Formative feedback to transfer self‐regulation of task‐oriented reading strategies

The study includes two experiments to analyse the effects of automatic formative feedback designed to promote the transfer of self‐regulation of strategic decisions in task‐oriented reading (e.g. answering questions from an available text). Secondary‐school students read and answered multiple‐choice comprehension questions from two texts having them available while receiving consistent feedback about their performance and strategic decisions. Then, they read a different text and answered questions also with the text available, but receiving no feedback. In Experiment 1, we tested two feedback procedures that differed in task conditions and the feedback information associated to these conditions. The most effective was a procedure that forced students to select relevant text information to answer each question and provided accurate feedback based on that selection. Experiment 2 was designed to disentangle the role played by the selection task from that played by the feedback provided. We found that the two components contribute to transfer the self‐regulation strategies, although each one has a specific role for different strategies. Theoretical and practical implications of the studies are discussed.     

Influence of gas mixtures Ar-He and Ar-He-O2 on weldability of aluminum alloy AA5083-O using automated GMAW-P

Problems of industries and manufacturers of welded structures in aluminium alloys are centred on reduction of mechanical properties in welded joints due to heat input effects on the heat affected zone; as well as effects of discontinuities and metallurgical defects, high cost repairs, and low productivity. The aim of this paper is to evaluate the influence of gas mixtures 80Ar20He (MG1), 60Ar40He (MG2), 80Ar19He1O₂ (MG3), and 60Ar39He1O₂ (MG4), on aluminium alloy AA5083-O weldability using filler metal ER5183 using the automated GMAW-P process. Methodology has included a factorial experiment design, customisation of welding parameters, and characterisation of base metal and welding regions. Analysis of results were carried out based on microstructure evaluation of welding regions, measurements of hardness and tensile properties, observations of discontinuities and defects, costs evaluation, and welding speed. Results show that gas mixtures with O₂ are highly beneficial to obtain good weldability of the studied alloy.     

Bayesian Networks‐Based Probabilistic Safety Analysis for Railway Lines

A Bayesian network model is developed, in which all the items or elements encountered when travelling a railway line, such as terrain, infrastructure, light signals, speed limit signs, curves, switches, tunnels, viaducts, rolling stock, and any other element related to its safety are reproduced. Due to the importance of human error in safety, especial attention is given to modeling the driver behavior variables and their time evolution. The sets of conditional probabilities of variables given their parents, which permits quantifying the Bayesian network joint probability, are given by means of closed formulas, which allow us to identify the particular contribution of each variable and facilitate a sensitivity analysis. The probabilities of incidents affecting safety are calculated so that a probabilistic safety assessment of the line can be done and its most critical elements can be identified and sorted by importance. This permits improving the line safety and saving time and money in the maintenance program by concentrating on the most critical elements. To reduce the complexity of the problem, an original method is given that permits dividing the Bayesian network in to small parts such that the complexity of the problem becomes linear in the number of items and subnetworks. This is crucial to deal with real lines in which the number of variables can be measured in thousands. In addition, when an accident occurs the Bayesian network allows us to identify its causes by means of a backward inference process. The case of the real Palencia–Santander line is commented on and some examples of how the model works are discussed.     

Distinct Hardening Behavior of Ultrafine-Grained Al-Zn-Mg-Cu Alloy

The age-hardening response for ultrafine-grained, powder-metallurgy-consolidated aluminum 7091 was investigated for the first time. Peak hardening occurred after aging at 353 K (80 °C) for only 4 hours; further aging for up to 26 hours resulted in only slight fluctuations in hardness values. After the 4-hour aging, the precipitate population consists of a high density of nanoscale GP zones (diameter ~3 nm) and nanoscale η′ phase (<30 nm); η phase is not present.     

Investigation of the mechanical behaviour of Ti–6Al–4V alloy under hot forming conditions: Experiment and modelling

The present investigation aims at evaluating and understanding the formability of Ti–6Al–4V alloy under hot forming conditions (650 °C ≤ T ≤ 750 °C). To fulfil these objectives, it was necessary to establish accurate material models and predict microscopic material evolution depending on temperature and strain rate. Two kinds of microstructure were investigated, the first one considers a conventional grain size of the α‐phase (3 µm) whereas a combined forging‐rolling process is used to elaborate the second one and allows to obtain a very fine grain of the α‐phase (0.5 µm). In this research work, we propose to investigate the capabilities of the titanium alloy under forming conditions quite different from those usually considered in superplastic forming process (lower temperatures and higher strain rates).     

Stress and Damage Mitigation from Oriented Nanostructures within the Radular Teeth of Cryptochiton stelleri

Chiton are marine mollusks who use heavily mineralized and ultrahard teeth to feed on epilithic and endolithic algae on intertidal rocks. To fulfill this function, chiton teeth must be tough and wear‐resistant. Impressive mechanical properties are achieved in the chiton tooth through a hierarchically arranged composite structure consisting of a hard shell of organic‐encased and highly oriented nanostructured magnetite rods that surround a soft core of organic‐rich iron phosphate. Microscopic and spectroscopic analyses combined with finite element simulations are used to probe the ultrastructural features and uncover structure–mechanical property relationships in the fully mineralized teeth of the gumboot chiton Cryptochiton stelleri. By understanding the effects of the nanostructured architecture within the chiton tooth, abrasion‐resistant materials can be developed for tooling and machining applications, as well as coatings for equipment and medical implants.     

High performance lattice reduction on heterogeneous computing platform

The lattice reduction (LR) technique has become very important in many engineering fields. However, its high complexity makes difficult its use in real-time applications, especially in applications that deal with large matrices. As a solution, the modified block LLL (MB-LLL) algorithm was introduced, where several levels of parallelism were exploited: (a) fine-grained parallelism was achieved through the cost-reduced all-swap LLL (CR-AS-LLL) algorithm introduced together with the MB-LLL by Józsa et al. (Proceedings of the tenth international symposium on wireless communication systems, 2013) and (b) coarse-grained parallelism was achieved by applying the block-reduction concept presented by Wetzel (Algorithmic number theory. Springer, New York, pp 323–337, 1998). In this paper, we present the cost-reduced MB-LLL (CR-MB-LLL) algorithm, which allows to significantly reduce the computational complexity of the MB-LLL by allowing the relaxation of the first LLL condition while executing the LR of submatrices, resulting in the delay of the Gram–Schmidt coefficients update and by using less costly procedures during the boundary checks. The effects of complexity reduction and implementation details are analyzed and discussed for several architectures. A mapping of the CR-MB-LLL on a heterogeneous platform is proposed and it is compared with implementations running on a dynamic parallelism enabled GPU and a multi-core CPU. The mapping on the architecture proposed allows a dynamic scheduling of kernels where the overhead introduced is hidden by the use of several CUDA streams. Results show that the execution time of the CR-MB-LLL algorithm on the heterogeneous platform outperforms the multi-core CPU and it is more efficient than the CR-AS-LLL algorithm in case of large matrices.     

High stiffness polymer composite with tunable transparency

Biological materials are multifunctional performing more than one function in a perfect synergy. These materials are built from fairly simple and limited components at ambient conditions. Such judicious designs have proven elusive for synthetic materials. Here, we demonstrate a multifunctional phase change (pc) composite from simple building blocks, which exhibits high stiffness and optical transmittance control. We show an increase of more than one order of magnitude in stiffness when we embed paraffin wax spheres into an elastomer matrix, polydimethylsiloxane (PDMS) in a dynamic compression test. High stiffness is mainly influenced by presence of microcrystals within the wax. We further show fast temperature-controlled optical switching of the composite for an unlimited number of cycles without any noticeable mechanical degradation. Through experimental and finite element method, we show high energy absorption capability of pc-composite. Based on these properties, the pc-composite could be used as an effective coating on glasses for cars and windows. This simple approach to multi-functionality is exciting and could pave way for designs of other multifunctional materials at the macro-scale.     

Control of a 2 DoF robot using a Brain–Machine Interface

In this paper, a non-invasive spontaneous Brain–Machine Interface (BMI) is used to control the movement of a planar robot. To that end, two mental tasks are used to manage the visual interface that controls the robot. The robot used is a PupArm, a force-controlled planar robot designed by the nBio research group at the Miguel Hernández University of Elche (Spain). Two control strategies are compared: hierarchical and directional control. The experimental test (performed by four users) consists of reaching four targets. The errors and time used during the performance of the tests are compared in both control strategies (hierarchical and directional control). The advantages and disadvantages of each method are shown after the analysis of the results. The hierarchical control allows an accurate approaching to the goals but it is slower than using the directional control which, on the contrary, is less precise. The results show both strategies are useful to control this planar robot. In the future, by adding an extra device like a gripper, this BMI could be used in assistive applications such as grasping daily objects in a realistic environment. In order to compare the behavior of the system taking into account the opinion of the users, a NASA Tasks Load Index (TLX) questionnaire is filled out after two sessions are completed.