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Sayed Ahmed E. Sayed Ahmed,Osama M. Mesalhy,Mohamed A. Abdelatief 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6
A numerical study is conducted to clarify heat transfer characteristics, effectiveness and entropy generation for a bundle of wingshaped-tubes attached to Longitudinal fins (LF) at downstream side. The air-side Re a ranged from 1.8 x 10 3 to 9.7 x 10 3 . The fin height (h f ) and fin thickness (δ) have been changed as: (2 mm ≤ h f ≤ 12 mm) and (1.5 mm ≤ δ ≤ 3.5 mm). The analysis of entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction losses. The temperature field around the wing-shaped-tubes with (LF) is predicted using commercial CFD FLUENT 6.3.26 software package. Correlations of Nu a , St a , and Bejan number (Be), as well as the irreversibility distribution ratio (Φ) in terms of Re a and design parameters for the studied bundle are presented. Results indicated that, installing fins with heights from 2 to 12 mm results in an increase in Nu a from 11 to 36% comparing with that of wing-shaped tubes without fins (NOF). The highest and lowest values of effectiveness (ε) at every value of the considered Re a range are occurred at h f = 6 mm and (NOF), respectively. The wing-shaped-tubes heat exchanger with h f = 6 mm has the highest values of (ε), efficiency index (η) and area goodness factor (G a ) and also the lowest values of Φ and hence the best performance comparing with other arrangements. The minimum values of Φ are occurred at h f = 6 mm. (Be) decreases with increasing Re a for all studied h f . The heat transfer irreversibility predominates for (1800 ≤ Re a ≤ 4200) while the opposite is true for (6950 < Re a ≤ 9700). δ has negligible effect on Nu a and heat transfer irreversibility. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.
Centrifugal Impeller Blade Shape Optimization Through Numerical Modeling
Sayed Ahmed Imran Bellary,Abdus Samad 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.4
Surrogate model based shape optimization methodology to enhance performance of a centrifugal pump has been implemented in this work. Design variables, such as blade number and blade angles defining the pump impeller blade shape were selected and a three-level full factorial design approach was used for efficiency enhancement. A threedimensional simulation using Reynolds-averaged Navier Stokes (RANS) equations for the performance analysis was carried out after designing the geometries of the impellers at the design points. Standard k-ε turbulence model was used for steady incompressible flow simulations. The optimized impeller incurred lower losses by shifting the trailing edge towards the impeller pressure side. It is observed that the surrogates are problem dependent and most accurate surrogate does not deliver the best design always.
( Ahmed Sayed Mohammed Nogod Allah ) 단국대학교 GCC국가연구소 2014 걸프지역연구 Vol.2 No.1
The aim of this study is to find out how to own the Middle East Studies Department at the University of dankook oral expression competencies and and identify the main difficulties they face from their perspective. The population of the study consisted of all students of the same University'sMiddle East Studies scholar whom picked delegation (40) randomly sampled for this study, the researcher on the closed questionnaire was adopted as an instrument for the collection of data necessary for the study and after measuring the sincerity and consistency, the researcher used a number of statistical methods of processing the data and found the following results: 1. almlmhai competencies got on top of the arithmetic means that students have to measure the skills of oral expression, followed by intellectual and linguistic and finally the voice side 2-double trust students themselves and theirablities is The main reason for feeling hard-guy students oral expression promoting the confidence of students and their yanfshm and the development of the linguistic and cognitive repertoire and diversifying teaching methods are the most important methods of addressing weaknesses incident guy oral expression. The researcher made a number of recommendations: 1.prepairing educational programmes that contribute to the upgrading and improvement of teaching skills of students 2-traning courses for members teaching in order to familiarize them with competencies of oral expression 3-activating language clubs which help student to improve and develop their oral expression competencies.
Life Span Extension of Caenorhabditis elegans by Novel Pyridoperimidine Derivative
Ahmed A. R. Sayed,Kamal M. El-Shaieb,Aboul-Fetouh E. Mourad 대한약학회 2012 Archives of Pharmacal Research Vol.35 No.1
Zwitterions formed from the addition of triphenylphosphine to dialky acetylene-dicarboxylates attack the nucleus of both 1H-perimidine (1) and 1H-benzo[d]imidazole (9) to form novel pyrido[1,2,3-cd]perimidine and imidazo[4,5,1-ij]quinoline derivatives in moderate yields (64-72%). The biological activity of the products has been studied. Compound 3a was found to extend life span of wild type Caenorhabditis elegans under standard laboratory conditions. Both heat stress and induced chemical stress resistance of wild type C. elegans were improved in a reverse dose-dependent manner due to 3a treatment. In addition, treatment of worms with compound 3a significantly attenuated the formation of advanced glycation end products in a reverse dose-dependent manner.
Effectiveness of meta-models for multi-objective optimization of centrifugal impeller
Sayed Ahmed Imran Bellary,Afzal Husain,Abdus Samad 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12
The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper constructionof low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model isthen used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimalfront which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are notwell-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectivenessfor the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodelswas used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as casestudy to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impellergeometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodelhas been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitationof the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelityof optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximationerror in the Pareto-optimal front.
Experimental Verification of Resistance-Demand Approach for Shear of HSC Beams
Ahmed K. El-Sayed,Ahmed B. Shuraim 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.4
The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.
Control of Open-Loop PWM Delta-Connected Motor-Drive Systems under One Phase Failure Condition
Ahmed Sayed-Ahmed,Nabeel A. O. Demerdash 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.6
A new fault-tolerant control topology for open-loop motor-drive systems with Delta-connected stator windings is introduced in this paper. This new control topology enables the operation of a three-phase induction machine as a two-phase machine fed by a three-phase inverter upon a failure in one of the motor phases. This topology utilizes the “open-Delta” configuration to independently control the current in each of the two remaining healthy phases. This new control technique leads to the alleviation of any torque pulsations resulting from the consequences of the asymmetrical conditions associated with this class of faults.