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Tip geometry effects in surface characterization with amplitude modulation AFM
, Article Scientia Iranica ; Volume 17, Issue 1 F , 2010 , Pages 27-34 ; 10263098 (ISSN) ; Meghdari, A ; Sharif University of Technology
Abstract
In the present work, characterization of the surface trenches and vacancies with Amplitude Modulation AFM (AM-AFM) using Molecular Dynamics (MD) is simulated and the effects of the tip shape on the resulting images are investigated. The simulated system includes a recently developed gold coated AFM probe which interacts with a sample including a surface trench or a single-atom vacancy. In order to examine the behavior of the above system, including different transition metals, a Molecular Dynamics (MD) simulation with Sutton-Chen (SC) interatomic potential is used. Special attention is dedicated to the study of tip geometry effects such as the tip apex radius, the tip cone angle, the probe...
Packing of nonoverlapping cubic particles: Computational algorithms and microstructural characteristics
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 94, Issue 6 , 2016 ; 15393755 (ISSN) ; Sahimi, M ; Rahimi Tabar, M. R ; Sharif University of Technology
American Physical Society
Abstract
Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir, Sci....
An improvement of thermodynamic micellization model for prediction of asphaltene precipitation during gas injection in heavy crude
, Article Fluid Phase Equilibria ; Volume 308, Issue 1-2 , September , 2011 , Pages 153-163 ; 03783812 (ISSN) ; Masihi, M ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
Abstract
Thermodynamic micellization model is known as an appropriate approach for prediction of asphaltene precipitation. However, the reliability (i.e. accuracy) of this model for whole range of pressure or injected gas mole percent must be checked. In practice, the accuracy can be improved by using a suitable characterization method. In this research, a computer code for implementing the thermodynamic micellization model has been developed. Having used this program, we make the prediction of asphaltene precipitation by using data reported in the literature as well as the experimental data obtained from high pressure, high temperature asphaltene precipitation experiments under gas injection...
Facile synthesis of cauliflower-like hydrophobically modified polyacrylamide nanospheres by aerosol-photopolymerization
, Article European Polymer Journal ; Volume 83 , 2016 , Pages 323-336 ; 00143057 (ISSN) ; Ramazani, S. A. A ; Ahadian, M. M ; Tamsilian, Y ; Weber, A. P ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Amphiphilic copolymers consist of hydrophilic and hydrophobic monomer units have attracted great technological attention recently, owing to their unique properties and their ability to stabilize various interfaces in aqueous systems. This paper presents a novel and facile approach to produce spherical polyacrylamide, polystyrene and hydrophobically modified polyacrylamide (HM-PAM), as one of the most important type of amphiphilic copolymers, using a continuous aerosol-photopolymerization for the first time. To this end, the monomer droplets were generated by an atomizer, then photopolymerization was initiated ‘‘in flight’’ by ultraviolet (UV) irradiation of the aerosol monomer droplets...
Fabrication and characterization of maleic anhydride grafted polypropylene membranes with high antifouling properties
, Article Journal of Applied Polymer Science ; Volume 133, Issue 36 , 2016 ; 00218995 (ISSN) ; Mousavi, S. A ; Farhadi, F ; Sharif University of Technology
John Wiley and Sons Inc
2016
Abstract
In this study, maleic anhydride grafted polypropylene microporous flat-sheet membranes were prepared via a thermally induced phase separation method with a mixture of dibutyl phthalate and dioctyl phthalate as a diluent. The effects of the polymer composition and coagulation bath temperature on the morphology and performance of the fabricated membranes were investigated. The hydrophilicity results of the membranes demonstrated that membrane modification reduced the water contact angle by about 45°, whereas the pure water flux was enhanced about four times. The antifouling behavior of the fabricated membranes was also investigated in a membrane bioreactor. The results show that the pure water...
Fabrication, characterization and mechanical properties of hybrid composites of copper using the nanoparticulates of SiC and carbon nanotubes
, Article Materials Science and Engineering A ; Volume 572 , 2013 , Pages 83-90 ; 09215093 (ISSN) ; Salahi, E ; Alikhani Hesari, F ; Simchi, A ; Kim, H. S ; Sharif University of Technology
Abstract
Copper based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were fabricated via mechanical milling followed by hot pressing technique. Microstructures of the powders and consolidated materials were studied using scanning electron microscope, X-ray diffraction, Raman spectroscopy, and scanning transmission electron microscope. Microstructural characterization of the materials revealed that the addition of nanosized silicon carbide reinforcement lowered the grain growth rate and enhanced the homogenization during mechanical milling. Microhardness measurements and compression test showed considerable improvements in mechanical...
The highly sensitive impedimetric biosensor in label free approach for hepatitis B virus DNA detection based on tellurium doped ZnO nanowires
, Article Applied Physics A: Materials Science and Processing ; Volume 125, Issue 9 , 2019 ; 09478396 (ISSN) ; Teimouri, M ; Jafari Marandi, S ; Shariati, M ; Sharif University of Technology
Springer Verlag
2019
Abstract
The highly sensitive impedimetric biosensor in label free approach for hepatitis B virus DNA (HPV DNA) detection based on tellurium doped ZnO nanowires was fabricated. The NWs were grown by hybrid thin film oxidation in the physical vapor deposition (PVD) mechanism. The morphology characterization of the synthesized NWs was performed by field emission scanning electron microscopy (FESEM) and the images demonstrated that the diameter and the length of the materialized NWs were around 50 nm and several micrometers, respectively. The high-resolution transmission electron microscopy (HRTEM) image indicated that the fabricated NWs were crystalline and their phase characterization was validated by...
A novel procedure for micromechanical characterization of white matter constituents at various strain rates
, Article Scientia Iranica ; Volume 27, Issue 2 , 2021 , Pages 784-794 ; 10263098 (ISSN) ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
Optimal hyperplastic coeficients of the micromechanical constituents of the human brain stem were investigated. An evolutionary optimization algorithm was combined with a Finite Element (FE) model of a Representative Volume Element (RVE) to nd the optimal material properties of axon and Extra Cellular Matrix (ECM). The tension and compression test results of a previously published experiment were used for optimizing the material coeficients, and the shear experiment was used for the validation of the resulting constitutive model. The optimization algorithm was used to search for optimal shear moduli and ber sti ness of axon and ECM by tting the average stress in the axonal direction with the...
Performance evaluation and improvement of PC-SAFT equation of state for the asphaltene precipitation modeling during mixing with various fluid types
, Article Fluid Phase Equilibria ; Volume 554 , 2022 ; 03783812 (ISSN) ; Jamshidi, S ; Sharif University of Technology
Elsevier B.V
2022
Abstract
One of the significant problems of the upstream flow assurance community is precipitation or deposition of asphaltene that leads to affect the economics of oil production seriously. Knowledge of asphaltene onset pressure (AOP) and amount of asphaltene precipitation in the change of temperature, pressure, and composition is the essential information for preventing this problem. Recent studies have shown that thermodynamic models based on the solubility nature of asphaltenes using an equation of state (EOS) are the most effective approach to asphaltene behavior modeling. In this research, the common version of the SAFT equation, known as the Perturbed Chain form of Statistical Association...
Synthesis and characterization of a chitosan/gelatin transparent film crosslinked with a combination of EDC/NHS for corneal epithelial cell culture scaffold with potential application in cornea implantation
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 71, Issue 8 , 2022 , Pages 568-578 ; 00914037 (ISSN) ; Ramazani S. A, A ; Mehraji, S ; Eslami, H ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
The diseases and disorders of the cornea may lead to blindness, and cornea transplantation has been an effective treatment in this regard. However, lack of cornea throughout the world makes this treatment difficult. Therefore, the first goal of the present study is to make a chitosan/gelatin hyaline film with NHS and EDC crosslinkers for transplanting the epithelial cells of the cornea. Two solutions of gelatin and chitosan were mixed homogeneously before crosslinking in ratios of 20/80, 30/70, 40/60, and 50/50 (Gel/Chi). After 24 hours, they were put in an oven to dry, then EDC and NHS were added to the mixture as crosslinker. Corneal epithelial cell morphology was assessed qualitatively...
Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations
, Article Materials Characterization ; Volume 101 , March , 2015 , Pages 189-207 ; 10445803 (ISSN) ; Behnamian, Y ; Mostafaei, A ; Izadi, H ; Saeid, T ; Kokabi, A. H ; Gerlich, A. P ; Sharif University of Technology
Elsevier Inc
2015
Abstract
Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560-1400 r/min and 16-40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS)...
Reservoir Characterization and Parameter Estimation Using Ensemble Kalman Filter
, M.Sc. Thesis Sharif University of Technology ; Pishvaei, Mahmood Reza (Supervisor) ; Bozorgmehri Boozarjmehri, Ramin (Supervisor)
Abstract
Management decisions, enhanced oil recovery, and reservoir development plans in petroleum industries are based on predictions by reservoir simulation. Due to uncertainties in model parameters or engineering assumptions, the simulation results are not accurate, while they are correct. For more accurate estimation of unknown production quantities, it is required to characterize the unknown parameters and its uncertainty. By using static data alone the result of characterization is unreliable and unsure, therefore dynamic data use practically. In reservoir engineering literature, this is called “History Matching”.The ensemble Kalman filter is an optimal recursive data processing algorithm based...
Enhancing Performance of Replacement Policy in Operating System Page Cache for I/O Intensive Workloads
, M.Sc. Thesis Sharif University of Technology ; Asadi, Hossein (Supervisor)
Abstract
Due to the increasing use of data storage systems and volume of digital data, fast information access and retrieval has significant effect on performance of storage-bound systems. Operating systems utilize the spare space in the main memory as a cache to speed up access to the storage subsystem. Due to the large performance gap between hard disk and main memory, any improvement in this caching layer can greatly affect the performance of the entire system. Page replacement algorithms are one of the important mechanisms in the virtual memory management layer. Several algorithms have been proposed for the eviction of pages from the virtual memory cache and few of them have also been implemented...
Noise Characterization in VVER-1000 Reactor Core
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Neutron fluctuations in both low and high power reactors provide important information about the system. The origins of these fluctuations are different in both regimes. In low power the branching process is the reason of these fluctuations. But the random nature of technological processes such as boiling in the reactors cooling and mechanical structure vibrating such as control rod and fuel rod created the neutron noise. Mathematical descriptions and applications of neutron noise for each mode are different. In common mode, fluctuations in the neutron detection system, determine some parameters and determin the start abnormality in system. In this study the spatial dependence of the cross...
Elemental Characterization of the Total Suspended Particulate Matter of the Industrial City of Arak with NAA and AAS and Modeling with the AERMOD Software
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor)
Abstract
Environmental conditions of various cities of Iran are deteriorating due to various contributing effects of increased traffic, deforestation, industrial pollution etc. Arak is an example in point. It is a city of about 440,000 inhabitants. It is located at the edge of the main central desert (Kavir) of Iran. It lacks any appreciable vegetation or wooded areas and it is the home of a number of major industries. These include aluminum smelting, petrochemical industry, refinery, power plant and various other heavy manufacturing facilities. It was suggested to perform an air sampling of the city for a whole year (2010-2011) to determine the concentration of various elements by instrumental...
Characterization of Naturally Fractured Reservoirs Using Intelligent Integration of Diverse Data Sources
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor) ; Masihi, Mohsen (Supervisor)
Abstract
Naturally fractured reservoirs are essentially very complicated; therefore we need a systematic and reliable characterization process in order to model, analyze displacement phenomena, simulate, develop, and schedule production and other engineering processes. These kinds of reservoirs have multi-scale asymmetry while there is no specific tool to fully characterize them, and on the other hand the field data (including stratigraphy, core study, well testing and seismology) have different resolutions and accuracies, though their significant role to investigate naturally fractured reservoirs. The objective of this project is to investigate the different data sources and present their...
Investigation on Wettability Alteration of Reservoir Rocks by Functionalized Silica Nanoparticles using Molecular Dynamics Simulations
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Aliasghar (Supervisor) ; Seyfkordi, Aliakbar (Supervisor)
Abstract
The properties of 3 nm-diameter fluorinated silica nanoparticles with different coverage percent of CF3 groups as water and oil repellents were investigated at the water-rock and decane-rock interface using molecular dynamics simulation. Simulating a pore of rock in presence of water and decane molecules separately, resulted in liquid bridging for both of liquids. The density profiles of liquids in the pore clearly show several highly ordered layers packing of the molecules close to the rock surface. Distribution of liquid molecules around the nanoparticles is much influenced with increasing CF3 groups on the nanoparticle surface. Results show that adsorption of functionalized silica...
(MCNP Simulation of Online Elemental Analyzer in the Cement Manufacturing Poroces by Prompt Gamma Neutron Activation Analysis (PGNAA
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor)
Abstract
Method of Prompt Gamma Neutron Activation Analysis (PGNAA) is useful for controlling some massive production processes such as cement industry and mineral materials. Difficulty of other methods of analysis such as XRF comparing with PGNAA is that mass of sample is small and it doesn’t determine heterogeneity of mixture. On the other hand, need to sampling is also another problem of these analysis methods because sampling is terminated and it doesn’t supervise on production continuously, in fact its quality can’t be revealed simultaneously and there is a long time between sampling and control of process. Usually, analysis methods such as XRF are useful for processes that are controlled...
Improving Cache Performance of Data Storage Systems Using Machine Learning
, M.Sc. Thesis Sharif University of Technology ; Asadi, Hossein (Supervisor)
Abstract
Emerging Solid State Drives (SSDs) have performance advantages over traditional Hard Disk Drives (HDDs). Higher price per capacity and limited lifetime, however, prevents enterprise data centers to entirely replace HDD-based storage subsystems with SSDs. Thus,SSD-based caching has been widely employed in data centers to benefit from higher performance of SSDs while minimizing overall cost. Input/Output (I/O) workloads exhibit unpredictable and highly random behavior which makes conventional algorithms such as Least Recently Used (LRU) not able to provide high hit ratio as they employ linear localities.In addition to poor performance, such algorithms also shorten SSD lifetime with unnecessary...
Analysis and Characterization of Near Field Behavior of Plasmonic Nanostructures
, Ph.D. Dissertation Sharif University of Technology ; Rashidian, Bizhan (Supervisor)
Abstract
Despite ongoing progress in the field of nanophotonics, characterizing and identifying optical interactions in the deep subwavelength dimensions have remained challenging. The inability of conventional optical microscopy in nanoscale imaging, due to diffraction limit, was the main stimulus for research on new characterizing methods with the capability of non-destructive high-resolution imaging in which the sample preparation is not required. To achieve this goal, scanning probe microscopes are introduced to extract valuable high spatial harmonics from near field measurements on the sample. In this thesis, by focusing on the probe-sample interaction, the near field behavior of the plasmonic...