Search for: tortuosity
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    Simple and efficient method to measure vessel tortuosity

    , Article Proceedings of the 3rd International Conference on Computer and Knowledge Engineering, ICCKE 2013, Mashhad: Iran ; 2013 , Pages 219-222 ; 9781479920921 (ISBN) Pourreza, H. R ; Pourreza, M ; Banaee, T ; Sharif University of Technology
    Retinal vessels tortuosity is one of the important signs of cardiovascular diseases such as diabetic retinopathy and hypertension. In this paper we present a simple and efficient algorithm to measure the grade of tortuosity in retinal images. This algorithm consists of four main steps,vessel detection, extracting vascular skeleton via thinning, detection of vessel crossovers and bifurcations and finally calculating local and global tortuosity. The last stage is based on a circular mask that is put on every skeleton point of retinal vessels. While the skeleton of vessel splits the circle in each position, the local tortuosity is considered to be the bigger to smaller area ratio. The proposed... 

    Pore scale study of permeability and tortuosity for flow through particulate media using Lattice Boltzmann method

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 35, Issue 8 , 2011 , Pages 886-901 ; 03639061 (ISSN) Ghassemi, A ; Pak, A ; Sharif University of Technology
    In this paper, Lattice Boltzmann method (LBM) has been used to study the effects of permeability and tortuosity on flow through saturated particulate media and identify the relationships between permeability and tortuosity with other parameters such as particles diameter, grain specific surface, and porosity. LBM is a simple kinematic model that can incorporate the essential physics of microscopic and mesoscopic processes involved in flow through granular soils. The obtained results indicate that the 2D LB model, due to its inherent theoretical advantages, is capable of demonstrating that the porosity and specific surface are the most influential parameters in determining the intrinsic... 

    A new insight into onset of inertial flow in porous media using network modeling with converging/diverging pores

    , Article Computational Geosciences ; Volume 22, Issue 1 , February , 2018 , Pages 329-346 ; 14200597 (ISSN) Veyskarami, M ; Hassani, A. H ; Ghazanfari, M. H ; Sharif University of technology
    Springer International Publishing  2018
    The network modeling approach is applied to provide a new insight into the onset of non-Darcy flow through porous media. The analytical solutions of one-dimensional Navier-Stokes equation in sinusoidal and conical converging/diverging throats are used to calculate the pressure drop/flow rate responses in the capillaries of the network. The analysis of flow in a single pore revealed that there are two different regions for the flow coefficient ratio as a function of the aspect ratio. It is found that the critical Reynolds number strongly depends on the pore geometrical properties including throat length, average aspect ratio, and average coordination number of the porous media, and an... 

    An approach to defining tortuosity and cementation factor in carbonate reservoir rocks

    , Article Journal of Petroleum Science and Engineering ; Volume 60, Issue 2 , 2008 , Pages 125-131 ; 09204105 (ISSN) Hassanzadeh Azar, J ; Javaherian, A ; Pishvaie, M. R ; Nabi Bidhendi, M ; Sharif University of Technology
    Tortuosity and cementation factor are two critical parameters that significantly affect estimates of reservoir properties. Tortuosity factor can be used to estimate permeability using the Carman-Kozeny equation and is an important parameter for formation resistivity factor calculation using a modified version of Archie's formula. It is also used to predict water saturation of reservoir rocks. Tortuosity as an input parameter in Biot's equation can be used to estimate velocity dispersion. In this work, based on the Generalized Archie Equation Curve Fitting (GAECF), tortuosity and cementation factor are determined for selected intervals in a carbonate reservoir. Formation resistivity factor... 

    Molecular Diffusion in the Dynamics Brain Extracellular Space

    , Ph.D. Dissertation Sharif University of Technology Yousefnezhad, Mohsen (Author) ; Fotouhi, Morteza (Supervisor) ; Kamali Zare, Padideh (Co-Advisor) ; Vejdani, Kaveh (Co-Advisor)
    In the thesis , we present a universal model of brain tissue microstructure that dynamically links osmosis and diffusion with geometrical parameters of brain extracellular space (ECS) . In the first part , we investigate the biological aspects of the model , and in the second , we analysis the model in the mathematical framework . The first part : Our model robustly describes and predicts the nonlinear time dependency of tortuosity ($\lambda = \sqrt{D/{D^{*}}}$) changes with very high precision in various media with uniform and nonuniform osmolarity distribution , as demonstrated by previously published experimental data ($D$ = free diffusion coefficient , $D^{*}$ = effective...