Search

Your search keyword '"Sommer, D."' showing total 725 results
Start Over Author "Sommer, D."
725 results on '"Sommer, D."'

7. Double electron capture searches in $^{74}$Se

Author

Lehnert, B., Wester, T., Degering, D., Sommer, D., Wagner, L., and Zuber, K.

Subjects
Nuclear Experiment
Abstract

A search for various double electron capture modes of $^{74}$Se has been performed using an ultralow background Ge-detector in the Felsenkeller laboratory, Germany. Especially for the potentially resonant transition into the 1204.2 keV excited state of $^{74}$Ge a lower half-life limit of $0.70\cdot 10^{19}$ yr (90% credibility) has been obtained. Serious concerns are raised about the validity of obtained $^{74}$Se limits in some recent publications.

Published
2016
Full Text
View/download PDF

16. High-fidelity damage modelling of CFRP laminates for impact and crashworthiness applications – dynamic tube crushing simulations

Author

Sommer D. E., Thomson D., Falcó O., Quino G., Cui H., and Petrinic N.

Subjects
Physics, QC1-999
Abstract

Drop weight impact experiments were conducted on angle-ply carbon fibre reinforced polymer (CFRP) composite crush tubes. The dynamic response was modelled using explicit finite element methods and continuum damage mechanics and cohesive zone modelling in both Abaqus/Explicit and LS-DYNA. User-defined constitutive models for the intra-ply behaviour were used and a fibre-aligned meshing technique was implemented. The results of the experiments and simulations are compared to evaluate accuracy of the different modelling techniques, highlighting the advantages and drawbacks of each approach. Among these, the choice of meshing strategy is shown to be especially important in capturing the physical propagation of cracks and damage mechanisms in CFRP laminates.

Published
2021
Full Text
View/download PDF

17. Numerical prediction of the ballistic performance of hygrothermally aged CFRP laminates using a multi-scale modelling approach

Author

Thomson D., Sommer D. E., Falcó O., Quino G., Cui H., Erice B., and Petrinic N.

Subjects
Physics, QC1-999
Abstract

A multi-scale modelling strategy is proposed to investigate the potential effects of hygrothermal ageing on the ballistic performance of CFRP laminates. At the micro-scale, damage evolution due to cyclic hygrothermal loads is simulated on a representative microstructure using an adapted fatigue damage law. Then, the results of the micro-mechanical analysis are used to measure the predicted transverse crack density and calibrate a meso-scale material model with the effects of micro-scale damage. Finally, a meso-scale impact model is generated with seeded transverse cracks at the predicted crack density and the calibrated material properties from the homogenisation step, which allows for the performance of the laminate to be compared at different stages of hygrothermal ageing damage.

Published
2021
Full Text
View/download PDF

18. The role of expert evaluation for microsleep detection

Author

Golz M., Schenka A., Sommer D., Geißler B., and Muttray A.

Subjects
sleepiness, microsleep, driving simulation, eeg, eog, neural networks, support-vector machines, Medicine
Abstract

Recently, it has been shown by overnight driving simulation studies that microsleep density is the only known sleepiness indicator which rapidly increases within a few seconds immediately before sleepiness related crashes. This indicator is based solely on EEG and EOG and subsequent adaptive pattern recognition. Accurate microsleep recognition is very important for the performance of this sleepiness indicator. The question is whether expensive evaluations of microsleep events by a) experts are necessary or b) non-experts provide sufficient evaluations. Based on 11,114 microsleep events in case a) and 12,787 in case b) recognition accuracies were investigated utilizing (i) artificial neural networks and (ii) support-vector machines. Cross validated classification accuracies ranged between 92.2 % for (i,b) and 99.3 % for (ii, a). It is concluded that expert evaluations are very important to provide independent information for detecting microsleep.

Published
2015
Full Text
View/download PDF

22. Experimental analysis and simulation of low-velocity impact damage of composite laminates

Author

Falcó, O. (author), Lopes, C. S. (author), Sommer, D. E. (author), Thomson, D. (author), Ávila, R. L. (author), Tijs, B.H.A.H. (author), Falcó, O. (author), Lopes, C. S. (author), Sommer, D. E. (author), Thomson, D. (author), Ávila, R. L. (author), and Tijs, B.H.A.H. (author)

Abstract

The capability to accurately analyse the response of multi-directional composite laminates during impact events is of high importance for the design of lightweight aircraft structures. In this work, both experimental and numerical analyses are performed covering a large design-space of laminates for all aspects from on-set of damage and barely visible impact damage up to clearly visible impact damage and full penetration of the laminates. The impact tests are simulated using a sophisticated three-dimensional continuum damage model, combined with an automated meso-scale model generation algorithm for ply-by-ply, material/fibre-aligned meshing of laminated composite coupons. To assess the accuracy of the predictions, an extensive validation test program of several configurations and impact energies has been performed, thus demonstrating that the simulations are capable of accurately predicting the damage and failure mechanisms under low-velocity impact loading. Not only the evolution of impact loads and energy dissipated are numerically analysed, but the competition of the dominant failure mechanisms from low impact energy and full penetration cases are also macroscopically replicated., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Aerospace Structures & Computational Mechanics

Published
2022
Full Text
View/download PDF

25. Table-top X-ray magnetic circular dichroism at the Fe L edges

Author

Borchert, M., Tümmler, J., Sommer, D., Engel, D., Korff Schmising, C., Pfau, B., Schick, D., and Stefan Eisebitt

Abstract

We generate circularly-polarized soft X-rays from a laser-driven plasma source by a magnetic thin-film polarizer. This enables first lab-based X-ray magnetic circular dichroism experiments at the Fe L edges with picosecond time resolution.

Published
2022

28. Monte Carlo modelling for the in vivo lung monitoring of enriched uranium: Results of an international comparison

Author

Broggio, D., Bento, J., Caldeira, M., Cardenas-Mendez, E., Farah, J., Fonseca, T., Konvalinka, C., Liu, L., Perez, B., Capello, K., Cowan, P., Cruzate, J.-A., Freire, L., Gómez-Ros, J.-M., Gossio, S., Heide, B., Huikari, J., Hunt, J., Kinase, S., Kramer, G.H., Kurihara, O., Kyrieleis, A., Lebacq, A.-L., Leone, D., Li, C., Li, J., Mihailescu, L.-C., Moraleda, M., Navarro, J.-F., Oliveira, C., Puerta, N., Reichelt, U., Simões, C., Sommer, D., Takahashi, M., Teles, P., Vanhavere, F., Vrba, T., Franck, D., Gualdrini, G., and Lopez, M.-A.

Published
2012
Full Text
View/download PDF

41. Numerical prediction of the ballistic performance of hygrothermally aged CFRP laminates using a multi-scale modelling approach.

Author

Gálvez Díaz-Rubio, F., Cendón Franco, D. A., Thomson, D., Sommer, D. E., Falcó, O., Quino, G., Cui, H., Erice, B., and Petrinic, N.

Subjects
HYGROTHERMOELASTICITY, LAMINATED materials, MICROSTRUCTURE, MECHANICAL behavior of materials, DUCTILITY
Abstract

A multi-scale modelling strategy is proposed to investigate the potential effects of hygrothermal ageing on the ballistic performance of CFRP laminates. At the micro-scale, damage evolution due to cyclic hygrothermal loads is simulated on a representative microstructure using an adapted fatigue damage law. Then, the results of the micro-mechanical analysis are used to measure the predicted transverse crack density and calibrate a meso-scale material model with the effects of micro-scale damage. Finally, a meso-scale impact model is generated with seeded transverse cracks at the predicted crack density and the calibrated material properties from the homogenisation step, which allows for the performance of the laminate to be compared at different stages of hygrothermal ageing damage. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

42. High-fidelity damage modelling of CFRP laminates for impact and crashworthiness applications - dynamic tube crushing simulations.

Author

Gálvez Díaz-Rubio, F., Cendón Franco, D. A., Sommer, D. E., Thomson, D., Falcó, O., Quino, G., Cui, H., and Petrinic, N.

Subjects
CRASHWORTHINESS of automobiles, CARBON fiber testing, CRACK propagation (Fracture mechanics), LAMINATED materials, FINITE element method
Abstract

Drop weight impact experiments were conducted on angle-ply carbon fibre reinforced polymer (CFRP) composite crush tubes. The dynamic response was modelled using explicit finite element methods and continuum damage mechanics and cohesive zone modelling in both Abaqus/Explicit and LS-DYNA. User-defined constitutive models for the intra-ply behaviour were used and a fibre-aligned meshing technique was implemented. The results of the experiments and simulations are compared to evaluate accuracy of the different modelling techniques, highlighting the advantages and drawbacks of each approach. Among these, the choice of meshing strategy is shown to be especially important in capturing the physical propagation of cracks and damage mechanisms in CFRP laminates. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

48. Bimetallic reactivity. One-site additional two-metal oxidation reaction of dioxygen with a bimetallic dicobalt(II) complex bearing five-and six-coordinate sites

Author

Gavrilova, Anna L., Qin, Jin Q., Sommer, D., Rheingold, Arnold L., and Bosnich, B.

Subjects
Oxygen -- Chemical properties, Oxygen -- Atomic properties, Molecular structure -- Analysis, Cobalt -- Atomic properties, Oxidation-reduction reaction -- Analysis, Chemistry
Abstract

One-site addition two-metal oxidation reactions and interconversion of dioxygen binding modes in bimetallic complexes are discussed. The study reveals the facile transformation of dioxygen ligand in these complexes.

Published
2002

49. Effect of Intranasal Corticosteroid Treatment on Allergen Induced Changes in Numbers, Activation and Phenotype of Group 2 Innate Lymphoid Cells in Mild Allergic Rhinitics with Asthma

Author

Ju, X., primary, Xie, Y., additional, Beaudin, S., additional, Wiltshire, L., additional, Oliveria, J.-P., additional, MacLean, J., additional, Sommer, D., additional, Keith, P.K., additional, O’Byrne, P.M., additional, Li, O., additional, Banerjee, P., additional, Bauer, R., additional, Gauvreau, G.M., additional, and Sehmi, R., additional

Published
2020
Full Text
View/download PDF

50. Evaluation of the Reproducibility of Nasal Allergen Challenge in Mild Allergic Asthmatics to Support Drug Development

Author

Bauer, R., primary, Xie, Y., additional, Beaudin, S., additional, Wiltshire, L., additional, Wattie, J., additional, Munoz, C., additional, Alsaji, N., additional, Oliveria, J.-P., additional, MacLean, J., additional, Sommer, D., additional, Keith, P.K., additional, Ju, X., additional, Satia, I., additional, Cusack, R., additional, O'Byrne, P., additional, Sperinde, G., additional, Hokom, M., additional, Li, O., additional, Banerjee, P., additional, Smith, J., additional, Boucherat, E., additional, Staton, T., additional, Sehmi, R., additional, and Gauvreau, G.M., additional

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results