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bahmani--ahmad
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Understanding the occurrence of the surface turbulence in a nonpressurized bottom gating system: numerical simulation of the melt flow pattern
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 232, Issue 3 , March , 2018 , Pages 230-241 ; 14644207 (ISSN) ; Baghani, A ; Bahmani, A ; Tamizifar, M ; Davami, P ; Ostad Shabani, M ; Mazahery, A ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
Surface turbulence during the filling of the mold triggers the entrainment of oxide films, which appears to be detrimental to the soundness of the final casting. Nonpressurized and bottom-gating systems have been employed in order to avoid such casting defects by reducing the surface velocity of the liquid metal. However, recent studies have shown that the melt front velocity in the mold entrance may exceed the critical value in the nonpressurized and bottom-gating systems. Therefore, a study was conducted on numerical simulation melt flow pattern in nonpressurized and bottom-gating systems. It was noted that the liquid metal enters the gate and then mold cavity with a higher velocity by...
Gold nanorods for drug and gene delivery: An overview of recent advancements
, Article Pharmaceutics ; Volume 14, Issue 3 , 2022 ; 19994923 (ISSN) ; Mousazadeh, M ; Taji, S ; Bahmani, A ; Zarepour, A ; Zarrabi, A ; Sharifi, E ; Azimzadeh, M ; Sharif University of Technology
MDPI
2022
Abstract
Over the past few decades, gold nanomaterials have shown great promise in the field of nanotechnology, especially in medical and biological applications. They have become the most used nanomaterials in those fields due to their several advantageous. However, rod-shaped gold nanoparticles, or gold nanorods (GNRs), have some more unique physical, optical, and chemical properties, making them proper candidates for biomedical applications including drug/gene delivery, photothermal/photodynamic therapy, and theranostics. Most of their therapeutic applications are based on their ability for tunable heat generation upon exposure to near-infrared (NIR) radiation, which is helpful in both...
A self-similar approach to study nanofluid flow driven by a stretching curved sheet
, Article Symmetry ; Volume 14, Issue 10 , 2022 ; 20738994 (ISSN) ; Jamshed, W ; Ahmad, S ; Bashir, H ; Ahmad, S ; Tag El Din, E.S.M ; Sharif University of Technology
MDPI
2022
Abstract
Nano-fluids have considerable importance in the field of thermal development that relates to several industrial systems. There are some key applications in recent construction systems flow, as well as microscale cooling gadgets and microstructure electric gadgets for thermal migration. The current investigation concludes the study of electrically conducting nano-fluid flow and heat transfer analysis in two-dimensional boundary layer flow over a curved extending surface in the coexisting of magnetic field, heat generation and thermal radiation. The small sized particles of copper (Cu) are taken as nanoparticles and water is assumed to be the base fluid. We used quasi-linearization and central...
Thin Film Thickness Measurement Using Colors of Interference Fringes
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer
Effect of Amplitude of Electric Field on the Rotation of Liquid Film
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric...
Design and Build an Acoustic Tweezers and Move up the Polystyrene Particles
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
Ultrasound waves have attracted substantial attention due to their potential for trapping the small particles, which cannot be handled by usual tweezers. The acoustic tweezer is a technology that is able to tarp and control the movement of micrometer to millimeter objects by standing or focused sound waves. Acoustic tweezers are the subject of many researches around the world, due to simplicity, cost-effective, biocompatibility and most important better performance in non-transparent optical environments, compared with optical tweezers.In this project, by using a ring piezoelectric and a power amplifier, an acoustic tweezer was designed and constructed. Moreover, the polystyrene particles...
Thermal Relaxation Time Of Healthy and Cancerous Tissue In Pulsed Laser Using Monte Carlo Simulation
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
Thermal relaxation time is the time when maximum temperature of a particle get to 1/e of it’s initial value. The destruction of a tissue depends to this important parameter. This parameter has studied by Monte Carlo simulation of pulsed laser in to environment as healthy and cancerous tissue. The main goal of this method is providing proper temperature in a special area so that minimize thermal destruction around that area. In this thesis, temperature distribution of tissue that is caused by pulsed laser, has solved by new method;in this new method the pulse duration uses for Monte Carlo simulation. Also using the solution of radiation transfer equation by Discretes Ordinate Method, new...
Prediction of Agricultural Water Demand and Uncertainties Under Climate Change(Case Study: Wheat in Cities of Dezful and Andimeshk)
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
Climate change impacts especially on temperature and precipitation, may have various effects on agriculture and water demand of agriculture sector in different regions around the world. Based on numerous researches, these effects may be positive in a region while another region might endure negative effects. Therefore carrying out researches and developing methods to predict these impacts as well as mitigating strategies seem to be essential. The most worldwide accepted method is using global circulation models (GCMs) outputs under different greenhouse gases emission scenarios, and according to Intergovernmental Panel on Climate Change (IPCC) assessments. IPCC claims that the most recent...
Assessing the Ecological Potential of Tehran City Using Sustainable Urban Criteria
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
The citizens’ dissatisfaction with the decreased life and residential care quality is increasing as a result of the rapid growth and development of cities. To find an effective solution to reduce and control these harmful effects is one of the main concerns of urban managers and planners in most countries. In this research, various ecological and sustainability criteria were selected through library-based studies and relative recognition of the region. The Maps were mostly provided through satellite imagery and some by using synoptic data collected from the official aerology website of the country, Iran. Through surveying the experts, different criteria were evaluated and based on the...
Strain Analysis of Sheet Metal Forming Parts by Inverse Finite Element Method Considering the Tooling Effects
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
The purpose of this work is to introduce an inverse finite element tool for prediction of the blank geometry and forming severity in stamping of 3D sheet metal parts. To achieve this goal total deformation theory of plasticity has been employed. In this method the final 3D part is unfolded on the flat surface and therefore the problem is reduced to two dimensional computations. Some tooling effects including blank holder force, bending and unbending and effect of draw bead are also considered. To investigate the capability of this work, predictions of the blank shape and strain distribution and forming severity have been performed on two circular and square parts. The results have been...
Optimaztion of Distance Between Stations in Cold Roll Forming
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
Cold roll forming is a process for manufacturing of long sheet metal products with constant cross sections. The base of this process is bending and formation of plastic deformation in sheet. In this process, bending operation occurs in several forming stations. The purpose of this project is estimation of the distance between stations in roll forming. This work is based on determination of deformation length. In this study, first, the researches done in the roll forming is expressed. Then, a relation for estimation of deformation length has been derived that could be used in different stages of roll forming. Compared with other works, the work hardening effect has been considered in the...
An Analysis of Key Factors Contributing to Residential Property Valuation in Iran
,
M.Sc. Thesis
Sharif University of Technology
;
Sharbatoghlie, Ahmad
(Supervisor)
Abstract
It is our purpose in this study to compare and analyze behavioral aspects of residential property valuation in Iran. More specifically, this research aims to explore the attributes that influence the value of residential property from the consumers’ and valuers’ perspective to determine whether valuers account for consumer behavior accurately. Finally, we investigate which variables operate at the lower end of the market, as distinct from those influencing the value of higher priced property. The core methodology underpinning the measurement of buyer and valuer behavior is the use of survey analysis. The identification of variables employing a two stage process forms an initial but critical...
Study of Climate Change Impacts on Water Resources (Case Study: Karkheh River Basin)
,
M.Sc. Thesis
Sharif University of Technology
;
Abrishamchi, Ahmad
(Supervisor)
Abstract
Future of the Karkheh River Basin and its people’s livelihoods clearly depends on natural resources like water, soil, vegetation and livestock. As water is the most limiting natural resource in this basin, any increase in water productivity will almost certainly benefit rural livelihoods. To ensure the sustainability of the improvements in water productivity, assessment of the possible impacts of climate change on hydrology and water resources in the basin is necessary. In this study the potential impacts of climate change on hydrology in the Karkheh River Basin were assessed using a macroscale hydrology model driven by 21st century simulations of temperature and precipitation downscaled...
Forecasting Urban Groundwater Level Applying Geographical Information System (GIS) and Artificial Neural Network (ANN)
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
Groundwater beneath the cities is becoming an important and valuable resource. Conjunctive use of surface and groundwater is likely to become increasingly more common as urban population grows by time. Therefore, one important requirement for urban water management planning is forecasting the groundwater level fluctuations. Unfortunately less experience and information is available to evaluate the fluctuations of groundwater level in urban environment compare to the natural systems, also different processes (sources) are involved in an urban water cycle, which all together make it more complicated to study. Similar to many other megacities, there is a serious lack of hydrogeological and...
Study of Climate Change Impacts on Temporal and Spatially Varying Groundwater Recharge
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
Increase of concentration of CO2 and other greenhouse gases will have significant effect on global climate. Climate change affects precipitation and hydrology, which in turn influences recharge to groundwater. Recharge to groundwater is an important source, which has the main role in groundwater resources availability. To trace these changes to recharges and its consequent effect on groundwater state, a combined modeling of climate change and groundwater is necessary. In This study impact of climate change on groundwater recharge in two different climatic plains of Karkheh river basin in Khuzestan, Iran, has been investigated using a physically-based methodology that can be used for...
Regional Hydrologic Models in Basins(Case Study: Monthly Flow in Urmia Lake Basin)
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
One of the very common models for hydrologic cycle modeling is water balance model which is used widely in water resource management. In these models, precipitation is used as input of the model and runoff is used as output of the model. The main purpose of this thesis is usage of a procedure that could have in mind the complicated climate changes and predict the stream flow. This method which is named regionalization connects the gauged stations and ungauged station. Linear regression and regional calibration are two methods which are used in this research and water balance model is calibrated for ten subcatchments of Urmia lake and three subcatchments are used for verification of the...
, M.Sc. Thesis Sharif University of Technology ; Asempour, Ahmad (Supervisor)
Abstract
In this research two stage deep drawing has been analyzed by the upper bound method. During this study, the deep drawings of cylindrical parts have been analyzed. In this method, for the first stage the whole deformation region is divided into five zones including punch bottom, punch radius, between punch and die, die radius and flange. Then, the geometric equations of each zones is generated by sweeping the section curves defined on the boundary of each zone. The velocity fields are expressed in a similar manner by sweeping the boundary velocity functions. At each stage, with the change of height between punch and die, the point location is changed and movement and tension in the sheet are...
Urban Water Demand Forecasting with Dynamic Artificial Neural Networks
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
The water demand forecasting is an important activity for successful planning, utilization and operation of urban water supply and distribution systems. The population growth result in water consumption growth, also the restriction of water resources lead to pay more attention to the water demand management. The unexpected droughts, financial crises, over-use of water resources, or inessential infrastructure development are the outcome of poor water demand prediction and inflexible water resource management. This research is addressed the daily short-term (two week ahead), weekly medium-term (six months ahead), and monthly long-term (two years ahead) water demand. The dynamic artificial...
Development of Regional Rainfall-Runoff Models
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
Hydrological models are suitable tools for reduction of hydrological uncertainty in stream flow estimation. There are different historical approaches for the development of rainfall-runoff models, with regard to the choice of model structure and the calibration of the parameters, but the most attention has been focused on gauged catchments where sufficient data, in particular stream flow data, are available. So new modeling strategies for ungauged or pseudo ungauged catchments have been developed. This work was aimed to develop a methodology for the regionalization of some parameters of a conceptual rainfall-runoff model based on measurable physiographic, meteorological and even land...
Initial Blank Design of Deep Drawn Single Layer Composite parts Using Inverse Finite Element Method
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
The inverse finite element method was derived from ideal forming to predict the development blank of sheet forming process and the strain distribution according to the geometry of final product. In this project we present an inverse finite element method to obtain strain and stress distribution in final shape and design initial blank of deep drawing process. The procedure is as follows: First, strain distribution in deep drawn part is estimated by kinematics. Then by using Hill’s anisotropic plasticity and according to the associated plastic flow rule, stress distribution is obtained in deep drawn orthotropic part.Finally, initial blank is designed by considering external forces between...
The inverse finite element method was derived from ideal forming to predict the development blank of sheet forming process and the strain distribution according to the geometry of final product. In this project we present an inverse finite element method to obtain strain and stress distribution in final shape and design initial blank of deep drawing process. The procedure is as follows: First, strain distribution in deep drawn part is estimated by kinematics. Then by using Hill’s anisotropic plasticity and according to the associated plastic flow rule, stress distribution is obtained in deep drawn orthotropic part.Finally, initial blank is designed by considering external forces between...