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    Numerical Simulation of Two-dimensional Sonoluminescence Phenomenon, Using Front Tracking/Ghost Fluid Method

    , M.Sc. Thesis Sharif University of Technology Moezzi Rafie, Hamid (Author) ; Tayyebi Rahni, Mohammad (Supervisor)
    Abstract
    Sonoluminescence is a unique phenomenon in physics, which is known as the process of converting sound into light. By applying sound to a volume of liquid, with a specific geometrical shape (such as sphere) and forming standing waves around an existing bubble, the bubble first expands to a maximum radius and then gets extremely small leading to its supersonic collapse. During the collapse, the resulting shock wave approches the center of the bubble, causing extreme increase in the pressure and temperature at the center of the bubble. This causes flashing of light during small time scales (pico-seconds). This phenomenon is used in many fields, such as treatment of cancer. Also, the energy... 

    , M.Sc. Thesis Sharif University of Technology Abtahi, Mohammad Reza (Author) ; Abedini, Javad (Supervisor)
    Abstract
    In this piece of work, a gravity model is suggested as Iranian non-fuel export model to OIC countries. The most important results out of this model are the acquired coefficients of two variables, namely “ECO membership” and “Economic and Trade Freedom of Importer”. At first, we expected that for importer, being a member of ECO would increase the amount of trade with iran. Surprisingly, this is not what we see in a model. In fact, as ECO has not achieved any tangible success in increasing trade between its members, eastern Asian Muslim countries has become an important trade partner for iranians. This result is compatible with other pieces of researches about ECO. “Economic and Trade Freedom... 

    Relay-assisted Multiple-input Multiple-output Underwater Wireless Optical Communication Systems

    , M.Sc. Thesis Sharif University of Technology Jamali, Mohammad Vahid (Author) ; Salehi, Javad (Supervisor)
    Abstract
    Today’s growing interest to the underwater explorations and navigations demands to design appropriate underwater communication methods and systems. However, radio frequencies which are widely being used in free space communications, can’t be a good candidate for underwater wireless communications, due to their sever attenuation in water. On the other hand, underwater acoustic communication has been widely studied and implemented in the past decades, inspired by suitable propagation of acoustic waves through the underwater medium. Nevertheless, acoustic communication systems have limited bandwidth, lower propagation speed and lower security than optical counterparts, which suggests underwater... 

    Mobility-Aware Resource Allocation in Hybrid Visible Light Communication and 5G Radio Access Technologies Networks

    , M.Sc. Thesis Sharif University of Technology Dastgheib, Mohammad Amir (Author) ; Salehi, Javad (Supervisor)
    Abstract
    Visible light communication (VLC) uses huge license-free spectral bandwidth of visible light for high-speed wireless communication. Since each VLC access point covers a small area, handovers of mobile users are inevitable. In order to deal with these handovers, developing fast and effective resource allocation algorithms is a challenge. this paper introduces the problem of mobility-aware optimization of resources in hybrid VLC and 5G radio access technologies networks using the T-step look-ahead policy and employing the notion of handover efficiency. It is shown that the handover efficiency can correlate the overall performance of the network with future actions based on the mobility of... 

    Introducing a Numerical Method for Estimating Median Crack Depth during Machining on Optical Glasses

    , Ph.D. Dissertation Sharif University of Technology Asqari, Mohammad Amin (Author) ; Akbari, Javad (Supervisor)
    Abstract
    In present research, a cohesive based finite element model has been introduced to estimate median crack depth during mechanical machining on optical glasses. Development of the machining numerical model has been initiated by investigating the indentation process. Experimental results of this step have been calibrated primary numerical model which has been used in the scratch process. Due to differences between the scratch mechanism and indentation one, mathematical bases fracture formulas and cohesive relations have been developed. After extracting primary result, using them in the scratch model and developing the primary model, ultimately numerical model has been evolved to an abstract... 

    Production of Uranium Dioxide Nano Powder With Hydrothermal Method in Supercritical Water Reactor

    , M.Sc. Thesis Sharif University of Technology Golzary, Abooali (Author) ; Outokesh, Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor) ; Karimi Sabet, Javad (Co-Advisor)
    Abstract
    Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

    Lithium Isotopes Separation by Electrolysis Amalgam by a Continuous Method

    , M.Sc. Thesis Sharif University of Technology Kowsari, Mohammad Reza (Author) ; Outokesh, Mohammad (Supervisor) ; Ahmadi, Javad (Co-Advisor)
    Abstract
    Lithium has 9 isotopes which two isotopes are stable and remaining isotopes are unstable and have half-life. Lithium stable isotopes include 6Li and 7Li that their abundance is 7.53% and 92.47% respectively. Importance of lighter lithium isotope appears for its small cross section against thermal neutron and producing fusion reactors fuel in nuclear industries. Thermal neutron absorption cross section for 6Li and 7Li are 950 barn and 37 mbarn respectively. Interesting of these isotopes in nuclear industry is due to the large difference in the absorption cross section.6Li compounds implied for tritium producing in coat of nuclear fusion reactor with DT fuel. Following tritium is used in... 

    A tunable high-Q active inductor with a feed forward noise reduction path

    , Article Scientia Iranica ; Volume 21, Issue 3 , 2014 , Pages 945-952 ; ISSN: 10263098 Moezzi, M ; Bakhtiar, M. S ; Sharif University of Technology
    2014
    Abstract
    The analysis and design of a tunable low noise active inductor is presented. The noise performance of the proposed gyrator-based active inductor is improved without either degrading its quality factor or consuming more power using a linear Feed Forward Path (FFP). The proposed low noise active inductor has been designed and fabricated using standard 0.18-μm CMOS technology. The measurements show a 3 fold improvement in the input noise current compared to that of conventional active inductors. The active inductor was tuned and measured at the resonance frequency of 2.5 GHz, which could be extended as high as 5.5 GHz, with a quality factor of 30. The circuit draws 4.8 mA from a 1.8 V supply  

    Wideband LNA using active inductor with multiple feed-forward noise reduction paths

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 60, Issue 4 , 2012 , Pages 1069-1078 ; 00189480 (ISSN) Moezzi, M ; Sharif Bakhtiar, M ; Sharif University of Technology
    2012
    Abstract
    In this paper, an area-efficient LNA with on-chip input matching circuit utilizing an active inductor is presented. The active inductor is implemented based on the gyrator structure and its noise is improved by employing a feed-forward path (FFP). The overall low-noise performance of the LNA is achieved by cancelling the inductor noise through an additional FFP. It is shown that the proposed LNA circuit is capable of achieving low-noise performance with wideband tuning at the input in a small die area. A 0.32- to 1-GHz LNA has been designed and fabricated in a standard 0.18-μm CMOS technology. The LNA occupies a die area of less than 0.1 mm 2. The measured results show noise figure of... 

    Design of LC Resonator for Low Phase Noise Oscillators

    , Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 63, Issue 2 , 2016 , Pages 169-180 ; 15498328 (ISSN) Moezzi, M ; Sharif Bakhtiar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    The effects of resonator topology on the phase noise of LC oscillators are studied in this paper. It is shown that there is a neglected factor that can considerably influence the phase noise behavior of the oscillator. We designate this factor as the Inductance Energy Factor (IEF), which directly depends on the topology of the resonator. It is shown that through proper design of the resonator for a better IEF, the oscillator phase noise can be improved. It is also shown that by modifying the resonator structure to improve IEF, the phase noise does not have to be constrained by the minimum realizable inductance and its maximum quality factor. Therefore, the power-phase noise trade-off remains... 

    Spectral Element Simulations of Wave Propagation in Porous Fluid-Saturated Media

    , M.Sc. Thesis Sharif University of Technology Moezzi, Mohammad Javad (Author) ; Naghd Abadi, Reza (Supervisor) ; Asghari, Mohsen (Supervisor) ; Mazaheri, Hashem (Co-Advisor)
    Abstract
    The aim of this work is numerical analysis of wave propagation in earth by using spectral element method for single and multi phase with application in oil industry. In this method, numerical solution has high accuracy due to using high order polynomials and appropriate integration points. Also, the mass matrix is diagonal by using this method which results in considerable decrease in computational cost with respect to finite element method.
    The wave propagation in the mentioned models is studied by many researchers. The main problem in petroleum industry is large dimension of the model which results in high computational costs. Thus, using the proper numerical approach for these... 

    Design, Analysis and Manufacturing of Gas Foil Bearing

    , M.Sc. Thesis Sharif University of Technology Majidi, Mohammad Hassan (Author) ; Akbari, Javad (Supervisor) ; Movahhedy, Mohammad Reza (Supervisor)
    Abstract
    Foil gas bearings are compliant surface, self-acting hydrodynamic bearings that use ambient gas as their working fluid. They do not require external pressurization and are typically constructed from several layers of sheet metal foils. In high-speed, high-temperature applications the GFB’s have the advantage of developing higher load capacities than with fixed geometry gas bearings. Since GFB’s have a complex structure consisting of a spring-like substructure with an overlying flexible surface, there exists a great variety of permutations on any given design. At current work presents a 1D model for GFB with couple solving Reynolds and Euler-Bernoulli beam equation. This mean top foil assume to... 

    A Study on Automatic and Early Detection of Lameness in Dairy Cattle

    , M.Sc. Thesis Sharif University of Technology Honarvar Mahjoobin, Mohammad Hadi (Author) ; Akbari, Javad (Supervisor)
    Abstract
    Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

    Boron Isotope Separation by Distillation of BF3-(C2H5)2O Complex

    , M.Sc. Thesis Sharif University of Technology montazeri, Meysam (Author) ; Otukesh, Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor)
    Abstract
    Natural boron consists of two stable isotopes, mass 10 (19.3%) and mass 11 (80.7%). 10B isotope has a large thermal neutron capture cross-section and it therefore, used widely in such aspects as modern industry, military equipment, medical science and so on. specially the demand of atomic energy industry for the boron isotope is increased severely. So the separation of 10B from natural boron has received very wide attention at present. There are many kinds of methods on the boron isotopes separation, such as chemical exchange reaction and distillation in boron trifluoride method, ion exchange in boric acid solution method, counter current recycle membrane cascades in boron trifluoride... 

    The Synthesis and Characterization of Nano Zeolitic Molecular Sieve for Separation of 133Xe from 85Kr

    , Ph.D. Dissertation Sharif University of Technology Charkhi, Amir (Author) ; Kazemeini, Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor)
    Abstract
    In this study the feasibility of xenon separation from xenon-krypton mixture was investigated by utilizing of the chromatographic column filled with nano and micron sized NaY zeolite. For this purpose the nano NaY with the yield of 100% related to Al2O3 and the average size of 98.6 nm was synthesized through the clear solution method with the mid-adding of NaOH. Furthermore, a novel method for granulation of nano zeolite was developed by utilizing sodium alginate as an external template. In this method the production of uniform spherical granules with the different sizes in the range of several milimiteres to 100 µm was easily performed. Moreover, the results showed that the adding of... 

    Separation of Boron Isotopes by Distillation of (CH3)2O-BF3 Complex

    , M.Sc. Thesis Sharif University of Technology abdollahi, Mojtaba (Author) ; Outokesh, Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor)
    Abstract
    Natural boron includes two stable isotopes 10B and 11B with 19.3 and 80.7 weight percent respectivley.10B isotope has a high thermal neutron absorption cross section. So isotope 10B material is suitable for making atomic reactor control rods. Other and even more important applications of 10B are in disclosing neutrons in order to measure neutron reactors fluxes and also are in nuclear physics laboratories and medical radiation. This isotope also is used in the pharmaceutical and the military industries. There are several methods for separating boron isotopes. Among the distillation methods, thermal diffusion of BF3, distillation of BF3, distillation of methyl borate, boric acid distillation... 

    Using Game Theory to Battle Jammer in Control Channel of Ad-hoc Cognitive Radio Networks

    , M.Sc. Thesis Sharif University of Technology Golzari Oskoui, Mohammad Reza (Author) ; Salehi, Javad (Supervisor)
    Abstract
    Due to both dynamic and opportunistic spectrum access, Cognitive radio networks is a promising solution for spectrum scarcity problem. In cognitive radio networks, users need to have a control channels in order to cooperate for sharing the sensing information, channel sharing and etc. In Ad-hoc cognitive radio networks because of the absence of infrastructure and central nodes, every user runs a distributed algorithm to create a common control channel. If the control channel gets jammed, network’s performance degrades dramatically, therefore the jammer’s target in cognitive radio networks is the control channels to disturb the networks’ performance. The traditional solution to confront... 

    Synthesis and Fuctionalization of Graphene oxide for Thorium Adsorption

    , M.Sc. Thesis Sharif University of Technology Doram, Amir (Author) ; Outokesh , Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor)
    Abstract
    In this work, graphene oxide (GO) and Amino ethyl phosphonic acid (AEPA) functionalized graphene were synthesized using chemical method. In addition, reduced graphene was prepared by chemical and supercritical methods. Physical, chemical, morphological properties of as-synthesized materials were investigate using XRD, FTIR, RAMAN, UV, TEM, TGA, and BET. Thickness of monolayer GO which synthesized using Hummer’s method was evaluated 1 nm using AFM. FTIR and CHN results were affirmed the presence of AMPA onto graphene nanosheets. Adsorption properties of functionalized graphene for Th ions from aqueous solution was examined. Isotherm adsorption results demonstrated that maximum adsorption... 

    Technical Artifacts and Human Being: A Reflection on Verbeek’s Ideas

    , M.Sc. Thesis Sharif University of Technology Jalilian, Mohammad Sobhan (Author) ; Akbari Takhtameshlou, Javad (Supervisor)
    Abstract
    Technology, especially in recent centuries, has changed human form of life. Case studies show that there is a mutual relationship between human being and technology; Human is a technological being and technology is also a social entity. Therefore, trying to develop a conceptual framework to describe the important role of technical artifacts in our life can be regarded as a legitimate philosophical concern. Peter Paul Verbeek is one of the contemporary philosophers who take this concern seriously. He, by using the doctrines of The Empirical Turn in the philosophy of technology, has developed a lexical system, called post-phenomenology, to describe the role of Technology in human’s perception... 

    Investigation for Increasing the Life of Broaching Tools with Small Cross Section

    , M.Sc. Thesis Sharif University of Technology Haddad Mohammadabadi, Mohammad Mahdi (Author) ; Akbari, Javad (Supervisor)
    Abstract
    In the proccess of making key slots in lock parts, broaching is necessary. The only procedure or at least the best procedure for making the slots is broaching. High speed and precision, surface quality and the ability to create complicated surfaces in one step are the advantages that make broaching suitable for this product. The cost of tool maintainance and replacement is very important to make this process efficient economically, therefore, determining the factors affecting tool life are important for industries. The purpose of this study is to increase the life of narrow broaching tools. In other words, in this study, the purpose is to design and manufacture the tool in such a way that...