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

Consumer acceptance of yellow, provitamin A-biofortified maize in KwaZulu-Natal

Objectives: To assess the acceptance of popular maize food products (phutu, thin porridge and samp), prepared with yellow, provitamin A-biofortified maize varieties, in 212 subjects between the ages of three and 55 years, from rural KwaZulu-Natal.Design: A cross-sectional study.Method: Preschool, primary school and secondary school subjects were randomly selected from two primary schools and one secondary school, respectively, while adult subjects constituted a convenience sample. Pre- and primary school children completed a paired preference test. Secondary school and adult subjects completed a five-point facial hedonic and a preference ranking test. Focus group discussions were conducted using adult subjects.Results: Preschool children preferred yellow maize to white maize food products: phutu (81% vs. 19%; p-value < 0.001), thin porridge (75% vs. 25%; p-value < 0.001) and samp (73% vs. 27%; p-value < 0.001). There was no statistically significant difference in preference for white and yellow maize by primary school children. Secondary school and adult subjects preferred white maize to yellow maize. Focus group discussions confirmed the preference for white maize by the adults.Conclusion: The study findings suggest that yellow, provitamin A-biofortified maize has the potential to succeed as a new strategy of dealing with the serious problem of vitamin A deficiency, especially among children of preschool age. However, in older groups, this strategy is unlikely to be successful, unless other strategies are implemented, including intensive nutrition education programmes on the nutritional benefits of the maize, targeting the market price at which yellow maize is sold, increasing its availability in local grocery stores, and improving its sensory properties through breeding.Keywords: yellow maize, provitamin A, vitamin A deficiency, consumer acceptanc

Nutritional quality of a ready-to-use food, and its acceptability to healthy and HIV-infected children receiving antiretroviral treatment

Objectives: The objectives of this study were to determine the nutritional quality of a ready-to-use food (RUF), and its acceptability to children who were “healthy” and to those who were human-immunodeficiency virus (HIV)-infected and receiving antiretroviral therapy (ART).Design: This was a cross-sectional survey that assessed the consumer acceptability of the RUF by the children.Setting and subjects: One hundred and eighty-eight children were selected from six schools, a day care and a hospital in Pietermaritzburg. Of these children, 123 were “healthy”, and 65 HIV-infected and receiving ART.Outcome measures: The outcome measure of the study was the nutritional quality of the RUF in terms of its nutrient levels relative to appropriate nutritional standards, and its acceptability rating by the children.Results: The RUF had appreciable levels of energy (2 624 kJ/100 g) and protein (15.7 g/100 g).The nutritional composition met the World Health Organization/World Food Programme/the United Nations Standing Committee on Nutrition/The United Nations Children’s Fund recommendations for an RUF regarding energy, protein and essential amino acid levels. Sensory evaluation indicated that the RUF was acceptable to both children who were healthy and to those who were  HIV-infected. Generally, more than 75% of the participants in both groups rated the product overall as “good”. More than 65% of the children liked the taste, smell and mouth feel.Conclusion: The RUF that was used in this study is a good source of energy and quality protein, and is acceptable to children. Further micronutrient analysis would determine the additional role of the RUF in alleviating micronutrient deficiencies, including vitamin A, zinc and iron. Since the RUF is acceptable to children who were healthy and to those who were  HIV-infected on ART, it can be used to address proteinenergy malnutrition in these target groups

Acceptance of a ready-to-use supplementary food by stable HIV-treated and HIV and tuberculosis (co-infected)-treated patients

Objectives: The objective of the study was to determine consumer  acceptance and perceptions of a ready-to-use supplementary food (RUSF)by subjects treated for human immunodeficiency virus (HIV) and HIV and tuberculosis (co-infected subjects).Design: A cross-sectional study was conducted.Subjects: One hundred and thirty-nine stable HIV-treated and HIV and tuberculosis (co-infected)-treated patients participated in the study. Sixty-eight healthy subjects served as the control group.Setting: The setting was Northdale Hospital and Grey’s Hospital in  Pietermaritzburg, KwaZulu-Natal.Outcome measures: Acceptance of the RUSF was assessed using a five-point facial hedonic scale by stable HIV-treated and HIV and tuberculosis (co-infected)-treated patients (n = 139) from Northdale Hospital and Grey’s Hospital in Pietermaritzburg, KwaZulu-Natal. Perceptions of the RUSF were determined through focus group discussions in which HIV-treated and HIV and tuberculosis (co-infected)-treated patients (n = 43) participated.Results: The overall acceptance of the RUSF was significantly associated with the health status of the subjects (p-value < 0.05). Overall, the product was liked by more than 90% of the HIV-treated and HIV and tuberculosis (co-infected)-treated individuals compared to 85% of the control group. More than 90% of the HIV-treated and HIV and tuberculosis   (co-infected)-treated individuals liked the taste, compared to 87% of the control group. The colour and mouth feel were rated to be “good” by more than 80% of the HIV-treated and HIV and tuberculosis (coinfected)-treated group, compared to approximately 70% of the healthy group. Focus group discussions revealed that the subjects perceived the mouth feel of the RUSF to be “rough”, and that as a health supplement, the RUSF should be provided free of charge, or at a reasonable cost, at public health centres.Conclusion: The RUSF was found to be highly acceptable to stable   HIV-treated and HIV and tuberculosis (co-infected)-treated subjects, although concern was raised about the mouth feel

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

Unlocking the hidden potentioal of electricity distribution grids

For the grid, electric vehicles can be seen as flexible loads since they stand still for at least 90% of the time. The coupling of these flexible loads to the grid can bring advantages for the power system. However, to connect electric cars enough capacity is needed. Already existing capacity might be made available for this extra load by using the flexibility of the electric vehicles and controlling them well. This paper describes an analysis of the existing capacity of the distribution grid of Enexis B.V. which might become available for flexible loads if they are coupled to the grid in an intelligent way. The available capacity of a part of the distribution grid owned and operated by Enexis B.V. is estimated, based on measured data. Further, it is described how this capacity can be used by flexible loads. It is also briefly discussed how this can be facilitated by the introduction of the so-called ‘Mobile Smart Grid’, which includes secondary systems to control the load

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