Loading...
Search for:
ashrafi--abolfazl
0.126 seconds
Total 172 records
Droplet condensation on chemically homogeneous and heterogeneous surfaces
, Article Journal of Applied Physics ; Volume 120, Issue 12 , 2016 ; 00218979 (ISSN) ; Moosavi, A ; Sharif University of Technology
American Institute of Physics Inc
2016
Abstract
Nucleation and growth of condensing droplets on horizontal surfaces are investigated via a 2-D double distribution function thermal lattice Boltzmann method. First, condensation on completely uniform surface is investigated and different mechanisms which cause dropwise and filmwise condensation are studied. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. In the second step, condensation on chemically heterogeneous surfaces is investigated. Moreover, the effect of non-uniformity in the surface temperature is also studied. The results indicate that the vapor layer instability and the nucleation start from the heterogeneities....
Biomass Separation in Moving Bed Biofilm Reactors (MBBR) by Natural And Innovative Filters
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Mahdi (Supervisor)
Abstract
The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the...
Continuous-thrust Trajectory Optimization in the Binary Asteroids System
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
In this thesis, the optimal trajectories of a spacecraft in the binary asteroids system is studied. The objective functions of optimal trajectories in these system are the maximum coverage of the asteroids surface and minimum time and fuel consumption. For this purpose, the dynamic of binary system is modeled. The binary system of 1999 KW4 is selected as a case study. The ellipsoid-sphere model is a good approximation for the case of this study. In this model, the asteroids orbit in a circular orbit around each other in a spin-spin-orbit resonance configuration, in which the asteroids’ rotational velocity is equal to orbital mean motion. Then, the equations of motion of the spacecraft as the...
New correlation for calculating natural gas Z-factor
, Article Hydrocarbon Processing ; Volume 89, Issue 10 , 2010 ; 00188190 (ISSN) ; Ghotbi, C ; Sharif University of Technology
2010
Droplet condensation and jumping on structured superhydrophobic surfaces
, Article International Journal of Heat and Mass Transfer ; Volume 134 , 2019 , Pages 680-693 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θa=90°,120°,155° is...
An Investigation on the Behavior of Bolted Connections using Friction Drilling in Shear and Tension
, M.Sc. Thesis Sharif University of Technology ; Ahmadizadeh, Mehdi (Supervisor)
Abstract
Friction drilling or flow drilling is a method of making holes in metal sheets, in which the material is pushed with the aid of heat from friction. This procedure allows making holes in sheet metal, with a sleeve formed as the hole is created. This sleeve is then threaded and used as the nut, thus eliminating the need for access to the interior faces of hollow steel sections. On the other hand, with the development of advanced manufacturing techniques, larger and thicker hollow structural sections are becoming more popular in mid-rise and multistory structures. onsequently, flow drilling can be considered as a viable alternative for traditional drilling techniques, where the material is...
A novel management scheme to reduce emission produced by power plants and plug-in hybrid electric vehicles in a smart microgrid
, Article International Journal of Environmental Science and Technology ; Volume 17, Issue 5 , 2020 , Pages 2529-2544 ; Soleymani, S ; Mehdi, E ; Sharif University of Technology
Springer
2020
Abstract
Recently, with the growth and development of distributed generation (DGs) and energy storage systems (ESSs), as well as smart control equipment, microgrids (MGs) have been developed. Microgrids are comprised of a limited number of constitutive parts, including loads, DGs, ESSs, and electric vehicles (EVs). This paper presents a novel scheme to manage active and reactive powers, based on DGs, ESSs, and EVs to reduce the total operation cost including power generation and emission costs. Simultaneous management of active and reactive power makes it possible to consider grid operation constraints together. In the proposed schedule, the vehicles are assumed to be plug-in hybrid electric...
Recycling of Cobalt with the form of Cobalt Nano Oxide from Spent Li-ion Batteries
, M.Sc. Thesis Sharif University of Technology ; Askari, Masoud (Supervisor)
Abstract
One of the most important methods for recycling of spent Li-ion batteries is acid leaching that various parameters affect it. In this work, influences of effective parameters on the percent of cobalt and lithium recovery with application of design of experiments (response surface methodology-central composite) were investigated and then cobalt nano oxide as the by-product synthesized by pulsing lectrolysis. In the first Phase, effects of parameters such as sulfuric acid oncentration: 2-6 molar, hydrogen peroxide volume percent: 5-10%, S/L ratio: 20-50 g/L and temperature: 50-80°C on cobalt and lithium recovery were investigated and finally an adequate model presented. For all experiments,...
Two-dimensional modeling of functionally graded viscoelastic materials using a boundary element approach
, Article Advanced Materials Research, 7 January 2012 through 8 January 2012 ; Volume 463-464 , January , 2012 , Pages 570-574 ; 10226680 (ISSN) ; 9783037853634 (ISBN) ; Bahadori, M. R ; Shariyat, M ; Sharif University of Technology
2012
Abstract
In this paper, a 2D boundary element approach able to model viscoelastic functionally graded materials (FGM) is presented. A numerical implementation of the Somigliana identity for displacements is developed to solve 2D problems of exponentially graded elasticity. An FGM is an advanced material in which its composition changes gradually resulting in a corresponding change in properties of the material. The FGM concept can be applied to various materials for structural and functional uses. Our model needs only the Green's function of nonhomogeneous elastostatic problems with material properties that vary continuously along a given dimension. We consider the material properties to be an...
Modeling of viscoelastic solid polymers using a boundary element formulation with considering a body load
, Article Advanced Materials Research, 7 January 2012 through 8 January 2012 ; Volume 463-464 , January , 2012 , Pages 499-504 ; 10226680 (ISSN) ; 9783037853634 (ISBN) ; Bahadori, M. R ; Shariyat, M ; Sharif University of Technology
2012
Abstract
In this work, a boundary element formulation for 2D linear viscoelastic solid polymers subjected to body force of gravity has been presented. Structural analysis of solid polymers is one of the most important subjects in advanced engineering structures. From basic assumptions of the viscoelastic constitutive equations and the weighted residual techniques, a simple but effective boundary element formulation is implemented for standard linear solid (SLS) model. The SLS model provides an approximate representation of observed behavior of a real advanced polymer in its viscoelastic range. This approach avoids the use of relaxation functions and mathematical transformations, and it is able to...
A new low voltage, high PSRR, CMOS bandgap voltage reference
, Article 2008 IEEE International SOC Conference, SOCC, Newport Beach, CA, 17 September 2008 through 20 September 2008 ; 2008 , Pages 345-348 ; 9781424425969 (ISBN) ; Atarodi, M ; Chahardori, M ; Sharif University of Technology
2008
Abstract
A new low voltage bandgap reference (BGR) in CMOS technology, with high power supply rejection ratio (PSRR) is presented. The proposed circuit uses a regulated current mode structure and some feedback loops to reach a low voltage, low power and high PSRR voltage reference. The circuit was designed and simulated in 0.18um CMOS technology, with a power supply of 1.4 volt. The results show PSRR is 65dB at 1MHz and the output voltage variation versus temperature (-40 to 140) is less than 0.1%. This circuit shows robustness against process variation. ©2008 IEEE
Numerical Investigation of Formation and Growth of Steam Condensing Droplets on Nanostructured Superhydrophobic Surface Using Lattice Boltzmann Method
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Condensation is one of the main processes in environment and engineering systems, including thermal power plants, desalination systems and air conditioners. Thus, improvement of its performance can lead to decrease of energy consumption and the resulting air pollutions. Recently, using nanotechnology and new coating methods, there have been great researches on stable superhydrophobic surfaces and using theme as condensing surfaces which because of jumping droplet phenomena can increase condensation performance. Because of the great influence of wetting and structure properties of surfaces on condensation, in this study nucleation and growth of condensing droplets on smooth and structured...
Proposing an Appropriate Lateral Load Pattern for Push-over Analysis of Steel Moment Resisting Frame Structures with Mass Irregularity in Height
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
The irregularity in structures is divided into two categories of irregularity in vertical and irregularity in plan. The irregularity in vertical can be caused by ultra-change in dynamic properties of the structure such as mass, stiffness or strength. Research studies indicate that this irregularity leads to intensify the applied damages to structures in severe earthquakes. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). That is due to consideration of higher modes effects and the shifts in inertia load pattern as the structural system experiences nonlinear behavior. Nowadays, due to complexity of nonlinear dynamic...
Numerical Study of Geotextile Application in Downstream Filter Zone of an Embankment Dam with Clay Core
, M.Sc. Thesis Sharif University of Technology ; Shamsaie, Abolfazl (Supervisor)
Abstract
Nowadays, applications of the synthetic materials are developing in civil engineering projects and widely used in these projects. Therefore, during previous years; use of the Geotextiles as one of the Geosynthetic materials in order to filtration, drainage, separation, soil protection, etc have developed ever-increasing. The goal of this research is modeling and studies of the Geotextiles application in the downstream filter zone of embankment dams in combination with granular materials using FLAC2D software. Gordeh Bin embankment dam situated in West Azerbaijan province has been chosen as case study. In this matter, different models have been made with changes in thickness of the inclined...
groundwater level fluctuations forecasting using conjunction models of Wavelet - Neural-Fuzzy Network (WNF) and Wavelet-Neural Network (WNN) and linear model of ARIMA (case study: Qom plain
,
M.Sc. Thesis
Sharif University of Technology
;
Shamsaei, Abolfazl
(Supervisor)
Abstract
Prediction of groundwater level fluctuations is absolutely necessary for the proper manag ement of these precious resources. There are different methods to predict hydrological time series such as groundwater level. Linear models inefficiency in predicting nonlinear and n on-stationary time series cause researchers widely use artificial intelligence techniques such as Artificial Neural Networks (ANN), Fuzzy Inference System (FIS), Genetic Algorithm (GA) and their hybrid models such as Artificial Neural – Fuzzy Inference System (ANFIS). These smart models are capable to simulate nonlinear and non-stationary time series in suitable accu-racy using by a few time and data. By emersion of Wavelet...
, M.Sc. Thesis Sharif University of Technology ; Shamsaei, Abolfazl (Supervisor)
Abstract
Entrance of air to close water conduits occurs in many ways. This phenomenon makes displeasing effects on water transport structures. Two-phase flows in closed conduits are studied experimentally, numerically and theoretically. Even after decades, due to the complexity of the subject, these studies still require development and reformation. Numerical and theoretical two-phase models are often limited to a special regime of flow."Volume Of Fluid"(VOF) is a model for non-mixing two-phase flows. "Fluent" software uses this model in this field of flows. Volume of fluid is used successfully in some problems like dam break or rising bubbles. Main disadvantage of this model is distribution of the...
Assessment of waterlogging and provide risk maps by using RS, GIS and field data (case study: Qazvin plain)
,
M.Sc. Thesis
Sharif University of Technology
;
Shamsaei, Abolfazl
(Supervisor)
Abstract
Groundwater quality protection has a significant importance due to abundant applications of these resources in various fields such as agriculture, industry and drinking water. Removal of groundwater pollution is a time and money consuming process and often pollution is detected when improving the quality of groundwater is nearly impossible. For this vulnerability assessment there are three methods: Processing, Overlap-Index and Statistical Methods. Overlap-Index is composed of variety of maps such as Geology, Soil, Groundwater Depth and etc which uses in determining of vulnerability Index. In the present study for underground pollution potential determining, four indexes such as AVI، GOD،...
Efficient Management of River Water Quality Based on Pollution Trading Approach
, Ph.D. Dissertation Sharif University of Technology ; Shamsai, Abolfazl (Supervisor)
Abstract
“Sustainable development” is a frequently used phrase, but the idiom has been experienced little since it was coined by the Brundtland, due to its intrinsic complications. The issue is going to compromise two key components; economy and ecology. One of the solutions based on concept of sustainable development that has been proposed for maintaining water quality at acceptable levels is to cap pollutant emissions at a sustainable level, then establish an economic market in which the right to discharge pollutants is traded according to market supply and demand mechanisms. Water quality trading or pollution trading is one such kind of market-based program that has also been described using names...
Semi-supervised Breast Cancer Subtype Clustering Using Microarray Datasets
, M.Sc. Thesis Sharif University of Technology ; Motahhari, Abolfazl (Supervisor)
Abstract
Gene expression microarrays can be used for precision medicine and targeted therapies. The data generated by microarrays are high-dimensional causing statistical inference of any parameter a daunting task. In this thesis, it is shown that regardless of high-dimensional datasets produced by microarrays, the inference can be robust in the sense that random selection of features results in the same conclusion as far as the number of selected features are chosen appropriately. Stratifying patients with breast cancer based on their gene expression levels shows that patient subtypes are almost independent of the feature selection strategy. Moreover, using less noisy datasets coming from RNAseq...
A Simulation for Better Understanding of Integrin Clustering and Activation
, M.Sc. Thesis Sharif University of Technology ; Motahhari, Abolfazl (Supervisor)
Abstract
Today, computer simulations are employed prevalently by researchers to understand biological processes. The tendency to use computational methods has been increased recently due to the high costs and errors of experimental methods. Integrins are membrane proteins that mechanically attach cells to the extra cellular matrix (ECM) and derive some behaviors such as cell migration. Moreover, integrins have biochemical functions. They transduce environment signals and trigger chemical pathways. As a result, integrins regulate cell shape, motility, etc. The investigation of integrin behavior in a real environment is very difficult due to the presence of many other proteins that interfere with the...