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Nonlinear Representation of Two-Stage Power-Factor-Correction AC/DC Circuits
Orabi Mohamed,Ninomiya Tamotsu The Korean Institute of Power Electronics 2004 JOURNAL OF POWER ELECTRONICS Vol.4 No.4
Two-stage Power-Factor-Correction (PFC) converters are the most common circuits for drawing sinusoidal and in phase current waveforms from an ac source with a good regulated output voltage. The first stage is a boost PFC converter with average-current-mode control for achieving the near-unity power factor and the second stage is a forward converter with voltage-mode control to regulate the output voltage. Stability analysis and design methods of two-stage PFC converters have previously been discussed using linear models. Recently, new nonlinear phenomena have been detected in pre-regulator boost PFC circuits and a new nonlinear model has been proposed for pre-regulated PFC converters. Therefore, investigation of two-stage PFC converters from the nonlinear viewpoint becomes important because the second stage DC/DC converter adds more complexity to the circuit. So, this paper introduces a study of the stability of two-stage PFC converters. A novel nonlinear model of two-stage PFC converters is proposed. Then, a stability analysis is made based upon this nonlinear model. The high correspondence between the simulated and experimental results confirms our analysis.
Orabi M. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.5
The influence of adding iodine as a contrast substance to elevate radiation in a tumor is studied using simulation techniques of Monte-Carlo. The study is carried on a brain cancer by adopting an unsophisticated head phantom. The ionizing radiation source is an external beam of x-rays with energy range of a few tens of keV. The expected radiation dose increment due to adding the iodine is investigated by comparing the radiation in the tumor after and before adding the iodine and calculating the ratio between the two doses. Several concentrations of the contrast substance are used to quantify its impact. The change of the dose increment with the source energy is also examined. It is found that the radiation elevation in the tumor tends to saturate with increasing the iodine concentration, and for the studied domain of energies (30 keVe100 keV), the radiation dose enhancement factors (RDEF) for the different iodine concentrations (1%e9%) show peaked curves, with the peak occurring between 60 keV and 70 keV. For the highest concentration studied, 9%, the peak value is almost 7
Step-One in Pre-regulator Boost Power-Factor-Correction Converter Design
Orabi, Mohamed,Ninomiya, Tamotsu The Korean Institute of Power Electronics 2004 JOURNAL OF POWER ELECTRONICS Vol.4 No.1
The output storage capacitor of the PFC converters is commonly designed for the selected hold-up time or the allowed output ripple voltage percentage. Nevertheless, this output capacitor is a main contribution factor to the PFC system stability. Moreover, seeking for a minimum output storage capacitor that assures the PFC desired operation under all condition, and providing the advantage of a small size and low cost is the main interesting target for engineering. Therefore, in this issue the design steps of the PFC converter have been discussed depending on three choices, output ripple, hold-up time, and stability. It is cleared that any design must take the minimum required storage capacitor for stability prospective as step-l in deign, then apply for any other specification like hold-up time or ripple percentage.
Step-One in Pre-regulator Boost Power-Factor-Correction Converter Design
Mohamed Orabi,Tamotsu Ninomiya 전력전자학회 2004 JOURNAL OF POWER ELECTRONICS Vol.4 No.1
The output storage capacitor of the PFC converters is commonly designed for the selected hold-up time or the allowed output ripple voltage percentage Nevertheless, this output capacitor is a main contribution factor to the PFC system stability. Moreover, seeking for a minimum output storage capacitor that assures the PFC desired operation under all condition, and providing the advantage of a small size and low cost is the main interesting target for engineering Therefore, in this issue the design steps of the PFC converter have been discussed depending on three choices, output ripple, hold-up time, and stability It is cleared that any design must take the minimum required storage capacitor for stability prospective as step-1 in deign, then apply for any other specification like hold-up time or ripple percentage
Nonlinear Representation of Two-Stage Power-Factor-Correction AC/DC Circuits
Mohamed Orabi,Tamotsu Ninomiya 전력전자학회 2004 JOURNAL OF POWER ELECTRONICS Vol.4 No.4
Two-stage Power-Factor-Correction (PFC) converters are the most common circuits for drawing sinusoidal and in phase current wave forms from an ac source with a good regulated output voltage. The first stage is a boost PFC converter with average-current-mode control for achieving the near-unity power factor and the second stage is a forward converter with voltage-mode control to regulate the output voltage. Stability analysis and design methods of two-stage PFC converters have previously been discussed using linear models. Recently, new nonlinear phenomena have been detected in pre-regulator boost PFC circuits and a new nonlinear model has been proposed for pre-regulated PFC converters. Therefore, investigation of two-stage PFC converters from the nonlinear viewpoint becomes important because the second stage DC/DC converter adds more complexity to the circuit. So, this paper introduces a study of the stability of two-stage PFC converters. A novel nonlinear model of two-stage PFC converters is proposed. Then, a stability analysis is made based upon this nonlinear model. The high correspondence between the simulated and experimental results confirms our analysis.<br/>
A NOTE ON CERTAIN TRANSFORMATION FORMULAS RELATED TO APPELL, HORN AND KAMPÉ DE FÉRIET FUNCTIONS
Asmaa Orabi Mohammed,Medhat Ahmed Rakha,Arjun K. Rathie Korean Mathematical Society 2023 대한수학회논문집 Vol.38 No.3
In 2019, Mathur and Solanki [7, 8] obtained a few transformation formulas for Appell, Horn and the Kampé de Fériet functions. Unfortunately, some of the results are well-known and very old results in literature while others are erroneous. Thus the aim of this note is to provide the results in corrected forms and some of the results have been written in more compact form.
Marwan Mohamed Abu ORABI 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.2
The goal of the study was to see how polymer banknotes affected users’ purchasing intention. Variables affecting the properties of polymer banknotes were considered, including security, ease of use, convenience, and durability. To achieve the study’s main goal, quantitative methods were used, and a questionnaire was created and posted online through Google Forms to collect primary data. The questionnaire was completed by 403 people, and the data was screened and analyzed using SPSS.The study found that using Polymer money influenced people’s behavior, particularly in terms of purchase patterns, decisions, and impulsive behavior toward purchases. This was attributed to the security and simplicity of using Polymer money, which appealed to many people. Furthermore, the study found that people lost their feeling of spending, meaning that using polymer money didn’t feel like spending to them, effectively eliminating the moral guilt associated with excessive spending and encouraging more impulsive buying decisions.Based on the findings, the study recommends that a study be conducted to compare the use of Polymer money with tiny and large banknotes to see what kind of difference there is.
Ultralow Lattice Thermal Conductivity and Enhanced Thermoelectric Performance in SnTe:Ga Materials
Al Rahal Al Orabi, Rabih,Hwang, Junphil,Lin, Chan-Chieh,Gautier, Ré,gis,Fontaine, Bruno,Kim, Woochul,Rhyee, Jong-Soo,Wee, Daehyun,Fornari, Marco American Chemical Society 2017 Chemistry of materials Vol.29 No.2
<P>Ultralow thermal conductivity is of great interest in a variety of fields, including thermoelectric energy conversion. We report, for the first time, experimental evidence that Ga-doping in SnTe may lower the lattice thermal conduction slightly below the theoretical amorphous minimum at high temperature. Such an effect is justified by the spontaneous formation of nanoprecipitates we characterized as GaTe. Remarkably, the introduction of Ga (2-10%) in SnTe also improves the electronic transport properties by activating several hole pockets in the multivalley valence band. Experimental results are supported by density functional theory calculations. The thermoelectric figure of merit, ZT, reaches similar to 1 at 873 K in Sn0.96Ga0.07Te, which corresponds to an similar to 80% improvement with respect to pure SnTe.</P>
Speed of random walk and resistance
Konsowa, Mokhtar,Oraby, Tamer 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
We give a simple formula to calculate the speed of weighted random walks on nonnegative integers and on spherically symmetric trees.
Speed of random walk and resistance
Mokhtar Konsowa,Tamer Oraby 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
We give a simple formula to calculate the speed of weighted random walks on nonnegative integers and on spherically symmetric trees.