Multifidelity variance reduction for pick-freeze Sobol index estimation

Many mathematical models involve input parameters, which are not precisely known. Global sensitivity analysis aims to identify the parameters whose uncertainty has the largest impact on the variability of a quantity of interest (output of the model). One of the statistical tools used to quantify the influence of each input variable on the output is the Sobol sensitivity index, which can be estimated using a large sample of evaluations of the output. We propose a variance reduction technique, based on the availability of a fast approximation of the output, which can enable significant computational savings when the output is costly to evaluate

Randomized pick-freeze for sparse Sobol indices estimation in high dimension

This article investigates a new procedure to estimate the influence of each variable of a given function defined on a high-dimensional space. More precisely, we are concerned with describing a function of a large number $p$ of parameters that depends only on a small number $s$ of them. Our proposed method is an unconstrained $\ell_{1}$-minimization based on the Sobol's method. We prove that, with only $\mathcal O(s\log p)$ evaluations of $f$, one can find which are the relevant parameters

Global sensitivity analysis for the boundary control of an open channel

The goal of this paper is to solve the global sensitivity analysis for a particular control problem. More precisely, the boundary control problem of an open-water channel is considered, where the boundary conditions are defined by the position of a down stream overflow gate and an upper stream underflow gate. The dynamics of the water depth and of the water velocity are described by the Shallow Water equations, taking into account the bottom and friction slopes. Since some physical parameters are unknown, a stabilizing boundary control is first computed for their nominal values, and then a sensitivity anal-ysis is performed to measure the impact of the uncertainty in the parameters on a given to-be-controlled output. The unknown physical parameters are de-scribed by some probability distribution functions. Numerical simulations are performed to measure the first-order and total sensitivity indices

Does quality child care centre shape children's behaviour? a case study of IIUM Educare

This paper discusses the role of child care centre in shaping children’s social behaviour. It hypothesizes that quality child care affects children’s social behaviour. More specifically, it is assumed that high quality child care will predict positive social behaviour in children. 100 parents of children aged 4 to 5 year old at the IIUM EDUCARE, Gombak participated in this study. Data were collected via survey and observations using measures such as the Early Childhood Environmental Rating Scale–Revised [ECERS-R ](Harms, Clifford, & Cryer, 1998), the Caregiver Interaction Scale [CIS] (Arnett, 1989), and the Adaptive Social Behaviour Inventory [ASBI] (Hogan, Scott & Bauer, 1992). Results indicated that the aspect of caregiver child interaction significantly associated with children social competency. Findings also suggested that the role of quality child care varied as a function of family variable. These results provide useful information in understanding the significant role of child care centre in child development. Key words: child care quality, caregiver –child interactions, family relationship, children’s social behaviou

Effects of the amount of time in child care on children’s cognitive and social development.

This thesis has four main goals: (1) to examine the association between different measures of time in childcare on children’s cognitive and social development; (2) to investigate the influence of child-care-related variables (i.e., structural and process features of quality child care, caregivers’ mental health status and job satisfaction) on child developmental outcomes; (3) to determine whether child care predicts developmental outcomes after controlling for the effects of family-background variables (e.g., family social environment, parental discipline practices and parental mental health status); and (4) to examine the moderating effect of family and other predictor variables on the relationship between the amount of time spent in child care and its effect on children’s cognitive and social development. To achieve these goals, data were collected from 147 children between 3-4 years of age in Study I and 89 children aged 4-5 years in follow-up studies. These children were attending nationally accredited child care centres in South Australia, but in areas that differed socio-economically. The first finding was that different measures of time in childcare were not equally related to child developmental outcomes. The number of day(s) in a week, amount of hour(s) in a day and in a week spent in childcare was negatively related to children’s social behaviour, whereas the number of months children had spent in childcare was positively related to social development scores. A second finding was that the structural feature of childcare (group size) was significantly related to child developmental outcomes. A smaller group size (10-20 children) was found to have a greater significant positive effect than bigger group size (21-30 children) on child psychosocial behaviour. Another quality feature, a harsh style of caregiver interaction was associated with high scores in child conduct problems measure. A third finding was that higher levels of family conflict were associated with higher scores on the SDQ and ASBI subscales while higher levels of expressiveness in the family were associated with higher scores on the ASBI subscales. Further, higher scores on a measure of dysfunctional parental discipline practices were associated with lower scores in social competence measures in children. Fourth, the nature of caregiver interactions with children (in particular, a harsher style of interaction) was found to moderate the effect of time spent in child care and its consequent impact on children’s developmental outcomes. Specifically, it was found that: (1) children who spent long hours in daily care had higher caregiver assessed scores on the SDQ if the caregiver practised a harsher style of interaction; and (2) children who attended childcare many hours per week were rated by their caregivers as having lower prosocial scores if the child attended a centre where caregivers interacted more harshly with children, Other results obtained from the analysis of interaction effects showed that family-related variables (i.e., family conflict, expressiveness, dysfunctional parenting discipline and lax parenting style) moderated the effect of time spent in child care on children’s developmental outcomes. In particular, it was found that: (1) children who attended many days per week and who came from family environments characterised by higher levels of conflict were given lower ratings for prosocial behaviour; (2) children who spent more hours of child care in a week were rated low in peer problems measure when the family reported high social expressiveness; (3) children who spent more hours in a week in childcare were given higher ratings for prosocial behaviours if the children had been exposed to more dysfunctional parenting discipline practises at home (i.e., total score and lax parenting style). These results are discussed in relation to studies in other countries on the effects that child care attendance has on child developmental outcomes. Consistent with findings in Sweden, the United Kingdom and the United States of America: (1) attending child care more hours in a week seem to have a negative effect on a child’s social developmental outcomes even after child care and family characteristics are taken into account; (2) family characteristics remain a significant predictor of child development even when children spend most of their day time in child care; and (3) structural and process features of child care had significant predictive effects on children’s development. In contrast to the findings from studies in these countries, this research showed that: (1) high numbers of months in child care positively affects child social development; (2) family variables (i.e., family conflict and dysfunctional parental discipline strategies) have both direct and indirect influences on child developmental outcomes; and (3) the effects of the amount of time in childcare vary as a function of caregiver interaction as well as family background variables. Further research is needed to understand all the mechanisms responsible for these convergent and divergent outcomes.Thesis (Ph.D.) -- University of Adelaide, School of Psychology, 201

Development of STEP-NC based machining system for machining process information flow

To realize the STEP-NC based machining system, it is necessary to perform machining feature extraction, generating machine-specific information, and creating a relationship between STEP-NC entities. A process planning system of a STEP-NC information flow that starts with constructing a machining feature from a CAD model will be developed. In this paper, a further in depth study of the implementation and adaptation of STEP-NC in manufacturing is studied. This study will help to understand how the data from CAD/CAM can be converted into STEP-NC codes and the machining process will be based on the STEP-NC codes generated