Ignition enhancement via radical farming in two-dimensional supersonic combustion

A two-dimensional numerical study has been performed of the ignition processes associated with the concept of radical farming for supersonic combustion. In a preliminary parametric study, a range of freestream conditions attainable in a hypersonic shock tunnel has been investigated, and mapped according to whether or not the behaviour known as radical farming is present - combustion-induced pressure rise in second or subsequent hot pockets rather than the first. One such case has been analysed in detail, having mean conditions across the combustion chamber entrance that would result in extremely long ignition lengths. The branching cycle and heat release reactions in the combustion process become active in the radical farm, and H and OH radicals are produced. Their rate of production slows in the expansion, but does not approach chemical freezing until towards the end of it. When the mixture flows through the shock at the second hot pocket, the presence of radicals enables the branching cycle and three-body recombination heat release reactions to accelerate, and significant pressure rise due to heat release is then able to occur

Increasing compliance with wearing a medical device in children with autism

Health professionals often recommend the use of medical devices to assess the health, monitor the well-being, or improve the quality of life of their patients. Children with autism may present challenges in these situations as their sensory peculiarities may increase refusals to wear such devices. To address this issue, we systematically replicated prior research by examining the effects of differential reinforcement of other behavior (DRO) to increase compliance with wearing a heart rate monitor in 2 children with autism. The intervention increased compliance to 100% for both participants when an edible reinforcer was delivered every 90 s. The results indicate that DRO does not require the implementation of extinction to increase compliance with wearing a medical device. More research is needed to examine whether the reinforcement schedule can be further thinned

Behavioural and Developmental Interventions for Autism Spectrum Disorder: A Clinical Systematic Review

Background: Much controversy exists regarding the clinical efficacy of behavioural and developmental interventions for improving the core symptoms of autism spectrum disorders (ASD). We conducted a systematic review to summarize the evidence on the effectiveness of behavioural and developmental interventions for ASD. Methods and Findings: Comprehensive searches were conducted in 22 electronic databases through May 2007. Further information was obtained through hand searching journals, searching reference lists, databases of theses and dissertations, and contacting experts in the field. Experimental and observational analytic studies were included if they were written in English and reported the efficacy of any behavioural or developmental intervention for individuals with ASD. Two independent reviewers made the final study selection, extracted data, and reached consensus on study quality. Results were summarized descriptively and, where possible, meta-analyses of the study results were conducted. One-hundred-and-one studies at predominantly high risk of bias that reported inconsistent results across various interventions were included in the review. Meta-analyses of three controlled clinical trials showed that Lovaas treatment was superior to special education on measures of adaptive behaviour, communication and interaction, comprehensive language, daily living skills, expressive language, overall intellectual functioning and socialization. High-intensity Lovaas was superior to low-intensity Lovaas on measures of intellectual functioning in two retrospective cohort studies. Pooling the results of two randomized controlle

An experimental investigation of hypersonic transverse jet interactions in laminar, transitional and turbulent flows

The interaction between a circular sonic jet and a Mach 6.65 cross flow on a flat plate have been investigated experimentally in a free piston shock tunnel. Turbulent wedges of varying widths were created upstream of the interaction using distributed and isolated wall roughness elements and the effects on the jet interaction flowfield were assessed using a combination of surface pressure measurements and schlieren visualisation. In all cases it was found that laminar-like and turbulent-like separation occurred simultaneously in the flowfield. The effects on the associated near field pressure distributions were found to depend on both the spanwise location of the wedge and its size relative to the expanding jet

Radical farm ignition processes in two-dimensional supersonic combustion

A two-dimensional numerical study was performed of the ignition processes associated with the concept of radical farming for supersonic combustion. In a preliminary parametric study, a range of freestream conditions attainable in a hypersonic shock tunnel was investigated and mapped according to whether or not the behavior known as radical farming is present: a combustion-induced pressure rise in second or subsequent hot pockets rather than the first Two such cases were analyzed in detail, both having mean conditions across the combustion-chamber entrance that would result in extremely long ignition lengths. The initiation, branching cycle, and heat release reactions in the combustion process become active in the radical farm, and H and OH radicals are produced. Their rate of production slows in the regions of flow expansion, but does not approach chemical freezing until toward the end of the localized expansion zones. Simultaneously, heat release elevates the local temperature. When the mixture flows through the shock at the second hot pocket, the elevated temperature and the presence of radicals enable the branching cycle and three-body recombination heat release reactions to accelerate, and significant pressure rise due to heat release is then able to occur. The extent to which this is completed in the second hot pocket depends on the inflow conditions

Numerical simulation of transitional behaviors in hypersonic transverse jet interaction

Transverse jets are investigated during planetary atmospheric entry and high speed flight with a view that they are for aero-maneuvering at high enthalpy flows. A two-dimensional transverse-jet interaction is numerically investigated for a particular experimental configuration. CFD++, a commercial Navier-Stokes CFD solver has been used for this purpose. The laminar/turbulent nature of the boundary layer at separation and the free-shear layer downstream of separation are extensively examined utilizing the transitional behavior of Spalart-Allmaras turbulence model. The outcome of this study will be used in an examination of the aero-thermodynamics and surface pressure fields of high enthalpy reacting flow in transverse-jet interaction. Such flows are typically encountered in planetary entry, aerobraking, aero-gravity assisted and exploratory fight at hypersonic velocities. Copyrigh