The use of fibre-reinforced polymer (FRP) as an internal reinforcement for concrete has many advantages over steel, most notably lack of corrosion which is considered to be a major problem for structures incorporating steel. In Europe alone, it is estimated that the annual repairing and maintenance costs associated with steel corrosion in infrastructure are around £20 billion (Nadjai et al., 2005). Despite of its corrosion resistance, the widespread use of FRP as an internal reinforcement for concrete was hindered due to its relatively weak performance at elevated temperatures, such as in the event of fire. Under heating, the polymer matrix in FRP softens, which causes bond degrading between reinforcement and concrete. The softening of polymer matrices occurs around their glass transition temperatures, which is typically in the range of 65– 150 °C. The sensitivity of FRP bond to temperature is recognised in design guidelines, therefore many advise against utilising FRP as an internal reinforcement for concrete in structures where fire performance is critical. On the other hand, fibres, the other component of FRP, can tolerate temperatures much higher than polymer matrices. This research investigates a new design for FRP internal reinforcement, which exploits the fact that the FRP fibres in general and carbon fibres in particular are capable of sustaining a large proportion of their original strength at high temperatures. Instead of the traditional way of using separate bars, FRP reinforcement was made as closed loops produced through the continuous winding of carbon fibre tows. When the surface bond degrades at elevated temperatures, interaction with concrete can still be provided through bearing at loop ends. The concept of FRP loops was investigated through a series of experimental work. Firstly, the performance of carbon FRP (CFRP) loops was evaluated through a series of push-off tests in which specimens consisting of CFRP loops bridging two concrete cubes were tested in pull-out using hydraulic jacks. Specimens with straight and hooked reinforcement were produced as well for comparison. A total number of 18 specimens were tested at ambient temperature, glass transition temperature (Tg), and above Tg. Results showed that while at ambient temperature there was no distinction in performance. At elevated temperatures, CFRP loops developed strength about three times higher than specimens with straight or hooked bars. Also, while failure mode occurred due to de-bond in the case of straight and hooked reinforcement, rupture failure occurred with CFRP loops. For better demonstration of the concept in more realistic conditions, four-point bending tests were conducted upon 28 beam specimens reinforced either with CFRP loops or straight bars as flexural reinforcement. Beams were tested under monotonic loading at ambient temperature, or under sustained loads with localised heating over the midspan region that contained the reinforcement overlaps. The benefit of CFRP loops became evident in the elevated temperature tests. Beam specimens with spliced straight bars failed due to debonding after a short period (up to 15 minutes) of fire exposure. Conversely, the fire endurance increased four to five times when CFRP loop reinforcement was used. Unlike straight bars, debonding failure was avoided as failure occurred due to reinforcement rupture. The overlap length of the CFRP loops was found to be important in the order for the loop to develop full capacity. Premature failure can occur with short overlap length due to shear off concrete within the overlap zone. The presence of transverse reinforcement increases confinement levels for reinforcement, so the bond failure of straight bars at ambient temperature testing was eliminated when stirrups were provided. However, at elevated temperatures straight bars failed by pull-out even in presence of transverse reinforcement. To facilitate design with CFRP loops, a numerical analysis tool was developed to calculate the bond stress-slip response of reinforcement at ambient and elevated temperatures. A Matlab programme was designed based on a one-dimensional analytical model for steel. The bond law was modified to be used for CFRP reinforcement. Other analytical models from the literature to account for bond degradation with temperature and tensile strength of curved FRP were also utilised. The developed Matlab code has the capability of producing slip, axial stress, and bond stress distribution along reinforcement. The novel FRP loop reinforcement was demonstrated to be a promising solution for enhancing the fire performance of CFRP internal reinforcement at elevated temperatures. It contributes to removing a major obstacle preventing widespread use of FRP-reinforced concrete, and paves the way for CFRP reinforcement to be used in situations where fire performance is critical.

Older adults often engage in few activities, for short periods of time, and typically engage with one item without switching to other items. The purposes of this study were (a) to further evaluate the MSWO preference assessment as well as the utility of the brief free-operant presentation method with older adults with dementia to identify preferred activities, (b) to determine if non-variable selection during a free operant preference assessment was due to repetitive behavior through concurrent engagement analyses, and (c) to determine the reinforcing effectiveness of stimuli identified via the single-array MSWO and free operant preference assessments through a reinforcer assessment. The results suggest that for 6 of the 7 participants the free operant was a better predictor for time allocation and engagement with a preferred activity. The results suggest that the single array MSWO was not as predictive of time allocation or engagement as the free operant, resulting in false positives. The results also suggest that individuals not switching items may be a result of the environment rather than a symptom of dementia (repetitive behavior), showing that it was not that the participants could not switch, but rather that they chose not to switch.

Research on impulsivity has focused on the choices between sooner, smaller stimuli versus larger later stimuli. More recent methods that have studied health choices compared temporal and probability discounting tasks between control groups and a comparison group such as smokers, obese individuals, alcoholics, etc. While correlations have been derived between responses on discounting tasks and selection of actual monetary reinforcers, research has not been expanded to question choices pertaining directly to the targeted problem. A technology that reliably assesses choices directly related to these illnesses has yet to be developed. The current study attempted to expand on the technology of discounting by applying it to choices related to healthy eating. 11 participants completed a cross commodity health discounting survey and average proportion area under the curve (AUC) was calculated for survey 1 (M = .41) and survey 2 (M = .21) Correlations between weight and proportion AUC (r = 0.69), income and proportion AUC (r = -0.32), and age and proportion AUC (r = -0.40) were determined. Methodological error that altered 2 variables (hypothetical weight and weight loss option) between surveys limited direct comparisons between survey. Implications of data derived from such error were discussed.

The problem of this study is to determine the feasibility of using an operant treatment procedure to ameliorate several manifestations of depression. The purpose is to apply contingent positive reinforcement to the detection of nondepressive thoughts and to examine the effects of this procedure upon the frequency of nondepressive thoughts, idiosyncratic depressive manifestations, and scores on the Depression Inventory.

In most industrialized countries, significant future activity in the construction sector will be related to repair and rehabilitation of aging infrastructure. This will require use of durable and high performance repair materials. Among various mechanisms cited for lack of durability in repairs, early-age shrinkage cracking in overlay materials is of utmost importance. Fiber-reinforcement can be used to alleviate some of the issues related to plastic shrinkage. However, quantifying the performance of cement-based composites under restrained shrinkage conditions remains an issue. Various test techniques are available to measure free and restrained shrinkage, but do not simulate the real constraint imposed by the substrate on the overlay. In this dissertation, an innovative test method called the bonded overlay technique is described. An overlay of fiber-reinforced material to be tested is cast directly on a substrate, and the entire assembly is subjected to controlled drying. Cracking in the overlay is then monitored and characterized. During the development of this test method, instrumentation was included to enable measurement of the crack propagation rate using image analysis, evaporation rate, heat development, and strain using embedded sensors. Using the above technique, the effect of mix proportion including variables such as water-cement ratio (w/c), sand-cement ratio (s/c), and coarse aggregate content were studied. An increase in w/c from 0.35 to 0.6 significantly increased the total cracking. Addition of coarse aggregates reduced shrinkage cracking, however, for the range of s/c investigated, no definite conclusions could be drawn. Mixes with 0-20% fly ash and a 7 lit/m3 dosage of shrinkage reducing admixtures indicated no significant reduction in cracking. The influence of fiber geometry on cracking in overlays was also investigated. Fiber types included different sizes of polypropylene and cellulose fibers and one type of glass fiber (volume fraction ranging between 0-0.4%). Glass fibers at a small dosage of 0.1% were the most efficient fiber and completely eliminated cracking. Of the two field projects considered: one was a plaza deck at the UBC Aquatic Center, where cellulose fibers were used, and the second at the UBC ChemBioE building, where polypropylene fibers were used in slabs-on-grade. Both overlays were instrumented with strain sensors, data from which were monitored over the Internet. Results clearly indicated that fibers reduced the strain development in fiber-reinforced overlays when compared to un-reinforced overlays. An energy-based fracture model was proposed to predict maximum crack widths and in a second study, an equation was proposed to correlate early-age shrinkage and flexural toughness of cellulose fibers. In both models, a reasonable correlation with the test data was observed. In addition, factorial design method was used and a mathematical model was proposed to correlate different variables such as w/c, s/c, and fiber dosage. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

No description available.

The effects of thinning to intermittent reinforcement with various reward-associated messages were investigated using an alternating treatments design. Three children who displayed high rates of disruptive classroom behavior were encouraged to be on-task using a FI 30" schedule of token reinforcement. Once the children reached a preset criterion of on-task behavior, the tokens were thinned to a leaner FI 5' schedule and different reward-associated messages concerning the reinforcement reduction were simultaneously interspersed. Three conditions were compared and alternated from one session to the next. One condition attributed the reinforcement reduction to increased competence (e.g., "You're doing so well you don't need tokens"); a second attributed reductions to factors extraneous to behavior (e.g. therapist forgetful ness); in the third condition no information was given about the schedule change. In a final extinction phase tokens were completely withdrawn. Results indicated that for two subjects the reward-associated messages affected rates of on-task behavior differentially during both thinning and extinction sessions. Better short-term maintenance was obtained during thinning and extinction phases when the reward messages stressed personal competence rather than extraneous reasons for the reduction in reinforcers. The results are interpreted in terms of reward communication theory. Practical implications are also discussed.

<div>Here, we explore methods of counter autonomy defense for aerial autonomous multi-agent systems. First, the case is made for vast capabilities made possible by these systems. Recognizing that widespread use is likely on the horizon, we assert that it will be necessary for system designers to give appropriate attention to the security and vulnerabilities of such systems. We propose a method of learning-based resilient control for the multi-agent formation tracking problem, which uses reinforcement learning and neural networks to attenuate adversarial inputs and ensure proper operation. We also devise a learning-based method of cyber-physical attack detection for UAVs, which requires no formal system dynamics model yet learns to recognize abnormal behavior. We also utilize similar techniques for time signal analysis to achieve epileptic seizure prediction. Finally, a blockchain-based method for network security in the presence of Byzantine agents is explored.</div>

Basal reinforcement, where high tensile geogrids are employed beneath structures, is becoming an increasingly accepted construction technique along the eastern coast of southern Africa. The presence of compressible, soft, thin and shallow clay horizons usually associated with complex estuarine or lagoonal deposits are a major consideration when using basal reinforcement as a founding technique. Basal reinforcement involves the use of high tensile strength geogrids beneath a structure to form a reinforced sand foundation. Deformation behaviour under loading is an important component of stability analysis of earth structures. If reinforcement is used, the mechanisms become altered. Geotechnical centrifuge modelling is a unique physical modelling technique, as it allows replication of in situ stresses, which is most important because soil behaviour is a function of stress. This is achieved by placing the model at the end of the centrifuge arm, and subjecting it to an increased gravitational field, which creates the correct stress distribution in the model. Centrifuge modelling provides an appropriate technique to observe the behaviour of compressible, soft, thin and shallow clay horizons when basal reinforcement is utilized. An appropriate centrifuge model was constructed and compared the behaviour of the clay horizon under unreinforced and reinforced conditions. Reinforcement configurations were adjusted to observe the influence of additional geogrid layers, and extension of the width of the reinforcement. It was found that deformation behaviour is distinctly different between unreinforced and reinforced tests. Vertical deformation in the unreinforced test localised to the region directly beneath the platform, with little lateral disturbance to the clay horizon beyond the platform edge. As such, the sand directly beneath the platform acts as a deeper rigid platform. The deformation behaviour of the clay horizon changes with the inclusion of reinforcement. When reinforcement is included a wider portion of clay is deformed. The lateral width of this deformation zone is controlled by the width of the reinforcement, as the applied load is spread. A ‘wide-slab’ effect is evident with an increase in the geogrid width, as the tensioned membrane-effect is mobilised to increase the capacity of the reinforced foundation sand. This results in a wider portion of the clay deforming. Addition of geogrid reinforcement to the sand foundation under a wide platform load enhances deformation of the clay, but has the advantage of an increased load-bearing capacity of the system. Furthermore, the addition of multiple layers of reinforcement contributes to this increase in load-bearing capacity. Additionally, increasing the installation width of the reinforcement contributes to an increased vertical load-bearing capacity. However, this resultant increase is only mobilised after a certain amount of vertical displacement. This is likely due to the reinforcement requiring a certain amount of vertical displacement to mobilise tension in order to support the applied load. The behaviour of a thin compressible clay horizon changes with the inclusion of reinforcement under a wide platform load. The deformation behaviour of the clay is increased by additional layers of reinforcement as well as an increase in the width of the reinforcement. However, the increase in deformation comes at the benefit of an increased vertical load-bearing capacity of the reinforced foundation sand. / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / Geology / unrestricted

The present experiment investigated the application of Green and Swets (1966) signal-detection theory to undesirable behavior as a method of reducing unwanted behaviors using reinforcement and extinction. This experiment investigated the use of this stimulus control technique to reduce undesirable behaviors using a multiple-baseline design. Once the cue for a target behavior was established and maintained, the use of the verbal cue was reduced in frequency and the rate of unprompted undesirable behavior was recorded. Generalization was tested across multiple people. Data for this experiment showed that undesirable behavior could be reduced by altering the stimulus control that maintained it.