With the proliferation of unmanned aircraft designed for national security and commercial purposes, opportunities exist to create high-fidelity aerodynamic models with flight test techniques developed specifically for remotely piloted aircraft. Then, highly maneuverable unmanned aircraft can be employed to their greatest potential in a safe manner using advanced control laws. In this dissertation, novel techniques are used to identify nonlinear, coupled, aerodynamic models for fixed-wing, unmanned aircraft from flight test data alone. Included are quasi-steady and unsteady nominal flight models, aero-propulsive models, and spinning flight models. A novel flight test technique for unmanned aircraft, excitation with remote uncorrelated pilot inputs, is developed for use in nominal and nonlinear flight regimes. Orthogonal phase-optimized multisine excitation signals are also used as inputs while collecting gliding, aero-propulsive, and spinning flight data. A novel vector decomposition of explanatory variables leads to an elegant model structure for stall spin flight data analysis and spin aerodynamic modeling. Results for each model developed show good agreement between model predictions and validation flight data. Two novel applications of aerodynamic modeling are discussed including energy-based nonlinear directional control and a spin flight path control law for use as a flight termination system. Experimental and simulation results from these applications demonstrate the utility of high-fidelity models developed from flight data. / Doctor of Philosophy / This dissertation presents flight test experiments conducted using a small remotely controlled airplane to determine mathematical equations and parameter values, called models, to describe the airplane's motion. Then, the models are applied to control the path of the airplane. The process to develop the models and predict an airplane's motion using flight data is described. New techniques are presented for data collection and analysis for unusual flight conditions, including a spinning descent. Results show the techniques can predict the airplane's motion very well. Two experiments are presented demonstrating new applications and the usefulness of the mathematical models.

The ever-increasing demand for private and sensitive data transmission over wireless networks has made security a crucial concern in the current and future large-scale, dynamic, and heterogeneous wireless communication systems. To address this challenge, wireless researchers have tried hard to continuously analyze the jamming threats and come up with improved countermeausres. In this research, we have analyzed the jamming-vulnerabilities of the leading multi-carrier communication systems, Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier Frequency Division Multiple Access (SC-FDMA). In order to lay the necessary theoretical groundwork, first we derived the analytical BER expressions for BPSK/QPSK and analytical upper and lower bounds for 16-QAM for OFDMA and SC-FDMA using Pilot Symbol Assisted Channel Estimation (PSACE) techniques in Rayleigh slow-fading channel that takes into account channel estimation error as well as pilot-jamming effect. From there we advanced to propose more novel attacks on the Cyclic Prefix (CP) of SC-FDMA. The associated countermeasures developed prove to be very effective to restore the system. We are first to consider the effect of frequency-selectivity and fading correlation of channel on the achievable rates of the legitimate system under pilot-spoofing attack. With respect to jamming mitigation techniques, our approaches are more focused on Anti-Jamming (AJ) techniques rather than Low Probability of Intercept (LPI) methods. The Channel State Information (CSI) of the two transceivers and the CSI between the jammer and the target play critical roles in ensuring the effectiveness of jamming and nulling attacks. Although current literature is rich with different channel estimation techniques between two legitimate transceivers, it does not have much to offer in the area of channel estimation from jammer's perspective. In this dissertation, we have proposed novel, computationally simple, deterministic, and optimal blind channel estimation techniques for PSK-OFDM as well as QAM-OFDM that estimate the jammer channel to the target precisely in high Signal-to-Noise (SNR) environment from a single OFDM symbol and thus perform well in mobile radio channel. We have also presented the feasibility analysis of estimating transceiver channel from jammer's perspective at the transmitter as well as receiver side of the underlying OFDM system. / Ph. D.

Despite the fact ultra-wideband (UWB) technology has been around for over 30 years, there is a newfound excitement about its potential for communications. With the advantageous qualities of multipath immunity and low power spectral density, researchers are examining fundamental questions about UWB communication systems. In this work, we examine UWB communication systems paying particular attention to transmitter and receiver design. This thesis is specifically focused on a software radio transceiver design for impulse-based UWB with the ability to transmit a raw data rate of 100 Mbps yet encompasses the adaptability of a reconfigurable digital receiver. A 500 ps wide Gaussian pulse is generated at the transmitter utilizing the fast-switching characteristics of a step recovery diode. Pulse modulation is accomplished via several stages of RF switches, filters, and amplifiers on a fully designed printed circuit board specifically manufactured for this project. Critical hardware components at the receiver consist of a bank of ADCs performing parallel sampling and an FPGA employed for data processing. Using a software radio design, various modulation schemes and digital receiver topologies are accommodated along with a vast number of algorithms for acquisition, synchronization, and data demodulation methods. Verification for the design is accomplished through transmitter hardware testing and receiver design simulation. The latter includes bit error rate testing for a variety of modulation schemes and wireless channels using a pilot-based matched filter estimation technique. Ultimately, the transceiver design demonstrates the advantages and challenges of UWB technology while boasting high data rate communication capability and providing the flexibility of a research testbed. / Master of Science

This thesis examines the benefits of using adaptive modulation and coding in terms of spectral efficiency and probability of bit error. Specifically, we examine the performance enhancement made possible by using linear prediction along with channel estimation in conjunction with adaptive modulation. We begin this manuscript with basic fundamentals of our study, followed by a detailed view of simulations, their results, and our conclusions from them. The study includes simulations in slow and moderately fast flat fading Rayleigh channels. We present our findings regarding the advantages of using predictive measures to foresee the state of the channel and make adjustments to transmissions accordingly. In addition to finding the general advantages of channel prediction in adaptive modulation, we explore various ways to adjust the prediction algorithm when we are faced with high Doppler rates and fast fading. By the end of this work, we should have a better understanding of when channel prediction is most valuable to adaptive modulation and when it is weakest, and how we can alleviate the problems that prediction will have in harsh environments. / Master of Science

This study uses the Self Determination Theory (SDT) to describe and analyse what motivates pilots whilst having limited control over working hours. Pilots work in a challenging environment with variable working hours and high operational demands. This affects the pilots autonomous, intrinsic, extrinsic and controlled motivation. The study uses a qualitative approach interviewing eight Swedish pilots working at different airlines. This study describes and analyses the sense of autonomy, sense of competence and sense of relatedness, and how autonomous motivation, intrinsic motivation, extrinsic motivation, and controlled motivation affects pilots´ motivation. This study finds that pilots value the sense of autonomy that comes from empowerment to take decisions within the strict framework of rules they operate in. The pilots feel a strong sense of competence from training programs and knowledge transfer colleagues, and relatedness to colleagues through a sense of being cared for, all these seems to promote autonomous and intrinsic motivation. Further, intrinsic motivation arises from a passion for flying and executing leadership. Extrinsic motivation arises from salary, and fear of punishment. The pilots lack of ability to control their working hours leads to controlled motivation and stress. The findings of this study could be used to improve pilot welfare and motivation. By understanding and addressing pilot motivation airlines can develop strategies to support its workforce more effectively.

Um método para avaliação do uso de ganho adequado em ensaios de verificação de PIO (Pilot Induced Oscillations) é apresentado. As tarefas de manobra sintética (Synthetic Tracking Task) são utilizadas para demonstração. A teoria é baseada no conceito de entropia estatística proveniente da teoria da informação e no modelo estrutural do piloto humano. O método é apresentado para manobras executadas no eixo lateral e oferece uma medida do ganho humano utilizado durante a sua execução em malha-fechada. Para a modelagem da planta é utilizado modelo black-box com equacionamento de espaço de estados e identificação de parâmetros. Dados de ensaios em voo provenientes de uma aeronave de transporte certificada FAR-25 são utilizados para medir a razão entre o tempo gasto pelo piloto humano em uma malha fechada em posição versus o tempo em uma malha de derivada da posição (roll vs. roll rate). Esta medida é proposta como validadora da execução correta do ensaio. / A method is proposed to verify losed-loop adequate flight test piloting gain in PIO aircraft certification. The synthetic tracking task PIO flight test is used. The theory is based on the entropy concept from information theory and on the structural pilot model of the human pilot. The method is presented for single axis pilot tracking maneuvers and offers a measure of the human pilot gain employed during its execution. A black-box, state-space, parameter-identified model is used for the plant. Flight test data from a FAR-25 transport aircraft is used to verify the theory of how to determine a measure of the ratio between time spent by the human pilot in the error loop versus in the error rate loop to control the aircraft. This measure is proposed as a test point validation method for PIO flight testing.

Um método para avaliação do uso de ganho adequado em ensaios de verificação de PIO (Pilot Induced Oscillations) é apresentado. As tarefas de manobra sintética (Synthetic Tracking Task) são utilizadas para demonstração. A teoria é baseada no conceito de entropia estatística proveniente da teoria da informação e no modelo estrutural do piloto humano. O método é apresentado para manobras executadas no eixo lateral e oferece uma medida do ganho humano utilizado durante a sua execução em malha-fechada. Para a modelagem da planta é utilizado modelo black-box com equacionamento de espaço de estados e identificação de parâmetros. Dados de ensaios em voo provenientes de uma aeronave de transporte certificada FAR-25 são utilizados para medir a razão entre o tempo gasto pelo piloto humano em uma malha fechada em posição versus o tempo em uma malha de derivada da posição (roll vs. roll rate). Esta medida é proposta como validadora da execução correta do ensaio. / A method is proposed to verify losed-loop adequate flight test piloting gain in PIO aircraft certification. The synthetic tracking task PIO flight test is used. The theory is based on the entropy concept from information theory and on the structural pilot model of the human pilot. The method is presented for single axis pilot tracking maneuvers and offers a measure of the human pilot gain employed during its execution. A black-box, state-space, parameter-identified model is used for the plant. Flight test data from a FAR-25 transport aircraft is used to verify the theory of how to determine a measure of the ratio between time spent by the human pilot in the error loop versus in the error rate loop to control the aircraft. This measure is proposed as a test point validation method for PIO flight testing.

Globally the domestic worker sector is characterised by a sense of “voicelessness”—an esoteric silence fuelled by a dire need to survive. South Africa is heralded as a global ambassador for the rights of these women. Significant sectoral reforms in recent years regulate the transactional element of this employment relationship through stipulated minimum wages and employment standards. The relational element of this engagement, however, remains underexplored. A decade of global scholarship detailing the hardships that characterise this sector has helped to uncover the plight of domestic workers. The study provided the participants with an opportunity to express their experiences and feelings, and the documented findings will hopefully stimulate more scholarly debate on this issue. It is hoped that the study will engender more sensitivity towards the needs of this vulnerable group of workers and promote positive employment relations within the South African labour market. The study describes the lived realities of domestic workers within the South African labour legislative context through five separate but interrelated journal articles. Article 1 provides a detailed “plan of action” that documents the initial considerations and rationale for the study. Guided by existing scholarly discourse, the research questions are highlighted and the proposed research design is presented. Issues related to trustworthiness are debated. This article constitutes the research proposal that was submitted during the initial phase of this research journey. Article 2 presents a transparent account of the methodological considerations that guided the co-construction of meaning within the South African domestic worker sector. Situated within the interpretivist paradigm, with phenomenology as theoretical underpinning, purposive respondent-driven self-sampling resulted in the recruitment of 20 female participants. All of them can be described as domestic workers in terms of Sectoral Determination 7. The pilot study indicated the value of using metaphors while exploring tentative topics. An interview guide facilitated the exploration of key concepts during our engagement. Rich, dense descriptive verbatim accounts of participants’ lived realities confirmed data saturation. In-depth interviews were transcribed and analysed through an inductive process of data reduction. Emanating themes confirmed that the South African domestic workers sector is far from being voiceless if we are only willing to listen. Making these voices heard constitutes a progressive step in future efforts to empower this neglected sector of the labour market. In article 3 a life-cycle approach is used to explore participants’ lived experiences of their work-life cycle. Each individual progresses through these various phases which are contextualised as a transitional process as a result of their unique circumstances and personal trajectory. Findings confirmed the existence of an institutionalised culture of engagement within the sector perpetuated from one generation to the next. Attempts to exit the sector are unsuccessful due in part to their limited formal education and skills repertoire. The article concludes with the notion that domestic workers are trapped within a never-ending cycle of sectoral engagement, and the possibility of exiting the sector remains “but a dream” for many. Article 4 focusses on the reciprocal interpersonal relatedness that often develops due to the prolonged engagement within the individualised sectoral employment context. Characterised by caring and connectedness, this mutually dignified treatment not only signals but also enhances human flourishing. Participants’ accounts of relational reciprocity are indicative of the enactment of cardinal Ubuntu principles within the employment context. The need for actions that surpass the “letter of the law” in order to enhance flourishing within the South African domestic worker sector is advocated. Article 5 explores the role that legislative awareness fulfils in the everyday lives of domestic workers. Findings indicated that empowerment was an unknown construct for all participants. The participants had little or no confidence in engaging their employers on employment issues; this was due in part to their limited legislative awareness. Domestic workers should thus take ownership of their own empowerment efforts. This will sanction their right to assert their expectations of employment standards with confidence and make use of the judicial system to bring about compliant action. The article concluded with the notion that legislative awareness can result in empowered actions though informed employee voices. / PhD (Labour Relations Management), North-West University, Vaal Triangle Campus, 2014

Globally the domestic worker sector is characterised by a sense of “voicelessness”—an esoteric silence fuelled by a dire need to survive. South Africa is heralded as a global ambassador for the rights of these women. Significant sectoral reforms in recent years regulate the transactional element of this employment relationship through stipulated minimum wages and employment standards. The relational element of this engagement, however, remains underexplored. A decade of global scholarship detailing the hardships that characterise this sector has helped to uncover the plight of domestic workers. The study provided the participants with an opportunity to express their experiences and feelings, and the documented findings will hopefully stimulate more scholarly debate on this issue. It is hoped that the study will engender more sensitivity towards the needs of this vulnerable group of workers and promote positive employment relations within the South African labour market. The study describes the lived realities of domestic workers within the South African labour legislative context through five separate but interrelated journal articles. Article 1 provides a detailed “plan of action” that documents the initial considerations and rationale for the study. Guided by existing scholarly discourse, the research questions are highlighted and the proposed research design is presented. Issues related to trustworthiness are debated. This article constitutes the research proposal that was submitted during the initial phase of this research journey. Article 2 presents a transparent account of the methodological considerations that guided the co-construction of meaning within the South African domestic worker sector. Situated within the interpretivist paradigm, with phenomenology as theoretical underpinning, purposive respondent-driven self-sampling resulted in the recruitment of 20 female participants. All of them can be described as domestic workers in terms of Sectoral Determination 7. The pilot study indicated the value of using metaphors while exploring tentative topics. An interview guide facilitated the exploration of key concepts during our engagement. Rich, dense descriptive verbatim accounts of participants’ lived realities confirmed data saturation. In-depth interviews were transcribed and analysed through an inductive process of data reduction. Emanating themes confirmed that the South African domestic workers sector is far from being voiceless if we are only willing to listen. Making these voices heard constitutes a progressive step in future efforts to empower this neglected sector of the labour market. In article 3 a life-cycle approach is used to explore participants’ lived experiences of their work-life cycle. Each individual progresses through these various phases which are contextualised as a transitional process as a result of their unique circumstances and personal trajectory. Findings confirmed the existence of an institutionalised culture of engagement within the sector perpetuated from one generation to the next. Attempts to exit the sector are unsuccessful due in part to their limited formal education and skills repertoire. The article concludes with the notion that domestic workers are trapped within a never-ending cycle of sectoral engagement, and the possibility of exiting the sector remains “but a dream” for many. Article 4 focusses on the reciprocal interpersonal relatedness that often develops due to the prolonged engagement within the individualised sectoral employment context. Characterised by caring and connectedness, this mutually dignified treatment not only signals but also enhances human flourishing. Participants’ accounts of relational reciprocity are indicative of the enactment of cardinal Ubuntu principles within the employment context. The need for actions that surpass the “letter of the law” in order to enhance flourishing within the South African domestic worker sector is advocated. Article 5 explores the role that legislative awareness fulfils in the everyday lives of domestic workers. Findings indicated that empowerment was an unknown construct for all participants. The participants had little or no confidence in engaging their employers on employment issues; this was due in part to their limited legislative awareness. Domestic workers should thus take ownership of their own empowerment efforts. This will sanction their right to assert their expectations of employment standards with confidence and make use of the judicial system to bring about compliant action. The article concluded with the notion that legislative awareness can result in empowered actions though informed employee voices. / PhD (Labour Relations Management), North-West University, Vaal Triangle Campus, 2014

Background: Pelvic floor muscle (PFM) training is recommended as first line conservative management for stress urinary incontinence (SUI). The fundamental issue of how to optimally contract the PFM has not previously been investigated. An effective voluntary PFM contraction is known to positively influence the bladder neck and urethra which are urethrovesical (UV) structures associated with continence. The PFM may be globally or selectively contracted according to cue to instruction. The main research question was to investigate which cue to instruction for a PFM contraction has the potential to optimise position of UVSs following a brief period of practice in continent nulliparous pre-menopausal women (aiming to provide normative data) and parous menopausal women with previously unreported SUI. Hypotheses: Posterior or combined cues for instruction of PFM contraction are more influential in optimising UV position (UVP) during PFMC following brief practice than an anterior cue. Posterior or combined cues are equally influential in altering UVP. Aims: Preliminary aim was to investigate the reliability and suitability of 2-DRTUS and angle of urethral inclination (AUI) for imaging of selective contraction of the PFM and ease of reading images by a non diagnostic imaging researcher. Principal aim was to investigate if there is an optimal cue to instruction for a PFM contraction in two groups of women. Study 1: pre menopausal nulliparous continent women (to provide normative data) and Study 2: post menopausal parous stress incontinent women. Secondary aims were investigation of posture; ability to selectively contract the PFM contraction; and cue preference. Method: Study 1: Twenty women who were able to effectively and selectively contract were taught the following cues: anterior; posterior; anterior and posterior combined. Following 4 weeks of practice, perineal 2-D RTUS images of three PFMC for each cue were captured in supine and standing twice (for repeatability analysis) five minutes apart. Two raters measured AUI. Data analysis was undertaken using a Customized General Linear Model (GLM) ANOVA with Bonferroni correction for interactions between all variables; subject, cue, posture and test. Seventeen data sets were available for analysis. Study 2: Methodology was based on Study 1. Twenty-one women were taught the study cues, followed the practice protocol and underwent data collection in the supine position. Twenty-one sets of data were available for analysis. Results: Reliability: ICC [1,3] for intra rater reliability was 0.957 [CI 95%: 0.946 to 0.967 p=0.000], inter rater reliability [2,1] 0.820 [CI 95%: 0.768 to 0.861] and for repeatability [1,3] 0.781 [CI 95%: 0.690 to 0.849 p=0.000] (continent) and 0.954 [CI 95%:0.931 to 0.971 p=0.000] (incontinent). Principal results Study 1: anterior vs posterior cues (difference) 3.979˚ (CI 95%: [0.503 to 7.455 p=0.021]); anterior vs combined 3.777˚ (CI 95%: [-0.099 to 6.853 p= 0.059]) posterior vs combined cues -0.602˚ (CI 95%: [-2.874- 4.078 p=1.00]). Aggregated data from tests 1 and 2: anterior vs posterior 4.240° (CI 95%: [1.213 to 7.267 p=0.003]); anterior vs posterior 3.756° (95%CI: [0.729 to 6.783 p=0.009]); posterior vs combined-6.48° (95% CI: [-3.511 to 2.542 p=1.000]). Principal results Study 2: anterior vs posterior 3.936˚ (95%CI: [0.863 to 7.008p=0.008]; 4.946˚ anterior vs combined (95%CI: [1.873 to 8.018 p=0.001]); posterior vs combined 1.010° (95%CI: -[2.062 to 4.082 p=1.000]). Aggregated analysis was anterior vs posterior 3.703˚ (95%CI: [1.639 to 5.761 p=0.000]); anterior vs combined 5.089˚ (95%CI: [3.0287 to 7.1503 p=0.000]) and posterior and combined 1.389° (95%CI: [-0.672 to 3.450 p=0.309]). Secondary results: 2-D RTUS and the AUI were found to be suitable for investigating selective PFM contraction. Posture: supine vs standing (difference) 9.496˚ (p=0.000); (posture did not affect absolute AUI). Three continent (13%) and 2 incontinent (7%) subjects were unable to selectively contract the PFM. Cue preference in both studies was posterior or combined. Conclusions: AUI was significantly narrower/optimal when instruction for PFM contraction included a posterior cue, in both continent and stress incontinent women. This is proposed to be due to optimal recruitment of puborectalis. Puborectalis may be more important in urinary continence than widely recognized. This study has provided seminal information with respect to optimal cue to contraction for a PFM contraction and will change practice. Investigation of the potential impact of these findings clinically is required. It is proposed that further understanding will lead to standardisation of PFM instruction, ease of comparability between PFM research studies, and will clarify PFM instructions for the media and lay public.