Low Power AC-DC and DC-DC Multilevel Converters

AC-DC power electronic converters are widely used for electrical power conversion in many industrial applications such as for telecom equipment, information technology equipment, electric vehicles, space power systems and power systems based on renewable energy resources. Conventional AC-DC converters generally have two conversion stages – an AC-DC front-end stage that operates with some sort of power factor correction to ensure good power quality at the input, and a DC-DC conversion stage that takes the DC output of the front-end converter and converts it to the desired output DC voltage. Due to the cost of having two separate and independent converters, there has been considerable research on so-called single-stage converters – converters that can simultaneously perform AC-DC and DC-DC conversion with only a single converter stage. In spite of the research that has been done on AC-DC single-stage, there is still a need for further research to improve their performance. The main focus of this thesis is on development of new and improved AC-DC single-stage converters that are based on multilevel circuit structures (topologies) and principles instead of conventional two-level ones. The development of a new DC-DC multilevel converter is a secondary focus of this thesis. In this thesis, a literature survey of state of the art AC-DC and DC-DC converters is performed and the drawbacks of previous proposed converters are reviewed. A variety of new power electronic converters including new single-phase and three-phase converters and a new DC-DC converter are then proposed. The steady-state characteristics of each new converter is determined by mathematical analysis, and, once determined, these characteristics are used to develop a procedure for the design of key converter components. The feasibility of all new converters is confirmed by experimental results obtained from proof-of-concept prototype converters. Finally, the contents of the thesis are summarized and conclusions about the effectiveness of using multilevel converter principles to improve the performance of AC-DC and DC-DC converters are made

Predatory Journals and Perished Articles; a Letter to Editor

In recent years, academic publishing has been faced with many destructive phenomena. “Predatory publishers” (or journals) are one challenge for  cholarly publishing. This term was introduced to academic societies for the first time by Jeffrey Beall in 2010. This letter to editor is about predatory journals and perished articles in the field of emergency medicine

Modeling and Modulation of NNPC Four-Level Inverter for Solar Photovoltaic Power Plant

Photovoltaic (PV) power plant is an attractive way of utilizing the solar energy. For high-power PV power plant, the multilevel inverter is of potential interest. In contrast to the neutral-point clamped (NPC) or flying capacitor (FC) multilevel inverter, the nested neutral point clamped (NNPC) four-level inverter has better features for solar photovoltaic power plant. In practical applications, the common mode voltage reduction of the NNPC four-level is one of the important issues. In order to solve the problem, a new modulation strategy is proposed to minimize the common mode voltage. Compared with the conventional solution, our proposal can reduce the common mode voltage to 1/18 of the DC bus voltage. Moreover, it has the capability to balance the capacitor voltages. Finally, we carried out time-domain simulations to test the performance of the NNPC four-level inverter

The Effect of Tea-Cinnamon and Melissa officinalis L. Aqueous Extraction, on Neuropsychology Distress, Biochemical and Oxidative Stress Biomarkers in Glass Production Workers

Abstract Medicinal plants are considered as natural sources of antioxidant compounds which may protect organisms against oxidative stresses. The aim of this study was to evaluate the potential of Cinnamon and Melissa officinalis L. (Lemon balm) on the improvement of oxidative stress in glass production workers. This clinical study was conducted on 32 glass production workers. They were asked to use 0.5 g of tea-Cinnamon and 3 g of Lemon balm as infusion for 30 days in the morning and evening each day. At the beginning and the end of the study, blood samples were taken from individuals to determine the level of fasting blood suger (FBS), aspartate transaminase (AST), alanintransferase (ALT), triglyceride (TG), cholesterol (CL), low-density lipoprotein (LDL), high-density lipoprotein(HDL) levels, lipid peroxidation (LPO), total antioxidant capacity (TAC) and sillies were measured in workers' blood. At the end of experiment, data were subjected to the paired t-test analysis. Clinical examination was accomplished to record any abnormal signs or symptoms. After treatment, the high-density lipoprotein and TAC of serum significantly increased while the AST and LPO decreased. There were positive correlations between work history and initiative energy disorder of cognitive test. Probably tea-Cinnamon and Lemon balm possesses marked an-* Corresponding author. M. Rashidi et al. 2593 tioxidant activity and, therefore, it can be used to protect individuals from the oxidative stresses. Using supplementary antioxidants may be helpful in the treatment of workers

Effect of music on driving performance and physiological and psychological indicators: A systematic review and meta-analysis study

Background: Many studies have assessed the effect of music on driving. However, their results are very scattered and contradictory. Therefore, this systematic review is conducted to determine the effect of music on driving performance and drivers’ physiological and psychological indicators. Methods: Scopus, PubMed, and Web of Science databases were searched until July 2023. A manual search in Google Scholar for gray literature was conducted. The Simulation Research Rubric (SRR) tool was used to assess the reporting quality of the studies. Stata software (StataCorp, version 16) was used to perform a meta-analysis. Results: A total of 2650 records were identified. The findings of 19 studies were analyzed. Most of them were carried out in high-income countries (HICs) using simulators. The most frequently used music style was classic rock. The meta-analysis results indicated that music with high and medium volume increases the average driving speed, and music with low volume decreases it. Although music in every mood reduces the average reaction time, it positively reduces response delay and increases coherence. Music with high volume decreases the heart rate, but music with medium and low volume increases it. Listening to music increases the level of arousal and mental load. Conclusion: It was concluded that, in some indicators, listening to music has adverse effects on driving. However, in many indicators, music has a positive impact on improving driving safety. It is better to choose appropriate music for different driving conditions and to train the drivers about it

Clinical Significance and Different Expression of Dipeptidyl Peptidase IV and Procalcitonin in Mild and Severe COVID-19

Background: Coronavirus has become a global concern in 2019-20. The virus belongs to the coronavirus family, which has been able to infect many patients and victims around the world. The virus originated in the Chinese city of Wuhan, which eventually spread around the world and became a pandemic. Materials and Methods: A total of 60 Patients with severe (n=30) and mild (n=30) symptoms of COIVD-19 were included in this study. Peripheral blood samples were collected from the patients. Real-time PCR was used to compare the relative expression levels of Procalcitonin and dipeptidyl peptidase IV (DPPIV) in a patient with severe and mild Covid-19 infection. Results: Procalcitonin and dipeptidyl peptidase IV markers in the peripheral blood of patients with severe symptoms, were positive in 29 (96.60%) and 26 (86.60%), respectively (n=30); however, positive rates in the mild symptoms patients group were 27 (90%) and 25 (83.30%), respectively. There was a statistically significant difference between these two groups in terms of DDPIV and Procalcitonin (p<0.001). Conclusion: Procalcitonin and DPPIV increase in patients with COVID-19 infection, significantly higher in the patients with more severe clinical symptoms than those with milder ones. More studies will be needed to verify the reliability of the current findings. Keywords: Procalcitonin, DPPIV, Severe symptoms, Mild symptoms, COVID-1