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    On Proofs and Some Consequences of Serre’s Conjecture on Projective Modules

    , M.Sc. Thesis Sharif University of Technology Abbasi Fakhr, Jalil (Author) ; Jafari, Amir (Supervisor)
    Abstract
    Jean-Pierre Serre in 1955, in his famous article “Faisceaux Algébriques Cohérents” asked if there is any finitely generated projective module on polynomial rings which is not free. Or equivalently: is there any non-trivial algebraic vector bundle over an affine space? The negative answer to this question is known as Serre’s conjecture and it was an open problem in algebra and affine algebraic geometry until 1976, when it was proved independently by Quillen and Suslin. The challenge of solving this question and its consequences led to a vast amount of research in commutative algebra, homological algebra and algebraic K-theory and inspired generalizations and similar questions. In this thesis... 

    Applying TPM Concept in an Alloy Steel Plant

    , M.Sc. Thesis Sharif University of Technology Fakhr-al-hosseini, Mehdi (Author) ; Houshmand, Mahmoud (Supervisor)
    Abstract
    The alloy steel plant was exploited in1999; and the maintenance department starts its function and its activities according to the written PM software by Austria’s BOHLER Company. The PM program was written for the entire factory. Having worked with the PM for eight years, now it is possible to evaluate its performance. There are two main problems in the maintenance system; firstly, the existing PM System is incomplete, some important feature of the PM program is incomplete. Secondly there are lacks of a good auditing system to evaluate the PM orders. To evaluate the weakness of the current PM system and to study application of TPM, a section of the factory was... 

    Aerodynamic Design of 100 kW Transonic Ducted Fan

    , M.Sc. Thesis Sharif University of Technology Shayan Fakhr, Atefeh (Author) ; Ghorbanian, Kaveh (Supervisor)
    Abstract
    The purpose of this research is the aerodynamic design of a 100 kW transonic ducted fan. Today, the aviation industry is moving towards the design of electric driven aircraft propulsion. Transonic ducted fans are one of the viable options that have been used in medium and heavy aircrafts due to their high specific power. In this research, the meanline model has been used for the initial design. By applying the design constraints, design limitations, design and functional parameters, the initial design point is found and then a sensitivity analysis is performed with respect to the effective design parameters to obtain the optimal design point. For the initial design of the transonic ducted... 

    The addition of data aggregation to SPEED routing algorithm while keeping the functionality of available techniques

    , Article 2nd International Conference on Future Networks, ICFN 2010, 22 January 2010 through 24 January 2010 ; January , 2010 , Pages 349-353 ; 9780769539409 (ISBN) Roustaei, R ; Yousefi Fakhr, F ; Movaghar, A ; Sharif University of Technology
    2010
    Abstract
    Data aggregation is a technique that is used to decrease extra and repetitive data in cluster based routing protocols. As we know SPEED routing algorithm is based on service quality and dose not perform data aggregation. In this article, we try to add an data aggregation technique to the available techniques without interfering with the functions of previous ones. The idea involves virtual configuration of sensors and specification of an individual ID to the created data by the sensors in each region, then data aggregation in relay node is done by this ID, resulting in less energy consumption, lower traffic and repeated data, an increase in network lifetime and better quality of service  

    The addition of data aggregation to non cluster based SPEED routing algorithm while keeping the functionality of available techniques inorder to increase QoS

    , Article ; Volume 2 , April , 2010 , Pages V2696-V2700 ; ICCET 2010 - 2010 International Conference on Computer Engineering and Technology, Proceedings, 16 April 2010 through 18 April 2010 ; 9781424463503 (ISBN) Yousefi Fakhr, F ; Roustaei, R ; Movaghar, A ; Sharif University of Technology
    2010
    Abstract
    Data aggregation is a technique that is used to decrease extra and repetitive data in cluster based routing protocols. As we know SPEED routing algorithm is based on service quality and dose not perform data aggregation. In this article, we try to add an data aggregation technique to the available techniques without interfering with the functions of previous ones. The idea involves virtual configuration of sensors and specification of an individual ID to the created data by the sensors in each region, then data aggregation in relay node is done by this ID, resulting in less energy consumption, lower traffic and repeated data, an increase in network lifetime and better quality of service  

    Processing Queries with Mathematical Expressions on Encrypted Outsourced Databases

    , M.Sc. Thesis Sharif University of Technology Naseri Boroujeni, Saeed (Author) ; Jalil, Rasool (Supervisor)
    Abstract
    The ever-increasing volume of data and the lack of computational and storage facilities have caused a managerial challenge to organizations. The existence of these challenges on the one hand and the increase of storage services on the other hand have compelled the organizations to delegate their storage and management of data to the server providers of cloud storage services. The outsourcing of data to servers obviates the need for purchasing exorbitant storage equipment and recruiting professional workforce in the organization. Since the organization’s data will be kept outside the organization’s ambience in case of using such services in form of outsourcing, and the data will not be under... 

    Dynamic Functional Connectivity in Autism Spectrum Disorder Using Resting-State fMRI

    , M.Sc. Thesis Sharif University of Technology Jalil Piran, Fardin (Author) ; Fatemizadeh, Emadeddin (Supervisor)
    Abstract
    Autism Spectrum Disorder (ASD) is a group of neurodevelopmental disorders that cause repetitive behaviors and social and communication skills abnormalities. Autistic Disorder(AD) is one of the disorders in ASD that is being investigated in this study. There has been an increase in research about AD in recent years due to the increasing AD prevalence and the high autistic living costs. The dynamic functional connectivity between healthy and autistic groups has been analyzed by using graph theory. The brain is modeled as a dynamic graph using resting-state fMRI. The graph theory metric is calculated in the dynamic graph of each subject, and the distinction of the two groups is checked using... 

    Increasing the Efficiency of Solar Cells Through the Redesign of the Cell Structure and the Addition of A Sensorless Solar Tracker

    , M.Sc. Thesis Sharif University of Technology jalil Sarghaleh, Arsalan (Author) ; Kavehvash, Zahra (Supervisor)
    Abstract
    In this thesis, the efficiency of energy conversion in solar cells has been enhanced through the use of an innovative structure combining a wideband plasmonic solar absorber (UWB), quantum dots (QDs), and an intermediate band (RB-IBSC). The QD structure has been integrated with a plasmonic array and optimized accordingly. Although the conventional QD structure is effective in improving solar cell efficiency, it has two fundamental issues. Firstly, the short carrier lifetime, which has been addressed by adding the RB-IBSC band. The key concept behind RB-IBSCs involves creating a structure that facilitates electron movement more effectively in one direction than in the other. By asymmetric... 

    Numerical investigation of effects of uniform magnetic field on heat transfer around a sphere

    , Article International Journal of Heat and Mass Transfer ; Volume 114 , 2017 , Pages 703-714 ; 00179310 (ISSN) Abbasi, Z ; Molaei Dehkordi, A ; Abbasi, F ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    In this article, ferrohydrodynamic forced-convection heat transfer from a heated sphere embedded in a ferrofluid in the presence of the uniform external magnetic field has been studied numerically for the first time over a wide range of Reynolds number value, nanoparticle diameter, particle volume fraction, and magnetic field intensity. Despite the uniform external magnetic field applied, the internal magnetic field near the sphere could be nonuniform due to the considerable difference between the relative magnetic permeability of the sphere and the surrounding medium. Kelvin body force arises from this nonuniformity and induces vortexes near the sphere. These vortexes disturb the boundary... 

    Deep interpretation of parkland environment for autonomous landscaping robot for the green smart city

    , Article 4th International Conference on Pattern Recognition and Image Analysis, IPRIA 2019, 6 March 2019 through 7 March 2019 ; 2019 , Pages 185-189 ; 9781728116211 (ISBN) Jalil Piran, S ; Majidi, B ; Manzuri, M. T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    In the past decade, making the cities green and environmentally friendly is becoming a major issue for many countries around the world. The green city is an urban environment in which the parklands and natural habitats are integrated into the living and the working space of the communities. This significant increase in the scale of parklands in the green cities requires autonomous landscaping. In this paper, a computer vision system for an autonomous landscaping robot which is capable of seeding various types of grass and designing patterns in the lawns is developed. The proposed robotic platform uses deep convolutional neural networks for finding the required patches for the replanting of... 

    Tunable spatial fractional derivatives with graphene-based transmit arrays

    , Article Optics Express ; Volume 31, Issue 8 , 2023 , Pages 12572-12584 ; 10944087 (ISSN) Jalil Abadi, F. S ; Habibiyan, H ; Khavasi, A ; Sharif University of Technology
    Optica Publishing Group (formerly OSA)  2023
    Abstract
    The optical implementation of mathematical spatial operators is a critical step toward achieving practical high-speed, low-energy analog optical processors. In recent years, it has been shown that using fractional derivatives in many engineering and science applications leads to more accurate results. In the case of optical spatial mathematical operators, the derivatives of the first and second orders have been investigated. But no research has been performed on fractional derivatives. On the other hand, in previous studies, each structure is dedicated to a single integer order derivative. This paper proposes a tunable structure made of graphene arrays on silica to implement fractional... 

    Biosorption of Zinc Ions Using Biomasses Produced From Four Different Types of Microbes Under Batch and Continuous Conditions

    , M.Sc. Thesis Sharif University of Technology Hosseini, Soheil (Author) ; Roostaazad, Reza (Supervisor) ; Razavi, Jalil (Supervisor)
    Abstract
    Biosorption capacity of zinc (II) by biomasses produced from four species of microorganism including two kinds of bacteria (Pseudomonas putida and Streptomyces rimosus) and two kinds of fungi ( Aspergillus niger and Phanerochate chrysosporium) in batch case were investigated and compared. In all cases dried original bio mass and dried pretreated bio mass with NaOH were used. In all cases biosorption capacity of pretreated biomasses were much higher than non-treated biuomasses to the ratio of 3.8 – 1.4 times. Freundlich and Langmuir equilibrium isotherms were used to match with experimental results of this research. Except S.rimosus, all others were completely matched with Langmuir... 

    Investigation of Water Electrical Parameters as a Function of Measurement Frequency and Concentration Using Cylindrical Capacitive Sensors

    , M.Sc. Thesis Sharif University of Technology Hosseinzadeh Fakhr, Mahan (Author) ; Golnabi, Hossein (Supervisor) ; Gobal, Fereydoon (Co-Advisor)
    Abstract
    The electrical conductivity of the solution has been one of the important physical quantities in many application. In this respect many probes and devices such as conductive sensors have been devised. In this study electrical properties of different water samples at frequency step range of 100-100000 Hz are measured by using the long cylindrical capacitive sensor and a measuring module (LCR-703). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water samples shows a decrease by increasing the measurement frequency. In another study the dielectric... 

    A method for simulation of vapour cloud explosions based on computational fluid dynamics (CFD)

    , Article Journal of Loss Prevention in the Process Industries ; Volume 24, Issue 5 , 2011 , Pages 638-647 ; 09504230 (ISSN) Tauseef, S. M ; Rashtchian, D ; Abbasi, T ; Abbasi, S.A ; Sharif University of Technology
    2011
    Abstract
    The effectiveness of the application of CFD to vapour cloud explosion (VCE) modelling depends on the accuracy with which geometrical details of the obstacles likely to be encountered by the vapour cloud are represented and the correctness with which turbulence is predicted. This is because the severity of a VCE strongly depends on the types of obstacles encountered by the cloud undergoing combustion; the turbulence generated by the obstacles influences flame speed and feeds the process of explosion through enhanced mixing of fuel and oxidant. In this paper a CFD-based method is proposed on the basis of the author's finding that among the various models available for assessing turbulence, the... 

    Thin film graphene oxide membrane: challenges and gas separation potential

    , Article Korean Journal of Chemical Engineering ; Volume 35, Issue 5 , May , 2018 , Pages 1174-1184 ; 02561115 (ISSN) Abbasi, F ; Karimi Sabet, J ; Ghotbi, C ; Abbasi, Z ; Sharif University of Technology
    Springer New York LLC  2018
    Abstract
    Graphene oxide membranes were prepared by vacuum and pressurized ultrafiltration methods on the 12% modified Polyacrylonitrile (12mPAN) substrate to specify challenges, salient features, future directions, and potential of GO membrane for separation fields using characterization techniques and gas separation test (studied gases are CO2, He and N2), which is an efficient tool for better understanding of GO membrane behavior. GO membrane structure was examined over a wide range of parameters, such as pore size range of substrate and its surface properties, pH of GO dispersion, GO content, synthesis pressure, operating pressure and temperature. The results show that the GO content does not hold... 

    Conversion of CO into CO2 by high active and stable PdNi nanoparticles supported on a metal-organic framework

    , Article Frontiers of Chemical Science and Engineering ; 2021 ; 20950179 (ISSN) Abbasi, F ; Karimi Sabet, J ; Abbasi, Z ; Ghotbi, C ; Sharif University of Technology
    Higher Education Press Limited Company  2021
    Abstract
    The solubility of Pd(NO3)2 in water is moderate whereas it is completely soluble in diluted HNO3 solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH2(Cr) were synthesized by aqueous solution of Pd(NO3)2 and Pd(NO3)2 solution in dilute HNO3 and used for CO oxidation reaction. The catalysts synthesized with Pd(NO3)2 solution in dilute HNO3 showed lower activity. The aqueous solution of Pd(NO3)2 was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd70Ni30/MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd + Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution... 

    Conversion of CO into CO2 by high active and stable PdNi nanoparticles supported on a metal-organic framework

    , Article Frontiers of Chemical Science and Engineering ; 2021 ; 20950179 (ISSN) Abbasi, F ; Karimi Sabet, J ; Abbasi, Z ; Ghotbi, C ; Sharif University of Technology
    Higher Education Press Limited Company  2021
    Abstract
    The solubility of Pd(NO3)2 in water is moderate whereas it is completely soluble in diluted HNO3 solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH2(Cr) were synthesized by aqueous solution of Pd(NO3)2 and Pd(NO3)2 solution in dilute HNO3 and used for CO oxidation reaction. The catalysts synthesized with Pd(NO3)2 solution in dilute HNO3 showed lower activity. The aqueous solution of Pd(NO3)2 was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd70Ni30/MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd + Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution... 

    Conversion of CO into CO2 by high active and stable PdNi nanoparticles supported on a metal-organic framework

    , Article Frontiers of Chemical Science and Engineering ; Volume 16, Issue 7 , 2022 , Pages 1139-1148 ; 20950179 (ISSN) Abbasi, F ; Karimi Sabet, J ; Abbasi, Z ; Ghotbi, C ; Sharif University of Technology
    Higher Education Press Limited Company  2022
    Abstract
    The solubility of Pd(NO3)2 in water is moderate whereas it is completely soluble in diluted HNO3 solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH2(Cr) were synthesized by aqueous solution of Pd(NO3)2 and Pd(NO3)2 solution in dilute HNO3 and used for CO oxidation reaction. The catalysts synthesized with Pd(NO3)2 solution in dilute HNO3 showed lower activity. The aqueous solution of Pd(NO3)2 was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd70Ni30/MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd + Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution... 

    Improved method for increasing accessible pores of MIL-101(Cr) by encapsulation and removal of Phosphotungstic acid (PTA): Pd/PTA-MIL-101(Cr) as an effective catalyst for CO oxidation

    , Article Journal of Cleaner Production ; Volume 347 , 2022 ; 09596526 (ISSN) Abbasi, F ; Karimi Sabet, J ; Abbasi, Z ; Ghotbi, C ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    This study forwards a novel and simple approach for encapsulation of Phosphotungstic acid (PTA) into MIL-101(Cr) cavities to develop PTA-MIL-101(Cr) with a high surface area. In this method, the resulting surface area of PTA-MIL-101(Cr) (3563 m2/g) is 1.72 times that of MIL-101(Cr) due to the existence of more accessible pores which are formed by leaching of PTAs incorporated inside MIL-101(Cr) pores during the intense washing. Catalysts are investigated in CO oxidation under atmospheric pressure and feed composition of 1%CO, 20%O2, and 79%He. 3%Pd/PTA-MIL-101(Cr) shows 100%CO conversion at T = 145 °C and outperforms PTA, PTA-MIL-101(Cr), Pd/PTA, 1–3%Pd/MIL-101(Cr), Pd-PTA/MIL-101(Cr), and... 

    Design of electrostatic actuators for suppressing vertical disturbances of CMOS-MEMS capacitive force sensors in bio applications

    , Article Mechanics and Industry ; Volume 16, Issue 3 , 2015 ; 22577777 (ISSN) Jalil Mozhdehi, R ; Selk Ghafari, A ; Khayyat, A. A ; Sharif University of Technology
    EDP Sciences  2015
    Abstract
    The objective of this work is to design electrostatic actuators for a CMOS-MEMS nano-newton capacitive force sensor to suppress vertical vibrations disturbances. Electrostatic actuators are selected because the movable part of this force sensor is anchored to the fixed parts. In the first step, we propose a framework for simulation of the force sensor based on finite element method. The proposed model is modified utilizing comparison between the simulation and experimental models to improve the performance of the model. Then, 14 pairs of electrostatic actuators are designed for applying the control algorithm and their pull-in voltage is calculated. In next step, Modal Analysis is applied to...