Search

Photovoltaic array characteristics with partial shading (PS) have multiple maximum power points (MPPs), and conventional algorithms have difficulties in tracking accurate global maximum power points (GMPPs). This study proposes a MPP tracking (MPPT) method based on improved water cycle optimization for fast-tracking the GMPP under PS conditions, along with a new strategy to enhance the convergence speed of the MPPT method during load variations. The experimental setup included a dc–dc single-ended primary inductance converter (SEPIC) and digital signal processing and control engineering (DSPACE) controller to assess the performance of the proposed method. The proposed method was also compared with the conventional water cycle optimization and six MPPT algorithms. The experimental results showed that the proposed method obtained an average tracking efficiency of 99.92% and a tracking time of 0.475 s for all PS tests. Moreover, it achieved a GMPP in a single perturbation step when the load change occurred, reducing the power loss in the photovoltaic (PV) system. The comparison showed that the proposed method performed better than the other MPPT methods in terms of tracking efficiency, convergence speed, and ease of implementation. This method could be utilized to implement developed PV systems with minimal losses.

Aim To investigate the difference in adhesion and rebubbling rate between eye bank and surgeon prepared Descemet membrane endothelial keratoplasty (DMEK) tissues. Methods Laboratory and clinical retrospective comparative interventional case series. Research corneal tissues were obtained for laboratory investigation. The clinical study involved patients with endothelial dysfunction who underwent DMEK surgery and tamponade with air. Tissues were stripped using a standard DMEK stripping technique (SCUBA) and shipped as prestripped or loaded in a 2.2 intra-ocular lens cartridge with endothelium facing inwards (preloaded) before transporting from the eye bank to the surgeon. For surgeon prepared tissues, all the grafts were stripped in the theatre and transplanted or stripped in the laboratory and tested immediately. Adhesion force and elastic modulus were measured in the centre and mid-periphery in a laboratory ex vivo investigation using atomic force microscopy, while rebubbling rates were recorded in the clinical study. Results There was no difference in endothelial cell viability between surgeon or eye bank prepared tissue. Surgeon-stripped DMEK grafts in the laboratory investigation showed significantly higher elastic modulus and adhesion force compared to prestripped and preloaded tissues (p<0.0001). In the clinical data, rebubbling rates of 48%, 40% and 15% were observed in preloaded, prestripped and surgeon-stripped DMEK grafts, respectively. Rebubbling rates were significantly associated with combined cataract surgery (p=0.009) and with time from harvesting the graft to the surgery (p=0.02). Conclusions Decreased adhesion forces and elastic modulus in eye bank prepared tissues may contribute to increased rebubbling rates. [ABSTRACT FROM AUTHOR]