W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Increasing the power of piezoelectric energy harvesters by magnetic stiffening,” Journal of Intelligent Material Systems and Structures, vol. 24, no. 11, pp. 1332–1342, 2013.
LibreCat: /record/9794
DOI: 10.1177/1045389X13483021

W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Enhanced energy harvesting using multiple piezoelectric elements: Theory and experiments,” Sensors and Actuators A: Physical, vol. 200, pp. 138–146, 2013.
LibreCat: /record/9795
DOI: 10.1016/j.sna.2013.01.008

W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems,” in Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013, 2013, no. 05/2013, pp. 159–161.
LibreCat: /record/9796

M. Hunstig, W. Al-Ashtari, T. Hemsel, and W. Sextro, “Leistungs- und Bandbreitensteigerung von Energy-Harvesting-Generatoren für Energieautarke Systeme,” in 9. Paderborner Workshop Entwurf mechatronischer Systeme, 2013, pp. 359–372.
LibreCat: /record/9801

W. Al-Ashtari, Model based enhancement of an autonomous system with a piezoelectric harvester. Shaker, 2013.
LibreCat: /record/9792

W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Frequency tuning of piezoelectric energy harvesters by magnetic force,” Smart Materials and Structures, vol. 21, no. 3, p. 035019, 2012.
LibreCat: /record/9781

W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Analytical determination of characteristic frequencies and equivalent circuit parameters of a piezoelectric bimorph,” Journal of Intelligent Material Systems and Structures, vol. 23, no. 1, pp. 15–23, 2012.
LibreCat: /record/9782
DOI: 10.1177/1045389X11430742