Valence band splitting in Cu2(Sn,Ge, Si)S3: effect on optical absorption spectra

in Physica Status Solidi. Rapid Research Letters (2017)

We perform a detailed analysis of the valence band splitting (VBS) effect on the absorption spectra of monoclinic Cu2(Sn,Ge,Si)S3 combining theory and experiment. We cal- culate the imaginary part of the ... [more ▼]

We perform a detailed analysis of the valence band splitting (VBS) effect on the absorption spectra of monoclinic Cu2(Sn,Ge,Si)S3 combining theory and experiment. We cal- culate the imaginary part of the dielectric function for all three compounds using hybrid functionals and maximally lo- calized Wannier functions in remarkably dense k-meshes to ensure an accurate description of the low energy spectral regime. We find that the VBS will affect the absorption spectra of these materials leading to multiple absorption onsets. Our experimental spectra on Cu2(Sn,Ge)S3, analysed using both Tauc plots and inflection points, verify this prediction. A good agreement between theory and experiment in terms of VBS values is recorded. [less ▲]

Valers Larve : Imitatio, Anagrammatik und die Macht der Philologie in Gotthold Ephraim Lessings 'Der junge Gelehrte'

in Ichtexte : Beiträge zur Philologie des Individuellen (2019)

Valeur attribuée au travail et santé mentale des détenis et des chômeurs de longue durée

Presentation (2008)

Plus les détenus du centre pénitentiaire de Givenich accordent une valeur positive au travail, meilleur est leur bien être psychologique. A l’opposé plus les chômeurs de longue durée de l’ADEM attribuent ... [more ▼]

Plus les détenus du centre pénitentiaire de Givenich accordent une valeur positive au travail, meilleur est leur bien être psychologique. A l’opposé plus les chômeurs de longue durée de l’ADEM attribuent de l’importance au rôle professionnel, plus leur santé mentale se dégrade. Plus le niveau d’instruction des personnes qui n’ont pas atteint la fin du cycle secondaire est faible, plus il est associé à un moins bon équilibre mental voir à un état dépressif. Détenus et chômeurs de longue durée en situation d’attente vers un retour à l'emploi nécessitent un véritable soutien psychologique et un accompagnement individualisé adaptés à leurs besoins. [less ▲]

Validated Variational Inference via Practical Posterior Error Bounds

in Proceedings of the 23rd International Conference on Artificial Intelligence and Statistics (AISTATS) (2020, June)

Validating Brouwer's Continuity Principle for Numbers Using Named Exceptions

in Mathematical Structures in Computer Science (2017)

Validating PISA 2015 collaborative problem solving by face-to-face, self-, and teacher report collaboration measures.

Scientific Conference (2018, April)

Validating the PISA 2015 collaborative problem solving approach

Poster (2015, September)

Validation and Psychometric Analysis of 32 cognitive item models spanning Grades 1 to 7 in the mathematical domain of numbers & operations

Scientific Conference (2022, November)

Today’s educational field has a tremendous hunger for valid and psychometrically sound items to reliably track and model students’ learning processes. Educational large-scale assessments, formative ... [more ▼]

Today’s educational field has a tremendous hunger for valid and psychometrically sound items to reliably track and model students’ learning processes. Educational large-scale assessments, formative classroom assessment, and lately, digital learning platforms require a constant stream of high-quality, and unbiased items. However, traditional development of test items ties up a significant amount of time from subject matter experts, pedagogues and psychometricians and might not be suited anymore to nowadays demands. Salvation is sought in automatic item generation (AIG) which provides the possibility of generating multiple items within a short period of time based on the development of cognitively sound item templates by using algorithms (Gierl & Haladyna, 2013; Gierl et al., 2015). The present study psychometrically analyses 35 cognitive item models that were developed by a team of national subject matter experts and psychometricians and then used for algorithmically producing items for the mathematical domain of numbers & shapes for Grades 1, 3, 5, and 7 of the Luxembourgish school system. Each item model was administered in 6 experimentally varied versions to investigate the impact of a) the context the mathematical problem was presented in, and b) problem characteristics which cognitive psychology identified to influence the problem solving process. Based on samples from Grade 1 (n = 5963), Grade 3 (n = 5527), Grade 5 (n = 5291), and Grade 7 (n = 3018) collected within the annual Épreuves standardisées, this design allows for evaluating whether psychometric characteristics of produced items per model are a) stable, b) can be predicted by problem characteristics, and c) are unbiased towards subgroups of students (known to be disadvantaged in the Luxembourgish school system). After item calibration using the 1-PL model, each cognitive model was analyzed in-depth by descriptive comparisons of resulting IRT parameters, and the estimation of manipulated problem characteristics’ impact on item difficulty by using the linear logistic test model (LLTM, Fischer, 1972). Results are truly promising and show negligible effects of different problem contexts on item difficulty and reasonably stable effects of altered problem characteristics. Thus, the majority of developed cognitive models could be used to generate a huge number of items (> 10.000.000) for the domain of numbers & operations with known psychometric properties without the need for expensive field-trials. We end with discussing lessons learned from item difficulty prediction per model and highlighting differences between the Grades. References: Fischer, G. H. (1973). The linear logistic test model as an instrument in educational research. Acta Psychologica, 36, 359-374. Gierl, M. J., & Haladyna, T. M. (Eds.). (2013). Automatic item generation: Theory and practice. New York, NY: Routledge. Gierl, M. J., Lai, H., Hogan, J., & Matovinovic, D. (2015). A Method for Generating Educational Test Items That Are Aligned to the Common Core State Standards. Journal of Applied Testing Technology, 16(1), 1–18. [less ▲]

Validation and verification in domain-specific modeling method engineering: an integrated life-cycle view

in Software and Systems Modeling (2022)

Validation d’une typologie pour l’étude des dispositifs hybrides

in Education et Formation (n.d.)