Showing 7 results for Fathi
M.h. Fathi, V. Mortazavi, M.a. Golozar and K. Khosravi,
Volume 15, Issue 1 (7-1994)
Abstract
Tarnish and Corrosion behavior of three Commercial dental amalgams namely Am.1, Am.2, Am.3, have been investigated by utilizing in vitro tests. The corrosion and/or dissolution rate of the three dental amalgams were studied in 0.9 wt% NaCl Solution, artificial saliva and Ringers solution. Potentiodynamic polarization technique was employed to study cathodic and anodic polarization behavior, from which the corrosion potentials and corrosion current densities were calculated. The corrosion potential and the corrosion current density of each amalgam was found to be affected by the nature of electrolyte used, as well as the Pre-immersion time. However, the order of corrosion potentials and corrosion current densities of the three dental amalgams examined, was found to be independent of the electrolyte used.
M. H. Fathi, Gh. Feizi, Sb. Moosavi, Gh. Gahanshahi, M. Salehi, A. Saatchi and V. Mortazavi,
Volume 20, Issue 1 (7-2001)
Abstract
Hydroxyapatite coatings have been used on metallic substrates in a variety of applications, including modifying the surface of human implants, bone osseointegration and biological fixation. In this paper, the effects of various kinds of metallic substrate on clinical and pathological results of in vivo tests are presented. Four kinds of endodontic implants i.e, stainless steel, cobalt base alloy, plasma sprayed hydroxyapatite coated stainless steel, plasma sprayed hydroxyapatite coated cobalt base alloy were prapared and implanted in mandibular canine of
cats. After a healing period of 4 months, investigation by SEM and histopathological interpretation and evaluation showed significant differences in tissue response and osseointegration between coated and non-coated metallic implants. It was concluded that the results were affected by the kind of metallic substrate .
Keywords: Hydroxyapatite coating, Dental endodontic implant, Osseointegration, Corrosion, Stainless steel,
Cobalt base alloy
A. Fathi, A. A. Aghakuchak, and Gh. A. Montazer,
Volume 26, Issue 2 (1-2008)
Abstract
In welded tubular joints, when the fatigue crack depth is less than 20% of chord wall thickness, the crack growing process is highly affected by weld geometry.
Hence, T-butt solution and weld magnification factor (Mk) are applicable tools for evaluating the crack growth rate in this domain. In this research, the capability of Artificial Neural Network (ANN) for estimating the Mk of weld toe cracks in T-butt joints is investigated. Four Multi-Layer Perceptron (MLP) networks are designed and trained to predict the Mk in deepest point and ends of weld toe cracks under membrane and bending stresses. Training and testing data of networks are extracted from a reputable resource on finite element modeling. Comparison of the results obtained and those from the most recently published equations shows that using ANN seems to be very beneficial in this field
B. Mostaghaci, M. H. Fathi, M. Sheikh-Zeinoddin, and S. Soleimanianzad,
Volume 27, Issue 2 (1-2009)
Abstract
S. Nasrollahi Boroujeni, M. Fathi, A. Ashrafifar,
Volume 35, Issue 1 (9-2016)
Abstract
In this paper, a robust control law is proposed, based on Lyapunov’s theory and sliding mode control theory, in
order to track the angle of attack in nonlinear longitudinal dynamics of a missile. It is assumed that there are unmatched
uncertainties in the nonlinear systems. In the proposed algorithm, the controller gains are optimized by Particle Swarm
Optimization (PSO) algorithm. For this purpose, a cost function is extracted from the output tracking error. Simulation results
show that the proposed algorithm has better performance than conventional Proportional-Integral-Derivative (PID) controller in
the presence of unmatched uncertainties.
M. Ettefagh, H. Mirab , R. Fathi,
Volume 36, Issue 2 (3-2018)
Abstract
One of the new methods for powering low-power electronic devices employed in the sea, is using of mechanical energies of sea waves. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electrical energy. The advantage of this method is based on not implementing the battery charging system. Although, many studies have been done about energy harvesting from sea waves, energy harvesting with considering random JONWSAP wave theory is not fully studied up to now. The random JONSWAP wave model is a more realistic approximation of sea waves in comparison of Airy wave model. Therefore, in this paper a vertical beam with the piezoelectric patches, which is fixed to the seabed, is considered as energy harvester system. The energy harvesting system is simulated by MATLAB software, and then the vibration response of the beam and consequently the generated power is obtained considering the JONWSAP wave theory. In addition, the reliability of the system and the effect of piezoelectric patches uncertainties on the generated power are studied by statistical method. Furthermore, the failure possibility of harvester based on violation criteria is investigated.
M. Rezaee, M. M. Ettefagh, R. Fathi ,
Volume 39, Issue 1 (8-2020)
Abstract
Although the traditional automatic ball balancer (ABB) has numerous advantages, it has two major deficiencies, i.e., it has a limited balance stable region and it increases the vibration amplitude of the rotor at transient state. These deficiencies limit the applicability of ABBs. In this regard, a new type of ABB called “the Ball-spring autobalancer” has been proposed to resolve the mentioned deficiencies of the traditional ABBs. In order to investigate the capability of the Ball-spring AB in balancing rotors, it is necessary to study its dynamics accurately. The dynamics of a rotor with linear bearing equipped with a Ball-spring AB has been studied previously; however, in real situations, the bearings have nonlinear characteristics. Here, the dynamics of a rotor with nonlinear bearings equipped with a Ball-spring AB is investigated by the multiple scales method for the first time. The results show that the nonlinearity at the rotor bearings does not impair the advantages of the Ball-spring AB.
