Liquid transport in scale space

International audienceWhen a liquid stream is injected into a gaseous atmosphere, it destabilizes and continuously passes through different states characterized by different morphologies. Throughout this process, the flow dynamics may be different depending on the region of the flow and the scales of the involved liquid structures. Exploring this multi-scale, multi-dimensional phenomenon requires some new theoretical tools, some of which need yet to be elaborated. Here, a new analytical framework is proposed on the basis of two-point statistical equations of the liquid volume fraction. This tool, which originates from single phase turbulence, allows us notably to decompose the fluxes of liquid in flow–position space and scale space. Direct numerical simulations of liquid–gas turbulence decaying in a triply periodic domain are then used to characterize the time and scale evolution of the liquid volume fraction. It is emphasized that two-point statistics of the liquid volume fraction depend explicitly on the geometrical properties of the liquid–gas interface and in particular its surface density. The stretch rate of the liquid–gas interface is further shown to be the equivalent for the liquid volume fraction (a non-diffusive scalar) of the scalar dissipation rate. Finally, a decomposition of the transport of liquid in scale space highlights that non-local interactions between non-adjacent scales play a significant role

The 3D structure of an active region filament as extrapolated from photospheric and chromospheric observations

The 3D structure of an active region (AR) filament is studied using nonlinear force-free field (NLFFF) extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 \AA\ line and the He I 10830 \AA\ triplet obtained with the Tenerife Infrared Polarimeter (TIP) at the VTT (Tenerife). The two extrapolations have been carried out independently from each other and their respective spatial domains overlap in a considerable height range. This opens up new possibilities for diagnostics in addition to the usual ones obtained through a single extrapolation from, typically, a photospheric layer. Among those possibilities, this method allows the determination of an average formation height of the He I 10830 \AA\ signal of \approx 2 Mm above the surface of the sun. It allows, as well, to cross-check the obtained 3D magnetic structures in view of verifying a possible deviation from the force- free condition especially at the photosphere. The extrapolations yield a filament formed by a twisted flux rope whose axis is located at about 1.4 Mm above the solar surface. The twisted field lines make slightly more than one turn along the filament within our box, which results in 0.055 turns/Mm. The convex part of the field lines (as seen from the solar surface) constitute dips where the plasma can naturally be supported. The obtained 3D magnetic structure of the filament depends on the choice of the observed horizontal magnetic field as determined from the 180\circ solution of the azimuth. We derive a method to check for the correctness of the selected 180\circ ambiguity solution.Comment: 31 pages, 13 figures, ApJ Accepte

The Construction and (Re)Construction of Mentoring Relations, Conversations, Observations and Cameras

The purpose of this study is to better understand mentoring as a relational process. Employing a constructionist form of Action Research called ‘Appreciative Inquiry’ (AI), twelve teachers, six pairs of Mentors and Newly Qualified Teachers explored through their joint actions with a digital camera, alternative forms of ‘observation’ and ‘feedback’ practices. The study took a fresh theoretical approach to mentoring, enabling the teachers to focus on the ‘positive’ aspects of their mentoring experiences. This approach provided constructionist tools with which to analyse the teachers’ experiences. These included ‘joint action’ (Shotter, 1993); the application of ‘in-vivo’ and ‘values’ coding (Saldana, 2009) and a form of discourse analysis known as ‘Interpretative Repertoires’ (Wetherell and Potter, 1988). Emerging themes showed how the teachers developed an understanding of how they co-constructed their observation and feedback practices; developed their teaching identities; and how filming enabled them to see how their practices connected or disconnected them to children’s learning; resources; the environment; and to the wider school and beyond. Findings show how co-constructed learning with a digital camera can support the professional development of both Mentors and Newly Qualified Teachers as part of the induction process, through everyday local mentoring practices. It also shows how mentoring practices can be more effectively aligned with the GTCS (2012) Standards. This small co-study addresses issues raised in key ‘policy’ texts shaping mentoring practices in Scottish education. For these continue to highlight the need for coherence in the language of ‘mentoring’; how ‘feedback’ might be more productive in supporting Newly Qualified Teachers; how training for Mentors is required and how pedagogical skills might be enhanced through the Mentoring Process (Evaluation of Teaching Scotland’s Future, Scottish Government, March 2016)

Liquid transport in scale space

When a liquid stream is injected into a gaseous atmosphere, it destabilizes and continuously passes through different states characterized by different morphologies. Throughout this process, the flow dynamics may be different depending on the region of the flow and the scales of the involved liquid structures. Exploring this multi-scale, multi-dimensional phenomenon requires some new theoretical tools, some of which need yet to be elaborated. Here, a new analytical framework is proposed on the basis of two-point statistical equations of the liquid volume fraction. This tool, which originates from single phase turbulence, allows notably to decompose the fluxes of liquid in flow-position space and scale space. Direct Numerical Simulations of liquid-gas turbulence decaying in a triply periodic domain are then used to characterize the time and scale evolution of the liquid volume fraction. It is emphasized that two-point statistics of the liquid volume fraction depend explicitly on the geometrical properties of the liquid-gas interface and in particular its surface density. The stretch rate of the liquid-gas interface is further shown to be the equivalent for the liquid volume fraction (a non diffusive scalar) of the scalar dissipation rate. Finally, a decomposition of the transport of liquid in scale space highlights that non-local interactions between non adjacent scales play a significant role

French translation and validation of the Jefferson Scale of Empathy - Health Professions Student version

Background: Background: Jefferson Scale of Empathy is one of the most widely used tools worldwide to assess empathy. The extended version for Health Professions Students (JSE HPS) has not yet been translated into French. Objective: The aim of our study was to translate the JSE HPS into French and assess the psychometric properties of this new version (JSE HPS Fr). Methods: The JSE HPS was translated according to international recommendations. The main psychometric qualities (test-retest reliability, internal consistency, floor and ceiling effects and construct validity) were studied in a sample of physiotherapy students. Participants provided general information (age, gender, year of study) and completed the JSE HPS Fr and the Questionnaire of Cognitive and Affective Empathy (QCAE). Participants were also asked to complete the JSE-HPS-Fr again one week later to assess its test-retest reliability. Results: 408 students (161 males and 247 females; mean age: 21.3 years) participated. The JSE HPS Fr demonstrated good test-retest reliability for the total score (ICC=0.81) and good internal consistency (α Cronbach: 0.79). The JSE HPS also showed good convergent validity with the QCAE questionnaire (r=0.41, p<0.05). No floor or ceiling effects were observed. Conclusions: The results indicate that the JSE HPS Fr is a valid and reliable tool to assess the level of empathy of French-speaking physiotherapy students

Observation of the Halo of NGC 3077 Near the "Garland" Region Using the Hubble Space Telescope

We report the detection of upper main sequence stars and red giant branch stars in the halo of an amorphous galaxy, NGC3077. The observations were made using Wide Field Planetary Camera~2 on board the Hubble Space Telescope. The red giant branch luminosity function in I-band shows a sudden discontinuity at I = 24.0 +- 0.1 mag. Identifying this with the tip of the red giant branch (TRGB), and adopting the calibration provided by Lee, Freedman, & Madore (1993) and the foreground extinction of A_B = 0.21 mag, we obtain a distance modulus of (m-M)_0 = 27.93 +- 0.14(random) +- 0.16(sys). This value agrees well with the distance estimates of four other galaxies in the M81 Group. In addition to the RGB stars, we observe a concentration of upper main sequence stars in the halo of NGC3077, which coincides partially with a feature known as the ``Garland''. Using Padua isochrones, these stars are estimated to be <150 Myrs old. Assuming that the nearest encounter between NGC3077 and M81 occurred 280 Myrs ago as predicted by the numerical simulations (Yun 1997), the observed upper main sequence stars are likely the results of the star formation triggered by the M81-NGC3077 tidal interaction.Comment: 15 pages, 8 figures. Accepted for publication in Astrophysical Journa

Measurement of the transfered impendance of the shield cable by the impulse current method using a Fourier processor

This paper is an application of the Fast Fourier Transform for the measurement of the transfer impedance of the shielded cables at the frequencies above 100 MHz . In the first part we present an overview of the principle of the measurement of the transfer impedance . We describe the signal processing method used in this special case . The second part of the paper is related to the Fourier processor designed to compute the Fourier tansform in few seconds and for 2,048 signal samples . We give the main steps of the algorithm and the simplifications which have been used in the numerical code .Mesure de l'impédance de transfert de câbles blindés aux fréquences supérieures à 100 MH

Statistical models for over-dispersion in the frequency of peaks over threshold data for a flow series.

In a peaks over threshold analysis of a series of river flows, a sufficiently high threshold is used to extract the peaks of independent flood events. This paper reviews existing, and proposes new, statistical models for both the annual counts of such events and the process of event peak times. The most common existing model for the process of event times is a homogeneous Poisson process. This model is motivated by asymptotic theory. However, empirical evidence suggests that it is not the most appropriate model, since it implies that the mean and variance of the annual counts are the same, whereas the counts appear to be overdispersed, i.e., have a larger variance than mean. This paper describes how the homogeneous Poisson process can be extended to incorporate time variation in the rate at which events occur and so help to account for overdispersion in annual counts through the use of regression and mixed models. The implications of these new models on the implied probability distribution of the annual maxima are also discussed. The models are illustrated using a historical flow series from the River Thames at Kingston

Basic Studies of III-IV High Efficiency Cell Components

The objective of the project is to raise the understanding of dark current mechanisms in GaAs-related solar cells to a level comparable to that of silicon cells. Motivation for this work arises from the observation that much of the progress in crystalline silicon cell performance has occurred as a result of a very deep knowledge of the physics controlling the cell’s dark current. Based on this knowledge, new cell structures evolved to suppress dominant dark current mechanisms. A comparable level of knowledge of GaAs cell device physics does not yet exist, but will be essential if cell performance near the thermodynamic limit is to be achieved

An efficient semiparametric maxima estimator of the extremal index

The extremal index $\theta$, a measure of the degree of local dependence in the extremes of a stationary process, plays an important role in extreme value analyses. We estimate $\theta$ semiparametrically, using the relationship between the distribution of block maxima and the marginal distribution of a process to define a semiparametric model. We show that these semiparametric estimators are simpler and substantially more efficient than their parametric counterparts. We seek to improve efficiency further using maxima over sliding blocks. A simulation study shows that the semiparametric estimators are competitive with the leading estimators. An application to sea-surge heights combines inferences about $\theta$ with a standard extreme value analysis of block maxima to estimate marginal quantiles.Comment: 17 pages, 7 figures. Minor edits made to version 1 prior to journal publication. The final publication is available at Springer via http://dx.doi.org/10.1007/s10687-015-0221-