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<p> An optical time division multiplexing (TDM) scheme using soliton interaction is proposed in the thesis to save the time-bandwidth prduct (TBP). The soliton multiplexer (MUX) consisting of a highly nonlinear fiber (HNLF) combines two adjacent solitons to form a composite soliton, while the soliton demultiplexer (DEMUX) consisting of a similar HNLF restores the component solitons. The case of interaction between identical fundamental solitons is discussed first. However, when this scheme is used in the conventional TDM system, the total bit rate transmitted over the channel is limited by the time interval between the two adjacent component solitons. Therefore, a modified multiplexing scheme using interaction between different solitons is proposed to satisfy more practical engineering applications. The theoretical analysis and numerical simulation results demonstrate that the modified optical TDM scheme offers a higher TBP efficiency and suitable for conventional TDM, which makes it an attractive candidate for meeting the challenge of increasing demand on frequency bandwidth in modern optical communications. </p> / Thesis / Master of Applied Science (MASc)

<p> Nonlinear amplification schemes for hearing aids have been developed to deal primarily with the problem of loudness recruitment. The most commonly used form of nonlinear amplification is wide-dynamic-range compression (WDRC). Unfortunately, finding WDRC characteristics that satisfactorily deal with loudness recruitment while maintaining good speech intelligibility has proven difficult. An alternative nonlinear scheme, Advanced Dynamic Range Optimization (ADRO), has been shown in several studies to provide better speech intelligibility and listening comfort than fast-acting WDRC. ADRO uses a set of fuzzy-logic rules to make gain changes to optimize audibility, comfort, protection against loud sound, and noise attenuation. The "hearing protection" gain rule acts instantaneously, whereas the audibility and comfort rules adjust the gain slowly, such that ADRO provides linear amplification most of the time.</p> <p> The goal of this study is to examine the physiological basis for the relative performance of linear amplification, WDRC, and ADRO. Sentences from the TIMIT Speech Database were processed by each algorithm. In the case of WDRC, both single-channel and multi-channel schemes with fast and slow dynamics were tested. Speech signals were presented at 52, 62, 74, and 82 dB SPL (sound pressure level) with various noise levels and types, to simulate real-life environments. The simulations first use an auditory-periphery model to generate a "neurogram" of the auditory nerve's representation of the test speech material. The spectral and temporal modulations in the neurogram are then analyzed by a model of cortical speech processing. The effects of the background noise, the presentation level, the hearing loss and the amplification scheme are evaluated by comparing the cortical model response for a given condition (the "test" response) to the cortical model response to the same TIMIT sentence presented in quiet at 65 dB SPL to the normal-hearing model (the "template" response). From the difference between the test and template responses, a spectro-temporal modulation index (STMI) value is calculated. High STMI values predict good speech intelligibility, while low values predict poor intelligibility. Results show that ADRO is better at restoring the neural representation of speech than the other algorithms tested, even when the WDRC algorithms utilize slow time constants. In the case of no background noise, all the algorithms perform similarly well. However, when background noise is added, STMI values for higher SPLs drop notably for all the algorithms except for ADRO, which sustains a stable value throughout the range of SPLs test.</p> / Thesis / Master of Engineering (MEngr)

Natural user interfaces, including verbal vocal interactions like speech processing, are ubiquitous and commonly used in both industry and academic settings. However, this field is limited by the speech and language components. Non-verbal vocal interaction (NVVI) provides further opportunities for people to use their vocals as an input modality. Despite the many possibilities of NVVI input modalities, such as whistling, humming, and tongue clicking, the field is niche and literature is few and far between. This work attempts to address these gaps, as well as the small sample sizes of performed studies of prior work. The problem definition is defined as to perform a large-scale study exploring a pitch-based NVVI modality that uses a relative pitch interaction technique to offer a continuous mode of one-dimensional interaction. A user study is outlined and performed via an ecosystem comprising of Amazon Mechanical Turk for recruitment and study access, a modularized study website, and a secure server that stores the study results, tasks users with controlling a slider with the NVVI technique by humming and whistling, in addition to using the computer mouse to perform these tasks as a baseline. In total, 72 participants' results are considered for analysis. Results show that the pitch based NVVI technique used in this study does not follow Fitts' Law, is not as performant as the computer mouse, humming is a more performant modality with the NVVI technique than whistling, and that participants experienced a significantly higher task workload using the NVVI technique than the computer mouse. Using the results of this study and from reviewed literature, an NVVI framework is developed and implemented as a contribution of this work. / Master of Science

No / Wounds arising from various conditions are painful, embarrassing and often requires treatment plans which are costly. A crucial task, during the treatment of wounds is the measurement of the size, area and volume of the wounds. This enables to provide appropriate objective means of measuring changes in the size or shape of wounds, in order to evaluate the efficiency of the available therapies in an appropriate fashion. Conventional techniques for measuring physical properties of a wound require making some form of physical contact with it. We present a method to model a wide variety of geometries of wound shapes. The shape modelling is based on formulating mathematical boundary-value problems relating to solutions of Partial Differential Equations (PDEs). In order to model a given geometric shape of the wound a series of boundary functions which correspond to the main features of the wound are selected. These boundary functions are then utilised to solve an elliptic PDE whose solution results in the geometry of the wound shape. Thus, here we show how low order elliptic PDEs, such as the Biharmonic equation subject to suitable boundary conditions can be used to model complex wound geometry. We also utilise the solution of the chosen PDE to automatically compute various physical properties of the wound such as the surface area, volume and mass. To demonstrate the methodology a series of examples are discussed demonstrating the capability of the method to produce good representative shapes of wounds.

Subitizing, a quick apprehension of the numerosity of a small set of items, is inconsistently utilized by preschool educators to support early number understandings (Sarama & Clements, 2009). The purpose of this qualitative study is to investigate the relationship between children’s number understanding and subitizing activity. Sarama and Clements (2009) consider students’ subitizing activity as shifting from reliance upon perceptual processes to conceptual processes. Hypothesized mental actions carried into subitizing activity by children have not yet been empirically investigated (Sarama & Clements, 2009). Drawing upon Piaget’s (1968/1970) three mother structures of mathematical thinking, the theoretical implications of this study consider expanding the scope of Piaget’s (1968/1970) definition of topological thinking structures to include patterned orientations. Increasing the scope of this definition would allow for the investigation of the development of topological thinking structures and subitizing activity. An 11-week teaching experiment was conducted with six preschool aged children in order to analyze student engagement with subitizing tasks (Steffe & Ulrich, in press). To infer what perceptual and conceptual processes students relied upon when subitizing, tasks were designed to either assess or provoke cognitive changes. Analysis of interactions between students and the teacher-researcher informed this teacher-researcher of cognitive changes relative to each student’s thinking structure. Results indicated that students rely upon the space between items, symmetrical aspects of items, and color of items when perceptually subitizing. Seven different types of subitizing activity were documented and used to more explicitly describe student reliance upon perceptual or conceptual processes. Conceptual subitizing activity was redefined in this study, as depending upon mental reversibility and sophisticated number schemes. Students capable of conceptual subitizing were also able to conserve number. Students capable of conserving number were not always capable of conceptual subitizing. The symmetrical aspects of an item’s arrangement elicited students’ attention towards subgroups and transitioning students’ perceptual subitizing to conceptual subitizing. Combinations of counting and subitizing activity explained students’ reliance upon serial and classification thinking structures when transitioning from perceptual subitizing to conceptual subitizing. Implications of this study suggest effectively designed subitizing activity can both assess students’ number understandings, and appropriately differentiate preschool curriculum. / Ph. D.

Optimum filter-and-sum beamforming is useful for array systems that suffer from spatially correlated noise and interference over large bandwidth. The set of finite impulse response (FIR) filter coefficients used to implement the optimum filter-and-sum beamformer are selected to optimize signal-to-noise ratio (SNR) and reduce interference from the certain directions. However, these array systems may also be vulnerable to dispersion caused by physical components such as antennas and cables, especially when the dispersion is unequal between sensors. The unequal responses can be equalized by using FIR filters. Although the problems of optimum-SNR beamforming, interference mitigation, and per-sensor dispersion have previously been individually investigated, their combined effects and strategies for mitigating their combined effects do not seem to have been considered. In this dissertation, combination strategies for optimum filter-and-sum beamforming and sensor dispersion correction are investigated. Our objective is to simultaneously implement optimum filter-and-sum beamforming and per-sensor dispersion correction using a single FIR filter per sensor. A contribution is to reduce overall filter length, possibly also resulting in a significant reduction in implementation complexity, power consumption, and cost. Expressions for optimum filter-and-sum beamforming weights and per-sensor dedispersion filter coefficients are derived. One solution is found via minimax optimization. To assess feasibility, the cost is analyzed in terms of filter length. These designs are considered in the context of LWA1, the first ``station'' of the Long Wavelength Array (LWA) radio telescope, consisting of 512 bowtie-type antennas and operating at frequencies between 10 MHz and 88 MHz. However, this work is applicable to a variety of systems which suffer from non-white spatial noise and directional interference and are vulnerable to sensor dispersion; e.g., sonar arrays, HF/VHF-band riometers, radar arrays, and other radio telescopes. / Ph. D.

Lipooligosaccharide (LOS) is the major outer membrane component of many Gram-negative bacteria inhabiting the mucosal membranes, including pathogenic species of <I>Haemophilus</I> and <I>Neisseria</I>. LOS phase variation is one mechanism by which some of these bacteria avoid the host immune response. To better understand LOS phase variation as a virulence mechanism of <I>H. somnus</I>, knowledge of the antigenic diversity of LOS epitopes must be increased. Monoclonal antibodies (MAbs) to <I>H. somnus</I> LOS were produced and used with cross-reacting MAbs to <I>H. aegyptius</I> LOS (MAb 5F5) and <I>Neisseria</I> <I>gonorrhoeae</I> LOS (MAb 3F11) in an ELISA to investigate LOS heterogeneity among forty-five strains of <I>H. somnus</I>. Using three MAbs, thirty-nine of these <I>H. somnus</I> strains were grouped into six antigenic types. Three groups, associated solely with the cross-reacting MAbs 5F5 and 3F11, included the majority (76%) of <I>H. somnus</I> strains. The anti-<I>H. somnus</I> LOS MAb 5D7 recognized a low frequency epitope associated with each of the remaining three groups, which included 11% of the <I>H. somnus</I> strains. Six strains (13%) were not recognized by any of these MAbs. Inhibition ELISA experiments showed that the MAb 5F5 epitope contained phosphocholine (PCho) and this epitope was present in 56% of the strains tested. The MAb 5F5 epitope is phase variable in <I>H. somnus</I> LOS. How PCho negative variants could allow for systemic infection after initial colonization of the mucosa by PCho positive variants is discussed. / Master of Science

Test and evaluation (TandE) is a critically important step before in-the-field deployment of radio-frequency (RF) hardware in order to assure that the hardware meets its design requirements and specifications. Typically, TandE is performed either in a lab setting utilizing a software simulation environment or through real-world field testing. While the former approach is typically limited by the accuracy of the simulation models (particularly of the anticipated hardware effects) and by non-real-time data rates, the latter can be extremely costly in terms of time, money, and manpower. To build upon the strengths of these approaches and to mitigate their weaknesses, this work presents the development of an FPGA-based TandE tool that allows for real-time pseudo-random aggregate signal generation for testing RF receiver hardware (such as communication receivers, spectrum sensors, etc.). In particular, a framework is developed for an FPGA-based implementation of a test signal emulator that generates randomized aggregate spectral environments containing signals with random parameters such as center frequencies, bandwidths, start times, and durations, as well as receiver and channel effects such as additive white Gaussian noise (AWGN). To test the accuracy of the developed spectrum generation framework, the randomization properties of the framework are analyzed to assure correct probability distributions and independence. Additionally, FPGA implementation decisions, such as bit precision versus accuracy of the generated signal and the impact on the FPGA's hardware footprint, are analyzed.This analysis allows the test signal engineer to make informed decisions while designing a hardware-based RF test system. This framework is easily extensible to other signal types and channel models, and can be used to test a variety of signal-based applications. / Master of Science / Test and evaluation (TandE) is a critically important step before in-the-field deployment of radio-frequency signal hardware in order to assure that the hardware meets its design requirements and specifications. Typically, TandE is performed either in a lab setting utilizing a software simulation or through real-world field testing. While the former approach is typically limited by the accuracy of the simulation models and by slower data rates, the latter can be extremely costly in terms of time, money, and manpower. To address these issues, a hardware-based signal generation approach that takes the best of both methods mentioned above is developed in this thesis. This approach allows the user to accurately model a radio-frequency system without requiring expensive equipment. This work presents the development of a hardware-based TandE tool that allows for real-time random signal generation for testing radio-frequency receiver hardware (such as communication receivers). In particular, a framework is developed for an implementation of a test signal emulator that allows for user-defined randomization of test signal parameters such as frequencies, signal bandwidths, start times, and durations, as well as communications receiver effects. To test the accuracy of the developed emulation framework, the randomization properties of the framework are analyzed to assure correct probability distributions and independence. Additionally, hardware implementation decisions such as bit precision versus quality of the generated signal and the impact on the hardware footprint are analyzed. Ultimately, it is shown that this framework is easily extensible to other signal types and communication channel models.

No / The use of queue thresholds is a well known technique for network traffic congestion control. This motivates the study of a single server queue with R(R ¿ 2) distinct priority classes under Head of Line (HoL) service priority discipline, Partial Buffer Sharing (PBS) scheme and a finite capacity vector N, representing a sequence of thresholds (N1, N2, ¿ , NR) for each class jobs. The external traffic is modelled using the compound Poisson process or generalised exponential (GE) distribution which can capture the bursty property of the network traffic. The transmission times have also been modelled using the GE distribution to depict the bulk departures from the system. Using a GE/GE/1/N approximation, a closed form cost-effective analytical solution is obtained using the principle of maximum entropy (ME). The forms of the joint, aggregate and marginal state probabilities, as well as basic performance measures such as utilisation and blocking probabilities are analytically established at equilibrium via appropriate mean value constraints and the generating function approach. Consequently, efficient recursive expressions of low computational cost are determined. Typical numerical experiments are included to illustrate the credibility of the proposed mechanism in the context of different QoS grades for various network traffic classes. This model, therefore, can be used as a powerful tool to provide a required grade of service to a particular class of traffic in any heterogeneous networks.