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hemati--mahmood
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Improve the Structure of Membrane Bioreactor to Reduce Fouling for Industrial Waste Water Purification
, M.Sc. Thesis Sharif University of Technology ; Seifkordi, Ali Akbar (Supervisor) ; Hemati, Mahmood (Co-Advisor)
Abstract
In the presence project by using of hydrophilic polymer, Cellulose acetate (CA), we tried to modify the membrane made of Polyvinylidine fluoride (PVDF). The membranes were made by phase inversion method. In five levels, at least 10% and at most 30%, CA was added to casting solution. The hydrophilicity of membranes’ surface and pore size was increased. The permeation of the neat membrane of PVDF was less than 10 , on the other hand the permeation of the membranes, which were made by adding CA, was increased up to 500 . The increment of CA more than 20% reduced the porosity of membrane. In the next step to reduce the irreversibility fouling tried to reduce the pore size by adding some...
Water allocation using game theory under climate change impact (Case study: Zarinehrood)
, Article Journal of Water and Climate Change ; Volume 12, Issue 3 , 2021 , Pages 759-771 ; 20402244 (ISSN) ; Abrishamchi, A ; Sharif University of Technology
IWA Publishing
2021
Abstract
The combined effects of climate change and growing water demand due to population growth, industrial and agricultural developments cause an increase in water scarcity and the subsequent environmental crisis in river basins, which results in conflicts over the property rights and allocation agreements. Thus, an integrated, sustainable and efficient water allocation considering changes in water resources due to climate change and change of users’ demands is necessary. In this study, the drainage basin of Zarinehrood was chosen to evaluate the function of selective methods. Assessing climate change impact scenarios of the Fifth IPCC reports, e.g., RCP2.6, RCP4.5, RCP6.0 and RCP8.5, have been...
General Review of the Gamma Irradiators for the Purpose of Desing Improvement of Multipurpose Systems
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor)
Abstract
Ionizing radiation can modify physical, chemical and biological properties of the irradiated materials. At present, the principal industrial applications of radiation are sterilization of health care products including pharmaceuticals, irradiation of food and agriculture products and materials modification. In the above application the wide range of the required doses together with different product densities require spatial mechanical design of the irradiators to be able to properly handle the specified tasks. In the multipurpose irradiators the design of system and positioning of the source must be done in such a way that a nearly optimum dose distaition in the product boxes in...
An analytical investigation of elastic-plastic deformation of FGM hollow rotors under a high centrifugal effect
, Article International Journal of Mechanical and Materials Engineering ; Volume 14, Issue 1 , 2019 ; 18230334 (ISSN) ; Aghajani, S ; Hemati, M ; Sharif University of Technology
Springer
2019
Abstract
Functionally graded material shafts are the main part of many modern rotary machines such as turbines and electric motors. The purpose of this study is to present an analytical solution of the elastic-plastic deformation of functionally graded material hollow rotor under a high centrifugal effect and finally determine the maximum allowed angular velocity of a hollow functionally graded material rotating shaft. Introducing non-dimensional parameters, the equilibrium equation has been analytically solved. The results for variable material properties are compared with the homogeneous rotor and the case in which Young’s modulus is the only variable while density and yield stress are considered...
Optimal Design of Tolerances in the Non-rigid Assemblies under the Thermal Impact
, M.Sc. Thesis Sharif University of Technology ; Khodaygan, Saeed (Supervisor)
Abstract
Tolerance allocation in the recent mechanical assembly is significant because it straightly affects product performance and cost. Loose tolerances may cause the quality defect while tight tolerances can increase the cost. Thermal effects and the temperature gradients are one of the factors that caused changes in the size and geometry of the components during the performance of mechanical assemblies. This thesis proposes a new approach for tolerance design considering the thermal effects, to achieve lower manufacturing cost and good product quality. Finite element analysis is used to determine the deformation of components in an assembly. The neural network is trained using experimental...
History Modeling in Conversational Question Answering
, M.Sc. Thesis Sharif University of Technology ; Beigy, Hamid (Supervisor)
Abstract
In this thesis, we propose a method for long document modeling to address the issue of handling lengthy documents. The results indicate that our method successfully improves the problem of independently modeling chunks that arise from long documents. Additionally, we present consistent training using history augmentation to enhance the representation of questions with a long history. Our experiments demonstrate that this proposed method increases the performance of the baseline model, particularly for questions with a long history. The long document modeling approach improves the baseline's performance by 2.1% based on the F1 criteria. Furthermore, the consistent training using history...
Conflict Resolution of water resources Allocation Using Game Theory under Climate Change Impact (Case Study: Zarinehrood basin)
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor) ; Tajrishi, Masoud (Co-Supervisor)
Abstract
Increasing water consumption via competitive demands has resulted in serious water conflicts and the subsequent environmental crisis in river basins. The combined effects of climate change on river flow and growing water demand due to population growth, industrial and agricultural developments cause an increase of water scarcity in many basins. This is one of the drivers of both noncompliance with water allocation agreements and conflicts over the property rights to river water. Conflicts often arise when different water users compete for a limited water supply. Thus an integrated, sustainable, efficient and fair water allocation considering changes in water resources due to climate change...
A bi-objective aggregate production planning problem with learning effect and machine deterioration: modeling and solution
, Article Computers and Operations Research ; Volume 91 , March , 2018 , Pages 21-36 ; 03050548 (ISSN) ; Akhavan Niaki, S. T ; Hemati, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The learning effects of the workers and machine deterioration in an aggregate production planning (APP) problem have not been taken into account in the literature yet. These factors affect the performance of any real-world production system and require attention. In this paper, a bi-objective optimization model is developed for an APP problem with labor learning effect and machine deterioration. The first objective of this model maximizes the profit by improving learning and reducing the failure cost of the system. The second objective function minimizes the costs associated with repairs and deterioration, which depend on the failure rate of the machines in the production periods. The aim of...
Improving Efficiency of Labyrinth Side Weirs Using Asymmetric Geometry
, M.Sc. Thesis Sharif University of Technology ; Borghei, Mahmood (Supervisor)
Abstract
One of the most important methods of controlling discharge in water industry which is widely used in irrigation, water distribution, waste-water engineering, drainage, flood control and other water related projects, is side weir. The hydraulic behavior of flow over side weir is spatially varied flow with decreasing discharge. Various investigators have related the weir discharge coefficient as a function of main channel upstream Froude number and the fraction of weir height to upstream depth . Performance of sharp crested side weirs with extended length (as labyrinth side weir with asymmetric geometry) has been studied in this thesis. The variables for this study are height of weir ,...
An Estimation Model for Computation and Control of Trajectory Coverage Error in Additive Manufacturing
, M.Sc. Thesis Sharif University of Technology ; Houshmand, Mahmood (Supervisor)
Abstract
During 1980s Additive Manufacturing technologies for the purpose of prototyping with fast and less expensive, under the name of Rapid Prototyping was invented. But nowadays under the vast progress made in this field, it possesses a notable place in different industries such as automobile manufacturing, aerospace, architecture, medicine and so on for part manufacturing. In all AM machines, the CAD model design part is manufactured by adding layered to each other. In this research, at first by explaining manufacturing process and current different technologies, the place of this manufacturing process in today and future industry, is analyzed. For discussing replacement of this method instead...
Analysis and Design of Nanoantenna Arrays
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
If the size of the conventional telecommunication antennas -that are widely used in transmitting broadcasted radio and TV messages- is reduced by a nanometer size these antennas can be used at optical frequencies. Dimensions of these optical nanoantennas -that made of nanoparticles with highly permittivity- can be smaller than half of the wavelength. Based on this capability, optical nanoantennas have some important applications such as optical communication, photovoltaic devices, non-classical light, and optical sensing. After studying on optical nanoantennas and their features, in this project, we present distinctions between optical NAs and MW antennas and then investigate about different...
Designing a New System for Proposing a Suitable Computer System for Customers Using Cloud Computing and Service Composition
, M.Sc. Thesis Sharif University of Technology ; Hushmand, Mahmood (Supervisor)
Abstract
Cloud computing has brought about many changes in the new business arena. These changes do not only include technological changes, but have penetrated the business models of many companies. For example, in recent years, many companies have migrated from their former systems to cloud computing for reasons such as easy and low-cost access to high-performance hardware and software systems, and to avoid maintenance and repair costs and security costs.Due to the economic conditions in recent years and the high cost of electronic items, the criterion of purchase price has become much more important than in the past among people when buying such goods. Now in the Iranian electronics market,...
Experimental Study of Pressure Fluctuation in Two Phase Slug Flow In a Tunnel with Rectangular Cross Section with an Expansion Transition and Horizontal Slope
, M.Sc. Thesis Sharif University of Technology ; Borghie, Mahmood (Supervisor)
Abstract
Air enterance in to flowing water is something that is commonly seen in the water conveyance systems. The mixture of Air and water that flow together create a kind of flow that is called two phase flow. This kind of flow is often seen in culverts and water conveyance systems. There are different flow patterns in two phase flow. Considering pressure fluctuation, pressure drop and pressure recovery, slug flow pattern is the most complicated pattern among all.
Sometimes a singularity is used in a tunnel; one of the singularities that are frequently used in water conveyance system is expansion transition. In this study an experimental setup is used to model two phase slug flow, which passes...
Sometimes a singularity is used in a tunnel; one of the singularities that are frequently used in water conveyance system is expansion transition. In this study an experimental setup is used to model two phase slug flow, which passes...
Controlling Local Scour Due to Hydraulic Jump Using Oblique Buried Plates
,
M.Sc. Thesis
Sharif University of Technology
;
Borghei, Mahmood
(Supervisor)
Abstract
Local scouring at the downstream of sluice gates in the erosive beds is one of the main concerns of hydraulic engineers because of the significant damage that it can cause to the hydraulic structures. It is important to control the local scour depth at downstream of hydraulic structures to ensure safety operation of these systems. Many researchers have conducted various studies to predict the maximum depth and diameter of scour hole and develop new methods in order to control this phenomenon. One way to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron length or decrease the effect of the...
Performance Analysis and Optimization of Optically Steered Arrayed Antennas with Gratings
, Ph.D. Dissertation Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
It is well known that arrays of antennas make it possible to steer the radiation pattern without steering a physical structure. For the past few decades this has been considered for many civil and military communication systems. Recently, ultra-short pulses are considered for high resolution radars and ultra-wideband communication systems. Systems with short pulses and large antenna arrays may benefit from high resolution in both temporal and spatial domains. But the implementation of the ultra-wideband feeding circuits for such antenna arrays is a hard job even with state of the art electronics. Optical technology has been applied, successfully, to a number of radio applications such as...
Laboratory Investigation For Unsymmetric Rectangular Weir
, M.Sc. Thesis Sharif University of Technology ; Borghei, Mahmood (Supervisor)
Abstract
Sharp crested weirs are one of the main and oldest means of measuring discharge in water conveyance systems. Many studies have been done on sharp rectangular weirs and have provided many relationships regarding the effect of geometric parameters and various factors on discharge coefficient of the weirs.In some places, due to existence of obstacles or barriers in the channel, it is impossible to create a symmetrical continuous weir some other cases,multiple or asymmetric weirs should be used, which is the main concept of this project.Since it seems unlikely that a purely mathematical model can review the impact of the multiplicity and asymmetry of these weirs without using empirical...
Optimization of Maximum Frequency and Power, Extraction of Parameter Data and Final Publication Design of High Power Microwave Pulse Generation Using nonlinear Transmission Line with the Periodic Structure of the Gas Switch
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
High-power (108 – 109 W) RF pulses with a carrier frequency of C band and a duration of several oscillation periods can be produced through direct energy conversion of a travelling high-voltage pulse with the use of nonlinear elements.
Nonlinear transmission lines consist either of lumped nonlinear elements and provide spatial dispersion of excited oscillations or of elements uniformly distributed on a certain line segment. The first type of NLTL’s can be referred to NLTL’s with spatial dispersion. The second type of NLTL’s is ensemble of nonlinear oscillators with a characteristic natural frequency and temporal dispersion. In the first case, the duration of electromagnetic pulses is...
Nonlinear transmission lines consist either of lumped nonlinear elements and provide spatial dispersion of excited oscillations or of elements uniformly distributed on a certain line segment. The first type of NLTL’s can be referred to NLTL’s with spatial dispersion. The second type of NLTL’s is ensemble of nonlinear oscillators with a characteristic natural frequency and temporal dispersion. In the first case, the duration of electromagnetic pulses is...
Analysis and Simulation of Micrometre-scale Silicon Electro-optic Modulators Based on Ring Resonators
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)Optimized Design of Switch Circuit and Receiver Antenna in the Field of Fifth Generation Telecommunications to Reduce the Fading Effect
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
The Deep Fading Effect is a destructive factor in communication systems, one of the solutions to eliminate it is the use of Diversity, and there are two types of indicators of Diversity, Spatial Diversity and Polarization Diversity. Spatial Diversity is a common method to reduce the Fading Effect while increasing the cost and increasing the volume of the communication station, which to optimize the cost and reduce the volume of the communication station, the Polarization Diversity Structure is added to the telecommunication system. To apply Spatial Diversity, several Antennas with different Polarizations are used, which The most common method in mobile telecommunication station systems is...
Design and Implementation of an Audio Steganography System on FPGA
, M.Sc. Thesis Sharif University of Technology ; Tabandeh, Mahmood (Supervisor)
Abstract
In recent years, along with development of technology and decrease in size of digital devices, copying and editing of digital multimedia products has become easier. Also, broadband technology caused simpler distribution of data. Considering above mentioned problems, we can use watermarking. Nowadays, watermarking has many applications such as secure transmission of data, owner identification, proof of ownership, authentication, broadcast monitoring etc. Watermarking is the process of hiding information in a secure host, in a way that it does not change the quality of signal. Watermarking is the science and art of hiding secret information in which neither the sender nor the receiver would...