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Search Results: 1 - 10 of 703 matches for " Abdelaziz Nasr "
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Synthesis of Ti3SiC2-Bicarbide Based Ceramic by Electro-Thermal Explosion  [PDF]
Nasr-Eddine Chakri, Zoubida Habes, Abdelaziz Toubal, Badis Bendjemil
Advances in Chemical Engineering and Science (ACES) , 2014, DOI: 10.4236/aces.2014.42027
Abstract:

A polycrystalline dense Ti3SiC2 based ceramic material has been produced by several techniques. The effect of addition of TiC and SiC is also studied. The Ti3SiC2 material shows extraordinary electrical, thermal and mechanical properties. Furthermore, it shows a damage tolerance capability and oxidation resistance. In this work, we have synthesized Ti3SiC2 by electro-thermal explosion chemical reaction (ETE) with high current density (900 Amperes/a.u) followed by uniaxial pressure. The structural properties of the as-prepared materials are studied by x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDX) techniques. The chemical cartography, imaging and electronic properties are investigated using Ultra-STEM and electron high energy loss resolution spectroscopy (EELS) techniques, respectively. The surface of Ti3SiC2 is characterized by means of X-ray photoelectron spectroscopy (XPS). High resolution C 1s, Si 2p, Ti 2p, Ti 3s core level spectra are explained in terms of crystallographic and electronic structure. Valence band spectrum is performed to confirm the validity of the theoretical calculations.

Evaporation of a binary liquid film by forced convection
Nasr Abdelaziz,Debbissi Chokri,Nasrallah Ben Sassi
Thermal Science , 2011, DOI: 10.2298/tsci100427076n
Abstract: This paper deals with a numerical analysis of the evaporation of a thin binary liquid film by forced convection inside a channel constituted by two parallel plates. The first plate is externally insulated and wetted by a thin water ethylene glycol film while the second is dry and isothermal. The liquid mixture consists of water (the more volatile component) and ethylene glycol while the gas mixture has three components: dry air, water vapour and ethylene-glycol vapour. The set of non linear and coupled equations expressing the conservation of mass, momentum, energy and species in the liquid and gas mixtures is solved numerically using a finite difference method. Results concerns with the effects of inlet ambience conditions and the inlet liquid concentration of ethylene glycol on the distribution of the temperature, concentrations profiles and the axial variation of the evaporation rate of species i.
An Efficient and Convenient Synthesis of Certain 2-Thioxothiazole,2-oxo-1,2-dihydropridine, 2-Oxo-2H-pyran,2,4-diaminothiophene and Pyrazolo[5,1-c][1,2,4]triazine Derivatives Containing Antipyrine Moiety  [PDF]
Seif-Eldin Nasr Ayyad, Fathy Muhammad Abdelaziz El-Taweel, Abdel-Ghani Ali Elagamey, Tahani Mahmoud El-Mashad
International Journal of Organic Chemistry (IJOC) , 2012, DOI: 10.4236/ijoc.2012.22021
Abstract: 2-Thioxothiazole derivatives 5a-c were prepared by reacting a mixture of 1a-c, CS2/KOH and 4-(2-chloroacetyl)-1, 5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one(3). Reacting 2-cyano-N-(4-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-2H- pyrazol-4-yl)-2-thioxothiazol-3(2H)-yl)acetamide (5c) with mercaptoacetic acid, arylidenemalononitriles 8 and (E)- 3-(dimethylamino)-1-(furan-2-yl)prop-2-en-1-one (12) give 4-oxo-4,5-dihydrothiazole 6, 2-oxo-1,2-dihydropyridine 10 and 2-oxo-2H-pyran 15 respectively. Heating a mixture of 5c, malononitrile and elemental sulfur yield 2,4-diaminothio- phene 19. Coupling of 5c with the diazotized aminopyrazole 20 and aryldiazonium salts 23 give pyrazolo[5,1-c][1,2,4] triazines 22 and arylhydrazones 25 respectively.
Evaporation of Water by Natural Convection in Partially Wetted Heated Vertical Plates: Effect of the Number of the Wetted Zone
Abdelaziz Nasr,Chokri Debissi,Amine Belhadj Mohamed,Jamel Orfi,Sassi Ben Nasrallah
Journal of Engineering and Applied Sciences , 2012,
Abstract: This research consists of a numerical investigation of coupled heat and mass transfers by natural convection during water evaporation in a vertical channel. The two channel walls were symmetrically heated by a uniform flux density. One wall is partially wetted by an extremely thin water film and the other is dry. The partially humid plate is divided into 2N with equal lengths being alternatively wet and dry zones. The results are reported in terms of local Sherwood number, the inlet velocity and evaporative rate for different wet zone position and for different wet number zones. However, the mass transfer is extremely influenced by the number of the wetted zones and their positions. The evaporative rate is more intense when the wetted zone is situated at the channel exit. Finally, it is observed that the evaporation is intensified by increasing the number of wetted zones.
Numerical Analysis of the Evaporation of Water by Forced Convection into Humid Air in Partially Wetted Vertical Plates
Chokri Debissi Hfaiedh,Abdelaziz Nasr,Jamel Orfi,Amine Belhadj Mohamed,Sassi Ben Nasrallah
Journal of Engineering and Applied Sciences , 2012,
Abstract: The present study focuses on a numerical investigation of steady conjugated heat and mass transfers by forced convection in an externally heated or insulated channel. One wall is partially wetted by an extremely thin water film, while the other is dry and impermeable. The partially humid plate is divided into 2.n equal regions, which are alternately humid and dry zones. The effect of the number of wetted zones and their positions on the flow, on the heat and mass transfers is analysed. The results are reported in terms of axial distribution of wall temperature, relative heat fluxes and evaporative rate for different wetted zone positions. It is noticed that the change of the wetted zone position has no significant effect on the moist air flow. However, the heat and mass transfers are extremely influenced by the presence of the wetted zones and their positions. As the condition of an insulated channel, the evaporative rate is more intense when the wetted zone is situated at the channel entrance. In case of the condition of a heated wall channel, the situation is generally inversed. It is also shown that there exists a critical value for the density heat flux from which the behaviour of the evaporative rate is reversed. Finally, it is noticed that the evaporation is intensified by increasing the number of humid zones.
Recurrence of Space-Time Events  [PDF]
Nasr Ahmed
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.613182
Abstract: A causal-directed graphical space-time model has been suggested in which the recurrence phenomena that happen in history and science can be naturally explained. In this Ramsey theorem inspired model, the regular and repeated patterns are interpreted as identical or semi-identical space-time causal chains. The “same colored paths and subgraphs” in the classical Ramsey theorem are interpreted as identical or semi-identical causal chains. In the framework of the model, Poincare recurrence and the cosmological recurrence arise naturally. We use Ramsey theorem to prove that there’s always a possibility of predictability no matter how chaotic the system is.
Constraints Based Decision Support for Site-Specific Preliminary Design of Wind Turbines  [PDF]
Abdelaziz Arbaoui, Mohamed Asbik
Energy and Power Engineering (EPE) , 2010, DOI: 10.4236/epe.2010.23024
Abstract: This study presents a decision-support tool for preliminary design of a horizontal wind turbine system. The function of this tool is to assist the various actors in making decisions about choices inherent to their activities in the field of wind energy. Wind turbine cost and site characteristics are taken into account in the used models which are mainly based on the engineering knowledge. The present tool uses a constraint-modelling technique in combination with a CSP solver (numerical CSPs which are based on an arithmetic interval). In this way, it generates solutions and automatically performs the concept selection and costing of a given wind turbine. The data generated by the tool and required for decision making are: the quality index of solution (wind turbine), the amount of energy produced, the total cost of the wind turbine and the design variables which define the architecture of the wind turbine system. When applied to redesign a standard wind turbine in adequacy with a given site, the present tool proved both its ability to implement constraint modelling and its usefulness in conducting an appraisal.
Modulation Equations for Roll Waves on Vertically Falling Films of a Power-Law Fluid  [PDF]
Abdelaziz Boudlal, Valery Liapidevskii
World Journal of Mechanics (WJM) , 2012, DOI: 10.4236/wjm.2012.21001
Abstract: Waves of finite amplitude on a thin layer of non-Newtonian fluid modelled as a power-law fluid are considered. In the long wave approximation, the system of equations taking into account the viscous and nonlinear effects has the hyper- bolic type. For the two-parameter family of periodic waves in the film flow on a vertical wall the modulation equations for nonlinear wave trains are derived and investigated. The stability criterium for roll waves based on the hyperbolicity of the modulation equations is suggested. It is shown that the evolution of stable roll waves can be described by self-similar solutions of the modulation equations.
Calculation of Atomic Data and Gain Coefficient for XUV & Soft X-Ray Laser Emission from Ge XXIII  [PDF]
Wessameldin S. Abdelaziz
Optics and Photonics Journal (OPJ) , 2014, DOI: 10.4236/opj.2014.49025
Abstract: Energy levels, transition probabilities, oscillator strengths, and collision strengths have been calculated for transitions in Ne-like Ge. The data refer to a 241 fine-structure levels belonging to the configurations 1s2 2s2 2p5nl, 1s2 2s1 2p6nl (n = 3, 4, 5, 6; l = s, p, d, f, g and h), which have been calculated by the fully relativistic flexible atomic code (FAC). These data are used in the determination of the reduced population for the 241 fine structure levels and gain coefficients over a wide range of electron densities (from 2 × 10+20 to 4 × 10+22 cm-3) and at various electron plasma temperatures (650, 850, 1050, 1250, 1450, 1650, 1850) eV by using the MATLAB R2013a Computer program for solving simultaneous coupled rate equations. The reduced population for the 241 fine structure levels the gain coefficients for those transitions with positive population inversion factor are determined and plotted against the electron density.
Immersive Learning Design (ILD): A New Model to Assure the Quality of Learning through Flipped Classrooms  [PDF]
Hamdy A. Abdelaziz
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.211027
Abstract: The objective of this paper was to develop an immersive Web-based learning model to assure the quality of learning through the flipped classrooms. The proposed model was guided theoretically by the flipped classroom as a new Web-based learning trend/system. It was also guided pedagogically by active and reflective learning principles that support transforming of the teaching and learning practices from content engagement to cognitive engagement. The targeted immersive learning model encompasses four reciprocal phases: Pro-act, Act, Reflect, and Re-act (PARR). To validate the suggested model, a convenience sample of graduate students studying an advanced statistics course was selected from the Distance Teaching and Training Program at Arabian Gulf University. After designing and applying this new immersive Web-based learning model (PARR), findings revealed that using the flipped classroom through this immersive Web-based learning model has a statistical and practical impact on developing achievement and self-study skills among graduate students. The contribution of this research is that it qualifies the Web-based instructional practices to shift from content acquisition act to knowledge expression and creation act. In addition, the paper will be of benefit to people looking for pedagogical applications of virtual and blended learning environments for developing multiple ways to express what learners know and be able to do.
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