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    Feasibility study of Foam Concrete production

    , M.Sc. Thesis Sharif University of Technology Koohestani, Mostafa (Author) ; Shadrokh, Shahram (Supervisor)
    Abstract
    Foam concrete is a new covering layer that can be used for several purposes in civil constructions and because of its unique physical specifications, produces a light concrete in which is isolated against thermal conductivity ,with required strength and favorite quality.This cover is made of cement , sand ,water and foam(chemical substance that produces foam) . The foam is mixed with water in a special machine (mixer) with a high speed centrifugal rotation and produces very small stable bubbles called foam. While cement and sand are mixed in special mixer, makes a fluent concrete that can be used in place, metallic or plastic molds. After dehydration, in accordance with percentage of... 

    Photocatalytic degradation of methyl orange and cyanide by using TiO2/CuO composite

    , Article Desalination and Water Treatment ; Volume 57, Issue 46 , 2016 , Pages 22029-22038 ; 19443994 (ISSN) Koohestani, H ; Sadrnezhaad, S. K ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    In this study, the effect of adding 5–12.5 wt% CuO to TiO2 on photocatalytic properties of the nano-composite TiO2/CuO was investigated. The products were characterized by X-ray diffractometer, SEM, Brunauer–Emmett–Teller (BET), and DRS. BET-specific surface area of the TiO2/CuO composites was lower than that of the pure TiO2. Incorporation of CuO into TiO2 shifted absorption spectra to the visible region. As the CuO content increased from 0 to 12.5%, a clear decrease in optical band gap from 2.95 to 2.30 eV was observed. The photocatalytic performance was determined by methyl orange degradation and cyanide photo-oxidation under ultraviolet irradiation. However, the excessive incorporation... 

    Photocatalytic activity of immobilized geometries of tio2

    , Article Journal of Materials Engineering and Performance ; Volume 24, Issue 7 , July , 2015 , Pages 2757-2763 ; 10599495 (ISSN) Koohestani, H ; Sadrnezhaad, S. K ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    Photocatalysts that are used for waste water treatment are often suspended in the waste water during processing and then must be removed from the water after treatment. To reduce the post-degradation expenses and time, separation is facilitated by an immobilization process. The effect of immobilized TiO2 geometries on the photocatalytic behavior of the photocatalyst is investigated in this work. Powder, fiber, film, and network-shaped TiO2 nanocatalysts were produced by using different templates. The cellulose fiber and ceramic templates were used as substrates for fiber and film/network geometry production. The products were characterized by x-ray diffraction (XRD),... 

    Improvement in TiO2 photocatalytic performance by ZrO2 nanocompositing and immobilizing

    , Article Desalination and Water Treatment ; Volume 57, Issue 58 , 2016 , Pages 28450-28459 ; 19443994 (ISSN) Koohestani, H ; Sadrnezhaad, S. K ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    In this work, the effect of addition of ZrO2 to TiO2 and catalyst geometry on photocatalytic properties of the nanocomposite TiO2/ZrO2 was investigated. The traditional use of powdery photocatalyst for the degradation of organic compounds has post-treatment problems which means much higher time and costs. A novel method to minimize these problems is immobilization by insertion onto an inert substrate. Several geometries of TiO2–10%ZrO2 (T-10Z) nano-photocatalysts (powder, fiber, film, and network-shaped) were produced using different templates. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller, and diffuse reflectance... 

    Improvement of Photocatalytic Efficiency of Nano-Titania Compsites

    , Ph.D. Dissertation Sharif University of Technology Koohestani, Hassan (Author) ; Sadrnezhad, Khatiboleslam (Supervisor)
    Abstract
    Semiconductor-based photo catalysts, titanium dioxide (TiO2) especially, have been extensively studied for the oxidative photo destruction of organic pollutants in wastewaters and hydrogen production as a green energy source. Much effort has been made to remove the restrictions on the use of TiO2 and challenges related to the recovery of powdery photocatalysts. In this study, copper oxide (CuO) and Zirconium oxide (ZrO2) were used to synthesize nanocomposites. Composition of TiO2/CuO and TiO2/ZrO2 with different weight percentages of second dioxide was synthesized by chemical methods and structural properties of samples were studied by X-ray diffraction and scanning electron microscopy.... 

    Investigation of photocatalytic performance of TiO2 network and fiber geometries

    , Article Desalination and Water Treatment ; Volume 57, Issue 50 , 2016 , Pages 23644-23650 ; 19443994 (ISSN) Koohestani, H ; Sadrnezhaad, S. K ; Kheilnejad, A ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    In typical photocatalytic processes slurry reactors are used in which catalyst particles have to be separated from the solution after the process ends which means much higher time and costs. Hence, immobilizing process is carried out on the catalyst to overcome this problem. In this work, fiber and network geometries were produced by particle precipitation on substrates. The obtained structures were characterized by XRD, SEM, and Brunauer–Emmett–Teller analyses. Photocatalytic performance of the samples was investigated by methyl orange degradation and also by hydrogen generation from water/methanol splitting. From the SEM images, the size range of the TiO2 particles in the network... 

    Investigating the effect of ultrasound intensity on the magnetic properties of magnetite nanostructures synthesized by sonochemical method

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 36, Issue 6 , 2023 , Pages 1034-1039 ; 1728144X (ISSN) Hassanjani Roshan, A ; Vaezi, M. R ; Koohestani, H ; Cheraghi, F ; Sharif University of Technology
    Materials and Energy Research Center  2023
    Abstract
    In this article, the synthesis of magnetite nanostructures was successfully carried out by the sonochemical process. In this method, stoichiometric amount of iron chlorides (FeCl3.6H2O and FeCl2.4H2O), ammonia (NH3) and polyvinylpyrolidone (PVP) were used to synthesize pure Fe3O4 nanoparticles. The effect of initial sonication power of the ultrasonic device on the size and morphology of the final products as one of the effective parameters was investigated. For this, the initial power of the sonicator was evaluated at 90, 70, 50 and 30 W at 40°C. Characterization of Fe3O4 nanoparticles was done by transmission electron microscope (TEM) and X-ray powder diffraction (XRD) and its magnetic... 

    Fe 50Co 50 nanoparticles via self-propagating high-temperature synthesis during milling

    , Article Powder Technology ; Volume 208, Issue 3 , 2011 , Pages 623-627 ; 00325910 (ISSN) Azizi, A ; Yourdkhani, A ; Koohestani, H ; Sadrnezhaad, S. K ; Asmatulu, R ; Sharif University of Technology
    2011
    Abstract
    Self-propagating exothermic reactions during mechanical milling of FeCl 3/CoCl 2 mixture together with sodium seeds resulted in formation of Fe 50Co 50 nanoparticles. Highly exothermic reactions resulted in temperature raise and formation of Fe 50Co 50 phase within the first 5min; however Fe 50Co 50 single-phase was obtained after 30min of milling. The products were characterized by XRD, SEM, EDS, TEM and VSM. Obtained results showed that both milling time and NaCl salt matrix affected the size, morphology, microstructure and magnetic properties of the produced particles  

    Structural Design of a Launch Vehicle with Reusable First Stage

    , M.Sc. Thesis Sharif University of Technology Hassan Jamaklu (Author) ; Haddadpour, Hassan (Supervisor)
    Abstract
    Aerodynamics loads and aeroheating during reentry, are one of the challenging issues in designing One of the main challenges in the design and application of reusable spacecrafts is the aerodynamic and thermal loads acting on their structures during reentry into the atmosphere. For this reason, all the concepts/prototypes presented in the 20th century were either not fully reusable, or were partially canceled, or did not have economic justification. In this report, the aerodynamic loads on the first stage of a launch vehicle during the launch and return phases have been investigated. Due to the fact that the main part of the first stage of the vehicle includes fuel and oxidizer tanks, the... 

    Optimal Trajectory Correction for Hazardous Near-Earth Asteroids

    , M.Sc. Thesis Sharif University of Technology Farsi, Salman (Author) ; Zohoor, Hassan (Supervisor) ; Sayyadi, Hassan (Supervisor)
    Abstract
    The collision of moderately large asteroids and comets also referred to as Near-Earth Objects (NEO's) with earth would have catastrophic consequences. Such events have occurred in the past and may occur again in the future. However, for the first time in known history, humanity may have the technology required to counter this threat. Methods studied for mitigation of this hazard are based on deflecting asteroid's trajectory and are normally divided into two basic categories: high energy impulsive methods, and long-duration low-thrust methods. Two parts of mission to be optimized are the trajectory of spacecraft to reach the target and the deflection strategy which could be analyzed by the... 

    A revised version of ACO for cutting stock problem [electronic resource]

    , Article International Journal of Industrial Engineering ; Vol 15, No 4 (2008), Pages 341-348 Eshghi, K. (Kourosh) ; Javanshir, Hassan ; Sharif University of Technology
    Abstract
    The one-dimensional cutting stock problem has many applications in industries and during the past few years has been one of the centers of attention among the researchers in the field of applied operations research. In this paper, a revised version of Ant Colony Optimization (ACO) technique is presented to solve this problem. This paper is a sequel to the previous ACO algorithm presented by the authors. In this algorithm, according to some probabilistic rules, artificial ants will select cutting patterns and generate a feasible solution. Computational results show the high efficiency and accuracy of the proposed algorithm for solving one- dimensional cutting stock problem  

    Control of Car-Like Multi Robots for Following and Hunting of Moving Target

    , M.Sc. Thesis Sharif University of Technology Kouhi Gilvan, Hamed (Author) ; Sayyaadi, Hassan (Supervisor) ; Salarieh, Hassan (Co-Advisor)
    Abstract
    The main purpose of the present thesis is to establish a decentralized controller for some car–like multi robots to follow and hunt moving targets. Robots are very similar to actual cars considering geometric dimensions, mass and moment of inertia and so on; and outputs of the controller are steering-wheel and driving-wheel torques appropriately. Dynamics of the moving target is so that it escapes from the robots. Robots are equipped with antenna for getting wireless sensory signals, including range and bearing sensors. Kalman filter is used for estimation the target relative position and speed and robots state variables. The controller is designed for doing the above mentioned group... 

    Effects of COVID-19-related psychological distress and anxiety on quality of sleep and life in healthcare workers in Iran and three European countries

    , Article Frontiers in Public Health ; Volume 10 , 2022 ; 22962565 (ISSN) Zangeneh Soroush, M ; Tahvilian, P ; Koohestani, S ; Maghooli, K ; Jafarnia Dabanloo, N ; Sarhangi Kadijani, M ; Jahantigh, S ; Zangeneh Soroush, M ; Saliani, A ; Sharif University of Technology
    Frontiers Media S.A  2022
    Abstract
    Introduction: The COVID-19 pandemic has considerably affected human beings most of whom are healthcare workers (HCWs) combating the disease in the front line. Methods: This cross-sectional study aims to explore the effects of stress and anxiety caused by COVID-19 on the quality of sleep and life in HCWs, including physicians, nurses, and other healthcare staff. In this global study, we asked 1,210 HCWs (620 and 590 volunteers from Iran and European countries, including Germany, the Netherlands, and Italy, respectively), who age 21–70, to participate in the test. Several measures of COVID-related stress, anxiety, sleep, and life quality, including the 12-item General Health Questionnaire... 

    Stock Price Forecasting Using Neural Networks and Fuzzy Logic

    , M.Sc. Thesis Sharif University of Technology Alizadeh, Parisa (Author) ; Shavandi, Hassan (Supervisor)
    Abstract
    This research proposes a novel hybrid method for stock price index forecasting relying on technical analysis, the fundamental analysis of capital market, neural networks technology, and fuzzy logic. The new method shows a good performance comparing complicated and time-consuming forecasting methods. Several factors influence stock price; for example, an important one is the previous trend of stock price. Fortunately, by developing technical analysis and introducing the various indices of this method the maximum use of historical data is made in order to forecast future prices. Another kind of factors is macro-economic variables that their influence on the long-term trends of the stock... 

    Control of a Group of Mobile Manipulators for Cooperative object Transportation

    , M.Sc. Thesis Sharif University of Technology Babaee, Mohammad (Author) ; Sayyadi, Hassan (Supervisor)
    Abstract
    In this thesis control of wheeled mobile manipulators for cooperative object transportation is investigated. Full dynamic model of a mobile manipulator with a three wheeled mobile base and a three DOF manipulator is derived using Gibbs-Appell method. Input-output linearization technique is used to control individual robots. Transporting the object is divided into two steps, first robots use a decentralized behavior-based method to approach and surround the object. Then virtual structure method is used to control the robots to transport the object cooperatively. Simulation results with three robots handling an object are presented to show the effectiveness of proposed method  

    Dynamic and Control of Tethered Satellite Systems

    , M.Sc. Thesis Sharif University of Technology Yousefian, Peyman (Author) ; Salarieh, Hassan (Supervisor)
    Abstract
    In this work dynamic behavior of a two body TSS with main satellite as rigid body is studied and effects of tether elasticity and tension on the satellite dynamic are indicated in station keeping phase and circular orbit. Also a simplified modeling is introduced which could be used in nonlinear controller design. Lagrange and extended Lagrange method is used to derive equations of motion. It is shown that longitudinal vibration of tether has small effect on satellite attitude and angular velocity and because of high frequency it can be decoupled from satellite dynamic. In the simplified model, orbital motion is decoupled from equations of TSS and main satellite dynamic. Effect of decoupling... 

    Analysis of Control of Nonlinear Switched Systems

    , M.Sc. Thesis Sharif University of Technology Toorani, Amin (Author) ; Zohoor, Hassan (Supervisor)
    Abstract
    Separate analysis of modern systems by continuous or discrete theories is not possible, because they cannot solely express the detailed descriptions of a system. As a result of this, researchers are motivated to study hybrid systems. Specific class of hybrid systems which consists of several continuous subsystems and a rule that specifies how to switch between them, is called a switched system. Recently, many studies have been done on the stability and control of switched systems. In this regard, the goal of present study is presenting applications of switched systems using two control methods. The first application is control of a chemical reactor system with multiple modes. We presented... 

    Design and Analysis of a Cable Based Robot Similar to a Human Hand

    , M.Sc. Thesis Sharif University of Technology Abyaneh, Soroush (Author) ; Zohoor, Hassan (Supervisor)
    Abstract
    The application of manipulators is becoming more and more popular in objects handling especially when it is desired to have access to remote areas in destructive or hazardous taskspaces. For this purpose, a hand-like mechanism must be designed to be used as an end-effector, which can grasp objects. In this paper a cable driven grasping mechanism has been presented. In the proposed mechanism each finger consists of three phalanxes which are actuated by a single motor. Also, locking and unlocking constraints are used in the mechanism in order to generate an anthropomorphic motion, in which, the order of reaching phalanxes to the object is sequential, in such a way that each phalanx starts... 

    Data Integration with Multiple Ontologies in Semantic Sensor Web

    , M.Sc. Thesis Sharif University of Technology Sadeghi, Shahrouz (Author) ; Abolhassani, Hassan (Supervisor)
    Abstract
    Sensor Observation Service (SOS) which is defined by Open Geospatial Consortium (OGC) Sensor Web Enablement group is a Web service specification in order to standardize the way sensors and sensor data are discovered and accessed on the Sensor Web. Multiple instances of this service can be implemented around the world, providing huge amount of data every moment. Each of these services operates in specific domain of knowledge (thematic), spatial and temporal dimensions. One way to reveal the underlying data over all of them is to provide an architecture for data integration to allow the user to query sensor data without the knowledge of the infrastructure components. In this research, a novel... 

    Crack Detection on Rotary Elements Using Vibration Analysis

    , M.Sc. Thesis Sharif University of Technology Ari, Mostafa (Author) ; Sayyaddi, Hassan (Supervisor)
    Abstract
    Rotating machinery are found in most industrial units, that are highly susceptible to transverse cross sectional cracks due to fatigue. The vibration pattern of a rotor system reflects the mechanical parameter changes in the system. These vibrations can be used for identifying the cracks and appropriate actions can be taken to prevent more damage to the system. The dynamic behavior of cracked rotor is a subject of considerable current interest. Several researchers have developed models of cracked rotor systems. Therefore, In this thesis, the influence of the presence of transverse cracks in a simple Jeffcott rotor is analyzed. In first, on the basis of fracture mechanics, the direct and...