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Search Results: 1 - 10 of 718796 matches for " Ibrahim A.M. Abdel-Halim "
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Modeling and Simulation of a Matrix Converter/Inductive Load System
Ibrahim A.M. Abdel-Halim,Hamed G. Hamed,Ahmed M. Hassan
International Journal of Electrical and Power Engineering , 2012, DOI: 10.3923/ijepe.2011.144.149
Abstract: In this study, a system composed of a matrix converter and an inductive load is modeled and simulated using Matlab/Simulink software package. The modulation techniques used for the matrix converter are Venturini and Optimum venturini methods. The voltages and currents waveforms of the system are presented and compared to those obtained from previously published results to validate the simulation process.
Steady-State Performance of a Directly Connected PV Array/Six-Step VSI/Induction Motor System
Ibrahim A.M. Abdel-Halim,Hamed G. Hamed,Ahmed M. Hassan
International Journal of Electrical and Power Engineering , 2012, DOI: 10.3923/ijepe.2010.105.112
Abstract: In this study, the analysis of a PV array connected directly without an intermediate converter to a voltage-source inverter/induction motor system driving a centrifugal pump is presented. This method is based on that the VSI/induction motor system, operating at a constant air gap flux can be connected directly to the PV array by controlling the insolation level to which the PV array is subjected.
Modeling and Simulation of a Self-Excited Induction Generator/Inductive Load System
Ibrahim A.M. Abdel-Halim,Hamed G. Hamed,Ahmed M. Hassan
International Journal of Electrical and Power Engineering , 2012, DOI: 10.3923/ijepe.2011.92.101
Abstract: In this study, complete Matlab/Simulink block diagrams are constructed to obtain the steady-state performance of a self-excited induction generator, using loop impedance method, using the exact and a previously obtained simplified method to obtain the operating frequency of the generator when feeding inductive loads. The results obtained by the presented approach for the frequency and performance characteristics of the system are compared with results obtained from a published reference to prove the validity of the simulation process.
Modeling and Simulation of a Matrix Converter/Induction Motor System
Ibrahim A.M. Abdel-Halim,Hamed G. Hamed,Mohammed E. Elfaraskoury,Ahmed M. Hassan
International Journal of Electrical and Power Engineering , 2012, DOI: 10.3923/ijepe.2011.193.202
Abstract: In this study, a system composed of a matrix converter and an induction motor is modeled and simulated using Matlab/Simulink software package. The modulation techniques used for the matrix converter are Venturini and Optimum Venturini Methods. The variation of motor voltages, currents, torque and speed with time are presented and compared with those obtained from previously published results to validate the simulation process.
Synthesis, chemical reactivity and fungicidal activity of pyrido[1,2-b][1,2,4]triazine derivatives
Ibrahim, Magdy A.;Abdel-Rahman, Reda M.;Abdel-Halim, Ali M.;Ibrahim, Salah S.;Allimony, Hassan A.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000700012
Abstract: the synthesis of some new pyrido[1,2-b][1,2,4]triazines (2-12) was achieved by cyclocondensation of 4-aryl-1,6-diamino-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles (1a, b) with α,β-bifunctional compounds. pyrido[1,2:2′,3′]triazino[5′,6′-f]triazines (13-14) were also prepared. the behavior of 1a, b toward interactions with indole-2,3-dione and its n-acetyl analogue have been studied under different reaction conditions. the structures of the new products have been deduced from elemental analysis and spectral data (uv, ir, 1h nmr, 13c nmr and mass spectra). the new synthesized compounds were screened for their antifungal activities.
Assessment of Physicians’ Knowledge, Attitude and Practices of Radiation Safety at Suez Canal University Hospital, Egypt  [PDF]
Rasha F. Abdellah, Shaimaa A. Attia, Ahmed M. Fouad, Amani W. Abdel-Halim
Open Journal of Radiology (OJRad) , 2015, DOI: 10.4236/ojrad.2015.54034
Abstract: Doctors who request imaging must be well trained in deciding whether diagnostic imaging is indicated and have an accurate knowledge of the associated risks. Although radiological doses are low and the chance of late effect is minimal, it should be kept as low as reasonably achievable. This cannot be achieved without a proper knowledge and adherence to safe practices. This cross-sectional study investigates the level of physicians’ knowledge about radiation safety and their attitude towards radiation protection. A self-administered questionnaire, for radiation safety was sent to a purposive sample of 120 physicians at Suez Canal University Hospital. Eighty questionnaires were filled by participants (response rate; 66.7%). The sample included 22 radiologists, 15 oncologists, 25 surgeons and 18 orthopedists. Most participants did not receive any radiation safety-related training (88.8%). Radiologists and oncologists were exposed to ionizing radiation more frequently; however, their knowledge was as low as that of other physicians. The overall knowledge score ranged from 40% - 60% (mean; 56.5 ± 15.2), with a low score among surgeons and orthopedics. The most deficient knowledge was in the dose of background radiation and the radiation dose received by patients in each type of radiation procedure. Adherence to safe radiation practices was violated by most of participants, especially surgeons and orthopedics, but they attributed it to the poor applicability of the protective measures during performing the procedures. This study concluded that physicians at the Suez Canal University Hospital had deficient knowledge, unsafe practices and negative attitude towards radiation safety policies & precautions.
Investigation of Self Excited Torsional Vibrations of Different Configurations of Automatic Transmission Systems during Engagement  [PDF]
Eid O. A. Abd Elmaksoud, E M. Rabeih, N A Abdel-halim, S M. El Demerdash
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.312146
Abstract: The vehicle drive line system is subjected to torsional vibration from different sources of the system such as; engine fluctuating torque, Hook’s joint and the final drive. However, the essential source is the friction torque induced in the friction elements, during their engagement. In the automatic transmission system, the planetary gear set includes several friction elements such as; clutch, band brakes, and one way clutch. During the engagement, severe torsional vibration is induced by friction which is noticeable by the passengers in the form of what so called vehicle shunt. In present paper, a torsional vibration model for Drive Line (DL) system includes three different configurations of automatic transmission is constructed. A computer program using MATLAB subroutines is implemented to obtain the system response. Effect of system parameters on the dynamic behavior and stability has been investigated. The system damping and the trend of the friction coefficient have an essential effect on the dynamic behavior and stability of the system. The system response is now predictable with change of the system parameters which opens up the opportunity in future to control the vibration level.
Study of Stress Sources and Critical Stress Combinations for the Input Shaft of a Longitudinally Mounted Four Speed Automotive Automatic Transmission Model  [PDF]
N. A. Abdel-Halim
Modern Mechanical Engineering (MME) , 2013, DOI: 10.4236/mme.2013.31006
Abstract:

In the present paper; two models of the input shaft for a Longitudinal Mounted four Speed Automotive Automatic Transmission for the first time were introduced to describe the input shaft critical loads. In the first model; the DC (Direct Clutch) connects two gears together. This gives no change in the set torque (the set output torque equal to the set input torque). In the second model; the ODB (Over Drive Brake) fixes one element of the planetary set. This is resulting, the gear set gives reduction ratio (the set output torque is not equal to the set input torque). So, the transmission input shaft is worked under two different working operating conditions of torque. Also, it is loaded by a two vertical loads which are coming from the turbine and planetary set loads respectively. They are shown that there are three critical combinations of forces (contact force, shear force, and normal force) applied on the input shaft. The critical forces can be possibility exist three types of cracks for the input shaft cross section they are: transverse (torsion stress), longitudinal (bending stress), and vertical (shear stress). The three cracks are studied in this article. The article considers three stress factors: shearing torsion stress, shear stress, and bending stress.

Phytoplankton and environmental variables as a water quality indicator for the beaches at Matrouh, south-eastern Mediterranean Sea, Egypt: an assessment
Samiha M. Gharib,Zeinab M. El-Sherif,Ahmed M. Abdel-Halim,Ahmed A. Radwan
Oceanologia , 2011,
Abstract: This study was carried out to determine the water quality of the beaches at Matrouh, south-eastern Mediterranean Sea, Egypt, by studying environmental variables as well as phytoplankton abundance and community structure. Surface water samples were monitored from a series of beach sites over a period of five seasons during 2009-2010. A total of 203 phytoplankton species were identified from seven algal divisions. Seasonal differences in the quantitative and qualitative composition of the phytoplankton communities in the different sites were marked. Nutrient concentrations and phytoplankton abundances were found to be poorer than those of many other areas along Egyptian coast. The Shannon-Wiener Diversity Index classified Matrouh water as being between clean and moderately polluted, whereas the WQI demonstrated that it was between good and excellent. It can be concluded that the index based on WQI is currently more suitable than the phytoplankton species index for assessing the quality of the water of the Matrouh beaches.
Synthesis, Molecular Modeling, and Biological Evaluation of Novel Tetrahydro-β-Carboline Hydantoin and Tetrahydro-β-Carboline Thiohydantoin Derivatives as Phosphodiesterase 5 Inhibitors
Ashraf H. Abadi,Jochen Lehmann,Gary A. Piazza,Mohammad Abdel-Halim,Mohamed S. M. Ali
International Journal of Medicinal Chemistry , 2011, DOI: 10.1155/2011/562421
Abstract: Two series of fused tetrahydro-β-carboline hydantoin and tetrahydro-β-carboline thiohydantoin derivatives with a pendant 2,4-dimethoxyphenyl at position 5 were synthesized, and chiral carbons at positions 5 and 11a swing from R,R to R,S, S,R, and S,S. The prepared analogues were evaluated for their capacity to inhibit phosphodiesterase 5 (PDE5) isozyme. The R absolute configuration of C-5 in the β-carboline hydantoin derivatives was found to be essential for the PDE5 inhibition. Chiral carbon derived from amino acid even if of the S configuration (L-tryptophan) may lead to equiactive or more active isomers than those derived from amino acid with the R configuration (D-tryptophan). This expands the horizon from which efficient PDE5 inhibitors can be derived and may offer an economic advantage. The thiohydantoin derivatives were less active than their hydantoin congeners. 1. Introduction Cyclic nucleotide phosphodiesterases (PDEs) are a superfamily of enzymes responsible for the hydrolysis of cyclic adenosine 3′,5′-monophosphate (cAMP) and cyclic guanosine 3′,5′-monophosphate (cGMP) that are important intracellular second messengers playing a central role in regulating many relevant cell functions. These second messengers are converted to the biologically inactive monophosphates with subsequent termination of their physiological functions. Currently, the PDE system includes 11 families (PDE1-PDE11) comprising 21 different gene products [1–3]. The cGMP-specific phosphodiesterase 5 (PDE5) is abundant in the penile tissue, platelets, vascular, and smooth muscle tissues. This enzyme is the primary target for the development of small molecules, such as the well-known sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) to treat erectile dysfunction [4]. Nitric oxide activates guanylatecyclase to convert GTP to the second messenger cGMP which, in turn, results in smooth muscle relaxation and the erectile response. cGMP is hydrolysed by PDE5 to inactive GMP. PDE5 inhibitors such as sildenafil thus act to inhibit cGMP breakdown and thereby facilitate penile erection in patients suffering from MED [5]. Recently, sildenafil was approved for the treatment of pulmonary hypertension (Revatio), and there are numerous emerging reports relating the elevation of cGMP to anticancer apoptotic actions. This further illustrates the potential of PDE5 inhibitors as therapeutic agents. Chemically speaking, the long-acting PDE5 inhibitor tadalafil is considered as a fused tetrahydro-β-carboline piperazinedione derivative with pendant 1,3-benzodioxol moiety at
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