The effectiveness of adaptive versus non-adaptive learning with digital educational games

For the training of academic skills, digital educational games with integrated adaptivity are promising. Adaptive games are considered superior to non-adaptive games, because they constantly assess children's performance, and accordingly adapt the difficulty of the tasks corresponding to the children's individual level. However, empirical evidence with regard to the effectivity of adaptive compared to non-adaptive games is limited. A study was conducted with 191 children from the third year of Kinder garten who were enrolled in one of three conditions, that is, playing an adaptive version of the reading game (RG), a non-adaptive version of the RG or training with pen-and-paper exercises. In all three conditions, children trained emergent reading (phonological awareness and letter knowledge) once a week for 30 min over a period of 5 weeks. Children's performance on cognitive (phonological awareness, letter knowledge, reading fluency) and non-cognitive (motivation, self-concept) factors was assessed. Results revealed a significant improvement in phonological awareness and letter knowledge in all conditions. However, no differences between the conditions were observed with respect to children's improvement on phonological awareness and letter knowledge or on their post-test scores for reading fluency. With regard to motivation and self-concept, again, no differences in these non-cognitive factors were observed across conditions.     

Time Petri nets as an evaluation tool for handling travel time uncertainty in vehicle routing solutions

Congestion on roads leads to uncertainty in travel times, which is important in delivery of goods, especially in a business environment where high levels of customer service are expected. Delivery periods to customers might be constrained by time windows, which makes the scheduling and routing of vehicles from the supplier’s side more difficult. Operations Research methods turn into heuristics for this type of application. But when, on top, uncertainty on travel times are the case, any hope of a simple and well-performing heuristic is lost. This study applies a methodology in which a heuristic is used to find a solution for scheduling and routing under deterministic travel times and, by means of simulation, though the use of Time Petri nets evaluates the sensitivity of the solution to uncertainties in travel times from one customer to the next in a route.     

Classification of Illumination Methods for Mixed Reality

A mixed reality (MR) represents an environment composed both by real and virtual objects. MR applications are used more and more, for instance in surgery, architecture, cultural heritage, entertainment, etc. For some of these applications it is important to merge the real and virtual elements using consistent illumination. This paper proposes a classification of illumination methods for MR applications that aim at generating a merged environment in which illumination and shadows are consistent. Three different illumination methods can be identified: common illumination, relighting and methods based on inverse illumination. In this paper a classification of the illumination methods for MR is given based on their input requirements: the amount of geometry and radiance known of the real environment. This led us to define four categories of methods that vary depending on the type of geometric model used for representing the real scene, and the sdifferent radiance information available for each point of the real scene. Various methods are described within their category. The classification points out that in general the quality of the illumination interactions increases with the amount of input information available. On the other hand, the accessibility of the method decreases since its pre‐processing time increases to gather the extra information. Recent developed techniques managed to compensate unknown data with clever techniques using an iterative algorithm, hardware illumination or recent progress in stereovision. Finally, a review of illumination techniques for MR is given with a discussion on important properties such as the possibility of interactivity or the amount of complexity in the simulated illumination.     

An X-ray absorption approach to mixed and metallicity-sorted single-walled carbon nanotubes

Carbon based structures have been widely studied by X-ray absorption (XAS), also called NEXAFS, which is a very useful bulk probing method that allows examining the unoccupied density of states (DOS) and the site selective bonding environment. Two very well known spectral features in the XAS core level spectrum are the σ* and π* bands, and both have been analyzed in several studies for graphitic-like systems. However, among all the carbon materials, the unique one-dimensional electronic properties attributed to single-walled carbon nanotubes (SWCNTs) exhibit features that reveal clearly their electronic structure in the core level XAS spectrum. In this article, we outline the C1s response in XAS, which is related to the DOS of the conduction band in SWCNTs and its fine structure, revealed by experiments performed on metallicity-sorted SWCNT material. The progress in the identification of changes in the site selective conduction band electronic structure with XAS is discussed in detail.     

Proposed Framework for Evaluating Quality of Experience in a Mobile,Testbed-oriented Living Lab Setting

The framework presented in this paper enables the evaluation of Quality of Experience (QoE) in a mobile, testbed-oriented Living Lab setting. As a result, it fits within the shift towards more user-centric approaches in innovation research and aims to bridge the gap between technical parameters and human experience factors. In view of this, Quality of Experience is seen as a multi-dimensional concept, which should be considered from an interdisciplinary perspective. Although several approaches for evaluating perceived QoE have been proposed in the past, they tend to focus on a limited number of objective dimensions and fail to grasp the subjective counterparts of users’ experiences. We therefore propose a distributed architecture for monitoring network Quality of Service (QoS), context information and subjective user experience based on the functional requirements related to real-time experience measurements in real-life settings. This approach allows us to evaluate all relevant QoE-dimensions in a mobile context.     

Liquid metal thermal hydraulics R&D at European scale: achievements and prospects

A significant role for a future nuclear carbon-free energy production is attributed to fast reactors, mostly employing a liquid metal as a coolant. This paper summarizes the efforts that have been undertaken in collaborative projects sponsored by the European Commission in the past 20 years in the fields of liquid-metal heat transfer modeling, fuel assembly and core thermal hydraulics, pool and system thermal hydraulics, and establishment of best practice guidelines and verification, validation, and uncertainty quantification (UQ). The achievements in these fields will be presented along with the prospects on topics which will be studied collaboratively in Europe in the years to come. These prospects include further development of heat transfer models for applied computational fluid dynamics (CFD), further analysis of the consequences of fuel assembly blockages on coolant flow and temperature, analysis of the thermal hydraulic effects in deformed fuel assemblies, extended validation of three-dimensional pool thermal hydraulic CFD models, and further development and validation of multi-scale system thermal hydraulic methods.     

Chloride binding of cement-based materials subjected to external chloride environment – A review

This paper reviews the chloride binding of cement-based materials subjected to external chloride environments. Chloride ion exist either in the pore solution, chemically bound to the hydration products, or physically held to the surface of the hydration products. Chloride binding of cement-based material is very complicated and influenced by many factors, such as chloride concentration, cement composition, hydroxyl concentration, cation of chloride salt, temperature, supplementary cementing materials, carbonation, sulfate ions and electrical field etc. Four different types of binding isotherms, namely linear, Langmuir, Freundlich and BET binding isotherm have been proposed to describe the relationship between free and bound chloride, none of which can accurately express the relationships between free and bound chloride within the whole concentration range. Freundlich binding isotherm seems to be the most approximate one. However, some field data fit linear isotherm well. This may be ascribed to the leakage of hydroxyl ion. Many service life prediction models based on diffusion mechanism alone have been proposed during the past two decades. If chloride ion binding is not considered in the models, it underestimates the predicated service life.     

Subspace angles between ARMA models

We define a notion of subspace angles between two linear, autoregressive moving average, single-input–single-output models by considering the principal angles between subspaces that are derived from these models. We show how a recently defined metric for these models, which is based on their cepstra, relates to the subspace angles between the models.     

Measurement of the Length and Strength of Adhesive Interactions in a Nanoscale Silicon–Diamond Interface

The adhesive interactions between nanoscale silicon atomic force microscope (AFM) probes and a diamond substrate are characterized using in situ adhesion tests inside of a transmission electron microscope (TEM). In particular, measurements are presented both for the strength of the adhesion acting between the two materials (characterized by the intrinsic work of adhesion W_adh,int) and for the length scale of the interaction (described by the range of adhesion z₀). These values are calculated using a novel analysis technique that requires measurement of the AFM probe geometry, the adhesive force, and the position where the snap‐in instability occurs. Values of W_adh = 0.66 J m⁻² and z₀ = 0.25 nm are extracted using this technique. This value of work of adhesion is 70% higher than the work of adhesion calculated if one uses a conventional paraboloidal asperity model. Comparing to literature, the work of adhesion obtained using the new method is significantly higher than most experimental and simulation values for similar material pairs. The discrepancy is attributed to nanoscale roughness, which was not accounted for previously. Furthermore, the value of the range of adhesion is comparable to previously reported values, but is significantly larger than the commonly assumed value of the interatomic spacing.