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Modular Multilevel Converter Based STATCOM Topology Suitable for Medium-Voltage Unbalanced Systems
Hassan Mohammadi Pirouz,Mohammad Tavakoli Bina 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.5
This paper discusses a transformerless shunt static compensator (STATCOM) based on a modular multilevel converter (MMC). It introduces a new time-discrete appropriate current control algorithm and a phase-shifted carrier modulation strategy for fast compensation of the reactive power and harmonics, and also for the balancing of the three-phase source side currents. Analytical formulas are derived to demonstrate the accurate mechanism of the stored energy balancing inside the MMC. Various simulated waveforms verify that the MMC based STATCOM is capable of reactive power compensation, harmonic cancellation, and simultaneous load balancing, while controlling and balancing all of the DC mean voltages even during the transient states.
( Mohammad Hassan Golzari ),( Mohammad Hassan Javanbakht ),( Ehsan Ghaedi ),( Hamed Mohammadi ),( Mahmoud Djalali ) 한국임상영양학회 2019 Clinical Nutrition Research Vol.8 No.1
Type 2 diabetes mellitus (T2DM) is recognized as one of the most prevalent metabolic diseases, and it is mostly associated with oxidative stress, atherosclerosis and dyslipidemia. Paraoxonase 2 (PON2) due to its antioxidant properties may play a role in the atherosclerosis development. Although long-chain omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) have been shown to reduce the risk of cardiovascular disease, the exact mechanism of action is still unknown. Our goal in this study was to determine the effect of EPA administration on gene expression of PON2 in patients with T2DM. Present study was a randomized, controlled double-blind trial. Thirty-six patients with T2DM were randomly allocated to receive 2 g/day EPA (n = 18) or placebo (n = 18) for 8 weeks. There were no significant differences between 2 groups concerning demographic or biochemical variables, and dietary intakes as well (p > 0.05). However, patients received EPA showed a significant increase in the gene expression of PON2 compared with placebo group (p = 0.027). In addition, high-density lipoprotein cholesterol increased and fasting blood sugar decreased significantly after EPA supplementation compared with control group. Taken together, supplementation with 2 g/day EPA could be atheroprotective via the upregulation of PON2 in patients with T2DM.
Modular Multilevel Converter Based STATCOM Topology Suitable for Medium-Voltage Unbalanced Systems
Pirouz, Hassan Mohammadi,Bina, Mohammad Tavakoli The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.5
This paper discusses a transformerless shunt static compensator (STATCOM) based on a modular multilevel converter (MMC). It introduces a new time-discrete appropriate current control algorithm and a phase-shifted carrier modulation strategy for fast compensation of the reactive power and harmonics, and also for the balancing of the three-phase source side currents. Analytical formulas are derived to demonstrate the accurate mechanism of the stored energy balancing inside the MMC. Various simulated waveforms verify that the MMC based STATCOM is capable of reactive power compensation, harmonic cancellation, and simultaneous load balancing, while controlling and balancing all of the DC mean voltages even during the transient states.
Majid Mohammadi,Mehdi Sedighi,Rajamohan Natarajan,Sedky Hassan Aly Hassan,Mostafa Ghasemi 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.1
Oilfield produced water is one of the vast amounts of wastewater that pollute the environment and cause serious problems. In this study, the produced water was treated in a microbial fuel cell (MFC), and response surface methodology and central composite design (RSM/CCD) were used as powerful tools to optimize the process. The results of two separate parameters of sulfonated poly ether ether ketone (SPEEK) as well as nanocomposite composition (CNT/Pt) on the chemical oxygen demand (COD) removal and power generation were discussed. The nanocomposite was analyzed using XRD, SEM, and TEM. Moreover, the degree of sulfonation (DS) was measured by NMR. A quadratic model was utilized to forecast the removal of COD and power generation under distinct circumstances. To obtain the maximum COD removal along with maximum power generation, favorable conditions were achieved by statistical and mathematical techniques. The findings proved that MFC could remove 92% of COD and generate 545mW/m2 of power density at optimum conditions of DS=80; and CNT/Pt of 14 wt% CNT- 86 wt% Pt.
Seyed Taghi Mohammadi,Mehdi Nazirzadeh,Hassan Nanakar 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.1
In the present investigation, A series of Mg-Mn ferrite nanopowders with composition MgxMn1-xFe2O4 (with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the co-precipitation method. Thereafter, the obtained powders were pressed separately to form pellets, and sintered at 1250 ℃ for 3 h at air atmosphere. Finally, the samples were characterized by X-ray Diffraction (XRD) technique, Scanning Transmission Electron Microscopy (STEM), Alternating Gradient Force Magnetometer (AGFM) and Curie temperature measuring instrument. The lattice constant and distribution of cation in the tetrahedral and octahedral sites have been deduced through XRD data analysis. The XRD pattern confirmed the existence of single phase of cubic spinel crystal structure with the lattice parameter ranging from 8.49 Å (for MnFe2O4) to 8.35 Å (for MgFe2O4). This behavior was attributed to the ionic radii. STEM micrographs exhibit that the particles are spherically shaped and agglomerated with particle size ranging 50–90 nm quite consistent with particle size obtained from XRD data. The average crystallite size was 70nm. Magnetization decreases with increasing Mg concentration except for x = 0.2, where it shows increasing trend. Curie temperature measurements exhibit increasing trend with increase in magnesium content. The variation of the saturation magnetization and Curie temperature with increasing concentration of the Mg2+ ions can be explained on the basis of cation distribution, strengthening A–B interaction and Neel's two sub-lattice.
Hamed Najaran,Hassan Hassani Bafrani,Hamid Rashtbari,Fatemeh Izadpanah,Mohammad Reza Rajabi,Hamed Haddad Kashani,Abouzar Mohammadi 경희대학교 융합한의과학연구소 2019 Oriental Pharmacy and Experimental Medicine Vol.19 No.2
Current study was aimed to investigate the protective effect of berberine (BB) on the serum gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), inhibin B (INHB), testosterone (T) and alkaline phosphatase (Alk-p) activity in the testis of experimental varicocele-induced animals. For the current objective, 30 mature-male Wistar rats were randomly divided into control (n = 6 rats), control-sham (n = 6 rats) and experimental groups (n = 18 rats). The animals in the experimental groups were undergone experimental varicocele and simple laparotomy was conducted in control-sham group. 60 days after varicocele (VCL) induction the experimental group subdivided into: nontreated VCL-induced and 50 mg/kg and 100 mg/kg BB-treated groups (intra-peritoneally). Following 60 days, the animals were euthanized and serum levels of testosterone and testicular activity of alkaline phosphatase were measured. Non-treated VCL-induced animals indicated a significant (P < 0.05) reduction in serum levels of T and INHB and a remarkable (P < 0.05) increase in GnRH, FSH, LH and Alk-p activity compared to control and control-sham groups. Insignificant changes were found between control and control-sham groups. Meanwhile, each BB administered group showed a remarkable (P < 0.05) increase in serum levels of T and INHB and a significant (P < 0.05) decrease in GnRH, FSH, LH and alkaline phosphatase activity in testis tissue. According to the current findings, BB by increasing serum levels of testosterone and INHB increases the testicular endocrine capacity and protects Leydig cell against inflammatory and oxidant injury of varicocele. In addition, BB by inhibiting GnRH, FSH, LH and alkaline phosphatase activity, regulate
Lumbar Spinal Canal Stenosis Classification Criteria: A New Tool
Parisa Azimi,Hassan Reza Mohammadi,Edward C. Benzel,Sohrab Shahzadi,Shirzad Azhari 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.3
Study Design: Case-control study. Purpose: To design a new tool for classifying lumbar spinal canal stenosis (CLSCS). Overview of Literature: Grading of patients with lumbar spinal canal stenosis (LSCS) is controversial. Methods: The Oswestry disability index (ODI) and the neurogenic claudication outcome score (NCOS) were recorded. Four parameters, which indicate the severity of LSCS disease, including Hufschmidt-grade, grading of magnetic resonance imaging, self-paced walking test, and stenosis ratio (SR) were employed. For the SR, quartile analysis was applied for classifying LSCS and the Hufschmidt- grade was modified into a 4-grade score. An initial score was assigned to each metric based on the severity of LSCS. Using the inverse-variance weighting method, the relative weights of these domains and their categories were determined. The score for all of the cases was obtained based on their weight by summing up the points of the four variables. Quartile analysis was used and a CLSCS score was proposed. Finally, intra- and interobserver reliability, and validity were assessed. Results: A total of 357 patients were studied. The final CLSCS score for each case ranged from 4 to 16.5. Based on the quartile analysis, using the new criteria set, the CLSCS score was divided into four categories: CLSCS<7 (grade 0); 7≤CLSCS<10 (grade 1); 10≤CLSCS<13 (grade 2); and 13≤CLSCS≤16.5 (grade 3). The kappa values of for the CLSCS score indicated a perfect agreement. The CLSCS was correlated with the ODI and NCOS. All patients with grade 3 CLSCS were observed in the surgical group. Conclusions: The CLSCS score can be helpful for classifying LSCS patients and in the decision-making process.
Development of cellulosic‑based hemostatic dressing with antibacterial activity
Mostafa Goodarz,Amir Behzadnia,Hassan Mohammadi 한국의류학회 2022 Fashion and Textiles Vol.9 No.1
A cotton-based hemostatic dressing featuring antibacterial properties was developed with the potential of being used in trafc accidents to control hemorrhage. Cotton gauze was oxidized initially in an acidic medium and then coated by PVA nanofbers and/or PVA nanofbers loaded with Ciprofoxacin. Fabricated dressings were characterized by FTIR analysis and SEM images. The FTIR spectrum showed the existence of carboxyl groups on the oxidized cotton gauze’s surface. The carboxyl groups content was estimated to be 17.3±0.3 for the oxidized sample with a mixture of nitric acid and phosphoric acid for 24 h (OCF-Mixed acid24). Moreover, the efect of the exposure duration of cotton gauze in the acidic medium on the blood coagulation activity was assessed. It was observed that the OCF-Mixed acid24 sample exhibited an agreeable hemostatic activity (BCIs=10). The antibacterial activity against E. coli and S. aureus bacteria was also captured for the coated cotton gauze by the PVA nanofbers loaded with Ciprofoxacin.