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    Analytical and Numerical Investigation of Fuel Spray Characteristics in a Direct Injection Engine

    , M.Sc. Thesis Sharif University of Technology Farajimoghaddam, Farhad (Author) ; Saeedi, Mohammad Hassan (Supervisor)
    Abstract
    With the increasing number of applications in internal combustion engines, environmental impact and air pollution caused by emissions has been much attention. Natural gas is a promising fuel for limiting pollution laws in many countries. The use of fuel with a higher ratio of hydrogen gas to carbon pollution reduction motor. In this context and with regard to development policy and also due to the diversity basket NGV fuel, fuel injection, has been modeled analytically and numerically in a direct injection engine. In this study, an analytical model for spray injection fuel delivery and is dissolved. The resolution of the method of separation of variables is taken. The effect of the nozzle... 

    Control Design for Nonlinear Stochastic Processes in the Presence of Output Constraint

    , M.Sc. Thesis Sharif University of Technology Esfandiar, Khadijeh (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    This work addresses adaptive neural control for a class of stochastic nonlinear systems in the nonstrict-feedback form. By introducing a nonlinear mapping, the output-constrained stochastic system transformed into a new system without constraint. The systems under study is subject to state time delay, input nonlinearity, unavailable states, unknown dynamics and actuator failure. The appropriate Lyapunov-Krasovskii functionals is used to compensate the time-delay effects, the neural network is used to approximate the unknown nonlinearities, the linear state observer is constructed to estimate the unmeasured states, and a variable separation method is used to deal with the difficulty caused by... 

    Design and analysis of a novel two DOF thermal micromanipulator

    , Article 2011 IEEE International Conference on Mechatronics, ICM 2011 - Proceedings ; 2011 , pp. 654-659 ; ISBN: 9781612849836 Pourzand, H ; Ghaemi, R ; Alasty, A ; Sharif University of Technology
    Abstract
    In this paper, a novel thermal microactuator is designed which is capable of producing bi-directional lateral and rotational output and one of its applications as a two DOF micromanipulator is shown. Also, by carefully choosing the doping level, temperature distribution is determined by considering the dependency of silicon's resistivity and conductivity to temperature. Using variable separation method an equation in terms of elliptic integrals is reached and after imposing boundary conditions the exact temperature distribution is obtained numerically. Currents at each branch is updated due to the last temperature distribution and this process is repeated several times until the final... 

    Exploring contraction–expansion inertial microfluidic-based particle separation devices integrated with curved channels

    , Article AIChE Journal ; Volume 65, Issue 11 , 2019 ; 00011541 (ISSN) Shamloo, A ; Abdorahimzadeh, S ; Nasiri, R ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    Abstract
    Separation of particles or cells has various applications in biotechnology, pharmaceutical and chemical industry. Inertial cell separation, in particular, has been gaining a great attention in the recent years since it has exhibited a label-free, high-throughput and efficient performance. In this work, first, an inertial contraction–expansion array microchannel device, capable of passively separating two particles with diameters of 4 and 10 μm, was numerically studied. Then, the validated model was combined with curved geometries in order to investigate the effect of curve features on the separation process. The overall purpose was to investigate the interaction between the two different... 

    LPG mass separation by vortex tube cascade and its economics

    , Article Applied Thermal Engineering ; Volume 148 , 2019 , Pages 1139-1147 ; 13594311 (ISSN) Majidi, D ; Alighardashi, H ; Farhadi, F ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In the present experimental study, the effect of operating parameters such as inlet and outlet pressure as well as inlet temperature on the mass separation capability of vortex tubes (VTs) for a gas mixture is investigated. Specifically, concentrating heavier components of a gas mixture in the hot outlet stream is considered. Proposing a semi-empirical index from the experimental study, the simulation of different arrangements of VTs, and the effect of recycling a portion of the hot outlet stream on its mass separation performance are investigated. Moreover, the proposed separation method by VTs is economically compared with commonly used methods by distillation columns and two-phase... 

    Control of Nonlinear Systems With Predefined Output Transient Performance

    , M.Sc. Thesis Sharif University of Technology Kamal Amiri, Ali (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    This project is aimed to design a controller for nonlinear systems that satisfy a prescribed performance while guaranteeing close-loop stability. To do this, the controller must be designed in such a way that the transient response of the system has had these performance indices and does not exceed them. These performance indices predefine some constraints for systems’ output.A comprehensive form for the model system, the unknown dynamics of the system, consideration of a variety of constraints on the system input, usage of the time-finite method for the residence time and consideration of just one tuning parameter to reduce the computation load, are among the other benefits for the proposed... 

    A new nonlinear sparse component analysis for a biologically plausible model of neurons

    , Article Neural Computation ; Volume 31, Issue 9 , 2019 , Pages 1853-1873 ; 08997667 (ISSN) Heidarieh, S. M ; Jahed, M ; Ghazizadeh, A ; Sharif University of Technology
    MIT Press Journals  2019
    Abstract
    It is known that brain can create a sparse representation of the environment in both sensory and mnemonic forms (Olshausen & Field, 2004). Such sparse representation can be combined in downstream areas to create rich multisensory responses to support various cognitive and motor functions. Determining the components present in neuronal responses in a given region is key to deciphering its functional role and connection with upstream areas. One approach for parsing out various sources of information in a single neuron is by using linear blind source separation (BSS) techniques. However, applying linear techniques to neuronal spiking activity is likely to be suboptimal due to inherent and...