insulation material. Both the inner and outer surface temperatures of the coaxial pipes were measured in order to evaluate the effective thermal conductivity and thermal diffusivity of the insulation concept. The predicted results from the model compared very favorably with the experimental results, confirming both the trends and magnitudes of the experimental data. In other words, whether the reduction in heat transfer observed for small laboratory samples was realistic for application to a pipeline configuration. This effort involved both analytical modeling for all thermal resistances and experimental test runs for validation of the analytical model. Finally, it was a goal of this investigation to develop a simplified model for a multilayer composite structure which will include radiation heat transfer exchange among the layers that constitute the insulation. With the developed model, feasibility and performance characteristics of the insulation concept were predicted. The thermal predictions have demonstrated the thermal competitiveness of the interstitial insulation technology.

In this dissertation, the design and analyses of an extremely scalable distributed multicomputer architecture, using optical interconnects, that has the potential to deliver in the order of petaFLOP performance is presented in detail. The design takes advantage of optical technologies, harnessing the features inherent in optics, to produce a 3D stack that implements efficiently a large, fully connected system of nodes forming a true 3D architecture. To adopt optics in large-scale multiprocessor cluster systems, efficient routing and scheduling techniques are needed. To this end, novel self-routing strategies for all-optical packet switched networks and on-line scheduling methods that can result in collision free communication and achieve real time operation in high-speed multiprocessor systems are proposed. The system is designed to allow failed/faulty nodes to stay in place without appreciable performance degradation. The approach is to develop a dynamic communication environment that will be able to effectively adapt and evolve with a high density of missing units or nodes. A joint CPU/bandwidth controller that maximizes the resource allocation in this dynamic computing environment is introduced with an objective to optimize the distributed cluster architecture, preventing performance/system degradation in the presence of failed/faulty nodes. A thorough analysis, feasibility study and description of the characteristics of a 3-Dimensional multicomputer system capable of achieving 100 teraFLOP performance is discussed in detail. Included in this dissertation is throughput analysis of the routing schemes, using methods from discrete-time queuing systems and computer simulation results for the different proposed algorithms. A prototype of the 3D architecture proposed is built and a test bed developed to obtain experimental results to further prove the feasibility of the design, validate initial assumptions, algorithms, simulations and the optimized distributed resource allocation scheme. Finally, as a prelude to further research, an efficient data routing strategy for highly scalable distributed mobile multiprocessor networks is introduced.

An experimental investigation exploring the use of wire mesh/hollow glass microsphere combination for use as thermal insulation was conducted with the aim to conclude whether or not it represents a superior insulation technology to those on the market. Three primary variables, including number of wire mesh layers, filler material, and temperature dependence were studied using an apparatus that was part of L.I.C.H.E.N (LabVIEW Integrated Conduction Heat Experiment Network), a setup whose basic components allow three vertically stacked samples to be thermally and mechanically controlled. Knowing the temperature profile in the upper and lower samples allows for determination of thermal conductivity of the middle material through the use of Fourier?s law. The numbers of layers investigated were two, four, six, and eight, with each separated by a metallic liner. The filler materials included air, s15, s35 and s60HS 3MTM hollow glass microspheres. The experiments were conducted at four temperatures of 300, 330, 366, and 400K with an interface pressure of 20 Psi. The experimental results indicated the ?number of layers? used was the primary factor in determining the effective thermal conductivity value. The addition of hollow glass microspheres as filler material resulted in statistically insignificant changes in effective thermal conductivity. Increasing the number of wire mesh layers resulted in a corresponding increase in effective thermal conductivity of the insulation. Changes in temperature had little to no effect on thermal conductivity. The effective thermal conductivity values for the proposed insulation structure ranged from 0.22 to 0.65 W/m-K, the lowest of which came from the two layer case having air as filler material. The uncertainties associated with the experimental results fell between 10 to 20 percent in all but a few cases. In the best performing cases, when compared with existing insulation technologies, thermal conductivity was approximately 3 to 10 times higher than these methods of insulation. Thus, the proposed insulation scheme with hollow glass-sphere filler material does not represent superior technology, and would be deemed uncompetitive with those readily available in the insulation market.