A framework for randomized time-splitting in linear-quadratic optimal control

Inspired by the successes of stochastic algorithms in the training of deep neural networks and the simulation of interacting particle systems, we propose and analyze a framework for randomized time-splitting in linear-quadratic optimal control. In our proposed framework, the linear dynamics of the original problem is replaced by a randomized dynamics. To obtain the randomized dynamics, the system matrix is split into simpler submatrices and the time interval of interest is split into subintervals. The randomized dynamics is then found by selecting randomly one or more submatrices in each subinterval. We show that the dynamics, the minimal values of the cost functional, and the optimal control obtained with the proposed randomized time-splitting method converge in expectation to their analogues in the original problem when the time grid is refined. The derived convergence rates are validated in several numerical experiments. Our numerical results also indicate that the proposed method can lead to a reduction in computational cost for the simulation and optimal control of large-scale linear dynamical systemsThis project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No: 694126- DyCon), the Alexander von Humboldt-Professorship program, the European Unions Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant agreement No.765579-ConFlex and the Transregio 154 Project “Mathematical Modelling, Simulation and Optimization Using the Example of Gas Networks”, project C08, of the German DFG, the grant PID2020-112617GB-C22, “Kinetic equations and learning control” of the Spanish MINECO, and the COST Action grant CA18232, “Mathematical models for interacting dynamics on networks” (MAT-DYN-NET

Quasi-simultaneous coupling methods for partitioned problems in computational hemodynamics

The paper describes the numerical coupling challenges in multiphysics problems like the simulation of blood flow in compliant arteries. In addition to an iterative coupling between the fluid flow and elastic vessel walls, i.e. fluid-structure interaction, also the coupling between a detailed 3D local (arterial) flow model and a more global 0D model (representing a global circulation) is analyzed. Most of the coupling analysis is formulated in the more abstract setting of electrical-network models. Both, weak (segregated) and strong (monolithic) coupling approaches are studied, and their numerical stability limitations are discussed. Being a hybrid combination, the quasi-simultaneous coupling method, developed for partitioned problems in aerodynamics, is shown to be a robust and flexible approach for hemodynamic applications too

A comparative analysis of the nutritional status of children attending early childhood development centres in Gauteng, North-West and Limpopo Province, South Africa

The nutritional status of children is a valuable indicator of health status and can indicate inequalities in health faced by the populations. The preschool period is the critical stage of active development and growth of physical, social, and mental wellbeing of children. Children eating  patterns and food preferences develop over a lifetimeand are influenced by family, ethnicity, and social environment. The purpose of the study was to do a comparative analysis of the nutritional status of children aged 2 to 5 years attending early childhood development centres in South Africa. A quantitative descriptive design was used to assess the nutritional status of 872 children attending preschool in the Soshanguve, Moretele, and Makhuduthamaga areas, and data was collected using a structured, researcher-administered questionnaire. The variables collected were age, sex, weight, height, mid-upper arm circumference. Gender and agespecific BMI cut-off points were used to determine the nutritional status. The study sample consisted of 872 preschool children, of which 422 (48%) were males, and 450 (52%) were females. The prevalence of overweight; obesity, and undernutrition were 7.7%, 3.4%, and 3.2%, respectively. The findings of this study showed that in all ECDs areas, most of the male children had normal weight. In this study, the age of children (p=0.007), as well as ECDs area (p=0.000), influenced the BMI of the children (p=0.007), and that overweight was higher amongst older children, 4 & 5 years from rural ECD area. The prevalence of overweight amongst children was 4.2% (Soshanguve), 9.3% (Moretele), and 9.6% (Makhuduthamaga), and the prevalence of underweight amongst children was 3.9% in  Soshanguve, 2.7% in Moretele, and 3.1% in Makhuduthamaga. The prevalence of underweight was higher in urban ECD areas as compared to ECDs  in rural areas. In this study, overnutrition was more prevalent as compared to undernutrition. Therefore, there is a need for nutritional intervention which promotes a healthy lifestyle in preschools.&nbsp

Age-dependent modulation of motor network connectivity for skill acquisition, consolidation and interlimb transfer after motor practice

Objective: Age-related differences in neural strategies for motor learning are not fully understood. We determined the effects of age on the relationship between motor network connectivity and motor skill acquisition, consolidation, and interlimb transfer using dynamic imaging of coherent sources. Methods: Healthy younger (n = 24, 18-24 y) and older (n = 24, 65-87 y) adults unilaterally practiced a visuomotor task and resting-state electroencephalographic data was acquired before and after practice as well as at retention. Results: The results showed that right-hand skill acquisition and consolidation did not differ between age groups. However, age affected the ability to transfer the newly acquired motor skill to the non-practiced limb. Moreover, strengthened left- and right-primary motor cortex-related beta conectivity was negatively and positively associated with right-hand skill acquisition and left-hand skill consolidation in older adults, respectively. Conclusion: Age-dependent modulations of bilateral resting-state motor network connectivity indicate age-specific strategies for the acquisition, consolidation, and interlimb transfer of novel motor tasks. Significance: The present results provide insights into the mechanisms underlying motor learning that are important for the development of interventions for patients with unilateral injuries. (C) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved

The proof of the pudding is in the eating? Implementation of cooperative learning:Differences in teachers’ attitudes and beliefs

In the current study differences between primary school teachers classified as high-performing in their implementation of cooperative learning (CL) in their classrooms and teachers who were less successful in implementing cooperative learning were investigated. The levels of implementation of cooperative learning differed significantly between teachers, especially in teaching students the needed cooperative behaviours. Based on semi-structured interviews, it was found that low-performing CL teachers struggle more with student behaviour during cooperative learning, while high-performing CL teachers feel more able to regulate student behaviour. We concluded that teachers who differed in their teacher performance of implementation of cooperative learning also differed in their attitudes and beliefs about this approach. An integrated model on professional development and teacher change is proposed to interpret the results of differences between teachers. This model shows that positive attitudes and beliefs before implementation, but also experiencing positive student outcomes (incl. positive student behaviour) during implementation are important factors in making cooperative learning successful in practice. We suggest that teachers should be prevented from entering a negative spiral in which they experience student behaviour during cooperative learning only as difficult and, therefore, do not succeed in improving students’ cognitive and behavioural outcomes

Promoting students' social behavior in primary education through Success for All lessons

Success for All (SfA) is a comprehensive school reform program with a strong emphasis on cooperative learning that aims to improve students' social emotional learning alongside students' cognitive learning. In the present study it was examined whether SfA led to improved students' social behavior in Grade 1-3 of primary education. Peer sociometric data was collected for 974 students aged 6-9. Using multivariate multilevel analysis we found no significant effect of SfA on students' proand antisocial behavior over time. However, a significant interaction effect was found showing that antisocial behavior of students from disadvantaged backgrounds decreased in the intervention condition in Grade 2. This is a promising finding given that the SfA program was especially developed for schools serving large numbers of disadvantaged students. Implications of the study are described