فهرست مطالب davod mohebbi

One of the main challenges facing the current Egyptian government is the challenge of the status of Islam in the structure of its constitutional law. The second principle of the last Egyptian constitution (approved in 2014) states the extent of Islam's entry into the domain of governance. This principle, which is based on the former constitutions, considers the minimum position for observance of Islamic rules and, based on the obstruction of the Ijtihad, recognizes only the definitive Islamic rules valid for conforming laws with them. The parliament and the judiciary have no obligation to observe the famous jurisprudents' opinion and are not obliged to follow a particular reading of the Islamic law. There is no statutory place for the institution to protect Islamic law and the body of the Council of elders of Al-Azhar, which was also in the former constitution, has been removed and he position of al-Azhar has been reduced to a mere scientific institution. Due to the minimal presence of people in the referendum of the constitution, it can be concluded that the Egyptian constitution has tended to secularism, contrary to the opinion of the absolute majority of the people.

The power density of a direct methanol fuel cell (DMFC) stack as a function of temperature, methanol concentration, oxygen flow rate, and methanol flow rate was studied using a response surface methodology (RSM) to maximize the power density. The operating variables investigated experimentally include temperature (50-75 °C), methanol concentration (0.5-2 M), methanol flow rate (15-30 ml min-1), and oxygen flow rate (900-1800 ml min-1). A new design of the central composite design (CCD) for a wide range of operating variables that optimize the power density was obtained using a quadratic model. The optimum conditions that yield the highest maximum power density of 86.45 mW cm-2 were provided using 3-cell stack at a fuel cell temperature of 75 °C with a methanol flow rate of 30 ml min-1, a methanol concentration of 0.5 M, and an oxygen flow rate of 1800 ml min-1. Results showed that the power density of DMFC increased with an increase in the temperature and methanol flow rate. The experimental data were in good agreement with the model predictions, demonstrating that the regression model was useful in optimizing maximum power density from the independent operating variables of the fuel cell stack.

The effect of the thickness of ceramic membrane on the productivity of microbial fuel cells (MFCs) was investigated with respect to the electricity generation and domestic wastewater treatment efficiencies. The thickest ceramic membrane (9 mm) gained the highest coulombic efficiency (27.58±4.2 %), voltage (681.15±33.1 mV), and current and power densities (447.11±21.37 mA/m2, 63.82±10.42 mW/m2) compared to the 6- and 3-mm thick separators. The results of electrochemical impedance spectroscopy (EIS) analysis were investigated to identify the internal resistance constituents by proposing the appropriate equivalent electrical circuit. The Gerischer element was modeled as the coupled reaction, and diffusion in the porous carbon electrodes and the constant phase element was assimilated into the electrical double-layer capacitance. The thickest ceramic (9 mm) was found to have the largest ohmic resistance; however, owing to its superior barrier capability, it provided more anoxic conditions for better accommodation of exoelectrogenic bacteria in the anode chamber. Therefore, lower charge transfer, fewer diffusional impedances, and higher rates of anodic reactions were achieved. Excessive oxygen and substrate crossover through the thinner ceramics (of 6 and 3 mm) resulted in the suppressed development of anaerobic anodic biofilm and the accomplishment of aerobic substrate respiration without electricity generation.

Nodaway, membrane methods such as ultrafiltration have been considered to separating pollutions from fluids. The governing equations indicate the role of cartridge geometry on the separation process. The present study is carried out to investigate the effect of cartridge geometry on the separation performance of a hollow fiber ultrafiltration system. Numerical Modeling are divided into three categories, include circle, square, and triangle. The region including fibers is considered as a porous medium. Results show in the same conditions, the use of square and triangular geometry reduce transemembrane pressure, cake thickness and consequently the cake resistance and the membrane resistance compared to circle. Also, triangle geometry has shown better performance under changes in inflow and packaging density and the time to reach the same thickness of the cake is more than the other two geometries.

Membrane processes are one of the most important separation methods in water and wastewater treatment processes. Hollow fiber membranes are used in many separation processes due to their high surface area to volume ratio. Since porosity and permeability of porous media depend on its geometric features, a change in the geometry leads to changes in these value and the performance of the system. In this study, a mathematical modeling was made for three fiber geometry categories; including circular, square and elliptical and the geometric features were calculated based on three strategies. In order to investigate the effect of geometry, a double porosity media was considered. Results showed that the ratio of surface area to volume of hollow fiber membranes and the axial permeability in square and elliptic geometries are usually higher than circular fibers and are increased to a maximum value of 27% and 63%, respectively. Also, in a strategy, equivalence of the radius of the inspirational circle of the new geometry with the inner radius of ordinary fibers was less than the circular fiber, which was a desired result and caused a decrease in energy consumption and operation cost of the system.