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madadi-mogharrab--j
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Experimental study and surface complexation modeling of non-monotonic wettability behavior due to change in brine salinity/composition: Insight into anhydrite impurity in carbonates
, Article Journal of Molecular Liquids ; Volume 365 , 2022 ; 01677322 (ISSN) ; Ayatollahi, S ; Pishvaie, M. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Wettability alteration as the main mechanism of improved oil recovery in carbonates during low salinity/engineered water flooding (LS/EWF) is a complex phenomenon due to high heterogeneity of rock. During LS/EWF, wettability changes when electrochemical interactions at carbonate-brine interface happen. Anhydrite impurity in carbonates is one of the most important parameters affecting the electrochemical interactions at the rock-brine interface and the wettability alteration process. Therefore, the success of LS/EWF in carbonate reservoirs lies in perceiving the role of impurities such as anhydrite, from a geochemical and dissolution point of view. Modified flotation tests (MFT) were...
Smart Water Optimal Injection Policy in Fractured Carbonate Reservoirs, Using Laboratory Data
, Ph.D. Dissertation Sharif University of Technology ; Ayatollahi, Shahaboddin (Supervisor) ; Pishvaie, Mahmood Reza (Supervisor)
Abstract
Wettability alteration is the main mechanism for enhancing oil recovery in carbonate reservoirs during low salinity or engineered water flooding (LS/EWF), though it is a complex process due to the high heterogeneity of rock. During LS/EWF, wettability alteration occurs as a result of electrochemical interactions at the interface between carbonate rock and brine. One of the most critical factors affecting these interactions, and the wettability alteration process, is the presence of anhydrite impurities in the carbonate rock. Therefore, the success of LS/EWF in carbonate reservoirs lies on understanding the role of impurities like anhydrite from both geochemical and dissolution perspectives....
Iranian Professional Football League’s Scheduling
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Ferydoon (Supervisor)
Abstract
Finding a proper and fair schedule for sport competitions has been an important issue, especially these days which professional sports has became a large scale business and profitability of sport competitions depends on the quality of the schedule.
Hence in the last three decades sport scheduling has been considered by computer science and operation research scientists.
Professional soccer league consists of many teams which compete in one round or double round robin tournament every year. In round robin tournaments each team has two matches, one at their own place and the other one at the competitors place. The main issues of the sport scheduling are the round and the host of...
Hence in the last three decades sport scheduling has been considered by computer science and operation research scientists.
Professional soccer league consists of many teams which compete in one round or double round robin tournament every year. In round robin tournaments each team has two matches, one at their own place and the other one at the competitors place. The main issues of the sport scheduling are the round and the host of...
Investigation of Plasmonic Excitation in Carbonic Nanostructures Within Near-IR
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Zahra (Supervisor)
Abstract
To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have...
Vector space generated by the multiplicative commutators of a division ring
, Article Journal of Algebra and its Applications ; Volume 12, Issue 8 , December , 2013 ; 02194988 (ISSN) ; Akbari, S ; Ariannejad, M ; Madadi, A ; Sharif University of Technology
2013
Abstract
Let D be a division ring with center F. An element of the form xyx -1y-1 ∈ D is called a multiplicative commutator. Let T(D) be the vector space over F generated by all multiplicative commutators in D. In this paper it is shown that if D is algebraic over F and Char(D) = 0, then D = T(D). We conjecture that it is true in general. Among other results it is shown that in characteristic zero if T(D) is algebraic over F, then D is algebraic over F
Performance predicting modeling of axial-flow compressor at design and off-design conditions
, Article Proceedings of the ASME Turbo Expo, 9 June 2008 through 13 June 2008, Berlin ; Volume 6, Issue PART A , 2008 , Pages 317-324 ; 9780791843161 (ISBN) ; Hajilouy Benisi, A ; International Gas Turbine Institute ; Sharif University of Technology
2008
Abstract
Axial flow compressor is one of the most important parts of gas turbine units. Therefore, its design and performance prediction are very important. One-dimensional modeling is a simple, fast and accurate method for performance prediction of any type of compressors with different geometries. In this approach, inlet flow conditions and compressor geometry are known and by considering various compressor losses, velocity triangles at rotor, and stator inlets and outlets are determined, and then compressor performance characteristics are predicted. Numerous models have been developed theoretically and experimentally for estimating various types of compressor losses. In present work, performance...
Optical analog of Matthiessen's rule in a one-dimensional model for diffusive light transport in foams
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 82, Issue 4 , 2010 ; 15393755 (ISSN) ; Kheradsoud, S ; Madadi, E ; Mokhtari, Z ; Hassani, H ; Sharif University of Technology
2010
Abstract
We study photon diffusion in a one-dimensional model foam composed of thin films and Plateau borders. Each thin film or Plateau border is characterized by its own intensity transmittance. We relate | Foam, the transport-mean-free path of photons diffusing in the foam, to the foam microstructure. Denoting by l Film (l PB) the transport-mean-free path of photons in a medium composed only of thin films (Plateau borders), we find 1/ l Foam = φF / l Film + φP / l PB. Here φF and φP =1- φF are the fraction of films and Plateau borders, respectively
Analysis of mechanical and thermal properties of carbon and silicon nanomaterials using a coarse-grained molecular dynamics method
, Article International Journal of Mechanical Sciences ; Volume 187 , December , 2020 ; Ali Madadi, A ; Bajalan, Z ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The main concern in Molecular Dynamics (MD) simulations is the computational cost, and coarse-graining methods accelerate simulations by reducing the degrees of freedom in the system. Yet, the utilization of these methods should be carefully followed. In this paper, we presented an energy-based coarse-graining method for Tersoff and Stillinger-Weber potential functions. The presented coarse-graining method is based on the domain mapping and modification of potential function. The focus of this paper is on Carbon and Silicon materials; however, this method can be applied to model other materials for which Tersoff and Stillinger-Weber potentials are defined. This method has been validated by...
Coarse Grained-Atomistic Concurrent Multi-Scale Modeling for Numerical Simulation of Mechanical Behavior of Heterogeneous Materials in Nano-cale
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this thesis, a method has been exploited to couple the atomistic domain with the coarse-grained domain. Since molecular dynamics has a high computational cost when a large number of atoms exist, coarse-grained molecular dynamics was used in which a number of atoms are assumed as a bigger bid and interatomic potential is modified for bids so that the material’s mechanical properties remain constant. This method not only reduces the computational cost of calculating forces in molecular dynamics simulation but also, the time step used in Coarse-Grained Methods can be more than atomistic simulations as the frequency of occurring phenomena in CG scale is less than atomistic scale.The advantage...
Tube length-assisted optimized aerosol trapping
, Article Optics Communications ; Vol. 329, issue , 2014 , pp. 196-199 ; ISSN: 00304018 ; Sadeghi, M ; Madadi, E ; S. Reihani, S. N ; Sharif University of Technology
2014
Abstract
Trapping a single aerosol using optical tweezers could be of great importance for environmental sciences. Though a single nanoparticle as small as 10 nm is successfully trapped in aqueous media using optical tweezers, due to spherical aberration only large clusters of nanoparticles were stably trapped in air. In this paper we provide our theoretical and experimental results on optimized trapping of aerosols as small as 400 nm in radius by the introduction of an extra spherical aberration source in order to minimize the total spherical aberration of the system. Our method allows for trapping of high refractive index particles such as polystyrene beads in air. It also provides considerably...
Functional compartmentalization in the hemocoel of insects
, Article Scientific Reports ; Volume 9, Issue 1 , 2019 ; 20452322 (ISSN) ; Aviles, J ; Adjerid, K ; Schoenewald, C ; Socha, J. J ; Sharif University of Technology
Nature Publishing Group
2019
Abstract
The insect circulatory system contains an open hemocoel, in which the mechanism of hemolymph flow control is ambiguous. As a continuous fluidic structure, this cavity should exhibit pressure changes that propagate quickly. Narrow-waisted insects create sustained pressure differences across segments, but their constricted waist provides an evident mechanism for compartmentalization. Insects with no obvious constrictions between segments may be capable of functionally compartmentalizing the body, which could explain complex hemolymph flows. Here, we test the hypothesis of functional compartmentalization by measuring pressures in a beetle and recording abdominal movements. We found that the...
Linear index coding via graph homomorphism
, Article Proceedings - 2014 International Conference on Control, Decision and Information Technologies, CoDIT 2014 ; 2014 , pp. 158-163 ; ISBN: 9781479967735 ; Siavoshani, M. J ; Sharif University of Technology
2014
Abstract
In [1], [2] it is shown that the minimum broadcast rate of a linear index code over a finite field Fq is equal to an algebraic invariant of the underlying digraph, called minrankq. In [3], it is proved that for F2 and any positive integer k, minrankq(G) ≤ k if and only if there exists a homomorphism from the complement of the graph G to the complement of a particular undirected graph family called 'graph family {Gk}'. As observed in [2], by combining these two results one can relate the linear index coding problem of undirected graphs to the graph homomorphism problem. In [4], a direct connection between linear index coding problem and graph homomorphism problem is introduced. In contrast to...
Emerging OCDMA communication systems and data networks [electronic resource]
, Article Journal of Optical Networking ; Volume 6, Issue 9, 1 September 2007, Pages 1138-1178 ; Sharif University Of Technology
Abstract
I present an in-depth review of the trends and the directions taken by researchers worldwide in optical code-division multiple-access (OCDMA) systems. I highlight those trends and features that I believe are essential to the successful introduction of various OCDMA techniques in communication systems and data networks in the near future. In particular I begin by giving a comprehensive review of the construction of optical orthogonal codes (OOCs). Specifically I discuss the recently developed algorithms that are based on matrix algebra, which simplify and enhance the efficiencies of algorithms in OOC generation. In communication systems studies I first focus on and discuss various OCDMA...
Network delay analysis of a (σ, ρ) - Regular traffic stream over multiple paths in a network of fair-queuing servers
, Article 2013 Iran Workshop on Communication and Information Theory ; May , 2013 , Page(s): 1 - 6 ; 9781467350235 (ISBN) ; Golestani, S. J ; Sharif University of Technology
2013
Abstract
In this paper, we analyze the worst-case delay performance of a network of fair queuing servers in case of multiple-paths between source-destination pairs. In order to develop worst-case delay analysis for the multiple-path scenario, two challenging events should be addressed: merging different sub-streams of a session as well as distributing a traffic stream among different paths (traffic partitioning). Specifically, we propose to merge incoming sub-streams of a session to a node according to a limited rate Fair Queuing (FQ) scheme. Although the merged stream is treated as a unity, this approach results in a guaranteed level of service to each sub-stream. In addition, an algorithm is...
Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon
, Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) ; Akbari, J ; Yan, J ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the...
Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon
, Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) ; Akbari, J ; Yan, J ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the...
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Comparative study on the microstructures and properties of wire+arc additively manufactured 5356 aluminium alloy with argon and nitrogen as the shielding gas
, Article Additive Manufacturing ; Volume 34 , August , 2020 ; Zhang, L. J ; Ning, J ; Wang, X ; Zhang, G. F ; Zhang, J. X ; Na, S. J ; Fatemeh, B ; Sharif University of Technology
Elsevier B. V
2020
Abstract
This research explored the influences of shielding gases on the appearance of weld beads and the microstructures and mechanical properties of thin-wall samples using conventional gas metal arc welding as the heat source by using 5356 aluminium alloy welding wire as the raw materials and nitrogen (N2) and argon (Ar) as the shielding gases. The results showed that under the same parameters and after mono-layer single-bead welding was performed using N2 as the shielding gas, the bead height was higher, the bead width was narrower, and the penetration depth was shallower. The grain size of the thin-wall sample protected by N2 was 43.5–47.8 % smaller than that obtained under Ar protection....
Solid products characterization in a multi-step mineralization process
, Article Chemical Engineering Journal ; Vol. 252 , 2014 , Pages 210-219 ; ISSN: 13858947 ; Shayegan, J ; Sharratt, P ; Yeo, T. Y ; Bu, J
2014
Abstract
In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was...