Al-Ashtari, W., Hunstig, M., Hemsel, T., &; Sextro, W. (2013). Increasing the power of piezoelectric energy harvesters by magnetic stiffening. Journal of Intelligent Material Systems and Structures, 24(11), 1332–1342.https://doi.org/10.1177/1045389X13483021 
LibreCat: /record/9794
DOI: 10.1177/1045389X13483021

Al-Ashtari, W., Hunstig, M., Hemsel, T., &; Sextro, W. (2013). Enhanced energy harvesting using multiple piezoelectric elements: Theory and experiments. Sensors and Actuators A: Physical, 200, 138–146.https://doi.org/10.1016/j.sna.2013.01.008 
LibreCat: /record/9795
DOI: 10.1016/j.sna.2013.01.008

Al-Ashtari, W., Hunstig, M., Hemsel, T., &; Sextro, W. (2013). 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 (pp. 159–161). Hannover, Germany.
LibreCat: /record/9796

Hunstig, M., Al-Ashtari, W., Hemsel, T., &; Sextro, W. (2013). Leistungs- und Bandbreitensteigerung von Energy-Harvesting-Generatoren für Energieautarke Systeme. In J. Gausemeier, R. Dumitrescu, F.  Rammig, W. Schäfer, &; A. Trächtler (Eds.), 9. Paderborner Workshop Entwurf mechatronischer Systeme (pp. 359–372). Paderborn: Heinz Nixdorf Institut, Universität Paderborn.
LibreCat: /record/9801

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

Al-Ashtari, W., Hunstig, M., Hemsel, T., &; Sextro, W. (2012). Frequency tuning of piezoelectric energy harvesters by magnetic force. Smart Materials and Structures, 21(3), 035019.
LibreCat: /record/9781

Al-Ashtari, W., Hunstig, M., Hemsel, T., &; Sextro, W. (2012). Analytical determination of characteristic frequencies and equivalent circuit parameters of a piezoelectric bimorph. Journal of Intelligent Material Systems and Structures, 23(1), 15–23.https://doi.org/10.1177/1045389X11430742 
LibreCat: /record/9782
DOI: 10.1177/1045389X11430742