Both response to intervention (RTI) and recognition and response systems recommend the use of evidence-based teaching strategies and individualized data collection to monitor the students' response to such strategies. In addition to the efficacy of interventions, individual stakeholders should have a voice in which intervention is implemented. Constant prompt delay and progressive prompt delay procedures have been routinely implemented and have been proven to be effective at teaching important skills to a variety populations; however, no objective data has been reported on the stakeholders' preference for such procedures. Thus, the purpose of the present study was to evaluate the relative efficacy of as well as the relative preference for prompt delay procedures. Four preschool children experienced three teaching conditions: constant prompt delay, progressive prompt delay, and a control condition. A multi-element design was used to evaluate the relative efficacy of the prompt delay procedures at teaching pre-academic tasks while a modified concurrent chains arrangement was used to evaluate each child's relative preference for each teaching strategy. The results for efficacy of and preference for prompt delay procedures were idiosyncratic for all participants. These results as well implication of the results are discussed.

Research on exotic dancers as a population indicates that exotic dancers may be a high risk population due to correlations of substance abuse and risky sexual behavior with the profession, (CDC, 2015; Sherman et. al, 2011; Reuben et. al, 2011; Forsyth & Deshotels, 1997). In delay discounting research, it has been demonstrated that populations of individuals who engage in risky sexual behavior and abuse substances have steeper rates of discounting on a delay discounting task compared to their peers (Moreira et. al, 2015; Jones et. al, 2015: Celio et al., 2016). Steeper rates of discounting indicate an increased degree of preference for smaller-sooner reward versus larger-later reward as measured by a discounting survey task with hypothetical monetary rewards and may indicate higher rates of impulsivity (Moller et al., 2001). This study sought to determine if exotic dancers delayed more steeply than restaurant worker peers. Results indicate that at longer delays, exotic dancers discount more steeply than their restaurant worker peers, which may indicate a higher degree of impulsivity among exotic dancers as a population..

This thesis contains some results on the behavior of a delay differential equation (DDE) with two delays, at a Hopf bifurcation, for the nonzero equilibrium, using the growth rate, r, as bifurcation parameter. This DDE is a model for population growth, incorporating a maturation delay, and a second delay in the harvesting term. Considering a Taylor expansion of the non-dimensionalized model, we find a region of stability for the nonzero equilibrium, after which we find a pair of ODEs which help define the flow on the center manifold. We then find an expression for the first Lypapunov coefficient, which changes sign, so we also find the second Lyapunov coefficient, allowing us to predict multi-stability in the model. Numerical simulations provide examples of the behavior expected. For a similar model with one delay (PMC model), we prove the Hopf bifurcation at the nonzero equilibrium is always supercritical.

Background: Research on communication intervention with young children provides support for the involvement of primary caregivers in their child’s language intervention (Kaiser, & Roberts, 2011; Roberts, & Kaiser, 2011). Research suggests that the perceptions of these caregivers regarding their child’s language development and their role in the language development process are important to their willingness to use intervention strategies (Kaiser, & Hancock, 2003; Leffel, & Suskind, 2013). Furthermore, studies suggest that the severity of child language difficulties may impact on these perceptions (Brady et al., 2006; Romski et al., 2011). However, there is a lack of research on how primary caregivers from non-Western, non-English-speaking backgrounds perceive their child’s language development and understand their role. Aims: The study investigated the perceptions of isiXhosa-speaking primary caregivers of children who receive speech-language therapy regarding their child’s language development across three expressive language groups (i.e. not speaking, speaking in single words and phrases, speaking in sentences). Perceptions on the basis of duration and frequency of the speech-language therapy, and child age are also described. Methods: Thirty primary caregivers of young children (30 to 70 months) completed the South African Caregiver Perception of Language Development (SA-CPOLD) in a structured interview format using the Talking Mats™ visual framework (Murphy, & Boa, 2012). These results were compared across three child expressive language groups, as determined by scores on the Mullen Scale of Early Learning, and language sample analysis data (i.e. mean length of utterance and number of different words). Results: The primary caregivers of the children who were speaking in either single words and phrases or speaking in sentences demonstrated more positive perceptions than caregivers of children who were not speaking, although this did not reach a conventional level of significance. Caregivers of children across the three expressive language groups acknowledged their child’s language difficulties, however primary caregivers of the children who were non-speaking agreed more with statements related to their child’s difficulty. Perceptions did not appear to differ on the additional variables (i.e. duration and frequency of speech-language therapy, and child age). Conclusion: The results of the present study suggest that isiXhosa-speaking caregivers’ perceptions of their child’s language skills are related to their expressive language skills to some extent and that these caregivers are able to accurately report on their child’s language difficulties. Keywords: caregiver perceptions, disability and developmental delays, early language intervention, isiXhosa, language delays, South Africa / Mini Dissertation (MA)--University of Pretoria, 2019. / Centre for Augmentative and Alternative Communication (CAAC) / MAAC / Unrestricted

No description available.

Performance and stability of bilateral teleoperation control systems are adversely affected by variations in environment dynamics and time delay in communication channel. Prior relevant research in the literature has mainly yielded control algorithms that sacrifice performance in order to guarantee robust stability. In contrast, this thesis proposes methods to deal with these two main problems in order to maintain the stability without compromising performance. To handle changes in environment dynamics, a multiple model controller for teleoperation is introduced. It is assumed that the dynamics of the environment are governed by a model from a finite set of environment models at any given time with Markov chain switching between these models. The first-order generalized pseudo-Bayesian (GPB1) multi-model estimation technique is used to identify the effective model at each time step given the sensory observations. The control action is a weighted sum of mode-based control laws that are designed for each mode of operation. The second major problem in teleoperation systems that this thesis deals with is communication channel time delay. The constant time-delay problem is solved using two different methods, i.e. discrete-time and continuous-time predictive type Linear Quadratic Gaussian (LQG) controllers. The treatment of the problem in the discrete-time domain allows for the development of a finite dimension state-space model that explicitly encompasses the time delay. The robustness of the controller with respect to uncertainty in the system parameters is examined via Nyquist analysis. In continuous-time, a modified state transformation is proposed to obtain delay-free dynamics based on the original dynamics with delayed inputs and outputs. The application of the continuous-time LQG control synthesis to these reduced dynamics yields a control law that guarantees closed-loop stability and performance. Mode-based controllers are designed for each phase of operation, i.e. free motion/soft contact and contact with rigid environments. Performance objectives such as position tracking and tool impedance shaping for free motion/soft contact, as well as position and force tracking for contact with rigid environments are incorporated into the LQG control design framework. Simulation and experimental results are presented for each of the proposed controllers in various scenarios. These results demonstrate the effectiveness of the proposed methods in providing a stable transparent interface for teleoperation in free motion and in contact with rigid environments. / Thesis / Master of Applied Science (MASc)

Network Address Translation (NAT) is a method by which Internet Protocol (IP) addresses are translated from one group to another, in a manner transparent to the end users. It translates the source and destination addresses and ports in the Internet Protocol datagram. There are several benefits for using NAT. NAT can be installed without changes to hosts or routers, it allows reuse of globally routable addresses, it facilitates easy migration or addition of new networks and it provides a method to keep private network addresses hidden from the outside world. NAT, however, is a processor- and memory-intensive activity for any device that implements it. This is because NAT involves reading from and writing to the header and payload information of every IP packet to do the address translation, a performance-intensive activity. It causes an increase in Central Processing Unit (CPU) and memory utilization and may impair throughput and increase the latency experienced by a packet. Thus, understanding the performance impact of NAT on a network device (in particular, a router) becomes an important factor when implementing NAT in any live network. This thesis aims to understand and quantify the impact of Network Address Translation on a network router by doing a series of performance tests after specifying the performance parameters to measure and, then, clearly defining the performance testing methodology that is used to study each of the performance parameters. After a discussion of previous research, the measurement system and subsequent measurement results are described. / Master of Science

Measurement studies have linked paraspinal muscle reflexes to low back pain. However, the role of reflexes in stabilizing the spine is not clear. Previous studies enlisted biomechanical models to aid in understanding of how intrinsic stiffness stabilizes the spine. This work expands these previous studies by modeling the neuromuscular dynamic control of the spine. The presence of delay in the reflexive system limits the availability of traditional stability analyses. However it is possible to investigate how reflex delay affects stability of the spine model using methods in linear time delayed stability. Such analyses find the maximum reflex delay, i.e., the delay margin for which stability is possible. Therefore a biomechanical model of the spine was developed that used these methods for stability. The model was able to demonstrate how reflex gains and delays affect stability. It was shown that increased proportional reflex gain reduced the amount of co-contraction required for stability. However, increased reflex gain required a reduced delay margin of the system. Differential reflex gain had no effect on the amount of co-contraction required for stability. However, it was shown to increase the delay margin for small gains. As the differential reflex gain approached the magnitude of intrinsic muscle damping the trend was reversed, and increased gain caused the delay margin to approach zero. Increased intrinsic muscle damping did not affect the minimum co-contraction required for stability, but was shown to increase the delay margin in all cases. This study provided a theoretical explanation for the role of reflexes in stabilizing the spine. Results agree with the trends in the published literature regarding patients with low-back pain. Specifically, these patients demonstrate abnormally larger reflex delay. To maintain stability, atypically small reflex gain is necessary. Compensatory co-contraction is required to offset the small reflex gain. Co-contraction and instability is observed in low back pain patients. The results presented here agree with measurement studies, and should aid in the development of hypotheses for future measurement studies. / Master of Science

Delay differential equations (DDEs) are often used to model systems with time-delayed effects, and they have found applications in fields such as climate dynamics, biosciences, engineering, and control theory. In contrast to ordinary differential equations (ODEs), the phase space associated even with a scalar DDE is infinite-dimensional. Oftentimes, it is desirable to have low-dimensional ODE systems that capture qualitative features as well as approximate certain quantitative aspects of the DDE dynamics. In this thesis, we present a Galerkin scheme for a broad class of DDEs and derive convergence results for this scheme. In contrast to other Galerkin schemes devised in the DDE literature, the main new ingredient here is the use of the so called Koornwinder polynomials, which are orthogonal polynomials under an inner product with a point mass. A main advantage of using such polynomials is that they live in the domain of the underlying linear operator, which arguably simplifies the related numerical treatments. The obtained results generalize a previous work to the case of DDEs with multiply delays in the linear terms, either discrete or distributed, or both. We also consider the more challenging case of discrete delays in the nonlinearity and obtain a convergence result by assuming additional assumptions about the Galerkin approximations of the linearized systems. / Master of Science / Delay differential equations (DDEs) are equations that are commonly used to model systems with time-delayed effects. DDEs have found applications in fields such as climate dynamics, biosciences, engineering, and control theory. However, the solutions to these equations can be dicult to approximate. In a previous paper, a method to approximate certain types of DDEs was described. In this thesis, it is shown that this method may also approximate more general types of DDEs.

<p>Timing-related defects are becoming increasingly important in nanometer-technology integrated circuits (ICs). Small delay variations induced by crosstalk, process variations, power-supply noise, as well as resistive opens and shorts can potentially cause timing failures in a design, thereby leading to quality and reliability concerns. All these effects are noticeable in today's technologies and they are likely to become more prominent in the next-generation process technologies~\cite{itrs2007}.</p><p>The detection of small-delay defects (SDDs) is difficult because of the small size of the introduced delay. Although the delay introduced by each SDD is small, the overall impact can be significant if the target path is critical, has low slack, or includes many SDDs. The overall delay of the path may become larger than the clock period, causing circuit failure or temporarily incorrect results. As a result, the detection of SDDs typically requires fault excitation through least-slack paths. However, widely-used automatic test-pattern generation (ATPG) techniques are not effective at exciting small delay defects. On the other hand, the usage of commercially available timing-aware tools is expensive in terms of pattern count inflation and very high test-generation times. Furthermore, these tools do not target real physical defects.</p><p>SDDs are induced not only by physical defects, but also by run-time variations such as crosstalk and power-supply noise. These variations are ignored by today's commercial ATPG tools. As a result, new methods are required for comprehensive coverage of SDDs.</p><p>Test data volume and test application time are also major concerns for large industrial circuits. In recent years, many compression techniques have been proposed and evaluated using industrial designs. However, these methods do not target sequence- or timing-dependent failures while compressing the test patterns. Since timing-related failures in high-performance integrated circuits are now increasingly dominated by SDDs, it is necessary to develop timing-aware compression techniques.</p><p>This thesis addresses the problem of selecting the most effective test patterns for detecting SDDs. A new gate and interconnect delay-defect probability measure is defined to model delay variations for nanometer technologies. The proposed technique intelligently selects the best set of patterns for SDD detection from a large pattern set generated using timing-unaware ATPG. It offers significantly lower computational complexity and it excites a larger number of long paths compared to previously proposed timing-aware ATPG methods. It is shown that, for the same pattern count, the selected patterns are more effective than timing-aware ATPG for detecting small delay defects caused by resistive shorts, resistive opens, process variations, and crosstalk. The proposed technique also serves as the basis for an efficient SDD-aware test compression scheme. The effectiveness of the proposed technique is highlighted for industrial circuits.</p><p>In summary, this research is targeted at the testing of SDDs caused by various underlying reasons. The proposed techniques are expected to generate high-quality and compact test patterns for various types of defects in nanometer ICs. The results of this research are expected to provide low-cost and effective test methods for nanometer devices, and they will lead to higher shipped-product quality.</p> / Dissertation