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    All-Optical Scalable Multi-stage Interconnection Network for Data Centers

    , M.Sc. Thesis Sharif University of Technology Movahederad, Mahdieh (Author) ; Koohi, Somayeh (Supervisor)
    Abstract
    According to the increasing amount of data exchanged among data centers, the need for speeding up and bandwidth and reduced power consumption has been increased. The information show that about 77% of the data is moved into the data centers. On the other hand, 10% of data center’s power consumption is used to data transmission. Improving the interconnection network of data centers can play an important role in reducing power consumption and speeding up. In recent years, optical interconnects have gained attention as a promising solution. Nevertheless, offering an all-optical and efficient architecture is an important issue. In this study, we intend to provide a multi-stage, all-optical... 

    Adopting Dynamic Topology for Energy Management in Optical Interconnection Networks in Data Centers

    , M.Sc. Thesis Sharif University of Technology Rezaei, Negar (Author) ; Koohi, Somayeh (Supervisor)
    Abstract
    Today with the deployment of cloud computing and web applications; We need to have powerful datacenters with provisioning high bandwidth. Current data centers with electronic network interconnects, using excessive power to provisioning requisite bandwidth. Nevertheless, interconnecting networks in data centers isn’t in maximum efficiency and many components of them aren't used efficiently. So it is necessary to use an optical network with dynamic provisioning variable bandwidth and energy management. In this approach, our proposed architecture is designing topology with adopting dynamically for energy management in optical interconnect networks in data centers. To achieve this we can study... 

    Feasibility Analysis of Backflow Detection in Lobe Blowers in Khuzestan Steel Plant using Condition Monitoring Techniques

    , M.Sc. Thesis Sharif University of Technology Monazami, Ali (Author) ; Behzad, Mehdi (Supervisor) ; Mohammadi, Somayeh (Supervisor)
    Abstract
    Lobe blowers are positive displacement machines (PDM) that are widely used in various industries. The efficiency of lobe blowers depends on the clearance between fixed and moving parts. If the clearance between the parts increases, backflow occurs, which means that the flow returns from the high-pressure zone of the outlet to the low-pressure zone of the inlet, and this makes the blower not have the initial efficiency and work with a lower capacity than its design. This research is carried out with the aim of checking the feasibility of backflow detection using two condition monitoring methods, including ultrasonic and thermography techniques. The sample of this research includes seven... 

    Comparison of Vibration and Ultrasonic Signal Performance in Predicting the Remaining Useful Life of Rolling Element Bearings

    , M.Sc. Thesis Sharif University of Technology Yousefizadeh, Emadaddin (Author) ; Behzad, Mehdi (Supervisor) ; Mohammadi, Somayeh (Supervisor)
    Abstract
    The prediction of Remaining Useful Life (RUL) has become a critical tool in enhancing the availability of rotating machinery. By knowing the remaining time before a bearing failure occurs during operation, significant reductions in unplanned production downtimes and associated costs can be achieved. In this study, by analyzing the time signals of vibration and ultrasonic data related to the bearing of a 4.1 MW electromotor from installation to replacement, and by investigating the behavior trends and correlation between extracted features, RMS has been ultimately identified as the health indicator in both vibration and ultrasonic techniques for monitoring the bearing’s condition. First,... 

    , M.Sc. Thesis Sharif University of Technology Seif, Mohammad Reza (Author) ; Behzad, Mehdi (Supervisor) ; Mohammadi, Somayeh (Supervisor)
    Abstract
    Bearings play a critical role in the functionality of rotating equipment across various industries, accounting for approximately 50% of equipment failures due to bearing malfunctions. Accurate life prediction of bearings is essential not only for preventing unexpected breakdowns and subsequent damage but also for minimizing unnecessary replacements of functional bearings, which can lead to increased operational costs. With the rise of artificial intelligence, numerous predictive models have been developed; however, many of these require extensive datasets, which are often unavailable in industrial settings. Data collection is typically irregular, based on the sensitivity of the equipment,... 

    Identification of Possible Failures in Online Data of Gas Turbines based on Information Fusion using Artificial Intelligence

    , M.Sc. Thesis Sharif University of Technology Haghighat Shoar, Amin (Author) ; Behzad, Mehdi (Supervisor) ; Mohammadi, Somayeh (Supervisor)
    Abstract
    Gas turbines' safe operation depends on the monitoring of performance thresholds and equipment limitations. This is accomplished through online data monitoring using sensors, with the collected data processed by monitoring software supplied by turbine manufacturers to extract information on operating conditions. The thresholds are usually set during manufacturing under standard conditions and saved in the control software. As the turbine ages and undergoes maintenance, these thresholds and operating conditions may change, requiring expert analysis to determine safe operating limits. Technological advancements have enabled the processing of operational data to establish patterns and create... 

    Economic complexity and the dynamics of regional competitiveness a systematic review

    , Article Competitiveness Review ; Volume 33, Issue 4 , 2023 , Pages 711-744 ; 10595422 (ISSN) Bahrami, F ; Shahmoradi, B ; Noori, J ; Turkina, E ; Bahrami, H ; Sharif University of Technology
    Emerald Publishing  2023
    Abstract
    Purpose: This study aims to systematically review the economic complexity literature to advance the knowledge on its contribution to building regional competitiveness. Design/methodology/approach: In this study, we did a systematic review of 111 relevant papers. In this regard, we did a thematic analysis on all the collected papers, which led to a two-level processed approach. In the first level, the contributions of the reviewed articles have been classified into three main streams. In the second level, the findings under each contribution category are analyzed and explained. This approach led to a thematic network demonstrating economic complexity and the dynamics of regional... 

    Reliability and Redundancy Analysis at a Methanol Plant in the Khark Petrochemical Complex: Investigation, Modeling, and Improvement

    , M.Sc. Thesis Sharif University of Technology Modabber, Morteza (Author) ; Mohammadi, Somayeh (Supervisor) ; Saniee Monfared, Mohammad Ali (Supervisor)
    Abstract
    Today, reliability assessment of production systems is crucial for ensuring continuous production and minimizing operational and maintenance (O&M) costs. One way to assess reliability at the system level is to create a reliability block diagram (RBD) and estimate the failure rates of equipment over their operational periods. This approach has been utilized in this thesis, focusing on assessment of the reliability of various units within the methanol plant at Khark Petrochemical Complex. In this context, understanding the condition of the equipment criticality is essential for constructing the reliability block diagram. The Crespo model and total criticality per risk (CTR) measure have been... 

    The Investigation of the Effectiveness of Engine Oil Filter Particle Analysis in Enhancing the Efficiency of Diesel Engine Condition Monitoring Programs

    , M.Sc. Thesis Sharif University of Technology Samaeinejad, Saman (Author) ; Behzad, Mehdi (Supervisor) ; Masoodi, Alireza (Supervisor) ; Mohammadi, Somayeh (Co-Supervisor)
    Abstract
    Over the years, as machines have been invented, their maintenance and repair have consistently been regarded as critical concerns. Oil analysis techniques are an effective method for monitoring the condition of mechanical equipment. Since filters in these devices continually absorb and remove a significant portion of particles from the lubricant, the selection of appropriate filters is crucial. While filters positively affect machine performance, they can also negatively impact oil condition monitoring. To mitigate this negative effect and improve the predictive accuracy of equipment health monitoring, oil filter analysis was conducted. In this research, analytical ferrography tests were... 

    Game theoretic based charging strategy for plug-in hybrid electric vehicles

    , Article IEEE Transactions on Smart Grid ; Vol. 5,Issue. 5 , 2014 , pp. 2368-2375 ; ISSN: 19493053 Bahrami, S ; Parniani, M ; Sharif University of Technology
    2014
    Abstract
    In the future smart grids, Plug-in Hybrid Electric Vehicles (PHEVs) are seen as an important means of transportation to reduce greenhouse gas emissions. One of the main issues regarding to this sort of vehicles is managing their charging time to prevent high peak loads over time. Deploying advanced metering and automatic chargers can be a practical way not only for the vehicle owners to manage their energy consumption, but also for the utilities to manage the electricity load during the day by shifting the charging loads to the off-peak periods. Additionally, an efficient charging schedule can reduce the users' electricity bill cost. In this paper we propose a new practical demand response... 

    Stability of chiral states, role of intermolecular interactions and molecular parity violation

    , Article Computational and Theoretical Chemistry ; Volume 978, Issue 1-3 , 2011 , Pages 84-87 ; 2210271X (ISSN) Bahrami, M ; Shafiee, A ; Sharif University of Technology
    2011
    Abstract
    We study the problem of stability of chiral states, also known as problem of chirality, within the framework of a two-dimensional approximation of a symmetric double-well potential. We show how the symmetry breaking of the potential due to the molecular parity violation can stop the tunneling in a coherent way, accordingly stabilize the chiral states. Then, we use the quantum Brownian motion within a linear Lindblad-type equation to model how the intermolecular interactions make the tunneling incoherent, thus inducing a racemization by dephasing. Finally, we investigate the normal physical conditions where the dephasing racemization does not suppress the effects of the molecular parity... 

    Tunneling properties of nonplanar molecules in a gas medium

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 84, Issue 6 , 2011 ; 10502947 (ISSN) Bahrami, M ; Bassi, A ; Sharif University of Technology
    2011
    Abstract
    We propose a simple, general, and accurate formula for analyzing the tunneling between classical configurations of a nonplanar molecule in a gas medium, as a function of the thermodynamic parameters of the gas. We apply it to two interesting cases: (i) the shift to zero frequency of the inversion line of ammonia, upon an increase in the pressure of the gas; and (ii) the destruction of the coherent tunneling of D 2S 2 molecules in a He gas. In both cases, we compare our analysis with previous theoretical and experimental results  

    Circuit design to improve security of telecommunication devices

    , Article 2015 IEEE Conference on Technologies for Sustainability, SusTech 2015, 30 July 2015 through 1 August 2015 ; Aug , 2015 , Pages 171-175 ; 9781479918010 (ISBN) Bahrami, H ; Hajsadeghi, K ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Security in mobile handsets of telecommunication standards such as GSM, Project 25 and TETRA is very important, especially when governments and military forces use handsets and telecommunication devices. Although telecommunication could be quite secure by using encryption, coding, tunneling and exclusive channel, attackers create new ways to bypass them without the knowledge of the legitimate user. In this paper we introduce a new, simple and economical circuit to warn the user in cases where the message is not encrypted because of manipulation by attackers or accidental damage. This circuit not only consumes very low power but also is created to sustain telecommunication devices in aspect... 

    Rigid body attitude control with delayed attitude measurement

    , Article IEEE Transactions on Control Systems Technology ; Volume 23, Issue 5 , February , 2015 , Pages 1961-1969 ; 10636536 (ISSN) Bahrami, S ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Time delay in the evaluation of the attitude of a rigid body can significantly hinder the performance of the attitude control system. In this brief, we propose a dynamically smooth control law that guarantees asymptotic convergence of the rigid body attitude and angular velocity to their desired values in the presence of delayed attitude measurement. We assume that the moment-of-inertia matrix of the body is unknown. The control law includes a matrix gain that is computed by solving a delay-dependent and time-varying matrix differential equation. It is shown that the solvability of the matrix differential equation depends on a uniform controllability condition, which can be verified a priori... 

    Motion tracking in robotic manipulators in presence of delay in measurements

    , Article Proceedings - IEEE International Conference on Robotics and Automation, 3 May 2010 through 7 May 2010, Anchorage, AK ; 2010 , Pages 3884-3889 ; 10504729 (ISSN) ; 9781424450381 (ISBN) Bahrami, S ; Namvar, M ; Sharif University of Technology
    2010
    Abstract
    Time-delay in sensor measurements can be a frequent cause of instability and performance degradation in a robotic system. In this paper, motion tracking of rigid manipulators in presence of constant and known delay in sensors is investigated. By using non-minimal model of a manipulator, a dynamically smooth controller based on the Linear Matrix Inequality (LMI) approach is proposed which guarantees asymptotic tracking of desired joint angles and velocities in presence of delayed measurements. For a given controller the maximum amount of delay that preserves system stability is computed by solving an LMI optimization and also by numerical simulations, and the results are compared. Finally, a... 

    From demand response in smart grid toward integrated demand response in smart energy hub

    , Article IEEE Transactions on Smart Grid ; Volume 7, Issue 2 , 2016 , Pages 650-658 ; 19493053 (ISSN) Bahrami, S ; Sheikhi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    The proliferation of technologies such as combine heat and power systems has accelerated the integration of energy resources in energy hubs. Besides, the advances in smart grid technologies motivate the electricity utility companies toward developing demand response (DR) programs to influence the electricity usage behavior of the customers. In this paper, we modify the conventional DR programs in smart grid to develop an integrated DR (IDR) program for multiple energy carriers fed into an energy hub in smart grid, namely a smart energy (S. E.) hub. In our model, the IDR program is formulated for the electricity and natural gas networks. The interaction among the S. E. hubs is modeled as an... 

    SN transport method for neutronic noise calculation in nuclear reactor systems: comparative study between transport theory and diffusion theory

    , Article Annals of Nuclear Energy ; Volume 114 , 2018 , Pages 236-244 ; 03064549 (ISSN) Bahrami, M ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    In this paper, the neutron noise based on transport theory and diffusion noise theory using Green's function technique is calculated. As the neutron noise is used for core diagnostic, surveillance and monitoring, calculation of neutron noise precisely can play an important role in monitoring and safety. We compare the accuracy of Green's function based on transport and diffusion theory in order to survey the differences between these theories. In this study some deviation between results obtained two theories are observed, and the impact of dimensions, cross sections and frequency on the results investigated. © 2017  

    Circuit design to improve security of telecommunication devices

    , Article 2017 IEEE 7th Annual Computing and Communication Workshop and Conference, CCWC 2017, 9 January 2017 through 11 January 2017 ; 2017 ; ISBN: 978-150904228-9 Bahrami, H ; Hajsadeghi, K ; Sharif University of Technology
    2017
    Abstract
    Security in mobile handsets of telecommunication standards such as GSM, Project 25 and TETRA is very important, especially when governments and military forces use handsets and telecommunication devices. Although telecommunication could be quite secure by using encryption, coding, tunneling and exclusive channel, attackers create new ways to bypass them without the knowledge of the legitimate user. In this paper we introduce a new, simple and economical circuit to warn the user in cases where the message is not encrypted because of manipulation by attackers or accidental damage. This circuit not only consumes very low power but also is created to sustain telecommunication devices in aspect... 

    A novel organic–inorganic hybrid tandem solar cell with inverted structure

    , Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 4 , 2017 ; 09478396 (ISSN) Bahrami, A ; Faez, R ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    A novel organic–inorganic hybrid tandem solar cell with inverted structure is proposed. This efficient double-junction hybrid tandem solar cell consists of a single-junction hydrogenated amorphous silicon (a-Si:H) subcell with n-i-p structure as front cell and a P3HT:PCBM organic subcell with inverted structure as back cell. In order to optimize the hybrid tandem cell, we have performed a simulation based on transfer matrix method. We have compared the characteristics of this novel structure with a conventional structure. As a result, a power conversion efficiency (PCE) of 6.1 and 24% improvement compared to the conventional hybrid tandem cell was achieved. We also discuss the high potential... 

    Global attitude estimation using single delayed vector measurement and biased gyro

    , Article Automatica ; Volume 75 , 2017 , Pages 88-95 ; 00051098 (ISSN) Bahrami, S ; Namvar, M ; Sharif University of Technology
    2017
    Abstract
    Time delay in attitude determination systems is unavoidable and it is usually caused by low-quality data sampling, poor sensor synchronization, momentary sensor outage or operational restrictions of sensors. Despite its performance-degrading effect, time delay has been widely neglected in the existing attitude estimation methods. This paper presents a general framework for design of attitude estimators with and without SO(3) manifold restriction by assuming that measurement of a single vector measurement is available with time delay. Also, measurement of rigid-body angular velocity is considered available with an unknown bias. The proposed estimator guarantees global and asymptotic...