Repositório RCAAP

In this study, we examine associations between the quality of teacher-child interactions and infantoutcomes during their first months in Portuguese childcare centers. Participants were 90 infants, theirmothers and their teachers. A set of multiple regression models were conducted to determine whetherclassroom quality related to active engagement and non-engagement and to adaptive behavior six monthslater, controlling for important covariates, namely developmental age, child temperament, mothers’ edu-cation, and home quality. Results showed that, in higher quality classrooms, infants spent more timeactively engaged, less time non-engaged and six months later were rated as having higher levels of adap-tive behaviors. Findings provide further evidence for the need to better support teachers in fosteringinfant active engagement and unfolding capacities as part of high-quality daily experiences in childcare.

Although literature reports associations between parent-teacher communication and childcare quality, little is known about how such communications are related to family, child and childcare characteristics. This study examines whether child, family and childcare experience characteristics predict the level of parent-teacher communication, and differences between parents’ and teachers’ reports of communication. Participants were mothers of 90 infants and their teachers in childcare in Portugal. Results show that both parents and teachers report higher levels of communication in higher-quality programmes. Teachers reported more frequent communication than parents. Teachers, but not parents, reported more frequent communication when children spent fewer hours in childcare. Discussion highlights the relevance of monitoring the quality of childcare contexts, especially in early ages, and to increase parent-teacher communication when children spend more time in childcare. The importance of promoting high-quality childcare and accounting for variables at the mesosystemic level of development in teacher training are also discussed.

Recent research has shown that caregiver education and training can be important in determining levels of quality in early childhood, but has mainly considered the education and training of the lead teacher. In infant childcare, however, classrooms have more than one caregiver with varying levels of education and in Portugal it is less common to have a qualified teacher exclusively assigned to infant classrooms. This study examines the quality of caregiver-child interactions in infant classrooms and its association with caregiver qualifications and training, specifically the level of pre-service education and in-service training of the lead caregiver, whether she is exclusively assigned to an infant classroom or to more classrooms, and the pre-service education of the multiple caregivers in the classroom. Participants were 90 infant classrooms from Porto, Portugal. The CLASS-Infant (Hamre et al. 2014) was used to measure quality of caregiver-infant interactions. Classrooms with one lead caregiver holding at least a bachelor degree, whether exclusively assigned to the infant classroom or not, showed higher levels of quality. Few effects were found for in-service training. Results suggest that lead teachers with pre-service education in early childhood are likely to play an important role not only directly by interacting with children but also indirectly through team work.

Purpose: The purpose of this article is to explore the optimization of internal process is assumed as a critical factor to be capable of answering to the moulds industries. Consequently, it has been considered essential to adopt high-valued methodologies to support tooling industry in order to achieve global competitive advantages. For that purpose, this work aims to apply LEAN principles and techniques to support mould design and manufacturing processes. Methodology/Approach: The methodology used was based on PDCA/DMAIC, with the following stages: Define, Measure, Analyze, Improve and Control. For each stages was taken some of Lean Six Sigma techniques, such as Continuous Improvement, Value Stream Mapping, Pareto analysis and Overall Equipment Effectiveness. Findings: This study results was revealed that there are many areas on the organizations in the Mould Industry, when they utilize otimizations tools obtain hugt successes. With the Pareto analysis was carried out to show that events that contributes the most to the stops. The results were: unavailability of the operator (16.4%), programming the machine (14.4%) and tool exchange (12.4%) In the case of this Mould Industry study was obtained for the CNC machines studies, with the implementation of Lean Six Sigma tools as obtained a improvement about 20% of global OEE. Research Limitation/implication: This research was revealed that there the moulds are Project unique and difficult to analyze. Moreover, this paper reports that the approach LEAN Six Sigma is very interesting for the continuous improvement of processes and profitability of moulds industry. Originality/Value of paper: This research highlight areas of future research using of quality management methods and Lean Six Sigma tools to analyse and optimize production in the moulds industry. Therefore this research It is considered to promote and adopt high-valued methodologies to support tooling industry in order to achieve global competitive advantages.

Electricity market players operating in a liberalized environment requires access to an adequate decision support tool, allowing them to consider all the business opportunities and take strategic decisions. Ancillary services represent a good negotiation opportunity that must be considered by market players. For this, decision support tools must include ancillary market simulation. This paper proposes two different methods (Linear Programming and Genetic Algorithm approaches) for ancillary services dispatch. The methodologies are implemented in MASCEM, a multi-agent based electricity market simulator. A test case concerning the dispatch of Regulation Down, Regulation Up, Spinning Reserve and Non-Spinning Reserve services is included in this paper.

.The research proposed herein seeks to improve solar irradiance magnitude and variability results produced by the Weather Research and Forecasting (WRF) model using a novel offline coupling procedure (OCP). The OCP includes simulations in clear sky conditions, where the effects from varying atmospheric composition depend on the broadband clear sky model used, on cloud attenuation and on decomposition techniques to accurately separate the global irradiance into direct and diffuse components. Furthermore, shadowing and slope effects from orographic features and other obstacles are included with much greater detail. Benefits of the offline coupling procedure were quantified by comparison against local solar radiation measurements over a period of one year. A baseline test to explore the different configuration options was implemented. It considers two aerosol databases, three broadband clear sky models, two cloud attenuation corrections based on clear sky index (either global or by components) and four decomposition models. Given the amount of results from baseline tests, the relative root-mean-square error (rRMSE) was used as the criterion to identify the most suitable OCP configuration, which was subsequently used in the performance analysis. The current baseline test comprises seven sites selected from the Baseline Radiation Network (BSRN) in different terrain complexities and atmospheric conditions. Statistical indicators associated with the annual global horizontal irradiance reveal that OCP improved WRF results by 88.4% in terms of the relative mean bias error (rMBE) and by 5.0% in the value of the Nash-Sutcliffe efficiency (NSE). A standard OCP configuration to model global horizontal irradiance only is proposed. The rMBE of annual hourly global horizontal irradiance oscillated between −3.6% and 3.9%, whilst the NSE varied between 0.608 and 0.939. The analogous quantities for diffuse horizontal irradiance were 19.3% rMBE 4.6% and 0.371 NSE 0.717 , while for direct normal irradiance 6.5% rMBE 23.2% and 0.101 NSE 0.656.

This study examines the quality of infant center care in Portugal through a multi-measure approach and investigates the associations among process quality dimensions and structural quality indicators. Ninety infant child care classrooms were observed during two full mornings with the ITERS-R, the CLASS-Infant and the CIS. Results revealed that a two-factor structure of process quality with the domains (a) Relationships and (b) Use of Space and Materials provided the best fit to the data. Of the structural indicators that were examined, teacher training showed the most robust relation to both process quality domains. In addition, classrooms with smaller groups and in centers located in non-urban areas were likely to show more sensitive relationships between teachers and infants. These findings have implications for public policy and professional development efforts on infant center care.

With adhesive bonding, design can be oriented towards lighter structures, not only regarding the direct weight saving advantages of the joint over fastened or welded joints, but also because of flexibility to joint different materials. Cohesive Zone Models (CZM) are a powerful design tool, although the CZM laws of the adhesive bond in tension and shear are required as input in the models. This work evaluated the shear fracture toughness and CZM laws of bonded joints. The End-Notched Flexure (ENF) test geometry was used with this purpose. The experimental work consisted on the shear fracture characterization of the bond by conventional and the J-integral techniques. Additionally, by the J-integral technique, the precise shape of the cohesive law was defined. Numerical Finite Element (FE) simulations were carried out in Abaqus® to assess the accuracy of the obtained CZM laws in predicting the experimental behaviour of the ENF tests, with positive results. As output of this work, fracture data is provided in shear for the selected adhesive, allowing the subsequent strength prediction of bonded joints.

Several adhesive joint configurations are available, namely butt joints, single-lap joints (SLJ), double-lap joints and scarf joints. Stepped-lap joints, which are not so studied, consist of a finite number of steps in the bonded area, possessing stress concentrations at all step edges instead of only at the bonded length edges. Stepped-lap joints increase the maximum load (Pm) over SLJ. The present study experimentally and numerically evaluates the static tensile strength of SLJ and stepped-lap joints bonded with the moderately ductile adhesive Araldite® 2015, considering varying values of overlap length (LO). A Finite Element Method (FEM) analysis was carried out to compare through-thickness normal (σy) and shear (τxy) stresses in the bondline between joint configurations. Additionally, a Cohesive Zone Modelling (CZM) analysis was considered to study the failure modes and to evaluate the CZM technique’s accuracy. Between SLJ and stepped-lap joints, the improved stress distributions of the stepped-lap joints resulted in higher joint performance, especially for higher LO. The CZM model revealed to be accurate in predicting Pm.

Structures built from several components require some means of joining. In this context, bonding with adhesives has several advantagescompared to traditional joining methods, e.g. reduction of stress concentrations, reduced weight penalty and easy manufacturing. Adhesives can be strong and brittle (e.g., Araldite® AV138) or less strong and ductile (e.g., Araldite® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce® 7888). In this work, the performance of the three above mentioned adhesives was tested in single-lap joints with varying values of overlap length (LO). The experimental work carried out is accompanied by a detailed numerical analysis by Finite Elements, based on Cohesive Zone Models (CZM). This procedure enabled detailing the performance of this predictive technique applied to bonded joints. Moreover, it was possible to evaluate which family of adhesives is more suited for each joint geometry. CZM revealed to be highly accurate, except for largely ductile adhesives, although this could be circumvented with a different cohesive law.

Adhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. As a result, adhesives are being increasingly used in industries such as the automotive, aerospace and construction. Thus, it is highly important to predict the strength of bonded joints to assess the feasibility of joining during the fabrication process of components (e.g. due to complex geometries) or for repairing purposes. When using the Finite Element Method with advanced propagation laws, the tensile (Gnc) and shear (Gsc) fracture toughness of adhesive joints must be determined with accuracy. Several conventional methods to obtain Gnc and Gsc exist in the literature, mainly based on Linear Elastic Fracture Mechanics (LEFM). The J-integral technique is accurate to measure these parameters for adhesives with high ductility. In this work, the J-integral is used to obtain Gnc by the Double-Cantilever Beam (DCB) test. An optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab® sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain Gnc than the available methods is proposed (by the J-integral technique) and some results are presented regarding joints with different geometry and adherend material.

The relationship between the film generation and the coefficient of friction in grease lubricated contacts was investigated. Ball-on-disc tests were performed under different operating conditions: entrainment speed, lubricant temperature and surface roughness. The tests were performed with fully formulated greases and their base oils. The greases were formulated with different thickener types and also different base oils natures and viscosities. Film thickness measurements were performed in ball-on-glass disc tests, and Stribeck curves were measured in ball-on-steel disc tests with discs of different roughness. The role of the thickener and the base oil nature/viscosity on the film thickness and coefficient of friction was addressed and the greases’ performance was compared based on their formulation.

The maintenance management is a topic of strategic importance for automotive manufacturers. In fact, an effective maintenance process and a preventive maintenance (PM) procedure can significantly reduce the risk of equipment failures that can lead to downtime on the production lines. However, due to the complexity of an automotive production system, the risk of failure on a crucial piece of the production equipment cannot be entirely avoided. The study made in this paper aims at improving the availability of a critical production line through the total productive maintenance (TPM) methodology and supported by Lean Maintenance tools. An analysis is made of the initial condition of the line where the main problems are identified by employing several tools for this purpose, such as Mean Time between Failures (MTBF), Mean Time to Repair (MTTR), Overall Equipment Efficiency (OEE) and Availability (A). In response to the identified problems, an action plan is developed and implemented in order to find the root cause of the high number of malfunctions and faults in one of the line’s equipment with the use of 5S tools, visual management, and maintenance progress, as well as the development of a training program to increase operators’ skills. The results of such actions were positive as the line became more organized, the value of the MTBF increased, the MTTR value decreased, and consequently the overall availability increased.

The increasing competitiveness installed in the automotive industry implies continuous improvements in all fields of knowledge and action. Thus, it is very important to be aware of the wastes generate across all the productive and logistics operations. In this regard, and considering the production process of command cables for the automotive industry, it was detected that a significant volume of lubricant is wasted during the task of introducing grease into the spiral used in the command cables utilized to drive the doors, windows and brakes of motor vehicles. The industrial operation was carefully followed leading to identify the main causes of the wastes and a brainstorming was carried out allowing the discussion of new ideas on how to overcome the problem. A novel equipment was developed, being also cared all the logistics around the supplying task. The new solution developed, as well as the redefinition of the logistic process of supplying the lubricating grease to the production lines, made it possible to make the process more flexible for the admission of different grease packs, as well as a better utilization of the existing grease in the reservoirs, resulting in a cut of grease waste by more than 70%. It was also produced a prototype of the grease supply system, which allowed validate the previously developed system.

Due to the globalization of markets, the industrial competitiveness has increased significantly in the recent years. Within this scope, the transportation of products inside industrial parks acquires special relevancy. One of the solutions is the use of autonomous guided vehicles. This work presents the design of a modular autonomous vehicle, capable of carrying heavy loads, which will improve the performance of industrial parks. This is a compact vehicle with low associated costs and good transport speeds. A drive system was designed, which will be capable of transporting the proposed loads. This design was carried out using simulations of the transport with loads, either in plane ground or in an industrial park. A structural analysis to the vehicle was also undertaken by the Finite Element Method, showing the points of the structure that require reinforcement for the different load cases. Finally, the required corrections were implemented, giving to the structure the ability to carry the desired loads. The end result was an autonomous vehicle with capacity to safely transport the imposed loads in the most efficient possible manner.

This paper presents an integrated system that helps both retail companies and electricity consumers on the definition of the best retail contracts and tariffs. This integrated system is composed by a Decision Support System (DSS) based on a Consumer Characterization Framework (CCF). The CCF is based on data mining techniques, applied to obtain useful knowledge about electricity consumers from large amounts of consumption data. This knowledge is acquired following an innovative and systematic approach able to identify different consumers’ classes, represented by a load profile, and its characterization using decision trees. The framework generates inputs to use in the knowledge base and in the database of the DSS. The rule sets derived from the decision trees are integrated in the knowledge base of the DSS. The load profiles together with the information about contracts and electricity prices form the database of the DSS. This DSS is able to perform the classification of different consumers, present its load profile and test different electricity tariffs and contracts. The final outputs of the DSS are a comparative economic analysis between different contracts and advice about the most economic contract to each consumer class. The presentation of the DSS is completed with an application example using a real data base of consumers from the Portuguese distribution company.

The automotive industry, like many other industries, uses a wide range of parts produced by the die-cast process. Parts like engine blocks, wheel spacers, alternator housings and command cable terminals, are made by die casting with different kinds of materials like aluminium and zinc alloys. Despite being a reliable process both in terms of quantity and quality, it is very important to keep the process parameters controlled, in order to achieve a minimum percentage of defective parts, which may be caused by several factors such as, porosities, segregations, incomplete fill, soldering, cracks, etc. The main goal of the die casting industry is to achieve the zero per cent defects target, a goal that goes along with the automotive industry and its quality system, and to accomplish this objective the stakeholders need to invest in research and development. In the casting industry, for instance, it is very important to have a complete knowledge of the entire process developed inside the casting machine, from the melting pot to the die, in order to obtain data so one can improve the filling parameters, machine parts, and moulds. The focus of the presented study is the improvement of the methodologies used to design moulds for control cable terminals in Zamak alloys. The work starts by characterizing the flow happening inside the mould at the moment of cavity fill by analysing computer fluid dynamics simulations (CFD). The study proceeds by quantifying the porosities detected on cut terminal surfaces, and the ultimate goal is achieved with the modification of molten metal flow systems, like channels and sprues, and the introduction of venting systems, with a resource to mathematical and geometrical calculus developed in MATLAB® specifically for that purpose. The paper ends with the validation of the improvements, by comparing the initial results with the ones obtained through an improved mould, building bases for novel design concepts of moulds for this kind of parts, as well as new studies trying to improve the results now achieved.

Cohesive zone modelling (CZM) is widespread for the strength analysis of bonded joints. The fracture toughness (GC) is required to use CZM. A scarcely studied mixed-mode test is the Asymmetric Tapered Double-Cantilever Beam (ATDCB), which merges a Tapered Double-Cantilever Beam (TDCB) adherend with a Double-Cantilever Beam (DCB) adherend. This work addresses the ATDCB test to estimate the fracture envelope of a structural adhesive. TDCB and End-Notched Flexure (ENF) tests were also performed to acquire the tensile (GIC) and shear fracture toughness (GIIC), respectively. Numerically, mixed-mode CZM laws were constructed based on the obtained data, and the results were compared with experiments, to validate the CZM laws and the mixed mode propagation criterion. As a result, the best damage propagation criterion for mixed mode was estimated and validated.

The growing globalization of the different types of market requires that companies invest, in a recurrent way, to optimize and improve all the processes inherent to their activities. Aluminium extrusion is the main industrial process used to create profiles of a fixed cross-section. This process requires appropriate processing parameters to be used, in order to produce diverse profiles and high-quality products. The company’s ability to adapt and improve the productive process are differentiating factors against the competition. Thus, understand the main operations and dynamics of the companies is crucial. This work presents an empirical study concerning the extrusion process of a Portuguese company in the aluminium sector. By analysing a real data base provided by the company, the main objective is to model the aluminium extrusion process. Taking into account the variables that most influence the extrusion of different profiles, the aim is to minimize the production of scrap. First, by studying the literature in the subject, the variables that most contribute to scrap production were identified. Since the database provided by the company did not present all the variables described in literature, proxy variables were considered. Next, a multivariate linear regression model for explaining the amount of scrap taking as explanatory the identified variables was estimated. With this analysis, it was possible to identify levels of significance of the variables under study, and therefore understand how each of the variables contributes to the increase or decrease of the amount of scrap on the production of aluminium profiles. The results show that variables concerning with extrusion temperature, time, speed, pressure and die geometry are crucial to improve and control the scrap production. The obtained model will be improved, in future work, by including further variables of the extrusion process. Furthermore, factor analysis and GHML methodologies will also be considered for explaining the production of scrap and therefore improve the production process.

The effect of organophilic clay (C15A) in PP compatibilized polymer (PP/PP-g-MA) through rheological experimental results is presented. This study focusses on the description of the rheological behaviour of the organophilic layers along the screws of a twin screw extruder by melting process, varying the screw profile as well as the processing conditions, namely screw speed, temperature and feed rate. Different levels of dispersion were found along the screws for all conditions and positions analyzed by rheology. The qualitative analysis of the images obtained by transmission electron microscopy, reinforced the results. Furthermore, the effects of the processing conditions on dispersion of C15A layers along the screw profile are analyzed using multiple linear regression techniques. The results show statistically significant differences of all rheology measures for all the processing conditions and positions along the extruder.