Sharif Digital Repository

A theoretical model was developed to describe a dynamic process involving an enzymatic reaction and diffusion of reactants and product inside glucose sensitive composite membrane. The composite membrane consisted of nanoparticles of a weakly acidic polymer, glucose oxidase and catalase embedded in a hydrophobic polymer. Time- and position-dependent diffusivity of involved species was considered in the model. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of pH, species concentrations, volume fraction of swollen gel, polymer and water-filled space, as well as solute diffusivity inside the membrane were predicted by the model as a function... 

A theoretical model concerning simultaneous diffusion and reaction was developed to describe the steady state behavior of a cationic glucose-sensitive membrane with consideration of oxygen limitation and swelling-dependent diffusivities of involved species inside the membrane. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of species concentrations, pH, polymer volume fraction and solute diffusivity inside the membrane were predicted by the model in response to step changes of glucose concentration in the external solution. The influence of various factors on the responsiveness of the membrane was analyzed using the model. The results... 

This paper shows a new possible way with particle swarm optimisation (PSO) to achieve an exergoeconomic optimisation of combinedcycle power plants. The optimisation has been done using a classic exergoeconomic and genetic algorithm, and the effects of using three methods are investigated and compared. The design data of an existing plant is used for the present analysis. Two different objective functions are proposed: One minimises the total cost of production per unit of output, and maximises the total exergetic efficiency. The analysis shows that the total cost of production per unit of output is 2%, 3%and 5% lower and exergy efficiency is 4%, 8% and 6% higher with respect to the base case... 

In this paper, we report on the design, simulation and measurement of a flat-top beam shaper (FBS) lens for a millimeter-wave (mm-wave) antenna coupled source. The beam shaper is designed to transform the pseudo-Gaussian beam of the mm-wave source into a flat-top beam of sharp roll-off at a specific distance in the Fresnel region. Firstly, relying on the geometrical optics principles, we propose an analytical formulation for the design of lens profiles. Next, a simple optimization method based on the full-wave simulation of the lens and the mm-wave antenna is suggested to tune the analytically extracted lens profile. The optimized lens profile is then studied to assess its performance... 

In this paper, we report on the design, simulation and measurement of a flat-top beam shaper (FBS) lens for a millimeter-wave (mm-wave) antenna coupled source. The beam shaper is designed to transform the pseudo-Gaussian beam of the mm-wave source into a flat-top beam of sharp roll-off at a specific distance in the Fresnel region. Firstly, relying on the geometrical optics principles, we propose an analytical formulation for the design of lens profiles. Next, a simple optimization method based on the full-wave simulation of the lens and the mm-wave antenna is suggested to tune the analytically extracted lens profile. The optimized lens profile is then studied to assess its performance... 

Diffusivity equation which can provide us with the pressure distribution, is a Partial Differential Equation (PDE) describing fluid flow in porous media. The quadratic pressure gradient term in the diffusivity equation is nearly neglected in hydrology and petroleum engineering problems such as well test analysis. When a compressible liquid is injected into a well at high pressure gradient or when the reservoir possess a small permeability value, the effect of ignoring this term increases. In such cases, neglecting this parameter can result in high errors. Previous models basically focused on numerical and semi-analytical methods for semi-infinite domain. To the best of our knowledge, no... 

The Weibull distribution plays an important role in failure distribution modeling of reliability research. While there are three parameters in the general form of this distribution, for simplicity, one of its parameters is usually omitted and as a result, the others are estimated easily. However, due to its more flexibility, when the general form of the Weibull distribution is of interest, the estimation procedure is not an easy task anymore. For example, in the maximum likelihood estimation method, the likelihood function that is formed for a three-parameter Weibull distribution is very hard to maximize. In this paper, a new hybrid methodology based on a variable neighborhood search and a... 

In this study, a neural network (NN) modeling approach has been used to predict the mechanical and geometrical behaviors of mouse embryo cells. Two NN models have been implemented. In the first NN model dimple depth (w), dimple radius (a) and radius of the semi-circular curved surface of the cell (R) were used as inputs of the model while indentation force (f) was considered as output. In the second NN model, indentation force (f), dimple radius (a) and radius of the semi-circular curved surface of the cell (R) were considered as inputs of the model and dimple depth was predicted as the output of the model. In addition, sensitivity analysis has been carried out to investigate the influence...