High-Temperature Corrosion Testing of Uranium Silicide Surrogates

The corrosion resistance of cerium silicide, a surrogate of uranium silicide, is investigated to gain insight into the reaction of uranium silicide with water. As-received and proton-irradiated Ce3Si2, CeSi2, and CeSi1.x monolithic pellets are subjected to corrosion tests in water at 300°C and 9 MPa for up to 48 h. Results show that an oxide layer composed of Ce4.67 (SiO4)3O forms on the surface of all samples, and it grows thicker with extended exposure times. Irradiated samples corrode to a greater extent than their unirradiated counterparts, which is mainly a result of the existing post-irradiation cerium oxide and the presence of ion-induced defects. Most of the Ce3Si2 samples crack (as-received) or fracture (ion-irradiated) during testing, which is due to the brittleness of the samples and oxide erosion/spallation that occur during testing

Vibration-induced granular segregation: a phenomenon driven by three mechanisms

The segregation of large spheres in a granular bed under vertical vibrations is studied. In our experiments we systematically measure rise times as a function of density, diameter and depth; for two different sinusoidal excitations. The measurements reveal that: at low frequencies, inertia and convection are the only mechanisms behind segregation. Inertia (convection) dominates when the relative density is greater (less) than one. At high frequencies, where convection is suppressed, fluidization of the granular bed causes either buoyancy or sinkage and segregation occurs.Comment: 4 pages. 3 figures, revtex4, to appear in PRL (in press

Sequence tutor: Conservative fine-tuning of sequence generation models with KL-control

This paper proposes a general method for improving the structure and quality of sequences generated by a recurrent neural network (RNN), while maintaining information originally learned from data, as well as sample diversity. An RNN is first pre-trained on data using maximum likelihood estimation (MLE), and the probability distribution over the next token in the sequence learned by this model is treated as a prior policy. Another RNN is then trained using reinforcement learning (RL) to generate higher-quality outputs that account for domain-specific incentives while retaining proximity to the prior policy of the MLE RNN. To formalize this objective, we derive novel off-policy RL methods for RNNs from KL-control. The effectiveness of the approach is demonstrated on two applications; 1) generating novel musical melodies, and 2) computational molecular generation. For both problems, we show that the proposed method improves the desired properties and structure of the generated sequences, while maintaining information learned from data

Infographics or Graphics+Text: Which Material is Best for Robust Learning?

Infographic is a type of information visualization that uses graphic design to enhance human ability to identify patterns and trends. It is popularly used to support spread of information. Yet, there are few studies that investigate how infographics affect learning and how individual factors, such as learning styles and enjoyment of the information affect infographics perception. In this sense, this paper describes a case study performed in an online platform where 27 undergraduate students were randomly assigned to view infographics (n=14) and graphics+text (n=13) as learning materials about the same content. They also responded to questionnaires of enjoyment and learning styles. Our findings indicate that there is no correlation between learning styles and post-test scores. Furthermore, we did not find any difference regarding learning between students using graphics or infographics. Nevertheless, for learners using infographics, we found a significant and positive correlation between correct answers and the positive self-assessment of enjoyment/ pleasure. We also identified that students who used infographics keep their acquired information longer than students who only used graphics+text, indicating that infographics can better support robust learning.Comment: accepted as a full paper in the IEEE International Conference on Advanced Learning Technologie

Student teamwork: developing virtual support for team projects

In the 21st century team working increasingly requires online cooperative skills as well as more traditional skills associated with face to face team working. Virtual team working differs from face to face team working in a number of respects, such as interpreting the alternatives to visual cues, adapting to synchronous communication, developing trust and cohesion and cultural interpretations. However, co-located student teams working within higher education can only simulate team working as it might be experienced in organisations today. For example, students can learn from their mistakes in a non-threatening environment, colleagues tend to be established friends and assessing teamwork encourages behaviour such as “free-riding”. Using a prototyping approach, which involves students and tutors, a system has been designed to support learners engaged in team working. This system helps students to achieve to their full potential and appreciate issues surrounding virtual teamwork. The Guardian Agent system enables teams to allocate project tasks and agree ground rules for the team according to individuals’ preferences. Results from four cycles of its use are presented, together with modifications arising from iterations of testing. The results show that students find the system useful in preparing for team working, and have encouraged further development of the system

Ab initio modeling of oxygen impurity atom incorporation into uranium mononitride surface and subsurface vacancies

The incorporation of oxygen atoms has been simulated into either nitrogen or uranium vacancy at the UN(001) surface, sub-surface or central layers. For calculations on the corresponding slab models both the relativistic pseudopotentials and the method of projector augmented-waves (PAW) as implemented in the VASP computer code have been used. The energies of O atom incorporation and solution within the defective UN surface have been calculated and discussed. For different configurations of oxygen ions at vacancies within the UN(001) slab, the calculated density of states and electronic charge re-distribution was analyzed. Considerable energetic preference of O atom incorporation into the N-vacancy as compared to U-vacancy indicates that the observed oxidation of UN is determined mainly by the interaction of oxygen atoms with the surface and sub-surface N vacancies resulting in their capture by the vacancies and formation of O-U bonds with the nearest uranium atoms. Keywords: Density functional calculations, uranium mononitride, surface, defects, N and U vacancie

Integration of professional judgement and decision-making in high-level adventure sports coaching practice

This study examined the integration of professional judgement and decision-making processes in adventure sports coaching. The study utilised a thematic analysis approach to investigate the decision-making practices of a sample of high-level adventure sports coaches over a series of sessions. Results revealed that, in order to make judgements and decisions in practice, expert coaches employ a range of practical and pedagogic management strategies to create and opportunistically use time for decision-making. These approaches include span of control and time management strategies to facilitate the decision-making process regarding risk management, venue selection, aims, objectives, session content, and differentiation of the coaching process. The implication for coaches, coach education, and accreditation is the recognition and training of the approaches that“create time” for the judgements in practice, namely“creating space to think”. The paper concludes by offering a template for a more expertise-focused progression in adventure sports coachin

Fractura triplana epifisaria distal de tibia: a propósito de un caso con interposición de periostio

Se presenta un caso de fractura triplana en 2 fragmentos en un paciente varón de 13 años tratado quirúrgicamente, observando la interposición perióstica en el plano axial a nivel del fragmento antero-externo, que impedía la reducción anatómica de la zona epifisaria articular. Se analiza la anatomía quirúrgica de las fracturas triplanas considerando que esta lesión puede ser más frecuente de lo que se ha informado, y sólo valorada en los casos en que se emplee un abordaje antero-externo.The case of a 13-year-old boy with a two-fragment triplane fracture of the distal epiphysis of the tibia is presented. At surgery, an interposition of the periosteum in the axial plane behind the antero-lateral fragment, preventing the anatomical reduction of the epiphyseal joint surface was found. The surgical anatomy of triplane fractures is review taking into account that this lesion can be more frequent that it has been reported. The true incidence should be evaluated at surgery by antero-lateral approach

Fracturas del macizo trocantéreo. Estudio comparativo Ender-DHS: revision de 114 casos

Se presenta un estudio retrospectivo de 114 fracturas pertrocantéreas tratadas con enclavado elástico de Ender (71) y tornillo placa deslizante, DHS (43). Se efectuó un estudio estadístico descriptivo-comparativo entre los 2 grupos de pacientes según la técnica quirúrgica empleada. Se constató un mayor índice de estabilidad usando el DHS (81%), frente al 6 1 % del otro grupo. La tasa de complicaciones fue del 16% y 55% respectivamente. Los resultados clínicos fueron mejores en los enfermos tratados con DHS, fundamentalmente en cuanto a la deambulación que se consiguió en el 98% (Ender 75%), ausencia de dolor y movilidad conservada. Los autores piensan que la estabilidad preoperatoria no influye en la solidez del montaje usando el DHS, pero con la técnica de Ender ésta disminuye en las fracturas inestables; por ello, la técnica de Ender estaría solamente indicada en el tratamiento de fracturas estables en pacientes de edad avanzada o con mal estado general, aunque en clara competencia con el DHS.A retrospective study of 114 intertrochanteric fractures operated on either with Ender's rods (71) or dynamic hip screws, DHS (43) is presented. A statistical descriptive-comparative study between the 2 groups was attempted. There was a greater index of stability using the DHS (82%) than Ender's rods (61%). The rate of complications was 16% and 55% respectively. The clinical outcome was better in cases treated with DHS, specially for walking ability, which was regained in the 98% of cases (Ender 75%), painless and preserved mobility. The authors think that the stability before operation do not influence the solidity of the assembly using the DHS device. On the contrary, with the Ender's technique the fixation is no satisfactory in unstables fractures. Ender's rods would only be suitable for treatment of stable fractures in older patient or with serious associated diseases, although in clear competition with the DHS