Several new multiuser detectors are developed for different direct-sequence codedivision multiple-access (DS-CDMA) application environments. The first detector is based on a semidefinite-programming (SDP) relaxation technique. In this detector, maximum likelihood (ML) detection is achieved by 'relaxing' the associated combinatorial problem into an SDP problem, which leads to a detector of polynomial complexity. It is shown that the SDP-relaxation (SDPR) based detector can be obtained by solving a dual SDP problem which leads to improved efficiency. Computer simulations demonstrate that the SDPR detector offers near-optimal performance with much reduced computational complexity compared with that of the ML detector proposed by Verdu for both synchronous and asynchronous DS-CDMA systems. The second detector is based on a recursive convex programming (RCP) approach. In this detector, ML detection is carried out in two steps: first, the combinatorial problem associated with ML detection is relaxed to a convex programming problem, and then a recursive approach is used to obtain an approximate solution for ML detection. Efficient unconstrained relaxation approach is proposed for the proposed detector to reduce the involved computational complexity. Computer simulations demonstrate that the proposed detectors offer near-optimal detection performance which is superior to that offered by many other suboptimal detectors including the SDPR detector. However, the computational complexity involved in the proposed detectors is much lower relative to that involved in Verdu's ML detector as well as our SDPR detector. The third detector entails a subspace estimation-based constrained optimization approach for channel estimation in DS-CDMA systems with multipath propagation channels. The proposed approach offers an improved approximation for the noise iii subspace compared with that offered by several existing algorithms. Computer simulations show that the performance of the proposed detector offers nearly the same performance as that of existing subspace detectors but leads to a significant reduction in the amount of computation. Relative to some existing constrained optimization methods, the proposed detector offers a significantly improved performance while requiring a comparable amount of computation. The fourth detector is proposed based on a vector constant-modulus (VCM) approach. This detector is designed for DS-CDMA systems with multipath propagation channels where the effective signatures observed at receiver are distorted by multipath propagation and aliasing concurrently. In this detector, detection is carried out by solving a linear constrained optimization problem whose objective function is formulated based on the VCM criterion. Two adaptation algorithms, namely, the constrained stochastic gradient algorithm and the recursive vector constant-modulus algorithm, are developed. Analysis are presented to investigate the performance of the proposed detector. Computer simulations show that the proposed detectors are able to suppress multiuser interference and inter-symbol interference effectively. More importantly, they offer robust detection performance against the effective signature distortion caused by aliasing at the receiver.

The need for Shared Situational Awareness (SSA) in accomplishing joint missions by coalition militaries, law enforcement, the intelligence community, and the private sector creates a unique challenge to providing access control. In this thesis we investigate the capabilities and limitations of Role-Based Access Control (RBAC) to control the dissemination of SSA in a coalition environment. Our case study is that of controlling access to SSA in the Maritime Domain Awareness (MDA) environment. MDA exemplifies both rapid change in membership of coalitions and the roles of coalition participants. We explore the access policy and roles played by the participants in the MDA environment, in addition to the characteristics of those roles. We make use of feasible scenarios to provide us with a base for applying models to the situation. The models that are applied to the scenario provide the formal methods that prove that RBAC policies and derivatives such as Distributed Role Based Access Control (DRBAC), Coalition Based Access Control (CBAC) and Temporal Role Based Access Control (TRBAC) can be used in conjunction with the Information Broker (IB) concept to provide adequate access control policies.

In this dissertation, direct-sequence code-division multiple access (DS-CDMA) systems with multiuser detectors used at receiver are investigated and two kinds of multiuser detectors are developed for DS-CDMA systems. In the investigation of DS-CDMA systems using multiuser detectors at receiver, a study on the performance of the system is presented, where heterogeneous traffic with different transmission rates and quality of service (QoS) requirements is supported. The effects of some realistic factors, such as imperfect power control and the existence of multiple cells, on the system performance are studied. In addition, algorithms are proposed to deal with the forward link power allocation problem based on the measurements of random characteristics of the received signals. This power allocation problem is formulated as a constrained optimization problem. To make the problem easy to solve, an additional appropriate constraint is proposed. Two methods are developed to identify the feasible region of this constrained optimization problem. The first proposed multiuser detector is an adaptive minimum mean-squared-error (MMSE) detector. Particularly, it is desirable for the cases where communication channels have severe near-far problem, and thus the convergence rates of adaptive MMSE detectors for users with different power are quite different. To improve the convergence rates of adaptive MMSE detectors for weak power users, the interference effects of the strong power user signals are subtracted from the received signal successively. The method to estimate the parameters required in the proposed detector is also developed. It is shown that the proposed detector achieves fast convergence rates in various near-far scenarios. Other studies conducted include the transient mean-squared-error (MSE) analysis to explain the different convergence rates of adaptive MMSE detectors for users with different power, and the bit-error-rate (BER) performance analysis for the proposed detector. The second proposed multiuser detector is a set of semi-blind linear parallel interference cancellation (PIC) detectors for the reverse link of multiple-cell systems, where only information about intra-cell users is available. To decrease the interference from inter-cell users whose information is unavailable to the receiver, the inter-cell user signal subspace is identified first by making use of the available information about intra-cell users. The eigenvectors and eigenvalues of this signal subspace are then used in the traditional linear PIC structure, in place of the unknown inter-cell users’ signature codes and signal amplitudes. Based on this idea, three detection schemes are proposed. In addition, an efficient adaptation implementation method is developed, and the performance of the proposed detectors is studied. The proposed detectors are shown to be suitable for practical implementations and have satisfactory performance. / Graduate

Class of 2017 Abstract / Objectives: (1) To assess the access to and quality of primary care for patients living with a psychiatric condition(s). (2) To identify demographic factors that may influence the access and quality of primary care services. Methods: Subjects were recruited at HOPE Inc., a behavioral health resource center, in Tucson, Arizona, during pharmacy student-run health fairs. Participants were surveyed using the Primary Care Assessment Tool (PCAT) a questionnaire developed by Johns Hopkins, which assess four domains of primary care. Participants were also surveyed about demographics, mental health diagnosis and their SMI designation. For objective (1): Descriptive statistics for each domain of the PCAT were performed to assess the level of access and quality of care, including comparison to a hypothesized score. For objective (2): Due to the small sample size only descriptive analysis of the demographic data was performed. Results: A total of 11 subjects were surveyed using the PCAT with an average score of 67.64±12.18. This was higher than the hypothesized score of 46. On average, in all four PCAT domains participants scored higher than the hypothesized, value. The lowest scoring domains were, “Care at first contact - Access” and “Coordination of care” (10.45±3.62, Hypothesized score: 8) and (12.36±5.82, Hypothesized score: 10) respectively. The highest scoring domain was “Care at first contact - utilization” (11.09±1.92, Hypothesized score: 12). Conclusions: This study helped to provide a framework for future studies of primary care services using the PCAT survey.

People make a range of everyday decisions about how and whether to share content with different people, across different platforms and services, during a variety of tasks. These sharing decisions can encompass complex preferences and a variety of access-control dimensions. In this thesis I examine potential methods for improving sharing mechanisms by better understanding the everyday online sharing environment and evaluating a potential sharing tool. I first present two studies that explore how current sharing mechanisms may fall short on social networking sites, leading to suboptimal outcomes such as regret or self censorship. I discuss the implications of these suboptimal outcomes for the design of behavioral nudging tools and the potential for improving the design of selective-sharing mechanisms. I then draw on a third study to explore the broader “ecosystem” of available channels created by the services and platforms people move between and combine to share content in everyday contexts. I examine the role of selective-sharing features in the broader audience-driven and task-driven dynamics that drive sharing decisions in this environment. I discuss the implications of channel choice and dynamics for the design of selective-sharing mechanisms. Using insights from current shortfalls and ecosystem-level dynamics I then present a fourth study examining the potential for adding topic-driven sharing mechanisms to Facebook. I use design mockups and a lab-based interview to explore participants’ hypothetical use cases for such mechanisms. I find that these mechanisms could potentially be useful in a variety of situations, but successful implementation would require accounting for privacy requirements and users’ sharing strategies.

This thesis analyzes the contested struggles for fuelwood extraction and protection around the Borjomi-Kharagauli Protected Areas (BKPA) of central Georgia in light of wider debates over the reconciliation of biodiversity conservation and livelihood security in the developing world. Particular focus is given to conflicts over local peoples’ struggles in accessing fuelwood and the ways and extentto which these struggles are influenced by broader forces. In endeavoring to answer these questions, interviews were conducted with local people living on the margin of BKPA as well as with conservation authorities involved in the development and ongoing management of the park. The results of theresearch suggest that considerable obstacles to fuelwood access remain despite BKPA policies permitting fuelwood extraction in several of the studied villages. Furthermore, the association of nonstate actors in the development of BKPA coupled with the lack of participation of local people inongoing management provoke questions of legitimacy and governance. The study underscores that incontexts of widespread poverty and highly subsistence-based livelihoods, participatory management embodies the most effective and socially just approach to conservation.

Greater environmental considerations and the desire to reduce pollution overflows to watercourses are requiring engineers to develop a better understanding of the processes involved in pollution transport through sewer networks. Furthermore, developments in modelling techniques and computer power are allowing urban drainage modellers to increase the complexity of their software and so demand additional data that can be incorporated. Presently, an important aspect is quantifying the retention time and dispersion of pollutants entering an urban drainage system. Manholes provide a means of sewer access for maintenance and inspection. Under storm flow conditions they are liable to surcharge above the level of the pipe soffit. This creates a storage volume that has an impact on the longitudinal dispersion and travel time of soluble pollutants in sewer systems. A laboratory investigation has been completed to quantify these effects for various manhole configurations. These include step heights between the inlet and outlet pipes, benching and extreme high surcharge conditions. In addition, re·analysis of previously acquired data has allowed variations in manhole diameter to be considered. Numerical modelling using computational fluid dynamics, combined with laser light sheet visualisation of the flow structures within manholes, has provided greater insight into the processes causing longitudinal dispersion. The coefficients required for two existing longitudinal dispersion models, the advection dispersion equation and the aggregated dead zone model, have been determined by means of an optimisation process. This has been undertaken with computer software specifically written for the purpose. The technique adopted for optimisation is fully detailed. Final conclusions regarding the longitudinal dispersion due to surcharged manholes are presented.

Since 2004, the number of people living with HIV (PLWH) has steadily increased by about 5% and currently, the number in Texas is about 86,000. Though the National HIV/AIDS Strategic Plan seeks to ensure “unfettered access to quality healthcare”, barriers to access still exist especially among minority populations. This study examines the relationship between HIV infection rates and the geographic location of HIV service centers with a focus on 4 counties: namely, Dallas, Denton, Harris and Tarrant. The goal is to show whether there is a spatial mismatch between HIV rates and service providers. Are service facilities located in zip codes where they are most needed? Using the vulnerability framework and the Inverse Care Law (ICL), we address the research question using demographic variables (race/ethnicity, sex, poverty, education attainment) and HIV data. Our results show that extreme vulnerable zip codes have high HIV rates and closest proximity to HIV service providers.

This dissertation is focused on multi-service and direct sequence code division multiple access (DS/CDMA) wireless cellular systems. The reverse link performance of a slotted DS/CDMA cellular system with multi-service traffic is analyzed. Services with/without packet retransmission to meet their Quality of Service, share the entire bandwidth. Packet failure probabilities and packet delay are obtained based on analyzing the mutual interaction among services. The impacts of power level allocation and power control error of services on capacity, throughput and delay are analyzed under given Quality of Service. The system capacity is maximized by appropriate power allocation. The impact of power control error on capacity is dependent on whether packet retransmission is allowed or not. Admission control policies for multi-service systems are proposed and analyzed. Both nonprioritized and prioritized admission control are studied. Services difference in terms of resource requirement and degree of importance are considered. Analytical models are developed. Blocking probability of each type of calls are found under given amount of traffic. Fair access by soft capacity is addressed. The cost of protecting certain type(s) of calls on the rest of calls is investigated. The impact of traffic distribution on the performance of the policies is also examined. In a hierarchical cellular system, user mobility estimation helps channel assignment so as to reduce the handoff rate and avoid high mobility users travel among small cells. Two different strategies are compared. It is found that when high mobility users are served by overlay macrocells, call drop rate is reduced. Speed estimation error only has limited impact on the system performance. User membership in a cellular CDMA network is simulated based on the estimation of the local mean value of the pilot signal from surrounding base stations. The base station providing strongest pilot local mean controls the mobile station. Simulation is conducted under different fading environments. Two performance measurements are simulated: the number of membership switchings per second and the probability of wrong base station selection. An optimum window length for filtering out Rayleigh fading is found. Simulation results are in good fit with those of analysis. / Graduate

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Commerce, Law and Management, School of Governance, 2014. / The democratisation process of higher education in South Africa commenced in 1994, with the refrains of ‘widening access, broadening participation’ and ‘the doors of education and culture shall be opened’. The deep structural and systemic deficits in the apartheid education system restricted access to higher education based on race, while simultaneously deepening inequalities in the schooling system. Education reform as the transition to democracy commenced, required seismic policy and systemic shifts widely described as an agenda to transform the higher education system. Thus equity of access and success reverberate in the policy documents and reforms undertaken by the government. This research study examined the policy texts and state instruments used to steer the system towards the goal of widening access. Using the conceptual model of Bowe, Ball and Gold (1992) it explored the role of universities in re-interpreting policies, while at the same time focusing on the difficulty of ‘widening access’ given the treacherous legacy of the past. The focus was on a 16 year time-span from 1994–2010, tracing the journey of policy reforms and analysing the quantitative data at the national level of the higher education system. The researcher sought to understand the enormity of the education system problems, while taking into account that changing the course for the country is a major task which would require deep transformation that would not be feasible in a short period. Findings of the research conducted are analysed and discussed during the course of this thesis. The thesis also recommends the adoption of an evaluative framework that would enable government to measure progress in relation to stated goals and inculcate greater accountability by universities.