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hemati--azam
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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...
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...
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...
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...
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...
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...
Synthesis of Palladium Nanowires for Hydrogen Gas Sensor by Field Ionization
, M.Sc. Thesis Sharif University of Technology ; Irajizad, Azam (Supervisor)
Abstract
The interesting properties of metallic nanowires provide many applications in electronic sensors. In this project, we have synthesized Pd nanowires using electrodeposition method. These nanowires are useful for hydrogen sensors by measuring field ionization current in gas. In this project, Pd nanowires were synthesized by electrochemical deposition method in PCT template with 100 nm pore size. The used solution was contained 2mM PdCl2 + 0.1M HCl. The best reduction potential was determined about -0.2V and the best time for synthesizing nanowires was 7 minutes. Chronoampermetric diagrams showed four steps, capacitive current, growth in the holes, reaching to the surface of PCT and the growth...
Study of Local Density of States in MoS2 Nanosheets by Scanning Tunneling Spectroscopy
, M.Sc. Thesis Sharif University of Technology ; irajizad, Azam (Supervisor)
Abstract
Recently, the applications of two dimension materials have been increased in nanotechnology. Among this group of material the Transition metal dichalcogenide due to their energy gap and their particular optical features has attracted much attention. For instance MoS2 is a most famous material in this familyand as a semiconductor has an indirect energy gap about 1.3 eV in the bulk status and 1.9 eV in monolayer. In this project, we investigated the Nano-sheet optical properties of MoS2 by using of tunneling spectroscopy. In this procedure a thin probe is close to the surface until a quantum tunneling occurs between the probe and the sample. By measure the tunneling current we can achieve much...
Surfactant effects on the particle size, zeta potential, and stability of starch nanoparticles and their use in a pH-responsive manner
, Article Cellulose ; Volume 24, Issue 10 , 2017 , Pages 4217-4234 ; 09690239 (ISSN) ; Kashanian, S ; Hemati Azandaryani, A ; Omidfar, K ; Bazyar, E ; Sharif University of Technology
2017
Abstract
Storage conditions seem to be important in the long-term stability of nanoparticles (NPs). This work studies the effects of surfactants and storage container on particle size distribution and zeta potential during long-term storage of acid hydrolyzed potato starch NPs. The NPs were prepared from potato starch using acid hydrolysis and high-intensity ultrasonication. During the ultrasonic treatment, the surfactants were added dropwise to the solutions to reduce the size and stabilize the formed NPs. Particle size distribution, zeta potential, and FE-SEM were used to characterize the ensuing NPs. Additionally, a 5-month stability study was performed to evaluate the maintenance of potato starch...
Performance analysis of the outer rotor variable reluctance resolver
, Article 2023 3rd International Conference on Electrical Machines and Drives, ICEMD 2023 ; 2023 ; 979-835039374-3 (ISBN) ; Hajmohammadi, S ; Nasiri Gheidari, Z ; Hemati, D ; Oraee, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Position sensors are essential in the control of moving systems. Variable Reluctance (VR) resolvers are used as position sensors in the control of permanent magnet motors due to their simple and robust structure. VR resolvers can be built in outer/inner stator configuration. Although most of the commercial VR resolvers have outer stator /inner rotor configuration, the manufacturing process of the inner stator resolver is much simpler than that of outer stator ones. However, design considerations of inner stator/outer rotor configurations are not well established. Therefore, in this paper the influence of different number of stator slots, pole number of windings, and number of rotor saliency...
Strain Effect on the CO & H2 Adsorption Upon Graphene
, M.Sc. Thesis Sharif University of Technology ; Irajizad, Azam (Supervisor)
Abstract
In this thesis, adsorption of Carbon monoxide and Hydrogen on graphene, by DFT calculation has been studied. Also effect of strain on some electrical properties, such as band structure, electrical conductivity and Density of states, for pristine graphene and adsorption CO and H2 on it has been probed. This results show that with strain up to 12% on pristine graphene , we won’t have any band gap on Fermi surface and energy adsorption for Carbon monoxide on strained graphene (up 12%) increase up 400 per cent. Also for strained graphene (12%) on Carbon monoxide adsorption condition we will have energy band gap almost a few electron volt on Fermi surface. In general this results express...
Investigation of Buckling Phenomenon in Fiber Production Using Direct Electrospinning
, M.Sc. Thesis Sharif University of Technology ; Iraji Zad, Azam (Supervisor)
Abstract
Duringfalling a viscous liquid freely on a surface, the viscous thread bends due to a phenomenon called buckling. The gravity force in this process could be replaced by an electric force in electrospinning process. In the present thesis, we have designed a number of setups in order to investigate the buckling phenomenon in two categories of helical and non-helical buckling by using direct electrospinning process. By making the collector moving, the electrospun fibers show several shapes including coiling, meander, figure of 8 shape, etc. There are three effective forces acting in this process which are viscous force, electric force and inertia. Also there are three distinct regimes defined...
Fabrication of one Dimensional Nano-Structured of Titanium Dioxide and their Application in Dye Sensitized Solar Cells
, M.Sc. Thesis Sharif University of Technology ; Iraji Zad, Azam (Supervisor)
Abstract
In this research we focus on study and fabrication of titanium dioxide nanofibers and their application in preparation of dye sensitized solar cell’s photo anode in order to improve optical and electrical properties. Titanium dioxide nanofibers was prepared by electroespinning method. To investigate the effect of nanofiber diameter on optical and electrical properties of photo anode, three different diameter of titanium dioxide nanofibers with diameters of 100-200 nm, 200-300 nm and 500-600 nm was prepared by varying the type or amount of polymer in the electrospinning solution and fixing other conditions of electrospinning process. By use of these structures, paste of pure fibers in form of...
Preparation and Stabilizing Graphene Sheets for Gas Sensing Application
, M.Sc. Thesis Sharif University of Technology ; Iraji zad, Azam (Supervisor)
Abstract
Graphene is one of the most attractive subjects for scientists in the last decade. Its unique properties has been probed by many research groups and innumerable projects have been developed to investigate applications of graphene in electronics, mechanics, biophysics etc. Due to high surface to volume ratio and magnificent electron mobility in graphene, it is a suitable candidate for gas sensing. This has been proved by several theoretical and experimental researches for various gases such as CO, NH3 and NO2 etc. In present thesis, graphene has been prepared chemically and transferred to silicone substrates that are previously coated with a 300 nanometer silicone dioxide layer, by dip...
Preparation and Characterization of One-dimensional Copper Oxide Nanostructures for Field Ionization Gas Sensors
, M.Sc. Thesis Sharif University of Technology ; Iraji Zad, Azam (Supervisor)
Abstract
The purpose of this project is to construct a gas sensor based on one-dimensional nanostructured electrodes of copper oxide. By creating of these nanostructures, can be reduced breakdown voltage of gases, including flammable, to a few hundred volts. The CuO nanowires were grown by thermal oxidation on copper substrate to form self-assembled. In this method, by heating the copper foil,Cu2O also was formed on substrate. Effects of surface tension of substrate and oxidation temperature on surface density and structure of the nanowires were studied. SEM images taken from the samples showed that the surface tensions increases the density of nanowires and increasing the oxidation temperature leads...
Optical and Electrical Properties of Nanostructures Prepared by Hydrothermal Method for Application in Nanostructured Solar Cell Electrode
, M.Sc. Thesis Sharif University of Technology ; Iraji Zad, Azam (Supervisor)
Abstract
In this research we focus on study and fabrication of one dimentianal TiO2 nanostructures and nanoheterostructures on TiO2 nanofibers in order to use them in Dye Sensitized Solar Cells (DSC). Nanofibers of titanium oxide have been fabricated using hydrothermal method. Then, hierarchical TiO2 nanostructures were grown on the nanofibers via another hydrothermal step. Increasing the effective surface of nanofibers, we achieved two secondary architectures from fibers:1-Nanoparticular fibers (TiO2 nanoparticles grown on nanofibers).2-Nanostars.After fabrication, the SEM and XRD characterizations were provided. Furthermore, the suitable pastes of these nanostructures were prepared for application...
Design and Construction of Tunneling Spectroscope to Study Reaction of Gas with Porous Silicon Surface
, M.Sc. Thesis Sharif University of Technology ; Iraji zad, Azam (Supervisor)
Abstract
Studying the interactions between gas molecules and surface is one of the important issues in the field of sensing. In nanometer scales, it can play a key role in fabricating novel nanosensors. Tunneling spectroscopy, on the other hand, is a powerful method for studying the local electrical properties of surface. Our purpose in this project is to design and construct a local tunneling spectroscope, which is able to probe the effects of adsorption of gas molecules on local density of state (LDOS) in sub-nanometer scales. The designed and constructed local tunneling spectroscope system includes a small chamber, which is isolated from any vibrations by means of a set of dampers. In the main...
Doping Effect of Copper and Copper Oxide on H2S Sensing of Nanostructured WO3
, M.Sc. Thesis Sharif University of Technology ; Iraji Zad, Azam (Supervisor)
Abstract
The aim of this research is preparation of tungsten trioxide nanoparticles film for hydrogen sulfide gas sensing. These nanoparticles were made by simple and inexpensive sol-gel method. To improve gas sensing properties, various precursors of copper and copper oxides were added to the sol. This solution was coated on alumina substrate by spin coating method. After annealing, sensing properties of samples were studied by measuring the electrical resistance. Best precursor and its molar percentage of copper to tungsten were selected (WO3-Cu2O (1%)). All tests for this sample were done in temperatures below 100 °C and gas concentration lower than 10 ppm. Sensitivity of WO3-Cu2O (1%) to 1 ppm...
Fast Alignment-free Protein Comparison Approach based on FPGA Implementation
, M.Sc. Thesis Sharif University of Technology ; Koohi, Somayyeh (Supervisor)
Abstract
Protein, as the functional unit of the cell, plays a vital role in its biological function. With the advent of advanced sequencing techniques in recent years and the consequent exponential growth of the number of protein sequences extracted from diverse biological samples, their analysis, comparison, and classification have faced a considerable challenge. Existing methods for comparing proteins divide into two categories: methods based on alignment and alignment-free. Although alignment-based methods are among the most accurate methods, they face inherent limitations such as poor analysis of protein groups with low sequence similarity, time complexity, computational complexity, and memory...