Asymmetric Cascaded Multilevel Inverter with Unequal Dc Sources using SPWM and MSVPWM Topologies

This paper introduces the modeling design and simulation of seven and thirteen levels cascaded asymmetric multilevel inverter (MLI) with reduced number of switches.  MLI is the most efficient energy converters which are essentially appropriated for high power applications with decrease total harmonics distortion (THD). MLI doesn't only get high power in the output but it is also utilized in renewable energy resources such as fuel cells, wind and photovoltaic cells. This paper principally focuses on a hybrid cascaded MLI with two and three unequal dc supplies which decreases the number of semiconductor power switches. Sinusoidal PWM (SPWM) and modified space vector PWM (MSVPWM) techniques are used to improve an ac output with reduced THD. The gating pulses for seven and thirteen level hybrid cascaded converter using SPWM and MSVPWM techniques are introduced. The results of these proposed modulation strategies reduce the percentage magnitude of THD. The performance of the proposed SPWM and MSVPWM topologies are verified using seven and thirteen levels cascaded asymmetric MLI via simulink/matlab. Keywords: Sinusoidal Pulse Width Modulation (SPWM), Modified Space Vector Pulse Width Modulation (MSVPWM), Multilevel Inverter (MLI), Total Harmonics Distortion (THD)

Influence of limestone filler and of the size of the aggregates on DEF

This experimental study aims to determine the effect of limestone filler on concrete expansion due to delayed ettringite formation (DEF). Different mortars made with different sizes and percentages of limestone filler and Portland cement CEM I 52.5N are conserved in water. The expansion of the specimens is measured. Results show that DEF is not inhibited by limestone filler. The kinetics and the amplitude of the swelling depend on the size of the limestone filler. The volume fraction of aggregates changes only the kinetics: the relation between swelling and water uptake depends only on the size of the aggregates.Comment: 16 pages, 9 figures, 4 table

Knowledge about stroke among adults in Sharjah, United Arab Emirates

Background: In UAE, stroke is the second leading cause of disability after RTA, where annually 8,000 to 10,000 patients get a stroke. Our aim is to identify the knowledge levels of stroke among Sharjah’s adult citizens.Methods: Using self-administered questionnaires, in a cross-sectional design, a non-probability convenience sampling method was used to enrol subjects. Eligible subjects were above 18 years of age, comprehended Arabic or English, and are currently residing in Sharjah. The questionnaire was 17 questions structured in 5 sections which included: demographics, general knowledge, knowledge of signs and symptoms, risk factors, and appropriate response towards stroke. SPSS V.22 was used to analyse the data. Percentages, means, and ANOVA were used. A P-value less than 0.05 was considered to be statistically significant.Results: The study included 426 subjects, mean age was 35.1 years, 65.2% were females. 51.8% of the subjects claimed they know what stroke is, out of whom 24.3% provided incorrect descriptions. The mean knowledge level of signs and symptoms was 55.4%, and of risk factors was 40.6%. Visual disturbance was the least identified of the five signs and symptoms (38.0%). Female gender, African American race, and age above 60, were the least identified of the 8 risk factors (4.7%, 3.5%, 19.8% respectively). Better knowledge was associated with increased age and higher education. Conclusion: The majority of the sample showed an average to low level of knowledge. Such results indicate the importance of implementing more awareness programs that target younger age groups in the community

Short recipient warm ischemia time improves outcomes in deceased donor liver transplantation

While adverse effects of prolonged recipient warm ischemia time (rWIT) in liver transplantation (LT) have been well investigated, few studies have focused on possible positive prognostic effects of short rWIT. We aim to investigate if shortening rWIT can further improve outcomes in donation after brain death liver transplant (DBD-LT). Primary DBD-LT between 2000 and 2019 were retrospectively reviewed. Patients were divided according to rWIT (≤30, 31-40, 41-50, and \u3e50 min). The requirement of intraoperative transfusion, early allograft dysfunction (EAD), and graft survival were compared between the rWIT groups. A total of 1,256 patients of DBD-LTs were eligible. rWIT was ≤30min in 203 patients (15.7%), 31-40min in 465 patients (37.3%), 41-50min in 353 patients (28.1%), and \u3e50min in 240 patients (19.1%). There were significant increasing trends of transfusion requirement (P \u3c 0.001) and increased estimated blood loss (EBL, P \u3c 0.001), and higher lactate level (P \u3c 0.001) with prolongation of rWIT. Multivariable logistic regression demonstrated the lowest risk of EAD in the WIT ≤30min group. After risk adjustment, patients with rWIT ≤30 min showed a significantly lower risk of graft loss at 1 and 5-years, compared to other groups. The positive prognostic impact of rWIT ≤30min was more prominent when cold ischemia time exceeded 6 h. In conclusion, shorter rWIT in DBD-LT provided significantly better post-transplant outcomes