A nature based novel maximum power point tracking algorithm for partial shading conditions

Introduction. The huge demand of green energy over past few decades have drawn the interest of scientists and researchers. Solar energy is the most abundant and easily available source but there have been so many problems with its optimum extraction of output. The factors affecting the maximum power point tracking of PV systems are input irradiance, temperature, load etc. The variations in irradiance level lead to partial shading that causes reduction in performance by not letting system to operate at maximum power point. Many methods have been proposed in literature to optimize the performance of PV systems but each method has shortcomings that have failed all of them. The actual problem occurs when partial shading is very strong; this is where most of the methods totally fail. So proposed work addresses this issue and solves it to the fullest. The novelty in the proposed work is that it introduces a new nature-based algorithm that works on the principle of plant propagation. It is a natural optimization technique that plants follow to survive and propagate in different environmental conditions. The proposed method efficiently tracks the global peak under all shading conditions and is simple to implement with high accuracy and tracking speed. Purpose. Building an algorithm that can track global peak of photovoltaic systems under all shading conditions and extracts the maximum possible power from the system, and is simple and easy to implement. Methods. The method is implemented in MATLAB / Simulink on an electrical model that uses a PV array model. Different shadings are applied to check for the results. Results. The results have shown that for different photovoltaic configurations the algorithm performs very good under uniform and partial shadings conditions. Its accuracy, tracking efficiency and tracking time has increased reasonably. Practical value. The project can be very beneficial to people as it enhances the performances of PV systems that can make them self-sufficient in electrical energy, focuses on sustainable development and reduces pollution. This way it can have huge impact on human life.

Assessment of Longitudinal Left Ventricular Function in Patients with Coronary Artery Ectasia by 2D Speckle Tracking Echocardiography

Background Coronary artery ectasia (CAE) is one of the uncommon cardiovascular disorders. CAE is one of the known risk factors for acute coronary syndrome, its incidence ranges from 1.5%-5% of patients undergoing coronary angiography, with predominance in males. Coronary artery ectasia (CAE) is defined as dilatation of an arterial segment to a diameter at least 1.5 times that of an adjacent normal artery and involves at least one third of the affected artery (1)(1). The exact pathogenesis of CAE is not well established; however, Coronary atherosclerosis is detected in more than 50% of the patients. Objective To evaluate global left ventricle longitudinal strain by 2D speckle tracking echocardiography in patients with coronary artery ectasia and without significant (>50%) coronary artery stenosis. Patients and Methods This study carried on sixty patients referred to cath lab of Ain Shams university hospital for elective coronary angiography during period between January 2018 and Augest 2019. The patients were divided in to two groups (Group A) included thirty patients with ectasia in one or more of the coronary arteries without any significant coronary artery stenosis and (Group B) included thirty patients with normal coronary angiographic findings serving as control group. Results The present study showed a statistically significant decrease in EF comparing CAE group to control group .As regards other echocardiography parameters, there was a highly significant difference of LVEDD, LVEDD index, LVESD,, LVESD index, LV mass, LV mass index, LA volume and LA volume index between the two groups. Global peak longitudinal strain showed highly significant difference between two groups as its mean value was significantly lower in the CAE group. Conclusion In our study, we have concluded that global peak longitudinal strain was significantly impaired in patients with coronary artery ectasia without significant coronary artery lesion denoting subclinical LV systolic dysfunction .LV diastolic dysfunction was more prevalent in coronary artery ectasia patients compared to control subjects.

Segmental Strain for Scar Detection in Acute Myocardial Infarcts and in Follow-up Exams using Non-Contrast CMR Cine Sequences

Background The purpose of the study was to investigate feasibility of infarct detection in segmental strain derived from non-contrast cardiac magnetic resonance (CMR) cine sequences in patients with acute myocardial infarction (AMI) and in follow-up (FU) exams.Methods57 patients with AMI (mean age 61 ± 12 years, CMR 2.8 ± 2 days after infarction) were retrospectively included, FU exams were available in 32 patients (35 ± 14 days after first CMR). 28 patients with normal CMR (47 ± 8 years) served as controls. Dedicated software (Segment CMR, Medviso) was used to calculate global and segmental strain derived from cine sequences. Cine short axis stacks and segmental circumferential strain calculations of every patient and control were presented to two blinded readers in random order, who were advised to identify potentially infarcted segments, blinded to LGE and clinical information. Results Impaired global strain was measured in AMI patients compared to controls (global peak circumferential strain [GPCS] p= 0.01; global peak longitudinal strain [GPLS] p= 0.04; global peak radial strain [GPRS] p= 0.01). In both imaging time points, mean segmental peak circumferential strain [SPCS] was impaired in infarcted tissue compared to remote segments (AMI: p=0.03, FU: p=0.02). SPCS values in infarcted segments were similar between AMI and FU (p=0.8), remote segments were marginally more impaired in AMI than in FU (p= 0.07). In SPCS calculations, 141 from 189 acutely infarcted segments were accurately detected (74.6%), visual evaluation of correlating cine images detected 44.4% infarcts. In FU, 81.5 % infarcted segments (93/114 segments) were detected in SPCS and 51.8% by visual evaluation of correlating short axis cine images (p=0.01).ConclusionSegmental circumferential strain derived from routinely acquired native cine sequences detects nearly 75 % of acute infarcts and about 80% of infarcts in subacute follow-up CMR, significantly more than visual evaluation of correlating cine images alone. Acute infarcts may display only subtle impairment of wall motion and no obvious wall thinning, thus SPCS calculation might be helpful for scar detection in patients with acute infarcts, when only cine images are available.

A Simple Method for Detecting Partial Shading in PV Systems

Partial shading conditions (PSCs) can significantly reduce the output energy produced by photovoltaic (PV) systems. Moreover, when such conditions occur, conventional and advanced maximum power point tracking (MPPT) systems fail to operate the PV system at its peak because the bypassing diodes may cause the PV system to become trapped at a low power point when they are in conduction mode. The PV system can be operated at the global maximum power point (MPP) with the help of global peak searching tools. However, the frequent use of these tools will reduce the output of PV systems since they force the PV system to operate outside its power region while scanning the I-V curve in order to determine the global MPP. Thus, the global peak searching tools should be deployed only when a PSC occurs. In this paper, a simple and accurate method is proposed for detecting PSCs by means of monitoring the sign of voltage changes (positive or negative). The method predicts a PSC if the sign of successive voltage changes is the same for a certain number of successive changes. The proposed method was tested on two types of PV array configurations (series and series–parallel) with several shading patterns emulated on-site. The proposed method correctly and timely identified all emulated shading patterns. It can be used to trigger the global MPP searching techniques for improving the PV system’s output under PSCs; furthermore, it can be used to notify the PV system’s operator of the occurrence of PSCs.

Myocardial Characterization in Patients with Nonischemic Dilated Cardiomyopathy Combined with Ventricular Arrhythmias: Insights from Cardiovascular Magnetic Resonance Feature Tracking

This study investigated the feasibility of using cardiovascular magnetic resonance feature tracking (CMR-FT) for analysis of left ventricular (LV) strain and strain rate in patients with non-ischemic dilated cardiomyopathy (NIDCM) combined with ventricular arrhythmias (VAs). And evaluated the correlation between the LV global strain and left ventricular ejection (LVEF). We performed a retrospective study in a cohort of 34 consecutive patients with NIDCM combined with VAs who underwent CMR examination in our hospital between January 2016 and December 2019. Global and segmental peak values of LV longitudinal, circumferential, radial strain, and systolic strain rate were analyzed. Pearson analysis was calculated to assess the correlation of LV global deformation and LVEF as well as the correlation of between LV global deformation. Compared with the healthy controls, the global peak radial strain (GPRS), global peak circumferential strain (GPCS), and global peak longitudinal strain (GPLS) were significantly reduced in patients with NIDCM combined with VAs (P < 0.001, respectively). Additionally, Pearson analysis showed GPCS negatively correlated with LVEF (r=-0.946, P < 0.001), GPLS negatively correlated with LVEF (r=-0.860, P < 0.001), and GPRS positively correlated with LVEF (r = 0.920, P < 0.001). CMR-FT is a feasible and promising technique for assessing LV myocardial deformation of patients with NIDCM combined with VAs. And, GPCS was better negatively correlated with LVEF and higher reproducibility of intra-class correlation coefficient (ICC), which can help to guide clinical treatment and have great implication on clinical decision.

Segmental Strain for Myocardial Scar Detection in Acute Infarcts and Follow-Up CMR Using Non-Contrast Cine Images

Aims Scar tissue from myocardial infarction is best visualized with cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE). Gadolinium-free alternatives for detection of myocardial scars are limited. This study investigated the feasibility of myocardial scar detection in acute infarcts and follow-up CMR using non-contrast cine images. Methods Fifty-seven patients with acute infarcts (15 female, mean age 61 ± 12 years, CMR 2.8 ± 2 days after infarction) were retrospectively evaluated with follow-up CMR exams available in thirty-two patients (9 female, 35 ± 14 days after infarction). Twenty-eight patients with normal CMR scans (2 female, mean age 47 ± 8 years) served as controls. Global and segmental strain parameters (global peak circumferential [GPCS], global peak longitudinal [GPLS], global peak radial strain [GPRS], segmental peak circumferential [SPCS], segmental peak longitudinal [SPLS], and segmental peak radial strain [SPRS]) were calculated from standard non-contrast balanced SSFP cine sequences using commercially available software (Segment CMR, Medviso, Sweden). Visual assessment of wall motion abnormalities on short axis cine images, as well as segmental circumferential strain calculations (endo-/epicardially contoured short axis cine and resulting polar plot strain map) of every patient (acute imaging and follow-up CMR) and control were presented for two blinded readers in random order, who were advised to localize potentially infarcted segments, blinded to LGE images and clinical information.Results While global strain values were impaired in patients with acute infarcts compared to controls (GPCS p= 0.01; GPLS p= 0.04; GPRS p= 0.01), global strain was similar between first CMR and follow-up imaging in the subgroup of 32 patients (GPCS p= 0.7; GPLS p=0.8; GPRS p=0.2). In acute infarcts and in follow-up CMR, patients had reduced mean SPCS in infarcted segments compared to remote myocardium (acute p= 0.03, follow-up exams p= 0.02). SPCS values in infarcted areas were similar in acute infarcts and in follow-up exams (p=0.8). In acute infarcts 74.6% of all in LGE infarcted segments (141/189) were correctly localized in polar plot strain maps compared to 44.4% (84/189) of infarcted segments detected by visual wall motion assessment only (p < 0.01). In follow-up exams, 81.5% of all in LGE infarcted segments (93/114 segments) were correctly localized in polar plot strain maps compared to 51.8% (59/114) of infarcted segments detected by visual wall motion assessment (p < 0.01).Conclusion Segmental circumferential strain derived from routinely acquired cine sequences detects nearly 75% acute infarcts and about 80% of infarcts in follow-up CMR and can potentially be used for scar identification based on non-contrast cine images, when gadolinium cant not be applied or LGE images are not available.

Segmental strain analysis for the detection of chronic ischemic scars in non-contrast cardiac MRI cine images

Cardiac magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) is considered the gold standard for scar detection after myocardial infarction. In times of increasing skepticism about gadolinium depositions in brain tissue and contraindications of gadolinium administration in some patient groups, tissue strain-based techniques for detecting ischemic scars should be further developed as part of clinical protocols. Therefore, the objective of the present work was to investigate whether segmental strain is noticeably affected in chronic infarcts and thus can be potentially used for infarct detection based on routinely acquired non-contrast cine images in patients with known coronary artery disease (CAD). Forty-six patients with known CAD and chronic scars in LGE images (5 female, mean age 52 ± 19 years) and 24 gender- and age-matched controls with normal cardiac MRI (2 female, mean age 47 ± 13 years) were retrospectively enrolled. Global (global peak circumferential [GPCS], global peak longitudinal [GPLS], global peak radial strain [GPRS]) and segmental (segmental peak circumferential [SPCS], segmental peak longitudinal [SPLS], segmental peak radial strain [SPRS]) strain parameters were calculated from standard non-contrast balanced SSFP cine sequences using commercially available software (Segment CMR, Medviso, Sweden). Visual wall motion assessment of short axis cine images as well as segmental circumferential strain calculations (endo-/epicardially contoured short axis cine and resulting polar plot strain map) of every patient and control were presented in random order to two independent blinded readers, which should localize potentially infarcted segments in those datasets blinded to LGE images and patient information. Global strain values were impaired in patients compared to controls (GPCS p = 0.02; GPLS p = 0.04; GPRS p = 0.01). Patients with preserved ejection fraction showed also impeded GPCS compared to healthy individuals (p = 0.04). In patients, mean SPCS was significantly impaired in subendocardially (− 5.4% ± 2) and in transmurally infarcted segments (− 1.2% ± 3) compared to remote myocardium (− 12.9% ± 3, p = 0.02 and 0.03, respectively). ROC analysis revealed an optimal cut-off value for SPCS for discriminating infarcted from remote myocardium of − 7.2% with a sensitivity of 89.4% and specificity of 85.7%. Mean SPRS was impeded in transmurally infarcted segments (15.9% ± 6) compared to SPRS of remote myocardium (31.4% ± 5; p = 0.02). The optimal cut-off value for SPRS for discriminating scar tissue from remote myocardium was 16.6% with a sensitivity of 83.3% and specificity of 76.5%. 80.3% of all in LGE infarcted segments (118/147) were correctly localized in segmental circumferential strain calculations based on non-contrast cine images compared to 53.7% (79/147) of infarcted segments detected by visual wall motion assessment (p > 0.01). Global strain parameters are impaired in patients with chronic infarcts compared to controls. Mean SPCS and SPRS in scar tissue is impeded compared to remote myocardium in infarcts patients. Blinded to LGE images, two readers correctly localized 80% of infarcted segments in segmental circumferential strain calculations based on non-contrast cine images, in contrast to only 54% of infarcted segments detected due to wall motion abnormalities in visual wall motion assessment. Analysis of segmental circumferential strain shows a promising method for detection of chronic scars in routinely acquired, non-contrast cine images for patients who cannot receive or decline gadolinium.

A Bayesian fusion technique for maximum power point tracking under partial shading condition

In this paper, a Bayesian fusion technique (BFT) based on maximum power point tracking (MPPT) is developed for the photovoltaic (PV) system that can exhibit faster and accurate tracking under partially shaded conditions (PSCs). Although the conventional hill-climbing algorithms have fast tracking capabilities, they are prone to steady-state oscillations and may not guarantee global peak under partially shaded conditions. Contrarily, the meta-heuristic-based techniques may promise a global peak solution, but they are computationally inefficient and take significant time for tracking. To address this problem, a BFT is proposed which combines the solutions obtained from conventional incremental conductance algorithm and Jaya optimization algorithm to produce better responses under various PSCs. The effectiveness of the proposed BFT-based MPPT is evaluated by comparing it with various MPPT methods, viz. incremental conductance, particle swarm optimization (PSO), and Jaya optimization algorithms in MATLAB/Simulink environment. From the various case studies carried, the overall average tracking speed with more than 99% accuracy is less than 0.25 s and having minimum steady-state oscillations. Even under the wide range of partially shaded conditions, the proposed method exhibited superior MPPT compared to the existing methods with tracking speed less than 0.1 s to achieve 99.8% tracking efficiency. A detailed comparison table is provided by comparing with other popular existing MPPT methodologies.

The Prognostic Value of Left Atrial Global Longitudinal Strain and Left Atrial Phasic Volumes in Patients Undergoing Transcatheter Valve Implantation for Severe Aortic Stenosis

Introduction: The changes and the prognostic implications of left atrial (LA) volumes (LAV), LA function, and vascular load in patients undergoing transcatheter aortic valve implantation (TAVI) for severe aortic stenosis (AS) are less known. Methods: We enrolled 150 symptomatic patients (mean age 82 ± 8 years, 58% female, and pre-TAVI aortic valve area 0.40 ± 0.19 cm/m2) with severe AS who underwent 2D transthoracic echocardiography and 2D speckle tracking echocardiography at average 21 ± 35 days before and 171 ± 217 days after TAVI. The end point was a composite of new onset of atrial fibrillation, hospitalization for heart failure and all-cause death (major adverse cardiac events [MACE]). Results: After TAVI, indexed maximal LA volume and minimum volume of the LA decreased by 2.1 ± 10 mL/m2 and 1.6 ± 7 mL/m2 (p = 0.032 and p = 0.011, respectively), LA function index increased by 6.8 ± 11 units (p < 0.001), and LA stiffness decreased by 0.38 ± 2.0 (p = 0.05). No other changes in the LA phasic volumes, emptying fractions, and vascular load were noted. Post-TAVI, both left atrial and ventricular global peak longitudinal strain improved by about 6% (p = 0.01 and 0.02, respectively). MACE was reached by 37 (25%) patients after a median follow-up period of 172 days (interquartile range, 20–727). In multivariable models, MACE was associated with both pre- and post-TAVI LA global peak longitudinal strain (hazard ratio [HR] 0.75, CI 0.59–0.97; and HR 0.77, CI 0.60–1.00, per 5 percentage point units, respectively), pre-TAVI LV global endocardial longitudinal strain (HR 1.37, CI 1.02–1.83 per 5 percentage point units), and with most of the LA phasic volumes. Conclusion: Within 6 months after TAVI, there is reverse LA remodeling and an improvement in LA reservoir function. Pre- and post-TAVI indices of LA function and volume remain independently associated with MACE. Larger studies enrolling a greater diversity of patients may provide sufficient evidence for the utilization of these imaging biomarkers in clinical practice.

MPPT-based on Bat algorithm for photovoltaic systems working under partial shading conditions

Under partial shading conditions (PSC), most traditional maximum power point tracking (MPPT) techniques may not adopt GP (global peak). These strategies also often take a considerable amount of time to reach a full power point (MPP). Such obstacles can be eliminated by the use of metaheuristic strategies. This paper shows, in partial shading conditions, the MPPT technique for the photovoltaic system using the Bat Algorithm (BA). Simulations have been performed in the MATLAB ®/Simulink setting to verify the efficacy of the proposed method. In MPPT applications, the results of the simulations emphasize the precision of the proposed technique. The algorithm is also simple and efficient, on a low-cost microcontroller, it could be implemented. Hardwar in loop (HIL) validation is performed, with a Typhoon HIL 402 setup.