Micro-geometry effects on the nonlinear effective yield strength response of magnetorheological fluids

We use the novel constitutive model in [15], derived using the homogenization method, to investigate the effect particle chain microstructures have on the properties of the magnetorheological fluid. The model allows to compute the constitutive coefficients for different geometries. Different geometrical realizations of chains can significantly change the magnetorheological effect of the suspension. Numerical simulations suggest that particle size is also important as the increase of the overall particle surface area can lead to a decrease of the overall magnetorheological effect while keeping the volume fraction constant

Micro-geometry effects on the nonlinear effective yield strength response of magnetorheological fluids

We use the novel constitutive model in [15], derived using the homogenization method, to investigate the effect particle chain microstructures have on the properties of the magnetorheological fluid. The model allows to compute the constitutive coefficients for different geometries. Different geometrical realizations of chains can significantly change the magnetorheological effect of the suspension. Numerical simulations suggest that particle size is also important as the increase of the overall particle surface area can lead to a decrease of the overall magnetorheological effect while keeping the volume fraction constant

Composites with imperfect interface

New variational principles and bounds are introduced, describing the effective conductivity tensor for anisotropic two-phase heat conducting composites with interfacial surface resistance between phases. The new upper bound is given in terms of the two-point correlation function, component volume fractions and moment of inertia tensor for the surface of each heterogeneity. The new lower bound is given in terms of the interfacial surface area, component volume fractions and a scale-free matrix of parameters. This matrix corresponds to the effective conductivity associated with the same geometry but with non-conducting inclusions. The bounds are applied to theoretically predict the occurrence of size effect phenomena. We identify a parameter Rcr that measures the relative importance of interfacial resistance and contrast between phase resistivities. :The scale at which size effects occur is determined by this parameter. For isotropic conducting spheres in a less conducting isotropic matrix we show that for monodisperse suspensions of spheres of radius Rct the effective conductivity equals that of the matrix. For polydisperse suspensions of spheres it is shown that, when the mean radius lies below Rcr, the effective conductivity lies below that of the matrix. © 1996 The Royal Society

Asymptotic analysis of singular problems in perforated cylinders.

In this paper, we deal with elliptic problems having terms singular in the variable uu which represents the solution. The problems are posed in cylinders Ωnε of height 2n and perforated according to a parameter ε. We study existence, uniqueness and asymptotic behavior of the solutions uεn as the cylinders become infinite (n→+∞) and the size of the holes decreases while the number of the holes increases (ε→0)

Steady state non-Newtonian flow with strain rate dependent viscosity in domains with cylindrical outlets to infinity

The paper deals with a stationary non-Newtonian flow of a viscous fluid in unbounded domains with cylindrical outlets to infinity. The viscosity is assumed to be smoothly dependent on the gradient of the velocity. Applying the generalized Banach fixed point theorem, we prove the existence, uniqueness and high order regularity of solutions stabilizing in the outlets to the prescribed quasi-Poiseuille flows. Varying the limit quasi-Poiseuille flows, we prove the stability of the solution

Sustained attention training in children with fetal alcohol spectrum disorder

Objective. Attentional difficulties are the most commonly observed behaviours in children with FASD, and Attention Deficit Hyperactivity Disorder (ADHD) is often cited as a central feature of the profile associated with FASD. Attention deficits can be noted as early as infancy, or during the preschool years, and become critical when children enter the school system. Deficits in learning and memory are often secondary to an inability to attend effectively, which is not surprising given that attention is necessary for orienting toward relevant concepts or events. Without appropriate intervention, even mild deficits in this domain can have a significant negative impact on a child's development, as children grow missing important information in their immediate environment, having difficulty recalling events, making mistakes in daily tasks, and having difficulty with higher level cognitive processing such as problem solving and reasoning. Intervention research for children with FASD is limited to two published reports, with a glaring dearth in the area of attention. The purpose of the current study was to implement a cognitive-based intervention strategy that targeted attentional processes directly. -- Participants and methods. Twenty Labrador Inuit children (ages 6.8-11.9) were divided into 2 groups matched for age and non-verbal reasoning and randomly assigned to attention process training that focused on sustained attention (SA), or contact control (CC) conditions that included academic support and games. Pre- and post-treatment assessments were conducted with direct standardized measures of verbal and non-verbal reasoning (KBIT2 and CTONI) and attention (KiTAP and TEA-Ch), and indirect measures of attention and executive functioning (ADDES-3-SV and BRIEF teacher checklists). There were no significant differences between the treatment and contact-control groups on pre-training measures of attention or verbal and non-verbal reasoning. Children were trained using materials from Thomson and colleagues' Pay Attention program. All children participated in 12 daily 30-min individual training or support sessions, for approximately 3 weeks. On average, children completed all assessment and training sessions during a 5-6 week period (approximately 18-20 individual sessions). -- Results. Significant treatment effects emerged on untrained visual and auditory sustained attention tasks, including improved performance on correct responses, errors of omission, and variability of response time. Gains from training generalized to a task tapping selective attention, with significant improvements in errors of commission following sustained attention training. In addition, training seems to have also generalized to higher-order alternating attention tasks, with increased correct response performance and reduced errors of commission. While teachers rated all children as having post-test improvements in attention and executive functioning behaviour, and hence reported no differential effects of treatment, significant treatment effects emerged on a widely utilized measure of non-verbal reasoning (CTONI), with a similar trend on the KBIT2 non-verbal performance subscale. -- Conclusions. Given the high prevalence of attention deficits for children with FASD and the impact that these deficits have on many aspects of development, early intervention is critical for a better outcome for these children. Should we be able to target basic attention deficits through direct early intervention, we may be able to alter some of the secondary deficits associated with FASD throughout the teenage and young adult years. Based on the work conducted in this exploratory dissertation, it is concluded that sustained attention process training may be beneficial for children with FASD. While all children made nonspecific gains from participating in the current study, children undergoing direct sustained attention training made significant gains as a function of treatment on various untrained measures of attention. These beneficial effects generalized to a functional measure of non-verbal reasoning ability, with children's performance significantly improving on a widely utilized school-based instrument. Thus, it appears that direct training of attentional processes might provide a useful technique for use with the pediatric FASD population

On some remarkable positive polynomial operators of approximation

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