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    Investigation of E-Vtol Performance Parameters on the Characteristics of Civil Air-Taxi Network

    , M.Sc. Thesis Sharif University of Technology Kiani, Arash (Author) ; Malaek, Mohammad Bagher (Supervisor)
    Abstract
    Nowadays more than half of the world’s population lived in urban areas. That proportion is set to rise to 67% by 2050. This will cause urban mobility with serious problems. The concept of Urban Air Mobility (UAM) is proposed to avoid the problem to become a catastrophy. Due to environmental issues and also high operating costs, using copters as an air-taxi was not justifiable. As the technology in e-VTOL flourished, the desire of using of these vehicles in such a transportation system was increased. In this paper, besides previous investigations, the e-VTOL’s performance parameters’ influence on the characteristic of a civil air-taxi network is under investigation. In addition, this paper... 

    Gaining Competitive Advantage through Marketing Strategies in Container Terminal: A Case Study on Shahid Rajaee Port in Iran

    , M.Sc. Thesis Sharif University of Technology Cheraghi, Hossein (Author) ; Miremadi, Ali Reza (Supervisor)
    Abstract
    The competitiveness of a port convinced shipping lines and shippers with a significant basis in selecting a port. Port authorities and port operators can make use of the competitive advantage as a parameter for counter measures by grasping the advantages and disadvantages of the ports and be a prime factor of opportunities and threats of the ports. Ports have a significant role in today’s networked business environment. They are being regarded as hubs that are part of various logistic systems. The very essence of a seaport is to link maritime networks and land network. These networks for the port are means of analyzing its competitiveness. A port overall competitiveness is determined by it’s... 

    Study, Analysis & Optimizing The Process Of Approval, Design & Implementation Of Projects In The Iranian Oil Terminal Company(IOTC)

    , M.Sc. Thesis Sharif University of Technology Moosavi, Saeed (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Since the Iranian oil terminals company(I.O.T.C.) has been the main and strategic gateway of exporting petroleum in the country and plays an important role in the optimum continuity of national, regional and international energy supply chain and also conducting the needed projects whit a desirable quality and minimum time and cost has a prominent influence on steady continuity of manufacturing, importing and exporting of petroleum and gas production. The main purpose of doing this thesis is diagnosing the process of approval, design and implementation of projects in the I.O.T.C., Thus, whit regarding to the modern needs of implementing projects and the necessity of reviewing the structure... 

    Terminal Flight Path Optimization Pattern for High Traffic Airports for Noise

    , M.Sc. Thesis Sharif University of Technology Mostaghimi Rezazade, Saeed (Author) ; Malaek, Mohammad Bagher (Supervisor)
    Abstract
    The only problem in aviation and airport development is the noise print on population groups surrounding airports due to its high frequency it is so annoying for human ear. In order to overcome this problem technology has reached its edge and the only alternative is to deviate terminal flight path.In this thesis I tried find a pattern for optimizing terminal flight path considering a Boeing 737-800 taking off from Mehrabad airport’s runway 29. To do this we were in need of a huge database of airplane low speed model, geographic information and population knowledge.The common approaches used by FAA and other international organizations for modeling low speed flight were used. The influence of... 

    A Systematic Model to Determine Minimum Separation for VToL in Terminal Phase

    , M.Sc. Thesis Sharif University of Technology Adeli Koudehi, Ali (Author) ; Malaek, Mohammad Bagher (Supervisor)
    Abstract
    For the VTOL aircraft mission profiles, terminal phases are considered the most crucial and convoluted due to the interrelated aspects involved in transition from level flight into vertical motion. Flight safety is the trivial, yet essential requisite that should be satisfied during all flight phases. This paper aims to present a comprehensive model for determining a safe distance for urban VTOL air taxies during the landing phase through predicting possible conflictions and reducing this possibility by performing a conflict resolution maneuver while maintaining the flight safety requirements.The safe distance during landing is calculated based on a Monte-Carlo simulation which employs the... 

    Evaluation of Exerted Drag Force on Alkane Saturated Air Bubbles in Aqueous Solutions by Experimental Studies

    , M.Sc. Thesis Sharif University of Technology Rajabzadeh Dezfuli, Mehdi (Author) ; Bastani, Dariush (Supervisor) ; Lotfi, Marzieh (Supervisor)
    Abstract
    Interfacial phenomena and properties of interphase surfaces in dynamic mode play an important role in industrial processes that include gas-liquid and liquid-liquid multiphase flows. As well as, interface knowledge leads to better understanding of natural and fundamental phenomena. The present study has been performed for understanding about dynamic behavior of interphase surfaces in the presence of nanoparticles and hexane vapor in gas-liquid dispersion systems. In this research, rising bubble method has been used as one of the most conventional techniques. Accordingly, aqueous solutions of nanosilica were prepared in concentrations of 50, 100, 200, 400 and 1200 ppm as continuous phase... 

    The Simultaneous Berth and Quay Crane Scheduling

    , M.Sc. Thesis Sharif University of Technology Zokaei Nikoo, Maryam (Author) ; Salmasi, Naser (Supervisor)
    Abstract
    This study addresses the simultaneous berth and quay crane (QC) scheduling problem in a container terminal. The berths are considered as a continuous area and the vessels arrive dynamically. QCs are allowed to move to other vessels before completing the process on an assigned vessel.The objective function is determined based on the practical applications of the problem. It deals with minimization of sum of the completion time of vessels. In this research, a mathematical model has been developed for the research problem. According to NP-hardness of the research problem, two meta heuristic algorithms based on Tabu Search are proposed. To solve the problem, these methods have two layers with... 

    Combination of Linear MPC and Differential Game Theory for Optimal Cooperative Terminal Guidance Law with HIL Simulation

    , M.Sc. Thesis Sharif University of Technology Akbari, Mohammad Sadegh (Author) ; Nobahari, Hadi (Supervisor)
    Abstract
    In this research, a cooperative terminal guidance algorithm has been derived for simultaneous multi-interceptor collision with a target. This algorithm is obtained using the combination of model predictive control method and differential game theory. One of the features of this method is the calculation of the optimal guidance command in the form of an explicit relationship. Another feature of this method is its resistance to disturbances due to the use of differential game theory. The first innovation of this research is the use of this hybrid method to create a guidance algorithm, even in the non-cooperative guidance problem. The next innovation is in creating a cooperative terminal... 

    Introducing a Simulation-Based Model to Improve the Design and Layout of Workstations Inside Airport Terminals in Iran

    , M.Sc. Thesis Sharif University of Technology Amini Esfidvajani, Amin Mohammad (Author) ; Alvanchi, Amin (Supervisor)
    Abstract
    The airport terminal is difficult to plan and design due to the different components and the intricate complexity of its parts. At the airport terminal, we face a queue system which simulation is always a good way to analyze. In addition, computer simulation using modern softwares with the capability to model different types of systems, including the airport terminal, while being less realistic than analytical models, is less costly than operational Exercise.In this study, a supportive approach for better and specific management of Iranian airport terminal buildings with discrete-event simulation is proposed, considering the need for managing the airport terminals building in the country and... 

    Performance of UWB linked relay network with time-reversed transmission in the presence of channel estimation error

    , Article IEEE Transactions on Wireless Communications ; Volume 11, Issue 8 , 2012 , Pages 2958-2969 ; 15361276 (ISSN) Zeinalpour Yazdi, Z ; Nasiri Kenari, M ; Aazhang, B ; Sharif University of Technology
    2012
    Abstract
    In this paper, we present the bit error probability (BEP) of a relay network employing UWB links between its nodes. Since UWB systems can resolve many paths and are thus rich in multipath diversity, the use of the Rake diversity combining is very effective. However, because of the complexity, it is impractical in the scenarios with portable terminals or in the networks with multiple relays. Time-reversal technique, in which the transmitting nodes can do the pre-diversity filtering of UWB signal before transmission, is known as an approach to achieve the performance equivalent to the Rake combining without increasing the receiver complexity. The performance of such a network with simple... 

    Enhanced control of grid forming VSCs in a micro-grid system under unbalanced conditions

    , Article 9th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2018, 13 February 2018 through 15 February 2018 ; Volume 2018-January , April , 2018 , Pages 380-385 ; 9781538646977 (ISBN) Zarei, S. F ; Mokhtari, H ; Ghasemi, M. A ; SHarif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Due to the technical advances in power electronic industry, employing inverter-based distributed energy resources (IBDERs) are increased in electric power systems. Distributed generators (DGs) with the rating capacity of few megawatts are commonly connected to the distribution level of power systems which are inherently unbalanced. A cluster of IBDERs and loads form a small-scale grid called microgrid (MG) which can operate independent of the main grid. In a MG, grid forming voltage source converters (VSCs) are used to control the voltages and frequency of the MG. However, grid forming VSCs with conventional control schemes cannot do this task properly when the MG is unbalanced. In this... 

    Reliability evaluation of an HVDC transmission system tapped by a VSC station

    , Article IEEE Transactions on Power Delivery ; Vol. 25, issue. 3 , 2010 , p. 1962-1970 ; ISSN: 8858977 Zadkhast, S ; Fotuhi-Firuzabad, M ; Aminifar, F ; Billinton, R ; Faried, S. O ; Edris, A. -A ; Sharif University of Technology
    Abstract
    Reliability evaluation of multiterminal HVDC systems has received very little attention in the past. This paper presents reliability modeling and analysis of an HVDC transmission system incorporating a voltage-sourced converter (VSC) tapping station. The use of VSC tapping stations enables the supply of power along the route to areas with comparatively little consumption. In this paper, a comprehensive detailed reliability model is developed and then converted to a manageable and computationally efficient model. Using this equivalent reliability model, various reliability indices are calculated at the load point of the system and the impacts of the VSC tapping station on these indices are... 

    Reliability evaluation of an HVDC transmission system tapped by a VSC station

    , Article IEEE Transactions on Power Delivery ; Volume 25, Issue 3 , April , 2010 , Pages 1962-1970 ; 08858977 (ISSN) Zadkhast, S ; Fotuhi Firuzabad, M ; Aminifar, F ; Billinton, R ; Faried, S. O ; Edris, A. A ; Sharif University of Technology
    2010
    Abstract
    Reliability evaluation of multiterminal HVDC systems has received very little attention in the past. This paper presents reliability modeling and analysis of an HVDC transmission system incorporating a voltage-sourced converter (VSC) tapping station. The use of VSC tapping stations enables the supply of power along the route to areas with comparatively little consumption. In this paper, a comprehensive detailed reliability model is developed and then converted to a manageable and computationally efficient model. Using this equivalent reliability model, various reliability indices are calculated at the load point of the system and the impacts of the VSC tapping station on these indices are... 

    Estimating terminal velocity of rough cracks in the framework of discrete fractal fracture mechanics

    , Article Engineering Fracture Mechanics ; Volume 77, Issue 10 , 2010 , Pages 1516-1526 ; 00137944 (ISSN) Yavari, A ; Khezrzadeh, H ; Sharif University of Technology
    2010
    Abstract
    In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed  

    Dynamic Gossip

    , Article Bulletin of the Iranian Mathematical Society ; Volume 45, Issue 3 , 2019 , Pages 701-728 ; 10186301 (ISSN) van Ditmarsch, H ; van Eijck, J ; Pardo, P ; Ramezanian, R ; Schwarzentruber, F ; Sharif University of Technology
    Springer International Publishing  2019
    Abstract
    A gossip protocol is a procedure for spreading secrets among a group of agents, using a connection graph. The goal is for all agents to get to know all secrets, in which case we call the execution of the protocol successful. We consider distributed and dynamic gossip protocols. In distributed gossip, the agents themselves instead of a global scheduler determine whom to call. In dynamic gossip, not only secrets are exchanged but also telephone numbers (agent identities). This results in increased graph connectivity. We define six such distributed dynamic gossip protocols, and we characterize them in terms of the topology of the graphs on which they are successful, wherein we distinguish... 

    Multicast beamformer design for coded caching

    , Article IEEE International Symposium on Information Theory - Proceedings, 17 June 2018 through 22 June 2018 ; Volume 2018-June , 2018 , Pages 1914-1918 ; 21578095 (ISSN) ; 9781538647806 (ISBN) Tolli, A ; Shariatpanahi, S. P ; Kaleva, J ; Khalaj, B ; Sharif University of Technology
    Abstract
    A single cell downlink scenario is considered where a multiple-antenna base station delivers contents to cache-enabled user terminals. Using the ideas from multi-server coded caching (CC) scheme developed for wired networks, a joint design of CC and general multicast beamforming is considered to benefit from spatial multiplexing gain, improved interference management and the global CC gain, simultaneously. The proposed multicast beamforming strategies utilize the multiantenna multicasting opportunities provided by the CC technique and optimally balance the detrimental impact of both noise and inter-stream interference from coded messages transmitted in parallel. The proposed scheme is shown... 

    Linear multicast beamforming schemes for coded caching

    , Article 52nd Asilomar Conference on Signals, Systems and Computers, ACSSC 2018, 28 October 2018 through 31 October 2018 ; Volume 2018-October , 2019 , Pages 172-176 ; 10586393 (ISSN); 9781538692189 (ISBN) Tolli, A ; Kaleva, J ; Shariatpanahi, S. P ; Khalaj, B ; Matthews M. B ; Sharif University of Technology
    IEEE Computer Society  2019
    Abstract
    A single cell downlink scenario is considered, where a multiple-antenna base station delivers contents to cache-enabled user terminals. Depending on the available degrees of freedom, several multicast messages are transmitted in parallel to distinct subsets of users. In the multicast beamformer design, we restrict ourselves to linear receiver implementation, which does not require successive interference cancellation unlike in the more optimal baseline scheme. With a small loss in performance, the complexity of both the receiver and transmitter implementation can be significantly reduced. © 2018 IEEE  

    Analysis and enhancement of low-voltage ride-through capability of brushless doubly fed induction generator

    , Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 3 , March , 2013 , Pages 1146-1155 ; 02780046 (ISSN) Tohidi, S ; Oraee, H ; Zolghadri, M. R ; Shao, S ; Tavner, P ; Sharif University of Technology
    2013
    Abstract
    This paper discusses the dynamic behavior of the brushless doubly fed induction generator during the grid faults which lead to a decrease in the generator's terminal voltage. The variation of the fluxes, back EMFs, and currents are analyzed during and after the voltage dip. Furthermore, two alternative approaches are proposed to improve the generator ride-through capability using crowbar and series dynamic resistor circuits. Appropriate values for their resistances are calculated analytically. Finally, the coupled circuit model and the generator's speed and reactive power controllers are simulated to validate the theoretical results and the effectiveness of the proposed solutions. Moreover,... 

    Rapid depressurization dynamics of solid propellant rocket motors

    , Article 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cincinnati, OH, 8 July 2007 through 11 July 2007 ; Volume 8 , 2007 , Pages 7871-7879 ; 1563479036 (ISBN); 9781563479038 (ISBN) Tahsini, A. M ; Farshchi, M ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2007
    Abstract
    Transient internal ballistics of a solid propellant rocket motor during rapid depressurization due to opening of an auxiliary nozzle for active thrust termination has been considered in this work. Prediction of thrust termination and reversing dynamics is required for successful stage separation in multi-stage rockets. Quasi one-dimensional unsteady Euler equation with a transient propellant burning model that accounts for the effects of time rate of change of the chamber pressure on the burning rate have been used to simulate the internal ballistics of a rocket motor. The compressible convective flow solver used in this study is based on Roe's scheme. The effects of rapid chamber pressure... 

    Thrust termination dynamics of solid propellant rocket motors

    , Article Journal of Propulsion and Power ; Volume 23, Issue 5 , 2007 , Pages 1141-1142 ; 07484658 (ISSN) Tahsini, A. M ; Farshchi, M ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2007
    Abstract
    Thrust termination dynamics of a solid propellant rocket motor that is crucial to the performance of the rocket has been analyzed. Active thrust termination or reversing of a separating motor facilitate the staging process and enhance the performance of a multistage rocket. This can be achieved by opening a secondary nozzle located on the motor head and causing rapid depressurization of the motor chamber. The strong dependence of the solid propellant burning rate on the chamber pressure causes a transient nonlinear behavior that can result in premature dynamic extinguishments of the motor. It was confirmed that there is a maximum achievable level of equilibrium reverse thrust due to...