PWM Control Techniques for Single-Phase Multilevel Inverter Based Controlled DC Cells

Sayed, Mahmoud A.,Ahmed, Mahrous,Elsheikh, Maha G.,Orabi, Mohamed The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103.

PWM Control Techniques for Single-Phase Multilevel Inverter Based Controlled DC Cells

Mahmoud A. Sayed,Mahrous Ahmed,Maha G. Elsheikh,Mohamed Orabi 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103.

Experimental Investigation of a Walk-in Refrigerator Performance Using R290 as a Retrofit for R22

A. R. El-Sayed,M. El Morsi,N. A. Mahmoud 대한설비공학회 2018 International Journal Of Air-Conditioning and Refr Vol.26 No.4

An experimental performance study is performed on a refrigeration system equipped with a scroll compressor and tested with R22 using an electronic expansion valve (EEV) as an expansion device and controlled by proportional-integral-derivative (PID) control method. The system is tested at −12∘C, −8∘C, −4∘C, 0∘C and 4∘C evaporator air temperature and 20∘C, 25∘C and 30∘C condenser inlet water temperature at 50 Hz compressor driving frequency and 50Hz evaporator fans driving frequency. R22 reached the set point at all temperatures except −12∘C evaporator temperature with 30∘C condenser temperature due to the severe increase in the compressor discharge temperature that could result in the lubricating oil burnout. Then, the system is retrofitted with a reciprocating compressor especially designed to be used with R290 and tested with R290 at the same evaporator and condenser temperatures using EEV as an expansion device. R290 reached all set points at all evaporator and condenser temperatures. Also, R290 was able to reach all evaporator temperatures at higher condenser temperatures, 35∘C and 40∘C, and this will be discussed in future work. The results show that using R290, the pulldown time decreases by 30.3–71.4%, the ON time ratio decreases by 1–23.6%, the compressor discharge temperature decreases by 46.6–81∘C, the refrigerant mass flow rate decreases by 28.8–50.4%, VRC decreases by 15.2–32.5%, the compressor power consumption decreases by 34.4–44.3% and coefficient of performance (COP) increases by 35–115.5%.

Nanosheet composed of gold nanoparticle/graphene/epoxy resin based on ultrasonic fabrication for flexible dopamine biosensor using surface-enhanced Raman spectroscopy

Hussein Mahmoud A.,El-Said Waleed A.,Abu-Zied Bahaa M.,최정우 나노기술연구협의회 2020 Nano Convergence Vol.7 No.15

Construction of a fast, easy and sensitive neurotransmitters-based sensor could provide a promising way for the diagnosis of neurological diseases, leading to the discovery of more effective treatment methods. The current work is directed to develop for the first time a flexible Surface-Enhanced Raman Spectroscopy (SERS) based neurotransmit‑ ters sensor by using the ultrasonic-assisted fabrication of a new set of epoxy resin (EPR) nanocomposites based on graphene nanosheets (GNS) using the casting technique. The perspicuous epoxy resin was reinforced by the variable loading of GNS giving the general formula GNS/EPR 1–5 . The designed products have been fabricated in situ while the perspicuous epoxy resin was formed. The expected nanocomposites have been fabricated using 3%, 5%, 10%, 15% and 20% GNS loading was applied for such fabrication process. The chemical, physical and morphological properties of the prepared nanocomposites were investigated by using Fourier transforms infrared spectroscopy, X-ray diffrac‑ tion, Thermogravimetric analysis, Differential Thermal gravimetry, and field emission scanning electron microscopy methods. The GNS/EPR 1–5 nanocomposites were decorated with a layer of gold nanoparticles (Au NPs/GNS/EPR) to create surface-enhanced Raman scattering hot points. The wettability of the Au NPs/GNS/EPR was investigated in comparison with the different nanocomposites and the bare epoxy. Au NPs/GNS/EPR was used as a SERS-active surface for detecting different concentrations of dopamine with a limit of detection of 3.3 µM. Our sensor showed the capability to detect low concentrations of dopamine either in a buffer system or in human serum as a real sample.

Synthesis, structural, TD-DFT, and optical characteristics of indole derivatives

Almutlaq N.,Elshanawany Mahmoud M.,Sayed Mostafa,Younis Osama,Ahmed Mostafa,Wachtveitl Josef,Braun Markus,Tolba Mahmoud S.,Al-Hossainy Ahmed F.,Abozeed Amina A. 한국물리학회 2023 Current Applied Physics Vol.45 No.-

New compounds of (E)-1-(3-chloro-1H-indol-2-yl)-N-(4-methoxyphenyl)methanimine [Indol-M] and (E)-1-(4- (((3-chloro-1H-indol-2-yl)methylene)amino)phenyl)ethan-1-one [Indol-A] were synthesized and subsequently converted to thin films via physical vapor deposition technique. Numerous characterization techniques were used including FTIR, nuclear magnetic resonance, X-ray diffraction, scanning electron microscope, and optical spectroscopy. Additionally, the optimization using TD-DFTD/Mol3 and Cambridge Serial Total Energy Bundle (TD-FDT/CASTEP) was performed. The XRD and FTIR spectra recorded experimentally were confirmed by TD-DFT calculations, proving their molecular structure. As determined by XRD, the crystallite size of [Indol-M]TF and [Indol-A]TF is 72.26 and 62.05 nm, respectively. SEM image depicts a one-dimensional morphological structure made up of tightly packed nanorods. The direct optical energy bandgaps computed using Tauc’s equation for the [Indol-M]TF and [Indol-A]TF are 4.49 eV and 3.31 eV, respectively. As predicted by CASTEP TD-DFT, the optical properties agree well with the experimental values. [Indol-M]TF and [Indol-A]TF present good candidates for optoelectronics and solar cell applications.

Arctigenin from Burdock Root Exhibits Potent Antibacterial and Anti-Virulence Properties against Pseudomonas aeruginosa

Koshak Abdulrahman E.,Elfaky Mahmoud A.,Abdallah Hossam M.,Albadawi Dina A. I.,Mohamed Gamal A.,Ibrahim Sabrin R. M.,Alzain Abdulrahim A.,Khafagy El-Sayed,Rajab Azza A. H.,Hegazy Wael A. H. 한국미생물·생명공학회 2024 Journal of microbiology and biotechnology Vol.34 No.8

Arctium lappa (Burdock) root is used in various culinary applications especially in Asian Cuisine. Arctigenin (ARC) is a polyphenolic compound abundant in the roots of the burdock plant from which it derives its name. The emergence of bacterial resistance is a growing global worry, specifically due to the declining availability of new antibiotics. Screening for the antibacterial candidates among the safe natural products is a promising approach. The present study was aimed to assess the antibacterial activity of ARC against Pseudomonas aeruginosa exploring its effect on the bacterial cell membrane. Furthermore, the anti-virulence activities and anti-quorum sensing (QS) activities of ARC were in vitro, in vivo and in silico assessed against P. aeruginosa. The current results showed the ARC antibacterial activity was owed to its disruption effect of the cell membrane. ARC at sub-MIC significantly decreased the formation of biofilm, motility, production of extracellular enzymes and in vivo protected mice against P. aeruginosa. These anti-virulence activities of ARC are owed to its interference with bacterial QS and its expression. Furthermore, ARC showed mild effect on mammalian erythrocytes, low probability to induce resistance and synergistically combined with antibiotics. In summary, the promising anti-virulence properties of ARC indicate its potential as an effective supplement to conventional antibiotics for treating severe P. aeruginosa infections.

A Review of the Potential Replacements of HCFC,HFCs Using Environment-Friendly Refrigerants

A. R. El-Sayed,M. El Morsi,N. A. Mahmoud 대한설비공학회 2018 International Journal Of Air-Conditioning and Refr Vol.26 No.3

The adequate and efficient performance of HVAC systems are signs of luxury and human comfort, and the improvement of their performance has been the target of continuous researches. Choosing the suitable refrigerant is the main parameter in matching the system components, selecting the type of heat exchangers, the compressor, the expansion device and the suitable lubricant. The theoretically ideal refrigerant is the one having zero ozone depletion potential (ODP), low global warming potential (GWP), nontoxic, nonflammable, has appropriate thermodynamic and heat transfer properties and is compatible with any type of lubricating oil. Chlorinated, fluorinated refrigerants, zeotropic and azeotropic mixtures satisfy many requirements, but have high ODP and GWP and are not compatible with all types of oil. Hydrocarbons (HCs) satisfy all the requirements except being highly flammable. This work reviews previous research aiming to find substitutes for the environmentally harmful refrigerants by other environmentally friendly ones and compare their performance in various HVAC appliances.

Cap-Assisted Technique versus Conventional Methods for Esophageal Food Bolus Extraction: A Comparative Study

Mahmoud Wahba,Ghada Habib,Ahmed El Mazny,May Fawzi,Mohamed A. Elfeki,Seham Sabry,Mahommad ELbaz,Sayed M Seif El Nasr 대한소화기내시경학회 2019 Clinical Endoscopy Vol.52 No.5

Background/Aims: Food bolus impaction is the most common form of esophageal foreign body impaction observed in adults. Clinicalguidelines recommend using the push technique or retrieval methods in such cases. The push technique can cause injuries in certainclinical situations. Notably, conventional retrieval methods are time and effort consuming. Cap-assisted endoscopic extraction of animpacted food bolus is an easy and effective technique; however, more data are needed for its validation. This study compared the capassistedextraction technique with conventional methods. Methods: This prospective observational multicenter study compared the success and en bloc removal rates, total procedure time, andadverse events in both techniques.. Results: The study included 303 patients who underwent food bolus extraction. The push technique was used in 87 patients (28.7%) anda retrieval procedure in 216 patients (71.3%). Cap-assisted extraction was performed in 106 patients and retrieval using conventionalmethods in 110 patients. The cap-assisted technique was associated with a higher rate of en bloc removal (80.2% vs. 15%, p<0.01), shorterprocedure time (6.9±3.5 min vs. 15.7±4.1 min, p<0.001), and fewer adverse events (0/106 vs. 9/110, p<0.001). Conclusions: Cap-assisted extraction showed no adverse events, higher efficacy, and a shorter procedure time compared withconventional retrieval procedures.

Antimicrobial Activity of New 4,6-Disubstituted Pyrimidine, Pyrazoline, and Pyran Derivatives

Mahmoud M. M. Ramiz,Wael A. El-Sayed,Asmaa I. El-Tantawy,Adel A. H. Abdel-Rahman 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.5

A number of new 2,6-didisubstituted pyrimidine, pyrazoline, and pyran derivatives were synthesized starting from their chalcone derivative. The synthesized compounds displayed different degrees of antimicrobial activity against Bscillus subtilis (Gram-positive), Pseudomonas aeruginosa (Gram-negative), and Streptomyces species (Actinomycetes).

Enhancement and optimization of gamma radiation shielding by doped nano HgO into nanoscale bentonite

Elhassan A. Allam,Rehab M. El-Sharkawy,Atef El-Taher,E.R. Shaaban,RedaElsaman,E. El Sayed Massoud,Mohamed E. Mahmoud 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6

In this study, nano-scaled shielding materials were assembled and fabricated by doping different weightpercentages of Nano-mercuric oxide (N-HgO) into Nano-Bentonite (N-Bent) based on using (100-x% NBent þ x% N-HgO, x ¼ 10, 20, 30, and 40 wt %). The fabricated N-HgO/N-Bent nanocomposites werecharacterized by FT-IR, XRD, and SEM and evaluated to evaluate their shielding properties toward gammaradiation by using four different g-ray energies form three point sources; 356 keV from 133Ba, 662 keVfrom 137Cs as well as 1173, and 1332 keV from 60Co. The g-rays mass attenuation coefficients were plottedas a function of the doped N-HgO concentrations into N-HgO/N-Bent nanocomposites. The computedvalues of mass attenuation coefficients (mm), effective atomic number (Zeff) and electron density (Nel) bythe as-prepared samples were found to increase, while the half value layer (HVL) and mean free path(MFP) were identified to decrease upon increasing the N-HgO contents. It was concluded also that theincrease in N-HgO concentration led to a direct increase in the mass attenuation coefficient from 0.10 to0.17 cm2/g at 356 keV and from 0.08 to 0.09 cm2/g at 662 keV. However, a slight increase was observed inthe identified mass attenuation coefficients at (1172 and 1332 keV).