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Papers by Ahmed Gad
Journal of University of Shanghai for Science and Technology, 2021
In this paper, we will review the methods that used to handle longitudinal data in the case of ma... more In this paper, we will review the methods that used to handle longitudinal data in the case of marginal models when inferences about the population average are the primary focus [1] or when future applications of the results require the expectation of the response as a function of the current covariates [7]. We will review the generalized estimating equations method (GEE), quadratic inference functions (QIF), generalized quasi likelihood (GQL) and the generalized method of moments (GMM). These methods will be reviewed by discussing its advantages and disadvantages in more details.
Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfoni... more Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSNa), was carried out using chronoamperometric technique. Cyclic voltammetry measurements showed that the electroactivity of PPY films, doped with AMPSNa, increases with the film thickness. Scanning electron microscopy photographs revealed that the PPY particles are in the nano-scale range and that their size depends on the potential at which the PPY has formed. Electrochemical impedance spectroscopy (EIS), in the potential range of + 1.0 and − 1.0 V, revealed in the PPY film charge transfer domination with a semicircle at high frequencies, and anion diffusion dominance at low frequencies. EIS also showed that the charge transfer resistance of PPY film at − 1.0 V is lower than what is expected and that on increasing the thickness of the PPY films, the overall impedance decreases. The proposed equivalent circuit model, based on the double layer capacity and the Warburg impedance, was replaced by two constant-phase elements to fit the experimental work of this study. The values of the fractional exponent of the first constant phase element at approximately 0.5 indicate that the processes have a diffusion-limited nature.
Journal of University of Shanghai for Science and Technology, 2021
In this paper, we will review the methods that used to handle longitudinal data in the case of ma... more In this paper, we will review the methods that used to handle longitudinal data in the case of marginal models when inferences about the population average are the primary focus [1] or when future applications of the results require the expectation of the response as a function of the current covariates [7]. We will review the generalized estimating equations method (GEE), quadratic inference functions (QIF), generalized quasi likelihood (GQL) and the generalized method of moments (GMM). These methods will be reviewed by discussing its advantages and disadvantages in more details.
Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfoni... more Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSNa), was carried out using chronoamperometric technique. Cyclic voltammetry measurements showed that the electroactivity of PPY films, doped with AMPSNa, increases with the film thickness. Scanning electron microscopy photographs revealed that the PPY particles are in the nano-scale range and that their size depends on the potential at which the PPY has formed. Electrochemical impedance spectroscopy (EIS), in the potential range of + 1.0 and − 1.0 V, revealed in the PPY film charge transfer domination with a semicircle at high frequencies, and anion diffusion dominance at low frequencies. EIS also showed that the charge transfer resistance of PPY film at − 1.0 V is lower than what is expected and that on increasing the thickness of the PPY films, the overall impedance decreases. The proposed equivalent circuit model, based on the double layer capacity and the Warburg impedance, was replaced by two constant-phase elements to fit the experimental work of this study. The values of the fractional exponent of the first constant phase element at approximately 0.5 indicate that the processes have a diffusion-limited nature.