Influence of pH on the characteristics of cobalt ferrite powder prepared by a combination of sol-gel auto-combustion and ultrasonic irradiation techniques

S. S. Madani,G. Mahmoudzadeh,S. Abedini Khorrami 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2

Cobalt ferrite (CoFe2O4) powders with nanocrystalline sizes were produced by a combination of sol-gel auto-combustion and ultrasonic irradiation methods employing a mixture of urea, thiourea and glycine as the fuel with the corresponding metal nitrates. The pH in the starting solution affects the combustion process, and then determines the particle size of the assynthesized powder. The influence of the pH value on the gel auto-combustion and the phase composition of the synthesized powders have been studied with the help of scanning electron microscopy (SEM) observations, Fourier transform infra red (FTIR) spectroscopy and X-Ray diffraction (XRD) techniques. The synthesized powders had a particle size distribution in the range of 23-43 nm.

Numerical analysis of the combined aging and fillet effect of the adhesive on the mechanical behavior of a single lap joint of type Aluminum/Aluminum

S.M. Medjdoub,K. Madani,L. Rezgani,S. Mallarino,S. Touzain,R.D.S.G. Campilho 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5

Bonded joints have proven their performance against conventional joining processes such as welding, riveting and bolting. The single-lap joint is the most widely used to characterize adhesive joints in tensile-shear loadings. However, the high stress concentrations in the adhesive joint due to the non-linearity of the applied loads generate a bending moment in the joint, resulting in high stresses at the adhesive edges. Geometric optimization of the bonded joint to reduce this high stress concentration prompted various researchers to perform geometric modifications of the adhesive and adherends at their free edges. Modifying both edges of the adhesive (spew) and the adherends (bevel) has proven to be an effective solution to reduce stresses at both edges and improve stress transfer at the inner part of the adhesive layer. The majority of research aimed at improving the geometry of the plate and adhesive edges has not considered the effect of temperature and water absorption in evaluating the strength of the joint. The objective of this work is to analyze, by the finite element method, the stress distribution in an adhesive joint between two 2024-T3 aluminum plates. The effects of the adhesive fillet and adherend bevel on the bonded joint stresses were taken into account. On the other hand, degradation of the mechanical properties of the adhesive following its exposure to moisture and temperature was found. The results clearly showed that the modification of the edges of the adhesive and of the bonding agent have an important role in the durability of the bond. Although the modification of the adhesive and bonding edges significantly improves the joint strength, the simultaneous exposure of the joint to temperature and moisture generates high stress concentrations in the adhesive joint that, in most cases, can easily reach the failure point of the material even at low applied stresses.

Effect of calcination temperature on the particle sizes of zinc ferrite prepared by a combination of sol-gel auto combustion and ultrasonic irradiation techniques

S. Abedini Khorrami,G. Mahmoudzadeh,S. S. Madani,F. Gharib 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5

ZnFe2O4 nanocrystallites were synthesized successfully by a combination of sol-gel auto combustion and ultrasonic irradiation techniques. The influence of the calcination temperature on the particle sizes was investigated. The particles have been calcined at temperatures varying from 400 to 900 oC. The studies were carried out using XRD and SEM techniques. The gradual increase in the crystallite size with the calcination temperature indicates the formation of bigger particles by the calcination.

Optimal Rotor Shape Design of Asymmetrical Multi-Layer IPM Motors to Improve Torque Performance Considering Irreversible Demagnetization

M. S. Mirazimi,A. Kiyoumarsi,S. M. Madani 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

A study on the multi-objective optimization of Interior Permanent-Magnet Synchronous Motors (IPMSMs) with 2, 3, 4 and 5 flux barriers per magnetic pole, based on Genetic Algorithm (GA) is presented by considering the aspect of irreversible demagnetization. Applying the 2004 Toyota Prius single-layer IPMSM as the reference machine, the asymmetrical two-, three-, four- and five-layer rotor models with the same amount of Permanent-Magnets (PMs) is presented to improve the torque characteristics, i.e., reducing the torque pulsation and increasing the average torque. A reduction of the torque pulsations is achieved by adopting different and asymmetrical flux barrier geometries in each magnetic pole of the rotor topology. The demagnetization performance in the PMs is considered as well as the motor performance; and analyzed by using finite element method (FEM) for verification of the optimal solutions.

Nasal septal anatomical variations among Saudi population and their possible coincidence with sinusitis: a computed tomography scan study

Gisma Ahmed Madani,Wael Amin Nasr El-Din,Asmaa S. Essawy,Khamrunissa Hussain,Islam Omar Abdel Fattah 대한해부학회 2022 Anatomy & Cell Biology Vol.55 No.4

The nasal septum is a crucial supporting factor for the nasal cavity and may develop several anatomical variants including septal deviation, spur and pneumatization. These variants could be associated with a higher incidence of sinusitis due to structural and functional alterations. So, the aim of this study was to assess the prevalence of nasal septal deviation (NSD), nasal septal spur (NSS) and nasal septal pneumatization (NSP) among the Saudi adult population and their links with the incidence of sinusitis by using computed tomography (CT). A retrospective study was achieved over a twenty-two months period on 681 adult Saudi subjects (420 males and 261 females) aged 20 years or older, referred for coronal CT evaluation of the paranasal sinuses. NSD and NSS were significantly more prevalent in males than females (80.0% vs. 67.4% respectively for NSD, and 34.5% vs. 24.9% respectively for NSS), while there was no statistical difference in frequency of NSP regarding gender (P=0.670). The incidence of sinusitis was significantly higher in presence of NSD and/or NSS (P<0.001 for both). On the contrary, NSP was not associated with a significant increase in the prevalence of sinusitis (P=0.131). In conclusion, NSD and NSS are more prevalent in males than females among the Saudi population with no statistical difference between both genders regarding the presence of septal pneumatization. Furthermore, sinusitis is more prevalent with the occurrence of NSD and NSS, and not related to the incidence of NSP.

Optimal Rotor Shape Design of Asymmetrical Multi-Layer IPM Motors to Improve Torque Performance Considering Irreversible Demagnetization

Mirazimi, M.S.,Kiyoumarsi, A.,Madani, Sayed M. The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

A study on the multi-objective optimization of Interior Permanent-Magnet Synchronous Motors (IPMSMs) with 2, 3, 4 and 5 flux barriers per magnetic pole, based on Genetic Algorithm (GA) is presented by considering the aspect of irreversible demagnetization. Applying the 2004 Toyota Prius single-layer IPMSM as the reference machine, the asymmetrical two-, three-, four- and five-layer rotor models with the same amount of Permanent-Magnets (PMs) is presented to improve the torque characteristics, i.e., reducing the torque pulsation and increasing the average torque. A reduction of the torque pulsations is achieved by adopting different and asymmetrical flux barrier geometries in each magnetic pole of the rotor topology. The demagnetization performance in the PMs is considered as well as the motor performance; and analyzed by using finite element method (FEM) for verification of the optimal solutions.

Experimental investigation of the pullout behavior of fiber concrete with inclination steel fibers

Seyyed Amir Hossein, Madani,S. Mohammad, Mirhosseini,Ehsanolah, Zeighami,Alireza, NezamAbadi Techno-Press 2022 Advances in concrete construction Vol.14 No.5

Cement-based matrixes have low tensile strength and negligible ductility. Adding fibres to these matrixes will improve their mechanical properties and make these composites suitable for structural applications. Post-cracking tensile strength of steel fibers-reinforced cementitious composite materials is directly related to the number of transverse fibers passing through the crack width and the pulling-out behavior of each of the fibers. Therefore, the exact recognition of the pullout behavior of single fibers is necessary to understand the uniaxial tensile and bending behavior of steel fiber-reinforced concrete. In this paper, an experimental study has been carried out on the pullout behavior of 3D (steel fibers with totally two hooks at both ends), 4D (steel fibers with a total of four hooks at both ends), and 5D (steel fibers with totally six hooks at both ends) in which the fibers have been located either perpendicular to the crack width or in an inclined manner. The pullout behavior of the mentioned steel fibers at an inclination angle of 0, 15, 30, 45, and 60 degrees and with embedded lengths of 10, 15, 20, 25, and 30 millimetres is studied in order to explore the simultaneous effect of the inclination angle of the fibers relative to the alongside loading and the embedded length of fibers on the pullout response in each case, including the maximal pullout force, the slip of the maximum point of pullout force, pullout energy, fiber rupture, and concrete matrix spalling. The results showed that the maximum pullout energy in 3D, 4D, and 5D steel fibers with different embedded lengths occurs at 0 to 30° inclination angles. In 5D fibers, maximum pullout energy occurs at a 30° angle with a 25 mm embedded length.

Impact of bonding defect on the tensile response of a composite patch-repaired structure: Effect of the defect position and size

N. Kaddouri,K. Madani,S.CH. Djebbar,M. Belhouari,R.D.S.G. Campliho 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.6

Adhesive bonding has seen rapid development in recent years, with emphasis to composite patch repairing processes of geometric defects in aeronautical structures. However, its use is still limited given its low resistance to climatic conditions and requirement of specialized labor to avoid fabrication induced defects, such as air bubbles, cracks, and cavities. This work aims to numerically analyze, by the finite element method, the failure behavior of a damaged plate, in the form of a bonding defect, and repaired by an adhesively bonded composite patch. The position and size of the defect were studied. The results of the numerical analysis clearly showed that the position of the defect in the adhesive layer has a large effect on the value of J-Integral. The reduction in the value of J-Integral is also related to the composite stacking sequence which, according to the mechanical properties of the ply, provides better load transfer from the plate to the repair piece through the adhesive. In addition, the increase in the applied load significantly affects the value of the J-Integral at the crack tip in the presence of a bonding defect, even for small dimensions, by reducing the load transfer.

Comparative study of the resistance of bonded, riveted and hybrid assemblies; Experimental and numerical analyses

M.C.Ezzine,K. Madani,M. Tarfaou,S. Touzain,S. Mallarino 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.4

The objective of this work is to analyze by traction tests, the mechanical behavior of an assembly of type metal / metal by various assembly processes; bonding, riveting and hybrid, on the one hand to show the advantage of a hybrid assembly with respect to the other processes, and on the other hand, to analyze by the finite element method the distribution of the stresses in the various components of the structure and to demonstrate the effectiveness of the use of a hybrid assembly with respect to other processes. The number of rivets has been considered. The results show clearly that the value of the different stresses is reduced in the case of a hybrid junction and that the number of rivets in an assembly can be reduced by using a hybrid joint.

Impact of composite patch on the J-integral in adhesive layer for repaired aluminum plate

Kaci, D. Ait,Madani, K.,Mokhtari, M.,Feaugas, X.,Touzain, S. Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.6

The aim of this study is to perform a finite element analysis of the Von Mises stresses distribution in the adhesive layer and of the J-Integral for a damaged plate repaired by a composite patch. Firstly, we study the effect of the fiber orientation, especially the position of the layers that have orientation angle different of $0^{\circ}$ from the first layer which is in all cases of our study oriented at ($0^{\circ}$) on the J-Integral. Secondly, we evaluate the effects of the mechanical properties of the patch and the use of a hybrid patch on the reduction of stresses distribution and J-Integral. The results show clearly that the stacking sequence for the composite patch must be selected to absorb optimally the stresses from the damaged area and to position the various layers of the composite under the first layer whose fibers orientation will remain in all cases equal to $0^{\circ}$. The use of a hybrid composite reduces significantly the J-Integral and the stresses in both damaged plate and the adhesive layer.