We present a Markov chain analysis for studying the performance of wireless ad hoc networks. The models presented in this dissertation support an arbitrary backoff strategy. We found that the most important parameter affecting the performance of binary exponential backoff is the initial backoff window size. Our experimental results show that the probability of collision can be reduced when the initial backoff window size equals the number of terminals. Thus, the throughput of the system increases and, at the same time, the delay to transmit the frame is reduced. In our second contribution, we present a new analytical model of a Medium Access Control (MAC) layer for wireless ad hoc networks that takes into account frame retry limits for a four-way handshaking mechanism. This model offers flexibility to address some design issues such as the effects of traffic parameters as well as possible improvements for wireless ad hoc networks. It effectively captures important network performance characteristics such as throughput, channel utilization, delay, and average energy. Under this analytical framework, we evaluate the effect of the Request-to-Send (RTS) state on unsuccessful transmission probability and its effect on performance particularly when the hidden terminal problem is dominant, the traffic is heavy, or the data frame length is very large. By using our proposed model, we show that the probability of collision can be reduced when using a Request-to-Send/Clear- to-Send (RTS/CTS) mechanism. Thus, the throughput increases and, at the same time, the delay and the average energy to transmit the frame decrease. In our third contribution, we present a new analytical model of a MAC layer for wireless ad hoc networks that takes into account channel bit errors and frame retry limits for a two-way handshaking mechanism. This model offers flexibility to address design issues such as the effects of traffic parameters and possible improvements for wireless ad hoc networks. We illustrate that an important parameter affecting the performance of binary exponential backoff is the initial backoff window size. We show that for a low bit error rate (BER) the throughput increases and, at the same time, the delay and the average energy to transmit the frame decrease. Results show also that the negative acknowledgment-based (NAK-based) model proves more useful for a high BER. In our fourth contribution, we present a new analytical model of a MAC layer for wireless ad hoc networks that takes into account Quality of Service (QoS) of the MAC layer for a two-way handshaking mechanism. The model includes a high priority traffic class (class 1) and a low priority traffic class (class 2). Extension of the model to more QoS levels is easily accomplished. We illustrate an important parameter affecting the performance of an Arbitration InterFrame Space (AIFS) and small backoff window size limits. They cause the frame to start contending the channel earlier and to complete the backoff sooner. As a result, the probability of sending the frame increases. Under this analytical framework, we evaluate the effect of QoS on successful transmission probability and its effect on performance, particularly when high priority traffic is dominant. / Graduate

Due to rising energy prices as well as supply and ecological concerns, there is a strong interest in reducing the energy used in buildings. As such, it is desirable to model the operation of a building and predict its future energy use. In predicting the energy use of a building, the heat gain/loss through windows is an important factor. In order to accurately model this heat gain/loss, the convective heat transfer coefficient of any insect screens mounted adjacent to the windows needs to be known. This thesis describes an investigation into the heat transfer from insect screens mounted towards the indoor side of a window. The convective heat transfer coefficient of an insect screen varies based on several parameters. For implementation in building energy modelling software, it is desirable to be able to predict the convective heat transfer coefficient for an arbitrary insect screen. Due to the number of variables and the large dynamic range of the details required for modelling, direct simulation of a range of whole insect screens was not completed. Instead, a range of numerical models representing small sections of an insect screen were created. By comparing results from these to available correlations for simpler geometries, such as cylinders and flat plates, estimates for the heat transfer coefficient of a screen can be obtained. The results were non-dimensionalized for analysis and different methodologies for the prediction of heat transfer from an indoor window insect screen are described.

Developing and applying pre-clinical tumour models in order to determine the mechanistic action of applied therapies is essential if we aim to improve antitumour strategies in the clinical setting. The chaotic nature of tumour vasculature impacts directly on the effectiveness of combined chemo-radiotherapy and antiangiogenic (AA) strategies and as such warrants closer study. This work looked at the effects of novel AAs combined with clinically relevant radiotherapy (RT) using both conventional murine xenograft growth delay studies and real-time imaging. The imaging methodology was the non-invasive Dorsal Window Chamber/Intra Vital Microscopy (DWC/IVM) model which allows the study of real-time vascular responses to these therapies. The DWC/IVM model was applied to determine whether the DNA repair inhibitors Nicotinamide, AG14361 and AGO14699 had additional modes of action which could contribute to tumour radioresistance/radiosensitivity. Using the DWC/IVM model a secondary quantifiable mechanistic function was determined where these drugs also increased tumour vessel permeability. The DWC/IVM model was also used to investigate the effects of AZD2171 and AZD6244 combined with radiotherapy. These agents can inhibit angiogenic signalling pathways and it was demonstrated that both drugs worked by reducing tumour microvascular density when used in combination with radiation. In studies looking at the influence of hypoxia inducible factor-1(HIF-1) on tumour response to radiation the DWC/IVM model provided measurable differences in the microvascular density between HIF-1 deficient and HIF-1 competent tumours. The DWC/IVM model allowed the direct visualisation and quantification of the less well developed vasculature in HIF-1 deficient tumours compared to that found in HIF-1 competent tumours. The results provide a mechanistic basis for understanding the improved response to radiotherapy of HIF-1 deficient tumours. By applying the DWC/IVM model to conventional murine xenograft models the DWC/IVM proved itself as a useful research tool where continuous real-time non-invasive measurements could be made without the need for large numbers of time points or laborious histological analysis.

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Studying movement, through the design and development of a narrow residential site with access from water and land at opposing ends. Utilizing parallel planes, connect three zones of the site and maximizing directional views along its length, while formulating an architectural language of path and passage. The façade design is a layering of fixed and active colored glass planes to allow dominate parallel wall, to run through the site without the obstruction of frames. Active glass planes rotate along horizontal and vertical axis and connect the interior and exterior living spaces. Glass façade design led to development of a hinging mechanism to provide rotational movement at various opening increments and locking points, while incorporating it into the fixed glazing system. / Master of Architecture

With the continuing growth of the Internet and network protocols, there is a need for Protocol Development Environments. Simulation environments like ns and OPNET require protocol code to be rewritten in a discrete event model. Direct Code Execution Environments (DCEE) solve the Verification and Validation problems by supporting the execution of unmodified protocol code in a controlled environment. Open Network Emulator (ONE) is a system supporting Direct Code Execution in a parallel environment - allowing unmodified protocol code to run on top of a parallel simulation layer, capable of simulating complex network topologies. Traditional approaches to the problem of Parallel Discrete Event Simulation (PDES) broadly fall into two categories. Conservative approaches allow processing of events only after it has been asserted that the event handling would not result in a causality error. Optimistic approaches allow for causality errors and support means of restoring state — i.e., rollback. All standard approaches to the problem of PDES are either flawed by their assumption of existing event patterns in the system or cannot be applied to ONE due to their restricted analysis on simplified models like queues and Petri-nets. The Adaptive Time Window algorithm is a bounded optimistic parallel simulation algorithm with the capability to change the degree of optimism with changes in the degree of causality in the network. The optimism at any instant is bounded by the amount of virtual time called the time window. The algorithm assumes efficient rollback capabilities supported by the â Weaves' framework. The algorithm is reactive and responds to changes in the degree of causality in the system by adjusting the length of its time window. With sufficient history gathered the algorithm adjusts to the increasing causality in the system with a small time window (conservative approach) and increases to a higher value (optimistic approach) during idle periods. The problem of splitting the entire simulation run into time windows of arbitrary length, whereby the total number of rollbacks in the system is minimal, is NP-complete. The Adaptive Time Window algorithm is compared against offline greedy approaches to the NP-complete problem called Oracle Computations. The total number of rollbacks in the system and the total execution time for the Adaptive Time Window algorithm were comparable to the ones for Oracle Computations. / Master of Science

A study of public and private space through human scale architectural elements: Window, Material and Path. The project is an urban infill that is very narrow and long, and incorporates an alley that connects one side of the block to another. The program combines a small restaurant with a home above for the family that owns it. Questions of light and privacy immediately arise, and the thesis begins. A window is typically a two dimensional object that opens for light and air. Window is a dining room overlooking a garden or a large sill to sit on. Window is not only part of the façade but also breaks through it, bringing small private spaces beyond the building boundaries and defining the interior spaces of the home. Window is also a small skylight facing east, scooping in soft morning light to a bedroom. The materials of a building are what it is made of: its cladding, waterproofing, walls and floors. Material makes an emotive space through touch and reflection. Concrete is heavy, rough and protective, Concrete is boundary. Contrastingly, Wood is soft, flexible and changing, Wood is home. An alley is a narrow walkway, an undesirable secondary access point. How can an alley become Path? Path is an invitation to walk and be, Path is not the same from beginning to end. Path belongs to the city, the restaurant, and the pedestrian. Inside + Outside studies what makes these public and private places at the human scale, and how architecture appeals to intuition rather than definition. / Master of Architecture

Windows reduce heat loss and heat gain by resisting conduction, convection, and radiation using thermal breaks, low-emissivity films, and window gaps. Contrary to advancing these resistive qualities, this research introduced a highly conductive gap medium using Al2O3 nanoparticles dispersed in deionized water to enhance thermal conductivity. The solution harnessed the photothermal properties of Al2O3 nanofluids to trap, store, and transport thermally charged fluids to heat exchangers to preheat air and water, and to generate electricity forming a transparent generator—the Nanowindow. Seven Nanowindow prototypes with varying orders of air and fluid columns were fabricated and tested using distilled water (H2Owindows) to establish a baseline of performance. A solar simulator was built to avoid environmental radiant flux irregularities providing a uniform test condition averaging 750–850 W/m2, and resulted in an undefined spectral match, Class B spatial uniformity, and Class B temporal stability. All Nanowindows were tested in a calibrated hot box determined to have a ±4% degree of accuracy based on four laboratory samples establishing a framework to conduct U-factor and solar heat gain coefficient (SHGC) measurements. Four heat exchange experiments and standardized window performance metrics (U-factor, SHGC, and visible transmission) where conducted on seven H2Owindows. The top two H2Owindows were then tested using Al2O3 nanofluids. The highest performing Nanowindow improved total convective heat transfer rates using Al2O3 by 90% over water baseline, and 61% improvement in preheat water experiments. Nanowindows coupled with thermoelectric generators generated a rated voltage of 0.31VDC/0.075ADC per 12in2 Nanowindow, an improvement of 38% over baseline. Standardized window performance metrics confirmed Nanowindow U-factors ranging from 0.23 to 0.54, SHGC from 0.43 to 0.67, and visible transmittance coefficient (VT) ranging from 0.27 to 0.38. The concept of nature as model system thinking provided a theoretical framework for the research and proof of concept experiment. Ultimately, the experiment shifted window gaps from resisting energy to harnessing solar energy. The Nanowindow thus presents a unique opportunity to turn vast glass facades into transparent generators to offset energy demand, and reduce greenhouse gases.

OpenGL is getting used more in window system as a way of improving performance and enabling new functionality. Examples of two systems using different approaches of how OpenGL is being used are Quartz Extreme and Fresco. Quartz Extreme uses window composition which assures fast redisplay and Fresco on the other hand uses a structured graphics approach which utilises OpenGL on a much lower level compared to Quartz Extreme which operates at a window level. Fresco’s way brings great flexibility and an ability to mix 2D and 3D-objects on the desktop. But each of the approaches has its problems; Quartz extreme requires a large amount of memory for buffering of the window contents and Fresco has performance problems when redisplaying complex structures. / OpenGL används mer och mer i fönstersystem som ett sätt att förbättra prestanda och möjliggöra ny funktionalitet. Två exempel på olika sätt att nyttja OpenGL är Quartz Extreme och Fresco, Quartz Extreme använder fönster komposition vilket garanterar snabbt omritning av fönster medan Fresco använder Structured Graphics vilket använder OpenGL på en mycket lägre nivå inom fönstersystemet jämfört med Quartz Extreme som är på fönster nivå. Frescos angreppsätt medför en större flexibilitet och möjligheten att blanda 2D och 3D-objekt på skrivbordet. Men bägge angreppsätten har sina nackdelar; Quartz Extreme kräver en stor mängd minne eftersom den buffrar fönsterinnehållet och Fresco får problem med prestandan vid omritning av komplexa strukturer.