Search for: porosity
Total 312 records
Article Results in Materials ; Volume 16 , 2022 ; 2590048X (ISSN) ; Sharif University of Technology
Elsevier B.V 2022
Nanofiber layers have exciting properties such as fine fiber diameter, small pores, suitable connectivity between pores, high surface area and high porosity. These properties make nanofibers applicable for a variety of applications, such as high-performance filters and tissue engineering scaffolds. Different applications of electrospinning layers require different porosities. Therefore, it is very important to measure the porosity of nanofiber layers to express their application. To date, many methods have been expressed for this purpose, but all methods have disadvantages. Therefore, finding the best method is a challenge that will be addressed in this project. © 2022 The Author
Article Scientia Iranica ; Volume 7, Issue 1 , 2000 , Pages 41-49 ; 10263098 (ISSN) ; Simchi, A ; Moradkhani, D ; Ashtari, M ; Khorsand, H ; Davami, P ; Sharif University of Technology
Sharif University of Technology 2000
In this study, microstructural aspects that control fracture and deformation resistance of P/M materials are evaluated. Several low-alloy steels were produced under both experimental and commercial conditions for achieving different matrix phases and porosity levels with varying shape factors. A 'porosity map' was constructed and used for a quantified study of the dominant mechanism controlling mechanical behaviors. The role of inclusion gathering and secondary pores, as well as sintering mechanism and alloying method is considered and discussed. The mechanism assessment was performed by using microstructure examination through optical and scanning electron microscopy. The results...
M.Sc. Thesis Sharif University of Technology ; Sadrhosseini, Hani ; Ashjari, Mohammad Ali
Present study is to simulate laminar flow in a channel exposed to heat flux from the walls and filled with porous media by software ANSYS CFX in finite volume method. The analysis is based on the Naviere-Stokes equations in the flow field which are modified to Brinkman-Forchheimer equations to be applicable for porous media. Effect of Reynolds number and permeability on seepage velocity, temperature distribution, heat transfer and pressure drop are investigated.Simulations are performed for two cases: fully developed flow at the entrance of the porous media and developing flow, which are corresponding to the Reynolds numbers of Re=77.6 and Re=1553 respectively (U= 0.01 m/s and U= 0.2 m/s)....
Article Powder Metallurgy ; Volume 47, Issue 1 , 2004 , Pages 73-80 ; 00325899 (ISSN) ; Danninger, H ; Sharif University of Technology
IOM Communications Ltd 2004
The role of porosity on the wear behaviour of sintered iron was investigated. Sintered iron was used in preference to steel because the various alloy additions and matrix heterogeneity in the latter might affect the microwear behaviour and the role of porosity. The wear tests were performed in a pin on disc test bed under 10-40 N loads at 0·56 m s-1 sliding speed in air. For the given tribological conditions, it was found that the wear mechanism is delamination or mechanical wear, which is basically similar to that of wrought materials according to subsurface crack generation and crack propagation processes. However, the open pores on the surface act as a site for generation and collection...
Article Chemical Engineering Science ; Vol. 107 , April , 2014 , pp. 311-316 ; ISSN: 00092509 ; Morad, M. R ; Matyka, M ; Liu, B ; Malekmohammadi, R ; Weise, J ; Kuypers, M. M. M ; Sharif University of Technology
The correct quantification of porosity is essential in all studies pertaining to porous media. A host of existing works employs a constant, bulk value for porosity, even when the porous sample is attached to a free fluid. Since the volume fraction of the solid matrix near the interface region differs from that in the core, the porosity undergoes a spatial variation. Here we present a novel relation for the porosity as a function of depth below the interface, using the concept of surface roughness applied on the classical definition of open porosity. This relation has been verified by computational modeling as well as non-invasive laser experiments. It has been shown that this depth-dependent...
Article Petroleum Science and Technology ; Vol. 31, issue. 24 , Apr , 2011 , Pages. 2612-2620 ; 10916466 (ISSN) ; Masihi, M ; Sharif University of Technology
The simulation of fractured reservoir is conventionally performed by using dual porosity formulation in which the type of transfer function may be critical. Over the past few years, various models with their strength and weakness have been developed to account for matrix-fracture interporosity flow. However, some of them are unable to simulate some mechanisms like gravity drainage. In this work, the most well-known transfer functions have been examined for simulation of the gravity drainage in a single block model and an improvement has been introduced to modify them. The validation of the developed approach have been done by using fine grid simulation
Article Journal of Iron and Steel Research International ; Volume 18, Issue 4 , 2011 , Pages 44-47+67 ; 1006706X (ISSN) ; Amin Ahmadi, B ; Sharif University of Technology
The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated. Molds with different hardnesses (0.41, 0.48, 0.55, 0.62 MPa) and a sand mold prepared by Co2 method were used. The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated. The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases; therefore, the possibility of achieving a sound product without using any riser increases
Formation of ZrC-WC-W Composites Ceramics by DCP Method and Investigation of Their Physical Properties, Phase Composition and Microstructure, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali ; Mirhabibi, Ali Reza
Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense...
Article International Journal for Numerical and Analytical Methods in Geomechanics ; 2018 ; 03639061 (ISSN) ; Khoei, A. R ; Sharif University of Technology
John Wiley and Sons Ltd 2018
In this paper, a multiscale homogenization approach is developed for fully coupled saturated porous media to represent the idealized sugar cube model, which is generally employed in fractured porous media on the basis of dual porosity models. In this manner, an extended version of the Hill-Mandel theory that incorporates the microdynamic effects into the multiscale analysis is presented, and the concept of the deformable dual porosity model is demonstrated. Numerical simulations are performed employing the multiscale analysis and dual porosity model, and the results are compared with the direct numerical simulation through 2 numerical examples. Finally, a combined multiscale-dual porosity...
Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 13 , 2014 , pp. 1395-1405 ; ISSN: 15567036 ; Ghoodjani, E ; Sharif University of Technology
In this article, dynamic core flood experiments in miscible CO2 condition were carried out to investigate core damage due to asphaltene deposition. Carbonate and sandstone cores were used to study of effect of core characteristic on permeability and porosity reduction. The experimental results show asphaltene deposition preferentially in sandstone core type takes place in the first half of the core while in the carbonate one it occurs in the second half. In spite of asphaltene content measurement results (IP-143) that show higher asphaltene deposition in sandstone cores, permeability impairment compared to the carbonate one is severe. Also, permeability-porosity reduction models are affected...
Article Petroleum Science and Technology ; Volume 31, Issue 16 , 2013 , Pages 1633-1646 ; 10916466 (ISSN) ; Gerami, S ; Sharif University of Technology
The performance of a solution gas-drive reservoir can be predicted using Vogel inflow performance relation (or IPR), which simply relates the deliverability of a well to bottom-hole pressure and average reservoir pressure. While many studies have shown the success of Vogel-type IPR for single porosity reservoirs, the applicability of this method for naturally fractured reservoirs (NFRs), is under question mainly because of the complex flow behavior in matrix and fracture systems. The present study is undertaken to determine if the relation between NFR flowing wellbore pressure and oil production rate could be described by Vogel's IPR. For this purpose, a synthetic dual porosity fractured...
Application of artificial neural network for estimation of formation permeability in an iranian reservoir, Article 1st International Petroleum Conference and Exhibition, Shiraz, 4 May 2009 through 6 May 2009 ; 2009 ; Masihi, M ; Fatholahi, S ; Sharif University of Technology
European Association of Geoscientists and Engineers, EAGE 2009
The permeability is one of the most important reservoir parameters and its accurate prediction is necessary for reservoir management and enhancement. Although many empirical formulas are derived regarding permeability and porosity in sandstone reservoirs , these correlations cannot be modified accurately in carbonate reservoir for the wells which are not cored and there is no welltest data. Therefore estimation of these parameters is a challenge in reservoirs with no coring sample and welltest data. One of the most powerful tools to estimate permeability from well logs is Artificial Neural Network (ANN) whose advantages and disadvantages have been discussed by several authors . In this...
Synthesis of Super-porous Nano Structure Nitinol by Milling using Space Holder Technics and Measure of Termomechanical Properties, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam
NiTi is known as a most important material for manufacturing implants and other medical devises duo to its shape memory and super elasticity properties, high energy damping and high corrosion resistance.In this project the possibility of producing nano structured NiTi implant with high porosity was investigated. For reaching to nano scale mechanical alloying process was done on Ti and Ni powder as row materials. Mechanical alloying process and the possibility of reaching nano structure or amorphous phase was investigated. Space holder technic was used for reaching a porous structure. Sintering process was planned in a way to inhibit grain growth as much as possible. The samples sintered in...
Effect of water-cement ratio on abrasive strength, porosity and permeability of nano-silica concrete, Article World Applied Sciences Journal ; Volume 17, Issue 8 , 2012 , Pages 929-933 ; 18184952 (ISSN) ; Peroti, S ; Rahmani, K ; Rahemi, L ; Sharif University of Technology
Today, due to rapid development of construction of hydraulic structures like dams, the constituent material used in concrete and its durability in these kinds of structures has gained dominant interests and importance. One of the important factors of concrete durability in these structures is its resistance against abrasion due to crash of particles carried out as hydrated crystalline particulate matter. To enhance the abrasion resistance of concrete, different methods have been offered and investigated by many research3ers/ The aim of present article is to investigate the important parameter i.e. water-cement ratio on abrasive strength, porosity and the coefficient of hydraulic conductivity...
Article Second International Conference on Fuel Cell Science, Engineering and Technology, Rochester, NY, 14 June 2004 through 16 June 2004 ; 2004 , Pages 587-594 ; 0791841650 (ISBN); 9780791841655 (ISBN) ; Farhanieh, B ; Saievar Iranizad, E ; Sharif University of Technology
American Society of Mechanical Engineers 2004
Gas diffusion layers are one of the important parts of the PEM fuel cell as they serve to transport the reactant gases to the catalyst layer. Porosity of this layer has a large effect on the PEM fuel cell performance. The spatial variation in porosity arises due to two effects: 1. Compression of the electrode on the solid landing areas and 2. Water produced at the cathode side of gas diffusion layers. Both of these factors change the porosity of gas diffusion layers and affects fuel cell performance. To implement this performance analysis, a mathematical model which considers oxygen and hydrogen mass fraction in gas diffusion layer and the electrical current density in the catalyst layer,...
Microstructural modelling of electrical conductivity and mechanical properties of sintered ferrous materials, Article Powder Metallurgy, London ; Volume 43, Issue 3 , 2000 , Pages 219-227 ; 00325899 (ISSN) ; Danninger, H ; Weiss, B ; Sharif University of Technology
Inst of Materials 2000
The role of microstructure on mechanical properties of sintered ferrous materials was studied using a method based on electrical conductivity measurement. The method was accompanied by quantitative fractography to evaluate the dewaxing and sintering process in iron compacts. The effects of manufacturing parameters, such as compacting pressure in the range of 150-800 MPa, sintering temperature from 400 to 1300 °C, sintering time up to 8 h, and lubrication mode were investigated. Several mathematical models were checked to obtain the best one for prediction of electrical conductivity changes as a function of manufacturing parameters. The mechanical properties of the sintered compacts were also...
Optimization of Porosity Distribution in Functionally Graded Porous Shape Memory Alloy Beams Using Genethic Algorithm, M.Sc. Thesis Sharif University of Technology ; Arghavani Hadi, Jamal
Shape Memory alloys are a kind of intelligent materials developed in recent years due to their comprehensive use in medical, robotics, and other advanced sciences. Two main characteristics of them are shape memory effect and superelasticity put these materials in the category of advanced materials. Recently, the new branch of them attracted many studies which is the porous shape memory alloys. The importance of this class of material is related to their properties such as bio-compatibility, superelasticity and shape memory effect. Since shape memory alloys are usually expensive, a new field is developed known as functionally graded porosity distribution. This method is performed by...
Article Journal of Petroleum Science and Engineering ; Vol. 126, issue , February , 2015 , p. 211-221 ; ISSN: 09204105 ; Masihi, M ; Heinemann, Z. E ; Ghazanfari, M. H ; Sharif University of Technology
The discrete fracture network (DFN) and Multiple-Continua concept are among the most widely used methods to model naturally fractured reservoirs. Each faces specific limitations. The recently introduced recovery curve method (RCM) is believed to be a compromise between these two current methods. In this method the recovery curves are used to determine the amount of mass exchanges between the matrix and fracture mediums. Two recovery curves are assigned for each simulation cell, one curve for gas displacement in the presence of the gravity drainage mechanism, and another for water displacement in the case of the occurrence of the imbibition mechanism. These curves describe matrix-fracture...
Comparison of the membrane morphology based on the phase diagram using PVP as an organic additive and TiO2 as an inorganic additive, Article Polymer (United Kingdom) ; Volume 97 , 2016 , Pages 559-568 ; 00323861 (ISSN) ; Safekordi, A ; Tavakolmoghadam, M ; Rekabdar, F ; Hemmati, M ; Sharif University of Technology
The morphology of symmetric and asymmetric membranes obtained by precipitation can be rationalized by thermodynamic and kinetic parameters. Such parameters which the former relates to thermodynamic effect and the latter controls the time of separation of the cast solution film immersing in the non-solvent bath from the glass plate were calculated as dimensionless parameters for further analysis. Phase diagram was used to consider the role of thermodynamic. The kinetic properties of the membranes could be investigated by the rate of mass transfer between solvent and non-solvent. By adding additives to the polymer solution the desire for becoming two phase and also viscosity of the solution...
Optimal input experiment design and parameter estimation in core-scale pressure oscillation experiments, Article Journal of Hydrology ; Volume 534 , 2016 , Pages 534-552 ; 00221694 (ISSN) ; Mansoori, M ; Bombois, X ; Jansen, J. D ; Van den Hof, P. M. J ; Sharif University of Technology
This paper considers Pressure Oscillation (PO) experiments for which we find the minimum experiment time that guarantees user-imposed parameter variance upper bounds and honours actuator limits. The parameters permeability and porosity are estimated with a classical least-squares estimation method for which an expression of the covariance matrix of the estimates is calculated. This expression is used to tackle the optimization problem. We study the Dynamic Darcy Cell experiment set-up (Heller et al., 2002) and focus on data generation using square wave actuator signals, which, as we shall prove, deliver shorter experiment times than sinusoidal ones. Parameter identification is achieved using...