Showing papers on "Reinforcement published in 2013"

Functional analysis screening for problem behavior maintained by automatic reinforcement.

Abstract: A common finding in previous research is that problem behavior maintained by automatic reinforcement continues to occur in the alone condition of a functional analysis (FA), whereas behavior maintained by social reinforcement typically is extinguished. Thus, the alone condition may represent an efficient screening procedure when maintenance by automatic reinforcement is suspected. We conducted a series of 5-min alone (or no-interaction) probes for 30 cases of problem behavior and compared initial predictions of maintenance or extinction to outcomes obtained in subsequent FAs. Results indicated that data from the screening procedure accurately predicted that problem behavior was maintained by automatic reinforcement in 21 of 22 cases and by social reinforcement in 7 of 8 cases. Thus, results of the screening accurately predicted the function of problem behavior (social vs. automatic reinforcement) in 28 of 30 cases.

Cracking Behavior of Steel Fiber-Reinforced Concrete Members Containing Conventional Reinforcement

Abstract: Uniaxial tension tests were conducted on 12 plain reinforced concrete (RC) and 48 large-scale steel fiber-reinforced concrete (SFRC) specimens, each containing conventional longitudinal reinforcement, to study their cracking and tension-stiffening behavior. The test parameters included fiber volumetric content, fiber length and aspect ratio, conventional reinforcement ratio, and steel reinforcing bar diameter. “Dog-bone” tension tests and bending tests were also performed to quantify the tensile properties of the concrete. It was found that the cracking behavior of SFRC was significantly altered by the presence of conventional reinforcement. Crack spacings and crack widths were influenced by the reinforcement ratio and bar diameter of the conventional reinforcing bar, as well as by the volume fraction and aspect ratio of the steel fiber. Details and results of the experimental investigation are provided and discussed.

Effects of high, low, and thinning rates of alternative reinforcement on response elimination and resurgence.

Abstract: A common treatment for operant problem behavior is alternative reinforcement. When alternative reinforcement is removed or reduced, however, resurgence of the target behavior can occur. Shahan and Sweeney (2011) developed a quantitative model of resurgence based on behavioral momentum theory that suggests higher rates of alternative reinforcement result in faster response elimination and greater resurgence when removed, whereas lower rates of alternative reinforcement result in slower response elimination but are followed by less resurgence. Thus, the present study was designed to examine whether faster target response elimination and less resurgence could be achieved by beginning with a high rate of alternative reinforcement and gradually thinning it such that a low rate is ultimately removed during a simulated treatment lapse. Results showed that high rates of alternative reinforcement were more effective than low or thinning rates at target response suppression but resulted in resurgence when discontinued. Low and thinning rates, on the other hand, were less effective at response suppression but target responding did not increase when alternative reinforcement was discontinued. The quantitative model cannot currently account for the finding that lower-rate alternative reinforcement may not effectively disrupt behavior relative to an extinction only control. Relative advantages of high, low, thinning, or no alternative reinforcement are discussed with respect to suppression of target response rate during treatment, resurgence when alternative reinforcement is removed, and alternative response persistence, while taking into account differences between this animal model and modern applied behavior analytic treatments.

Learning from Limited Demonstrations

Abstract: We propose a Learning from Demonstration (LfD) algorithm which leverages expert data, even if they are very few or inaccurate. We achieve this by using both expert data, as well as reinforcement signals gathered through trial-and-error interactions with the environment. The key idea of our approach, Approximate Policy Iteration with Demonstration (APID), is that expert's suggestions are used to define linear constraints which guide the optimization performed by Approximate Policy Iteration. We prove an upper bound on the Bellman error of the estimate computed by APID at each iteration. Moreover, we show empirically that APID outperforms pure Approximate Policy Iteration, a state-of-the-art LfD algorithm, and supervised learning in a variety of scenarios, including when very few and/or suboptimal demonstrations are available. Our experiments include simulations as well as a real robot path-finding task.

Reinforcement of silica aerogels using silane-end-capped polyurethanes.

Abstract: Proper selection of silane precursors and polymer reinforcements yields more durable and stronger silica aerogels. This paper focuses on the use of silane-end-capped urethane prepolymer and chain-extended polyurethane for reinforcement of silica aerogels. The silane end groups were expected to participate in silica network formation and uniquely determine the amounts of urethanes incorporated into the aerogel network as reinforcement. The aerogels were prepared by one-step sol–gel process from mixed silane precursors tetraethoxysilane, aminopropyltriethoxysilane (APTES), and APTES-end-capped polyurethanes. The morphology and mechanical and surface properties of the resultant aerogels were investigated in addition to elucidation of chemical structures by solid-state 13C and 29Si nuclear magnetic resonance. Modification by 10 wt % APTES-end-capped chain-extended polyurethane yielded a 5-fold increase in compressive modulus and 60% increase in density. APTES-end-capped chain-extended polyurethane was found t...

A component analysis of schedule thinning during functional communication training

Abstract: One limitation of functional communication training (FCT) is that individuals may request reinforcement via the functional communication response (FCR) at exceedingly high rates. Multiple schedules with alternating periods of reinforcement and extinction of the FCR combined with gradually lengthening the extinction-component interval can effectively address this limitation. However, the extent to which each of these components contributes to the effectiveness of the overall approach remains uncertain. In the current investigation, we evaluated the first component by comparing rates of the FCR and problem behavior under mixed and multiple schedules and evaluated the second component by rapidly switching from dense mixed and multiple schedules to lean multiple schedules without gradually thinning the density of reinforcement. Results indicated that multiple schedules decreased the overall rate of reinforcement for the FCR and maintained the strength of the FCR and low rates of problem behavior without gradually thinning the reinforcement schedule.

Reinforcement enhancing effects of nicotine via smoking.

Abstract: Rationale In animals, nicotine enhances reinforcement from stimuli unrelated to nicotine intake. Human research is suggestive but has not clearly shown a similar influence of nicotine.

Shear Behavior of FRP-Reinforced Concrete Deep Beams without Web Reinforcement

Abstract: The shear behavior of four full-scale deep beams reinforced with carbon and glass fiber reinforced polymer (FRP) bars were investigated. The beams were supported over a 3,000-mm span with a projection of 1,000 mm on each side, with a cross section of 300 mm in width and 1,200 mm in depth, and tested to failure under four-point loading. The primary test variables included the longitudinal reinforcement ratio and the reinforcement type. The reinforcement ratio and concrete compressive strength had a clear effect on the ultimate capacity and deflection characteristics while reinforcement type no clear effect of the behavior of the tested beams. The crack patterns, mode of failure, and strains in concrete and reinforcement were also reported. The formation of the tie action was confirmed by the nearly uniform strain distribution in the longitudinal reinforcement. The results are compared to the strut-and-tie model, demonstrating the necessity of including the effect of web reinforcement and the import...

Experimental analysis of precursors to severe problem behavior

Abstract: Some individuals engage in both mild and severe forms of problem behavior. Research has shown that when mild behaviors precede severe behaviors (i.e., the mild behaviors serve as precursors), they can (a) be maintained by the same source of reinforcement as severe behavior and (b) reduce rates of severe behavior observed during assessment. In Study 1, we developed an objective checklist to identify precursors via videotaped trials for 16 subjects who engaged in problem behavior and identified at least 1 precursor for every subject. In Study 2, we conducted separate functional analyses of precursor and severe problem behaviors for 8 subjects, and obtained correspondence between outcomes in 7 cases. In Study 3, we evaluated noncontingent reinforcement schedule thinning plus differential reinforcement of alternative behavior to reduce precursors, increase appropriate behavior, and maintain low rates of severe behavior during 3 treatment analyses for 2 subjects. Results showed that this treatment strategy was effective for behaviors maintained by positive and negative reinforcement.

Behavior of nonwoven-geotextile-reinforced sand and mobilization of reinforcement strain under triaxial compression

Abstract: Laboratory triaxial compression tests were conducted to investigate the stress–strain–volumetric responses of geotextile-reinforced sand and the mobilization and distribution of reinforcement strain/loads and soil–geotextile interface shear stress within reinforced soil. Geotextile-reinforced sand specimens were tested while varying the confining pressures and number of geotextile reinforcement layers. A digital image-processing technique was applied to determine residual tensile strain of the reinforcements after tests and to estimate reinforcement tensile loads. Experimental results indicate that the geotextile reinforcement enhanced peak shear strength and axial strain at failure, and reduced loss of post-peak shear strength. The reinforced specimen had higher shear strength when compared with that of unreinforced soil after deforming by 1–3% of axial strain, which indicates that the geotextile requires a sufficient deformation to mobilize its tensile force to improve the shear strength of re...

Thermoplastic polymer powder

Abstract: A method of modifying a thermoplastic polymer powder. A suspension of thermoplastic polymer powder and reinforcement elements in a liquid is heated within a reaction chamber so that the thermoplastic polymer powder becomes softened and the reinforcement elements migrate into the softened thermoplastic polymer powder to form modified thermoplastic polymer powder. The modified thermoplastic polymer powder is then separated from the liquid. The reinforcement elements have an electromagnetic moment and are subjected to an electromagnetic field as the suspension is heated. The interaction of the electromagnetic field with the electromagnetic moment of the reinforcement elements causes the reinforcement elements to become aligned with the electromagnetic field before they migrate into the powder.

Value learning through reinforcement: The basics of dopamine and reinforcement learning

Abstract: In order to choose advantageously in many circumstances, the values of choice alternatives have to be learned from experience. We provide an introduction to theoretical and experimental work on reinforcement learning, that is, trial-and-error learning to obtain rewards or avoid punishments. We introduce one version, the temporal-difference learning model, and review evidence that its predictions relate to the firing properties of midbrain dopamine neurons and to activity recorded with functional neuroimaging in humans. We also present evidence that this computational and neurophysiological mechanism affects human and animal behavior in decision and conditioning tasks.

Load-Carrying Capacity and Required Reinforcement Strength of Closely Spaced Soil-Geosynthetic Composites

Abstract: In current design methods for reinforced soil walls, it has been tacitly assumed that reinforcement strength and reinforcement spacing play an equal role. This fundamental design assumption has led to the use of larger reinforcement spacing (0.3–1.0 m) in conjunction with stronger reinforcement to reduce construction time. Recent studies, however, have clearly indicated that the role of reinforcement spacing is much more significant than that of reinforcement strength. With closely spaced (reinforcement spacing ≤0.3 m) reinforcement, the beneficial effects of geosynthetic inclusion is significantly enhanced, and the load-deformation behavior can be characterized as that of a composite material. A reinforced soil mass with closely spaced geosynthetic reinforcement is referred to as geosynthetic-reinforced soil (GRS). In this study, an analytical model is developed for predicting the ultimate load-carrying capacity and required reinforcement strength of a GRS mass. The model was developed based on a...

Robotic training apparatus and methods

Abstract: Adaptive controller apparatus of a robot may be implemented. The controller may be operated in accordance with a reinforcement learning process. A trainer may observe movements of the robot and provide reinforcement signals to the controller via a remote clicker. The reinforcement may comprise one or more degrees of positive and/or negative reinforcement. Based on the reinforcement signal, the controller may adjust instantaneous cost and to modify controller implementation accordingly. Training via reinforcement combined with particular cost evaluations may enable the robot to move more like an animal.

Positive reinforcement as treatment for problem behavior maintained by negative reinforcement.

Abstract: Functional analyses (Iwata, Dorsey, Slifer, Bauman, & Richman, 1982/1994) have been useful in determining function-based treatments for problem behavior. Recently, however, researchers have evaluated the use of arbitrary reinforcers (e.g., positive reinforcers) to decrease problem behavior maintained by negative reinforcement, particularly in the absence of extinction. We provide a brief review of recent research on this topic and discuss implications regarding mechanisms, practice, and future research directions.

Concrete cover cracking due to uniform reinforcement corrosion

Abstract: Service life design (SLD) is an important tool for civil engineers to ensure that the structural integrity and functionality of the structure is not compromised within a given time frame, i.e. the service life. In SLD of reinforced concrete structures, reinforcement corrosion is of major concern and reinforcement de-passivation is a frequently used limit state. The present paper investigates an alternative limit state: corrosion-induced cover cracking. Results from numerical simulations of concrete cover cracking due to reinforcement corrosion are presented. The potential additional service life is calculated using literature data on corrosion rate and Faraday’s law. The parameters varied comprise reinforcement diameter, concrete cover thickness and concrete material properties, viz. concrete tensile strength and ductility (plain concrete and fibre reinforced concrete). Results obtained from the numerical simulations reveal that, depending on the serviceability limit state applied, the service life of a reinforced concrete structure can be increased significantly by allowing minor damage of the cover.

Experimental flexural behavior of SMA-FRP reinforced concrete beam

Abstract: The most critical drawback in currently used steel reinforcement in reinforced concrete (RC) structures is susceptibility to accumulation of plastic deformation under excessive loads. Many concrete structures due to damaged (yielded) steel reinforcement have undergone costly repairs and replacements. This research presents a new type of shape memory alloy (SMA)-based composite reinforcement with ability to withstand high elongation while exhibiting pseudo-elastic behavior. In this study, small diameter SMA wires are embedded in thermoset resin matrix with or without additional glass fibers to develop composite reinforcement. Manufacturing technique of new proposed composite is validated using microscopy images. The proposed SMA-FRP composite square rebars are first fabricated and then embedded in small scale concrete T-beam. 3-point bending test is conducted on manufactured RC beam using a cyclic displacement controlled regime until failure. It is found that the SMA-FRP composite reinforcement is able to enhance the performance of concrete member by providing re-centering and crack closing capability.

Assessment and treatment of social avoidance

Abstract: Problem behavior maintained by social-negative reinforcement often is evoked by a specific type of social interaction--the presentation of task demands. This study involved assessment and treatment of a more general form of social avoidance in which the establishing operation (EO) for problem behavior consisted of social interaction per se. Four subjects exhibited high rates of problem behavior during the play or demand conditions of a functional analysis (FA). A subsequent FA in which problem behavior produced escape from social interaction confirmed social avoidance for all subjects. A series of interventions aimed at attenuating aversive characteristics of social interaction then was implemented with 3 of the subjects. These interventions included vicarious reinforcement, conditioning of social interaction as a reinforcer, stimulus fading, and differential reinforcement (DRA) plus extinction (EXT). DRA plus EXT was the only condition in which decreases in problem behavior and increases in social interactions were observed reliably.

An evaluation of generalization of mands during functional communication training

Abstract: The primary purpose of this study was to evaluate the generalization of mands during functional communication training (FCT) and sign language training across functional contexts (i.e., positive reinforcement, negative reinforcement). A secondary purpose was to evaluate a training procedure based on stimulus control to teach manual signs. During the treatment evaluation, we implemented sign language training in 1 functional context (e.g., positive reinforcement by attention) while continuing the functional analysis conditions in 2 other contexts (e.g., positive reinforcement by tangible item; negative reinforcement by escape). During the generalization evaluation, we tested for the generalization of trained mands across functional contexts (i.e., positive reinforcement; negative reinforcement) by implementing extinction in the 2 nontarget contexts. The results suggested that the stimulus control training procedure effectively taught manual signs and treated destructive behavior. Specific patterns of generalization of trained mands and destructive behavior also were observed.

Minimum web reinforcement in deep beams

Abstract: An experimental study was performed to examine current code requirements for minimum web reinforcement of reinforced concrete deep beams. Twelve full-scale tests were conducted in which the shear span-depth ratio (a/d) was 1.2, 1.85, or 2.5. At each a/d, the quantity of web reinforcement was the primary variable. Web reinforcement ranged from 0 to 0.3% in the vertical and horizontal directions. The compressive strength of concrete of the test specimens ranged from 3200 to 5000 psi (22 to 34 MPa). Diagonal cracking loads, diagonal crack widths, and failure shears were recorded for each test. The results indicated that a larger quantity of web reinforcement was needed to adequately restrain the width of diagonal cracks than to provide adequate deep beam shear capacity. Based on the strength and serviceability results, a minimum web reinforcement of 0.3% in each orthogonal direction was recommended for deep beams.

Composite Behavior of Geosynthetic Reinforced Soil Mass

Abstract: This study investigated the composite behavior of a geosynthetic reinforced soil (GRS) mass. Many studies have been conducted on the behavior of GRS structures; however, the interactive behavior between the soil and geosynthetic reinforcement in a GRS mass has not been fully elucidated. Current design methods consider the reinforcement in a GRS structure as tiebacks and adopt a design concept that the reinforcement strength and reinforcement spacing produce the same effects on the performance of a GRS structure. This has encouraged designers to use stronger reinforcement at a larger spacing to reduce time and effort in construction. A series of large-size generic soil geosynthetic composite (GSGC) tests were designed and conducted to examine the behavior of a GRS mass under well-controlled conditions. The tests clearly demonstrated that reinforcement spacing has a much stronger impact than reinforcement strength on the performance of the GRS mass. An analytical model was established to describe the relative contribution of reinforcement strength and reinforcement spacing. Based on the analytical model, equations were developed to calculate the apparent cohesion of a GRS composite, the ultimate load-carrying capacity of a GRS mass, and the required tensile strength of reinforcement for a prescribed value of spacing. The equations were verified using measured data from the GSGC tests and measured data from large-size experiments by other researchers, as well as by results of the finite element (FE) method of analysis. Due to the popularity of GRS walls with modular block facing, an analytical procedure was developed for predicting the walls’ lateral movement. This procedure also allows the required tensile strength of the reinforcement to be determined by simple calculations. In addition, compaction-induced stresses, which have usually been ignored in design and analysis of GRS structures, were investigated. An analytical model for estimating compaction-induced stresses in a GRS mass was proposed. Preliminary verification of the model was made by using results from the GSGC tests and FE analysis. The dilative behavior of a GRS composite was also examined. The presence of geosynthetic reinforcement has a tendency to suppress dilation of the surrounding soil and reduce the angle of dilation of the soil mass. The dilative behavior offers a new explanation of the reinforcing mechanism, and the angle of dilation may be used to reflect the degree of reinforcing of a GRS mass.